The Influence of Sn Orientation on the Electromigration of Idealized Lead-free Interconnects

NASA Astrophysics Data System (ADS)

Linares, Xioranny

As conventional lead solders are being replaced by Pb-free solders in electronic devices, the reliability of solder joints in integrated circuits (ICs) has become a high concern. Due to the miniaturization of ICs and consequently solder joints, the current density through the solder interconnects has increased causing electrical damage known as electromigration. Electromigration, atomic and mass migration due to high electron currents, is one of the most urgent reliability issues delaying the implementation of Pb-free solder materials in electronic devices. The research on Pb-free solders has mainly focused on the qualitative understanding of failure by electromigration. There has been little progress however, on the quantitative analysis of electromigration because of the lack of available material parameters, such as the effective charge, (z*), the driving force for electromigration. The research herein uses idealized interconnects to measure the z* of electromigration of Cu in Sn-3.0Ag-0.5Cu (SAC305) alloy under different experimental conditions. Planar SAC 305 interconnects were sandwiched between two Cu pads and subject to uniaxial current. The crystallographic orientation of Sn in these samples were characterized with electron backscatter diffraction (EBSD) and wavelength dispersive spectroscopy (WDS) before and after electromigration testing. Results indicate that samples with the c-axis aligned perpendicular to current flow, polycrystalline, and those with a diffusion barrier on the cathode side all inhibit the growth of intermetallic compounds (IMC). The effective charge values of Cu in SAC 305 under the different conditions tested were quantified for the first time and included in this dissertation. The following research is expected to help verify and improve the electromigration model and identify the desirable conditions to inhibit damage by electromigration in Pb-free solder joints.

Electromigration failures under bidirectional current stress

NASA Astrophysics Data System (ADS)

Tao, Jiang; Cheung, Nathan W.; Hu, Chenming

1998-01-01

Electromigration failure under DC stress has been studied for more than 30 years, and the methodologies for accelerated DC testing and design rules have been well established in the IC industry. However, the electromigration behavior and design rules under time-varying current stress are still unclear. In CMOS circuits, as many interconnects carry pulsed-DC (local VCC and VSS lines) and bidirectional AC current (clock and signal lines), it is essential to assess the reliability of metallization systems under these conditions. Failure mechanisms of different metallization systems (Al-Si, Al-Cu, Cu, TiN/Al-alloy/TiN, etc.) and different metallization structures (via, plug and interconnect) under AC current stress in a wide frequency range (from mHz to 500 MHz) has been study in this paper. Based on these experimental results, a damage healing model is developed, and electromigration design rules are proposed. It shows that in the circuit operating frequency range, the "design-rule current" is the time-average current. The pure AC component of the current only contributes to self-heating, while the average (DC component) current contributes to electromigration. To ensure longer thermal-migration lifetime under high frequency AC stress, an additional design rule is proposed to limit the temperature rise due to self-joule heating.

Texture-enhanced Al-Cu electrodes on ultrathin Ti buffer layers for high-power durable 2.6 GHz SAW filters

NASA Astrophysics Data System (ADS)

Fu, Sulei; Wang, Weibiao; Xiao, Li; Lu, Zengtian; Li, Qi; Song, Cheng; Zeng, Fei; Pan, Feng

2018-04-01

Achieving high resistance to acoustomigration and electromigration in the electrodes used in high-power and high-frequency surface acoustic wave (SAW) filters is important to mobile communications development. In this study, the effects of the Ti buffer layers on the textures and acoustomigration and electromigration resistances of the Al-Cu electrodes were studied comprehensively. The results demonstrate that both power durability and electromigration lifetime are positively correlated with the Al-Cu electrode texture quality. Ultrathin (˜2 nm) Ti can lead to the strongest Al-Cu (111) textured electrodes, with a full width at half maximum of the rocking curve of 2.09°. This represents a remarkable enhancement of the power durability of high-frequency 2.6 GHz SAW filters from 29 dBm to 35 dBm. It also produces lifetime almost 7 times longer than those of electrodes without Ti buffer layers in electromigration tests. X-ray diffraction and transmission electron microscopy analyses revealed that these improved acoustomigration and electromigration resistances can be attributed primarily to the reductions in overall and large-angle grain boundaries in the highly Al-Cu (111) textured electrodes. Furthermore, the growth mechanism of highly Al-Cu texture films is discussed in terms of surface-interface energy balance.

Separation of the Isotopes of Calcium by Countercurrent Electromigration in Fused Salts. Final Report; SEPARATION DES ISOTOPES DU CALCIUM PAR ELECTROMIGRATION A CONTRE COURANT EN SELS FONDUS

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

Menes, F.; Dirian, G.

1962-12-14

The results obtained up to June 25, 1962, on the separation of Ca isotopes by electromigration in fused salts have been reported in seven progress reports. The data given in these reports are summarized. Later study investigated the improvement of the diaphragm performance using nonclassical methods, preparation of an experiment confirming the performances of the high capacity U tube'' apparatus, and preparation of an installation designed for perfecting the dropping tube'' device. Only preliminary results on these studes are available. (J.S.R.)

Effect of electromigration-induced back stress gradient on nanoindentation marker movement in SnAgCu solder joints

NASA Astrophysics Data System (ADS)

Xu, Luhua; Pang, John H. L.; Tu, K. N.

2006-11-01

The electromigration-induced back stress in Pb-free SnAgCu solder was studied by an area array of nanoindentation markers on the cross section of a solder joint. The marker movements driven by combined electron wind force and electromigration-induced back stress gradient were measured at different locations. The back stress gradient was determined from the observation of marker motion using the proposed model. With the applied current density of 104A/cm2 at 125°C, the stress gradient near the anode is 97kPa/μm.

Electromigration-induced plastic deformation in passivated metal lines

NASA Astrophysics Data System (ADS)

Valek, B. C.; Bravman, J. C.; Tamura, N.; MacDowell, A. A.; Celestre, R. S.; Padmore, H. A.; Spolenak, R.; Brown, W. L.; Batterman, B. W.; Patel, J. R.

2002-11-01

We have used scanning white beam x-ray microdiffraction to study microstructural evolution during an in situ electromigration experiment on a passivated Al(Cu) test line. The data show plastic deformation and grain rotations occurring under the influence of electromigration, seen as broadening, movement, and splitting of reflections diffracted from individual metal grains. We believe this deformation is due to localized shear stresses that arise due to the inhomogeneous transfer of metal along the line. Deviatoric stress measurements show changes in the components of stress within the line, including relaxation of stress when current is removed.

Electromigration induced high fraction of compound formation in SnAgCu flip chip solder joints with copper column

NASA Astrophysics Data System (ADS)

Xu, Luhua; Han, Jung-Kyu; Liang, Jarrett Jun; Tu, K. N.; Lai, Yi-Shao

2008-06-01

To overcome the effect of current crowding on electromigration-induced pancake-type void formation in flip chip solder joints, two types of Cu column in 90μm flip chip SnAgCu solder joints have been studied. They were (1) the solder contacts the Cu column at bottom and side walls and (2) the solder wets only the bottom surface of the copper column. With a current density of 1.6×104A/cm2 at 135°C, no failure was detected after 1290h. However, the resistance increased by about 10% due to the formation of a large fraction of intermetallic compounds. We found that electromigration has accelerated the consumption rate of copper column and converted almost the entire solder joint into intermetallic compound. Mechanically, drop impact test indicates a brittle fracture failure in the intermetallic. The electromigration critical product for the intermetallic is discussed.

Electro-migration of heavy metals in an aged electroplating contaminated soil affected by the coexisting hexavalent chromium.

PubMed

Zhang, Weihua; Zhuang, Luwen; Tong, Lizhi; Lo, Irene M C; Qiu, Rongliang

2012-02-01

Cr(VI) was often reported to oxidize soil organic matter at acidic environments due to its high ORP, probably thus changing cationic metal species bound to soil organic matter, and influencing their electro-migration patterns. However, such an effect on the electro-migration was not confirmed in most previous studies. Therefore, this study applied a fixed voltage direct current field on an aged electroplating contaminated clayed soil, with a special interest in the direct or indirect influence of Cr(VI) on the electro-migration of other coexisting metals. After 353 h electrokinetic process, 81% of Zn, 53% of Ni and 22% of Cu in the original soil were electro-migrated into the electrolyte, and most of the remaining concentrated near the cathode. The Cr(VI) oxidized some soil organic matter along its migration pathway, with a pronounced reaction occurred near the anode at low pHs. The resulting Cr(III) reversed its original movement, and migrated towards the cathode, leading to the occurrence of a second Cr concentration peak in the soil. Metal species analyses showed that the amount of metals bound to soil organic matter significantly decreased, while a substantial increase in the Cr species bound to Fe/Mn (hydro-)oxides was observed, suggesting an enhancement of cationic metal electro-migration by the reduction of Cr(VI) into Cr(III). However, the Cr(VI) may form some stable lead chromate precipitates, and in turn demobilize Pb in the soil, as the results showed a low Pb removal and an increase in its acid-extractable and residual fractions after electrokinetic remediation. Copyright © 2011 Elsevier Ltd. All rights reserved.

An in situ investigation of electromigration in Cu nanowires.

PubMed

Huang, Qiaojian; Lilley, Carmen M; Divan, Ralu

2009-02-18

Electromigration in copper (Cu) nanowires deposited by electron beam evaporation has been investigated using both resistance measurement and the in situ scanning electron microscopy technique. During electromigration, voids formed at the cathode end while hillocks (or extrusions) grew close to the anode end. The failure lifetimes were measured for various applied current densities and the mean temperature in the wire was estimated. Electromigration activation energies of 1.06 eV and 0.94 eV were found for the wire widths of 90 nm and 141 nm, respectively. These results suggest that the mass transport of Cu during electromigration mainly occurs along the wire surfaces. Further investigations of the Auger electron spectrum show that both Cu atoms and the surface contaminants of carbon and oxygen migrate from cathode to anode under the electrical stressing.

Photovoltaic switching mechanism in lateral structure hybrid perovskite solar cells

DOE PAGES

Yuan, Yongbo; Chae, Jungseok; Shao, Yuchuan; ...

2015-06-05

In this study, long range electromigration of methylammonium ions (MA +) in methyl ammonium lead tri-iodide (MAPbI 3) film is observed directly using the photo­thermal induced resonance technique. The electromigration of MA + leads to the formation of a lateral p-i-n structure, which is the origin of the switchable photovoltaic effect in MAPbI 3 perovskite devices.

Electromigration Reliability of Advanced Interconnects

NASA Astrophysics Data System (ADS)

Hu, C.-K.; Gignac, L. M.; Baker-O'Neal, B.; Liniger, E.; Yu, R.; Flaitz, P.; Stamper, A. K.

2007-10-01

Electromigration behavior in Cu damascene wires was studied for various metal line widths, thicknesses and grain sizes where the grain size was modulated by Cu linewidth and thickness, and by adjusting the wafer annealing process step after Cu electroplating and before Cu chemical mechanical polishing. Significantly different results were found between 0.2 μm and 65 nm CMOS node technologies. A larger variation of Cu grain size between the samples was achieved on 65 nm node which was due to the finer line width and thinner metal thickness. The Cu lifetime and mass flow in samples with bamboo, near bamboo, bamboo-polycrystalline mixture, and polycrystalline grain structures were measured. These factors allow one to accurately resolve the relative contribution between grain boundary and interface diffusions in the Cu nanowires. The electromigration mass flow estimated from the lifetime on the test line on a W via and physically stable liner was found to be linearly proportional to current density. The effects of Cu(Ti) alloy seeds and Cu surface pre-clean techniques before the dielectric cap depositions on Cu electromigration were also observed. A significantly improved Cu lifetime, at the expense of the Cu conductivity, was found. The electromigration activation energies for Cu in Cu(Ti) alloy, along Cu/amorphous a-SiCxNyHz interface and in Cu grain boundaries were found to be 1.3, 0.95 and 0.79+0.05 eV, respectively.

White beam analysis of coupling between precipitation and plasticdeformation during electromigration in a passivated Al(0.5wt. percent Cu)interconnect

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

Barabash, R.I.; Ice, G.E.; Tamura, N.

2005-09-01

The scaling of device dimensions with a simultaneous increase in functional density imposes a challenge to materials technology and reliability of interconnects. White beam X-ray microdiffraction is particularly well suited for the in situ study of electromigration. M.A. Krivoglaz theory was applied for the interpretation of white beam diffraction. The technique was used to probe microstructure in interconnects and has recently been able to monitor the onset of plastic deformation induced by mass transport during electromigration in Al(Cu) lines even before any macroscopic damage became visible. In the present paper, we demonstrate that the evolution of the dislocation structure duringmore » electromigration is highly inhomogeneous and results in the formation of unpaired randomly distributed geometrically necessary dislocations as well as geometrically necessary dislocation boundaries. When almost all unpaired dislocations and dislocation walls with the density n+ are parallel (as in the case of Al-based interconnects), the anisotropy in the scattering properties of the material becomes important, and the electrical properties of the interconnect depend strongly on the direction of the electric current relative to the orientation of the dislocation network. A coupling between the dissolution, growth and reprecipitation of Al2Cu precipitates and the electromigration-induced plastic deformation of grains in interconnects is observed.« less

Purification of CdZnTe by electromigration

NASA Astrophysics Data System (ADS)

Kim, K.; Kim, Sangsu; Hong, Jinki; Lee, Jinseo; Hong, Taekwon; Bolotnikov, A. E.; Camarda, G. S.; James, R. B.

2015-04-01

Electro-migration of ionized/electrically active impurities in CdZnTe (CZT) was successfully demonstrated at elevated temperature with an electric field of 20 V/mm. Copper, which exists in positively charged states, electro-migrated at a speed of 15 μm/h in an electric field of 20 V/mm. A notable variation in impurity concentration along the growth direction with the segregation tendency of the impurities was observed in an electro-migrated CZT boule. Notably, both Ga and Fe, which exist in positively charged states, exhibited the opposite distribution to that of their segregation tendency in Cd(Zn)Te. A CZT detector fabricated from the middle portion of the electro-migrated CZT boule showed an improved mobility-lifetime product of 0.91 × 10-2 cm2/V, compared with that of 1.4 × 10-3 cm2/V, observed in an as-grown (non-electro-migrated) CZT detector. The optimum radiation detector material would have minimum concentration of deep traps required for compensation.

Purification of CdZnTe by Electromigration

DOE PAGES

Kim, K.; Kim, Sangsu; Hong, Jinki; ...

2015-04-14

Electro-migration of ionized/electrically active impurities in CdZnTe (CZT) was successfully demonstrated at elevated temperature with an electric field of 20 V/mm. Copper, which exists in positively charged states, electro-migrated at a speed of 15 lm/h in an electric field of 20 V/mm. A notable variation in impurity concentration along the growth direction with the segregation tendency of the impurities was observed in an electro-migrated CZT boule. Notably, both Ga and Fe, which exist in positively charged states, exhibited the opposite distribution to that of their segregation tendency in Cd(Zn)Te. Furthermore, a CZT detector fabricated from the middle portion of themore » electromigrated CZT boule showed an improved mobility-lifetime product of 0.91 10 -2 cm 2 /V, compared to that of 1.4 10 -3 cm 2 /V, observed in an as-grown (non-electro-migrated) CZT detector. The optimum radiation detector material would have minimum concentration of deep traps required for compensation.« less

Line length dependence of threshold current density and driving force in eutectic SnPb and SnAgCu solder electromigration

NASA Astrophysics Data System (ADS)

Yoon, Min-Seung; Ko, Min-Ku; Kim, Bit-Na; Kim, Byung-Joon; Park, Yong-Bae; Joo, Young-Chang

2008-04-01

The relationship between the threshold current density and the critical line length in eutectic SnPb and SnAgCu electromigrations were examined using solder lines with the various lengths ranging from 100to1000μm. When the electron wind-force was balanced by the back-stress gradient force, the net flux of electromigration is zero, at which the current density and line length are defined as the threshold current density and the critical length, respectively. It was found that in SnAgCu electromigration, the 1/L dependence on the threshold current density showed good agreement, whereas the threshold current densities of the eutectic SnPb deviated from the 1/L dependence. The balance between the electron wind-force and the back-stress gradient force was the main factor determining the threshold product of SnAgCu electromigration. On the other hand, in the case of eutectic SnPb, the chemical driving force is contributed as a back-flux force in addition to the back-stress gradient force. The existence of the chemical driving force was caused by the nonequilibrium Pb concentration inside the Pb-rich phases between the cathode and anode during the electromigration procedure.

The failure models of Sn-based solder joints under coupling effects of electromigration and thermal cycling

NASA Astrophysics Data System (ADS)

Ma, Limin; Zuo, Yong; Liu, Sihan; Guo, Fu; Wang, Xitao

2013-01-01

Currently, the main concerns of Pb-free solder joints are focusing on electromigration (EM) and thermomechanical fatigue (TMF) problems. Many models have been established to understand the failure mechanisms of the joint under such single test conditions. Based on the fact that almost all microelectronic devices serve in combination conditions of fluctuated temperature and electric current stressing, the coupling effects of EM and TMF on evolution of microstructure and resistance of solder joint had been investigated. The failure models of binary SnBi alloy and ternary SnAgCu (SAC) solder under the coupling stressing were divided into four and three different stages, respectively. The failure mechanisms were dominant by the relationship of phase segregation, polarity effect, phase coarsening, and the coefficient of thermal expansion mismatch. Cracks tend to form and propagate along the interface between intermetallic compound layers and solder matrix in SAC solder. However, grain boundary was considered as the nucleation sites for microcracks in SnBi solder. High current density alleviates the deterioration of solder at the beginning stage of coupling stressing through Joule heating effect. An abrupt jump of resistance could be observed before the failure of the joint. The failure molds were determined by interactions of EM behaviors and TMF damages.

Electro-migration of impurities in TlBr

NASA Astrophysics Data System (ADS)

Kim, Ki Hyun; Kim, Eunlim; Kim, H.; Tappero, R.; Bolotnikov, A. E.; Camarda, G. S.; Hossain, A.; Cirignano, L.; James, R. B.

2013-10-01

We observed the electro-migration of Cu, Ag, and Au impurities that exist in positive-ion states in TlBr detectors under electric field strengths typically used for device operation. The migration occurred predominantly through bulk- and specific-channels, which are presumed to be a network of grain and sub-grain boundaries. The electro-migration velocity of Cu, Ag, and Au in TlBr is about 4-8 × 10-8 cm/s at room temperature under an electric field of 500-800 V/mm. The instability and polarization effects of TlBr detectors might well be correlated with the electro-migration of residual impurities in TlBr, which alters the internal electric field over time. The effect may also have been due to migration of the electrode material itself, which would allow for the possibility of a better choice for contact material and for depositing an effective diffusion barrier. From our findings, we suggest that applying our electro-migration technique for purifying material is a promising new way to remove electrically active metallic impurities in TlBr crystals, as well as other materials.

Separation of Calcium Isotopes by Counter-Current Electro-Migration in Molten Salts; SEPARATION DES ISOTOPES DU CALCIUM PAR ELECTRO-MIGRATION A CONTRECOURANT EN SELS FONDUS

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

Menes, F.; Dirian, G.; Roth, E.

1962-01-01

The method of counter-current electromigration in molten salts was applied to CaBr/sub 2/ with an alkali metal bromide added to the cathode compartment. Enrichments on Ca/sup 46/ greater than a factor of two were obtained at the anode. The mass effect was found to be about 0.06. An estimation of the cost of energy for a process based on this method was made. (auth)

AB INITIO calculation of the electromigration wind valence of interstitial hydrogen in f.c.c metals

NASA Astrophysics Data System (ADS)

van Ek, J.; Lodder, A.

1990-02-01

Calculated electromigration wind valences, obtained within a KKR-Green function description, are presented. It is shown that the electromigration wind valence of hydrogen along different migration paths in Cu, Ag and Pd can be calculated including charge transfer effects in the impurity cluster. A nice procedure for retrieving the scalar character of the wind valence in an f.c.c metal introduces an explanation for the isotope effect in the wind valence.

Quantifying Electromigration Processes in Sn-0.7Cu Solder with Lab-Scale X-Ray Computed Micro-Tomography

NASA Astrophysics Data System (ADS)

Mertens, James Charles Edwin

For decades, microelectronics manufacturing has been concerned with failures related to electromigration phenomena in conductors experiencing high current densities. The influence of interconnect microstructure on device failures related to electromigration in BGA and flip chip solder interconnects has become a significant interest with reduced individual solder interconnect volumes. A survey indicates that x-ray computed micro-tomography (muXCT) is an emerging, novel means for characterizing the microstructures' role in governing electromigration failures. This work details the design and construction of a lab-scale muXCT system to characterize electromigration in the Sn-0.7Cu lead-free solder system by leveraging in situ imaging. In order to enhance the attenuation contrast observed in multi-phase material systems, a modeling approach has been developed to predict settings for the controllable imaging parameters which yield relatively high detection rates over the range of x-ray energies for which maximum attenuation contrast is expected in the polychromatic x-ray imaging system. In order to develop this predictive tool, a model has been constructed for the Bremsstrahlung spectrum of an x-ray tube, and calculations for the detector's efficiency over the relevant range of x-ray energies have been made, and the product of emitted and detected spectra has been used to calculate the effective x-ray imaging spectrum. An approach has also been established for filtering 'zinger' noise in x-ray radiographs, which has proven problematic at high x-ray energies used for solder imaging. The performance of this filter has been compared with a known existing method and the results indicate a significant increase in the accuracy of zinger filtered radiographs. The obtained results indicate the conception of a powerful means for the study of failure causing processes in solder systems used as interconnects in microelectronic packaging devices. These results include the volumetric quantification of parameters which are indicative of both electromigration tolerance of solders and the dominant mechanisms for atomic migration in response to current stressing. This work is aimed to further the community's understanding of failure-causing electromigration processes in industrially relevant material systems for microelectronic interconnect applications and to advance the capability of available characterization techniques for their interrogation.

Effect Of Impurity On Cu Electromigration

NASA Astrophysics Data System (ADS)

Hu, C.-K.; Angyal, M.; Baker, B. C.; Bonilla, G.; Cabral, C.; Canaperi, D. F.; Choi, S.; Clevenger, L.; Edelstein, D.; Gignac, L.; Huang, E.; Kelly, J.; Kim, B. Y.; Kyei-Fordjour, V.; Manikonda, S. L.; Maniscalco, J.; Mittal, S.; Nogami, T.; Parks, C.; Rosenberg, R.; Simon, A.; Xu, Y.; Vo, T. A.; Witt, C.

2010-11-01

The impact of the existence of Cu grain boundaries on the degradation of Cu interconnect lifetime at the 45 nm technology node and beyond has suggested that improved electromigra-tion in Cu grain boundaries has become increasingly important. In this paper, solute effects of non-metallic (C, Cl, O and S) and metallic (Al, Co, In, Mg, Sn, and Ti) impurities on Cu elec-tromigration were investigated. The Cu alloy interconnects were fabricated by adjusting Cu electroplating solutions or by depositing a Cu alloy seed, a thin film layer of impurity, an alloy liner, or a metal cap. A large variation of Cu grain structure in the samples was achieved by adjusting the wafer fabrication process steps. The non-metallic impurities were found to be less than 0.1% in the electroplated Cu with no effect on Cu electromigration lifetimes. Most of the metallic impurities reduced Cu interface and grain boundary mass flows and enhanced Cu lifetime, but Al, Co, and Mg impurities did not mitigate Cu grain boundary diffusion.

Microstructure control of Al-Cu films for improved electromigration resistance

DOEpatents

Frear, D.R.; Michael, J.R.; Romig, A.D. Jr.

1994-04-05

A process for the forming of Al-Cu conductive thin films with reduced electromigration failures is useful, for example, in the metallization of integrated circuits. An improved formation process includes the heat treatment or annealing of the thin film conductor at a temperature within the range of from 200 C to 300 C for a time period between 10 minutes and 24 hours under a reducing atmosphere such as 15% H[sub 2] in N[sub 2] by volume. Al-Cu thin films annealed in the single phase region of a phase diagram, to temperatures between 200 C and 300 C have [theta]-phase Al[sub 2] Cu precipitates at the grain boundaries continuously become enriched in copper, due, it is theorized, to the formation of a thin coating of [theta]-phase precipitate at the grain boundary. Electromigration behavior of the aluminum is, thus, improved because the [theta]-phase precipitates with copper hinder aluminum diffusion along the grain boundaries. Electromigration, then, occurs mainly within the aluminum grains, a much slower process. 5 figures.

Electromigration kinetics and critical current of Pb-free interconnects

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

Lu, Minhua; Rosenberg, Robert

2014-04-07

Electromigration kinetics of Pb-free solder bump interconnects have been studied using a single bump parameter sweep technique. By removing bump to bump variations in structure, texture, and composition, the single bump sweep technique has provided both activation energy and power exponents that reflect atomic migration and interface reactions with fewer samples, shorter stress time, and better statistics than standard failure testing procedures. Contact metallurgies based on Cu and Ni have been studied. Critical current, which corresponds to the Blech limit, was found to exist in the Ni metallurgy, but not in the Cu metallurgy. A temperature dependence of critical currentmore » was also observed.« less

Electromigrative separation techniques in forensic science: combining selectivity, sensitivity, and robustness.

PubMed

Posch, Tjorben Nils; Pütz, Michael; Martin, Nathalie; Huhn, Carolin

2015-01-01

In this review we introduce the advantages and limitations of electromigrative separation techniques in forensic toxicology. We thus present a summary of illustrative studies and our own experience in the field together with established methods from the German Federal Criminal Police Office rather than a complete survey. We focus on the analytical aspects of analytes' physicochemical characteristics (e.g. polarity, stereoisomers) and analytical challenges including matrix tolerance, separation from compounds present in large excess, sample volumes, and orthogonality. For these aspects we want to reveal the specific advantages over more traditional methods. Both detailed studies and profiling and screening studies are taken into account. Care was taken to nearly exclusively document well-validated methods outstanding for the analytical challenge discussed. Special attention was paid to aspects exclusive to electromigrative separation techniques, including the use of the mobility axis, the potential for on-site instrumentation, and the capillary format for immunoassays. The review concludes with an introductory guide to method development for different separation modes, presenting typical buffer systems as starting points for different analyte classes. The objective of this review is to provide an orientation for users in separation science considering using capillary electrophoresis in their laboratory in the future.

Mechanism of electromigration failure in Damascene processed copper interconnects

NASA Astrophysics Data System (ADS)

Michael, Nancy Lyn

2002-11-01

A major unresolved issue in Cu interconnect reliability is the interface role in the failure mechanism of real structures. The present study investigates failure in single-level damascene Cu interconnects with variations in interface condition, passivation and barrier, and linewidth. In the first phase, accelerated electromigration testing of 0.25mum Cu interconnects capped with SiN or SiCN, shows that lifetime and failure mode vary with capping layer. The first mode, seen primarily in SiN samples, is characterized by gradual resistance increase and extensive interface damage, believed to result from failure led by interface electromigration. The competing failure mode, found in SiCN capped samples, is characterized by abrupt resistance increase and localized voiding. The second phase fixes SiCN as the capping material and varies barrier material and line width. The three barrier materials, Ta, TaN, and Ta/TaN, produce similar lifetime statistics and failure is abrupt. Line width, however, does have a strong influence on failure time. The line width/grain size ratio ranged from 0.53 to 2.2 but does not correlate with mean time to failure (MTF). The strong dependence on interface fraction, combined with the conclusion from phase one that interface electromigration is not rate controlling, suggests another mechanism related to the interface is a controlling factor. The possibility that contamination and defects at the interface are key to this failure mode was investigated using electro-thermal fatigue (ETF). In ETF, where lines are simultaneously subjected to thermal cycling and constant current, damage caused by thermal stress is accelerated. Tests reveal that in 80 nm lines, transient failure occurs at times far below MTF in electromigration tests at higher temperatures. Failure found in ETF is clearly a result of damage growth due to thermal/mechanical stress rather than electromigration. At the stress levels created by the moderate ETF test conditions, the only place voids are likely to nucleate and grow is at pre-existing defects and impurities. In narrower lines, where smaller voids can cause catastrophic damage, defects have a greater effect on MTF. Results from this investigation suggest that impurities and defects in the Cu and at the interface, must be carefully controlled to make reliable narrow Cu interconnects.

Electromigration process for the purification of molten silicon during crystal growth

DOEpatents

Lovelace, Alan M. Administrator of the National Aeronautics and Space; Shlichta, Paul J.

1982-01-01

A process for the purification of molten materials during crystal growth by electromigration of impurities to localized dirty zones. The process has particular applications for silicon crystal growth according to Czochralski techniques and edge-defined film-fed growth (EFG) conditions. In the Czochralski crystal growing process, the impurities are electromigrated away from the crystallization interface by applying a direct electrical current to the molten silicon for electromigrating the charged impurities away from the crystal growth interface. In the EFG crystal growth process, a direct electrical current is applied between the two faces which are used in forming the molten silicon into a ribbon. The impurities are thereby migrated to one side only of the crystal ribbon. The impurities may be removed or left in place. If left in place, they will not adversely affect the ribbon when used in solar collectors. The migration of the impurity to one side only of the silicon ribbon is especially suitable for use with asymmetric dies which preferentially crystallize uncharged impurities along one side or face of the ribbon.

Crystallographic Orientation Effect on Electromigration in Ni-Sn Microbump

NASA Astrophysics Data System (ADS)

Huang, Yi-Ting; Chen, Chih-Hao; Chakroborty, Subhendu; Wu, Albert T.

2017-09-01

This article addresses the reliability challenges regarding electromigration in developing three-dimensional integrated circuits (3D-ICs). The line-type sandwich structure of Ni/Sn3.5Ag(15 μm)/Ni was used to simulate microbumps to examine the reliability of electromigration in 3D-IC technology. The solder strip of Ni/Sn3.5Ag(15 μm)/Ni was stressed with a current density of 1.0 × 104 A/cm2 at 150°C. The current stressing enhanced the reaction between the solder and Ni to form Ni3Sn4, which occupied the entire joint and transformed into a Ni/Ni3Sn4/Ni structure when the solder was completely consumed. Electron backscatter diffraction was used to analyze the crystallographic characteristics of Sn and Ni3Sn4 as related to the electromigration effect. The results indicated that the crystallographic orientation of Sn plays a significant role in the Ni/Sn3.5Ag/Ni, whereas the orientation of Ni3Sn4 is the dominant factor of diffusion behavior in the Ni/Ni3Sn4/Ni.

Microstructure control of Al-Cu films for improved electromigration resistance

DOEpatents

Frear, Darrel R.; Michael, Joseph R.; Romig, Jr., Alton D.

1994-01-01

A process for the forming of Al-Cu conductive thin films with reduced electromigration failures is useful, for example, in the metallization of integrated circuits. An improved formation process includes the heat treatment or annealing of the thin film conductor at a temperature within the range of from 200.degree. C. to 300.degree. C. for a time period between 10 minutes and 24 hours under a reducing atmosphere such as 15% H.sub.2 in N.sub.2 by volume. Al-Cu thin films annealed in the single phase region of a phase diagram, to temperatures between 200.degree. C. and 300.degree. C. have .theta.-phase Al.sub.2 Cu precipitates at the grain boundaries continuously become enriched in copper, due, it is theorized, to the formation of a thin coating of .theta.-phase precipitate at the grain boundary. Electromigration behavior of the aluminum is, thus, improved because the .theta.-phase precipitates with copper hinder aluminum diffusion along the grain boundaries. Electromigration, then, occurs mainly within the aluminum grains, a much slower process.

Liquid-phase electroepitaxy - Dopant segregation

NASA Technical Reports Server (NTRS)

Lagowski, J.; Jastrzebski, L.; Gatos, H. C.

1980-01-01

A theoretical model is presented which accounts for the dopant segregation in liquid-phase electroepitaxy in terms of dopant transport in the liquid phase (by electromigration and diffusion), the growth velocity, and the Peltier effect at the substrate-solution interface. The contribution of dopant electromigration to the magnitude of the effective segregation coefficient is dominant in the absence of convection; the contribution of the Peltier effect becomes significant only in the presence of pronounced convection. Quantitative expressions which relate the segregation coefficient to the growth parameters also permit the determination of the diffusion constant and electromigration mobility of the dopant in the liquid phase. The model was found to be in good agreement with the measured segregation characteristics of Sn in the electroepitaxial growth of GaAs from Ga-As solutions. For Sn in Ga-As solution at 900 C the diffusion constant was found to be 4 x 10 to the -5 sq cm/s and the electromigration velocity (toward the substrate with a positive polarity 2 x 10 to the -5 cm/s current density of 10 A/sq cm.

Separation of Isotopes by Electromigration in Fused Salts; SEPARATION DES ISOTOPES PAR ELECTROMIGRATION EN SELS FONDUS (in French)

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

Menes, F.

1961-12-01

A process is given for the separation of isotopes by reflux electromigration of fused salts. The process is carried out in a countercurrent manner on a fused mixture of a salt containing the isotopic cations with a salt having the same anion and a cation with a mobility as near as possible to that of the isotopic cations. An electrolytic cell for carrying out the process is described. Examples are presented of the process in which lithium-6 and lithium-7 are separated in a LiBr-KBr mixture, and calcium isotopes are separated in CaBr/sub 2/-KBr and CaBr/sub 2/- LiBr systems. (N.W.R.)

Applications of Electromigration Techniques: Applications of Electromigration Techniques in Food Analysis

NASA Astrophysics Data System (ADS)

Wieczorek, Piotr; Ligor, Magdalena; Buszewski, Bogusław

Electromigration techniques, including capillary electrophoresis (CE), are widely used for separation and identification of compounds present in food products. These techniques may also be considered as alternate and complementary with respect to commonly used analytical techniques, such as high-performance liquid chromatography (HPLC), or gas chromatography (GC). Applications of CE concern the determination of high-molecular compounds, like polyphenols, including flavonoids, pigments, vitamins, food additives (preservatives, antioxidants, sweeteners, artificial pigments) are presented. Also, the method developed for the determination of proteins and peptides composed of amino acids, which are basic components of food products, are studied. Other substances such as carbohydrates, nucleic acids, biogenic amines, natural toxins, and other contaminations including pesticides and antibiotics are discussed. The possibility of CE application in food control laboratories, where analysis of the composition of food and food products are conducted, is of great importance. CE technique may be used during the control of technological processes in the food industry and for the identification of numerous compounds present in food. Due to the numerous advantages of the CE technique it is successfully used in routine food analysis.

Investigation of electromigration behavior in lead-free flip chip solder bumps

NASA Astrophysics Data System (ADS)

Kalkundri, Kaustubh Jayant

Packaging technology has also evolved over time in an effort to keep pace with the demanding requirements. Wirebond and flip chip packaging technologies have become extremely versatile and ubiquitous in catering to myriad applications due to their inherent potential. This research is restricted strictly to flip chip technology. This technology incorporates a process in which the bare chip is turned upside down, i.e., active face down, and is bonded through the I/O to the substrate, hence called flip chip. A solder interconnect that provides electrical connection between the chip and substrate is bumped on a processed silicon wafer prior to dicing for die-attach. The assembly is then reflow-soldered followed by the underfill process to provide the required encapsulation. The demand for smaller and lighter products has increased the number of I/Os without increasing the package sizes, thereby drastically reducing the size of the flip chip solder bumps and their pitch. Reliability assessment and verification of these devices has gained tremendous importance due to their shrinking size. To add to the complexity, changing material sets that are results of recently enacted lead-free solder legislations have raised some compatibility issues that are already being researched. In addition to materials and process related flip chip challenges such as solder-flux compatibility, Coefficient of Thermal Expansion (CTE) mismatch, underfill-flux compatibility and thermal management, flip chip packages are vulnerable to a comparatively newer challenge, namely electromigration observed in solder bumps. It is interesting to note that electromigration has come to the forefront of challenges only recently. It has been exacerbated by the reduction in bump cross-section due to the seemingly continuous shrinking in package size over time. The focus of this research was to understand the overall electromigration behavior in lead-free (SnAg) flip chip solder bumps. The objectives of the research were to comprehend the physics of failure mechanism in electromigration for lead-free solder bumps assembled in a flip chip ceramic package having thick copper under bump metallization and to estimate the unknown critical material parameters from Black's equation that describe failure due to electromigration. In addition, the intent was to verify the 'use condition reliability' by extrapolation from experimental conditions. The methodology adopted for this research was comprised of accelerated electromigration tests on SnAg flip chip solder bumps assembled on ceramic substrate with a thick copper under bump metallization. The experimental approach was comprised of elaborate measurement of the temperature of each sample by separate metallization resistance exhibiting positive resistance characteristics to overcome the variation in Joule heating. After conducting the constant current experiments and analyzing the failed samples, it was found that the primary electromigration failure mode observed was the dissolution of the thick copper under bump metallization in the solder, leading to a change in resistance. The lifetime data obtained from different experiments was solved simultaneously using a multiple regression approach to yield the unknown Black's equation parameters of current density exponent and activation energy. In addition to the implementation of a systematic failure analysis and data analysis procedure, it was also deduced that thermomigration due to the temperature gradient across the chip does impact the overall electromigration behavior. This research and the obtained results were significant in bridging the gap for an overall understanding of this critical failure mode observed in flip chip solder bumps. The measurement of each individual sample temperature instead of an average temperature enabled an accurate analysis for predicting the 'use condition reliability' of a comparable product. The obtained results and the conclusions can be used as potential inputs in future designs and newer generations of flip chip devices that might undergo aggressive scaling. This will enable these devices to retain their functionality during their intended useful life with minimal threat of failure due to the potent issue of electromigration. (Abstract shortened by UMI.)

Thermoreflectance imaging of electromigration evolution in asymmetric aluminum constrictions

NASA Astrophysics Data System (ADS)

Tian, Hao; Ahn, Woojin; Maize, Kerry; Si, Mengwei; Ye, Peide; Alam, Muhammad Ashraful; Shakouri, Ali; Bermel, Peter

2018-01-01

Electromigration (EM) is a phenomenon whereby the flow of current in metal wires moves the underlying atoms, potentially inducing electronic interconnect failures. The continued decrease in commercial lithographically defined feature sizes means that EM presents an increasing risk to the reliability of modern electronics. To mitigate these risks, it is important to look for novel mechanisms to extend lifetime without forfeiting miniaturization. Typically, only the overall increase in the interconnect resistance and failure voltage are characterized. However, if the current flows non-uniformly, spatially resolving the resulting hot spots during electromigration aging experiments may provide better insights into the fundamental mechanisms of this process. In this study, we focus on aluminum interconnects containing asymmetric reservoir and void pairs with contact pads on each end. Such reservoirs are potential candidates for self-healing. Thermoreflectance imaging was used to detect hot spots in electrical interconnects at risk of failure as the voltage was gradually increased. It reveals differential heating with increasing voltage for each polarity. We find that while current flow going from a constriction to a reservoir causes a break at the void, the identical structure with the opposite polarity can sustain higher current (J = 21 × 106 A/cm2) and more localized joule heating and yet is more stable. Ultimately, a break takes place at the contact pad where the current flows from narrow interconnect to larger pads. In summary, thermoreflectance imaging with submicron spatial resolution provides valuable information about localized electromigration evolution and the potential role of reservoirs to create more robust interconnects.

Grain boundary grooving induced by the anisotropic surface drift diffusion driven by the capillary and electromigration forces: Simulations

NASA Astrophysics Data System (ADS)

Akyildiz, Oncu; Omer Ogurtani, Tarik

2011-08-01

The morphological evolution kinetics of a bicrystal thin film induced by anisotropic surface drift diffusion and driven by the applied electrostatic field is investigated via self consistent dynamical computer simulations. The physico-mathematical model, which is based upon the irreversible thermodynamic treatment of surfaces and interfaces with singularities [T. O. Ogurtani, J. Chem. Phys. 124, 144706 (2006)], provided us with auto-control on the otherwise free-motion of the triple junction at the intersection of the grooving surface and the grain boundary, without having any a priori assumption on the equilibrium dihedral angles. The destruction of the symmetry of the freshly formed grain boundary grooves under the anisotropic surface diffusion driven by the concurrent action of the capillarity and electromigration is observed. After prolonged exposure times the applied electric field above the well defined threshold level modifies Mullins' familiar stationary state time law as, t¯1/4, and causes the premature termination of the groove penetration because of the current crowding at the tips of counteracting grain boundary-grooves initiated on both sides of the test modulus. That finding indicates that the electromigration plays the same role as a healing agent [T. O. Ogurtani, J. Appl. Phys. 106, 053503 (2009)] in arresting the thermal grooving, thereby avoiding the premature interconnect failure as in the case of surface roughening and crack initiation caused by compressive stress gradients. The role of the electromigration and wetting parameter on the ridge/slit formations are thoroughly investigated in this study and the prerequisite conditions are also identified.

Feasibilty analyses of electroepitaxial research and development accommodations. Volume 2: Electroepitaxial growth of GaAs

NASA Technical Reports Server (NTRS)

1982-01-01

The technique of electromigration, i.e., electric field induced forced convection, can be used to grow semiconductor material and other compounds from solution by passing electric current through the growth interface while the temperature of the system is maintained constant. Current controlled electromigration, referred to as electroepitaxy, was successfully applied to grow epitaxial layers of various semiconductors and garnets.

Simulation of Electromigration Based on Resistor Networks

NASA Astrophysics Data System (ADS)

Patrinos, Anthony John

A two dimensional computer simulation of electromigration based on resistor networks was designed and implemented. The model utilizes a realistic grain structure generated by the Monte Carlo method and takes specific account of the local effects through which electromigration damage progresses. The dynamic evolution of the simulated thin film is governed by the local current and temperature distributions. The current distribution is calculated by superimposing a two dimensional electrical network on the lattice whose nodes correspond to the particles in the lattice and the branches to interparticle bonds. Current is assumed to flow from site to site via nearest neighbor bonds. The current distribution problem is solved by applying Kirchhoff's rules on the resulting electrical network. The calculation of the temperature distribution in the lattice proceeds by discretizing the partial differential equation for heat conduction, with appropriate material parameters chosen for the lattice and its defects. SEReNe (for Simulation of Electromigration using Resistor Networks) was tested by applying it to common situations arising in experiments with real films with satisfactory results. Specifically, the model successfully reproduces the expected grain size, line width and bamboo effects, the lognormal failure time distribution and the relationship between current density exponent and current density. It has also been modified to simulate temperature ramp experiments but with mixed, in this case, results.

Effect of current crowding on whisker growth at the anode in flip chip solder joints

NASA Astrophysics Data System (ADS)

Ouyang, Fan-Yi; Chen, Kai; Tu, K. N.; Lai, Yi-Shao

2007-12-01

Owing to the line-to-bump configuration in flip chip solder joints, current crowding occurs when electrons enter into or exit from the solder bump. At the cathode contact, where electrons enter into the bump, current crowding induced pancake-type void formation has now been observed widely. At the anode contact, where electrons exit from the bump, we report here that whisker is formed. Results of both eutectic SnPb and SnAgCu solder joints are presented and compared. The cross-sectioned surface in SnPb showed dimple and bulge after electromigration, while that of SnAgCu remained flat. The difference is due to a larger back stress in the SnAgCu, consequently, electromigration in SnAgCu is slower than that in SnPb. Nanoindentation markers were used to measure the combined atomic fluxes of back stress and electromigration.

Electromigration model for the prediction of lifetime based on the failure unit statistics in aluminum metallization

NASA Astrophysics Data System (ADS)

Park, Jong Ho; Ahn, Byung Tae

2003-01-01

A failure model for electromigration based on the "failure unit model" was presented for the prediction of lifetime in metal lines.The failure unit model, which consists of failure units in parallel and series, can predict both the median time to failure (MTTF) and the deviation in the time to failure (DTTF) in Al metal lines. The model can describe them only qualitatively. In our model, both the probability function of the failure unit in single grain segments and polygrain segments are considered instead of in polygrain segments alone. Based on our model, we calculated MTTF, DTTF, and activation energy for different median grain sizes, grain size distributions, linewidths, line lengths, current densities, and temperatures. Comparisons between our results and published experimental data showed good agreements and our model could explain the previously unexplained phenomena. Our advanced failure unit model might be further applied to other electromigration characteristics of metal lines.

The electromigration force in metallic bulk

NASA Astrophysics Data System (ADS)

Lodder, A.; Dekker, J. P.

1998-01-01

The voltage induced driving force on a migrating atom in a metallic system is discussed in the perspective of the Hellmann-Feynman force concept, local screening concepts and the linear-response approach. Since the force operator is well defined in quantum mechanics it appears to be only confusing to refer to the Hellmann-Feynman theorem in the context of electromigration. Local screening concepts are shown to be mainly of historical value. The physics involved is completely represented in ab initio local density treatments of dilute alloys and the implementation does not require additional precautions about screening, being typical for jellium treatments. The linear-response approach is shown to be a reliable guide in deciding about the two contributions to the driving force, the direct force and the wind force. Results are given for the wind valence for electromigration in a number of FCC and BCC metals, calculated using an ab initio KKR-Green's function description of a dilute alloy.

Electromigration and thermomigration in lead-free tin-silver-copper and eutectic tin-lead flip chip solder joints

NASA Astrophysics Data System (ADS)

Ou Yang, Fan-Yi

Phase separation and microstructure change of eutectic SnPb and SnAgCu flip chip solder joint were investigated under thermomigration, electromigration, stressmigration and the combination of these effects. Different morphological behaviors under DC and AC electromigration were seen. Phase separation with Pb rich phase migration to the anode was observed when current density is below 1.6 x 104 A/cm2 at 100°C. For some cases, phase separation of Pb-rich phase and Su-rich phase as well as refinement of lamellar microstructure has also been observed. We propose that the refinement is due to recrystallization. On the other hand, time-dependent melting of eutectic SnPb flip chip solder joints has been observed to occur frequently with current density above 1.6 x 104 A/cm 2at 100°C. It has been found that it is due to joule heating of the on-chip Al interconnects. We found that electromigration has especially generated voids at the anode of the Al. This damage has greatly increased the resistance of the Al, which produces the heat needed to melt the solder joint. Owing to the line-to-bump configuration in flip chip solder joints, current crowding occurs when electrons enters into or exits from the solder bump. At the cathode contact, current crowding induced pancake-type void formation was observed widely. Furthermore, at the anode contact, we note that hillock or whisker forms. The cross-sectioned surface in SnPb showed dimple and bulge after electromigration, while that of SnAgCu remained flat. The difference is due to a larger back stress in the SnAgCu, consequently electromigration in SnAgCu is slower than that in SnPb. For thermomigration in eutectic SnPb flip chip solder joints, phase separation of Sn and Pb occurred, with Pb moving to the cold end. Both Sn and Pb have a stepwise concentration profile across solder bump. Refinement of lamellar microstructure was observed, indicating recrystallization. Also, thermomigration in eutectic SnAgCu flip chip solder joint were presented. It seems that vacancy flux plays a dominant role in thermomigration in Pb-free solder bumps; voids formed on the cold end and Sn moved to the hot end.

Observation of electromigration in a Cu thin line by in situ coherent x-ray diffraction microscopy

NASA Astrophysics Data System (ADS)

Takahashi, Yukio; Nishino, Yoshinori; Furukawa, Hayato; Kubo, Hideto; Yamauchi, Kazuto; Ishikawa, Tetsuya; Matsubara, Eiichiro

2009-06-01

Electromigration (EM) in a 1-μm-thick Cu thin line was investigated by in situ coherent x-ray diffraction microscopy (CXDM). Characteristic x-ray speckle patterns due to both EM-induced voids and thermal deformation in the thin line were observed in the coherent x-ray diffraction patterns. Both parts of the voids and the deformation were successfully visualized in the images reconstructed from the diffraction patterns. This result not only represents the first demonstration of the visualization of structural changes in metallic materials by in situ CXDM but is also an important step toward studying the structural dynamics of nanomaterials using x-ray free-electron lasers in the near future.

Effect of the Angle Between Sn Grain c-Axis and Electron Flow Direction on Cu-Reinforced Composite Solder Joints Under Current Stressing

NASA Astrophysics Data System (ADS)

Wang, Yan; Han, Jing; Wang, Yishu; Ma, Limin; Guo, Fu

2018-01-01

With a body-centered tetragonal crystal structure, Sn grains were demonstrated to have highly anisotropic behaviors in various properties. The electromigration behavior of lead-free solder was impacted by the grain orientations. In this paper, the angle between the c-axis and the electron flow direction in composite solder joints (angle θ) was proven to be an important factor during electromigration. The effects of angle θ on the electromigration of composite solder joints were investigated in this paper. Cu particle-reinforced Sn3.5Ag solder joints were stressed under a current density of 104 A/cm2 at room temperature. After 336 h current stressing time, different electromigration phenomena occurred at the two sides of the grain boundary in the composite solder joint which contained two Sn grains with different angle θ. The Sn grains with the larger angle θ had a smaller growth rate of Cu6Sn5. In addition, a composite solder joint with a single Sn grain was set as the contrast and its angle θ was smaller than that of the composite solder joint with two Sn grains. The growth rate of Cu6Sn5 in the composite solder joint with a single grain was faster than that of the composite solder joint with two Sn grains.

Can amorphization take place in nanoscale interconnects?

PubMed

Kumar, S; Joshi, K L; van Duin, A C T; Haque, M A

2012-03-09

The trend of miniaturization has highlighted the problems of heat dissipation and electromigration in nanoelectronic device interconnects, but not amorphization. While amorphization is known to be a high pressure and/or temperature phenomenon, we argue that defect density is the key factor, while temperature and pressure are only the means. For nanoscale interconnects carrying modest current density, large vacancy concentrations may be generated without the necessity of high temperature or pressure due to the large fraction of grain boundaries and triple points. To investigate this hypothesis, we performed in situ transmission electron microscope (TEM) experiments on 200 nm thick (80 nm average grain size) aluminum specimens. Electron diffraction patterns indicate partial amorphization at modest current density of about 10(5) A cm(-2), which is too low to trigger electromigration. Since amorphization results in drastic decrease in mechanical ductility as well as electrical and thermal conductivity, further increase in current density to about 7 × 10(5) A cm(-2) resulted in brittle fracture failure. Our molecular dynamics (MD) simulations predict the formation of amorphous regions in response to large mechanical stresses (due to nanoscale grain size) and excess vacancies at the cathode side of the thin films. The findings of this study suggest that amorphization can precede electromigration and thereby play a vital role in the reliability of micro/nanoelectronic devices.

Electromigration-induced Plasticity and Texture in Cu Interconnects

NASA Astrophysics Data System (ADS)

Budiman, A. S.; Hau-Riege, C. S.; Besser, P. R.; Marathe, A.; Joo, Y.-C.; Tamura, N.; Patel, J. R.; Nix, W. D.

2007-10-01

Plastic deformation has been observed in damascene Cu interconnect test structures during an in-situ electromigration experiment and before the onset of visible microstructural damage (ie. voiding) using a synchrotron technique of white beam X-ray microdiffraction. We show here that the extent of this electromigration-induced plasticity is dependent on the texture of the Cu grains in the line. In lines with strong <111> textures, the extent of plastic deformation is found to be relatively large compared to our plasticity results in the previous study[1] using another set of Cu lines with weaker textures. This is consistent with our earlier observation that the occurrence of plastic deformation in a given grain can be strongly correlated with the availability of a <112> direction of the crystal in the proximity of the direction of the electron flow in the line (within an angle of 10°). In <111> out-of-plane oriented grains in a damascene interconnect scheme, the crystal plane facing the sidewall tends to be a {110} plane,[2-4] so as to minimize interfacial energy. Therefore, it is deterministic rather than probabilistic that the <111> grains will have a <112> direction nearly parallel to the direction of electron flow. Thus, strong <111> textures lead to more plasticity, as we observe.

A quick method for AlCu interconnect electromigration performance predicting and monitoring

NASA Astrophysics Data System (ADS)

Zhang, Wenjie; Yi, Leeward; Tao, Kai; Ma, Yue; Chang, Pingyi; Mao, Duli; Wu, Jin; Zou, S. C.

2006-05-01

The film properties and microstructures of (bottom)Si/SiO2/Ti(top) and (bottom)Si/SiO2/Ti/TiN/AlCu(top) stacks deposited by different processes were characterized. The resistivities of thin Ti films and the reflectivities of AlCu alloy films were found to correlate with the microstructure as well as the mean time to failure (MTTF) in the electromigration (EM) test. A quick-turn monitor for AlCu interconnect reliability in the semiconductor manufacturing industry was established.

Comparison of electrokinetic soil remediation methods using one fixed anode and approaching anodes.

PubMed

Shen, Zhemin; Chen, Xuejun; Jia, Jinping; Qu, Liya; Wang, Wenhua

2007-11-01

During the cation exchange membrane (CEM) enhanced electrokinetic (EK) soil remediation, the nearer to the anode, the higher are the H+ concentrations and the redox potentials. As both low pH and high redox potential are helpful to speed-up Cd electro-migration, soils near the anode can be quickly remedied. Usually EK process is operated with one fixed anode (FA). A novel CEM enhanced EK method with approaching anodes (AAs) is proposed to accelerate electro-migration effect. Several mesh Ti/Ru anodes were inserted as AAs in the treated soil. They were switched in turn from the anode towards the cathode. Thus high H+ ions concentrations and high redox potentials quickly migrate to the cathode. Consequently, soil remediation is accelerated and nearly 44% of energy and 40% of time can be saved. The mechanism of Cd electro-migration behavior in soils during CEM enhanced EK is described as the elution in an electrokinetically driven chromatogram.

A new electrophoretic focusing principle: focusing of nonamphoteric weak ionogenic analytes using inverse electromigration dispersion profiles.

PubMed

Gebauer, Petr; Malá, Zdena; Bocek, Petr

2010-03-01

This contribution introduces a new separation principle in CE which offers focusing of weak nonamphoteric ionogenic species and their inherent transport to the detector. The prerequisite condition for application of this principle is the existence of an inverse electromigration dispersion profile, i.e. a profile where pH is decreasing toward the anode or cathode for focusing of anionic or cationic weak analytes, respectively. The theory presented defines the principal conditions under which an analyte is focused on a profile of this type. Since electromigration dispersion profiles are migrating ones, the new principle offers inherent transport of focused analytes into the detection cell. The focusing principle described utilizes a mechanism different from both CZE (where separation is based on the difference in mobilities) and IEF (where separation is based on difference in pI), and hence, offers another separation dimension in CE. The new principle and its theory presented here are supplemented by convincing experiments as their proof.

Dielectric cracking produced by electromigration in microelectronic interconnects

NASA Astrophysics Data System (ADS)

Chiras, S.; Clarke, D. R.

2000-12-01

The development of stress during electromigration along Al lines, constrained within a dielectric in a coplanar test configuration, is measured. It is shown that, above a certain threshold current density, cracking of the dielectric is induced in the vicinity of the anode. Cracking of the dielectric leads to loss of mechanical constraint on the aluminum conductor which, in turn, leads to increases in electrical resistance with continued current flow. The electromigration-induced stresses are determined from the measured frequency shifts induced in a novel ruby strain sensor embedded immediately beneath the interconnect line on a sapphire substrate. The transparency of the sapphire substrate also facilitated the observation of a hitherto unreported form of dielectric cracking, namely cracking from the interconnect along internal interfaces. The observations of dielectric cracking are in agreement with a recent fracture mechanics model. Analysis of the stress data, together with the results of finite element calculations of the strain energy release rate for crack extension, gives a quantitative estimate of the effective valence Z*(=1.3±0.2) for aluminum.

High-resolution determination of the stress in individual interconnect lines and the variation due to electromigration

NASA Astrophysics Data System (ADS)

Ma, Qing; Chiras, S.; Clarke, D. R.; Suo, Z.

1995-08-01

Large tensile stresses usually exist in metallic interconnect lines on silicon substrates as a result of thermal mismatch. When a current is subsequently passed any divergence of atomic flux can create superimposed stress variations along the line. Together, these stresses can significantly influence the growth of voids and therefore affect interconnect reliability. In this work, a high-resolution (˜2 μm) optical spectroscopy method has been used to measure the localized stresses around passivated aluminum lines on a silicon wafer, both as-fabricated and after electromigration testing. The method is based on the piezospectroscopic properties of silicon, specifically the frequency shift of the Raman line at 520 R cm-1. By focusing a laser beam at points adjacent to the aluminum lines, the Raman signal was excited and collected. The stresses in the aluminum lines can then be derived from the stresses in the silicon using finite element methods. Large variations of stress along an electromigration-tested line were observed and compared to a theoretical model based on differences in effective diffusivities from grain to grain in a polycrystalline interconnect line.

Electromigration analysis of solder joints under ac load: A mean time to failure model

NASA Astrophysics Data System (ADS)

Yao, Wei; Basaran, Cemal

2012-03-01

In this study, alternating current (ac) electromigration (EM) degradation simulations were carried out for Sn95.5%Ag4.0%Cu0.5 (SAC405- by weight) solder joints. Mass transport analysis was conducted with viscoplastic material properties for quantifying damage mechanism in solder joints. Square, sine, and triangle current wave forms ac were used as input signals. dc and pulsed dc (PDC) electromigration analysis were conducted for comparison purposes. The maximum current density ranged from 2.2×106A/cm2 to 5.0×106A/cm2, frequency ranged from 0.05 Hz to 5 Hz with ambient temperature varying from 350 K to 450 K. Because the room temperature is nearly two-thirds of SAC solder joint's melting point on absolute temperature scale (494.15 K), viscoplastic material model is essential. Entropy based damage evolution model was used to investigate mean time to failure (MTF) behavior of solder joints subjected to ac stressing. It was observed that MTF was inversely proportional to ambient temperature T1.1 in Celsius and also inversely proportional to current density j0.27 in A/cm2. Higher frequency will lead to a shorter lifetime with in the frequency range we studied, and a relationship is proposed as MTF∝f-0.41. Lifetime of a solder joint subjected to ac is longer compared with dc and PDC loading conditions. By introducing frequency, ambient temperature and current density dependency terms, a modified MTTF equation was proposed for solder joints subjected to ac current stressing.

Statistical analysis of early failures in electromigration

NASA Astrophysics Data System (ADS)

Gall, M.; Capasso, C.; Jawarani, D.; Hernandez, R.; Kawasaki, H.; Ho, P. S.

2001-07-01

The detection of early failures in electromigration (EM) and the complicated statistical nature of this important reliability phenomenon have been difficult issues to treat in the past. A satisfactory experimental approach for the detection and the statistical analysis of early failures has not yet been established. This is mainly due to the rare occurrence of early failures and difficulties in testing of large sample populations. Furthermore, experimental data on the EM behavior as a function of varying number of failure links are scarce. In this study, a technique utilizing large interconnect arrays in conjunction with the well-known Wheatstone Bridge is presented. Three types of structures with a varying number of Ti/TiN/Al(Cu)/TiN-based interconnects were used, starting from a small unit of five lines in parallel. A serial arrangement of this unit enabled testing of interconnect arrays encompassing 480 possible failure links. In addition, a Wheatstone Bridge-type wiring using four large arrays in each device enabled simultaneous testing of 1920 interconnects. In conjunction with a statistical deconvolution to the single interconnect level, the results indicate that the electromigration failure mechanism studied here follows perfect lognormal behavior down to the four sigma level. The statistical deconvolution procedure is described in detail. Over a temperature range from 155 to 200 °C, a total of more than 75 000 interconnects were tested. None of the samples have shown an indication of early, or alternate, failure mechanisms. The activation energy of the EM mechanism studied here, namely the Cu incubation time, was determined to be Q=1.08±0.05 eV. We surmise that interface diffusion of Cu along the Al(Cu) sidewalls and along the top and bottom refractory layers, coupled with grain boundary diffusion within the interconnects, constitutes the Cu incubation mechanism.

Oxygen adsorption on Cu-9 at. %Al(111) studied by low energy electron diffraction and Auger electron spectroscopy

NASA Astrophysics Data System (ADS)

Yoshitake, Michiko; Bera, Santanu; Yamauchi, Yasuhiro; Song, Weijie

2003-07-01

Cu-based alloys have been used for electric cables for long time. In the field of microelectronics, Al had been used for electrical wiring. However, it became clear that electromigration occurs in Al that causes breaking of wires in minute wirings. Due to this problem, Cu wiring is used in most advanced microprocessors. Cu metal is more corrosive than Al and Cu-based alloys with a small amount of Al is expected to solve problems both on electromigration and corrosion. The initial stage of corrosion is oxygen adsorption. We studied surface segregation of Al on Cu-9% Al(111) and oxygen adsorption on the surface with/without Al segregation in ultrahigh vacuum by low energy electron diffraction (LEED) and Auger electron spectroscopy. It was found that Al segregates on the surface to form (√3×√3)R30° structure and the structure vanishes above 595 K to give (1×1) structure while Al still segregates. The specimen was exposed to oxygen at different temperatures. The amount of oxygen uptake was not structure dependent but temperature dependent. Below 595 K, only a small amount of oxygen adsorbed. Between 595 and 870 K, oxygen adsorbed surface showed amorphous LEED pattern. The specimen was annealed at 1070 K after oxygen exposure. When the specimen was exposed oxygen below 870 K, the oxygen Auger intensity decreased significantly by annealing and the annealed surface showed (√3×√3)R30° structure at room temperature. When the specimen was exposed to oxygen at 870 K, diffused spots developed newly in LEED pattern but the pattern disappeared after 1070 K annealing while oxygen Auger intensity remained almost constant. Exposing the specimen to oxygen at 995 K resulted in clear spots in the LEED pattern, which were attributed to the (7/√3×7√3)R30° structure.

Identification of Microorganisms by Modern Analytical Techniques.

PubMed

Buszewski, Bogusław; Rogowska, Agnieszka; Pomastowski, Paweł; Złoch, Michał; Railean-Plugaru, Viorica

2017-11-01

Rapid detection and identification of microorganisms is a challenging and important aspect in a wide range of fields, from medical to industrial, affecting human lives. Unfortunately, classical methods of microorganism identification are based on time-consuming and labor-intensive approaches. Screening techniques require the rapid and cheap grouping of bacterial isolates; however, modern bioanalytics demand comprehensive bacterial studies at a molecular level. Modern approaches for the rapid identification of bacteria use molecular techniques, such as 16S ribosomal RNA gene sequencing based on polymerase chain reaction or electromigration, especially capillary zone electrophoresis and capillary isoelectric focusing. However, there are still several challenges with the analysis of microbial complexes using electromigration technology, such as uncontrolled aggregation and/or adhesion to the capillary surface. Thus, an approach using capillary electrophoresis of microbial aggregates with UV and matrix-assisted laser desorption ionization time-of-flight MS detection is presented.

A study on electromigration-inducing intergranular fracture of fine silver alloy wires

NASA Astrophysics Data System (ADS)

Hsueh, Hao-Wen; Hung, Fei-Yi; Lui, Truan-Sheng

2017-01-01

In this study, Pd-coated Cu, Ag (purity = 4 N), and Ag alloy (Ag-8Au-3Pd) wires were employed to measure the tensile properties during current stressing using the so-called dynamic current tensile (DCT) test. Both the tensile strength and elongation of the wires decreased dramatically in the DCT test, particularly of the Ag-based wires, and the fracture morphology of the Cu-based and Ag-based wires was ductile fracture and intergranular fracture, respectively. Compared to the Cu-based wires, electromigration occurred more easily in the Ag-based wires, and it always generated voids and cracks at the grain boundaries; therefore, the fracture morphology of the Ag-based wires was intergranular fracture owing to the weakened grain boundary. Further, the results indicated that the Ag-based wires could not carry a higher current density than the Cu-based wires, primarily because their extremely low strength and elongation in current stressing might cause serious reliability problems.

Effect of Joule heating and current crowding on electromigration in mobile technology

NASA Astrophysics Data System (ADS)

Tu, K. N.; Liu, Yingxia; Li, Menglu

2017-03-01

In the present era of big data and internet of things, the use of microelectronic products in all aspects of our life is manifested by the ubiquitous presence of mobile devices as i-phones and wearable i-products. These devices are facing the need for higher power and greater functionality applications such as in i-health, yet they are limited by physical size. At the moment, software (Apps) is much ahead of hardware in mobile technology. To advance hardware, the end of Moore's law in two-dimensional integrated circuits can be extended by three-dimensional integrated circuits (3D ICs). The concept of 3D ICs has been with us for more than ten years. The challenge in 3D IC technology is dense packing by using both vertical and horizontal interconnections. Mass production of 3D IC devices is behind schedule due to cost because of low yield and uncertain reliability. Joule heating is serious in a dense structure because of heat generation and dissipation. A change of reliability paradigm has advanced from failure at a specific circuit component to failure at a system level weak-link. Currently, the electronic industry is introducing 3D IC devices in mainframe computers, where cost is not an issue, for the purpose of collecting field data of failure, especially the effect of Joule heating and current crowding on electromigration. This review will concentrate on the positive feedback between Joule heating and electromigration, resulting in an accelerated system level weak-link failure. A new driving force of electromigration, the electric potential gradient force due to current crowding, will be reviewed critically. The induced failure tends to occur in the low current density region.

A Field Test of Electromigration as a Method for Remediating Sulfate from Shallow Ground Water

USGS Publications Warehouse

Patterson, C.G.; Runnells, D.D.

1996-01-01

Electromigration offers a potential tool for remediating ground water contaminated with highly soluble components, such as Na+, Cl-, NO3-, and SO4-. A field experiment was designed to test the efficacy of electromigration for preconcentrating dissolved SO42- in ground water associated with a fossil-fuel power plant. Two shallow wells, 25 feet apart (one 25 feet deep, the other 47 feet deep), were constructed in the upper portion of an unconfined alluvial aquifer. The wells were constructed with a double-wall design, with an outer casing of 4-inch PVC and an inner tube of 2-inch PVC; both were fully slotted (0.01 inch). Electrodes were constructed by wrapping the inner tubing with a 100-foot length of rare-earth metal oxide/copper wire. An electrical potential of 10.65 volts DC was applied, and tests were run for periods of 12, 44, and 216 hours. Results showed large changes in the pH from the initial pH of ground water of about 7.5 to values of approximately 2 and 12 at the anode and cathode, respectively. Despite the fact that the test conditions were far from ideal, dissolved SO42- was significantly concentrated at the anode. Over a period of approximately nine days, the concentration of SO42- at the anode reached what appeared to be a steady-state value of 2200 mg/L, compared to the initial value in ground water of approximately 1150 mg/L. The results of this field test should encourage further investigation of electromigration as a tool in the remediation of contaminated ground water.

New methodology for capillary electrophoresis with ESI-MS detection: Electrophoretic focusing on inverse electromigration dispersion gradient. High-sensitivity analysis of sulfonamides in waters.

PubMed

Malá, Zdena; Gebauer, Petr; Boček, Petr

2016-09-07

This article describes for the first time the combination of electrophoretic focusing on inverse electromigration dispersion (EMD) gradient, a new separation principle described in 2010, with electrospray-ionization (ESI) mass spectrometric detection. The separation of analytes along the electromigrating EMD profile proceeds so that each analyte is focused and concentrated within the profile at a particular position given by its pKa and ionic mobility. The proposed methodology combines this principle with the transport of the focused zones to the capillary end by superimposed electromigration, electroosmotic flow and ESI suction, and their detection by the MS detector. The designed electrolyte system based on maleic acid and 2,6-lutidine is suitable to create an inverse EMD gradient of required properties and its components are volatile enough to be compatible with the ESI interface. The characteristic properties of the proposed electrolyte system and of the formed inverse gradient are discussed in detail using calculated diagrams and computer simulations. It is shown that the system is surprisingly robust and allows sensitive analyses of trace amounts of weak acids in the pKa range between approx. 6 and 9. As a first practical application of electrophoretic focusing on inverse EMD gradient, the analysis of several sulfonamides in waters is reported. It demonstrates the potential of the developed methodology for fast and high-sensitivity analyses of ionic trace analytes, with reached LODs around 3 × 10(-9) M (0.8 ng mL(-1)) of sulfonamides in spiked drinking water without any sample pretreatment. Copyright © 2016 Elsevier B.V. All rights reserved.

Structure control of tungsten nanocontacts through pulsed-voltage application

NASA Astrophysics Data System (ADS)

Suzuki, Yasuchika; Kizuka, Tokushi

2018-05-01

The structural variation in tungsten nanocontacts (NCs) during a pulsed-voltage application was observed in situ by high-resolution transmission electron microscopy. The direction of electromigration in the NCs changed from the well-known direction to the opposite direction at a critical voltage of 0.9 V. Upon applying a higher pulsed voltage of 2.5 V, the NC structure changed to amorphous, with an average conductance density decreased to 82% of that of the crystalline NCs. We demonstrated that the external shape and texture of tungsten NCs can be controlled with an atomic precision through electromigration and amorphization by a pulsed-voltage application.

Utilization of electromigration in civil and environmental engineering--processes, transport rates and matrix changes.

PubMed

Ottosen, Lisbeth M; Christensen, Iben V; Rorig-Dalgård, Inge; Jensen, Pernille E; Hansen, Henrik K

2008-07-01

Electromigration (movement of ions in an applied electric field) is utilized for supply or extraction of ions from various porous materials within both civil and environmental engineering. In civil engineering, most research has been conducted on the removal of chlorides from concrete to hinder reinforcement corrosion while in environmental engineering remediation of heavy metal polluted soil is the issue most studied. Never the less, experiments have been conducted with utilization for several other materials and purposes within both engineering fields. Even though there are many topics of common interest in the use of electromigration for the two fields, there is no tradition for collaboration. The present paper is a review with the aim of pointing out areas of shared interest. Focus is laid on the purposes of the different processes, transport rates of various ions in different materials and on changes in the matrix itself. Desorption and dissolution of the target elements into ionic form is a key issue to most of the processes, and can be the limiting step. The removal rate is generally below 1 cm day(- 1), but it can be much less than 1 mm day(- 1) when desorption is slow and insufficient. Matrix changes occurs under the action of the applied electric field and it includes both physico-chemical and hydrological changes. Some of the solid phases is weathered and new can be formed. Increased fundamental understanding of the effects and side effects, when applying the electric field to a porous material, can lead to improvement of the known technologies and possibly to new applications.

Glyphosate analysis using sensors and electromigration separation techniques as alternatives to gas or liquid chromatography.

PubMed

Gauglitz, Günter; Wimmer, Benedikt; Melzer, Tanja; Huhn, Carolin

2018-01-01

Since its introduction in 1974, the herbicide glyphosate has experienced a tremendous increase in use, with about one million tons used annually today. This review focuses on sensors and electromigration separation techniques as alternatives to chromatographic methods for the analysis of glyphosate and its metabolite aminomethyl phosphonic acid. Even with the large number of studies published, glyphosate analysis remains challenging. With its polar and depending on pH even ionic functional groups lacking a chromophore, it is difficult to analyze with chromatographic techniques. Its analysis is mostly achieved after derivatization. Its purification from food and environmental samples inevitably results incoextraction of ionic matrix components, with a further impact on analysis derivatization. Its purification from food and environmental samples inevitably results in coextraction of ionic matrix components, with a further impact on analysis and also derivatization reactions. Its ability to form chelates with metal cations is another obstacle for precise quantification. Lastly, the low limits of detection required by legislation have to be met. These challenges preclude glyphosate from being analyzed together with many other pesticides in common multiresidue (chromatographic) methods. For better monitoring of glyphosate in environmental and food samples, further fast and robust methods are required. In this review, analytical methods are summarized and discussed from the perspective of biosensors and various formats of electromigration separation techniques, including modes such as capillary electrophoresis and micellar electrokinetic chromatography, combined with various detection techniques. These methods are critically discussed with regard to matrix tolerance, limits of detection reached, and selectivity.

Activation energy associated with the electromigration of oligosaccharides through viscosity modifier and polymeric additive containing background electrolytes.

PubMed

Kerékgyártó, Márta; Járvás, Gábor; Novák, Levente; Guttman, András

2016-02-01

The activation energy related to the electromigration of oligosaccharides can be determined from their measured electrophoretic mobilities at different temperatures. The effects of a viscosity modifier (ethylene glycol) and a polymeric additive (linear polyacrylamide) on the electrophoretic mobility of linear sugar oligomers with α1-4 linked glucose units (maltooligosaccharides) were studied in CE using the activation energy concept. The electrophoretic separations of 8-aminopyrene-1,3,6-trisulfonate-labeled maltooligosaccharides were monitored by LIF detection in the temperature range of 20-50°C, using either 0-60% ethylene glycol (viscosity modifier) or 0-3% linear polyacrylamide (polymeric additive) containing BGEs. Activation energy curves were constructed based on the slopes of the Arrhenius plots. With the use of linear polyacrylamide additive, solute size-dependent activation energy variations were found for the maltooligosaccharides with polymerization degrees below and above maltoheptaose (DP 7), probably due to molecular conformation changes and possible matrix interaction effects. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Electromigration techniques--a fast and economical tool for differentiation of similar strains of microorganisms.

PubMed

Horká, Marie; Horký, Jaroslav; Kubesová, Anna; Mazanec, Karel; Matousková, Hana; Slais, Karel

2010-07-01

The detection and identification of pathogens currently relies upon a very diverse range of techniques and skills, from traditional cultivation and taxonomic procedures to modern rapid and sensitive diagnostic methods. Real-time PCR is now exploited as a front line diagnostic screening tool in human, animal and plant health as well as bio-security. Nevertheless, new techniques for pathogen identification, particularly of unknown samples, are needed. In this study we propose the combination of electrophoresis-based procedures for the fast differentiation of microorganisms. The method feasibility is proved on the model of seven similar strains of Pseudomonas syringae pathovars from 37 sources, identified by gas chromatography of fatty acid methyl esters. The results from the routine laboratory were compared with results of the combination of the developed capillary and gel electrophoresis as well as mass spectrometry. According to our experiments appropriate combination of electromigration techniques appears to be useful for the fast and economical differentiation of unknown microorganisms.

A nonviral transfection approach in vitro: the design of a gold nanoparticle vector joint with microelectromechanical systems.

PubMed

Jen, Chun-Ping; Chen, Yu-Hung; Fan, Chun-sheng; Yeh, Chen-Sheng; Lin, Yu-Cheng; Shieh, Dar-Bin; Wu, Chao-Ling; Chen, Dong-Hwang; Chou, Chen-Hsi

2004-02-17

Au nanoparticles modified with 21-base thiolated-oligonucleotides have been evaluated as delivery vehicles for the development of a nonviral transfection platform. The electromigration combined with electroporation for DNA delivery in an osteoblast like cell was employed to test on microchips. Electroporation introduces foreign materials into cells by applying impulses of electric field to induce multiple transient pores on the cell membrane through dielectric breakdown of the cell membrane. On the basis of the characteristic surface plasmon of the Au particles, UV-vis absorption was utilized to qualitatively judge the efficiency of delivery. Transmission electron microscopy images and atomic absorption measurements (quantitative analysis) provided evidence of the bare Au and Au/oligonucleotide nanoparticles before and after electroporation and electromigration function. The experiments demonstrated that electrophoretic migration followed by electroporation significantly enhanced the transportation efficiency of the nanoparticle-oligonucleotide complexes as compared with electroporation alone. Most interestingly, Au capped with oligonucleotides led to optimal performance. On the other hand, the bare Au colloidal suspensions resulted in aggregation, which might be an obstacle to the internalization process. In addition, analytical results demonstrated an increase in the local particle concentrations on the cell surface that provided additional support for the mechanism underlying the improved Au nanoparticle transportation into cells in the presence of electromigration function.

Electromigration failure mode concerning negative resistance shift of Cu interconnects buried in porous low-k dielectric

NASA Astrophysics Data System (ADS)

Zheng, Hui; Yin, Binfeng; Yu, Hewei; Chen, Leigang; Gao, Lin; Zhou, Ke; Kuo, Chinte

2017-02-01

Electromigration failure mode concerning a negative resistance shift of 4%-11% and cathode burnout was reported for Cu interconnects buried in porous low-k in this paper. Evidence for oxidation and debonding of Ta/TaN liner at high temperature was revealed, which was demonstrated to have been enabled by the unsealed porous low-k due to moisture uptake. The cathode burnout was thus attributed to severe Joule heating induced in the insulated liner after oxidation. The resistance decay of Cu also exhibited to be mainly consistent with the calculation from specularity recovery of electron scattering at the Cu/Ta interface after oxidation and debonding of the liner, although other factors like strain relaxation may also have some contribution.

X-Ray Microdiffraction as a Probe to Reveal Flux Divergences in Interconnects

NASA Astrophysics Data System (ADS)

Spolenak, R.; Tamura, N.; Patel, J. R.

2006-02-01

Most reliability issues in interconnect systems occur at a local scale and many of them include the local build-up of stresses. Typical failure mechanisms are electromigration and stress voiding in interconnect lines and fatigue in surface acoustic wave devices. Thus a local probe is required for the investigation of these phenomena. In this paper the application of the Laue microdiffraction technique to investigate flux divergences in interconnect systems will be described. The deviatoric strain tensor of single grains can be correlated with the local microstructure, orientation and defect density. Especially the latter led to recent results about the correlation of stress build-up and orientation in Cu lines and electromigration-induced grain rotation in Cu and Al lines.

The transport behavior of As, Cu, Pb, and Zn during electrokinetic remediation of a contaminated soil using electrolyte conditioning

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

Yang, Jung-Seok; Kwon, Man Jae; Choi, Jaeyoung

2014-12-01

Electrokinetic remediation (also known as electrokinetics) is a promising technology for removing metals from fine-grained soils. However, few studies have been conducted regarding the transport behavior of multi-metals during electrokinetics. We investigated the transport of As, Cu, Pb, and Zn from soils during electrokinetics, the metal fractionation before and after electrokinetics, the relationships between metal transport and fractionation, and the effects of electrolyte conditioning. The main transport mechanisms of the metals were electroosmosis and electromigration during the first two weeks and electromigration during the following weeks. The direction of electroosmotic flow was from the anode to the cathode, and themore » metals in the dissolved and reducible-oxides fractions were transported to the anode or cathode by electromigration according to the chemical speciation of the metal ions in the pore water. Moreover, a portion of the metals that were initially in the residual fraction transitioned to the reducible and soluble fractions during electrokinetic treatment. However, this alteration was slow and resulted in decreasing metal removal rates as the electrokinetic treatment progressed. In addition, the use of NaOH, H3PO4, and Na2SO4 as electrolytes resulted in conditions that favored the precipitation of metal hydroxides, phosphates, and sulfates in the soil. These results demonstrated that metal removal was affected by the initial metal fractionation, metal speciation in the pore solution, and the physical–chemical parameters of the electrolytes, such as pH and electrolyte composition. Therefore, the treatment time, use of chemicals, and energy consumption could be reduced by optimizing pretreatment and by choosing appropriate electrolytes for the target metals.« less

Removal of organic pollutants and heavy metals in soils by electrokinetic remediation.

PubMed

Ricart, M T; Pazos, M; Gouveia, S; Cameselle, C; Sanroman, M A

2008-07-01

In this work, the feasibility of electrokinetic remediation for the restoration of polluted soil with organic and inorganic compounds had been development and evaluated using a model soil sample. The model soil was prepared with kaolinite clay artificially polluted in the laboratory with chromium and an azo dye: Reactive Black 5 (RB5). The electromigration of Cr in a spiked kaolinite sample was studied in alkaline conditions. Despite of the high pH registered in the kaolinite sample (around pH 9.5), Cr migrated towards the cathode and it was accumulated in the cathode chamber forming a white precipitate. The removal was not complete, and 23% of the initial Cr was retained into the kaolinite sample close to the cathode side. The azo dye RB5 could be effectively removed from kaolinite by electrokinetics and the complete cleanup of the kaolinite could be achieved in alkaline environment. In this condition, RB5 formed an anion that migrated towards the anode where it was accumulated and quickly degraded upon the electrode surface. The electrokinetic treatment of a kaolinite sample polluted with both Cr and RB5 yielded very good results. The removal of Cr was improved compared to the experiment where Cr was the only pollutant, and RB5 reached a removal as high as 95%. RB5 was removed by electromigration towards the anode, where the dye was degraded upon the surface of the electrode by electrochemical oxidation. Cr was transported towards the cathode by electromigration and electroosmosis. It is supposed that the interaction among RB5 and Cr into the kaolinite sample prevented premature precipitation and allow Cr to migrate and concentrate in the cathode chamber.

1/f noise measurements for faster evaluation of electromigration in advanced microelectronics interconnections

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

Beyne, Sofie, E-mail: sofie.beyne@imec.be; De Wolf, Ingrid; imec, Kapeldreef 75, B-3001 Leuven

The use of 1/f noise measurements is explored for the purpose of finding faster techniques for electromigration (EM) characterization in advanced microelectronic interconnects, which also enable a better understanding of its underlying physical mechanisms. Three different applications of 1/f noise for EM characterization are explored. First, whether 1/f noise measurements during EM stress can serve as an early indicator of EM damage. Second, whether the current dependence of the noise power spectral density (PSD) can be used for a qualitative comparison of the defect concentration of different interconnects and consequently also their EM lifetime t50. Third, whether the activation energiesmore » obtained from the temperature dependence of the 1/f noise PSD correspond to the activation energies found by means of classic EM tests. In this paper, the 1/f noise technique has been used to assess and compare the EM properties of various advanced integration schemes and different materials, as they are being explored by the industry to enable advanced interconnect scaling. More concrete, different types of copper interconnects and one type of tungsten interconnect are compared. The 1/f noise measurements confirm the excellent electromigration properties of tungsten and demonstrate a dependence of the EM failure mechanism on copper grain size and distribution, where grain boundary diffusion is found to be a dominant failure mechanism.« less

Treatment Prevents Corrosion in Steel and Concrete Structures

NASA Technical Reports Server (NTRS)

2007-01-01

In the mid-1990s, to protect rebar from corrosion, NASA developed an electromigration technique that sends corrosion-inhibiting ions into rebar to prevent rust, corrosion, and separation from the surrounding concrete. Kennedy Space Center worked with Surtreat Holding LLC, of Pittsburgh, Pennsylvania, a company that had developed a chemical option to fight structural corrosion, combining Surtreat's TPS-II anti-corrosive solution and electromigration. Kennedy's materials scientists reviewed the applicability of the chemical treatment to the electromigration process and determined that it was an effective and environmentally friendly match. Ten years later, NASA is still using this approach to fight concrete corrosion, and it has also developed a new technology that will further advance these efforts-a liquid galvanic coating applied to the outer surface of reinforced concrete to protect the embedded rebar from corrosion. Surtreat licensed this new coating technology and put it to use at the U.S. Army Naha Port, in Okinawa, Japan. The new coating prevents corrosion of steel in concrete in several applications, including highway and bridge infrastructures, piers and docks, concrete balconies and ceilings, parking garages, cooling towers, and pipelines. A natural compliment to the new coating, Surtreat's Total Performance System provides diagnostic testing and site analysis to identify the scope of problems for each project, manufactures and prescribes site-specific solutions, controls material application, and verifies performance through follow-up testing and analysis.

Microwave evaluation of electromigration susceptibility in advanced interconnects

NASA Astrophysics Data System (ADS)

Sunday, Christopher E.; Veksler, Dmitry; Cheung, Kin C.; Obeng, Yaw S.

2017-11-01

Traditional metrology has been unable to adequately address the needs of the emerging integrated circuits (ICs) at the nano scale; thus, new metrology and techniques are needed. For example, the reliability challenges in fabrication need to be well understood and controlled to facilitate mass production of through-substrate-via (TSV) enabled three-dimensional integrated circuits (3D-ICs). This requires new approaches to the metrology. In this paper, we use the microwave propagation characteristics to study the reliability issues that precede the physical damage caused by electromigration in the Cu-filled TSVs. The pre-failure microwave insertion losses and group delay are dependent on both the device temperature and the amount of current forced through the devices-under-test. The microwave insertion losses increase with the increase in the test temperature, while the group delay increases with the increase in the forced direct current magnitude. The microwave insertion losses are attributed to the defect mobility at the Cu-TiN interface, and the group delay changes are due to resistive heating in the interconnects, which perturbs the dielectric properties of the cladding dielectrics of the copper fill in the TSVs.

Electromigration Failure Mechanism in Sn-Cu Solder Alloys with OSP Cu Surface Finish

NASA Astrophysics Data System (ADS)

Chu, Ming-Hui; Liang, S. W.; Chen, Chih; Huang, Annie T.

2012-09-01

Organic solderable preservative (OSP) has been adopted as the Cu substrate surface finish in flip-chip solder joints for many years. In this study, the electromigration behavior of lead-free Sn-Cu solder alloys with thin-film under bump metallization and OSP surface finish was investigated. The results showed that severe damage occurred on the substrate side (cathode side), whereas the damage on the chip side (cathode side) was not severe. The damage on the substrate side included void formation, copper dissolution, and formation of intermetallic compounds (IMCs). The OSP Cu interface on the substrate side became the weakest point in the solder joint even when thin-film metallization was used on the chip side. Three-dimensional simulations were employed to investigate the current density distribution in the area between the OSP Cu surface finish and the solder. The results indicated that the current density was higher along the periphery of the bonding area between the solder and the Cu pad, consistent with the area of IMC and void formation in our experimental results.

Multiscale Microstructures and Microstructural Effects on the Reliability of Microbumps in Three-Dimensional Integration

PubMed Central

Huang, Zhiheng; Xiong, Hua; Wu, Zhiyong; Conway, Paul; Altmann, Frank

2013-01-01

The dimensions of microbumps in three-dimensional integration reach microscopic scales and thus necessitate a study of the multiscale microstructures in microbumps. Here, we present simulated mesoscale and atomic-scale microstructures of microbumps using phase field and phase field crystal models. Coupled microstructure, mechanical stress, and electromigration modeling was performed to highlight the microstructural effects on the reliability of microbumps. The results suggest that the size and geometry of microbumps can influence both the mesoscale and atomic-scale microstructural formation during solidification. An external stress imposed on the microbump can cause ordered phase growth along the boundaries of the microbump. Mesoscale microstructures formed in the microbumps from solidification, solid state phase separation, and coarsening processes suggest that the microstructures in smaller microbumps are more heterogeneous. Due to the differences in microstructures, the von Mises stress distributions in microbumps of different sizes and geometries vary. In addition, a combined effect resulting from the connectivity of the phase morphology and the amount of interface present in the mesoscale microstructure can influence the electromigration reliability of microbumps. PMID:28788356

ELECTROKINETIC REMEDIATION: BASICS AND TECHNOLOGY STATUS

EPA Science Inventory

Electrokinetic remediation, variably named as electrochemical soil processing, electromigration, electrokinetic decontamination or electroreclamation uses electric currents to extract radionuclides, heavy metals, certain organic compounds, or mixed inorganic species and some orga...

The microstructure, mechanical stress, texture, and electromigration behavior of Al-Pd alloys

NASA Astrophysics Data System (ADS)

Rodbell, K. P.; Knorr, D. B.; Mis, J. D.

1993-06-01

As the minimum feature size of interconnect lines decreases below 0.5 urn, the need to control the line microstructure becomes increasingly important. The alloy content, deposition process, fabrication method, and thermal history all determine the microstructure of an interconnect, which, in turn, affects its performance and reliability. The motivation for this work was to characterize the microstructure of various sputtered Al-Pd alloys (Al-0.3wt.%Pd, Al-2Cu-0.3Pd, and Al-0.3Nb-0.3Pd) vs sputtered Al-Cu control samples (Al-0.5Cu and Al-2Cu) and to assess the role of grain size, mechanical stress, and crystallographic texture on the electromigration behavior of submicrometer wide lines. The grain size, mechanical stress, and texture of blanket films were measured as a function of annealing. The as-deposited film stress was tensile and followed a similar stress history on heating for all of the films; on cooling, however, significant differences were observed between the Al-Pd and Al-Cu films in the shape of their stress-temperature-curves. A strong (111) crystallographic texture was typically found for Al-Cu films deposited on SiO2. A stronger (111) texture resulted when Al-Cu was deposited on 25 nm titanium. Al-0.3Pd films, however, exhibited either a weak (111) or (220) texture when deposited on SiO2, which reverted to a strong (111) texture when deposited on 25 nm titanium. The electromigration lifetimes of passivated, ≈0.7 μm wide lines at 250°C and 2.5 × 106 A/cm2 for both single and multi-level samples (separated with W studs) are reported. The electromigration behavior of Al-0.3Pd was found to be less dependent on film microstructure than on the annealing atmosphere used, i.e. forming gas (90% N2-10%H2) annealed Al-0.3Pd films were superior to all of the alloys investigated, while annealing in only N2 resulted in poor lifetimes.

A general strategy for the ultrafast surface modification of metals.

PubMed

Shen, Mingli; Zhu, Shenglong; Wang, Fuhui

2016-12-07

Surface modification is an essential step in engineering materials that can withstand the increasingly aggressive environments encountered in various modern energy-conversion systems and chemical processing industries. However, most traditional technologies exhibit disadvantages such as slow diffusion kinetics, processing difficulties or compatibility issues. Here, we present a general strategy for the ultrafast surface modification of metals inspired by electromigration, using aluminizing austenitic stainless steel as an example. Our strategy facilitates the rapid formation of a favourable ductile surface layer composed of FeCrAl or β-FeAl within only 10 min compared with several hours in conventional processes. This result indicates that electromigration can be used to achieve the ultrafast surface modification of metals and can overcome the limitations of traditional technologies. This strategy could be used to aluminize ultra-supercritical steam tubing to withstand aggressive oxidizing environments.

Mechanical Stress Effects on Electromigration Voiding in a Meandering Test Stripe

NASA Technical Reports Server (NTRS)

Lowry, L. E.; Tai, B. H.; Mattila, J.; Walsh, L. H.

1993-01-01

Earlier experimental findings concluded that electromigratin voids in these meandering stripe test structures were not randomly distributed and that void nucleation frequenly occurred sub-surface at the metal/thermal oxide interface.

Electromigration effect upon the Sn-0.7 wt% Cu/Ni and Sn-3.5 wt% Ag/Ni interfacial reactions

NASA Astrophysics Data System (ADS)

Chen, Chih-ming; Chen, Sinn-wen

2001-08-01

This study investigates the effect of electromigration upon the interfacial reactions between the promising lead-free solders, Sn-Cu and Sn-Ag, with Ni substrate. Sandwich-type reaction couples, Sn-0.7 wt% Cu/Ni/Sn-0.7 wt% Cu and Sn-3.5 wt% Ag/Ni/Sn-3.5 wt% Ag, were reacted at 160, 180, and 200 °C for various lengths of time with and without the passage of electric currents. Without passage of electric currents through the couples, only one intermetallic compound Ni3Sn4 with ˜7 at. % Cu solubility was found at both interfaces of the Sn-0.7 wt% Cu/Ni couples. With the passage of an electric current of 500 A/cm2 density, the Cu6Sn5 phase was formed at the solder/Ni interface besides the Ni3Sn4 phase. Similar to those without the passage of electric currents, only the Ni3Sn4 phase was found at the Ni/solder interface. Directions of movement of electrons, Sn, and Cu atoms are the same at the solder/Ni interface, and the growth rates of the intermetallic layers were enhanced. At the Ni/solder interface, the electrons flow in the opposite direction of the Sn and Cu movement, and the growth rates of the intermetallic layers were retarded. Only the Ni3Sn4 phase was formed from the Sn-3.5 wt% Ag/Ni interfacial reaction with and without the passage of electric currents. Similar to the Sn-0.7 wt% Cu/Ni system, the movement of electrons enhances or retards the growth rates of the intermetallic layers at the solder/Ni and Ni/solder interfaces, respectively. Calculation results show the apparent effective charge za* decreases in magnitude with raising temperatures, which indicates the electromigration effect becomes insignificant at higher temperatures.

Electromigration and solid state aging of flip chip solder joints and analysis of tin whisker on lead-frame

NASA Astrophysics Data System (ADS)

Lee, Taekyeong

Electromigration and solid state aging in flip chip joint, and whisker on lead frame of Pb-containing (eutectic SnPb) and Pb-free solders (SnAg 3.5, SnAg3.8Cu0.7, and SnCu0.7), have been studied systematically, using Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Analysis (EDX), and synchrotron radiation. The high current density in flip chip joint drives the diffusion of atoms of eutectic SnPb and SnAgCu. A marker is used to measure the diffusion flux in a half cross-sectioned solder joint. SnAgCu shows higher resistance against electromigration than eutectic SnPb. In the half cross-sectioned solder joint, void growth is the dominant failure mechanism. However, the whole solder balls in the underfill show that the failure mechanism is a result from the dissolution of electroless Ni under bump metallization (UBM) of about 10 mum thickness. The growth rate between intermetallic compounds in molten and solid solders differed by four orders of magnitude. In liquid solder, the growth rate is about 1 mum/min; the growth rate in solid solder is only about 10 -4 mum/min. The difference is not resulting from factors of thermodynamics, which is the change of Gibbs free energy before and after intermetallic compound formation, but from kinetic factors, which is the rate of change of Gibbs free energy. Even though the difference in growth rate between eutectic SnPb and Pb-free solders during solid state aging was found, the reason behind such difference shown is unclear. The orientation and stress levels of whiskers are measured by white X-ray of synchrotron radiation. The growth direction is nearly parallel to one of the principal axes of tin. The compressive stress level is quite low because the residual stress is relaxed by the whisker growth.

Study of Electromigration-Induced Failures on Cu Pillar Bumps Joined to OSP and ENEPIG Substrates

NASA Astrophysics Data System (ADS)

Hsiao, Yu-Hsiang; Lin, Kwang-Lung; Lee, Chiu-Wen; Shao, Yu-Hsiu; Lai, Yi-Shao

2012-12-01

This work studies electromigration (EM)-induced failures on Cu pillar bumps joined to organic solderability preservative (OSP) on Cu substrates (OSP-bumps) and electroless Ni(P)/electroless Pd/immersion Au (ENEPIG) under bump metallurgy (UBM) on Cu substrates (ENEPIG-bumps). Two failure modes (Cu pad consumption and gap formation) were found with OSP-bumps, but only one failure mode (gap formation) was found with ENEPIG-bumps. The main interfacial compound layer was the Cu6Sn5 compound, which suffered significant EM-induced dissolution, eventually resulting in severe Cu pad consumption at the cathode side for OSP-bumps. A (Cu,Ni)6Sn5 layer with strong resistance to EM-induced dissolution exists at the joint interface when a nickel barrier layer is incorporated at the cathode side (Ni or ENEPIG), and these imbalanced atomic fluxes result in the voids and gap formation. OSP-bumps showed better lifetime results than ENEPIG-bumps for several current stressing conditions. The inverse Cu atomic flux ( J Cu,chem) which diffuses from the Cu pad to cathode side retards the formation of voids. The driving force for J Cu,chem comes from the difference in chemical potential between the (Cu,Ni)6Sn5 and Cu6Sn5 phases.

Two-Dimensional Porous Electrode Model for Capacitive Deionization

DOE PAGES

Hemmatifar, Ali; Stadermann, Michael; Santiago, Juan G.

2015-10-28

Here, ion transport in porous conductive materials is of great importance in a variety of electrochemical systems including batteries and supercapacitors. We here analyze the coupling of flow and charge transport and charge capacitance in capacitive deionization (CDI). In CDI, a pair of porous carbon electrodes is employed to electrostatically retain and remove ionic species from aqueous solutions. We here develop and solve a novel unsteady two-dimensional model for capturing the ion adsorption/desorption dynamics in a flow-between CDI system. We use this model to study the complex, nonlinear coupling between electromigration, diffusion, and advection of ions. We also fabricated amore » laboratory-scale CDI cell which we use to measure the near-equilibrium, cumulative adsorbed salt, and electric charge as a function of applied external voltage. We use these integral measures to validate and calibrate this model. We further present a detailed computational study of the spatiotemporal adsorption/desorption dynamics under constant voltage and constant flow conditions. We show results for low (20 mM KCl) and relatively high (200 mM KCl) inlet ion concentrations and identify effects of ion starvation on desalination. We show that in both cases electromigrative transport eventually becomes negligible and diffusive ion transport reduces the desalination rate.« less

A study of electromigration behaviors of Ge2Sb2Te5 chalcogenide nano-strips subjected to pulse bias

NASA Astrophysics Data System (ADS)

Huang, Yin-Hsien; Hsieh, Tsung-Eong

2017-07-01

Electromigration (EM) behaviors of pristine Ge2Sb2Te5 (GST) and cerium-doped GST (Ce-GST) nano-strips were investigated by the mean-time-to-failure (MTTF) tests under the pulse bias at the conditions of pulse frequency (f) ranging from 1 to 25 MHz and duty cycle ranging from 50% to 80%. Analytical results indicated that, at f greater than 10 MHz, the EM failure of GST nano-strips in pulse bias environment could be depicted by the ‘average current model’. With the aid of Black’s theory, the activation energies (E a) of EM process under pulse bias were found to be 0.63 and 0.56 eV for GST and Ce-GST nano-strips, respectively. The E a values were comparatively smaller than those observed in direct-current MTTF test of GST thin-film samples, implying the enhancement of surface diffusion and skin effect in GST nano-strips. The morphology and composition analyses indicated that the electrostatic and the electron-wind forces might simultaneously involve in the mass transport in GST nano-strips under the test conditions of this study. The composition analysis also revealed that doping could not effectively alleviate the element segregation in GST subjected to electrical bias.

[Diffusion and diffusion-osmosis models of the charged macromolecule transfer in barriers of biosystems].

PubMed

Varakin, A I; Mazur, V V; Arkhipova, N V; Serianov, Iu V

2009-01-01

Mathematical models of the transfer of charged macromolecules have been constructed on the basis of the classical equations of electromigration diffusion of Helmholtz-Smolukhovskii, Goldman, and Goldman-Hodgkin-Katz. It was shown that ion transfer in placental (mimicking lipid-protein barriers) and muscle barriers occurs by different mechanisms. In placental barriers, the electromigration diffusion occurs along lipid-protein channels formed due to the conformational deformation of phospholipid and protein molecules with the coefficients of diffusion D = (2.6-3.6) x 10(-8) cm2/s. The transfer in muscle barriers is due to the migration across charged interfibrillar channels with the negative diffusion activation energy, which is explained by changes in the structure of muscle fibers and expenditures of thermal energy for the extrusion of Cl- from channel walls with the diffusion coefficient D = (6.0-10.0) x 10(-6) cm2/s.

A general strategy for the ultrafast surface modification of metals

PubMed Central

Shen, Mingli; Zhu, Shenglong; Wang, Fuhui

2016-01-01

Surface modification is an essential step in engineering materials that can withstand the increasingly aggressive environments encountered in various modern energy-conversion systems and chemical processing industries. However, most traditional technologies exhibit disadvantages such as slow diffusion kinetics, processing difficulties or compatibility issues. Here, we present a general strategy for the ultrafast surface modification of metals inspired by electromigration, using aluminizing austenitic stainless steel as an example. Our strategy facilitates the rapid formation of a favourable ductile surface layer composed of FeCrAl or β-FeAl within only 10 min compared with several hours in conventional processes. This result indicates that electromigration can be used to achieve the ultrafast surface modification of metals and can overcome the limitations of traditional technologies. This strategy could be used to aluminize ultra-supercritical steam tubing to withstand aggressive oxidizing environments. PMID:27924909

Buried structure for increasing fabrication performance of micromaterial by electromigration

NASA Astrophysics Data System (ADS)

Kimura, Yasuhiro; Saka, Masumi

2016-06-01

The electromigration (EM) technique is a physical synthetic growth method for micro/nanomaterials. EM causes atomic diffusion in a metal line by high-density electron flows. The intentional control of accumulation and relaxation of atoms by EM can lead to the fabrication of a micro/nanomaterial. TiN passivation has been utilized as a component of sample in the EM technique. Although TiN passivation can simplify the cumbersome processes for preparing the sample, the leakage of current naturally occurs because of the conductivity of TiN as a side effect and decreases the performance of micro/nanomaterial fabrication. In the present work, we propose a buried structure, which contributes to significantly decreasing the current for fabricating an Al micromaterial by confining the current flow in the EM technique. The fabrication performance was evaluated based on the threshold current for fabricating an Al micromaterial using the buried structure and the previous structure with the leakage of current.

Microwave evaluation of electromigration susceptibility in advanced interconnects.

PubMed

Sunday, Christopher E; Veksler, Dmitry; Cheung, Kin C; Obeng, Yaw S

2017-11-07

Traditional metrology has been unable to adequately address the needs of the emerging integrated circuits (ICs) at the nano scale; thus, new metrology and techniques are needed. For example, the reliability challenges in fabrication need to be well understood and controlled to facilitate mass production of through-substrate-via (TSV) enabled three-dimensional integrated circuits (3D-ICs). This requires new approaches to the metrology. In this paper, we use the microwave propagation characteristics to study the reliability issues that precede the physical damage caused by electromigration in the Cu-filled TSVs. The pre-failure microwave insertion losses and group delay are dependent on both the device temperature and the amount of current forced through the devices-under-test. The microwave insertion losses increase with the increase in the test temperature, while the group delay increases with the increase in the forced direct current magnitude. The microwave insertion losses are attributed to the defect mobility at the Cu-TiN interface, and the group delay changes are due to resistive heating in the interconnects, which perturbs the dielectric properties of the cladding dielectrics of the copper fill in the TSVs. https://doi.org/10.1063/1.4992135.

Optimization of the nanotwin-induced zigzag surface of copper by electromigration

NASA Astrophysics Data System (ADS)

Chen, Hsin-Ping; Huang, Chun-Wei; Wang, Chun-Wen; Wu, Wen-Wei; Liao, Chien-Neng; Chen, Lih-Juann; Tu, King-Ning

2016-01-01

By adding nanotwins to Cu, the surface electromigration (EM) slows down. The atomic mobility of the surface step-edges is retarded by the triple points where a twin meets a free surface to form a zigzag-type surface. We observed that EM can alter the zigzag surface structure to optimize the reduction of EM, according to Le Chatelier's principle. Statistically, the optimal alternation is to change an arbitrary (111)/(hkl) zigzag pair to a pair having a very low index (hkl) plane, especially the (200) plane. Using in situ ultrahigh vacuum and high-resolution transmission electron microscopy, we examined the effects of different zigzag surfaces on the rate of EM. The calculated rate of surface EM can be decreased by a factor of ten.By adding nanotwins to Cu, the surface electromigration (EM) slows down. The atomic mobility of the surface step-edges is retarded by the triple points where a twin meets a free surface to form a zigzag-type surface. We observed that EM can alter the zigzag surface structure to optimize the reduction of EM, according to Le Chatelier's principle. Statistically, the optimal alternation is to change an arbitrary (111)/(hkl) zigzag pair to a pair having a very low index (hkl) plane, especially the (200) plane. Using in situ ultrahigh vacuum and high-resolution transmission electron microscopy, we examined the effects of different zigzag surfaces on the rate of EM. The calculated rate of surface EM can be decreased by a factor of ten. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr05418d

Evidence for oxygen vacancy or ferroelectric polarization induced switchable diode and photovoltaic effects in BiFeO3 based thin films.

PubMed

Guo, Yiping; Guo, Bing; Dong, Wen; Li, Hua; Liu, Hezhou

2013-07-12

The diode and photovoltaic effects of BiFeO3 and Bi0.9Sr0.1FeO(3-δ) polycrystalline thin films were investigated by poling the films with increased magnitude and alternating direction. It was found that both electromigration of oxygen vacancies and polarization flipping are able to induce switchable diode and photovoltaic effects. For the Bi0.9Sr0.1FeO(3-δ) thin films with high oxygen vacancy concentration, reversibly switchable diode and photovoltaic effects can be observed due to the electromigration of oxygen vacancies under an electric field much lower than its coercive field. However, for the pure BiFeO3 thin films with lower oxygen vacancy concentration, the reversibly switchable diode and photovoltaic effect is hard to detect until the occurrence of polarization flipping. The switchable diode and photovoltaic effects can be explained well using the concepts of Schottky-like barrier-to-Ohmic contacts resulting from the combination of oxygen vacancies and polarization. The sign of photocurrent could be independent of the direction of polarization when the modulation of the energy band induced by oxygen vacancies is large enough to offset that induced by polarization. The photovoltaic effect induced by the electromigration of oxygen vacancies is unstable due to the diffusion of oxygen vacancies or the recombination of oxygen vacancies with hopping electrons. Our work provides deep insights into the nature of diode and photovoltaic effects in ferroelectric films, and will facilitate the advanced design of switchable devices combining spintronic, electronic, and optical functionalities.

Phase nucleation and evolution mechanisms in heterogeneous solids

NASA Astrophysics Data System (ADS)

Udupa, Anirudh

Phase nucleation and evolution is a problem of critical importance in many applications. As the length scales are reduced, it becomes increasingly important to consider interfacial and micro-structural effects that can be safely ignored at larger length scales owing to randomness. The theory of phase nucleation has been addressed usually by the classical nucleation theory, which was originally derived for single component fluid systems, after making an assumption of equilibrium. The criterion has not been rigorously derived for solids, which are far from equilibrium due to dissipation by multiple physical drivers. In this thesis, a thermodynamically sound nucleation criterion is derived for systems with multiple interacting physical phenomena and multiple dissipating mechanisms. This is done, using the tools of continuum mechanics, by determining the change in free energy upon the introduction of a new nucleus into the system. The developed theory is demonstrated to be a generalization of the classical nucleation theory (CNT). The developed theory is then applied to the problem of electromigration driven void nucleation, a serious reliability concern for the microelectronics industry. The void grows and eventually severs the line making the chip nonfunctional. There are two classes of theories at present in the electromigration literature to address the problem of void nucleation, the vacancy supersaturation theory and the entropic dissipation theory, both of which are empirical and based on intuition developed from experimental observations. When the developed theory was applied to the problem of electromigration, it was found to be consistent with the vacancy supersaturation theory, but provided the correct energetic quantity, the chemical potential, which has contribution from both the vacancy concentration as well as the hydrostatic stress. An experiment, consisting of electromigration tests on serpentine lines, was developed to validate the developed nucleation theory. The experimental results are consistent with the developed theory and show that the theory of entropic dissipation is incorrect. A diffuse-interface computational technique was then developed to simulate the problem of electromigration driven void nucleation and growth in arbitrary geometries. Experimentally known results such as Black's law, existence of the Blech length, effect of interface adhesion energy were reproduced. The simulations were also used to infer the numerical value of the nucleation criterion, based on experimental results in the literature. The problem of electromigration is the result of species diffusion due to imparted momentum from the electrons, and the resulting motion of interface is influenced by surface diffusion along the interface, bulk diffusion, and the current density. Similarly, the formation of intermetallic compounds (IMC) and the resulting interface shape in many systems is the result of limiting effects of bulk diffusion, interfacial reaction, surface energy, and surface diffusion. Thus, the dynamics and stability of the interface formed when Cu and Sn react to form the IMC compound Cu6Sn5 is explored next. This system is of significant relevance to modern microelectronic chip assemblies, where solder joints with significant Cu6Sn5 volume fraction are known to be prone to brittle fracture and shorter useful life. Prior experimental observations have shown the interface to possess either a scalloped, flat or needle shaped morphology. The governing mechanism leading to the observed shape of the interface is not clearly known, and is the focus of the present study. In research unrelated to diffusion driven phase evolution, but involving interfaces nevertheless, in the appendix, the problem of interfacial delamination in Through Silicon Vias (TSV) is studied analytically. Three-dimensional (3D) packages utilizing TSVs are seen as enablers of increased performance and "More than Moore" functionality at the present time. However, the use of TSVs introduce a set of reliability concerns, one of which is the thermo-mechanical stress caused by the mismatch in coefficient of thermal expansion (CTE) between the copper via and the surround- ing silicon. The CTE mismatch, causes high stress zones in and around the copper TSVs, which in turn impede the mobility of electrons in the regions surrounding the TSVs. Further, proximal placing of TSVs for improved electrical performance may be restricted by additional stress induced by TSV-TSV interaction. The increased stress of the region surrounding the TSV also increases the risk of interfacial delamination. In order to ensure reliable functioning of 3D chip stacks, design guidelines are necessary on the excluded "keep-out" zone where stress induced by TSVs will impede transistor functionality. Towards this end, we analytically derive, using elasticity theory, the stress field in and around a doubly periodic arrangement of TSVs subjected to a uniform thermal excursion. The model for stress is used to analytically estimate the conditions for interfacial cracks to propagate, as a function of the system geometry and material properties. (Abstract shortened by ProQuest.).

Failure mechanism of THz GaAs photoconductive antenna

NASA Astrophysics Data System (ADS)

Qadri, Syed B.; Wu, Dong H.; Graber, Benjamin D.; Mahadik, Nadeemullah A.; Garzarella, Anthony

2012-07-01

We investigated the failure mechanism of THz GaAs photoconductive antenna using high resolution x-ray diffraction topography. From these studies, it was found that grain boundaries are formed during the high frequency device operation. This results in the segregation of gold at the boundaries causing electromigration of the metal between the gold micro-strips. This disrupts the photocurrents from being produced by femtosecond laser thus preventing terahertz beam generation from the photoconductive antennae leading to device failure.

Mean-time-to-failure study of flip chip solder joints on Cu/Ni(V)/Al thin-film under-bump-metallization

NASA Astrophysics Data System (ADS)

Choi, W. J.; Yeh, E. C. C.; Tu, K. N.

2003-11-01

Electromigration of eutectic SnPb flip chip solder joints and their mean-time-to-failure (MTTF) have been studied in the temperature range of 100 to 140 °C with current densities of 1.9 to 2.75×104 A/cm2. In these joints, the under-bump-metallization (UBM) on the chip side is a multilayer thin film of Al/Ni(V)/Cu, and the metallic bond-pad on the substrate side is a very thick, electroless Ni layer covered with 30 nm of Au. When stressed at the higher current densities, the MTTF was found to decrease much faster than what is expected from the published Black's equation. The failure occurred by interfacial void propagation at the cathode side, and it is due to current crowding near the contact interface between the solder bump and the thin-film UBM. The current crowding is confirmed by a simulation of current distribution in the solder joint. Besides the interfacial void formation, the intermetallic compounds formed on the UBM as well as the Ni(V) film in the UBM have been found to dissolve completely into the solder bump during electromigration. Therefore, the electromigation failure is a combination of the interfacial void formation and the loss of UBM. Similar findings in eutectic SnAgCu flip chip solder joints have also been obtained and compared.

The Effect of Sn Orientation on Intermetallic Compound Growth in Idealized Sn-Cu-Ag Interconnects

NASA Astrophysics Data System (ADS)

Kinney, Chris; Linares, Xioranny; Lee, Kyu-Oh; Morris, J. W.

2013-04-01

The work reported here explores the influence of crystal orientation on the growth of the interfacial intermetallic layer during electromigration in Cu||Sn||Cu solder joints. The samples were thin, planar Sn-Ag-Cu (SAC) solder layers between Cu bars subject to a uniaxial current. Electron backscatter diffraction (EBSD) was used to characterize the microstructure before and after testing. The most useful representation of the EBSD data identifies the Sn grain orientation by the angle between the Sn c-axis and the current direction. The tested samples included single-crystal joints with c-axis nearly parallel to the current ("green" samples) and with c-axis perpendicular to the current ("red" samples). At current density of 104 A/cm2 (steady-state temperature of ~150°C), an intermetallic layer grew at an observable rate in the "green" samples, but not in the "red" ones. A current density of 1.15 × 104 A/cm2 (temperature ~160°C) led to measurable intermetallic growth in both samples. The growth fronts were nearly planar and the growth rates constant (after an initial incubation period); the growth rates in the "green" samples were about 10× those in the "red" samples. The Cu concentrations were constant within the joints, showing that the intermetallic growth is dominated by the electromigration flux. The measured growth rates and literature values for the diffusion of Cu in Sn were used to extract values for the effective charge, z *, that governs the electromigration of Cu. The calculated value of z * is significantly larger for current perpendicular to the c-axis than along it.

Nanopipettes for Metal Transport

NASA Astrophysics Data System (ADS)

Svensson, K.; Olin, H.; Olsson, E.

2004-09-01

Here we demonstrate, for the first time experimentally, a nanopipette action for metals using multiwalled carbon nanotubes. The process relies on electromigration forces, created at high electron current densities, enabling the transport of material inside the hollow core of carbon nanotubes. In this way nanoparticles of iron were transported to and from electrically conducting substrates.

Nanopipettes for metal transport.

PubMed

Svensson, K; Olin, H; Olsson, E

2004-10-01

Here we demonstrate, for the first time experimentally, a nanopipette action for metals using multiwalled carbon nanotubes. The process relies on electromigration forces, created at high electron current densities, enabling the transport of material inside the hollow core of carbon nanotubes. In this way nanoparticles of iron were transported to and from electrically conducting substrates.

Electromigration of intergranular voids in metal films for microelectronic interconnects

NASA Astrophysics Data System (ADS)

Averbuch, Amir; Israeli, Moshe; Ravve, Igor

2003-04-01

Voids and cracks often occur in the interconnect lines of microelectronic devices. They increase the resistance of the circuits and may even lead to a fatal failure. Voids may occur inside a single grain, but often they appear on the boundary between two grains. In this work, we model and analyze numerically the migration and evolution of an intergranular void subjected to surface diffusion forces and external voltage applied to the interconnect. The grain-void interface is considered one-dimensional, and the physical formulation of the electromigration and diffusion model results in two coupled fourth-order one-dimensional time-dependent PDEs. The boundary conditions are specified at the triple points, which are common to both neighboring grains and the void. The solution of these equations uses a finite difference scheme in space and a Runge-Kutta integration scheme in time, and is also coupled to the solution of a static Laplace equation describing the voltage distribution throughout the grain. Since the voltage distribution is required only along the interface line, the two-dimensional discretization of the grain interior is not needed, and the static problem is solved by the boundary element method at each time step. The motion of the intergranular void was studied for different ratios between the diffusion and the electric field forces, and for different initial configurations of the void.

In situ removal of copper from sediments by a galvanic cell.

PubMed

Yuan, Songhu; Wu, Chan; Wan, Jinzhong; Lu, Xiaohua

2009-01-01

This study dealt with in situ removal of copper from sediments through an electrokinetic (EK) process driven by a galvanic cell. Iron (Fe) and carbon (C) were placed separately and connected with a conductive wire. Polluted sediments were put between them and water was filled above the sediments. The galvanic cell was thus formed due to the different electrode potentials of Fe and C. The cell could remove the pollutants in the sediments by electromigration and/or electroosmosis. Results showed that a weak voltage less than 1V was formed by the galvanic cell. The voltage decreased with the increase of time. A slight increase of sediment pH from the anode (Fe) to the cathode (C) was observed. The presence of supernatant water inhibited the variation of sediment pH because H(+) and OH(-) could diffuse into the water. The removal of copper was affected by the sediment pH and the distribution of electrolyte in sediment and supernatant water. Lower pH led to higher removal efficiency. More electrolyte in the sediment and/or less electrolyte in the supernatant water favored the removal of copper. The major removal mechanism was proposed on the basis of the desorption of copper from sediment to pore solution and the subsequent electromigration of copper from the anode to the cathode. The diffusion of copper from sediment to supernatant water was negligible.

Nanogap structures for molecular nanoelectronics.

PubMed

Motto, Paolo; Dimonte, Alice; Rattalino, Ismael; Demarchi, Danilo; Piccinini, Gianluca; Civera, Pierluigi

2012-02-09

This study is focused on the realization of nanodevices for nano and molecular electronics, based on molecular interactions in a metal-molecule-metal (M-M-M) structure. In an M-M-M system, the electronic function is a property of the structure and can be characterized through I/V measurements. The contact between the metals and the molecule was obtained by gold nanogaps (with a dimension of less than 10 nm), produced with the electromigration technique. The nanogap fabrication was controlled by a custom hardware and the related software system. The studies were carried out through experiments and simulations of organic molecules, in particular oligothiophenes.

Thermal-Interaction Matrix For Resistive Test Structure

NASA Technical Reports Server (NTRS)

Buehler, Martin G.; Dhiman, Jaipal K.; Zamani, Nasser

1990-01-01

Linear mathematical model predicts increase in temperature in each segment of 15-segment resistive structure used to test electromigration. Assumption of linearity based on fact: equations that govern flow of heat are linear and coefficients in equations (heat conductivities and capacities) depend only weakly on temperature and considered constant over limited range of temperature.

Fabrication of back-contacted silicon solar cells using thermomigration to create conductive vias

DOEpatents

Gee, James M; Schmit, Russell R.

2007-01-30

Methods of manufacturing back-contacted silicon solar cells fabricated using a gradient-driven solute transport process, such as thermomigration or electromigration, to create n-type conductive vias connecting the n-type emitter layer on the front side to n-type ohmic contacts located on the back side.

Electromigration and Thermomechanical Fatigue Behavior of Sn0.3Ag0.7Cu Solder Joints

NASA Astrophysics Data System (ADS)

Zuo, Yong; Bieler, Thomas R.; Zhou, Quan; Ma, Limin; Guo, Fu

2017-12-01

The anisotropy of Sn crystal structures greatly affects the electromigration (EM) and thermomechanical fatigue (TMF) of solder joints. The size of solder joint shrinkage in electronic systems further makes EM and TMF an inseparably coupled issue. To obtain a better understanding of failure under combined moderately high (2000 A/cm2) current density and 10-150°C/1 h thermal cycling, analysis of separate, sequential, and concurrent EM and thermal cycling (TC) was imposed on single shear lap joints, and the microstructure and crystal orientations were incrementally characterized using electron backscatter diffraction (EBSD) mapping. First, it was determined that EM did not significantly change the crystal orientation, but the formation of Cu6Sn5 depended on the crystal orientation, and this degraded subsequent TMF behavior. Secondly, TC causes changes in crystal orientation. Concurrent EM and TC led to significant changes in crystal orientation by discontinuous recrystallization, which is facilitated by Cu6Sn5 particle formation. The newly formed Cu6Sn5 often showed its c-axis close to the direction of electron flow.

Electromigration and morphological changes in Ag nanostructures

NASA Astrophysics Data System (ADS)

Chatterjee, A.; Bai, T.; Edler, F.; Tegenkamp, C.; Weide-Zaage, K.; Pfnür, H.

2018-02-01

Electromigration (EM) as a structuring tool was investigated in Ag nanowires (width 300 nm, thickness 25 nm) and partly in notched and bow-tie Ag structures on a Si(1 0 0) substrate in ultra-high vacuum using a four-tip scanning tunneling microscope in combination with a scanning electron microscope. From simulations of Ag nanowires we got estimates of temperature profiles, current density profiles, EM and thermal migration (TM) mass flux distributions within the nanowire induced by critical current densities of 108 A cm-2. At room temperature, the electron wind force at these current densities by far dominates over thermal diffusion, and is responsible for formation of voids at the cathode and hillocks at the anode side. For current densities that exceed the critical current densities necessary for EM, a new type of wire-like structure formation was found both at room temperature and at 100 K for notched and bow-tie structures. This suggests that the simultaneous action of EM and TM is structure forming, but with a very small influence of TM at low temperature.

Electromigration resistance in a short three-contact interconnect tree

NASA Astrophysics Data System (ADS)

Chang, C. W.; Choi, Z.-S.; Thompson, C. V.; Gan, C. L.; Pey, K. L.; Choi, W. K.; Hwang, N.

2006-05-01

Electromigration has been characterized in via-terminated interconnect lines with additional vias in the middle, creating two adjacent segments that can be stressed independently. The mortality of a segment was found to depend on the direction and magnitude of the current in the adjacent segment, confirming that there is not a fixed value of the product of the current density and segment length, jL, that defines immortality in individual segments that are part of a multisegment interconnect tree. Instead, it is found that the probability of failure of a multisegment tree increases with the increasing value of an effective jL product defined in earlier work. However, contrary to expectations, the failures were still observed when (jL)eff was less than the critical jL product for which lines were found to be immortal in single-segment test structures. It is argued that this is due to reservoir effects associated with unstressed segments or due to liner failure at the central via. Multisegment test structures are therefore shown to reveal more types of failure mechanisms and mortality conditions that are not found in tests with single-segment structures.

Non-equilibrium Transport in Carbon based Adsorbate Systems

NASA Astrophysics Data System (ADS)

Fürst, Joachim; Brandbyge, Mads; Stokbro, Kurt; Jauho, Antti-Pekka

2007-03-01

We have used the Atomistix Tool Kit(ATK) and TranSIESTA[1] packages to investigate adsorption of iron atoms on a graphene sheet. The technique of both codes is based on density functional theory using local basis sets[2], and non-equilibrium Green's functions (NEGF) to calculate the charge distribution under external bias. Spin dependent electronic structure calculations are performed for different iron coverages. These reveal adsorption site dependent charge transfer from iron to graphene leading to screening effects. Transport calculations show spin dependent scattering of the transmission which is analysed obtaining the transmission eigenchannels for each spin type. The phenomena of electromigration of iron in these systems at finite bias will be discussed, estimating the so-called wind force from the reflection[3]. [1] M. Brandbyge, J.-L. Mozos, P. Ordejon, J. Taylor, and K. Stokbro. Physical Review B (Condensed Matter and Materials Physics), 65(16):165401/11-7, 2002. [2] Jose M. Soler, Emilio Artacho, Julian D. Gale, Alberto Garcia, Javier Junquera, Pablo Ordejon, and Daniel Sanchez-Portal. Journal of Physics Condensed Matter, 14(11):2745-2779, 2002. [3] Sorbello. Theory of electromigration. Solid State Physics, 1997.

Electromigration and Thermomechanical Fatigue Behavior of Sn0.3Ag0.7Cu Solder Joints

NASA Astrophysics Data System (ADS)

Zuo, Yong; Bieler, Thomas R.; Zhou, Quan; Ma, Limin; Guo, Fu

2018-03-01

The anisotropy of Sn crystal structures greatly affects the electromigration (EM) and thermomechanical fatigue (TMF) of solder joints. The size of solder joint shrinkage in electronic systems further makes EM and TMF an inseparably coupled issue. To obtain a better understanding of failure under combined moderately high (2000 A/cm2) current density and 10-150°C/1 h thermal cycling, analysis of separate, sequential, and concurrent EM and thermal cycling (TC) was imposed on single shear lap joints, and the microstructure and crystal orientations were incrementally characterized using electron backscatter diffraction (EBSD) mapping. First, it was determined that EM did not significantly change the crystal orientation, but the formation of Cu6Sn5 depended on the crystal orientation, and this degraded subsequent TMF behavior. Secondly, TC causes changes in crystal orientation. Concurrent EM and TC led to significant changes in crystal orientation by discontinuous recrystallization, which is facilitated by Cu6Sn5 particle formation. The newly formed Cu6Sn5 often showed its c-axis close to the direction of electron flow.

Modeling and Studying the Effect of Texture and Elastic Anisotropy of Copper Microstructure in Nanoscale Interconnects on Reliability in Integrated Circuits

NASA Astrophysics Data System (ADS)

Basavalingappa, Adarsh

Copper interconnects are typically polycrystalline and follow a lognormal grain size distribution. Polycrystalline copper interconnect microstructures with a lognormal grain size distribution were obtained with a Voronoi tessellation approach. The interconnect structures thus obtained were used to study grain growth mechanisms, grain boundary scattering, scattering dependent resistance of interconnects, stress evolution, vacancy migration, reliability life times, impact of orientation dependent anisotropy on various mechanisms, etc. In this work, the microstructures were used to study the impact of microstructure and elastic anisotropy of copper on thermal and electromigration induced failure. A test structure with copper and bulk moduli values was modeled to do a comparative study with the test structures with textured microstructure and elastic anisotropy. By subjecting the modeled test structure to a thermal stress by ramping temperature down from 400 °C to 100 °C, a significant variation in normal stresses and pressure were observed at the grain boundaries. This variation in normal stresses and hydrostatic stresses at the grain boundaries was found to be dependent on the orientation, dimensions, surroundings, and location of the grains. This may introduce new weak points within the metal line where normal stresses can be very high depending on the orientation of the grains leading to delamination and accumulation sites for vacancies. Further, the hydrostatic stress gradients act as a driving force for vacancy migration. The normal stresses can exceed certain grain orientation dependent critical threshold values and induce delamination at the copper and cap material interface, thereby leading to void nucleation and growth. Modeled test structures were subjected to a series of copper depositions at 250 °C followed by copper etch at 25 °C to obtain initial stress conditions. Then the modeled test structures were subjected to 100,000 hours ( 11.4 years) of simulated thermal stress at an elevated temperature of 150 °C. Vacancy migration due to concentration gradients, thermal gradients, and mechanical stress gradients were considered under the applied thermal stress. As a result, relatively high concentrations of vacancies were observed in the test structure due to a driving force caused by the pressure gradients resulting from the elastic anisotropy of copper. The grain growth mechanism was not considered in these simulations. Studies with two grain analysis demonstrated that the stress gradients developed will be severe when (100) grains are adjacent to (111) grains, therefore making them the weak points for potentially reliability failures. Ilan Blech discovered that electromigration occurs above a critical product of the current density and metal length, commonly referred as Blech condition. Electromigration stress simulations in this work were carried out by subjecting test structures to scaled current densities to overcome the Blech condition of (jL)crit for small dimensions of test structure and the low temperature stress condition used. Vacancy migration under the electromigration stress conditions was considered along with the vacancy migration induced stress evolution. A simple void growth model was used which assumes voids start to form when vacancies reach a critical level. Increase of vacancies in a localized region increases the resistance of the metal line. Considering a 10% increase in resistance as a failure criterion, the distributions of failure times were obtained for given electromigration stress conditions. Bimodal/multimodal failure distributions were obtained as a result. The sigma values were slightly lower than the ones commonly observed from experiments. The anisotropy of the elastic moduli of copper leads to the development of significantly different stress values which are dependent on the orientation of the grains. This results in some grains having higher normal stress than the others. This grain orientation dependent normal stress can reach a critical stress necessary to induce delamination at the copper and cap interface. Time taken to reach critical stress was considered as time to fail and distributions of failure times were obtained for structures with different grain orientations in the microstructure for different critical stress values. The sigma values of the failure distributions thus obtained for different constant critical stress values had a strong dependence of on the critical stress. It is therefore critical to use the appropriate critical stress value for the delamination of copper and cap interface. The critical stress necessary to overcome the local adhesion of the copper and the cap material interface is dependent on grain orientation of the copper. Simulations were carried out by considering grain orientation dependent critical normal stress values as failure criteria. The sigma value thus obtained with selected critical stress values were comparable to sigma values commonly observed from experiments.

Single-step enantioselective amino acid flux analysis by capillary electrophoresis using on-line sample preconcentration with chemical derivatization.

PubMed

Ptolemy, Adam S; Tran, Lara; Britz-McKibbin, Philip

2006-07-15

Capillary electrophoresis (CE) represents a versatile platform for integrating sample pretreatment with chemical analysis because of its ability to tune analyte electromigration and band dispersion properties in discontinuous electrolyte systems. In this article, a single-step method that combines on-line sample preconcentration with in-capillary chemical derivatization is developed for rapid, sensitive, and enantioselective analysis of micromolar levels of amino acids that lack intrinsic chromophores by CE with UV detection. Time-resolved electrophoretic studies revealed two distinct stages of amino acid band narrowing within the original long sample injection plug occurring both prior to and after in-capillary labeling via zone passing by ortho-phthalaldehyde/N-acetyl l-cysteine (OPA/NAC). This technique enabled direct analysis of d-amino acids in a 95% enantiomeric excess mixture with sub-micromolar detection limits and minimal sample handling, where the capillary functions as a preconcentrator, microreactor, and chiral selector. On-line sample preconcentration with chemical derivatization CE (SPCD-CE) was applied to study the enantioselective amino acid flux in Escherichia coli bacteria cultures, which demonstrated a unique l-Ala efflux into the extracellular medium. New strategies for high-throughput analyses of low-abundance metabolites are important for understanding fundamental physiological processes in bacteria required for screening the efficacy of new classes of antibiotics as well as altered metabolism in genetically modified mutant strains.

Changes in electrical and thermal parameters of led packages under different current and heating stresses

NASA Astrophysics Data System (ADS)

Jayawardena, Adikaramge Asiri

The goal of this dissertation is to identify electrical and thermal parameters of an LED package that can be used to predict catastrophic failure real-time in an application. Through an experimental study the series electrical resistance and thermal resistance were identified as good indicators of contact failure of LED packages. This study investigated the long-term changes in series electrical resistance and thermal resistance of LED packages at three different current and junction temperature stress conditions. Experiment results showed that the series electrical resistance went through four phases of change; including periods of latency, rapid increase, saturation, and finally a sharp decline just before failure. Formation of voids in the contact metallization was identified as the underlying mechanism for series resistance increase. The rate of series resistance change was linked to void growth using the theory of electromigration. The rate of increase of series resistance is dependent on temperature and current density. The results indicate that void growth occurred in the cap (Au) layer, was constrained by the contact metal (Ni) layer, preventing open circuit failure of contact metal layer. Short circuit failure occurred due to electromigration induced metal diffusion along dislocations in GaN. The increase in ideality factor, and reverse leakage current with time provided further evidence to presence of metal in the semiconductor. An empirical model was derived for estimation of LED package failure time due to metal diffusion. The model is based on the experimental results and theories of electromigration and diffusion. Furthermore, the experimental results showed that the thermal resistance of LED packages increased with aging time. A relationship between thermal resistance change rate, with case temperature and temperature gradient within the LED package was developed. The results showed that dislocation creep is responsible for creep induced plastic deformation in the die-attach solder. The temperatures inside the LED package reached the melting point of die-attach solder due to delamination just before catastrophic open circuit failure. A combined model that could estimate life of LED packages based on catastrophic failure of thermal and electrical contacts is presented for the first time. This model can be used to make a-priori or real-time estimation of LED package life based on catastrophic failure. Finally, to illustrate the usefulness of the findings from this thesis, two different implementations of real-time life prediction using prognostics and health monitoring techniques are discussed.

Nanogap structures for molecular nanoelectronics

PubMed Central

2012-01-01

This study is focused on the realization of nanodevices for nano and molecular electronics, based on molecular interactions in a metal-molecule-metal (M-M-M) structure. In an M-M-M system, the electronic function is a property of the structure and can be characterized through I/V measurements. The contact between the metals and the molecule was obtained by gold nanogaps (with a dimension of less than 10 nm), produced with the electromigration technique. The nanogap fabrication was controlled by a custom hardware and the related software system. The studies were carried out through experiments and simulations of organic molecules, in particular oligothiophenes. PMID:22321736

Structural tuning of nanogaps using electromigration induced by field emission current with bipolar biasing

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

Yagi, Mamiko; Ito, Mitsuki; Shirakashi, Jun-ichi, E-mail: shrakash@cc.tuat.ac.jp

We report a new method for fabrication of Ni nanogaps based on electromigration induced by a field emission current. This method is called “activation” and is demonstrated here using a current source with alternately reversing polarities. The activation procedure with alternating current bias, in which the current source polarity alternates between positive and negative bias conditions, is performed with planar Ni nanogaps defined on SiO{sub 2}/Si substrates at room temperature. During negative biasing, a Fowler-Nordheim field emission current flows from the source (cathode) to the drain (anode) electrode. The Ni atoms at the tip of the drain electrode are thusmore » activated and then migrate across the gap from the drain to the source electrode. In contrast, in the positive bias case, the field emission current moves the activated atoms from the source to the drain electrode. These two procedures are repeated until the tunnel resistance of the nanogaps is successively reduced from 100 TΩ to 48 kΩ. Scanning electron microscopy and atomic force microscopy studies showed that the gap separation narrowed from approximately 95 nm to less than 10 nm because of the Ni atoms that accumulated at the tips of both the source and drain electrodes. These results show that the alternately biased activation process, which is a newly proposed atom transfer technique, can successfully control the tunnel resistance of the Ni nanogaps and is a suitable method for formation of ultrasmall nanogap structures.« less

Electromigration-induced void grain-boundary interactions: The mean time to failure for copper interconnects with bamboo and near-bamboo structures

NASA Astrophysics Data System (ADS)

Ogurtani, Tarik Omer; Oren, Ersin Emre

2004-12-01

A well-posed moving boundary-value problem, describing the dynamics of curved interfaces and surfaces associated with voids and/or cracks that are interacting with grain boundaries, is obtained. Extensive computer simulations are performed for void configuration evolution during intergranular motion, under the actions of capillary and electromigration forces in thin-film metallic interconnects with bamboo structures. The analysis of experimental data, utilizing the mean time to failure formulas derived in this paper, gives consistent values for the interface diffusion coefficients and enthalpies of voids. 5.85×10-5exp(-0.95eV/kT)m2s-1 is the value obtained for voids that form in the interior of the copper interconnects avoiding any surface contamination. 1.80×10-4exp(-1.20eV/kT)m2s-1 is obtained for those voids that nucleate either at triple junctions or at the grain-boundary technical surface intersections (grain-boundary groove), where the chemical impurities such as Si, O, S, and even C are segregated during the metallization and annealing processes and may act as trap centers for hopping vacancies.

Electromigration-Induced Surface Drift and Slit Propagation in Polycrystalline Interconnects: Insights from Phase-Field Simulations

NASA Astrophysics Data System (ADS)

Mukherjee, Arnab; Ankit, Kumar; Selzer, Michael; Nestler, Britta

2018-04-01

We employ the phase-field method to assess electromigration (EM) damage in wide polycrystalline interconnects due to grain-boundary grooving. An interplay of surface and grain-boundary diffusion is shown to drastically influence the mode of progressive EM damage. Rapid atomic transport along the surface leads to shape-preserving surface drift reminiscent of Blech drift-velocity experiments. On the other hand, a comparatively faster grain-boundary transport localizes the damage, resulting in the proliferation of intergranular slits with a shape-preserving tip. At steady state, the two regimes exhibit exponents of 1 and 3 /2 , respectively, in Black's law. While surface drift obeys an inverse scaling with grain size, slits exhibit a direct relationship at small sizes, with the dependence becoming weaker at larger ones. Furthermore, we explain the influence of curvature- or EM-mediated healing fluxes running along the surface on groove replenishment. Insights derived from phase-field simulations of EM in bicrystals are extended to investigate the multiphysics of mixed-mode damage of a polycrystalline interconnect line that is characterized by a drift of small grain surfaces, slit propagation, and coarsening. The triple and quadruple junctions are identified as prominent sites of failure.

Electromigration Mechanism of Failure in Flip-Chip Solder Joints Based on Discrete Void Formation.

PubMed

Chang, Yuan-Wei; Cheng, Yin; Helfen, Lukas; Xu, Feng; Tian, Tian; Scheel, Mario; Di Michiel, Marco; Chen, Chih; Tu, King-Ning; Baumbach, Tilo

2017-12-20

In this investigation, SnAgCu and SN100C solders were electromigration (EM) tested, and the 3D laminography imaging technique was employed for in-situ observation of the microstructure evolution during testing. We found that discrete voids nucleate, grow and coalesce along the intermetallic compound/solder interface during EM testing. A systematic analysis yields quantitative information on the number, volume, and growth rate of voids, and the EM parameter of DZ*. We observe that fast intrinsic diffusion in SnAgCu solder causes void growth and coalescence, while in the SN100C solder this coalescence was not significant. To deduce the current density distribution, finite-element models were constructed on the basis of the laminography images. The discrete voids do not change the global current density distribution, but they induce the local current crowding around the voids: this local current crowding enhances the lateral void growth and coalescence. The correlation between the current density and the probability of void formation indicates that a threshold current density exists for the activation of void formation. There is a significant increase in the probability of void formation when the current density exceeds half of the maximum value.

Electromigration in epitaxial Cu(001) lines

NASA Astrophysics Data System (ADS)

Ramanath, G.; Kim, H.; Goindi, H. S.; Frederick, M. J.; Shin, C.-S.; Goswami, R.; Petrov, I.; Greene, J. E.

2002-04-01

We report the electromigration (EM) response of single-domain epitaxial Cu(001) lines on layers of Ta, TaN, and TiN. Epitaxial Cu(001) lines on nitride layers exhibit nearly two orders of magnitude higher mean-time-to-failure (MTTF) values than those on Ta, indicating the strong influence of the underlayer. The activation energy of EM for Cu on the nitrides is ˜0.8-1.2 eV, and that of Cu on Ta is ˜0.2 eV, for 200-300 °C. Our results also indicate that the MTTF values correlate inversely to the crystal quality of the Cu layers measured by X-ray diffraction. The EM resistance of epitaxial Cu lines with different crystal quality on TaN were measured to separate the effects of interface chemistry and crystal quality. While higher quality epitaxial films reveal a higher EM resistance, the magnitude of the change is smaller than that obtained by changing the interface chemistry. Epitaxial lines exhibit more than 3-4 orders of magnitude higher MTTF than polycrystalline lines on the same underlayer. Based upon our results, we propose that the Cu/underlayer interface chemistry and presence of grain boundary diffusion play important roles in unpassivated Cu films.

Theoretical studies in isoelectric focusing. [mathematical modeling and computer simulation for biologicals purification process

NASA Technical Reports Server (NTRS)

Mosher, R. A.; Palusinski, O. A.; Bier, M.

1982-01-01

A mathematical model has been developed which describes the steady state in an isoelectric focusing (IEF) system with ampholytes or monovalent buffers. The model is based on the fundamental equations describing the component dissociation equilibria, mass transport due to diffusion and electromigration, electroneutrality, and the conservation of charge. The validity and usefulness of the model has been confirmed by using it to formulate buffer systems in actual laboratory experiments. The model has been recently extended to include the evolution of transient states not only in IEF but also in other modes of electrophoresis.

Electromigration effect on intermetallic growth and Young's modulus in SAC solder joint

NASA Astrophysics Data System (ADS)

Xu, Luhua; Pang, John H. L.; Ren, Fei; Tu, K. N.

2006-12-01

Solid-state intermetallic compound (IMC) growth behavior plays and important role in solder joint reliability of electronic packaging assemblies. The directional impact of electromigration (EM) on the growth of interfacial IMCs in Ni/SAC/Ni, Cu/SAC/Ni single BGA ball solder joint, and fine pitch ball-grid-array (FPBGA) at the anode and cathode sides is reported in this study. When the solder joint was subjected to a current density of 5,000 A/cm2 at 125°C or 150°C, IMC layer growth on the anode interface was faster than that on the cathode interface, and both were faster than isothermal aging due to the Joule heating effect. The EM affects the IMC growth rate, as well as the composition and mechanical properties. The Young’s modulus and hardness were measured by the nanoindentation continuous stiffness measurement (CSM) from planar IMC surfaces after EM exposure. Different values were observed at the anode and cathode. The energy-dispersive x-ray (EDX) line scan analysis was conducted at the interface from the cathode to anode to study the presence of species; Ni was found in the anode IMC at SAC/Cu in the Ni/SAC/Cu joint, but not detected when the current was reverse. Electron-probe microanalysis (EPMA) measurement on the Ni/SAC/Ni specimen also confirmed the polarized Ni and Cu distributions in cathode and anode IMCs, which were (Ni0.57Cu0.43)3Sn4 and (Cu0.73Ni0.27)6Sn5, respectively. Thus, the Young’s moduli of the IMC are 141 and 175 GPa, respectively.

Electromigration Critical Product to Measure Effect of Underfill Material in Suppressing Bi Segregation in Sn-58Bi Solder

NASA Astrophysics Data System (ADS)

Zhao, Xu; Takaya, Satoshi; Muraoka, Mikio

2017-08-01

Recently, we detected length-dependent electromigration (EM) behavior in Sn-58Bi (SB) solder and revealed the existence of Bi back-flow, which retards EM-induced Bi segregation and is dependent on solder length. The cause of the back-flow is attributed to an oxide layer formed on the SB solder. At present, underfill (UF) material is commonly used in flip-chip packaging as filler between chip and substrate to surround solder bumps. In this study, we quantitatively investigated the effect of UF material as a passivation layer on EM in SB solder strips. EM tests on SB solder strips with length of 50 μm, 100 μm, and 150 μm were conducted simultaneously. Some samples were coated with commercial thermosetting epoxy UF material, which acted as a passivation layer on the Cu-SB-Cu interconnections. The value of the critical product for SB solder was estimated to be 38 A/cm to 43 A/cm at 353 K to 373 K without UF coating and 59 A/cm at 373 K with UF coating. The UF material acting as a passivation layer suppressed EM-induced Bi segregation and increased the threshold current density by 37% to 55%. However, at very high current density, this effect became very slight. In addition, Bi atoms can diffuse to the anode side through the Sn phase, hence addition of microelements to the Sn phase to form obstacles, such as intermetallic compounds, may retard Bi segregation in SB solder.

Effect of surface finish on the failure mechanisms of flip-chip solder joints under electromigration

NASA Astrophysics Data System (ADS)

Lin, Y. L.; Lai, Y. S.; Tsai, C. M.; Kao, C. R.

2006-12-01

Two substrate surface finishes, Au/Ni and organic solderable preservative (OSP), were used to study the effect of the surface finish on the reliability of flip-chip solder joints under electromigration at 150°C ambient temperature. The solder used was eutectic PbSn, and the applied current density was 5×103 A/cm2 at the contact window of the chip. The under bump metallurgy (UBM) on the chip was sputtered Cu/Ni. It was found that the mean-time-to-failure (MTTF) of the OSP joints was six times better than that of the Au/Ni joints (3080 h vs. 500 h). Microstructure examinations uncovered that the combined effect of current crowding and the accompanying local Joule heating accelerated the local Ni UBM consumption near the point of electron entrance. Once Ni was depleted at a certain region, this region became nonconductive, and the flow of the electrons was diverted to the neighboring region. This neighboring region then became the place where electrons entered the joint, and the local Ni UBM consumption was accelerated. This process repeated itself, and the Ni-depleted region extended further on, creating an ever-larger nonconductive region. The solder joint eventually, failed when the nonconductive region became too large, making the effective current density very high. Accordingly, the key factor determining the MTTF was the Ni consumption rate. The joints with the OSP surface finish had a longer MTTF because Cu released from the substrate was able to reduce the Ni consumption rate.

Effects of media stray field on electromigration characteristics in current-perpendicular-to-plane giant magnetoresistance spin-valve read sensors

NASA Astrophysics Data System (ADS)

Gui Zeng, Ding; Lee, Kyoung-il; Chung, Kyung-Won; Bae, Seongtae

2012-05-01

Effects of magnetic stray field retrieved from both longitudinal and perpendicular magnetic recording media (denoted by "media stray field") on electromigration (EM) characteristics of current-perpendicular-to-plane (CPP) giant magnetoresistance spin-valve (GMR SV) read sensors have been numerically studied to explore the electrical and magnetic stability of the read sensor under real operation. The mean-time-to-failure (MTTF) of the CPP GMR SV read sensors was found to have a strong dependence on the physical parameters of the recording media and recorded information status, such as the pulse width of media stray field, the bit length, and the head moving velocity. According to the numerical calculation results, it was confirmed that in the longitudinal media, the shorter the stray field pulse width (i.e., the sharper the media transition) allows for the longer MTTF of the CPP GMR SV read sensors; while in the perpendicular media, the sharper the media transition gives rise to a shorter MTTF. Interestingly, it was also revealed that the MTTF could be improved by reducing the bit length as well as increasing the head velocity in both longitudinal and perpendicular media. Furthermore, the bit distribution patterns, especially the number of consecutive `0' bits strongly affected the MTTF of GMR SV read sensors. The strong dependences of MTTF on the media stray field during CPP GMR SV sensor operation are thought to be mainly attributed to the thermal cycling (temperature rise and fall) caused by the resistance change due to GMR effects.

Means and method for capillary zone electrophoresis with laser-induced indirect fluorescence detection

DOEpatents

Yeung, Edward S.; Kuhr, Werner G.

1996-02-20

A means and method for capillary zone electrphoresis with laser-induced indirect fluorescence detection. A detector is positioned on the capillary tube of a capillary zone electrophoresis system. The detector includes a laser which generates a laser beam which is imposed upon a small portion of the capillary tube. Fluorescence of the elutant electromigrating through the capillary tube is indirectly detected and recorded.

Means and method for capillary zone electrophoresis with laser-induced indirect fluorescence detection

DOEpatents

Yeung, Edwards; Kuhr, Werner G.

1991-04-09

A means and method for capillary zone electrphoresis with laser-induced indirect fluorescence detection. A detector is positioned on the capillary tube of a capillary zone electrophoresis system. The detector includes a laser which generates a laser beam which is imposed upon a small portion of the capillary tube. Fluorescence of the elutant electromigrating through the capillary tube is indirectly detected and recorded.

Electromigration and Deposition of Micro-Scale Calcium Carbonate Structures with Controlled Morphology and Polymorphism

DTIC Science & Technology

2013-04-01

precipitation of calcium carbonate in structured templates including microporous polycarbonate membranes and polyethylene foams. Para- meters...polyethylene foam). Microporous polycarbonate membranes and Medium-Density PolyEthylene (MDPE) foam specimens were used as the porous organic...voids in hardened concrete. DOI:10.1520/C624-06. West Conshohocken, PA: ASTM International . www.astm.org. Bersa, L., and M. Liu. 2007. A review on

Reliability of Next Generation Power Electronics Packaging Under Concurrent Vibration, Thermal and High Power Loads

DTIC Science & Technology

2008-02-01

combined thermal g effect and initial current field. The model is implemented using Abaqus user element subroutine and verified against the experimental...Finite Element Formulation The proposed model is implemented with ABAQUS general purpose finite element program using thermal -displacement analysis...option. ABAQUS and other commercially available finite element codes do not have the capability to solve general electromigration problem directly. Thermal

Generalized model of electromigration with 1:1 (analyte:selector) complexation stoichiometry: part I. Theory.

PubMed

Dubský, Pavel; Müllerová, Ludmila; Dvořák, Martin; Gaš, Bohuslav

2015-03-06

The model of electromigration of a multivalent weak acidic/basic/amphoteric analyte that undergoes complexation with a mixture of selectors is introduced. The model provides an extension of the series of models starting with the single-selector model without dissociation by Wren and Rowe in 1992, continuing with the monovalent weak analyte/single-selector model by Rawjee, Williams and Vigh in 1993 and that by Lelièvre in 1994, and ending with the multi-selector overall model without dissociation developed by our group in 2008. The new multivalent analyte multi-selector model shows that the effective mobility of the analyte obeys the original Wren and Row's formula. The overall complexation constant, mobility of the free analyte and mobility of complex can be measured and used in a standard way. The mathematical expressions for the overall parameters are provided. We further demonstrate mathematically that the pH dependent parameters for weak analytes can be simply used as an input into the multi-selector overall model and, in reverse, the multi-selector overall parameters can serve as an input into the pH-dependent models for the weak analytes. These findings can greatly simplify the rationale method development in analytical electrophoresis, specifically enantioseparations. Copyright © 2015 Elsevier B.V. All rights reserved.

Effects of Grain Orientation on Cu6Sn5 Growth Behavior in Cu6Sn5-Reinforced Composite Solder Joints During Electromigration

NASA Astrophysics Data System (ADS)

Han, Jing; Wang, Yan; Tan, Shihai; Guo, Fu

2018-02-01

Electromigration is a major reliability problem in composite solder joints. Due to the anisotropy of the β-Sn crystal structure, the Sn grain orientations present in the solder matrix dominate the principal failure mechanism in solder joints under electric current stressing. In this work, the Cu6Sn5 growth behavior in Cu6Sn5-reinforced composite solder joints with three different Sn grain orientations was investigated at current density of 104 A/cm2 at room temperature. Micron-sized Cu particles were added to Sn-3.5Ag solder at 2% volume fraction using an in situ method. After current stressing for 528 h, the polarity effect in the composite solder joint was greatest for an angle ( θ) between the c-axis and electron flow direction of 30°, resulting in higher growth rate of Cu6Sn5 in the solder matrix compared with composite solder joints with θ of 60° or 90°. There were no noticeable changes in the composite solder joint with θ of 90°. The growth behavior of Cu6Sn5, Cu atomic motion, and Cu diffusivity in the composite solder joints with different Sn grain orientations were analyzed in detail.

Innovative Multiphase Nanoparticle Composites Developed Using Electrophoresis And Electromigration

DTIC Science & Technology

2008-12-01

Fig. 2. Surface of enamel steel sheet showing the array of fine cracks in the enamel . Copper metal was deposited on the...suspensions of enameling frit are used, a layer of glass particles can be built up that can be fused into a tightly bonded vitreous coating. 1...Prescribed by ANSI Std Z39-18 Electrophoresis has been particularly important in enameling because it can deposit a glassy frit layer uniformly

Reliability Analysis/Assessment of Advanced Technologies

DTIC Science & Technology

1990-05-01

34, Reliability Physics 1980 , IEEE, p. 165. 25. RADC-TR-83-244. 26. Towner, Janet M., et. al., "Aluminum Electromigration Under Pulsed D.C. Conditions...Duvvury, Redwine, Kitagawa, Haas, Chuang, Beydler, Hyslop , "Impact of Hot Carriers On DRAM circuits", 1987 IEEE/IRPS. 58. Cahoon, Thornewell, Tsai...et. a]., "Substrate for Large Silicon Chip and Full Wafer Packaging", Semiconductor International, pp. 149-156, April 1980 . 5. T.E. Lewis and D.L

Study of complete interconnect reliability for a GaAs MMIC power amplifier

NASA Astrophysics Data System (ADS)

Lin, Qian; Wu, Haifeng; Chen, Shan-ji; Jia, Guoqing; Jiang, Wei; Chen, Chao

2018-05-01

By combining the finite element analysis (FEA) and artificial neural network (ANN) technique, the complete prediction of interconnect reliability for a monolithic microwave integrated circuit (MMIC) power amplifier (PA) at the both of direct current (DC) and alternating current (AC) operation conditions is achieved effectively in this article. As a example, a MMIC PA is modelled to study the electromigration failure of interconnect. This is the first time to study the interconnect reliability for an MMIC PA at the conditions of DC and AC operation simultaneously. By training the data from FEA, a high accuracy ANN model for PA reliability is constructed. Then, basing on the reliability database which is obtained from the ANN model, it can give important guidance for improving the reliability design for IC.

Fate of zinc in an electroplating sludge during electrokinetic treatments.

PubMed

Liu, Shou-Heng; Wang, H Paul

2008-08-01

Chemical structure of zinc in the electrokinetic treatments of an electroplating sludge has been studied by in situ extended X-ray absorption fine structural (EXAFS) and X-ray absorption near edge structural (XANES) spectroscopies in the present work. The least-square fitted XANES spectra indicate that the main zinc compounds in the sludge were ZnCO(3) (75%), ZnOSiO(2) (17%) and Zn(OH)(2) (7%). Zinc in the sludge possessed a Zn-O bond distance of 2.07 A with a coordination number (CN) of 5. In the second shells, the bond distance of Zn-(O)-Si was 3.05 A (CN=2). An increase of Zn-(O)-Si (0.05 A) with a decrease of its CN (from 5 to <1) was found in the early stage of the electrokinetic treatment. Prolong the electrokinetic treatment time to 180 min, about 34% of Zn(II) was dissolved into the aqueous phase and about 68% of Zn(II) in the sludge (or 23% of total zinc) was migrated to the cathode under the electric field (5 V cm(-1)). The dissolution and electromigration rates of Zn(II) in the sludge were 1.0 and 0.6 mmol h(-1)g(-1) sludge, respectively during the electrokinetic treatment. This work also exemplifies the utilization of in situ EXAFS and XANES for revealing speciation and possible reaction pathways during the course of zinc recycling from the sludge by electrokinetic treatments.

Integrative metabolomics for characterizing unknown low-abundance metabolites by capillary electrophoresis-mass spectrometry with computer simulations.

PubMed

Lee, Richard; Ptolemy, Adam S; Niewczas, Liliana; Britz-McKibbin, Philip

2007-01-15

Characterization of unknown low-abundance metabolites in biological samples is one the most significant challenges in metabolomic research. In this report, an integrative strategy based on capillary electrophoresis-electrospray ionization-ion trap mass spectrometry (CE-ESI-ITMS) with computer simulations is examined as a multiplexed approach for studying the selective nutrient uptake behavior of E. coli within a complex broth medium. On-line sample preconcentration with desalting by CE-ESI-ITMS was performed directly without off-line sample pretreatment in order to improve detector sensitivity over 50-fold for cationic metabolites with nanomolar detection limits. The migration behavior of charged metabolites were also modeled in CE as a qualitative tool to support MS characterization based on two fundamental analyte physicochemical properties, namely, absolute mobility (muo) and acid dissociation constant (pKa). Computer simulations using Simul 5.0 were used to better understand the dynamics of analyte electromigration, as well as aiding de novo identification of unknown nutrients. There was excellent agreement between computer-simulated and experimental electropherograms for several classes of cationic metabolites as reflected by their relative migration times with an average error of <2.0%. Our studies revealed differential uptake of specific amino acids and nucleoside nutrients associated with distinct stages of bacterial growth. Herein, we demonstrate that CE can serve as an effective preconcentrator, desalter, and separator prior to ESI-MS, while providing additional qualitative information for unambiguous identification among isobaric and isomeric metabolites. The proposed strategy is particularly relevant for characterizing unknown yet biologically relevant metabolites that are not readily synthesized or commercially available.

Size effect in Quincke rotation: a numerical study.

PubMed

Peters, F; Lobry, L; Khayari, A; Lemaire, E

2009-05-21

This paper deals with the Quincke rotation of small insulating particles. This dc electrorotation of insulating objects immersed in a slightly conducting liquid is usually explained by looking at the action of the free charges present in the liquid. Under the effect of the dc electric field, the charges accumulate at the surface of the insulating particle which, in turn, acquires a dipole moment in the direction opposite to that of the field and begins to rotate in order to flip its dipole moment. In the classical Quincke model, the charge distribution around the rotor is supposed to be purely superficial. A consequence of this assumption is that the angular velocity does not depend on the rotor size. Nevertheless, this hypothesis holds only if the rotor size is much larger than the characteristic ion layer thickness around the particle. In the opposite case, we show thanks to numerical calculations that the bulk charge distribution has to be accounted for to predict the electromechanical behavior of the rotor. We consider the case of an infinite insulating cylinder whose axis is perpendicular to the dc electric field. We use the finite element method to solve the conservation equations for the positive and the negative ions coupled with Navier-Stokes and Poisson equations. Doing so, we compute the bulk charge distribution and the velocity field in the liquid surrounding the cylinder. For sufficiently small cylinders, we show that the smaller the cylinder is, the smaller its angular velocity is when submitted to a dc electric field. This size effect is shown to originate both in ion diffusion and electromigration in the charge layer. At last, we propose a simple analytical model which allows calculating the angular velocity of the rotor when electromigration is present but weak and diffusion can be neglected.

Size effect in Quincke rotation: A numerical study

NASA Astrophysics Data System (ADS)

Peters, F.; Lobry, L.; Khayari, A.; Lemaire, E.

2009-05-01

This paper deals with the Quincke rotation of small insulating particles. This dc electrorotation of insulating objects immersed in a slightly conducting liquid is usually explained by looking at the action of the free charges present in the liquid. Under the effect of the dc electric field, the charges accumulate at the surface of the insulating particle which, in turn, acquires a dipole moment in the direction opposite to that of the field and begins to rotate in order to flip its dipole moment. In the classical Quincke model, the charge distribution around the rotor is supposed to be purely superficial. A consequence of this assumption is that the angular velocity does not depend on the rotor size. Nevertheless, this hypothesis holds only if the rotor size is much larger than the characteristic ion layer thickness around the particle. In the opposite case, we show thanks to numerical calculations that the bulk charge distribution has to be accounted for to predict the electromechanical behavior of the rotor. We consider the case of an infinite insulating cylinder whose axis is perpendicular to the dc electric field. We use the finite element method to solve the conservation equations for the positive and the negative ions coupled with Navier-Stokes and Poisson equations. Doing so, we compute the bulk charge distribution and the velocity field in the liquid surrounding the cylinder. For sufficiently small cylinders, we show that the smaller the cylinder is, the smaller its angular velocity is when submitted to a dc electric field. This size effect is shown to originate both in ion diffusion and electromigration in the charge layer. At last, we propose a simple analytical model which allows calculating the angular velocity of the rotor when electromigration is present but weak and diffusion can be neglected.

Growth of <111>-oriented Cu layer on thin TaWN films

NASA Astrophysics Data System (ADS)

Takeyama, Mayumi B.; Sato, Masaru

2017-07-01

In this study, we examine the growth of a <111>-oriented Cu layer on a thin TaWN ternary alloy barrier for good electromigration reliability. The strongly preferentially oriented Cu(111) layer is observed on a thin TaWN barrier even in the as-deposited Cu (100 nm)/TaWN (5 nm)/Si system. Also, this system tolerates annealing at 700 °C for 1 h without silicide reaction. It is revealed that the TaWN film is one of the excellent barriers with thermal stability and low resistivity. Simultaneously, the TaWN film is a candidate for a superior underlying material to achieve the Cu(111) preferential orientation.

Electromigration Related Effects At Metal-Metal Interfaces: Application To Railguns

DTIC Science & Technology

2007-03-01

found at the armature-rail contact due to local melting, to determine the kinetics of liquid flow Ga under electric current conditions. For this, a...model system comprising a bead of Ga on a Cu thin film track was devised in order to enable liquefaction and current induced movement of Ga to occur...along the Cu track. Upon application of current, Ga underwent liquefaction due to Joule heating and once liquid, it rapidly migrated along the Cu

On-clip high frequency reliability and failure test structures

DOEpatents

Snyder, Eric S.; Campbell, David V.

1997-01-01

Self-stressing test structures for realistic high frequency reliability characterizations. An on-chip high frequency oscillator, controlled by DC signals from off-chip, provides a range of high frequency pulses to test structures. The test structures provide information with regard to a variety of reliability failure mechanisms, including hot-carriers, electromigration, and oxide breakdown. The system is normally integrated at the wafer level to predict the failure mechanisms of the production integrated circuits on the same wafer.

Product Reliability Trends, Derating Considerations and Failure Mechanisms with Scaled CMOS

NASA Technical Reports Server (NTRS)

White, Mark; Vu, Duc; Nguyen, Duc; Ruiz, Ron; Chen, Yuan; Bernstein, Joseph B.

2006-01-01

As microelectronics is scaled into the deep sub-micron regime, space and aerospace users of advanced technology CMOS are reassessing how scaling effects impact long-term product reliability. The effects of electromigration (EM), time-dependent-dielectric-breakdown (TDDB) and hot carrier degradation (HCI and NBTI) wearout mechanisms on scaled technologies and product reliability are investigated, accelerated stress testing across several technology nodes is performed, and FA is conducted to confirm the failure mechanism(s).

Analytical characterization of wine and its precursors by capillary electrophoresis.

PubMed

Gomez, Federico J V; Monasterio, Romina P; Vargas, Verónica Carolina Soto; Silva, María F

2012-08-01

The accurate determination of marker chemical species in grape, musts, and wines presents a unique analytical challenge with high impact on diverse areas of knowledge such as health, plant physiology, and economy. Capillary electromigration techniques have emerged as a powerful tool, allowing the separation and identification of highly polar compounds that cannot be easily separated by traditional HPLC methods, providing complementary information and permitting the simultaneous analysis of analytes with different nature in a single run. The main advantage of CE over traditional methods for wine analysis is that in most cases samples require no treatment other than filtration. The purpose of this article is to present a revision on capillary electromigration methods applied to the analysis of wine and its precursors over the last decade. The current state of the art of the topic is evaluated, with special emphasis on the natural compounds that have allowed wine to be considered as a functional food. The most representative revised compounds are phenolic compounds, amino acids, proteins, elemental species, mycotoxins, and organic acids. Finally, a discussion on future trends of the role of capillary electrophoresis in the field of analytical characterization of wines for routine analysis, wine classification, as well as multidisciplinary aspects of the so-called "from soil to glass" chain is presented. © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Modeling pH variation in reverse osmosis.

PubMed

Nir, Oded; Bishop, Noga Fridman; Lahav, Ori; Freger, Viatcheslav

2015-12-15

The transport of hydronium and hydroxide ions through reverse osmosis membranes constitutes a unique case of ionic species characterized by uncommonly high permeabilities. Combined with electromigration, this leads to complex behavior of permeate pH, e.g., negative rejection, as often observed for monovalent ions in nanofiltration of salt mixtures. In this work we employed a rigorous phenomenological approach combined with chemical equilibrium to describe the trans-membrane transport of hydronium and hydroxide ions along with salt transport and calculate the resulting permeate pH. Starting from the Nernst-Planck equation, a full non-linear transport equation was derived, for which an approximate solution was proposed based on the analytical solution previously developed for trace ions in a dominant salt. Using the developed approximate equation, transport coefficients were deduced from experimental results obtained using a spiral wound reverse osmosis module operated under varying permeate flux (2-11 μm/s), NaCl feed concentrations (0.04-0.18 M) and feed pH values (5.5-9.0). The approximate equation agreed well with the experimental results, corroborating the finding that diffusion and electromigration, rather than a priori neglected convection, were the major contributors to the transport of hydronium and hydroxide. The approach presented here has the potential to improve the predictive capacity of reverse osmosis transport models for acid-base species, thereby improving process design/control. Copyright © 2015 Elsevier Ltd. All rights reserved.

The influence of microstructure on the probability of early failure in aluminum-based interconnects

NASA Astrophysics Data System (ADS)

Dwyer, V. M.

2004-09-01

For electromigration in short aluminum interconnects terminated by tungsten vias, the well known "short-line" effect applies. In a similar manner, for longer lines, early failure is determined by a critical value Lcrit for the length of polygranular clusters. Any cluster shorter than Lcrit is "immortal" on the time scale of early failure where the figure of merit is not the standard t50 value (the time to 50% failures), but rather the total probability of early failure, Pcf. Pcf is a complex function of current density, linewidth, line length, and material properties (the median grain size d50 and grain size shape factor σd). It is calculated here using a model based around the theory of runs, which has proved itself to be a useful tool for assessing the probability of extreme events. Our analysis shows that Pcf is strongly dependent on σd, and a change in σd from 0.27 to 0.5 can cause an order of magnitude increase in Pcf under typical test conditions. This has implications for the web-based two-dimensional grain-growth simulator MIT/EmSim, which generates grain patterns with σd=0.27, while typical as-patterned structures are better represented by a σd in the range 0.4 - 0.6. The simulator will consequently overestimate interconnect reliability due to this particular electromigration failure mode.

Surface evolution in bare bamboo-type metal lines under diffusion and electric field effects

NASA Astrophysics Data System (ADS)

Averbuch, Amir; Israeli, Moshe; Nathan, Menachem; Ravve, Igor

2003-07-01

Irregularities such as voids and cracks often occur in bamboo-type metal lines of microelectronic interconnects. They increase the resistance of the circuits, and may even lead to a fatal failure. In this work, we analyze numerically the electromigration of an unpassivated bamboo-type line with pre-existing irregularities in its top surface (also called a grain-void interface). The bamboo line is subjected to surface diffusion forces and external electric fields. Under these forces, initial defects may either heal or become worse. The grain-void interface is considered to be one-dimensional, and the physical formulation of an electromigration and diffusion model results in two coupled, fourth order, one-dimensional time-dependent PDEs, with the boundary conditions imposed at the electrode points and at the triple point, which belongs to two neighboring grains and the void. These equations are discretized by finite differences on a regular grid in space, and by a Runge-Kutta integration scheme in time, and solved simultaneously with a static Laplace equation describing the voltage distribution throughout each grain, when the substrate conductivity is neglected. Since the voltage distribution is required only along an interface line, the two-dimensional discretization of the grain interior is not needed, and the static problem is solved by the boundary element method at each time step. The motion of the interface line is studied for different ratios between diffusion and electric field forces, and for different initial configurations of the grain-void interface. We study plain and tilted contour lines, considering positive and negative tilts with respect to the external electric field, a stepped contour with field lines entering or exiting the 'step', and a number of modifications of the classical Mullins problem of thermal grooving. We also consider a two-grain Mullins problem with a normal and tilted boundary between the grains, examining positive and negative tilts.

Subnanometer Motion of Cargoes Driven by Thermal Gradients Along Carbon Nanotubes

NASA Astrophysics Data System (ADS)

Barreiro, Amelia; Rurali, Riccardo; Hernández, Eduardo R.; Moser, Joel; Pichler, Thomas; Forró, László; Bachtold, Adrian

2008-05-01

An important issue in nanoelectromechanical systems is developing small electrically driven motors. We report on an artificial nanofabricated motor in which one short carbon nanotube moves relative to another coaxial nanotube. A cargo is attached to an ablated outer wall of a multiwalled carbon nanotube that can rotate and/or translate along the inner nanotube. The motion is actuated by imposing a thermal gradient along the nanotube, which allows for subnanometer displacements, as opposed to an electromigration or random walk effect.

On-clip high frequency reliability and failure test structures

DOEpatents

Snyder, E.S.; Campbell, D.V.

1997-04-29

Self-stressing test structures for realistic high frequency reliability characterizations. An on-chip high frequency oscillator, controlled by DC signals from off-chip, provides a range of high frequency pulses to test structures. The test structures provide information with regard to a variety of reliability failure mechanisms, including hot-carriers, electromigration, and oxide breakdown. The system is normally integrated at the wafer level to predict the failure mechanisms of the production integrated circuits on the same wafer. 22 figs.

ESREF 98 - 9th European Symposium on Reliability of Electron Devices, Failure Physics and Analysis

DTIC Science & Technology

1998-10-19

Gap effects within a nanosecond time scale. Effective Density of States Because of the limited possibility of compact Mobility models to deal with the...brackets) and the dislocation source action mobility M. The force is the balance between the normal stress a,, on the dislocations and the osmotic The...on, the electromigration force acts theration kt. on the atoms and a transport to the anode side of the t It is the mobility term that accounts for

Effect of Electromigration on the Type of Drop Failure of Sn-3.0Ag-0.5Cu Solder Joints in PBGA Packages

NASA Astrophysics Data System (ADS)

Huang, M. L.; Zhao, N.

2015-10-01

Board-level drop tests of plastic ball grid array (PBGA) packages were performed in accordance with the Joint Electron Devices Engineering Council standard to investigate the effect of electromigration (EM) on the drop reliability of Sn-3.0Ag-0.5Cu solder joints with two substrate surface finishes, organic solderability preservative (OSP) and electroless nickel electroless palladium immersion gold (ENEPIG). In the as-soldered state, drop failures occurred at the substrate sides only, with cracks propagating within the interfacial intermetallic compound (IMC) layer for OSP solder joints and along the IMC/Ni-P interface for ENEPIG solder joints. The drop lifetime of OSP solder joints was approximately twice that of ENEPIG joints. EM had an important effect on crack formation and drop lifetime of the PBGA solder joints. ENEPIG solder joints performed better in drop reliability tests after EM, that is, the drop lifetime of ENEPIG joints decreased by 43% whereas that of OSP solder joints decreased by 91%, compared with the as-soldered cases. The more serious polarity effect, i.e., excessive growth of the interfacial IMC at the anode, was responsible for the sharper decrease in drop lifetime. The different types of drop failure of PBGA solder joints before and after EM, including the position of initiation and the propagation path of cracks, are discussed on the basis of the growth behavior of interfacial IMC.

Simulations of stress evolution and the current density scaling of electromigration-induced failure times in pure and alloyed interconnects

NASA Astrophysics Data System (ADS)

Park, Young-Joon; Andleigh, Vaibhav K.; Thompson, Carl V.

1999-04-01

An electromigration model is developed to simulate the reliability of Al and Al-Cu interconnects. A polynomial expression for the free energy of solution by Murray [Int. Met. Rev. 30, 211 (1985)] was used to calculate the chemical potential for Al and Cu while the diffusivities were defined based on a Cu-trapping model by Rosenberg [J. Vac. Sci. Technol. 9, 263 (1972)]. The effects of Cu on stress evolution and lifetime were investigated in all-bamboo and near-bamboo stud-to-stud structures. In addition, the significance of the effect of mechanical stress on the diffusivity of both Al and Cu was determined in all-bamboo and near-bamboo lines. The void nucleation and growth process was simulated in 200 μm, stud-to-stud lines. Current density scaling behavior for void-nucleation-limited failure and void-growth-limited failure modes was simulated in long, stud-to-stud lines. Current density exponents of both n=2 for void nucleation and n=1 for void growth failure modes were found in both pure Al and Al-Cu lines. Limitations of the most widely used current density scaling law (Black's equation) in the analysis of the reliability of stud-to-stud lines are discussed. By modifying the input materials properties used in this model (when they are known), this model can be adapted to predict the reliability of other interconnect materials such as pure Cu and Cu alloys.

Electromigration in Cu(Al) and Cu(Mn) damascene lines

NASA Astrophysics Data System (ADS)

Hu, C.-K.; Ohm, J.; Gignac, L. M.; Breslin, C. M.; Mittal, S.; Bonilla, G.; Edelstein, D.; Rosenberg, R.; Choi, S.; An, J. J.; Simon, A. H.; Angyal, M. S.; Clevenger, L.; Maniscalco, J.; Nogami, T.; Penny, C.; Kim, B. Y.

2012-05-01

The effects of impurities, Mn or Al, on interface and grain boundary electromigration (EM) in Cu damascene lines were investigated. The addition of Mn or Al solute caused a reduction in diffusivity at the Cu/dielectric cap interface and the EM activation energies for both Cu-alloys were found to increase by about 0.2 eV as compared to pure Cu. Mn mitigated and Al enhanced Cu grain boundary diffusion; however, no significant mitigation in Cu grain boundary diffusion was observed in low Mn concentration samples. The activation energies for Cu grain boundary diffusion were found to be 0.74 ± 0.05 eV and 0.77 ± 0.05 eV for 1.5 μm wide polycrystalline lines with pure Cu and Cu (0.5 at. % Mn) seeds, respectively. The effective charge number in Cu grain boundaries Z*GB was estimated from drift velocity and was found to be about -0.4. A significant enhancement in EM lifetimes for Cu(Al) or low Mn concentration bamboo-polycrystalline and near-bamboo grain structures was observed but not for polycrystalline-only alloy lines. These results indicated that the existence of bamboo grains in bamboo-polycrystalline lines played a critical role in slowing down the EM-induced void growth rate. The bamboo grains act as Cu diffusion blocking boundaries for grain boundary mass flow, thus generating a mechanical stress-induced back flow counterbalancing the EM force, which is the equality known as the "Blech short length effect."

High frequency pulsed electromigration

NASA Astrophysics Data System (ADS)

Malone, David Wayne

Electromigration life tests were performed on copper-alloyed aluminum test structures that were representative of modern CMOS metallization schemes, complete with Ti/TiN cladding layers and a tungsten-plug contact at the cathode. A total of 18 electrical stress treatments were applied. One was a DC current of 15 mA. The other 17 were pulsed currents, varied according to duty cycle and frequency. The pulse amplitude was 15 mA (˜2.7 × 10sp6 A/cmsp2) for all treatments. Duty cycles ranged from 33.3% to 80%, and frequencies fell into three rough ranges-100 KHz, 1 MHz, and 100 MHz. The ambient test temperature was 200sp°C in all experiments. Six to 9 samples were subjected to each treatment. Experimental data were gathered in the form of test stripe resistance versus time, R(t). For purposes of lifetime analysis, "failure" was defined by the criterion R(t)/R(0) = 1.10, and the median time to failure, tsb{50}, was used as the primary basis of comparison between test groups. It was found that the dependence of tsb{50} on pulse duty cycle conformed rather well to the so-called "average current density model" for duty cycles of 50% and higher. Lifetimes were less enhanced for a duty cycle of 33.3%, but they were still considerably longer than an "on-time" model would predict. No specific dependence of tsb{50} on pulse frequency was revealed by the data, that is, reasonably good predictions of tsb{50} could be made by recognizing the dominant influence of duty cycle. These findings confirm that IC miniaturization can be more aggressively pursued than an on-time prediction would allow. It is significant that this was found to be true for frequencies on the order of 100 MHz, where many present day digital applications operate. Post-test optical micrographs were obtained for each test subject in order to determine the location of electromigration damage. The pulse duty cycle was found to influence the location. Most damage occurred at the cathode contact, regardless of treatment conditions, but there was an increased incidence of damage farther downwind with decreasing duty cycle. This tendency and the deviation from the average current density model for small duty cycles were explained in terms of the Blech length, its dependence on microstructure and duty cycle, and its impact on the relative rates of damage and recovery.

Dry silver electromigration process for optical glass waveguide fabrication and fluxless bonding technology for photonics and MEMS packaging

NASA Astrophysics Data System (ADS)

Chuang, Ricky Wenkuei

2001-07-01

An effectively simple dry silver electromigration technology without the need of evaporating separate gold or aluminum film electrodes onto both sides of glass is reported to fabricate low-loss deep multimode planar and channel waveguides on BK7 and BF450 glass substrates. A relatively high electrical field ranging from 440 to 545 V/mm was applied to the glass to speed up the migration, while at the same time preventing silver ions that were driven into the glass from reducing into silver atom; a major contributor to waveguide loss. The deep planar and channel waveguides thus fabricated showed no discolors or cracks, of which the attenuation losses of less than 2dB/cm and 0.1dB/cm were later measured from channel waveguides constructed on the BK7 and BF450 glass substrates, respectively, using our 0.6328mum He-Ne laser edge-coupling setup. To complete the waveguide studies, the scanning electron microscope (SEM) equipped with energy-dispersive X-ray (EDX) detector was adopted to obtain the concentration profiles of silver and sodium ions distributed in a waveguiding region after the exchange. The EDX measurements acquired hereafter were then utilized along with the Gladstone-Dale relation altogether to deduce the refractive index profile; of which a nearly step-like profile was consistently deduced from every deep planar and channel waveguides fabricated. Finally, a numerical model utilizing the space charge approach was devised to explain the nonlinear current effect often observed during the actual waveguide fabrication. The simulation results have confirmed that the nonlinear current-versus-time profile obtained is mainly attributed to the inhomogeneous distribution of the electric field in the glass substrate due to a space charge region created by the separation between silver- and sodium-ion migration fronts as a result of their unequal mobilities; a phenomenon which is ultimately responsible for the eventual slow down in the ion exchange rate as monitored during the actual electromigration process. A fluxless oxidation-free bonding technology using multilayer composite solders based on the non eutectic binary alloys of indium-tin (In-Sn), silver-indium (Ag-In), gold-tin (Au-Sn), and bismuth-tin (Bi-Sn) has been established and studied to determine its applicability to photonics and MEMS packaging. The scanning acoustic microscopy (SAM) conducted on these solder samples has consistently shown that a nearly void-free joint fabricated from each non-eutectic binary alloy system can be reliably achieved. In addition, the scanning electron microscopy (SEM) equipped with the energy dispersive X-ray (EDX) detector was also performed on the cross section of each sample to determine its joint composition, especially of any sign of intermetallic compounds. These results will demonstrate that any intermetallic compound or phase present in a joint fabricated with a pre-determined multilayer composition based on a specific binary alloy system can be well understood and fully justified by correlating the experimental outcome with its respective binary phase diagram.

A new configuration of membrane stack for retrieval of nickel absorbed in resins*

PubMed Central

Chen, Xue-fen; Wu, Zu-cheng

2005-01-01

A new configuration integrated ion exchange effect with both electro-migration and electrochemical reaction in a single cell was developed to effectively retrieve metal ions from simulated wastewater using ion exchange resins without additive chemicals. By simply assembling cation exchange resins and anion exchange resins separated by homogeneous membranes, we found that the system will always be acidic in the concentrate compartment so that ion exchange resins could be in-situ regenerated without hydroxide precipitation. Such a realizable design will be really suitable for wastewater purification. PMID:15909341

Computation for Electromigration in Interconnects of Microelectronic Devices

NASA Astrophysics Data System (ADS)

Averbuch, Amir; Israeli, Moshe; Ravve, Igor; Yavneh, Irad

2001-03-01

Reliability and performance of microelectronic devices depend to a large extent on the resistance of interconnect lines. Voids and cracks may occur in the interconnects, causing a severe increase in the total resistance and even open circuits. In this work we analyze void motion and evolution due to surface diffusion effects and applied external voltage. The interconnects under consideration are three-dimensional (sandwich) constructs made of a very thin metal film of possibly variable thickness attached to a substrate of nonvanishing conductance. A two-dimensional level set approach was applied to study the dynamics of the moving (assumed one-dimensional) boundary of a void in the metal film. The level set formulation of an electromigration and diffusion model results in a fourth-order nonlinear (two-dimensional) time-dependent PDE. This equation was discretized by finite differences on a regular grid in space and a Runge-Kutta integration scheme in time, and solved simultaneously with a second-order static elliptic PDE describing the electric potential distribution throughout the interconnect line. The well-posed three-dimensional problem for the potential was approximated via singular perturbations, in the limit of small aspect ratio, by a two-dimensional elliptic equation with variable coefficients describing the combined local conductivity of metal and substrate (which is allowed to vary in time and space). The difference scheme for the elliptic PDE was solved by a multigrid technique at each time step. Motion of voids in both weak and strong electric fields was examined, and different initial void configurations were considered, including circles, ellipses, polygons with rounded corners, a butterfly, and long grooves. Analysis of the void behavior and its influence on the resistance gives the circuit designer a tool for choosing the proper parameters of an interconnect (width-to-length ratio, properties of the line material, conductivity of the underlayer, etc.).

Enhancing the efficiency of zero valent iron by electrolysis: Performance and reaction mechanism.

PubMed

Xiong, Zhaokun; Lai, Bo; Yang, Ping

2018-03-01

Electrolysis was applied to enhance the efficiency of micron-size zero valent iron (mFe 0 ) and thereby promote p-nitrophenol (PNP) removal. The rate of PNP removal by mFe 0 with electrolysis was determined in cylindrical electrolysis reactor that employed annular aluminum plate cathode as a function of experimental factors, including initial pH, mFe 0 dosage and current density. The rate constants of PNP removal by Ele-mFe 0 were 1.72-144.50-fold greater than those by pristine mFe 0 under various tested conditions. The electrolysis-induced improvement could be primarily ascribed to stimulated mFe 0 corrosion, as evidenced by Fe 2+ release. The application of electrolysis could extend the working pH range of mFe 0 from 3.0 to 6.0 to 3.0-10.0 for PNP removal. Additionally, intermediates analysis and scavengers experiments unraveled the reduction capacity of mFe 0 was accelerated in the presence of electrolysis instead of oxidation. Moreover, the electrolysis effect could also delay passivation of mFe 0 under acidic condition, as evidenced by SEM-EDS, XRD, and XPS analysis after long-term operation. This is mainly due to increased electromigration meaning that iron corrosion products (iron hydroxides and oxides) are not primarily formed in the vicinity of the mFe 0 or at its surface. In the presence of electrolysis, the effect of electric field significantly promoted the efficiency of electromigration, thereby enhanced mFe 0 corrosion and eventually accelerated the PNP removal rates. Copyright © 2017 Elsevier Ltd. All rights reserved.

Determination of thermodynamic values of acidic dissociation constants and complexation constants of profens and their utilization for optimization of separation conditions by Simul 5 Complex.

PubMed

Riesová, Martina; Svobodová, Jana; Ušelová, Kateřina; Tošner, Zdeněk; Zusková, Iva; Gaš, Bohuslav

2014-10-17

In this paper we determine acid dissociation constants, limiting ionic mobilities, complexation constants with β-cyclodextrin or heptakis(2,3,6-tri-O-methyl)-β-cyclodextrin, and mobilities of resulting complexes of profens, using capillary zone electrophoresis and affinity capillary electrophoresis. Complexation parameters are determined for both neutral and fully charged forms of profens and further corrected for actual ionic strength and variable viscosity in order to obtain thermodynamic values of complexation constants. The accuracy of obtained complexation parameters is verified by multidimensional nonlinear regression of affinity capillary electrophoretic data, which provides the acid dissociation and complexation parameters within one set of measurements, and by NMR technique. A good agreement among all discussed methods was obtained. Determined complexation parameters were used as input parameters for simulations of electrophoretic separation of profens by Simul 5 Complex. An excellent agreement of experimental and simulated results was achieved in terms of positions, shapes, and amplitudes of analyte peaks, confirming the applicability of Simul 5 Complex to complex systems, and accuracy of obtained physical-chemical constants. Simultaneously, we were able to demonstrate the influence of electromigration dispersion on the separation efficiency, which is not possible using the common theoretical approaches, and predict the electromigration order reversals of profen peaks. We have shown that determined acid dissociation and complexation parameters in combination with tool Simul 5 Complex software can be used for optimization of separation conditions in capillary electrophoresis. Copyright © 2014 Elsevier B.V. All rights reserved.

Mathematical modeling and computer simulation of isoelectric focusing with electrochemically defined ampholytes

NASA Technical Reports Server (NTRS)

Palusinski, O. A.; Allgyer, T. T.; Mosher, R. A.; Bier, M.; Saville, D. A.

1981-01-01

A mathematical model of isoelectric focusing at the steady state has been developed for an M-component system of electrochemically defined ampholytes. The model is formulated from fundamental principles describing the components' chemical equilibria, mass transfer resulting from diffusion and electromigration, and electroneutrality. The model consists of ordinary differential equations coupled with a system of algebraic equations. The model is implemented on a digital computer using FORTRAN-based simulation software. Computer simulation data are presented for several two-component systems showing the effects of varying the isoelectric points and dissociation constants of the constituents.

Reduction of the 3,4,9,10-perylenediimides and the formation of eletrodeposited films based on their radical anions

NASA Astrophysics Data System (ADS)

Zhu, Yuan-Yuan; Gu, Shuang-Xi

2014-09-01

The reduction of the two 3,4,9,10-perylene diimide (PDI) derivatives in the mixture of hydrazine hydrate and N,N-dimethylformamide was investigated by the UV-vis absorption spectra, fluorescence spectra (FL) and electron spin resonance spectroscopy (ESR). The time dependence of the PDI content, as well as the structure of PDI aggregates were also investigated and discussed. Combining the electro-migration behavior of PDI-· with the molecular self-assembly properties, the films of two PDI derivatives (PDI-32 and PDI-123) were successfully fabricated via anode electro-deposition (AED). The difference of aggregation state between the two PDI films was studied by UV-vis absorption spectra, XRD and SEM. Based on these, the formation mechanism of PDI films was also deduced.

Equivalence-point electromigration acid-base titration via moving neutralization boundary electrophoresis.

PubMed

Yang, Qing; Fan, Liu-Yin; Huang, Shan-Sheng; Zhang, Wei; Cao, Cheng-Xi

2011-04-01

In this paper, we developed a novel method of acid-base titration, viz. the electromigration acid-base titration (EABT), via a moving neutralization boundary (MNR). With HCl and NaOH as the model strong acid and base, respectively, we conducted the experiments on the EABT via the method of moving neutralization boundary for the first time. The experiments revealed that (i) the concentration of agarose gel, the voltage used and the content of background electrolyte (KCl) had evident influence on the boundary movement; (ii) the movement length was a function of the running time under the constant acid and base concentrations; and (iii) there was a good linearity between the length and natural logarithmic concentration of HCl under the optimized conditions, and the linearity could be used to detect the concentration of acid. The experiments further manifested that (i) the RSD values of intra-day and inter-day runs were less than 1.59 and 3.76%, respectively, indicating similar precision and stability in capillary electrophoresis or HPLC; (ii) the indicators with different pK(a) values had no obvious effect on EABT, distinguishing strong influence on the judgment of equivalence-point titration in the classic one; and (iii) the constant equivalence-point titration always existed in the EABT, rather than the classic volumetric analysis. Additionally, the EABT could be put to good use for the determination of actual acid concentrations. The experimental results achieved herein showed a new general guidance for the development of classic volumetric analysis and element (e.g. nitrogen) content analysis in protein chemistry. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Generalized model of electromigration with 1:1 (analyte:selector) complexation stoichiometry: part II. Application to dual systems and experimental verification.

PubMed

Müllerová, Ludmila; Dubský, Pavel; Gaš, Bohuslav

2015-03-06

Interactions among analyte forms that undergo simultaneous dissociation/protonation and complexation with multiple selectors take the shape of a highly interconnected multi-equilibrium scheme. This makes it difficult to express the effective mobility of the analyte in these systems, which are often encountered in electrophoretical separations, unless a generalized model is introduced. In the first part of this series, we presented the theory of electromigration of a multivalent weakly acidic/basic/amphoteric analyte undergoing complexation with a mixture of an arbitrary number of selectors. In this work we demonstrate the validity of this concept experimentally. The theory leads to three useful perspectives, each of which is closely related to the one originally formulated for simpler systems. If pH, IS and the selector mixture composition are all kept constant, the system is treated as if only a single analyte form interacted with a single selector. If the pH changes at constant IS and mixture composition, the already well-established models of a weakly acidic/basic analyte interacting with a single selector can be employed. Varying the mixture composition at constant IS and pH leads to a situation where virtually a single analyte form interacts with a mixture of selectors. We show how to switch between the three perspectives in practice and confirm that they can be employed interchangeably according to the specific needs by measurements performed in single- and dual-selector systems at a pH where the analyte is fully dissociated, partly dissociated or fully protonated. Weak monoprotic analyte (R-flurbiprofen) and two selectors (native β-cyclodextrin and monovalent positively charged 6-monodeoxy-6-monoamino-β-cyclodextrin) serve as a model system. Copyright © 2015 Elsevier B.V. All rights reserved.

Effect of Sn-Ag-Cu on the Improvement of Electromigration Behavior in Sn-58Bi Solder Joint

NASA Astrophysics Data System (ADS)

Wang, Fengjiang; Zhou, Lili; Zhang, Zhijie; Wang, Jiheng; Wang, Xiaojing; Wu, Mingfang

2017-10-01

Reliability issues caused by the formation of a Bi-rich layer at the anode interface usually occurs in the Sn-58Bi eutectic solder joint during electromigration (EM). To improve the EM performance of a Sn-58Bi solder joint, Sn-3.0Ag-0.5Cu solder was introduced into it to produce SnBi-SnAgCu structural or compositional composite joints, and their EM behaviors were investigated with the current density of 1.0 × 104 A/cm2 for different stressing times. The structure of the compositional composite solder joint was obtained by the occurrence of partial or full mixing between Sn-Bi and Sn-Ag-Cu solder with a suitable soldering temperature. In the structural composite joint, melted Sn-Bi was partially mixed with Sn-Ag-Cu solder to produce a Cu/Sn-Bi/Sn-Ag-Cu/Sn-Bi/Cu structure. In the compositional composite joint, full melting and mixing between these two solders occurred to produce a Cu/Sn-Ag-Cu-Bi/Cu structure, in which the solder matrix was a homogeneous structure including Sn, Bi phases, Cu6Sn5 and Ag3Sn IMCs. After current stressing, the EM performance of Sn-Bi solder was obviously improved with the structural or the compositional composite joint. In Sn-58Bi joints, a thick Bi-rich layer was easily produced at the anode interface, and obviously increased with stressing time. However, after current stressing on the structural composite joints, the existence of s Sn-3.0Ag-0.5Cu interlayer between the two Sn-58Bi solders effectively acted as a diffusion barrier and significantly slowed the formation of the Bi-rich layer at the anode side and the IMC thicknesses at the interfaces.

An investigation into the feasibility of myoglobin-based single-electron transistors

PubMed Central

Li, Debin; Gannett, Peter M.; Lederman, David

2016-01-01

Myoglobin single-electron transistors were investigated using nanometer-gap platinum electrodes fabricated by electromigration at cryogenic temperatures. Apomyoglobin (myoglobin without heme group) was used as a reference. The results suggest single electron transport is mediated by resonant tunneling with the electronic and vibrational levels of the heme group in a single protein. They also represent a proof-of-principle that proteins with redox centers across nanometer-gap electrodes can be utilized to fabricate single-electron transistors. The protein orientation and conformation may significantly affect the conductance of these devices. Future improvements in device reproducibility and yield will require control of these factors. PMID:22972432

Effect of Sn Grain Orientation on the Cu6Sn5 Formation in a Sn-Based Solder Under Current Stressing

NASA Astrophysics Data System (ADS)

Lin, Chih-Fan; Lee, Shang-Hua; Chen, Chih-Ming

2012-08-01

A SnAgCu-based solder stripe between two Cu electrodes is current stressed with a density of 5 × 104 A/cm2 at 393 K (120 °C). After current stressing for 24 hours, electromigration induces the Cu dissolution from the cathode-side Cu electrode, leading to the Cu6Sn5 formation in the solder stripe. Very interestingly, the Cu6Sn5 phase is selectively formed within a specific Sn grain. Electron backscattering diffraction analysis indicates the crystallographic orientations of Sn grains play an important role in the selective Cu6Sn5 formation.

A graphene integrated highly transparent resistive switching memory device

NASA Astrophysics Data System (ADS)

Dugu, Sita; Pavunny, Shojan P.; Limbu, Tej B.; Weiner, Brad R.; Morell, Gerardo; Katiyar, Ram S.

2018-05-01

We demonstrate the hybrid fabrication process of a graphene integrated highly transparent resistive random-access memory (TRRAM) device. The indium tin oxide (ITO)/Al2O3/graphene nonvolatile memory device possesses a high transmittance of >82% in the visible region (370-700 nm) and exhibits stable and non-symmetrical bipolar switching characteristics with considerably low set and reset voltages (<±1 V). The vertical two-terminal device shows an excellent resistive switching behavior with a high on-off ratio of ˜5 × 103. We also fabricated a ITO/Al2O3/Pt device and studied its switching characteristics for comparison and a better understanding of the ITO/Al2O3/graphene device characteristics. The conduction mechanisms in high and low resistance states were analyzed, and the observed polarity dependent resistive switching is explained based on electro-migration of oxygen ions.

A numerical study on electrochemical transport of ions in calcium fluoride slag

NASA Astrophysics Data System (ADS)

Karimi-Sibaki, E.; Kharicha, A.; Wu, M.; Ludwig, A.

2016-07-01

Electrically resistive CaF 2-based slags are widely used in electroslag remelting (ESR) process to generate Joule heat for the melting of electrode. The electric current is conducted by ions (electrolyte) such as Ca +2 or F -, thus it is necessary to establish electrochemical models to study electrical behavior of slag. This paper presents a numerical model on electrochemical transport of ions in an arbitrary symmetrical (ZZ) and non-symmetrical (CaF2) stagnant electrolytes blocked by two parallel, planar electrodes. The dimensionless Poisson-Nernst-Planck (PNP) equations are solved to model electro-migration and diffusion of ions. The ions are considered to be inert that no Faradic reactions occur. Spatial variations of concentrations of ions, charge density and electric potential across the electrolyte are analyzed. It is shown that the applied potential has significant influence on the system response. At high applied voltage, the anodic potential drop near the electrode is significantly larger than cathodic potential drop in fully dissociated CaF2 electrolyte.

Application of Lattice Boltzmann Methods in Complex Mass Transfer Systems

NASA Astrophysics Data System (ADS)

Sun, Ning

Lattice Boltzmann Method (LBM) is a novel computational fluid dynamics method that can easily handle complex and dynamic boundaries, couple local or interfacial interactions/reactions, and be easily parallelized allowing for simulation of large systems. While most of the current studies in LBM mainly focus on fluid dynamics, however, the inherent power of this method makes it an ideal candidate for the study of mass transfer systems involving complex/dynamic microstructures and local reactions. In this thesis, LBM is introduced to be an alternative computational method for the study of electrochemical energy storage systems (Li-ion batteries (LIBs) and electric double layer capacitors (EDLCs)) and transdermal drug design on mesoscopic scale. Based on traditional LBM, the following in-depth studies have been carried out: (1) For EDLCs, the simulation of diffuse charge dynamics is carried out for both the charge and the discharge processes on 2D systems of complex random electrode geometries (pure random, random spheres and random fibers). Steric effect of concentrated solutions is considered by using modified Poisson-Nernst-Plank (MPNP) equations and compared with regular Poisson-Nernst-Plank (PNP) systems. The effects of electrode microstructures (electrode density, electrode filler morphology, filler size, etc.) on the net charge distribution and charge/discharge time are studied in detail. The influence of applied potential during discharging process is also discussed. (2) For the study of dendrite formation on the anode of LIBs, it is shown that the Lattice Boltzmann model can capture all the experimentally observed features of microstructure evolution at the anode, from smooth to mossy to dendritic. The mechanism of dendrite formation process in mesoscopic scale is discussed in detail and compared with the traditional Sand's time theories. It shows that dendrite formation is closely related to the inhomogeneous reactively at the electrode-electrolyte interface. When the inhomogeneity is small, dendrites form mainly under high current densities, in which the mass transfer is dominated by electromigration; when the inhomogeneity is very large, dendrites may form under both high and low current densities, which is dominated by electromigration in high current density and by surface reactivity in low current density. We show that the critical current density for dendrite formation is sensitive to surface inhomogeneous reactivity and the onset time of dendrite formation is sensitive to the initial roughness of electrode. A new analysis method is introduced, which can predict the formation of dendrites in batteries at a very early stage even before large dendrites form. Charge/discharge cyclic properties of the system are also studied, which shows that electrode roughness will increase during cycles and the break-off of dendritic structures is inevitable once big dendrites form; however, it is possible to minimize the amount of break-off materials by optimizing the rate of discharge. (3) The LBM is also used to simulate intercalation reactions in a Li-Ion battery with graphite as anode and pure Li metal as counter electrode. Both galvanostatic and potentiostatic conditions were studied. The relation between operation parameters (current and potential) and electrode parameters (porosity, thickness and diffusivity) and plating times were discussed. Different equilibrium potentials forms (empirical fitting, fitting of SONY 18650 cell, and staged profiles) were also compared. By modifying the morphology of electrode with a density gradient, it was shown that much better electrode performance can be obtained, which can be helpful for the designing and manufacturing of better batteries. (4) The transdermal drug delivery system is also simulated by using LBM. Two kinds of transdermal structures are discussed: "brick and mortar" structure and a simple homogenized structure. It is demonstrated that the homogenized system is able to obtain similar steady state flux as the "brick and mortar" structure; however, in the early transient region, their flux value can be different. The influence of different system parameters (amount of drug in patch, patch thickness, partition coefficient at patch/ Stratum Corneum (SC) interface, and the diffusion coefficient of drug in each component) is discussed in details. It turns out that in this system, the rate-determine step for mass transfer should be the partition between patch and SC layers and the diffusion in the SC layer. The influence of enhancer is also tested. It is shown that by adding enhancers, the drug flux can be significantly increased. However, the peak time of drug does not necessarily match the peak flux time of enhancer. The peak time of drug could be adjusted (pushed earlier or dragged later) by using different kinds of enhancers, which has higher/smaller diffusivity than drug in the SC layer.

Synaptic plasticity and oscillation at zinc tin oxide/silver oxide interfaces

NASA Astrophysics Data System (ADS)

Murdoch, Billy J.; McCulloch, Dougal G.; Partridge, James G.

2017-02-01

Short-term plasticity, long-term potentiation, and pulse interval dependent plasticity learning/memory functions have been observed in junctions between amorphous zinc-tin-oxide and silver-oxide. The same junctions exhibited current-controlled negative differential resistance and when connected in an appropriate circuit, they behaved as relaxation oscillators. These oscillators produced voltage pulses suitable for device programming. Transmission electron microscopy, energy dispersive X-ray spectroscopy, and electrical measurements suggest that the characteristics of these junctions arise from Ag+/O- electromigration across a highly resistive interface layer. With memory/learning functions and programming spikes provided in a single device structure, arrays of similar devices could be used to form transistor-free neuromorphic circuits.

Application of Nano-SiO₂ and Nano-Fe₂O₃ for Protection of Steel Rebar in Chloride Contaminated Concrete: Epoxy Nanocomposite Coatings and Nano-Modified Mortars.

PubMed

Nguyen, Tuan Anh; Nguyen, The Huyen; Pham, Thi Lua; Dinh, Thi Mai Thanh Dinh; Thai, Hoang; Shi, Xianming

2017-01-01

The effect of incorporating nanoparticles on the corrosion resistance of epoxy-coated steel in salt contaminated mortars was investigated using potentiodynamic polarization and electrochemical impedance spectroscopy. Researchers conducted electrochemical monitoring of the coated steel embedded in mortar over 100 days of immersion in 0.1 M NaOH solutions. The chloride permeability and microstructure of Portland cement mortar with admixed nano-materials (at 1% by weight of cement) were examined using an electromigration test and field emission scanning electron microscopy (FESEM). Electrochemical monitoring showed that nano Fe₂O₃ improved the corrosion resistance of the coated rebar. The incorporation of a small amount of nano Fe₂O₃ (1% by total weight of resin and hardener) into the epoxy coating reduced the corrosion current of the epoxy-coated steel in chloride-contaminated mortar (0.3% chloride by weight of cement). After 100 days of immersion, the nanoparticles reduced the corrosion current of epoxy-coated steel by a factor of 6. The FESEM test revealed that admixing of nano-materials not only led to denser cement mortar but also changed the morphology of cement hydration products. The test results of compressive strength showed that nanoparticles increased the strength of cement mortar. The electromigration test showed that the incorporation of nanoparticles improved the chloride penetration resistance of the mortar, as indicated by the reduced apparent diffusion coefficients of the chloride anion. When nano-SiO₂ and nano-Fe₂O₃ were admixed into fresh cement mortar at 1% by weight of cement, the value of D(Cl−) was decreased by 83%, from 7.35×10(−11) m²/s (control specimen) to 1.21×10(−11) m²/s and 1.36×10(−11) m²/s, respectively.

A critical overview of non-aqueous capillary electrophoresis. Part I: mobility and separation selectivity.

PubMed

Kenndler, Ernst

2014-03-28

This two-part review critically gives an overview on the theoretical and practical advances in non-aqueous capillary electrophoresis (NACE) achieved over the recent five years. Part I starts out by reviewing the aspects relevant to electromigration in organic solvents and evaluates potential advantages of the latter in comparison to aqueous solvent systems. The crucial role of solubility for the species involved in CE - analytes and back ground electrolyte constituents - is discussed both for ionic and neutral compounds. The impact of organic solvents on the electrophoretic and electroosmotic mobility and on the ionization (pKa values) of weak acids and bases is highlighted. Special emphasis is placed on methanol, acetonitrile and mixtures of these solvents, being the most frequent employed media for NACE applications. In addition, also solvents less commonly used in NACE will be covered, including other alcohols, amides (formamide, N-methylformamide, N,N-dimethylformamide, N,N-dimethylacetamide), propylene carbonate, dimethylsulphoxide, and nitromethane. The discussions address the consequences of dramatic pKa shifts frequently seen for weak acids and bases, and the important contributions of medium-specific electroosmotic flow (EOF) to electromigration in nonaqueous media. Important for NACE, the role of the water content on pKa and mobility is analyzed. Finally, association phenomena rather specific to nonaqueous solvents (ion pairing, homo- and heteroconjugation) will be addressed, along with their potential advantages for the development of NACE separation protocols. It is pointed out that this review is not intended as a listing of all papers that have been published on NACE in the period mentioned above. It rather deals with general aspects of migration and selectivity in organic solvent systems, and discusses - critically - examples from the literature with particular interest to the topic. An analog discussion about the role of the solvent on efficiency will be presented in Part II. Copyright © 2014 Elsevier B.V. All rights reserved.

EM calibration based on Post OPC layout analysis

NASA Astrophysics Data System (ADS)

Sreedhar, Aswin; Kundu, Sandip

2010-03-01

Design for Manufacturability (DFM) involves changes to the design and CAD tools to help increase pattern printability and improve process control. Design for Reliability (DFR) performs the same to improve reliability of devices from failures such as Electromigration (EM), gate-oxide break down, hot carrier injection (HCI), Negative Bias Temperature Insatiability (NBTI) and mechanical stress effects. Electromigration (EM) occurs due to migration or displacement of atoms as a result of the movement of electrons through a conducting medium. The rate of migration determines the Mean Time to Failure (MTTF) which is modeled as a function of temperature and current density. The model itself is calibrated through failure analysis (FA) of parts that are deemed to have failed due to EM against design parameters such as linewidth. Reliability Verification (RV) of a design involves verifying that every conducting line in a design meets certain MTTF threshold. In order to perform RV, current density for each wire must be computed. Current itself is a function of the parasitics that are determined through RC extraction. The standard practice is to perform the RC extraction and current density calculation on drawn, pre-OPC layouts. If a wire fails to meet threshold for MTTF, it may be resized. Subsequently, mask preparation steps such as OPC and PSM introduce extra features such as SRAFs, jogs,hammerheads and serifs that change their resistance, capacitance and current density values. Hence, calibrating EM model based on pre-OPC layouts will lead to different results compared to post-OPC layouts. In this work, we compare EM model calibration and reliability check based on drawn layout versus predicted layout, where the drawn layout is pre-OPC layout and predicted layout is based on litho simulation of post-OPC layout. Results show significant divergence between these two approaches, making a case for methodology based on predicted layout.

Multi-dimensional modeling of atmospheric copper-sulfidation corrosion on non-planar substrates.

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

Chen, Ken Shuang

2004-11-01

This report documents the author's efforts in the deterministic modeling of copper-sulfidation corrosion on non-planar substrates such as diodes and electrical connectors. A new framework based on Goma was developed for multi-dimensional modeling of atmospheric copper-sulfidation corrosion on non-planar substrates. In this framework, the moving sulfidation front is explicitly tracked by treating the finite-element mesh as a pseudo solid with an arbitrary Lagrangian-Eulerian formulation and repeatedly performing re-meshing using CUBIT and re-mapping using MAPVAR. Three one-dimensional studies were performed for verifying the framework in asymptotic regimes. Limited model validation was also carried out by comparing computed copper-sulfide thickness with experimentalmore » data. The framework was first demonstrated in modeling one-dimensional copper sulfidation with charge separation. It was found that both the thickness of the space-charge layers and the electrical potential at the sulfidation surface decrease rapidly as the Cu{sub 2}S layer thickens initially but eventually reach equilibrium values as Cu{sub 2}S layer becomes sufficiently thick; it was also found that electroneutrality is a reasonable approximation and that the electro-migration flux may be estimated by using the equilibrium potential difference between the sulfidation and annihilation surfaces when the Cu{sub 2}S layer is sufficiently thick. The framework was then employed to model copper sulfidation in the solid-state-diffusion controlled regime (i.e. stage II sulfidation) on a prototypical diode until a continuous Cu{sub 2}S film was formed on the diode surface. The framework was also applied to model copper sulfidation on an intermittent electrical contact between a gold-plated copper pin and gold-plated copper pad; the presence of Cu{sub 2}S was found to raise the effective electrical resistance drastically. Lastly, future research needs in modeling atmospheric copper sulfidation are discussed.« less

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

Strelcov, Evgheni; Cothren, Joshua E.; Leonard, Donovan N.

Progress in rational engineering of Li-ion batteries requires better understanding of the electrochemical processes and accompanying transformations in the electrode materials on multiple length scales. In spite of recent progress in utilizing transmission electron microscopy (TEM) to analyze these materials, in situ scanning electron microscopy (SEM) was mostly overlooked as a powerful tool that allows probing these phenomena on the nano and mesoscale. In this paper, we report on in situ SEM study of lithiation in a V 2O 5-based single-nanobelt battery with ionic liquid electrolyte. Coupled with cyclic voltammetry measurements, in situ SEM revealed the peculiarities of subsurface intercalation,more » formation of solid-electrolyte interface (SEI) and electromigration of liquid. We observed that single-crystalline vanadia nanobelts do not undergo large-scale amorphization or fracture during electrochemical cycling, but rather transform topochemically with only a slight shape distortion. Lastly, the SEI layer seems to have significant influence on the lithium ion diffusion and overall capacity of the single-nanobelt battery.« less

Use of solar cell in electrokinetic remediation of cadmium-contaminated soil.

PubMed

Yuan, Songhu; Zheng, Zhonghua; Chen, Jing; Lu, Xiaohua

2009-03-15

This preliminary study used a solar cell, instead of direct current (DC) power supply, to generate electric field for electrokinetic (EK) remediation of cadmium-contaminated soil. Three EK tests were conducted and compared; one was conducted on a cloudy and rainy day with solar cell, one was conducted on a sunny day with solar cell and another was conducted periodically with DC power supply. It was found that the output potential of solar cell depended on daytime and was influenced by weather conditions; the applied potential in soil was affected by the output potential and weather conditions, and the current achieved by solar cell was comparable with that achieved by DC power supply. Solar cell could be used to drive the electromigration of cadmium in contaminated soil, and removal efficiency achieved by solar cell was comparable with that achieved by DC power supply. Compared with traditional DC power supply, using solar cell as power supply for EK remediation can greatly reduce energy expenditure. This study provided an alternative to improve the EK soil remediation and expanded the use of solar cell in environmental remediation.

Model creation of moving redox reaction boundary in agarose gel electrophoresis by traditional potassium permanganate method.

PubMed

Xie, Hai-Yang; Liu, Qian; Li, Jia-Hao; Fan, Liu-Yin; Cao, Cheng-Xi

2013-02-21

A novel moving redox reaction boundary (MRRB) model was developed for studying electrophoretic behaviors of analytes involving redox reaction on the principle of moving reaction boundary (MRB). Traditional potassium permanganate method was used to create the boundary model in agarose gel electrophoresis because of the rapid reaction rate associated with MnO(4)(-) ions and Fe(2+) ions. MRB velocity equation was proposed to describe the general functional relationship between velocity of moving redox reaction boundary (V(MRRB)) and concentration of reactant, and can be extrapolated to similar MRB techniques. Parameters affecting the redox reaction boundary were investigated in detail. Under the selected conditions, good linear relationship between boundary movement distance and time were obtained. The potential application of MRRB in electromigration redox reaction titration was performed in two different concentration levels. The precision of the V(MRRB) was studied and the relative standard deviations were below 8.1%, illustrating the good repeatability achieved in this experiment. The proposed MRRB model enriches the MRB theory and also provides a feasible realization of manual control of redox reaction process in electrophoretic analysis.

In situ SEM Study of Lithium Intercalation in individual V 2O 5 Nanowires

DOE PAGES

Strelcov, Evgheni; Cothren, Joshua E.; Leonard, Donovan N.; ...

2015-01-08

Progress in rational engineering of Li-ion batteries requires better understanding of the electrochemical processes and accompanying transformations in the electrode materials on multiple length scales. In spite of recent progress in utilizing transmission electron microscopy (TEM) to analyze these materials, in situ scanning electron microscopy (SEM) was mostly overlooked as a powerful tool that allows probing these phenomena on the nano and mesoscale. In this paper, we report on in situ SEM study of lithiation in a V 2O 5-based single-nanobelt battery with ionic liquid electrolyte. Coupled with cyclic voltammetry measurements, in situ SEM revealed the peculiarities of subsurface intercalation,more » formation of solid-electrolyte interface (SEI) and electromigration of liquid. We observed that single-crystalline vanadia nanobelts do not undergo large-scale amorphization or fracture during electrochemical cycling, but rather transform topochemically with only a slight shape distortion. Lastly, the SEI layer seems to have significant influence on the lithium ion diffusion and overall capacity of the single-nanobelt battery.« less

The Reciprocal Principle of Selectand-Selector-Systems in Supramolecular Chromatography †.

PubMed

Schurig, Volker

2016-11-15

In selective chromatography and electromigration methods, supramolecular recognition of selectands and selectors is due to the fast and reversible formation of association complexes governed by thermodynamics. Whereas the selectand molecules to be separated are always present in the mobile phase, the selector employed for the separation of the selectands is either part of the stationary phase or is added to the mobile phase. By the reciprocal principle, the roles of selector and selectand can be reversed. In this contribution in honor of Professor Stig Allenmark, the evolution of the reciprocal principle in chromatography is reviewed and its advantages and limitations are outlined. Various reciprocal scenarios, including library approaches, are discussed in efforts to optimize selectivity in separation science.

Very High Output Thermoelectric Devices Based on ITO Nanocomposites

NASA Technical Reports Server (NTRS)

Fralick, Gustave; Gregory, Otto J.

2009-01-01

A material having useful thermoelectric properties was synthesized by combining indium-tin-oxide (ITO) with a NiCoCrAlY alloy/alumina cermet. This material had a very large Seebeck coefficient with electromotive-force-versustemperature behavior that is considered to be excellent with respect to utility in thermocouples and other thermoelectric devices. When deposited in thin-film form, ceramic thermocouples offer advantages over precious-metal (based, variously, on platinum or rhodium) thermocouples that are typically used in gas turbines. Ceramic thermocouples exhibit high melting temperatures, chemical stability at high temperatures, and little or no electromigration. Oxide ceramics also resist oxidation better than metal thermocouples, cost substantially less than precious-metal thermocouples, and, unlike precious-metal thermocouples, do not exert catalytic effects.

Effect of Al-trace dimension on Joule heating and current crowding in flip-chip solder joints under accelerated electromigration

NASA Astrophysics Data System (ADS)

Liang, S. W.; Chang, Y. W.; Chen, Chih

2006-04-01

Three-dimensional thermoelectrical simulation was conducted to investigate the influence of Al-trace dimension on Joule heating and current crowding in flip-chip solder joints. It is found that the dimension of the Al-trace effects significantly on the Joule heating, and thus directly determines the mean time to failure (MTTF). Simulated at a stressing current of 0.6A at 70°C, we estimate that the MTTF of the joints with Al traces in 100μm width was 6.1 times longer than that of joints with Al traces in 34μm width. Lower current crowding effect and reduced hot-spot temperature are responsible for the improved MTTF.

Recent applications of nanomaterials in capillary electrophoresis.

PubMed

González-Curbelo, Miguel Ángel; Varela-Martínez, Diana Angélica; Socas-Rodríguez, Bárbara; Hernández-Borges, Javier

2017-10-01

Nanomaterials have found an important place in Analytical Chemistry and, in particular, in Separation Science. Among them, metal-organic frameworks, magnetic and non-magnetic nanoparticles, carbon nanotubes and graphene, as well as their combinations, are the most important nanomaterials that have been used up to now. Concerning capillary electromigration techniques, these nanomaterials have also been used as both pseudostationary phases in electrokinetic chromatography (EKC) and as stationary phases in microchip capillary electrophoresis (CE) and capillary electrochromatography (CEC), as a result of their interesting and particular properties. This review article pretends to provide a general and critical revision of the most recent applications of nanomaterials in this field (period 2010-2017). © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Holographic investigation of silver electromigration in nano-sized As2S3 films

NASA Astrophysics Data System (ADS)

Sainov, S.; Todorov, R.; Bodurov, I.; Yovcheva, Temenuzhka

2013-10-01

Holographic gratings with a diffraction efficiency (DE) greater than 8% and a spatial resolution of 2237 mm-1 are recorded in very thin As2S3 films with a thickness of 100 nm. Silver photo-diffusion is observed during the holographic recording process while applying a corona discharge. We use the method of holographic grating relaxation spectroscopy (forced Rayleigh scattering) based on the evanescent waves to determine that the silver diffusion coefficient in the thin As2S3 film is in the range of (0.9-10.3) × 10-13 cm2 s-1 depending on the corona charge polarity. This work is dedicated to the 90th anniversary of the birth of Academician Jordan Malinowski.

Chiral drug analysis using mass spectrometric detection relevant to research and practice in clinical and forensic toxicology.

PubMed

Schwaninger, Andrea E; Meyer, Markus R; Maurer, Hans H

2012-12-21

This paper reviews analytical approaches published in 2002-2012 for chiral drug analysis and their relevance in research and practice in the field of clinical and forensic toxicology. Separation systems such as gas chromatography, high performance liquid chromatography, capillary electromigration, and supercritical fluid chromatography, all coupled to mass spectrometry, are discussed. Typical applications are reviewed for relevant chiral analytes such as amphetamines and amphetamine-derived designer drugs, methadone, tramadol, psychotropic and other CNS acting drugs, anticoagulants, cardiovascular drugs, and some other drugs. Usefulness of chiral drug analysis in the interpretation of analytical results in clinical and forensic toxicology is discussed as well. Copyright © 2012 Elsevier B.V. All rights reserved.

Electrotransport and diffusivity of molybdenum, rhenium, tungsten, and zirconium in beta-thorium

NASA Technical Reports Server (NTRS)

Schmidt, F. A.; Beck, M. S.; Rehbein, D. K.; Conzemius, R. J.; Carlson, O. N.

1984-01-01

The electric mobilities, diffusivities, and effective valences were determined for molybdenum, rhenium, tungsten, and zirconium in beta-thorium. All four solutes migrated in the same direction as the electron flow. Rhenium and molybdenum were found to be very mobile, with tungsten somewhat slower. Zirconium was found to move at a rate near that of the self-diffusion of beta-thorium, viz., about 10 to the -11th sq m/s at 1500 C. The electromigration velocities showed a similar trend. A comparison was made between experimental data obtained by scanning laser mass spectrometry and theoretical transport equations for two purification experiments. Good agreement was obtained with both the concentration profile predicted by DeGroot and the purification ratio predicted by Verhoeven.

Electrical Characterization of Thin Film Cadmium Telluride Electrodeposited from Tri-N Telluride

NASA Astrophysics Data System (ADS)

von Windheim, Jesko A.

The electrical transport properties of CdTe electrodeposited from tri-n-butylphosphine telluride have been studied by resistivity and Hall effect measurements. Methods have been developed to reproducibly remove large area samples from their conducting substrates, and these samples were prepared for temperature dependent Hall measurements and resistivity measurements. Apparatus was designed and built to routinely measure Hall voltages as low as 250 muV for source impedances up to 10 ^{12} Omega. The central aspect of the measurement system was a low cost, differential electrometer amplifier designed around the AD549L monolithic electrometer operational amplifier. Temperature control was achieved via a Eurotherm 808 temperature controller, and a cooled stream of nitrogen gas. With this system, temperature could be maintained within +/- 0.5^circC at set points between -40^circC and +40^circC. Data collection, temperature ramping, and power to the magnet were all computer controlled, and resistivity measurements were fully automated. As-annealed electrodeposited CdTe was found to be consistently p-type, with resistivity values typically 10^6- 10^{7 } Omega-cm. Various donor and acceptor dopants have been incorporated into polycrystalline CdTe films by three methods: electrochemical codeposition, electromigration and vapour techniques. The dopants were Cd, Te, Cu, Ag, In, and O_2. The activity of the dopant was dependent on the method that was used for incorporation. Oxygen was found to only have a significant effect when it was incorporated in situ, during deposition. For Cd and Te, on the other hand, little effect was seen when their concentration was varied in situ. However, hole concentration increased substantially when Te was incorporated by diffusion, and a p to n conversion was observed when Cd was incorporated by diffusion. The carrier concentration of p-type CdTe could be systematically increased by increasing the current density for the electromigration of copper. The decreasing carrier concentration was accompanied by a decrease in resistivity and a decrease in mobility. The effect of dopant density on the resistivity of the polycrystalline cadmium telluride films, deposited from tri-n-butylphosphine telluride, can consistently be described by a grain boundary model. In this model charging of grain boundary states results in a barrier and can affect the carrier density. According to the model, dopants accumulated at grain boundaries do not generate carriers and do not affect the density of interface states.

Biological permeable reactive barriers coupled with electrokinetic soil flushing for the treatment of diesel-polluted clay soil.

PubMed

Mena, Esperanza; Ruiz, Clara; Villaseñor, José; Rodrigo, Manuel A; Cañizares, Pablo

2015-01-01

Removal of diesel from spiked kaolin has been studied in the laboratory using coupled electrokinetic soil flushing (EKSF) and bioremediation through an innovative biological permeable reactive barriers (Bio-PRBs) positioned between electrode wells. The results show that this technology is efficient in the removal of pollutants and allows the soil to maintain the appropriate conditions for microorganism growth in terms of pH, temperature, and nutrients. At the same time, EKSF was demonstrated to be a very interesting technology for transporting pollutants, microorganisms and nutrients, although results indicate that careful management is necessary to avoid the depletion of nutrients, which are effectively transported by electro-migration. After two weeks of operation, 30% of pollutants are removed and energy consumption is under 70 kWh m(-3). Main fluxes (electroosmosis and evaporation) and changes in the most relevant parameters (nutrients, diesel, microorganisms, surfactants, moisture conductivity and pH) during treatment and in a complete post-study analysis are studied to give a comprehensive description of the most relevant processes occurring in the soil (pollutant transport and biodegradation). Copyright © 2014 Elsevier B.V. All rights reserved.

Stereoisomers Separation

NASA Astrophysics Data System (ADS)

Wieczorek, Piotr

The use of capillary electrophoresis for enantiomer separation and optical purity determination is presented. The contents start with basic information about the nature of stereoizomers and the mechanism of enantioseparation using capillary electrophoresis techniques. The molecules to be separated show identical chemical structure and electrochemical behavior. Therefore, the chiral recognition of enantiomers is possible only by bonding to chiral selector and the separation based on very small differences in complexation energies of diastereomer complexes formed. This method is useful for this purpose due to the fact that different compounds can be used as chiral selectors. The mostly used chiral selectors like cyclodextrins, crown ethers, chiral surfactants, macrocyclic antibiotics, transition metal complexes, natural, and synthetic polymers and their application for this purpose is also discussed. Finally, examples of practical applications of electromigration techniques for enantiomers separation and determination are presented.

Electrokinetic mixing vortices due to electrolyte depletion at microchannel junctions.

PubMed

Takhistov, Paul; Duginova, Ksenia; Chang, Hsueh-Chia

2003-07-01

Due to electric field leakage across sharp corners, the irrotational character of Ohmic electroosmotic flow is violated. Instead, we demonstrate experimentally and theoretically evidence of electrolyte depletion and vortex separation in electroosmotic flow around a junction between wide and narrow channels. When the penetration length of the electric field exceeds the width of the narrow channel and if the electric field is directed from the narrow to the wide channel, the electromigration of ions diminishes significantly at the junction end of the narrow channel due to this leakage. Concentration depletion then develops at that location to maintain current balance but it also increases the corner zeta potential and the local electroosmotic slip velocity. A back pressure gradient hence appears to maintain flow balance and, at a sufficient magnitude, generates a pair of vortices.

Removal of fluorine from contaminated soil by electrokinetic treatment driven by solar energy.

PubMed

Zhou, Ming; Zhu, Shufa; Liu, Yana; Wang, Xuejian

2013-08-01

Instead of direct current power supply, a series of electrokinetic remediation experiments driven by solar energy on fluorine-contaminated soil were conducted in a self-made electrolyzer, in order to reduce energy expenditure of electrokinetic remediation. After the 12-day electrokinetic remediation driven by solar energy, the removal efficiency of fluorine was 22.3%, and electrokinetic treatment had an impact on changes in partitioning of fluorine in soil. It proved that the combination of electrokinetics and solar energy was feasible and effective to some extent for the remediation of fluorine-contaminated soil. Meanwhile, the experimental results also indicated that the electromigration was a more dominant transport mechanism for the removal of fluorine from contaminated soil than electroosmosis, and the weather condition was the important factor in affecting the removal efficiency.

Measurement of strain in Al-Cu interconnect lines with x-ray microdiffraction

NASA Astrophysics Data System (ADS)

Solak, H. H.; Vladimirsky, Y.; Cerrina, F.; Lai, B.; Yun, W.; Cai, Z.; Ilinski, P.; Legnini, D.; Rodrigues, W.

1999-07-01

We report measurement of strain in patterned Al-Cu interconnect lines with x-ray microdiffraction technique with a ˜1 μm spatial resolution. Monochromatized x rays from an undulator were focused on the sample using a phase fresnel zone plate and diffracted light was collected by an area detector in a symmetric, angle dispersive x-ray diffraction geometry. Measurements were made before and after the line sample was stressed for electromigration. Results show an increase in inter- and intra-grain strain variation after the testing. Differences in strain behavior of grains with (111) and (200) crystallographic planes parallel to the substrate surface were observed. A position dependent variation of strain after the testing was measured whereas no such dependence was found before the testing.

Ion concentration in micro and nanoscale electrospray emitters.

PubMed

Yuill, Elizabeth M; Baker, Lane A

2018-06-01

Solution-phase ion transport during electrospray has been characterized for nanopipettes, or glass capillaries pulled to nanoscale tip dimensions, and micron-sized electrospray ionization emitters. Direct visualization of charged fluorophores during the electrospray process is used to evaluate impacts of emitter size, ionic strength, analyte size, and pressure-driven flow on heterogeneous ion transport during electrospray. Mass spectrometric measurements of positively- and negatively-charged proteins were taken for micron-sized and nanopipette emitters under low ionic strength conditions to further illustrate a discrepancy in solution-driven transport of charged analytes. A fundamental understanding of analyte electromigration during electrospray, which is not always considered, is expected to provide control over selective analyte depletion and enrichment, and can be harnessed for sample cleanup. Graphical abstract Fluorescence micrographs of ion migration in nanoscale pipettes while solution is electrosprayed.

Quantized conductance observed during sintering of silver nanoparticles by intense terahertz pulses

NASA Astrophysics Data System (ADS)

Takano, Keisuke; Harada, Hirofumi; Yoshimura, Masashi; Nakajima, Makoto

2018-04-01

We show that silver nanoparticles, which are deposited on a terahertz-receiving antenna, can be sintered by intense terahertz pulse irradiation. The conductance of the silver nanoparticles between the antenna electrodes is measured under the terahertz pulse irradiation. The dispersant materials surrounding the nanoparticles are peeled off, and conduction paths are created. We reveal that, during sintering, quantum point contacts are formed, leading to quantized conductance between the electrodes with the conductance quantum, which reflects the formation of atomically thin wires. The terahertz electric pulses are sufficiently intense to activate electromigration, i.e., transfer of kinetic energy from the electrons to the silver atoms. The silver atoms move and atomically thin wires form under the intense terahertz pulse irradiation. These findings may inspire nanoscale structural processing by terahertz pulse irradiation.

A review on solder reflow and flux application for flip chip

NASA Astrophysics Data System (ADS)

Suppiah, Sarveshvaran; Ong, Nestor Rubio; Sauli, Zaliman; Sarukunaselan, Karunavani; Alcain, Jesselyn Barro; Visvanathan, Susthitha Menon; Retnasamy, Vithyacharan

2017-09-01

This paper encompassed of the evolution and key findings, critical technical challenges, solutions and bonding equipment of solder reflow in flip chip bonding. Upon scrutinizing researches done by others, it can be deduced that peak temperature, time above liquidus, soak temperature, soak time, cooling rate and reflow environment played a vital role in achieving the desired bonding profile. In addition, flux is also needed with the purpose of removing oxides/contaminations on bump surface as well as to promote wetting of solder balls. Electromigration and warpage are the two main challenges faced by solder reflow process which can be overcome by the advancement in under bump metallization (UBM) and substrate technology. The review is ended with a brief description of the current equipment used in solder reflow process.

Physics-based simulation of EM and SM in TSV-based 3D IC structures

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

Kteyan, Armen; Sukharev, Valeriy; Zschech, Ehrenfried

2014-06-19

Evolution of stresses in through-silicon-vias (TSVs) and in the TSV landing pad due to the stress migration (SM) and electromigration (EM) phenomena are considered. It is shown that an initial stress distribution existing in a TSV depends on its architecture and copper fill technology. We demonstrate that in the case of proper copper annealing the SM-induced redistribution of atoms results in uniform distributions of the hydrostatic stress and concentration of vacancies along each segment. In this case, applied EM stressing generates atom migration that is characterized by kinetics depending on the preexisting equilibrium concentration of vacancies. Stress-induced voiding in TSVmore » is considered. EM induced voiding in TSV landing pad is analyzed in details.« less

The Influence of Impurities and Metallic Capping Layers on the Microstructure of Copper Interconnects

NASA Astrophysics Data System (ADS)

Rizzolo, Michael

As copper interconnects have scaled to ever smaller dimensions on semiconductor devices, the microstructure has become increasingly detrimental for performance and reliability. Small grains persist in interconnects despite annealing at high temperatures, leading to higher line resistance and more frequent electromigration-induced failures. Conventionally, it was believed that impurities from the electrodeposition pinned grain growth, but limitations in analytical techniques meant the effect was inferred rather than observed. Recent advances in analytical techniques, however, have enabled this work to quantify impurity content, location, and diffusion in relation to microstructural changes in electroplated copper. Surface segregation of impurities during the initial burst of grain growth was investigated. After no surface segregation was observed, a microfluidic plating cell was constructed to plate multilayer films with regions of intentionally high and low impurity concentrations to determine if grain growth could be pinned by the presence of impurities; it was not. An alternate mechanism for grain boundary pinning based on the texture of the seed layer is proposed, supported by time-resolved transmission electron microscopy and transmission electron backscatter diffraction data. The suggested model posits that the seed in narrow features has no preferred orientation, which results in rapid nucleation of subsurface grains in trench regions prior to recrystallization from the overburden down. These rapidly growing grains are able to block off several trenches from the larger overburden grains, inhibiting grain growth in narrow features. With this knowledge in hand, metallic capping layers were employed to address the problematic microstructure in 70nm lines. The capping layers (chromium, nickel, zinc, and tin) were plated on the copper overburden prior to annealing to manipulate the stress gradient and microstructural development during annealing. It appeared that regardless of as-plated stress, nickel capping altered the recrystallized texture of the copper over patterned features. The nickel capping also caused a 2x increase in the number of advantageous 'bamboo' grains that span the entire trench, which effectively block electromigration pathways. These data provides a more fundamental understanding of manipulating the microstructure in copper interconnects using pre-anneal capping layers, and demonstrates a strategy to improve the microstructure beyond the capabilities of simple annealing.

Assisting cultivation of photosynthetic microorganisms by microbial fuel cells to enhance nutrients recovery from wastewater.

PubMed

Colombo, Alessandra; Marzorati, Stefania; Lucchini, Giorgio; Cristiani, Pierangela; Pant, Deepak; Schievano, Andrea

2017-08-01

Spirulina was cultivated in cathodic compartments of photo-microbial fuel cells (P-MFC). Anodic compartments were fed with swine-farming wastewater, enriched with sodium acetate (2.34g COD L -1 ). Photosynthetic oxygen generation rates were sufficient to sustain cathodic oxygen reduction, significantly improving P-MFC electrochemical performances, as compared to water-cathode control experiments. Power densities (0.8-1Wm -2 ) approached those of air-cathode MFCs, run as control. COD was efficiently removed and only negligible fractions leaked to the cathodic chamber. Spirulina growth rates were comparable to those of control (MFC-free) cultures, while pH was significantly (0.5-1unit) higher in P-MFCs, due to cathodic reactions. Alkaliphilic photosynthetic microorganisms like Spirulina might take advantage of these selective conditions. Electro-migration along with diffusion to the cathodic compartment concurred for the recovery of most nutrients. Only P and Mg were retained in the anodic chamber. A deeper look into electro-osmotic mechanisms should be addressed in future studies. Copyright © 2017 Elsevier Ltd. All rights reserved.

Computational and experimental model of transdermal iontophorethic drug delivery system.

PubMed

Filipovic, Nenad; Saveljic, Igor; Rac, Vladislav; Graells, Beatriz Olalde; Bijelic, Goran

2017-11-30

The concept of iontophoresis is often applied to increase the transdermal transport of drugs and other bioactive agents into the skin or other tissues. It is a non-invasive drug delivery method which involves electromigration and electroosmosis in addition to diffusion and is shown to be a viable alternative to conventional administration routs such as oral, hypodermic and intravenous injection. In this study we investigated, experimentally and numerically, in vitro drug delivery of dexamethasone sodium phosphate to porcine skin. Different current densities, delivery durations and drug loads were investigated experimentally and introduced as boundary conditions for numerical simulations. Nernst-Planck equation was used for calculation of active substance flux through equivalent model of homogeneous hydrogel and skin layers. The obtained numerical results were in good agreement with experimental observations. A comprehensive in-silico platform, which includes appropriate numerical tools for fitting, could contribute to iontophoretic drug-delivery devices design and correct dosage and drug clearance profiles as well as to perform much faster in-silico experiments to better determine parameters and performance criteria of iontophoretic drug delivery. Copyright © 2017 Elsevier B.V. All rights reserved.

Exploring the Electrical Conductivity of Cytochrome P450 by Nano-Electrode and Conductive Atomic Force Microscopy

NASA Astrophysics Data System (ADS)

Li, Debin; Gu, Jianhua; Chye, Yewhee; Lederman, David; Kabulski, Jarod; Gannett, Peter; Tracy, Timothy

2006-03-01

There is a growing interest in measuring the conductivity of electron-transfer proteins. The cytochrome P450 (CP450) enzymes represent an important class of heme-containing enzymes. Immobilizing CP450 enzymes on a surface can be used for studying a single enzyme with respect to electron transfer. The spin state of the heme iron can change upon binding of a substrate. In our experiment, CP450 (diameter ˜ 5 nm) has been bonded to a metal surface. Nano-electrodes (gap < 10 nm) were fabricated by defining a bridge via e-beam lithography and then breaking the junction by electromigration at low temperatures. We have examined the electronic properties of CP450 by itself and after binding CP450 with flurbiprofen. The room temperature I-V conductivity is reminiscent to cyclic voltammetry measurements, indicating the presence of strong ionic transfer. At lower temperatures (100 K) the I-V characteristics indicate electronic transport dominated by tunneling processes. The conductive AFM is an additional method used to examine the enzyme's electronic properties. The results from two methods will be discussed..

Microstructural changes in a cementitious membrane due to the application of a DC electric field.

PubMed

Covelo, Alba; Diaz, Belen; Freire, Lorena; Novoa, X Ramon; Perez, M Consuelo

2008-07-01

The use of electromigration techniques to accelerate chloride ions motion is commonly employed to characterise the permeability of cementitious samples to chlorides, a relevant parameter in reinforced concrete corrosion. This paper is devoted to the study of microstructure's changes occurring in mortar samples when submitted to natural diffusion and migration experiments. The application of an electric field reduces testing time in about one order of magnitude with respect to natural diffusion experiments. Nevertheless, the final sample's microstructure differs in both tests. Impedance Spectroscopy is employed for real time monitoring of microstructural changes. During migration experiments the global impedance undergoes important increase in shorter period of time compared to natural diffusion tests. So, the forced motion of ions through the concrete membrane induces significant variations in the porous structure, as confirmed by Mercury Intrusion Porosimetry. After migration experiments, an important increase in the capillary pore size (10-100 nm) was detected. Conversely, no relevant variations are found after natural diffusion tests. Results presented in this work cast doubt on the significance of diffusion coefficient values obtained under accelerated conditions.

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

Bauer, R.; Ebersberger, B.; Kupfer, C.

SnAg solder bump is one bump type which is used to replace eutectic SnPb bumps. In this work tests have been done to characterize the reliability properties of this bump type. Electromigration (EM) tests, which were accelerated by high current and high temperature and high temperature storage (HTS) tests were performed. It was found that the reliability properties are sensitive to the material combinations in the interconnect stack. The interconnect stack includes substrate pad, pad finish, bump, underbump metallization (UBM) and the chip pad. Therefore separate test groups for SnAg bumps on Cu substrate pads with organic solderability preservative (OSP)more » finish and the identical bumps on pads with Ni/Au finish were used. In this paper the reliability test results and the corresponding failure analysis are presented. Some explanations about the differences in formation of intermetallic compounds (IMCs) are given.« less

Corrosion Propagation of Rebar Embedded in High Performance Concrete

NASA Astrophysics Data System (ADS)

Nazim, Manzurul

The FDOT has been using supplementary cementitious materials while constructing steel reinforced concrete marine bridge structures for over 3 decades. Previous findings indicated that such additions in concrete mix make the concrete more durable. To better understand corrosion propagation of rebar in high performance concrete: mature concrete samples that were made (2008/2009) with Portland cement, a binary mix, a ternary mix and recently prepared (April 2016 with 50% OPC + 50% slag and 80% OPC + 20% Fly ash) concrete samples were considered. None of these concretes had any admixed chloride to start with. An accelerated chloride transport process was used to drive chloride ions into the concrete so that chlorides reach and exceed the chloride threshold at the rebar surface and initiate corrosion. Electrochemical measurements were taken at regular intervals (during and after the electro-migration process) to observe the corrosion propagation in each sample.

Auger compositional depth profiling of the metal contact-TlBr interface

NASA Astrophysics Data System (ADS)

Nelson, A. J.; Swanberg, E. L.; Voss, L. F.; Graff, R. T.; Conway, A. M.; Nikolic, R. J.; Payne, S. A.; Kim, H.; Cirignano, L.; Shah, K.

2015-08-01

Degradation of room temperature operation of TlBr radiation detectors with time is thought to be due to electromigration of Tl and Br vacancies within the crystal as well as the metal contacts migrating into the TlBr crystal itself due to electrochemical reactions at the metal/TlBr interface. Scanning Auger electron spectroscopy (AES) in combination with sputter depth profiling was used to investigate the metal contact surface/interfacial structure on TlBr devices. Device-grade TlBr was polished and subjected to a 32% HCl etch to remove surface damage and create a TlBr1-xClx surface layer prior to metal contact deposition. Auger compositional depth profiling results reveal non-equilibrium interfacial diffusion after device operation in both air and N2 at ambient temperature. These results improve our understanding of contact/device degradation versus operating environment for further enhancing radiation detector performance.

Laterally configured resistive switching device based on transition-metal nano-gap electrode on Gd oxide

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

Kawakita, Masatoshi; Okabe, Kyota; Kimura, Takashi

2016-01-11

We have developed a fabrication process for a laterally configured resistive switching device based on a Gd oxide. A nano-gap electrode connected by a Gd oxide with the ideal interfaces has been created by adapting the electro-migration method in a metal/GdO{sub x} bilayer system. Bipolar set and reset operations have been clearly observed in the Pt/GdO{sub x} system similarly in the vertical device based on GdO{sub x}. Interestingly, we were able to observe a clear bipolar switching also in a ferromagnetic CoFeB nano-gap electrode with better stability compared to the Pt/GdO{sub x} device. The superior performance of the CoFeB/GdO{sub x}more » device implies the importance of the spin on the resistive switching.« less

Electrokinetic remediation of inorganic and organic pollutants in textile effluent contaminated agricultural soil.

PubMed

Annamalai, Sivasankar; Santhanam, Manikandan; Sundaram, Maruthamuthu; Curras, Marta Pazos

2014-12-01

The discharge from the dyeing industries constitutes unfixed dyes, inorganic salts, heavy metal complexes etc., which spoil the surrounding areas of industrial sites. The present article reports the use of direct current electrokinetic technique for the treatment of textile contaminated soil. Impressed direct current voltage of 20 V facilitates the dye/metal ions movement in the naturally available dye contaminated soil towards the opposite electrode by electromigration. IrO2–RuO2–TiO2/Ti was used as anode and Ti used as cathode. UV–Visible spectrum reveals that higher dye intensity was nearer to the anode. Ni, Cr and Pb migration towards the cathode and migration of Cu, SO42− and Cl− towards anode were noticed. Chemical oxygen demand in soil significantly decreased upon employing electrokinetic. This technology may be exploited for faster and eco-friendly removal of dye in soil environment.

Analysis of pilocarpine and its trans epimer, isopilocarpine, by capillary electrophoresis.

PubMed

Baeyens, W; Weiss, G; Van Der Weken, G; Van Den Bossche, W

1993-05-28

Capillary zone electrophoresis was used for the separation of pilocarpine from its epimer, isopilocarpine, using coated fused-silica capillaries of 20 cm x 25 microm I.D., 8 kV running voltage, migration buffer of 0.1 M sodium dihydrogenphosphate pH 8, detection at 217 nm and injection by electromigration. Injections of aqueous, acid and basic solutions were compared. Linearity of the signal for pilocarpine hydrochloride up to 200 microg ml(-1) in 0.05 M hydrochloric acid was obtained, using naphazoline nitrate as internal standard. Optimization of migration buffer pH using coated silica capillaries of 50 cm x 50 microm I.D. showed that at pH 6.9 pilocarpine can be separated from ++isopilocarpine. Inclusion of beta-cyclodextrin in the buffer allows full baseline separation of both epimers. The method was applied to the analysis of a commercial ophthalmic pilocarpine solution.

Accelerated reliability testing of highly aligned single-walled carbon nanotube networks subjected to DC electrical stressing.

PubMed

Strus, Mark C; Chiaramonti, Ann N; Kim, Young Lae; Jung, Yung Joon; Keller, Robert R

2011-07-01

We investigate the electrical reliability of nanoscale lines of highly aligned, networked, metallic/semiconducting single-walled carbon nanotubes (SWCNTs) fabricated through a template-based fluidic assembly process. We find that these SWCNT networks can withstand DC current densities larger than 10 MA cm(-2) for several hours and, in some cases, several days. We develop test methods that show that the degradation rate, failure predictability and total device lifetime can be linked to the initial resistance. Scanning electron and transmission electron microscopy suggest that fabrication variability plays a critical role in the rate of degradation, and we offer an empirical method of quickly determining the long-term performance of a network. We find that well-fabricated lines subject to constant electrical stress show a linear accumulation of damage reminiscent of electromigration in metallic interconnects, and we explore the underlying physical mechanisms that could cause such behavior.

Electroepitaxy of multicomponent systems - Ternary and quarternary compounds

NASA Technical Reports Server (NTRS)

Bryskiewicz, T.; Lagowski, J.; Gatos, H. C.

1980-01-01

A theoretical model is presented which accounts for the electroepitaxial growth kinetics and composition of multicomponent compounds in terms of mass transport in the liquid and phase diagram relationships. The mass transport in the interface is dominated by electromigration in the absence of convection and by diffusion in the presence of convection. The composition of the solid is controlled by the Peltier effect at the growth interface and by the diffusion and mobility constants of the solute components and the growth velocity (current density). Thus, for a given solution composition, the composition of the solid can be varied by varying the current density. For a given current density the composition remains constant even in the case of relatively thick epitaxial layers. All aspects of the model were found to be in good agreement with the growth and composition characteristics of Ga/x-1/Al/x/As layers.

Potential Electrokinetic Remediation Technologies of Laboratory Scale into Field Application- Methodology Overview

NASA Astrophysics Data System (ADS)

Ayuni Suied, Anis; Tajudin, Saiful Azhar Ahmad; Nizam Zakaria, Muhammad; Madun, Aziman

2018-04-01

Heavy metal in soil possesses high contribution towards soil contamination which causes to unbalance ecosystem. There are many ways and procedures to make the electrokinetic remediation (EKR) method to be efficient, effective, and potential as a low cost soil treatment. Electrode compartment for electrolyte is expected to treat the contaminated soil through electromigration and enhance metal ions movement. The electrokinetic is applicable for many approaches such as electrokinetic remediation (EKR), electrokinetic stabilization (EKS), electrokinetic bioremediation and many more. This paper presents a critical review on comparison of laboratory scale between EKR, EKS and EK bioremediation treatment by removing the heavy metal contaminants. It is expected to propose one framework of contaminated soil mapping. Electrical Resistivity Method (ERM) is one of famous indirect geophysical tools for surface mapping and subsurface profiling. Hence, ERM is used to mapping the migration of heavy metal ions by electrokinetic.

Epitaxial nickel disilicide with low resistivity and excellent reliability.

PubMed

Hsin, Cheng-Lun; Deng, Shiu-Sheng

2016-02-12

Ultra-thin epitaxial NiSi2 was formed, and its structure was examined by electron microscopy and x-ray diffraction. Compared with previous reports, the measured resistivity of the epitaxial NiSi2 was unprecedentedly low, reaching 7 μΩ cm in the experimental results and up to 14.93 μΩ cm after modification. The reliability, which was investigated under different temperatures and current densities to understand its electronic characteristics, was 1.5 times better than that of the conventional polycrystalline counterpart. Black's equation and the measured mean-time-to-failure (MTTF) were used to obtain the reliability characteristics of epitaxial and poly-NiSi2. Confidence intervals at 95% for each MTTF confirmed the single failure mode. The electromigration phenomenon was observed to be the failure mechanism. Our results provide evidence that epitaxial NiSi2 is a promising contact material for future electronics.

Epitaxial nickel disilicide with low resistivity and excellent reliability

NASA Astrophysics Data System (ADS)

Hsin, Cheng-Lun; Deng, Shiu-Sheng

2016-02-01

Ultra-thin epitaxial NiSi2 was formed, and its structure was examined by electron microscopy and x-ray diffraction. Compared with previous reports, the measured resistivity of the epitaxial NiSi2 was unprecedentedly low, reaching 7 μΩ cm in the experimental results and up to 14.93 μΩ cm after modification. The reliability, which was investigated under different temperatures and current densities to understand its electronic characteristics, was 1.5 times better than that of the conventional polycrystalline counterpart. Black’s equation and the measured mean-time-to-failure (MTTF) were used to obtain the reliability characteristics of epitaxial and poly-NiSi2. Confidence intervals at 95% for each MTTF confirmed the single failure mode. The electromigration phenomenon was observed to be the failure mechanism. Our results provide evidence that epitaxial NiSi2 is a promising contact material for future electronics.

The effect of an electric field on the morphological stability of the crystal-melt interface of a binary alloy. III - Weakly nonlinear theory

NASA Technical Reports Server (NTRS)

Wheeler, A. A.; Mcfadden, G. B.; Coriell, S. R.; Hurle, D. T. J.

1990-01-01

The effect of a constant electric current on the crystal-melt interface morphology during directional solidification at constant velocity of a binary alloy is considered. A linear temperature field is assumed, and thermoelectric effects and Joule heating are neglected; electromigration and differing electrical conductivities of crystal and melt are taken into account. A two-dimensional weakly nonlinear analysis is carried out to third order in the interface amplitude, resulting in a cubic amplitude equation that describes whether the bifurcation from the planar state is supercritical or subcritical. For wavelengths corresponding to the most dangerous mode of linear theory, the demarcation between supercritical and subcritical behavior is calculated as a function of processing conditions and material parameters. The bifurcation behavior is a sensitive function of the magnitude and direction of the electric current and of the electrical conductivity ratio.

Towards nanoprinting with metals on graphene.

PubMed

Melinte, G; Moldovan, S; Hirlimann, C; Liu, X; Bégin-Colin, S; Bégin, D; Banhart, F; Pham-Huu, C; Ersen, O

2015-08-28

Graphene and carbon nanotubes are envisaged as suitable materials for the fabrication of the new generation of nanoelectronics. The controlled patterning of such nanostructures with metal nanoparticles is conditioned by the transfer between a recipient and the surface to pattern. Electromigration under the impact of an applied voltage stands at the base of printing discrete digits at the nanoscale. Here we report the use of carbon nanotubes as nanoreservoirs for iron nanoparticles transfer on few-layer graphene. An initial Joule-induced annealing is required to ensure the control of the mass transfer with the nanotube acting as a 'pen' for the writing process. By applying a voltage, the tube filled with metal nanoparticles can deposit metal on the surface of the graphene sheet at precise locations. The reverse transfer of nanoparticles from the graphene surface to the nanotube when changing the voltage polarity opens the way for error corrections.

Towards nanoprinting with metals on graphene

NASA Astrophysics Data System (ADS)

Melinte, G.; Moldovan, S.; Hirlimann, C.; Liu, X.; Bégin-Colin, S.; Bégin, D.; Banhart, F.; Pham-Huu, C.; Ersen, O.

2015-08-01

Graphene and carbon nanotubes are envisaged as suitable materials for the fabrication of the new generation of nanoelectronics. The controlled patterning of such nanostructures with metal nanoparticles is conditioned by the transfer between a recipient and the surface to pattern. Electromigration under the impact of an applied voltage stands at the base of printing discrete digits at the nanoscale. Here we report the use of carbon nanotubes as nanoreservoirs for iron nanoparticles transfer on few-layer graphene. An initial Joule-induced annealing is required to ensure the control of the mass transfer with the nanotube acting as a `pen' for the writing process. By applying a voltage, the tube filled with metal nanoparticles can deposit metal on the surface of the graphene sheet at precise locations. The reverse transfer of nanoparticles from the graphene surface to the nanotube when changing the voltage polarity opens the way for error corrections.

Recent advances in combination of capillary electrophoresis with mass spectrometry: methodology and theory.

PubMed

Klepárník, Karel

2015-01-01

This review focuses on the latest development of microseparation electromigration methods in capillaries and microfluidic devices with MS detection and identification. A wide selection of 183 relevant articles covers the literature published from June 2012 till May 2014 as a continuation of the review article on the same topic by Kleparnik [Electrophoresis 2013, 34, 70-86]. Special attention is paid to the new improvements in the theory of instrumentation and methodology of MS interfacing with capillary versions of zone electrophoresis, ITP, and IEF. Ionization methods in MS include ESI, MALDI, and ICP. Although the main attention is paid to the development of instrumentation and methodology, representative examples illustrate also applications in the proteomics, glycomics, metabolomics, biomarker research, forensics, pharmacology, food analysis, and single-cell analysis. The combinations of MS with capillary versions of electrochromatography and micellar electrokinetic chromatography are not included. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Thermal stability, adhesion and electrical studies on (Ti,Zr)N x thin films as low resistive diffusion barriers between Cu and Si

NASA Astrophysics Data System (ADS)

Huang, Cheng-Lin; Lai, Chih-Huang; Tsai, Po-Hao; Kuo, Yu-Lin; Lin, Jing-Cheng; Lee, Chiapyng

2014-05-01

In this study, we investigated the thermal stability, wettability, adhesion and reliability of (Ti,Zr)N x films used as the diffusion barrier between Cu and Si. (Ti,Zr)N x films were prepared by DC reactive magnetron sputtering from a Ti-5 at. % Zr alloy target in N2/Ar gas mixtures. A minimum film resistivity of 59.3 µω cm was obtained at an N2/Ar flow ratio of 2.75, which corresponds to the near stoichiometric composition (N/(Ti,Zr) ratio ˜0.95). The sheet resistance of Cu/(Ti,Zr)N0.95/Si was not significantly increased until annealing above 750°C, indicating good thermal stability. On the other hand, the adhesion energy between Cu and the (Ti,Zr)Nx film was reduced as the N/Ti ratio was increased. To obtain reliable performance on stress-induced-voiding (SIV) and electromigration (EM) tests, we proposed to use (Ti,Zr)/(Ti,Zr)N x /(Ti,Zr) tri-layers. We suggest that the interfacial adhesion between barrier and Cu plays an important role in reliability. The proposed tri-layer structure may be a promising candidate for a barrier, as it exhibits excellent reliability without increasing resistance.

Oxidation/reduction reactions at the metal contact-TlBr interface: an x-ray photoelectron spectroscopy study

NASA Astrophysics Data System (ADS)

Nelson, A. J.; Swanberg, E. L.; Voss, L. F.; Graff, R. T.; Conway, A. M.; Nikolic, R. J.; Payne, S. A.; Kim, H.; Cirignano, L.; Shah, K.

2014-09-01

TlBr radiation detector operation degrades with time at room temperature and is thought to be due to electromigration of Tl and Br vacancies within the crystal as well as the metal contacts migrating into the TlBr crystal itself due to electrochemical reactions at the metal/TlBr interface. X-ray photoemission spectroscopy (XPS) was used to investigate the metal contact surface/interfacial structure on TlBr devices. Device-grade TlBr was polished and subjected to a 32% HCl etch to remove surface damage prior to Mo or Pt contact deposition. High-resolution photoemission measurements on the Tl 4f, Br 3d, Cl 2p, Mo 3d and Pt 4f core lines were used to evaluate surface chemistry and non-equilibrium interfacial diffusion. Results indicate that anion substitution at the TlBr surface due to the HCl etch forms TlBr1-xClx with consequent formation of a shallow heterojunction. In addition, a reduction of Tl1+ to Tl0 is observed at the metal contacts after device operation in both air and N2 at ambient temperature. Understanding contact/device degradation versus operating environment is useful for improving radiation detector performance.

Application of design of experiments for formulation development and mechanistic evaluation of iontophoretic tacrine hydrochloride delivery.

PubMed

Patel, Niketkumar; Jain, Shashank; Madan, Parshotam; Lin, Senshang

2016-11-01

The objective of this investigation is to develop mathematical equation to understand the impact of variables and establish statistical control over transdermal iontophoretic delivery of tacrine hydrochloride. In addition, possibility of using conductivity measurements as a tool of predicting ionic mobility of the participating ions for the application of iontophoretic delivery was explored. Central composite design was applied to study effect of independent variables like current strength, buffer molarity, and drug concentration on iontophoretic tacrine permeation flux. Molar conductivity was determined to evaluate electro-migration of tacrine ions with application of Kohlrausch's law. The developed mathematic equation not only reveals drug concentration as the most significant variable regulating tacrine permeation, followed by current strength and buffer molarity, but also is capable to optimize tacrine permeation with respective combination of independent variables to achieve desired therapeutic plasma concentration of tacrine in treatment of Alzheimer's disease. Moreover, relative higher mobility of sodium and chloride ions was observed as compared to estimated tacrine ion mobility. This investigation utilizes the design of experiment approach and extends the primary understanding of imapct of electronic and formulation variables on the tacrine permeation for the formulation development of iontophoretic tacrine delivery.

Dependence of magnetic field and electronic transport of Mn4 Single-molecule magnet in a Single-Electron Transistor

NASA Astrophysics Data System (ADS)

Rodriguez, Alvar; Singh, Simranjeet; Haque, Firoze; Del Barco, Enrique; Nguyen, Tu; Christou, George

2012-02-01

Dependence of magnetic field and electronic transport of Mn4 Single-molecule magnet in a Single-Electron Transistor A. Rodriguez, S. Singh, F. Haque and E. del Barco Department of Physics, University of Central Florida, 4000 Central Florida Blvd., Orlando, Florida 32816 USA T. Nguyen and G. Christou Department of Chemistry, University of Florida, Gainesville, Florida 32611 USA Abstract We have performed single-electron transport measurements on a series of Mn-based low-nuclearity single-molecule magnets (SMM) observing Coulomb blockade. SMMs with well isolated and low ground spin states, i.e. S = 9/2 (Mn4) and S = 6 (Mn3) were chosen for these studies, such that the ground spin multiplet does not mix with levels of other excited spin states for the magnetic fields (H = 0-8 T) employed in the experiments. Different functionalization groups were employed to change the mechanical, geometrical and transport characteristics of the molecules when deposited from liquid solution on the transistors. Electromigration-broken three-terminal single-electron transistors were used. Results obtained at temperatures down to 240 mK and in the presence of high magnetic fields will be shown.

Surface functional groups in capacitive deionization with porous carbon electrodes

NASA Astrophysics Data System (ADS)

Hemmatifar, Ali; Oyarzun, Diego I.; Palko, James W.; Hawks, Steven A.; Stadermann, Michael; Santiago, Juan G.; Stanford Microfluidics Lab Team; Lawrence Livermore National Lab Team

2017-11-01

Capacitive deionization (CDI) is a promising technology for removal of toxic ions and salt from water. In CDI, an applied potential of about 1 V to pairs of porous electrodes (e.g. activated carbon) induces ion electromigration and electrostatic adsorption at electrode surfaces. Immobile surface functional groups play a critical role in the type and capacity of ion adsorption, and this can dramatically change desalination performance. We here use models and experiments to study weak electrolyte surface groups which protonate and/or depropotante based on their acid/base dissociation constants and local pore pH. Net chemical surface charge and differential capacitance can thus vary during CDI operation. In this work, we present a CDI model based on weak electrolyte acid/base equilibria theory. Our model incorporates preferential cation (anion) adsorption for activated carbon with acidic (basic) surface groups. We validated our model with experiments on custom built CDI cells with a variety of functionalizations. To this end, we varied electrolyte pH and measured adsorption of individual anionic and cationic ions using inductively coupled plasma mass spectrometry (ICP-MS) and ion chromatography (IC) techniques. Our model shows good agreement with experiments and provides a framework useful in the design of CDI control schemes.

Two-dimensional self-organization of an ordered Au silicide nanowire network on a Si(110)-16 x 2 surface.

PubMed

Hong, Ie-Hong; Yen, Shang-Chieh; Lin, Fu-Shiang

2009-08-17

A well-ordered two-dimensional (2D) network consisting of two crossed Au silicide nanowire (NW) arrays is self-organized on a Si(110)-16 x 2 surface by the direct-current heating of approximately 1.5 monolayers of Au on the surface at 1100 K. Such a highly regular crossbar nanomesh exhibits both a perfect long-range spatial order and a high integration density over a mesoscopic area, and these two self-ordering crossed arrays of parallel-aligned NWs have distinctly different sizes and conductivities. NWs are fabricated with widths and pitches as small as approximately 2 and approximately 5 nm, respectively. The difference in the conductivities of two crossed-NW arrays opens up the possibility for their utilization in nanodevices of crossbar architecture. Scanning tunneling microscopy/spectroscopy studies show that the 2D self-organization of this perfect Au silicide nanomesh can be achieved through two different directional electromigrations of Au silicide NWs along different orientations of two nonorthogonal 16 x 2 domains, which are driven by the electrical field of direct-current heating. Prospects for this Au silicide nanomesh are also discussed.

Investigation of the acid-base and electromigration properties of 5-azacytosine derivatives using capillary electrophoresis and density functional theory calculations.

PubMed

Geffertová, Denisa; Ali, Syed Tahir; Šolínová, Veronika; Krečmerová, Marcela; Holý, Antonín; Havlas, Zdeněk; Kašička, Václav

2017-01-06

Capillary electrophoresis (CE) and quantum mechanical density functional theory (DFT) were applied to the investigation of the acid-base and electromigration properties of important compounds: newly synthesized derivatives of 5-azacytosine - analogs of efficient antiviral drug cidofovir. These compounds exhibit a strong antiviral activity and they are considered as potential new antiviral agents. For their characterization and application, it is necessary to know their acid-base properties, particularly the acidity constants (pK a ) of their ionogenic groups (the basic N 3 atom of the triazine ring and the acidic phosphonic acid group in the alkyl chain). First, the mixed acidity constants (pK a mix ) of these ionogenic groups and the ionic mobilities of these compounds were determined by nonlinear regression analysis of the pH dependence of their effective electrophoretic mobilities. Effective mobilities were measured by CE in a series of background electrolytes in a wide pH range (2.0-10.5), at constant ionic strength (25mM) and constant temperature (25°C). Subsequently, the pK a mix values were recalculated to thermodynamic pK a values using the Debye-Hückel theory. The thermodynamic pK a value of the NH + moiety at the N 3 atom of the triazine ring was found to be in the range 2.82-3.30, whereas the pK a of the hydrogenphosphonate group reached values from 7.19 to 7.47, depending on the structure of the analyzed compounds. These experimentally determined pK a values were in good agreement with those calculated by quantum mechanical DFT. In addition, DFT calculations revealed that from the four nitrogen atoms in the 5-azacytosine moiety, the N 3 atom of the triazine ring is preferentially protonated. Effective charges of analyzed compounds ranged from zero or close-to-zero values at pH 2 to -2 elementary charges at pH≥9. Ionic mobilities were in the range (-16.7 to -19.1)×10 -9 m 2 V -1 s -1 for univalent anions and in the interval (-26.9 to -30.3)×10 -9 m 2 V -1 s -1 for divalent anions. Copyright © 2016 Elsevier B.V. All rights reserved.

Growth of large-scale nanotwinned Cu nanowire arrays from anodic aluminum oxide membrane by electrochemical deposition process: controllable nanotwin density and growth orientation with enhanced electrical endurance performance

NASA Astrophysics Data System (ADS)

Chan, Tsung-Cheng; Lin, Yen-Miao; Tsai, Hung-Wei; Wang, Zhiming M.; Liao, Chien-Neng; Chueh, Yu-Lun

2014-06-01

Densely nanotwinned Cu nanowire (NW) arrays with an identical diameter of ~55 nm were fabricated by pulse electrochemical deposition at low temperature using anodic aluminum oxide as a template. Different growth orientations of nanotwinned Cu nanowire arrays were investigated. The endurance of the electrical current density before breakdown of the nanotwinned Cu NWs can reach up to 2.4 × 108 A cm-2. The formation of highly dense nanotwins is attributed to relaxation of coalescence induced stress and twin fault stacking when Cu NWs grow by two-dimensional kinetics. A mechanism based on the twinning structure effect on the electromigration was proposed to explain the improved electrical endurance of Cu. The result demonstrates that the formation of nanotwins into Cu NWs can effectively suppress the void growth, leading to extended life time for use in electronic devices.Densely nanotwinned Cu nanowire (NW) arrays with an identical diameter of ~55 nm were fabricated by pulse electrochemical deposition at low temperature using anodic aluminum oxide as a template. Different growth orientations of nanotwinned Cu nanowire arrays were investigated. The endurance of the electrical current density before breakdown of the nanotwinned Cu NWs can reach up to 2.4 × 108 A cm-2. The formation of highly dense nanotwins is attributed to relaxation of coalescence induced stress and twin fault stacking when Cu NWs grow by two-dimensional kinetics. A mechanism based on the twinning structure effect on the electromigration was proposed to explain the improved electrical endurance of Cu. The result demonstrates that the formation of nanotwins into Cu NWs can effectively suppress the void growth, leading to extended life time for use in electronic devices. Electronic supplementary information (ESI) available: X-ray diffraction spectra of Cu NWs grown by electrochemical deposition with a current density of 1.5 A cm-2 at -1 °C and room temperature; bright-field TEM images of Cu NWs deposited at -1 °C with a current density of 0.4, 0.8, 1.8, and 1.5 A cm-2, respectively; illustration of the effect of twin density on the MTTF of Cu NWs. See DOI: 10.1039/c3nr06194a

Insulation-resistance degradation kinetics of bulk BaTi1-ξAξO3-Δ and defect-chemical origin of acceptor-type(A) and doping-level(ξ) effect

NASA Astrophysics Data System (ADS)

Kwon, Hyung-Soon; Yoon, Seok-Hyun; Yoo, Han-Ill

2016-07-01

Dearth of the reproducible, consistent observations on insulation-resistance (IR) degradation kinetics of bulk dielectric BaTiO3 may be attributed to their conventional measurement method, two-probe potentiostatic, which would be by no means free from the electrode effect for a finite- dimension specimen in particular. We hereby measured the IR-degradation kinetics galvanostatically by using a series of inner probes on bulk BaTi1-ξAξO3-Δ (A = Al, Mn; ξ = 0.001, 0.003, 0.010) with their high-temperature (1000 °C) equilibrium ionic-defect-structure in air being frozen-in at 250 °C and compared with the kinetics as calculated on the basis of the electromigration of frozen-in oxygen vacancies ( cV o ) in association with the A-ionization or hole-trapping equilibria. It has turned out that the calculated depict sufficiently precisely all the as-observed kinetics as well as the effects of acceptor type(A) and doping level(ξ), thus, quantitatively establishing the correlation between the frozen-in ionic-defect-structure and IR-degradation kinetics with new insights into the degradation inner-workings: IR-degradation is triggered as soon as the oxygen vacancy concentration at the cathode reaches that corresponding to the insulator-to-semiconductor transition ( cV S / I ) and proceeds with the front of just-turned, n-type semiconducting region ( c V = cV S / I ) moving towards the anode at a fixed velocity. The healthy lifetime of the dielectric is, thus, essentially the time duration for the cathode to achieve cV S / I from cV o , and the final stage of degradation is approximated to be the length fraction χs of the semiconductor such that χs = cV o / cV S / I . A new suggestion is finally made to further suppress the IR degradation kinetics of the bulk dielectric BaTiO3.

Electromigration of Contaminated Soil by Electro-Bioremediation Technique

NASA Astrophysics Data System (ADS)

Azhar, A. T. S.; Nabila, A. T. A.; Nurshuhaila, M. S.; Shaylinda, M. Z. N.; Azim, M. A. M.

2016-07-01

Soil contamination with heavy metals poses major environmental and human health problems. This problem needs an efficient method and affordable technological solution such as electro-bioremediation technique. The electro-bioremediation technique used in this study is the combination of bacteria and electrokinetic process. The aim of this study is to investigate the effectiveness of Pseudomonas putida bacteria as a biodegradation agent to remediate contaminated soil. 5 kg of kaolin soil was spiked with 5 g of zinc oxide. During this process, the anode reservoir was filled with Pseudomonas putida while the cathode was filled with distilled water for 5 days at 50 V of electrical gradient. The X-Ray Fluorescent (XRF) test indicated that there was a significant reduction of zinc concentration for the soil near the anode with 89% percentage removal. The bacteria count is high near the anode which is 1.3x107 cfu/gww whereas the bacteria count at the middle and near the cathode was 5.0x106 cfu/gww and 8.0x106 cfu/gww respectively. The migration of ions to the opposite charge of electrodes during the electrokinetic process resulted from the reduction of zinc. The results obtained proved that the electro-bioremediation reduced the level of contaminants in the soil sample. Thus, the electro-bioremediation technique has the potential to be used in the treatment of contaminated soil.

Low power gas sensor array on flexible acetate substrate

NASA Astrophysics Data System (ADS)

Benedict, Samatha; Basu, Palash Kumar; Bhat, Navakanta

2017-07-01

In this paper, we present a novel approach of fabricating a low-cost and low power gas sensor array on flexible acetate sheets for sensing CO, SO2, H2 and NO2 gases. The array has four sensor elements with an integrated microheater which can be individually controlled enabling the monitoring of four gases. The thermal properties of the microheater characterized by IR imaging are presented. The microheater with an active area of 15 µm  ×  5 µm reaches a temperature of 300 °C, consuming 2 mW power, the lowest reported on flexible substrates. A sensing electrode is patterned on top of the microheater, and a nanogap (100 nm) is created by an electromigration process. This nanogap is bridged by four sensing materials doped with platinum, deposited using a solution dispensing technique. The sensing material characterization is completed using energy dispersive x-ray analysis. The sensing characteristics of ZnO for CO, V2O5 for SO2, SnO2 for H2 and WO3 for NO2 gases are studied at different microheater voltages. The sensing characteristics of ZnO at different bending angles is also studied, which shows that the microheater and the sensing material are intact without any breaking upto a bending angle of 20°. The ZnO CO sensor shows sensitivity of 146.2% at 1 ppm with good selectivity.

Application of electrokinetic soil flushing to four herbicides: A comparison.

PubMed

dos Santos, E Vieira; Souza, F; Saez, C; Cañizares, P; Lanza, M R V; Martinez-Huitle, C A; Rodrigo, M A

2016-06-01

In this work, four bench-scale plants containing soil spiked with four herbicides (2,4-Dichlorophenoxyacetic acid (2,4-D), oxyfluorfen, chlorsulfuron and atrazine) undergo treatment consisting of an electrokinetic soil flushing (EKSF). Results clearly demonstrate that efficiency of EKSF depends on the chemical characteristic of the pesticide used. The amount of pesticide collected in the anode well is more significant than that collected in the cathode wells, indicating that the electromigration is much more important than drainage by electro-osmotic flux for this application. After 15 d of treatment, the 2,4-D is the pesticide most efficiently removed (95% of removal), while chlorsulfuron is the pesticide more resilient to the treatment. Additionally, volatilization was found to be a process of the major significance in the application of electrokinetic techniques to soil polluted with herbicides and because of that it should always be taken into account in the future design of full-scale processes. Copyright © 2016 Elsevier Ltd. All rights reserved.

Cathode Degradation in Thallium Bromide Devices

NASA Astrophysics Data System (ADS)

Datta, Amlan; Motakef, Shariar

2015-06-01

Thallium bromide (TlBr) is a wide bandgap, compound semiconductor with high gamma-ray stopping power and promising physical properties. However, performance degradation and the eventual irreversible failure of TlBr devices can occur rapidly at room temperature, due to “polarization”, caused by the electromigration of Tl+ and Br- ions to the electrical contacts across the device. Using the Accelerated Device Degradation (ADD) experiment, the degradation phenomena in TlBr devices have been visualized and recorded. This paper focuses on “ageing” of the device cathode at various temperatures. ADD is a fast and reliable direct characterization technique that can be used to identify the effects of various growth and post-growth process modifications on device degradation. Using this technique we have identified cathode degradation with the migration of Br- ions and an associated generation and growth of Thallium-rich fractal “ferns” from the cathode. Its effect on the radiation response of the device has also been discussed in this paper. The chemical changes in the cathode were characterized using Energy-dispersive X-ray spectroscopy.

Spectral focusing of broadband silver electroluminescence in nanoscopic FRET-LEDs

NASA Astrophysics Data System (ADS)

Puchert, Robin P.; Steiner, Florian; Plechinger, Gerd; Hofmann, Felix J.; Caspers, Ines; Kirschner, Johanna; Nagler, Philipp; Chernikov, Alexey; Schüller, Christian; Korn, Tobias; Vogelsang, Jan; Bange, Sebastian; Lupton, John M.

2017-07-01

Few inventions have shaped the world like the incandescent bulb. Edison used thermal radiation from ohmically heated conductors, but some noble metals also exhibit 'cold' electroluminescence in percolation films, tunnel diodes, electromigrated nanoparticle aggregates, optical antennas or scanning tunnelling microscopy. The origin of this radiation, which is spectrally broad and depends on applied bias, is controversial given the low radiative yields of electronic transitions. Nanoparticle electroluminescence is particularly intriguing because it involves localized surface-plasmon resonances with large dipole moments. Such plasmons enable very efficient non-radiative fluorescence resonance energy transfer (FRET) coupling to proximal resonant dipole transitions. Here, we demonstrate nanoscopic FRET-light-emitting diodes which exploit the opposite process, energy transfer from silver nanoparticles to exfoliated monolayers of transition-metal dichalcogenides. In diffraction-limited hotspots showing pronounced photon bunching, broadband silver electroluminescence is focused into the narrow excitonic resonance of the atomically thin overlayer. Such devices may offer alternatives to conventional nano-light-emitting diodes in on-chip optical interconnects.

A Sinusoidal Applied Electric Potential can Induce a Long-Range, Steady Electrophoretic Force

NASA Astrophysics Data System (ADS)

Amrei, Seyyed Hashemi; Ristenpart, William D.; Miller, Greg R.

2017-11-01

We use the standard electrokinetic model to numerically investigate the electric field in aqueous solutions between parallel electrodes under AC polarization. In contrast to prior work, we invoke no simplifying assumptions regarding the applied voltage, frequency, or mismatch in ionic mobilities. We find that the nonlinear electromigration terms significantly contribute to the overall shape of the electric potential vs. time, which at sufficiently high applied potentials develops multi-modal peaks. More surprisingly, we find that electrolytes with non-equal mobilities yield an electric field with non-zero time average at large distances from the electrodes. Our calculations indicate this long-range electric field suffices to levitate colloidal particles many microns away from the electrode against the gravitational field, in accord with experimental observations of such behavior (Woehl et al., PRX, 2015). Moreover, the results indicate that particles will aggregate laterally near electrodes in some electrolytes but separate in others, helping explain a longstanding but not well understood phenomenon.

Membrane rejection of nitrogen compounds

NASA Technical Reports Server (NTRS)

Lee, S.; Lueptow, R. M.

2001-01-01

Rejection characteristics of nitrogen compounds were examined for reverse osmosis, nanofiltration, and low-pressure reverse osmosis membranes. The rejection of nitrogen compounds is explained by integrating experimental results with calculations using the extended Nernst-Planck model coupled with a steric hindrance model. The molecular weight and chemical structure of nitrogen compounds appear to be less important in determining rejection than electrostatic properties. The rejection is greatest when the Donnan potential exceeds 0.05 V or when the ratio of the solute radius to the pore radius is greater than 0.8. The transport of solute in the pore is dominated by diffusion, although convective transport is significant for organic nitrogen compounds. Electromigration contributes negligibly to the overall solute transport in the membrane. Urea, a small organic compound, has lower rejection than ionic compounds such as ammonium, nitrate, and nitrite, indicating the critical role of electrostatic interaction in rejection. This suggests that better treatment efficiency for organic nitrogen compounds can be obtained after ammonification of urea.

Purely electronic mechanism of electrolyte gating of indium tin oxide thin films

DOE PAGES

Leng, X.; Bozovic, I.; Bollinger, A. T.

2016-08-10

Epitaxial indium tin oxide films have been grown on both LaAlO 3 and yttria-stabilized zirconia substrates using RF magnetron sputtering. Electrolyte gating causes a large change in the film resistance that occurs immediately after the gate voltage is applied, and shows no hysteresis during the charging/discharging processes. When two devices are patterned next to one another and the first one gated through an electrolyte, the second one shows no changes in conductance, in contrast to what happens in materials (like tungsten oxide) susceptible to ionic electromigration and intercalation. These findings indicate that electrolyte gating in indium tin oxide triggers amore » pure electronic process (electron depletion or accumulation, depending on the polarity of the gate voltage), with no electrochemical reactions involved. Electron accumulation occurs in a very thin layer near the film surface, which becomes highly conductive. These results contribute to our understanding of the electrolyte gating mechanism in complex oxides and may be relevant for applications of electric double layer transistor devices.« less

Spectral focusing of broadband silver electroluminescence in nanoscopic FRET-LEDs.

PubMed

Puchert, Robin P; Steiner, Florian; Plechinger, Gerd; Hofmann, Felix J; Caspers, Ines; Kirschner, Johanna; Nagler, Philipp; Chernikov, Alexey; Schüller, Christian; Korn, Tobias; Vogelsang, Jan; Bange, Sebastian; Lupton, John M

2017-07-01

Few inventions have shaped the world like the incandescent bulb. Edison used thermal radiation from ohmically heated conductors, but some noble metals also exhibit 'cold' electroluminescence in percolation films, tunnel diodes, electromigrated nanoparticle aggregates, optical antennas or scanning tunnelling microscopy. The origin of this radiation, which is spectrally broad and depends on applied bias, is controversial given the low radiative yields of electronic transitions. Nanoparticle electroluminescence is particularly intriguing because it involves localized surface-plasmon resonances with large dipole moments. Such plasmons enable very efficient non-radiative fluorescence resonance energy transfer (FRET) coupling to proximal resonant dipole transitions. Here, we demonstrate nanoscopic FRET-light-emitting diodes which exploit the opposite process, energy transfer from silver nanoparticles to exfoliated monolayers of transition-metal dichalcogenides. In diffraction-limited hotspots showing pronounced photon bunching, broadband silver electroluminescence is focused into the narrow excitonic resonance of the atomically thin overlayer. Such devices may offer alternatives to conventional nano-light-emitting diodes in on-chip optical interconnects.

Magnetic field dependent electronic transport of Mn4 single-molecule magnet.

NASA Astrophysics Data System (ADS)

Haque, F.; Langhirt, M.; Henderson, J. J.; Del Barco, E.; Taguchi, T.; Christou, G.

2010-03-01

We have performed single-electron transport measurements on a Mn4 single-molecule magnet (SMM) in where amino groups were added to electrically protect the magnetic core and to increase the stability of the molecule when deposited on the single-electron transistor (SET) chip. A three-terminal SET with nano-gap electro-migrated gold electrodes and a naturally oxidized Aluminum back gate. Experiments were conducted at temperatures down to 230mK in the presence of high magnetic fields generated by a superconducting vector magnet. Mn4 molecules were deposited from solution to form a mono-layer. The optimum deposition time was determined by AFM analysis on atomically flat gold surfaces. We have observed Coulomb blockade an electronic excitations that curve with the magnetic field and present zero-field splitting, which represents evidence of magnetic anisotropy. Level anticrossings and large excitations slopes are associated with the behavior of molecular states with high spin values (S ˜ 9), as expected from Mn4.

Electrodeposition of Au/Ag bimetallic dendrites assisted by Faradaic AC-electroosmosis flow

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

Ji, Jianlong; Li, Pengwei; Sang, Shengbo, E-mail: sbsang@tyut.edu.cn

2014-03-15

Au/Ag bimetallic dendrites were synthesized successfully from the corresponding aqueous solution via the AC electrodeposition method. Both of the morphologies and compositions could be tuned by the electrolyte concentration and AC frequency. The prepared bimetallic dendrites were characterized by scanning electron microscopy (SEM), energy dispersive X-ray spectrometer (EDS), transmission electron microscopy (TEM) and UV–vis spectroscopy. The underlying dendrite growth mechanism was then proposed in the context of the Directed Electrochemical Nanowires Assembly (DENA) models. Owing to the unscreened voltage dropping in the electrolyte bulk, electromigration dominates the species flux process, and cations tend to accumulate in areas with strong electricmore » field intensity, such as electrode edges. Moreover, Faradaic AC-electro-osmosis (ACEO) flow could increase the effective diffusion layer thickness in these areas during the electrochemical reaction, and leads to dendrite growth. Further Micro-Raman observations illustrated that the Au/Ag bimetallic dendrites exhibited pronounced surface-enhanced Raman scattering (SERS) activity, using 4-mercaptopyridine (4-MP) as model molecules.« less

A first-principles analysis of ballistic conductance, grain boundary scattering and vertical resistance in aluminum interconnects

NASA Astrophysics Data System (ADS)

Zhou, Tianji; Lanzillo, Nicholas A.; Bhosale, Prasad; Gall, Daniel; Quon, Roger

2018-05-01

We present an ab initio evaluation of electron scattering mechanisms in Al interconnects from a back-end-of-line (BEOL) perspective. We consider the ballistic conductance as a function of nanowire size, as well as the impact of surface oxidation on electron transport. We also consider several representative twin grain boundaries and calculate the specific resistivity and reflection coefficients for each case. Lastly, we calculate the vertical resistance across the Al/Ta(N)/Al and Cu/Ta(N)/Cu interfaces, which are representative of typical vertical interconnect structures with diffusion barriers. Despite a high ballistic conductance, the calculated specific resistivities at grain boundaries are 70-100% higher in Al than in Cu, and the vertical resistance across Ta(N) diffusion barriers are 60-100% larger for Al than for Cu. These results suggest that in addition to the well-known electromigration limitations in Al interconnects, electron scattering represents a major problem in achieving low interconnect line resistance at fine dimensions.

Apparatus and method for measurement of the mechanical properties and electromigration of thin films

DOEpatents

Maris, Humphrey J.

2001-01-01

A method for characterizing a sample comprising the steps of depositing the sample on a substrate, measuring a first change in optical response of the sample, changing the lateral strain of the sample, measuring a second change in optical response of the sample, comparing the second change in optical response of with the first change in optical response and associating a difference between the second change and the first change in optical response with a property of interest in the sample. The measurement of the first change in optical response is made with the sample having an initial lateral strain. The measurement of the second change in optical response is made after the lateral strain in the sample is changed from the initial lateral strain to a different lateral strain. The second change in optical response is compared to the first change in optical response to find the difference between the second change and the first change.

Apparatus and method for measurement of the mechanical properties and electromigration of thin films

DOEpatents

Maris, Humphrey J.

2000-01-01

A method for characterizing a sample comprising the steps of depositing the sample on a substrate, measuring a first change in optical response of the sample, changing the lateral strain of the sample, measuring a second change in optical response of the sample, comparing the second change in optical response of with the first change in optical response and associating a difference between the second change and the first change in optical response with a property of interest in the sample. The measurement of the first change in optical response is made with the sample having an initial lateral strain. The measurement of the second change in optical response is made after the lateral strain in the sample is changed from the initial lateral strain to a different lateral strain. The second change in optical response is compared to the first change in optical response to find the difference between the second change and the first change.

Recent advances in CE-MS coupling: Instrumentation, methodology, and applications.

PubMed

Týčová, Anna; Ledvina, Vojtěch; Klepárník, Karel

2017-01-01

This review focuses on the latest development of microseparation electromigration methods in capillaries and microfluidic devices coupled with MS for detection and identification of important analytes. It is a continuation of the review article on the same topic by Kleparnik (Electrophoresis 2015, 36, 159-178). A wide selection of 161 relevant articles covers the literature published from June 2014 till May 2016. New improvements in the instrumentation and methodology of MS interfaced with capillary or microfluidic versions of zone electrophoresis, isotachophoresis, and isoelectric focusing are described in detail. The most frequently implemented MS ionization methods include electrospray ionization, matrix-assisted desorption/ionization and inductively coupled plasma ionization. Although the main attention is paid to the development of instrumentation and methodology, representative examples illustrate also applications in the proteomics, glycomics, metabolomics, biomarker research, forensics, pharmacology, food analysis, and single-cell analysis. The combinations of MS with capillary versions of electrochromatography, and micellar electrokinetic chromatography are not included. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

The Stressing Effect of Electromigration from the Maxwell Stress and a Preliminary Mean-Time-to-Failure Analysis

NASA Astrophysics Data System (ADS)

Zhou, Peng

2013-06-01

As temperature increases, it is suggested that atoms on lattice sites serve as dynamic defects and cause a much more homogeneous distribution of the Maxwell stress throughout the crystal lattice compared with that caused by static defects. Though this stressing effect mostly leads to Joule heating, it also results in distortion of the crystal lattice, which leads to a decrease in the activation energy for atomic diffusion and causes enhancements in the phase growth rates at both interfaces of diffusion couples. Due to this stressing effect, the decrease in the activation energy is proportional to a square term of the current density J. A mean-time-to-failure analysis is performed for failure caused by excessive growth of intermediate phases, and a mean-time-to-failure (MTTF) equation is found. This equation appears similar to Black's equation but with an extra exponential term arising from the stressing effect of the crystal lattice.

Nonuniformity of carrier injection and the degradation of blue LEDs

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

Bochkareva, N. I.; Efremov, A. A.; Rebane, Yu. T.

The distribution of electroluminescence (EL) intensity over the area and in the course of time before and after the optical degradation of blue InGaN/GaN LEDs is studied. Current-voltage characteristics have been recorded. It is found that the initially bright luminescence near the region of metallization of the p-contact turns weak after the degradation of an LED. The time delay of {approx}20-40 ns is observed in the distribution of EL intensity over the area of LEDs after their degradation. We suppose that a rise in the excess current after degradation is due to the density increasing of the InGaN/GaN interface statesmore » and the formation of an electrical dipole, which lowers the potential barriers in p-GaN and n-GaN layers. The corresponding increase of capacitance leads to a time delay in the spreading of the injection current and in the distribution of the emission brightness over the area. The lateral nonuniformity of the carrier injection into the quantum, well before and after optical degradation, is attributed to diffusion and electromigration of hydrogen, induced by mechanical stress. The metallization of the p-contact may be the source of mechanical stress.« less

Direct Observation of Halide Migration and its Effect on the Photoluminescence of Methylammonium Lead Bromide Perovskite Single Crystals.

PubMed

Luo, Yanqi; Khoram, Parisa; Brittman, Sarah; Zhu, Zhuoying; Lai, Barry; Ong, Shyue Ping; Garnett, Erik C; Fenning, David P

2017-11-01

Optoelectronic devices based on hybrid perovskites have demonstrated outstanding performance within a few years of intense study. However, commercialization of these devices requires barriers to their development to be overcome, such as their chemical instability under operating conditions. To investigate this instability and its consequences, the electric field applied to single crystals of methylammonium lead bromide (CH 3 NH 3 PbBr 3 ) is varied, and changes are mapped in both their elemental composition and photoluminescence. Synchrotron-based nanoprobe X-ray fluorescence (nano-XRF) with 250 nm resolution reveals quasi-reversible field-assisted halide migration, with corresponding changes in photoluminescence. It is observed that higher local bromide concentration is correlated to superior optoelectronic performance in CH 3 NH 3 PbBr 3 . A lower limit on the electromigration rate is calculated from these experiments and the motion is interpreted as vacancy-mediated migration based on nudged elastic band density functional theory (DFT) simulations. The XRF mapping data provide direct evidence of field-assisted ionic migration in a model hybrid-perovskite thin single crystal, while the link with photoluminescence proves that the halide stoichiometry plays a key role in the optoelectronic properties of the perovskite. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Mechanical integrity of a carbon nanotube/copper-based through-silicon via for 3D integrated circuits: a multi-scale modeling approach.

PubMed

Awad, Ibrahim; Ladani, Leila

2015-12-04

Carbon nanotube (CNT)/copper (Cu) composite material is proposed to replace Cu-based through-silicon vias (TSVs) in micro-electronic packages. The proposed material is believed to offer extraordinary mechanical and electrical properties and the presence of CNTs in Cu is believed to overcome issues associated with miniaturization of Cu interconnects, such as electromigration. This study introduces a multi-scale modeling of the proposed TSV in order to evaluate its mechanical integrity under mechanical and thermo-mechanical loading conditions. Molecular dynamics (MD) simulation was used to determine CNT/Cu interface adhesion properties. A cohesive zone model (CZM) was found to be most appropriate to model the interface adhesion, and CZM parameters at the nanoscale were determined using MD simulation. CZM parameters were then used in the finite element analysis in order to understand the mechanical and thermo-mechanical behavior of composite TSV at micro-scale. From the results, CNT/Cu separation does not take place prior to plastic deformation of Cu in bending, and separation does not take place when standard thermal cycling is applied. Further investigation is recommended in order to alleviate the increased plastic deformation in Cu at the CNT/Cu interface in both loading conditions.

Intermetallic Growth Induced Large-Scale Void Growth and Cracking Failure in Line-Type Cu/Solder/Cu Joints Under Current Stressing

NASA Astrophysics Data System (ADS)

Chen, Zhuo; Tian, Wenya; Li, Junhui; Zhu, Wenhui

2018-04-01

In order to study the electromigration (EM) behavior of solder joints in electronics packaging, especially under high-current and high-temperature working conditions, line-type Cu/solder/Cu butting samples were prepared to observe the microstructural evolution under 1.0 × 104 A/cm2 current stressing. A prominent polarity effect was found such that the Cu6Sn5 intermetallic compound (IMC) layer at the anode side, which thickened linearly with time, was much thicker than that at the cathode side. Compared to the samples subjected to thermal aging at the same temperature of 180°C, EM enhanced the Cu3Sn growth at both the anode and the cathode. Two distinct types of damage were observed after extended duration of current stressing. Back-flow of Cu into Cu3Sn was found at the Cu3Sn/Cu6Sn5 interface of the anode side, causing large voids, while strip cracks developed at the cathode solder/Cu6Sn5 interface, causing a significant increase of joint electrical resistance. With the mass transport characteristics that determine the IMC growth and vacancy accumulation analyzed in detail at each interface, formation mechanisms of the two types of damages are discussed.

Influence of reinforcement mesh configuration for improvement of concrete durability

NASA Astrophysics Data System (ADS)

Pan, Chong-gen; Jin, Wei-liang; Mao, Jiang-hong; Zhang, Hua; Sun, Li-hao; Wei, Dong

2017-10-01

Steel bar in concrete structures under harsh environmental conditions, such as chlorine corrosion, seriously affects its service life. Bidirectional electromigration rehabilitation (BIEM) is a new method of repair technology for reinforced concrete structures in such chloride corrosion environments. By applying the BIEM, chloride ions can be removed from the concrete and the migrating corrosion inhibit can be moved to the steel surface. In conventional engineering, the concrete structure is often configured with a multi-layer steel mesh. However, the effect of the BIEM in such structures has not yet been investigated. In this paper, the relevant simulation test is carried out to study the migration law of chloride ions and the migrating corrosion inhibitor in a concrete specimen with complex steel mesh under different energizing modes. The results show that the efficiency of the BIEM increases 50% in both the monolayer steel mesh and the double-layer steel mesh. By using the single-sided BIEM, 87% of the chloride ions are removed from the steel surface. The different step modes can affect the chloride ion removal. The chloride ions within the range of the reinforcement protective cover are easier to be removed than those in the concrete between the two layers of steel mesh. However, the amount of migrating corrosion inhibitor is larger in the latter circumstances.

A new statistical methodology predicting chip failure probability considering electromigration

NASA Astrophysics Data System (ADS)

Sun, Ted

In this research thesis, we present a new approach to analyze chip reliability subject to electromigration (EM) whose fundamental causes and EM phenomenon happened in different materials are presented in this thesis. This new approach utilizes the statistical nature of EM failure in order to assess overall EM risk. It includes within-die temperature variations from the chip's temperature map extracted by an Electronic Design Automation (EDA) tool to estimate the failure probability of a design. Both the power estimation and thermal analysis are performed in the EDA flow. We first used the traditional EM approach to analyze the design with a single temperature across the entire chip that involves 6 metal and 5 via layers. Next, we used the same traditional approach but with a realistic temperature map. The traditional EM analysis approach and that coupled with a temperature map and the comparison between the results of considering and not considering temperature map are presented in in this research. A comparison between these two results confirms that using a temperature map yields a less pessimistic estimation of the chip's EM risk. Finally, we employed the statistical methodology we developed considering a temperature map and different use-condition voltages and frequencies to estimate the overall failure probability of the chip. The statistical model established considers the scaling work with the usage of traditional Black equation and four major conditions. The statistical result comparisons are within our expectations. The results of this statistical analysis confirm that the chip level failure probability is higher i) at higher use-condition frequencies for all use-condition voltages, and ii) when a single temperature instead of a temperature map across the chip is considered. In this thesis, I start with an overall review on current design types, common flows, and necessary verifications and reliability checking steps used in this IC design industry. Furthermore, the important concepts about "Scripting Automation" which is used in all the integration of using diversified EDA tools in this research work are also described in detail with several examples and my completed coding works are also put in the appendix for your reference. Hopefully, this construction of my thesis will give readers a thorough understanding about my research work from the automation of EDA tools to the statistical data generation, from the nature of EM to the statistical model construction, and the comparisons among the traditional EM analysis and the statistical EM analysis approaches.

Understanding the poor iontophoretic transport of lysozyme across the skin: when high charge and high electrophoretic mobility are not enough.

PubMed

Dubey, S; Kalia, Y N

2014-06-10

The original aim of the study was to investigate the transdermal iontophoretic delivery of lysozyme and to gain further insight into the factors controlling protein electrotransport. Initial experiments were done using porcine skin. Lysozyme transport was quantified by using an activity assay based on the lysis of Micrococcus lysodeikticus and was corrected for the release of endogenous enzyme from the skin during current application. Cumulative iontophoretic permeation of lysozyme during 8h at 0.5mA/cm(2) (0.7mM; pH6) was surprisingly low (5.37±3.46μg/cm(2) in 8h) as compared to electrotransport of cytochrome c (Cyt c) and ribonuclease A (RNase A) under similar conditions (923.0±496.1 and 170.71±92.13μg/cm(2), respectively) - despite its having a higher electrophoretic mobility. The focus of the study then became to understand and explain the causes of its poor iontophoretic transport. Lowering formulation pH to 5 increased histidine protonation in the protein and decreased the ionisation of fixed negative charges in the skin (pI ~4.5) and resulted in a small but statistically significant increase in permeation. Co-iontophoresis of acetaminophen revealed a significant inhibition of electroosmosis; inhibition factors of 12-16 were indicative of strong lysozyme binding to skin. Intriguingly, lidocaine electrotransport, which is due almost exclusively to electromigration, was also decreased (approximately 2.7-fold) following skin pre-treatment by lysozyme iontophoresis (cf. iontophoresis of buffer solution) - suggesting that lysozyme was also able to influence subsequent cation electromigration. In order to elucidate the site of skin binding, different porcine skin models were tested (dermatomed skin with thicknesses of 250 and 750μm, tape-stripped skin and heat-separated dermis). Although no difference was seen between permeation across 250 and 750μm dermatomed skin (13.57±12.20 and 5.37±3.46μg/cm(2), respectively), there was a statistically significant increase across tape-stripped skin and heat-separated dermis (36.86±7.48 and 43.42±13.11μg/cm(2), respectively) - although transport was still much less than that seen across intact skin for Cyt c or RNase A. Furthermore, electroosmotic inhibition factors fell to 2.2 and 1.0 for tape-stripped skin and heat-separated dermis - indicating that lysozyme affected convective solvent flow through interactions with the epidermis and predominantly the stratum corneum. Finally, cation exchange and hydrophobic interaction chromatography confirmed that although lysozyme had greater positive charge than Cyt c or RNase A under the conditions used for iontophoresis, it also possessed the highest surface hydrophobicity, which may have facilitated the interactions with the transport pathways and encouraged aggregation in the skin microenvironment. Thus, high charge and electrophoretic mobility seem to be inadequate descriptors to predict the transdermal iontophoretic transport of proteins whose complex three dimensional structures can facilitate interactions with cutaneous transport pathways. Copyright © 2014 Elsevier B.V. All rights reserved.

Electrical Detection of Cancer Biomarker using Aptamers with Nanogap Break-Junctions

PubMed Central

Ilyas, Azhar; Asghar, Waseem; Allen, Peter B.; Duhon, Holli; Ellington, Andrew D.; Iqbal, Samir M.

2012-01-01

Epidermal Growth Factor Receptor (EGFR) is a cell surface protein overexpressed in cancerous cells. It is known to be the most common oncongene. EGFR concentration also increases in the serum of cancer patients. The detection of small changes in the concentration of EGFR can be critical for early diagnosis, resulting in better treatment and improved survival rate of cancer patients. This article reports an RNA aptamer based approach to selectively capture EGFR protein and an electrical scheme for its detection. Pairs of gold electrodes with nanometer separation were made through confluence of focused ion beam scratching and electromigration. The aptamer was hybridized to a single stranded DNA molecule, which in turn was immobilized on SiO2 surface between the gold nanoelectrodes. The selectivity of the aptamer was demonstrated by using control chips with mutated non–selective aptamer and with no aptamer. Surface functionalization was characterized by optical detection and two orders of magnitude increase in direct current (DC) was measured when selective capture of EGFR occurred. This represents an electronic biosensor for the detection of proteins of interest for medical applications. PMID:22706642

Effects of Pulse Parameters on Weld Microstructure and Mechanical Properties of Extra Pulse Current Aided Laser Welded 2219 Aluminum Alloy Joints.

PubMed

Zhang, Xinge; Li, Liqun; Chen, Yanbin; Yang, Zhaojun; Chen, Yanli; Guo, Xinjian

2017-09-15

In order to expand the application range of laser welding and improve weld quality, an extra pulse current was used to aid laser-welded 2219 aluminum alloy, and the effects of pulse current parameters on the weld microstructure and mechanical properties were investigated. The effect mechanisms of the pulse current interactions with the weld pool were evaluated. The results indicated that the coarse dendritic structure in the weld zone changed to a fine equiaxed structure using an extra pulse current, and the pulse parameters, including medium peak current, relatively high pulse frequency, and low pulse duty ratio benefited to improving the weld structure. The effect mechanisms of the pulse current were mainly ascribed to the magnetic pinch effect, thermal effect, and electromigration effect caused by the pulse current. The effect of the pulse parameters on the mechanical properties of welded joints were consistent with that of the weld microstructure. The tensile strength and elongation of the optimal pulse current-aided laser-welded joint increased by 16.4% and 105%, respectively, compared with autogenous laser welding.

Effects of Pulse Parameters on Weld Microstructure and Mechanical Properties of Extra Pulse Current Aided Laser Welded 2219 Aluminum Alloy Joints

PubMed Central

Zhang, Xinge; Li, Liqun; Chen, Yanbin; Yang, Zhaojun; Chen, Yanli; Guo, Xinjian

2017-01-01

In order to expand the application range of laser welding and improve weld quality, an extra pulse current was used to aid laser-welded 2219 aluminum alloy, and the effects of pulse current parameters on the weld microstructure and mechanical properties were investigated. The effect mechanisms of the pulse current interactions with the weld pool were evaluated. The results indicated that the coarse dendritic structure in the weld zone changed to a fine equiaxed structure using an extra pulse current, and the pulse parameters, including medium peak current, relatively high pulse frequency, and low pulse duty ratio benefited to improving the weld structure. The effect mechanisms of the pulse current were mainly ascribed to the magnetic pinch effect, thermal effect, and electromigration effect caused by the pulse current. The effect of the pulse parameters on the mechanical properties of welded joints were consistent with that of the weld microstructure. The tensile strength and elongation of the optimal pulse current-aided laser-welded joint increased by 16.4% and 105%, respectively, compared with autogenous laser welding. PMID:28914825

Electrical characteristics in reverse electrodialysis using nanoporous membranes

NASA Astrophysics Data System (ADS)

Chanda, Sourayon; Tsai, Peichun Amy

2017-11-01

We experimentally and numerically investigate the effects of concentration difference and flow velocity on sustainable electricity generation and associated fluid dynamics using a single reverse electrodialysis (RED) cell. By exploiting the charge-selective nature of nanoporous interfaces, electrical energy is generated by reverse electrodialysis harnessing chemical Gibbs energy via a salinity gradient. Experimentally, a RED cell was designed with two reservoirs, which are separated by a nanoporous, cation-selective membrane. We injected deionized water through one reservoir, whereas a solution of high salt concentration through the other. The gradient of salt concentration primarily drives the flow in the charged nano-pores, due to the interplay between charge selectivity, diffusion processes, and electro-migration. The current-voltage characteristics of the single RED cell shows a linear current-voltage relationship, similar to an electrochemical cell. The membrane resistance is increased with increasing salt concentration difference and external flow rate. The present experimental work was further analyzed numerically to better understand the detailed electrical and flow fields under different concentration gradients and external flows. NSERC Discovery, Accelerator, and CRC Programs.

On-chip isothermal, chemical cycling polymerase chain reaction (ccPCR)

NASA Astrophysics Data System (ADS)

Persat, Alexandre; Santiago, Juan

2008-11-01

We demonstrate a novel ccPCR technique for microfluidic DNA amplification where temperature is held constant in space and time. The polymerase chain reaction is a platform of choice for biological assays and typically based on a three-step thermal cycling: DNA denaturation, primers annealing and extension by an enzyme. We here demonstrate a novel technique where high concentration chemical denaturants (solvents) denature DNA. We leverage the high electrophoretic mobility of DNA and the electrical neutrality of denaturants to achieve chemical cycling. We focus DNA with isotachophoresis (ITP); a robust electrophoretic preconcentration technique which generates strong electric field gradients and protects the sample from dispersion. We apply a pressure-driven flow to balance electromigration velocity and keep the DNA sample stationary in a microchannel. We drive the DNA through a series of high denaturant concentration zones. DNA denatures at high denaturant concentration. At low denaturant concentration, the enzyme creates complementary strands. DNA reaction kinetics are slower than buffer reactions involved in ITP. We demonstrate successful ccPCR amplification for detection of E. Coli. The ccPCR has the potential for simpler chemistry than traditional PCR.

Capillary electrophoresis and nanomaterials - Part I: Capillary electrophoresis of nanomaterials.

PubMed

Adam, Vojtech; Vaculovicova, Marketa

2017-10-01

Nanomaterials are in analytical science used for a broad range of purposes, covering the area of sample pretreatment as well as separation, detection, and identification of target molecules. This part of the review covers capillary electrophoresis (CE) of nanomaterials and focuses on the application of CE as a method for characterization used during nanomaterial synthesis and modification as well as the monitoring of their properties and interactions with other molecules. The heterogeneity of the nanomaterial family is extremely large. Depending on different definitions of the term Nanomaterial/Nanoparticle, the group may cover metal and polymeric nanoparticles, carbon nanomaterials, liposomes and even dendrimers. Moreover, these nanomaterials are usually subjected to some kind of surface modification or functionalization, which broadens the diversity even more. Not only for purposes of verification of nanomaterial synthesis and batch-to-batch quality check, but also for determination the polydispersity and for functionality characterization on the nanoparticle surface, has CE offered very beneficial capabilities. Finally, the monitoring of interactions between nanomaterials and other (bio)molecules is easily performed by some kind of capillary electromigration technique. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Electromembrane extraction of gonadotropin-releasing hormone agonists from plasma and wastewater samples.

PubMed

Nojavan, Saeed; Bidarmanesh, Tina; Mohammadi, Ali; Yaripour, Saeid

2016-03-01

In the present study, for the first time electromembrane extraction followed by high performance liquid chromatography coupled with ultraviolet detection was optimized and validated for quantification of four gonadotropin-releasing hormone agonist anticancer peptides (alarelin, leuprolide, buserelin and triptorelin) in biological and aqueous samples. The parameters influencing electromigration were investigated and optimized. The membrane consists 95% of 1-octanol and 5% di-(2-ethylhexyl)-phosphate immobilized in the pores of a hollow fiber. A 20 V electrical field was applied to make the analytes migrate from sample solution with pH 7.0, through the supported liquid membrane into an acidic acceptor solution with pH 1.0 which was located inside the lumen of hollow fiber. Extraction recoveries in the range of 49 and 71% within 15 min extraction time were obtained in different biological matrices which resulted in preconcentration factors in the range of 82-118 and satisfactory repeatability (7.1 < RSD% < 19.8). The method offers good linearity (2.0-1000 ng/mL) with estimation of regression coefficient higher than 0.998. The procedure allows very low detection and quantitation limits of 0.2 and 0.6 ng/mL, respectively. Finally, it was applied to determination and quantification of peptides in human plasma and wastewater samples and satisfactory results were yielded. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Electroviscous Effects in Ceramic Nanofiltration Membranes.

PubMed

Farsi, Ali; Boffa, Vittorio; Christensen, Morten Lykkegaard

2015-11-16

Membrane permeability and salt rejection of a γ-alumina nanofiltration membrane were studied and modeled for different salt solutions. Salt rejection was predicted by using the Donnan-steric pore model, in which the extended Nernst-Planck equation was applied to predict ion transport through the pores. The solvent flux was modeled by using the Hagen-Poiseuille equation by introducing electroviscosity instead of bulk viscosity. γ-Alumina particles were used for ζ-potential measurements. The ζ-potential measurements show that monovalent ions did not adsorb on the γ-alumina surface, whereas divalent ions were highly adsorbed. Thus, for divalent ions, the model was modified, owing to pore shrinkage caused by ion adsorption. The ζ-potential lowered the membrane permeability, especially for membranes with a pore radius lower than 3 nm, a ζ-potential higher than 20 mV, and an ionic strength lower than 0.01 m. The rejection model showed that, for a pore radius lower than 3 nm and for solutions with ionic strengths lower than 0.01 m, there is an optimum ζ-potential for rejection, because of the concurrent effects of electromigration and convection. Hence, the model can be used as a prediction tool to optimize membrane perm-selectivity by designing a specific pore size and surface charge for application at specific ionic strengths and pH levels. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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

Guo, Rui; Gao, Liming, E-mail: liming.gao@sjtu.edu.cn; Li, Ming, E-mail: mingli90@sjtu.edu.cn

As the continuous shrinkage of the interconnect line width in microelectronics devices, there is a growing concern about the electromigration (EM) failure of bonding wire. In addition, an innovative Ag–8Au–3Pd alloy wire has shown promise as an economical substitute for gold wire interconnects due to the cost pressure of gold in the last decade. In present study of the Ag–8Au–3Pd alloy wire, the surface diffusion occupied the dominant position during EM failure, and the activation energy was found to be 0.61 eV. In order to reveal the failure mechanism, the cross-sections of the Ag–8Au–3Pd alloy wire during EM were preparedmore » by focused ion beam (FIB) micro-machining for electron backscatter diffraction (EBSD) analysis. The microstructure evolution of the Ag–8Au–3Pd alloy wire was characterized by the grain size and grain boundary. As a result, the EM failure originates in the atom transportation, which causes grain size increasing and atom diffusion on the wire surface. - Highlights: • The activation energy of Ag–8Au–3Pd alloy wire was obtained as 0.61 eV. • During EM, the silver atoms diffused from negative to the positive terminal on the wire surface. • The microstructure (grain size and grain boundary) was characterized by FIB-EBSD. • During EM, the atom transportation was found to cause grain size growth and atom diffusion on the wire surface.« less

Development of a fast capillary electrophoresis method for determination of carbohydrates in honey samples.

PubMed

Rizelio, Viviane Maria; Tenfen, Laura; da Silveira, Roberta; Gonzaga, Luciano Valdemiro; Costa, Ana Carolina Oliveira; Fett, Roseane

2012-05-15

In this study, the determination of fructose, glucose and sucrose by capillary electrophoresis (CE) was investigated. The tendency of the analyte to undergo electromigration dispersion and the buffer capacity were evaluated using the Peakmaster(®) software and considered in the optimization of the background electrolyte, which was composed of 20 mmol L(-1) sorbic acid, 0.2 mmol L(-1) CTAB and 40 mmol L(-1) NaOH at pH 12.2. Under optimal CE conditions, the separation of the substances investigated was achieved in less than 2 min. The detection limits for the three analytes were in the range of 0.022 and 0.029 g L(-1) and precision measurements within 0.62-4.69% were achieved. The proposed methodology was applied in the quantitative analysis by direct injection of in honey samples to determine the main sugars presents. The samples were previously dissolved in deionized water and filtered with no other sample treatment. The mean values for fructose, glucose and sucrose were in the ranges of 33.65-45.46 g 100g(-1), 24.63-35.06 g 100g(-1) and <0.22-1.32 g 100g(-1), respectively. The good analytical performance of the method makes it suitable for implementation in food laboratories for the routine analysis of honey samples. Copyright © 2012 Elsevier B.V. All rights reserved.

Analysis of current-driven oscillatory dynamics of single-layer homoepitaxial islands on crystalline conducting substrates

NASA Astrophysics Data System (ADS)

Dasgupta, Dwaipayan; Kumar, Ashish; Maroudas, Dimitrios

2018-03-01

We report results of a systematic study on the complex oscillatory current-driven dynamics of single-layer homoepitaxial islands on crystalline substrate surfaces and the dependence of this driven dynamical behavior on important physical parameters, including island size, substrate surface orientation, and direction of externally applied electric field. The analysis is based on a nonlinear model of driven island edge morphological evolution that accounts for curvature-driven edge diffusion, edge electromigration, and edge diffusional anisotropy. Using a linear theory of island edge morphological stability, we calculate a critical island size at which the island's equilibrium edge shape becomes unstable, which sets a lower bound for the onset of time-periodic oscillatory dynamical response. Using direct dynamical simulations, we study the edge morphological dynamics of current-driven single-layer islands at larger-than-critical size, and determine the actual island size at which the migrating islands undergo a transition from steady to time-periodic asymptotic states through a subcritical Hopf bifurcation. At the highest symmetry of diffusional anisotropy examined, on {111} surfaces of face-centered cubic crystalline substrates, we find that more complex stable oscillatory states can be reached through period-doubling bifurcation at island sizes larger than those at the Hopf points. We characterize in detail the island morphology and dynamical response at the stable time-periodic asymptotic states, determine the range of stability of these oscillatory states terminated by island breakup, and explain the morphological features of the stable oscillating islands on the basis of linear stability theory.

Stable room-temperature thallium bromide semiconductor radiation detectors

NASA Astrophysics Data System (ADS)

Datta, A.; Fiala, J.; Becla, P.; Motakef, Shariar

2017-10-01

Thallium bromide (TlBr) is a highly efficient ionic semiconductor with excellent radiation detection properties. However, at room temperature, TlBr devices polarize under an applied electric field. This phenomenon not only degrades the charge collection efficiency of the detectors but also promotes chemical reaction of the metal electrodes with bromine, resulting in an unstable electric field and premature failure of the device. This drawback has been crippling the TlBr semiconductor radiation detector technology over the past few decades. In this exhaustive study, this polarization phenomenon has been counteracted using innovative bias polarity switching schemes. Here the highly mobile Br- species, with an estimated electro-diffusion velocity of 10-8 cm/s, face opposing electro-migration forces during every polarity switch. This minimizes the device polarization and availability of Br- ions near the metal electrode. Our results indicate that it is possible to achieve longer device lifetimes spanning more than 17 000 h (five years of 8 × 7 operation) for planar and pixelated radiation detectors using this technique. On the other hand, at constant bias, 2500 h is the longest reported lifetime with most devices less than 1000 h. After testing several biasing switching schemes, it is concluded that the critical bias switching frequency at an applied bias of 1000 V/cm is about 17 μHz. Using this groundbreaking result, it will now be possible to deploy this highly efficient room temperature semiconductor material for field applications in homeland security, medical imaging, and physics research.

New pathway for the formation of metallic cubic phase Ge-Sb-Te compounds induced by an electric current

PubMed Central

Park, Yong-Jin; Cho, Ju-Young; Jeong, Min-Woo; Na, Sekwon; Joo, Young-Chang

2016-01-01

The novel discovery of a current-induced transition from insulator to metal in the crystalline phase of Ge2Sb2Te5 and GeSb4Te7 have been studied by means of a model using line-patterned samples. The resistivity of cubic phase Ge-Sb-Te compound was reduced by an electrical current (~1 MA/cm2), and the final resistivity was determined based on the stress current density, regardless of the initial resistivity and temperature, which indicates that the conductivity of Ge-Sb-Te compound can be modulated by an electrical current. The minimum resistivity of Ge-Sb-Te materials can be achieved at high kinetic rates by applying an electrical current, and the material properties change from insulating to metallic behavior without a phase transition. The current-induced metal transition is more effective in GeSb4Te7 than Ge2Sb2Te5, which depends on the intrinsic vacancy of materials. Electromigration, which is the migration of atoms induced by a momentum transfer from charge carriers, can easily promote the rearrangement of vacancies in the cubic phase of Ge-Sb-Te compound. This behavior differs significantly from thermal annealing, which accompanies a phase transition to the hexagonal phase. This result suggests a new pathway for modulating the electrical conductivity and material properties of chalcogenide materials by applying an electrical current. PMID:26902593

Excitation of propagating spin waves by pure spin current

NASA Astrophysics Data System (ADS)

Demokritov, Sergej

Recently it was demonstrated that pure spin currents can be utilized to excite coherent magnetization dynamics, which enables development of novel magnetic nano-oscillators. Such oscillators do not require electric current flow through the active magnetic layer, which can help to reduce the Joule power dissipation and electromigration. In addition, this allows one to use insulating magnetic materials and provides an unprecedented geometric flexibility. The pure spin currents can be produced by using the spin-Hall effect (SHE). However, SHE devices have a number of shortcomings. In particular, efficient spin Hall materials exhibit a high resistivity, resulting in the shunting of the driving current through the active magnetic layer and a significant Joule heating. These shortcomings can be eliminated in devices that utilize spin current generated by the nonlocal spin-injection (NLSI) mechanism. Here we review our recent studies of excitation of magnetization dynamics and propagating spin waves by using NLSI. We show that NLSI devices exhibit highly-coherent dynamics resulting in the oscillation linewidth of a few MHz at room temperature. Thanks to the geometrical flexibility of the NLSI oscillators, one can utilize dipolar fields in magnetic nano-patterns to convert current-induced localized oscillations into propagating spin waves. The demonstrated systems exhibit efficient and controllable excitation and directional propagation of coherent spin waves characterized by a large decay length. The obtained results open new perspectives for the future-generation electronics using electron spin degree of freedom for transmission and processing of information on the nanoscale.

Structural transitions in electron beam deposited Co-carbonyl suspended nanowires at high electrical current densities.

PubMed

Gazzadi, Gian Carlo; Frabboni, Stefano

2015-01-01

Suspended nanowires (SNWs) have been deposited from Co-carbonyl precursor (Co2(CO)8) by focused electron beam induced deposition (FEBID). The SNWs dimensions are about 30-50 nm in diameter and 600-850 nm in length. The as-deposited material has a nanogranular structure of mixed face-centered cubic (FCC) and hexagonal close-packed (HCP) Co phases, and a composition of 80 atom % Co, 15 atom % O and 5 atom % C, as revealed by transmission electron microscopy (TEM) analysis and by energy-dispersive X-ray (EDX) spectroscopy, respectively. Current (I)-voltage (V) measurements with current densities up to 10(7) A/cm(2) determine different structural transitions in the SNWs, depending on the I-V history. A single measurement with a sudden current burst leads to a polycrystalline FCC Co structure extended over the whole wire. Repeated measurements at increasing currents produce wires with a split structure: one half is polycrystalline FCC Co and the other half is graphitized C. The breakdown current density is found at 2.1 × 10(7) A/cm(2). The role played by resistive heating and electromigration in these transitions is discussed.

Importance of core electrostatic properties on the electrophoresis of a soft particle

NASA Astrophysics Data System (ADS)

De, Simanta; Bhattacharyya, Somnath; Gopmandal, Partha P.

2016-08-01

The impact of the volumetric charged density of the dielectric rigid core on the electrophoresis of a soft particle is analyzed numerically. The volume charge density of the inner core of a soft particle can arise for a dendrimer structure or bacteriophage MS2. We consider the electrokinetic model based on the conservation principles, thus no conditions for Debye length or applied electric field is imposed. The fluid flow equations are coupled with the ion transport equations and the equation for the electric field. The occurrence of the induced nonuniform surface charge density on the outer surface of the inner core leads to a situation different from the existing analysis of a soft particle electrophoresis. The impact of this induced surface charge density together with the double-layer polarization and relaxation due to ion convection and electromigration is analyzed. The dielectric permittivity and the charge density of the core have a significant impact on the particle electrophoresis when the Debye length is in the order of the particle size. We find that by varying the ionic concentration of the electrolyte, the particle can exhibit reversal in its electrophoretic velocity. The role of the polymer layer softness parameter is addressed in the present analysis.

Electrokinetic remediation of manganese and ammonia nitrogen from electrolytic manganese residue.

PubMed

Shu, Jiancheng; Liu, Renlong; Liu, Zuohua; Du, Jun; Tao, Changyuan

2015-10-01

Electrolytic manganese residue (EMR) is a solid waste found in filters after sulphuric acid leaching of manganese carbonate ore, which mainly contains manganese and ammonia nitrogen and seriously damages the ecological environment. This work demonstrated the use of electrokinetic (EK) remediation to remove ammonia nitrogen and manganese from EMR. The transport behavior of manganese and ammonia nitrogen from EMR during electrokinetics, Mn fractionation before and after EK treatment, the relationship between Mn fractionation and transport behavior, as well as the effects of electrolyte and pretreatment solutions on removal efficiency and energy consumption were investigated. The results indicated that the use of H2SO4 and Na2SO4 as electrolytes and pretreatment of EMR with citric acid and KCl can reduce energy consumption, and the removal efficiencies of manganese and ammonia nitrogen were 27.5 and 94.1 %, respectively. In these systems, electromigration and electroosmosis were the main mechanisms of manganese and ammonia nitrogen transport. Moreover, ammonia nitrogen in EMR reached the regulated level, and the concentration of manganese in EMR could be reduced from 455 to 37 mg/L. In general, the electrokinetic remediation of EMR is a promising technology in the future.

Effects of Surface Finishes and Current Stressing on Interfacial Reaction Characteristics of Sn-3.0Ag-0.5Cu Solder Bumps

NASA Astrophysics Data System (ADS)

Kim, Jae-Myeong; Jeong, Myeong-Hyeok; Yoo, Sehoon; Park, Young-Bae

2012-04-01

The effects of surface finishes on the in situ interfacial reaction characteristics of ball grid array (BGA) Sn-3.0Ag-0.5Cu lead-free solder bumps were investigated under annealing and electromigration (EM) test conditions of 130°C to 175°C with 5.0 × 103 A/cm2. During reflow and annealing, (Cu,Ni)6Sn5 intermetallic compound (IMC) formed at the interface of electroless nickel immersion gold (ENIG) finish. In the case of both immersion Sn and organic solderability preservative (OSP) finishes, Cu6Sn5 and Cu3Sn IMCs formed. Overall, the IMC growth velocity of ENIG was much lower than that of the other finishes. The activation energies of total IMCs were found to be 0.52 eV for ENIG, 0.78 eV for immersion Sn, and 0.72 eV for OSP. The ENIG finish appeared to present an effective diffusion barrier between the Cu substrate and the solder, which leads to better EM reliability in comparison with Cu-based pad systems. The failure mechanisms were explored in detail via in situ EM tests.

Measurement of resistance switching dynamics in copper sulfide memristor structures

NASA Astrophysics Data System (ADS)

McCreery, Kaitlin; Olson, Matthew; Teitsworth, Stephen

Resistance switching materials are the subject of current research in large part for their potential to enable novel computing devices and architectures such as resistance random access memories and neuromorphic chips. A common feature of memristive structures is the hysteretic switching between high and low resistance states which is induced by the application of a sufficiently large electric field. Here, we describe a relatively simple wet chemistry process to fabricate Cu2 S / Cu memristive structures with Cu2 S film thickness ranging up to 150 micron. In this case, resistance switching is believed to be mediated by electromigration of Cu ions from the Cu substrate into the Cu2 S film. Hysteretic current-voltage curves are measured and reveal switching voltages of about 0.8 Volts with a relatively large variance and independent of film thickness. In order to gain insight into the dynamics and variability of the switching process, we have measured the time-dependent current response to voltage pulses of varying height and duration with a time resolution of 1 ns. The transient response consists of a deterministic RC component as well as stochastically varying abrupt current steps that occur within a few microseconds of the pulse application.

High power vertical stacked diode laser development using macro-channel water cooling and hard solder bonding technology

NASA Astrophysics Data System (ADS)

Yu, Dongshan; Liang, Xuejie; Wang, Jingwei; Li, Xiaoning; Nie, Zhiqiang; Liu, Xingsheng

2017-02-01

A novel marco channel cooler (MaCC) has been developed for packaging high power diode vertical stacked (HPDL) lasers, which eliminates many of the issues in commercially-available copper micro-channel coolers (MCC). The MaCC coolers, which do not require deionized water as coolant, were carefully designed for compact size and superior thermal dissipation capability. Indium-free packaging technology was adopted throughout product design and fabrication process to minimize the risk of solder electromigration and thermal fatigue at high current density and long pulse width under QCW operation. Single MaCC unit with peak output power of up to 700W/bar at pulse width in microsecond range and 200W/bar at pulse width in millisecond range has been recorded. Characteristic comparison on thermal resistivity, spectrum, near filed and lifetime have been conducted between a MaCC product and its counterpart MCC product. QCW lifetime test (30ms 10Hz, 30% duty cycle) has also been conducted with distilled water as coolant. A vertical 40-MaCC stack product has been fabricated, total output power of 9 kilowatts has been recorded under QCW mode (3ms, 30Hz, 9% duty cycle).

Capillary electromigration separation of proteins and microorganisms dynamically modified by chromophoric nonionogenic surfactant.

PubMed

Horká, Marie; Růzicka, Filip; Holá, Veronika; Kahle, Vladislav; Moravcová, Dana; Slais, Karel

2009-08-15

A chromophoric nonionogenic surfactant poly(ethylene glycol) 3-(2-hydroxy-5-n-octylphenylazo)-benzoate, HOPAB, has been prepared and used as a buffer additive for a dynamic modification of proteins and/or microorganisms including Escherichia coli , Staphylococcus epidermidis (biofilm-positive and biofilm-negative), and the strains of yeast cells Candida albicans and Candida parapsilosis (biofilm-positive and biofilm-negative) during a capillary electrophoresis and a capillary isoelectric focusing (CIEF) with UV detection at 326 nm. Values of isoelectric points of labeled proteins and microorganisms have been calculated using UV-detectable pI markers and have been found comparable with pI of the native compounds. Minimum detectable amount has been assessed lower than picograms of proteins and lower than a hundred cells injected into a separation capillary. The introduced labeling method facilitates CIEF separation of microorganisms from the clinical sample of the infected urine at their clinically important levels in the pH gradient pH range of 2-5 and their subsequent cultivation. At the same time, it has enabled the determination of albumin in human urine as a major clinical marker of urinary tract infections and kidney diseases.

Numerical modelling of electrochemical polarization around charged metallic particles

NASA Astrophysics Data System (ADS)

Bücker, Matthias; Undorf, Sabine; Flores Orozco, Adrián; Kemna, Andreas

2017-04-01

We extend an existing analytical model and carry out numerical simulations to study the polarization process around charged metallic particles immersed in an electrolyte solution. Electro-migration and diffusion processes in the electrolyte are described by the Poisson-Nernst-Planck system of partial differential equations. To model the surface charge density, we consider a time- and frequency-invariant electric potential at the particle surface, which leads to the build-up of a static electrical double layer (EDL). Upon excitation by an external electric field at low frequencies, we observe the superposition of two polarization processes. On the one hand, the induced dipole moment on the metallic particle leads to the accumulation of opposite charges in the electrolyte. This charge polarization corresponds to the long-known response of uncharged metallic particles. On the other hand, the unequal cation and anion concentrations in the EDL give rise to a salinity gradient between the two opposite sides of the metallic particle. The resulting concentration polarization enhances the magnitude of the overall polarization response. Furthermore, we use our numerical model to study the effect of relevant model parameters such as surface charge density and ionic strength of the electrolyte on the resulting spectra of the effective conductivity of the composite model system. Our results do not only give interesting new insight into the time-harmonic variation of electric potential and ion concentrations around charged metallic particle. They are also able to reduce incongruities between earlier model predictions and geophysical field and laboratory measurements. Our model thereby improves the general understanding of IP signatures of metallic particles and represents the next step towards a quantitative interpretation of IP imaging results. Part of this research is funded by the Austrian Federal Ministry of Science, Research and Economy under the Raw Materials Initiative.

E-field induced resistive switch in metal/praseodymium calcium manganite interfaces: A model for future nonvolatile memory devices

NASA Astrophysics Data System (ADS)

Das, Nilanjan

Among the various candidates for non-volatile random access memory (RAM), interfacial resistive switch in Ag/Pr0.7Ca0.3 MnO3 (PCMO) configuration has drawn major attention in recent years due to its potential as a high storage density (˜ terabyte) device. However, the diverse nature of the resistive switch in different systems makes the development of a unifying model for its underlying physics very difficult. This dissertation will address both issues, namely, characterization of switches for device applications and development of a system-independent generic model, in detail. In our work, we have studied the properties electric pulse induced interfacial switch in electrode/PCMO system. A very fast speed ("write speed") of 100 ns, threshold ("programming voltage") as low as 2 V (for micro electrodes), and non-volatility ("data retention") of switched states have been achieved. A clear distinction between fast switch and sub-threshold slow quasistatic-dc switch has been made. Results obtained from time-dependence studies and impedance spectroscopy suggest that defect creation/annihilation, such as broken bonds (under very high field at interface, 107V/cm), is likely the mechanism for the sub-micros fast switching. On the other hand, slow accumulative process, such as electromigration of point defects, are responsible for the subthreshold quasi-dc switch. Scanning probe imaging has revealed the nanoscale inhomogeneity of the switched surfaces, essential for observing a resistive switch. Evolution of such structures has been observed under surface pre-training. Device scalability has been tested by creating reversible modification of surface conductivities with atomic force microscopy, thus creating the "nano-switch" (limited to a region of 10--100 nm).

Molecular Dynamics Simulations of Grain Boundary and Bulk Diffusion in Metals.

NASA Astrophysics Data System (ADS)

Plimpton, Steven James

Diffusion is a microscopic mass transport mechanism that underlies many important macroscopic phenomena affecting the structural, electrical, and mechanical properties of metals. This thesis presents results from atomistic simulation studies of diffusion both in bulk and in the fast diffusion paths known as grain boundaries. Using the principles of molecular dynamics single boundaries are studied and their structure and dynamic properties characterized. In particular, tilt boundary bicrystal and bulk models of fcc Al and bcc alpha-Fe are simulated. Diffusion coefficients and activation energies for atomic motion are calculated for both models and compared to experimental data. The influence of the interatomic pair potential on the diffusion is studied in detail. A universal relation between the melting temperature that a pair potential induces in a simulated bulk model and the potential energy barrier height for atomic hopping is derived and used to correlate results for a wide variety of pair potentials. Using these techniques grain boundary and bulk diffusion coefficients for any fcc material can be estimated from simple static calculations without the need to perform more time-consuming dynamic simulations. The influences of two other factors on grain boundary diffusion are also studied because of the interest of the microelectronics industry in the diffusion related reliability problem known as electromigration. The first factor, known to affect the self diffusion rate of Al, is the presence of Cu impurity atoms in Al tilt boundaries. The bicrystal model for Al is seeded randomly with Cu atoms and a simple hybrid Morse potential used to model the Al-Cu interaction. While some effect due to the Cu is noted, it is concluded that pair potentials are likely an inadequate approximation for the alloy system. The second factor studied is the effect of the boundary orientation angle on the diffusion rate. Symmetric bcc Fe boundaries are relaxed to find optimal structures and their diffusion coefficients calculated. Good agreement is found with the dislocation pipe model for tilt boundary diffusion.

New barrierless copper-alloy film for future applications

NASA Astrophysics Data System (ADS)

Lin, Chon-Hsin Lin

2015-09-01

Since Cu metallization results in a conductivity and an electromigration resistance greater than those of Al, it has become popular for making Si-based interconnects for numerous devices in the field of microelectronics. Following the current trend of miniaturization required for most electronic components, there is a greater need for further size reduction in Si-based devices. The most critical side effect of size reduction is the increase in electronic scattering and resistivity when the barrier-layer thickness is further reduced. To explore advanced Cu-metallization methods and to develop a more economical manufacturing process for Cu-alloy films, the development of Cu materials having better quality and higher thermal stability becomes imperative for the metallization and annealing processes. For this purpose, we first fabricated Cu(GeNx) films and examined their thermal stability and electrical reliability after either cyclic or isothermal annealing. The excellent thermal and electrical properties make these new Cu-alloy films highly promising for applications that require more reliable and inexpensive copper interconnects. In this study, we fabricated Cu alloy films by doping a minute amount of Ge or GeNx, respectively, into the Cu films via barrierless Cu metallization, an inexpensive manufacturing method. Using these newly fabricated alloy films, we were able to eliminate or at least substantially reduce the detrimental interaction between the alloy and the barrierless Si substrate. The Cu(GeNx) films also exhibited high thermal stability, low resistivity and leakage current, and long time-dependent dielectric breakdown (TDDB) lifetimes, making such novel films a candidate for high-quality, economical, and more reliable Cu interconnects.

Ultrafast DNA sequencing on a microchip by a hybrid separation mechanism that gives 600 bases in 6.5 minutes.

PubMed

Fredlake, Christopher P; Hert, Daniel G; Kan, Cheuk-Wai; Chiesl, Thomas N; Root, Brian E; Forster, Ryan E; Barron, Annelise E

2008-01-15

To realize the immense potential of large-scale genomic sequencing after the completion of the second human genome (Venter's), the costs for the complete sequencing of additional genomes must be dramatically reduced. Among the technologies being developed to reduce sequencing costs, microchip electrophoresis is the only new technology ready to produce the long reads most suitable for the de novo sequencing and assembly of large and complex genomes. Compared with the current paradigm of capillary electrophoresis, microchip systems promise to reduce sequencing costs dramatically by increasing throughput, reducing reagent consumption, and integrating the many steps of the sequencing pipeline onto a single platform. Although capillary-based systems require approximately 70 min to deliver approximately 650 bases of contiguous sequence, we report sequencing up to 600 bases in just 6.5 min by microchip electrophoresis with a unique polymer matrix/adsorbed polymer wall coating combination. This represents a two-thirds reduction in sequencing time over any previously published chip sequencing result, with comparable read length and sequence quality. We hypothesize that these ultrafast long reads on chips can be achieved because the combined polymer system engenders a recently discovered "hybrid" mechanism of DNA electromigration, in which DNA molecules alternate rapidly between repeating through the intact polymer network and disrupting network entanglements to drag polymers through the solution, similar to dsDNA dynamics we observe in single-molecule DNA imaging studies. Most importantly, these results reveal the surprisingly powerful ability of microchip electrophoresis to provide ultrafast Sanger sequencing, which will translate to increased system throughput and reduced costs.

Ultrafast DNA sequencing on a microchip by a hybrid separation mechanism that gives 600 bases in 6.5 minutes

PubMed Central

Fredlake, Christopher P.; Hert, Daniel G.; Kan, Cheuk-Wai; Chiesl, Thomas N.; Root, Brian E.; Forster, Ryan E.; Barron, Annelise E.

2008-01-01

To realize the immense potential of large-scale genomic sequencing after the completion of the second human genome (Venter's), the costs for the complete sequencing of additional genomes must be dramatically reduced. Among the technologies being developed to reduce sequencing costs, microchip electrophoresis is the only new technology ready to produce the long reads most suitable for the de novo sequencing and assembly of large and complex genomes. Compared with the current paradigm of capillary electrophoresis, microchip systems promise to reduce sequencing costs dramatically by increasing throughput, reducing reagent consumption, and integrating the many steps of the sequencing pipeline onto a single platform. Although capillary-based systems require ≈70 min to deliver ≈650 bases of contiguous sequence, we report sequencing up to 600 bases in just 6.5 min by microchip electrophoresis with a unique polymer matrix/adsorbed polymer wall coating combination. This represents a two-thirds reduction in sequencing time over any previously published chip sequencing result, with comparable read length and sequence quality. We hypothesize that these ultrafast long reads on chips can be achieved because the combined polymer system engenders a recently discovered “hybrid” mechanism of DNA electromigration, in which DNA molecules alternate rapidly between reptating through the intact polymer network and disrupting network entanglements to drag polymers through the solution, similar to dsDNA dynamics we observe in single-molecule DNA imaging studies. Most importantly, these results reveal the surprisingly powerful ability of microchip electrophoresis to provide ultrafast Sanger sequencing, which will translate to increased system throughput and reduced costs. PMID:18184818

Desalination and hydrogen, chlorine, and sodium hydroxide production via electrophoretic ion exchange and precipitation.

PubMed

Shkolnikov, Viktor; Bahga, Supreet S; Santiago, Juan G

2012-08-28

We demonstrate and analyze a novel desalination method which works by electrophoretically replacing sodium and chloride in feed salt water with a pair of ions, calcium and carbonate, that react and precipitate out. The resulting calcium carbonate precipitate is benign to health, and can be filtered or settled out, yielding low ionic strength product water. The ion exchange and precipitation employs self-sharpening interfaces induced by movement of multiple ions in an electric field to prevent contamination of the product water. Simultaneously, the electrolysis associated with the electromigration produces hydrogen gas, chlorine gas, and sodium hydroxide. We conducted an experimental study of this method's basic efficacy to desalinate salt water from 100 to 600 mol m(-3) sodium chloride. We also present physicochemical models of the process, and analyze replacement reagents consumption, permeate recovery ratio, and energy consumption. We hypothesize that the precipitate can be recycled back to replacement reagents using the well-known, commercially implemented Solvay process. We show that the method's permeate recovery ratio is 58% to 46%, which is on par with that of reverse osmosis. We show that the method's energy consumption requirement over and above that necessary to generate electrolysis is 3 to 10 W h l(-1), which is on par with the energy consumed by state-of-the-art desalination methods. Furthermore, the method operates at ambient temperature and pressure, and uses no specialized membranes. The process may be feasible as a part of a desalination-co-generation facility: generating fresh water, hydrogen and chlorine gas, and sodium hydroxide.

Monitoring exocytosis and release from individual mast cells by capillary electrophoresis and UV imaging microscopy

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

Yeung, E.S.; Lillard, S.J.; McCloskey, M.A.

1997-12-31

The complex temporal evolution of on-column exocytotic release of serotonin from individual peritoneal mast cells (RPMCs) was monitored by using capillary electrophoresis and UV imaging microscopy. Laser-induced native fluorescence detection with 275-nm excitation was used, and a detection limit of 1.7 amol (S/N = 3; rms) was obtained for serotonin. A physiological running buffer was used to ensure that the cell remained viable throughout. The secretagogue was polymyxin B sulfate (Pmx). Following the injection of a single mast cell into the capillary, electromigration of Pmx toward and past the cell induced degranulation and release of serotonin. The time course ofmore » release was registered in the electropherograms with subsecond resolution. Subsequent introduction of SDS caused the cell to lyse completely and allowed the residual serotonin to be quantified. The average amount of serotonin observed per RPMC was 1.6 {+-} 0.6 fmol; the average percentage of serotonin released was 28 {+-} 14%. Events that are consistent with released serontonin from single submicron granules (250 aL each) were evident, each of which contained an average amount of 5.9 {+-} 3 amol. Alternatively, UV movies can be taken of the entire event to provide temporal and spatial information.« less

Conceptual design and experiments of electrochemistry-flushing technology for the remediation of historically Cr(Ⅵ)-contaminated soil.

PubMed

Li, Dong; Sun, Delin; Hu, Siyang; Hu, Jing; Yuan, Xingzhong

2016-02-01

A conceptual design and experiments, electrochemistry-flushing (E-flushing), using electrochemistry to enhance flushing efficiency for the remediation of Cr(Ⅵ)-contaminated soil is presented. The rector contained three compartments vertically superposed. The upper was airtight cathode compartment containing an iron-cathode. The middle was soil layer. The bottom was anode compartment containing an iron-anode and connected to a container by circulation pumps. H2 and OH(-) ions were produced at cathode. H2 increased the gas pressure in cathode compartment and drove flushing solution into soil layer forming flushing process. OH(-) ions entered into soil layer by eletromigration and hydraulic flow to enhance the desorption of Cr(Ⅵ). High potential gradient was applied to accelerate the electromigration of desorbed Cr(Ⅵ) ions and produced joule heat to increase soil temperature to enhance Cr(Ⅵ) desorption. In anode compartment, Fe(2+) ions produced at iron-anode reduced the desorbed Cr(Ⅵ) into Cr(3+) ions, which reacted with OH(-) ions forming Cr(OH)3. Experimental results show that Cr(Ⅵ) removal efficiency of E-flushing experiments was more than double of flushing experiments and reached the maximum of removal efficiency determined by desorption kinetics. All electrochemistry processes were positively used in E-flushing technology. Copyright © 2015 Elsevier Ltd. All rights reserved.

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

Li, Menglu; Tu, K. N., E-mail: kntu@ucla.edu; Kim, Dong Wook

Thermal-crosstalk induced thermomigration failure in un-powered microbumps has been found in 2.5D integrated circuit (IC) circuit. In 2.5D IC, a Si interposer was used between a polymer substrate and a device chip which has transistors. The interposer has no transistors. If transistors are added to the interposer chip, it becomes 3D IC. In our test structure, there are two Si chips placed horizontally on a Si interposer. The vertical connections between the interposer and the Si chips are through microbumps. We powered one daisy chain of the microbumps under one Si chip; however, the un-powered microbumps in the neighboring chipmore » are failed with big holes in the solder layer. We find that Joule heating from the powered microbumps is transferred horizontally to the bottom of the neighboring un-powered microbumps, and creates a large temperature gradient, in the order of 1000 °C/cm, through the un-powered microbumps in the neighboring chip, so the latter failed by thermomigration. In addition, we used synchrotron radiation tomography to compare three sets of microbumps in the test structure: microbumps under electromigration, microbumps under thermomigration, and microbumps under a constant temperature thermal annealing. The results show that the microbumps under thermomigration have the largest damage. Furthermore, simulation of temperature distribution in the test structure supports the finding of thermomigration.« less

High power vertical stacked and horizontal arrayed diode laser bar development based on insulation micro-channel cooling (IMCC) and hard solder bonding technology

NASA Astrophysics Data System (ADS)

Wang, Boxue; Jia, Yangtao; Zhang, Haoyu; Jia, Shiyin; Liu, Jindou; Wang, Weifeng; Liu, Xingsheng

2018-02-01

An insulation micro-channel cooling (IMCC) has been developed for packaging high power bar-based vertical stack and horizontal array diode lasers, which eliminates many issues caused in its congener packaged by commercial copper formed micro-channel cooler(MCC), such as coefficient of thermal expansion (CTE) mismatch between cooler and diode laser bar, high coolant quality requirement (DI water) and channel corrosion and electro-corrosion induced by DI water if the DI-water quality is not well maintained The IMCC cooler separates water flow route and electrical route, which allows tap-water as coolant without electro-corrosion and therefore prolongs cooler lifetime dramatically and escalated the reliability of these diode lasers. The thickness of ceramic and copper in an IMCC cooler is well designed to minimize the CTE mismatch between laser bar and cooler, consequently, a very low "SMILE" of the laser bar can be achieved for small fast axis divergence after collimation. In additional, gold-tin hard solder bonding technology was also developed to minimize the risk of solder electromigration at high current density and thermal fatigue under hard-pulse operation mode. Testing results of IMCC packaged diode lasers are presented in this report.

Modeling and experimental characterization of electromigration in interconnect trees

NASA Astrophysics Data System (ADS)

Thompson, C. V.; Hau-Riege, S. P.; Andleigh, V. K.

1999-11-01

Most modeling and experimental characterization of interconnect reliability is focussed on simple straight lines terminating at pads or vias. However, laid-out integrated circuits often have interconnects with junctions and wide-to-narrow transitions. In carrying out circuit-level reliability assessments it is important to be able to assess the reliability of these more complex shapes, generally referred to as `trees.' An interconnect tree consists of continuously connected high-conductivity metal within one layer of metallization. Trees terminate at diffusion barriers at vias and contacts, and, in the general case, can have more than one terminating branch when they include junctions. We have extended the understanding of `immortality' demonstrated and analyzed for straight stud-to-stud lines, to trees of arbitrary complexity. This leads to a hierarchical approach for identifying immortal trees for specific circuit layouts and models for operation. To complete a circuit-level-reliability analysis, it is also necessary to estimate the lifetimes of the mortal trees. We have developed simulation tools that allow modeling of stress evolution and failure in arbitrarily complex trees. We are testing our models and simulations through comparisons with experiments on simple trees, such as lines broken into two segments with different currents in each segment. Models, simulations and early experimental results on the reliability of interconnect trees are shown to be consistent.

A review of combinations of electrokinetic applications.

PubMed

Moghadam, Mohamad Jamali; Moayedi, Hossein; Sadeghi, Masoud Mirmohamad; Hajiannia, Alborz

2016-12-01

Anthropogenic activities contaminate many lands and underground waters with dangerous materials. Although polluted soils occupy small parts of the land, the risk they pose to plants, animals, humans, and groundwater is too high. Remediation technologies have been used for many years in order to mitigate pollution or remove pollutants from soils. However, there are some deficiencies in the remediation in complex site conditions such as low permeability and complex composition of some clays or heterogeneous subsurface conditions. Electrokinetic is an effective method in which electrodes are embedded in polluted soil, usually vertically but in some cases horizontally, and a low direct current voltage gradient is applied between the electrodes. The electric gradient initiates movement of contaminants by electromigration (charged chemical movement), electro-osmosis (movement of fluid), electrolysis (chemical reactions due to the electric field), and diffusion. However, sites that are contaminated with heavy metals or mixed contaminants (e.g. a combination of organic compounds with heavy metals and/or radionuclides) are difficult to remediate. There is no technology that can achieve the best results, but combining electrokinetic with other remediation methods, such as bioremediation and geosynthetics, promises to be the most effective method so far. This review focuses on the factors that affect electrokinetic remediation and the state-of-the-art methods that can be combined with electrokinetic.

Partially Ionized Beam Deposition of Silicon-Dioxide and Aluminum Thin Films - Defects Generation.

NASA Astrophysics Data System (ADS)

Wong, Justin Wai-Chow

1987-09-01

Detect formation in SiO_2 and Al thin films and interfaces were studied using a partially ionized beam (PIB) deposition technique. The evaporated species (the deposition material) were partially ionized to give an ion/atom ratio of <=q0.1% and the substrate was biased at 0-5kV during the deposition. The results suggest that due to the ion bombardment, stoichiometric SiO_2 films can be deposited at a low substrate temperature (~300 ^circC) and low oxygen pressure (<=q10^{-4} Torr). Such deposition cannot be achieved using conventional evaporation-deposition techniques. However, traps and mobile ions were observed in the oxide and local melt-down was observed when a sufficiently high electric field was applied to the film. For the PIB Al deposition on the Si substrate, stable Al/Si Schottky contact was formed when the substrate bias was <=q1kV. For a substrate bias of 2.5kV, the capacitance of the Al/Si interface increased dramatically. A model of self-ion implantation with a p-n junction created by the Al^+ ion implantation was proposed and tested to explain the increase of the interface capacitance. Several deep level states at the Al/Si interface were observed using Deep Level Transient Spectroscopy (DLTS) technique when the film was deposited at a bias of 3kV. The PIB Al films deposited on the Si substrate showed unusually strong electromigration resistance under high current density operation. This phenomenon was explained by the highly oriented microstructure of the Al films created by the self-ion bombardment during deposition. These findings show that PIB has potential applications in a number of areas, including low temperature thin film deposition, and epitaxial growth of thin films in the microelectronics thin film industry.

In Situ Bioremediation of Chlorinated Ethenes in Hydraulically-Tight Sediments: Challenges and Limitations

NASA Astrophysics Data System (ADS)

Zhang, M.; Yoshikawa, M.; Takeuchi, M.; Komai, T.

2011-12-01

Chlorinated ethenes, like perchloroethene (PCE) and trichloroethene (TCE), have been widely used by many industries, especially in developed countries like Japan. Because of their wide applications, lack of proper regulation, poor handing, storage and disposal practices in the past, chlorinated ethenes have become a type of the most prevalent contaminants for soils and groundwater pollution. For the sake of their degradability, bioremediation has been considered as a potentially cost-effective and environmentally friendly approach for cleanup of chlorinated ethenes in situ. In this presentation, we briefly overview the status of soil and groundwater pollution, the recent amendment of the Soil Contamination Countermeasures Act in Japan, comparison between the bioremediation and other techniques like pump and treat, and the mechanisms of reductive dechlorination, direct oxidation and co-metabolism of chlorinated ethenes. We then introduce and discuss some recent challenges and advancements in in-situ bioremediation including technologies for accelerating bio-degradation of chlorinated ethenes, technologies for assessing diffusive properties of dissolved hydrogen in hydraulically-tight soil samples, and combination of bioremediation with other techniques like electro-kinetic approach. Limiting factors that may cause incomplete remediation and/or ineffectiveness of bioremediation are examined from biochemical, geochemical and hydro-geological aspects. This study reconfirmed and illustrated that: 1) The key factor for an effective bioremediation is how to disperse a proper accelerating agent throughout the polluted strata, 2) The effective diffusion coefficient of dissolved hydrogen in geologic media is relatively big and is almost independent on their permeability, and 3) To effectively design and perform an accelerated bioremediation, a combination of natural migration with pressurized injection and/or other approaches, like electro-migration, for stimulating mass transport could be necessary depending on the hydraulic properties, like porosity and permeability of a stratum.

Potassium Sodium Niobate-Based Lead-Free Piezoelectric Multilayer Ceramics Co-Fired with Nickel Electrodes.

PubMed

Kawada, Shinichiro; Hayashi, Hiroyuki; Ishii, Hideki; Kimura, Masahiko; Ando, Akira; Omiya, Suetake; Kubodera, Noriyuki

2015-11-03

Although lead-free piezoelectric ceramics have been extensively studied, many problems must still be overcome before they are suitable for practical use. One of the main problems is fabricating a multilayer structure, and one solution attracting growing interest is the use of lead-free multilayer piezoelectric ceramics. The paper reviews work that has been done by the authors on lead-free alkali niobate-based multilayer piezoelectric ceramics co-fired with nickel inner electrodes. Nickel inner electrodes have many advantages, such as high electromigration resistance, high interfacial strength with ceramics, and greater cost effectiveness than silver palladium inner electrodes. However, widely used lead zirconate titanate-based ceramics cannot be co-fired with nickel inner electrodes, and silver palladium inner electrodes are usually used for lead zirconate titanate-based piezoelectric ceramics. A possible alternative is lead-free ceramics co-fired with nickel inner electrodes. We have thus been developing lead-free alkali niobate-based multilayer ceramics co-fired with nickel inner electrodes. The normalized electric-field-induced thickness strain ( S max / E max ) of a representative alkali niobate-based multilayer ceramic structure with nickel inner electrodes was 360 pm/V, where S max denotes the maximum strain and E max denotes the maximum electric field. This value is about half that for the lead zirconate titanate-based ceramics that are widely used. However, a comparable value can be obtained by stacking more ceramic layers with smaller thicknesses. In the paper, the compositional design and process used to co-fire lead-free ceramics with nickel inner electrodes are introduced, and their piezoelectric properties and reliabilities are shown. Recent advances are introduced, and future development is discussed.

Mobilization of phenol and dichlorophenol in unsaturated soils by non-uniform electrokinetics.

PubMed

Luo, Qishi; Zhang, Xihui; Wang, Hui; Qian, Yi

2005-06-01

The poor mobility of organic pollutants in contaminated sites frequently results in slow remediation processes. Organics, especially hydrophobic compounds, are generally retained strongly in soil matrix as a result of sorption, sequestration, or even formation into non-aqueous-phase liquids and their mobility is thus greatly reduced. The objective of this study was to evaluate the feasibility of using non-uniform electrokinetic transport processes to enhance the mobility of organic pollutants in unsaturated soils with no injection reagents. Phenol and 2,4-dichlorophenol (2,4-DCP), and kaolin and a natural sandy loam soil were selected as model organics and soils, respectively. The results showed that non-uniform electrokinetics can accelerate the desorption and movement of phenol and 2,4-DCP in unsaturated soils. Electromigration and electroosmotic flow were the main driving forces, and their role in the mobilization of phenol and 2,4-DCP varied with soil pH. The movement of 2,4-DCP in the sandy loam towards the anode (about 1.0 cmd(-1)V(-1)) was 1.0-1.5 cmd(-1)V(-1) slower than that in the kaolin soil, but about 0.5 cmd(-1)V(-1) greater than that of phenol in the sandy loam. When the sandy loam was adjusted to pH 9.3, the movement of phenol and 2,4-DCP towards the anode was about twice and five times faster than that at pH 7.7, respectively. The results also demonstrated that the movement of phenol and 2,4-DCP in soils can be easily controlled by regulating the operational mode of electric field. It is believed that non-uniform electrokinetics has the potential for practical application to in situ remediation of organics-contaminated sites.

Potassium Sodium Niobate-Based Lead-Free Piezoelectric Multilayer Ceramics Co-Fired with Nickel Electrodes

PubMed Central

Kawada, Shinichiro; Hayashi, Hiroyuki; Ishii, Hideki; Kimura, Masahiko; Ando, Akira; Omiya, Suetake; Kubodera, Noriyuki

2015-01-01

Although lead-free piezoelectric ceramics have been extensively studied, many problems must still be overcome before they are suitable for practical use. One of the main problems is fabricating a multilayer structure, and one solution attracting growing interest is the use of lead-free multilayer piezoelectric ceramics. The paper reviews work that has been done by the authors on lead-free alkali niobate-based multilayer piezoelectric ceramics co-fired with nickel inner electrodes. Nickel inner electrodes have many advantages, such as high electromigration resistance, high interfacial strength with ceramics, and greater cost effectiveness than silver palladium inner electrodes. However, widely used lead zirconate titanate-based ceramics cannot be co-fired with nickel inner electrodes, and silver palladium inner electrodes are usually used for lead zirconate titanate-based piezoelectric ceramics. A possible alternative is lead-free ceramics co-fired with nickel inner electrodes. We have thus been developing lead-free alkali niobate-based multilayer ceramics co-fired with nickel inner electrodes. The normalized electric-field-induced thickness strain (Smax/Emax) of a representative alkali niobate-based multilayer ceramic structure with nickel inner electrodes was 360 pm/V, where Smax denotes the maximum strain and Emax denotes the maximum electric field. This value is about half that for the lead zirconate titanate-based ceramics that are widely used. However, a comparable value can be obtained by stacking more ceramic layers with smaller thicknesses. In the paper, the compositional design and process used to co-fire lead-free ceramics with nickel inner electrodes are introduced, and their piezoelectric properties and reliabilities are shown. Recent advances are introduced, and future development is discussed. PMID:28793646

Mathematical modeling based evaluation and simulation of boron removal in bioelectrochemical systems.

PubMed

Ping, Qingyun; Abu-Reesh, Ibrahim M; He, Zhen

2016-11-01

Boron removal is an arising issue in desalination plants due to boron's toxicity. As an emerging treatment concept, bioelectrochemical systems (BES) can achieve potentially cost-effective boron removal by taking advantage of cathodic-produced alkali. Prior studies have demonstrated successful removal of boron in microbial desalination cells (MDCs) and microbial fuel cells (MFCs), both of which are representative BES. Herein, mathematical models were developed to further evaluate boron removal by different BES and understand the key operating factors. The models delivered very good prediction of the boron concentration in the MDC integrated with Donnan Dialysis (DD) system with the lowest relative root-mean-square error (RMSE) of 0.00%; the predication of the MFC performance generated the highest RMSE of 18.55%. The model results of salt concentration, solution pH, and current generation were well fitted with experimental data for RMSE values mostly below 10%. The long term simulation of the MDC-DD system suggests that the accumulation of salt in the catholyte/stripping solution could have a positive impact on the removal of boron due to osmosis-driven convection. The current generation in the MDC may have little influence on the boron removal, while in the MFC the current-driven electromigration can contribute up to 40% of boron removal. Osmosis-induced convection transport of boron could be the major driving force for boron removal to a low level <2mgL(-1). The ratio between the anolyte and the catholyte flow rates should be kept >22.2 in order to avoid boron accumulation in the anolyte effluent. Copyright © 2016 Elsevier B.V. All rights reserved.

Probabilistic immortality of Cu damascene interconnects

NASA Astrophysics Data System (ADS)

Hau-Riege, Stefan P.

2002-02-01

We have studied electromigration short-line effects in Cu damascene interconnects through experiments on lines of various lengths L, stressed at a variety of current densities j, and embedded in different dielectric materials. We observed two modes of resistance evolution: Either the resistance of the lines remains constant for the duration of the test, so that the lines are considered immortal, or the lines fail due to abrupt open-circuit failure. The resistance was not observed to gradually increase and then saturate, as commonly observed in Al-based interconnects, because the barrier is too thin and resistive to serve as a redundant current path should voiding occur. The critical stress for void nucleation was found to be smaller than 41 MPa, since voiding occurred even under the mildest test conditions of j=2 MA/cm2 and L=10.5 μm at 300 °C. A small fraction of short Cu lines failed even at low current densities, which deems necessary a concept of probabilistic immortality rather than deterministic immortality. Experiments and modeling suggest that the probability of immortality is described by (jL2/B), where B is the effective elastic modulus of the metallization scheme. By contrast, the immortality of Al-based interconnects with shunt layers is described by (jL) if no voids nucleate, and (jL/B) if voids do nucleate. Even though the phenomenology of short-line effects differs for Al- and Cu-based interconnects, the immortality of interconnects of either materials system can be explained by the phenomena of nucleation barriers for void formation and void-growth saturation. The differences are due solely to the absence of a shunt layer and the low critical stress for void nucleation in the case of Cu.

Frequency-dependent failure mechanisms of nanocrystalline gold interconnect lines under general alternating current

NASA Astrophysics Data System (ADS)

Luo, X. M.; Zhang, B.; Zhang, G. P.

2014-09-01

Thermal fatigue failure of metallization interconnect lines subjected to alternating currents (AC) is becoming a severe threat to the long-term reliability of micro/nanodevices with increasing electrical current density/power. Here, thermal fatigue failure behaviors and damage mechanisms of nanocrystalline Au interconnect lines on the silicon glass substrate have been investigated by applying general alternating currents (the pure alternating current coupled with a direct current (DC) component) with different frequencies ranging from 0.05 Hz to 5 kHz. We observed both thermal fatigue damages caused by Joule heating-induced cyclic strain/stress and electromigration (EM) damages caused by the DC component. Besides, the damage formation showed a strong electrically-thermally-mechanically coupled effect and frequency dependence. At lower frequencies, thermal fatigue damages were dominant and the main damage forms were grain coarsening with grain boundary (GB) cracking/voiding and grain thinning. At higher frequencies, EM damages took over and the main damage forms were GB cracking/voiding of smaller grains and hillocks. Furthermore, the healing effect of the reversing current was considered to elucidate damage mechanisms of the nanocrystalline Au lines generated by the general AC. Lastly, a modified model was proposed to predict the lifetime of the nanocrystalline metal interconnect lines, i.e., that was a competing drift velocity-based approach based on the threshold time required for reverse diffusion/healing to occur.

A new model for the spectral induced polarization signature of bacterial growth in porous media

NASA Astrophysics Data System (ADS)

Revil, A.; Atekwana, E.; Zhang, C.; Jardani, A.; Smith, S.

2012-09-01

The complex conductivity of porous materials and colloidal suspensions comprises two components: an in-phase conductivity associated with electromigration of the charge carriers and a quadrature conductivity associated with the reversible storage of the charges at some polarization length scales. We developed a quantitative model to investigate the frequency domain induced polarization response of suspensions of bacteria and bacteria growth in porous media. Induced polarization of bacteria (α polarization) is related to the properties of the electrical double layer of the bacteria. Surface conductivity and α polarization are due to the Stern layer of counterions occurring in a brush of polymers coating the surface of the bacteria. These phenomena can be related to their cation exchange capacity. The mobility of the counterions in this Stern layer is found to be very small (4.7 × 10-10 m2 s-1 V-1 at 25°C). This implies a very low relaxation frequency for the αpolarization of the bacteria cells (typically around 0.1-5 Hz), in agreement with experimental observations. This new model can be coupled to reactive transport modeling codes in which the evolution of bacterial populations are usually described by Monod kinetics. We show that the growth rate and endogenous decay coefficients of bacteria in a porous sand can be inferred nonintrusively from time-lapse frequency domain induced polarization data.

Product assurance technology for procuring reliable, radiation-hard, custom LSI/VLSI electronics

NASA Technical Reports Server (NTRS)

Buehler, M. G.; Allen, R. A.; Blaes, B. R.; Hicks, K. A.; Jennings, G. A.; Lin, Y.-S.; Pina, C. A.; Sayah, H. R.; Zamani, N.

1989-01-01

Advanced measurement methods using microelectronic test chips are described. These chips are intended to be used in acquiring the data needed to qualify Application Specific Integrated Circuits (ASIC's) for space use. Efforts were focused on developing the technology for obtaining custom IC's from CMOS/bulk silicon foundries. A series of test chips were developed: a parametric test strip, a fault chip, a set of reliability chips, and the CRRES (Combined Release and Radiation Effects Satellite) chip, a test circuit for monitoring space radiation effects. The technical accomplishments of the effort include: (1) development of a fault chip that contains a set of test structures used to evaluate the density of various process-induced defects; (2) development of new test structures and testing techniques for measuring gate-oxide capacitance, gate-overlap capacitance, and propagation delay; (3) development of a set of reliability chips that are used to evaluate failure mechanisms in CMOS/bulk: interconnect and contact electromigration and time-dependent dielectric breakdown; (4) development of MOSFET parameter extraction procedures for evaluating subthreshold characteristics; (5) evaluation of test chips and test strips on the second CRRES wafer run; (6) two dedicated fabrication runs for the CRRES chip flight parts; and (7) publication of two papers: one on the split-cross bridge resistor and another on asymmetrical SRAM (static random access memory) cells for single-event upset analysis.

The electrodeposition of multilayers on a polymeric substrate in Flexible Organic Light Emitting Diode (OLED)

NASA Astrophysics Data System (ADS)

Guedes, Andre F. S.; Guedes, Vilmar P.; Tartari, Simone; Cunha, Idaulo Jose

2016-09-01

The development of Organic Light Emitting Diode (OLED), using an optically transparent substrate material and organic semiconductor materials, has been widely utilized by the electronic industry when producing new technological products. The OLED are the base Poly(3,4-ethylenedioxythiophene), PEDOT, Poly(p-phenylenevinylene), PPV, and Polyaniline, PANI, were deposited in Indium Tin Oxide, ITO, and characterized by UV-Visible Spectroscopy (UV-Vis), Optical Parameters (OP) and Scanning Electron Microscopy (SEM). In addition, the thin film obtained by the deposition of PANI, prepared in perchloric acid solution, was identified through PANI-X1. The result obtained by UV-Vis has demonstrated that the PET/ITO/PEDOT/PPV/PANI-X1/Al layer does not have displacement of absorption for wavelengths greaters after spin-coating and electrodeposition. Thus, the spectral irradiance of the OLED informed the irradiance of 100 W/m2, and this result, compared with the standard Light Emitting Diode (LED), has indicated that the OLED has higher irradiance. After 1200 hours of electrical OLED tests, the appearance of nanoparticles visible for images by SEM, to the migration process of organic semiconductor materials, was present, then. Still, similar to the phenomenon of electromigration observed in connections and interconnections of microelectronic devices, the results have revealed a new mechanism of migration, which raises the passage of electric current in OLED.

Transport of water and ions in partially water-saturated porous media. Part 1. Constitutive equations

NASA Astrophysics Data System (ADS)

Revil, A.

2017-05-01

I developed a model of cross-coupled flow in partially saturated porous media based on electrokinetic coupling including the effect of ion filtration (normal and reverse osmosis) and the multi-component nature of the pore water (wetting) phase. The model also handles diffusion and membrane polarization but is valid only for saturations above the irreducible water saturation. I start with the local Nernst-Planck and Stokes equations and I use a volume-averaging procedure to obtain the generalized Ohm, Fick, and Darcy equations with cross-coupling terms at the scale of a representative elementary volume of the porous rock. These coupling terms obey Onsager's reciprocity, which is a required condition, at the macroscale, to keep the total dissipation function of the system positive. Rather than writing the electrokinetic terms in terms of zeta potential (the double layer electrical potential on the slipping plane located in the pore water), I developed the model in terms of an effective charge density dragged by the flow of the pore water. This effective charge density is found to be strongly controlled by the permeability and the water saturation. I also developed an electrical conductivity equation including the effect of saturation on both bulk and surface conductivities, the surface conductivity being associated with electromigration in the electrical diffuse layer coating the grains. This surface conductivity depends on the CEC of the porous material.

A Single-Level Tunnel Model to Account for Electrical Transport through Single Molecule- and Self-Assembled Monolayer-based Junctions

PubMed Central

Garrigues, Alvar R.; Yuan, Li; Wang, Lejia; Mucciolo, Eduardo R.; Thompon, Damien; del Barco, Enrique; Nijhuis, Christian A.

2016-01-01

We present a theoretical analysis aimed at understanding electrical conduction in molecular tunnel junctions. We focus on discussing the validity of coherent versus incoherent theoretical formulations for single-level tunneling to explain experimental results obtained under a wide range of experimental conditions, including measurements in individual molecules connecting the leads of electromigrated single-electron transistors and junctions of self-assembled monolayers (SAM) of molecules sandwiched between two macroscopic contacts. We show that the restriction of transport through a single level in solid state junctions (no solvent) makes coherent and incoherent tunneling formalisms indistinguishable when only one level participates in transport. Similar to Marcus relaxation processes in wet electrochemistry, the thermal broadening of the Fermi distribution describing the electronic occupation energies in the electrodes accounts for the exponential dependence of the tunneling current on temperature. We demonstrate that a single-level tunnel model satisfactorily explains experimental results obtained in three different molecular junctions (both single-molecule and SAM-based) formed by ferrocene-based molecules. Among other things, we use the model to map the electrostatic potential profile in EGaIn-based SAM junctions in which the ferrocene unit is placed at different positions within the molecule, and we find that electrical screening gives rise to a strongly non-linear profile across the junction. PMID:27216489

Reliability Improvement By Adopting Ti-barrier Metal For Porous Low-k ILD Structure

NASA Astrophysics Data System (ADS)

Sakata, A.; Yamashita, S.; Omoto, S.; Hatano, M.; Wada, J.; Higashi, K.; Yamaguchi, H.; Yosho, T.; Imamizu, K.; Yamada, M.; Hasunuma, M.; Takahashi, S.; Yamada, A.; Hasegawa, T.; Motoyama, K.; Tagami, M.; Kitano, T.; Kaneko, H.

2007-10-01

Titanium (Ti) has been proposed as an excellent barrier metal (BM) material for ULSI's Cu metallization from the stand point of two characteristics. One is the oxidation property, especially for the porous low-k ILD materials for 45 nm node device; the other is the interface behavior of Ti with Cu. Both stress induced voiding (SIV) suppression and one order longer electromigration (EM) lifetime were obtained by the adoption of Ti-BM instead of the conventional Tantalum (Ta)-BM. SIV failure is accelerated in porous low-k ILD by the following steps; 1) BM oxidation by the absorbed moisture in porous low-k ILD, 2) Adhesion degradation caused by the BM oxidation results in micro delamination of Cu film (void nucleation), 3) Void growth induced by the stress gradient in the Cu interconnect. It has been considered that the small volume change of Ti oxidation and the existence of metallic Ti-O solid-solution phase would be the reason for control of moisture penetration from the low-k ILD materials. In addition, Ti/Cu intermetallic reaction and the segregation of Ti atoms at Cu grain boundaries suppress Cu migration at BM/Cu interface and Cu grain boundaries, respectively. This is supported by higher EM activation energy of Cu line with Ti-BM than that with Ta-BM. These phenomena contribute to higher interconnect reliability.

Al-Si-Cu/TiN multilayer interconnection and Al-Ge reflow sputtering technologies for quarter-micron devices

NASA Astrophysics Data System (ADS)

Kikkawa, Takamaro; Kikuta, Kuniko

1993-05-01

Issues of interconnection technologies for quarter-micron devices are the reliability of metal lines with quarter-micron feature sizes and the formation of contact-hole-plugs with high aspect ratios. This paper describes a TiN/Al-Si-Cu/TiN/Al-Si-Cu/TiN/Ti multilayer conductor structure as a quarter-micron interconnection technology and aluminum-germanium (Al-Ge) reflow sputtering as a contact-hole filling technology. The TiN/Al-Si-Cu/TiN/Al-Si-Cu/TiN/Ti multilayer conductor structure could suppress stress-induced voiding and improve the electromigration mean-time to failure. These improvements are attributed to the fact that the grain boundaries for the Al-Si-Cu film and the interfaces between the Al-Si-Cu and the TiN films are strengthened by the rigid intermetallic compound, TiAl3. The Al-Ge alloy reflow sputtering is a candidate for contact- and via-hole filling technologies in terms of reducing fabrication costs. The Al-Ge reflow sputtering achieved low temperature contact hole filling at 300 degree(s)C. Contact holes with a diameter of 0.25 micrometers and aspect ratio of 4 could be filled. This is attributed to the low eutectic temperature for Al-Ge (424 degree(s)C) and the effect of thin polysilicon underlayer on the enhancement of Al-Ge reflow.

Mapping Ionic Currents and Reactivity on the Nanoscale: Electrochemical Strain Microscopy

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

Kalinin, S.V.

2010-10-19

Solid-state electrochemical processes in oxides underpin a broad spectrum of energy and information storage devices, ranging from Li-ion and Li-air batteries, to solid oxide fuel cells (SOFC) to electroresistive and memristive systems. These functionalities are controlled by the bias-driven diffusive and electromigration transport of mobile ionic species, as well as intricate a set of electrochemical and defect-controlled reactions at interfaces and in bulk. Despite the wealth of device-level and atomistic studies, little is known on the mesoscopic mechanisms of ion diffusion and electronic transport on the level of grain clusters, individual grains, and extended defects. The development of the capabilitymore » for probing ion transport on the nanometer scale is a key to deciphering complex interplay between structure, functionality, and performance in these systems. Here we introduce Electrochemical Strain Microscopy, a scanning probe microscopy technique based on strong strain-bias coupling in the systems in which local ion concentrations are changed by electrical fields. The imaging capability, as well as time- and voltage spectroscopies analogous to traditional current based electrochemical characterization methods are developed. The reversible intercalation of Li and mapping electrochemical activity in LiCoO2 is demonstrated, illustrating higher Li diffusivity at non-basal planes and grain boundaries. In Si-anode device structure, the direct mapping of Li diffusion at extended defects and evolution of Li-activity with charge state is explored. The electrical field-dependence of Li mobility is studied to determine the critical bias required for the onset of electrochemical transformation, allowing reaction and diffusion processes in the battery system to be separated at each location. Finally, the applicability of ESM for probing oxygen vacancy diffusion and oxygen reduction/evolution reactions is illustrated, and the high resolution ESM maps are correlated with aberration corrected scanning transmission electron microscopy imaging. The future potential for deciphering mechanisms of electrochemical transformations on an atomically-defined single-defect level is discussed.« less

Electrokinetically Emplaced Amendments for Enhanced Bioremediation of Chlorinated Solvents in Clay: a Pilot Field Test

NASA Astrophysics Data System (ADS)

O'Carroll, D. M.; Inglis, A.; Head, N.; Chowdhury, A. I.; Garcia, A. N.; Reynolds, D. A.; Hogberg, D.; Edwards, E.; Lomheim, L.; Austrins, L. M.; Hayman, J.; Auger, M.; Sidebottom, A.; Eimers, J.; Gerhard, J.

2017-12-01

Bioremediation is an increasingly popular treatment technology for contaminated sites due to the proven success of biostimulation and bioaugmentation. However, bioremediation, along with other in-situ remediation technologies, faces limitations due to challenges with amendment delivery in low permeability media. Studies have suggested that electrokinetics (EK) can enhance the delivery of amendments in low permeability soils, such as clay. A pilot field trial was conducted to evaluate the potential for electrokinetics to support anaerobic dechlorination in clay by improving the transport of lactate and microorganisms. The study was performed on a former chlorinated solvent production facility in Ontario, Canada. Five transect cells were set up within the contaminated clay test area. Different amendments were injected in three of these cells to test various remediation strategies under the influence of EK. The other two cells were used as controls, one with EK applied and the other with no EK. This study focuses on the cell that applied electrokinetics for lactate emplacement followed by bioremediation (EK-Bio). This cell had an initial single injection of KB-1 bioaugmentation culture (SiREM, Canada) followed by injection of sodium lactate as a biostimulant while direct current was applied for 45 days between two electrodes 3 m apart. EK can enhance lactate migration by electromigration, while microorganisms have the potential to be influenced by electroosmosis of the bulk fluid or by electrophoresis of the charged bacteria themselves. All monitoring well locations in the EK-Bio cell exhibited evidence of successful lactate delivery corresponding to an increase in dissolved organic carbon. Reduction in chlorinated volatile organic compound (cVOC) concentrations, in particular 1,2-dichloroethane (1,2-DCA), were evident in monitoring locations coinciding with significant lactate breakthrough. Further investigation into the influence of EK-Bio on the abundance and distribution of microbial communities is being explored using soil and groundwater samples collected throughout the duration of the field trial. This study provides original insights into the application of electrokinetically-enhanced bioremediation as a treatment strategy for contaminated, low permeability porous media.

The role of bone marrow evaluation in the staging of patients with otherwise localized, low-risk neuroblastoma.

PubMed

Russell, Heidi V; Golding, Laurie A; Suell, Mary Nell; Nuchtern, Jed G; Strother, Douglas R

2005-12-01

Bone marrow aspirations and biopsies are standard staging procedures for neuroblastoma because the tumor frequently metastasizes to the bone marrow. The presence of bone marrow metastases indicates stage 4 or 4S neuroblastoma by International Neuroblastoma Staging System (INSS) criteria; these stages are also associated with other metastatic sites of disease. We questioned whether bone marrow studies changed the staging or treatment of children with localized, completely resected tumors if there was no other evidence of metastatic spread. If stage of disease rarely changed with bone marrow results, it might be possible to avoid this procedure in a subset of patients with neuroblastoma. The staging studies of patients with INSS stage 1 (n = 29), 4 (n = 60), and 4S (n = 13) neuroblastoma from two institutions were reviewed. There were no patients upstaged from stage 1 to 4 or 4S by bone marrow metastases alone. Fifty-nine of 60 stage 4 patients had other sites of metastases on imaging studies, the remaining patient had an unresectable primary tumor and marrow disease. All subjects with stage 4S disease had liver metastases. Bone marrow studies did not contribute data that changed the stage of patients who had surgically resectable tumors and no evidence of metastatic spread on imaging studies. When present, metastatic spread to the marrow was associated with advanced local tumors or other sites of metastatic disease. Given the relatively small size of our study population, further studies are warranted that investigate the utility of bone marrow studies for patients who otherwise have INSS stage 1 neuroblastoma. 2005 Wiley-Liss, Inc.

Does cemented or cementless single-stage exchange arthroplasty of chronic periprosthetic hip infections provide similar infection rates to a two-stage? A systematic review.

PubMed

George, D A; Logoluso, N; Castellini, G; Gianola, S; Scarponi, S; Haddad, F S; Drago, L; Romano, C L

2016-10-10

The best surgical modality for treating chronic periprosthetic hip infections remains controversial, with a lack of randomised controlled studies. The aim of this systematic review is to compare the infection recurrence rate after a single-stage versus a two-stage exchange arthroplasty, and the rate of cemented versus cementless single-stage exchange arthroplasty for chronic periprosthetic hip infections. We searched for eligible studies published up to December 2015. Full text or abstract in English were reviewed. We included studies reporting the infection recurrence rate as the outcome of interest following single- or two-stage exchange arthroplasty, or both, with a minimum follow-up of 12 months. Two reviewers independently abstracted data and appraised quality assessment. After study selection, 90 observational studies were included. The majority of studies were focused on a two-stage hip exchange arthroplasty (65 %), 18 % on a single-stage exchange, and only a 17 % were comparative studies. There was no statistically significant difference between a single-stage versus a two-stage exchange in terms of recurrence of infection in controlled studies (pooled odds ratio of 1.37 [95 % CI = 0.68-2.74, I 2  = 45.5 %]). Similarly, the recurrence infection rate in cementless versus cemented single-stage hip exchanges failed to demonstrate a significant difference, due to the substantial heterogeneity among the studies. Despite the methodological limitations and the heterogeneity between single cohorts studies, if we considered only the available controlled studies no superiority was demonstrated between a single- and two-stage exchange at a minimum of 12 months follow-up. The overalapping of confidence intervals related to single-stage cementless and cemented hip exchanges, showed no superiority of either technique.

The trace analysis of microorganisms in real samples by combination of a filtration microcartridge and capillary isoelectric focusing.

PubMed

Horká, Marie; Horký, Jaroslav; Kubesová, Anna; Zapletalová, Eva; Slais, Karel

2011-07-01

Trace analysis of microorganisms in real biological samples needs very sensitive methods for their detection. Most procedures for detecting and quantifying pathogens require a sample preparation step including concentrating microorganisms from large sample volumes with high and reproducible efficiency. Electromigration techniques have great potential to include the preconcentration, separation, and detection of whole cells and therefore they can rapidly indicate the presence of pathogens. The preconcentration and separation of microorganisms from real suspensions utilising a combination of filtration and capillary isoelectric focusing was developed and the possibility for its application to real samples was verified. For our experiments, spores of Monilinia species and of Penicillium expansum were selected as model bioparticles, as they cause major losses in agrosystems. The isoelectric points of the spores of M. laxa, M. fructigena, M. fruticola, and P. expansum were determined and the method was verified using real samples taken directly from infected apples. The coupling of a filtration cartridge with a separation capillary can improve the detection limit of isoelectric focusing with UV detection by at least 4 orders of magnitude. Spores of M. fructigena and of M. laxa in numbers of hundreds of particles per milliliter were detected on a visually noninfected apple surface which was cross-contaminated during handling and storage. The efficiency of preconcentration and a preliminary identification was verified by the phenotyping technique after cultivation of the spores sampled from the apple surface.

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.

Mechanisms of mineral membrane fouling growth modulated by pulsed modes of current during electrodialysis: evidences of water splitting implications in the appearance of the amorphous phases of magnesium hydroxide and calcium carbonate.

PubMed

Cifuentes-Araya, Nicolás; Astudillo-Castro, Carolina; Bazinet, Laurent

2014-07-15

Experiments revealed the fouling nature evolutions along different electrodialysis (ED) trials, and how it disappears when current pulsation acts repetitively on the interfaces of ion-exchange membranes (IEMs). Fouling was totally controlled on the diluate side of cation-exchange membrane (CEM) by the repetitive pulsation frequency of the higher on-duty ratios applied. They created steady water splitting proton-barriers that neutralized OH(-) leakage through the membrane, decreasing the interfacial pH, and fouling of the concentrate side. The anion-exchange membrane (AEM) on the diluate side was similarly protected, but it was fouled once water splitting OH(-) generation became either intense enough or excessively weak. Interestingly, amorphous magnesium hydroxide (AMH) stemmed on the CEM-diluate side from brucite under intense water splitting OH(-) generation, and/or strong OH(-) leakage electromigration through the membrane. Water dissociation and overlimiting current regimes triggered drastic water molecule removal from crystal lattices through an accelerated cascade water splitting reaction. Also, amorphous calcium carbonate (ACC) appeared on CEM under intense water splitting reaction, and disappeared once intense OH(-) leakage was allowed by the water splitting proton-barrier dissipation. Our findings have implications for membrane fouling control, as well as for the understanding of the growth behavior of CaCO3 and Mg(OH)2 species on electromembrane interfaces. Copyright © 2014 Elsevier Inc. All rights reserved.

Electromigration of Mn, Fe, Cu and Zn with citric acid in contaminated clay.

PubMed

Pazos, M; Gouveia, S; Sanroman, M A; Cameselle, C

2008-07-01

Metal reactivity, speciation and solubility have an important influence in its transportation through a porous matrix by electrokinetics and, therefore, they dramatically affect the removal efficiency. This work deals with the effect of solubility and transport competition among several metals (Mn, Fe, Cu and Zn) during their transport through polluted clay. The unenhancement electrokinetic treatment results in a limited removal of the tested metals because they were retained into the kaolinite sample by the penetration of the alkaline front. Metals showed a removal degree in accordance with the solubility of the corresponding hydroxide and its formation pH. In 7 days of treatment, the removal results were: 75.6% of Mn; 68.5% of Zn, 40.6% of Cu and 14.8% of Fe. In order to avoid the negative effects of the basic front generated at the cathode, two different techniques were proposed and tested: the addition of citric acid as complexing agent to the polluted kaolinite sample and the use of citric acid to control de pH on the cathode chamber. Both techniques are based on the capability of citric acid to act as a complexing and neutralizing agent. Almost complete removal of Mn, Cu and Zn was achieved when citric acid was used (as neutralizing or complexing agent). But Fe only reached 33% of removal because it formed a negatively charged complex with citrate that retarded its transportation to the cathode.

Insulation Resistance Degradation in Ni-BaTiO3 Multilayer Ceramic Capacitors

NASA Technical Reports Server (NTRS)

Liu, Donhang (David)

2015-01-01

Insulation resistance (IR) degradation in Ni-BaTiO3 multilayer ceramic capacitors has been characterized by the measurement of both time to failure and direct-current (DC) leakage current as a function of stress time under highly accelerated life test conditions. The measured leakage current-time dependence data fit well to an exponential form, and a characteristic growth time ?SD can be determined. A greater value of tau(sub SD) represents a slower IR degradation process. Oxygen vacancy migration and localization at the grain boundary region results in the reduction of the Schottky barrier height and has been found to be the main reason for IR degradation in Ni-BaTiO3 capacitors. The reduction of barrier height as a function of time follows an exponential relation of phi (??)=phi (0)e(exp -2?t), where the degradation rate constant ??=??o??(????/????) is inversely proportional to the mean time to failure (MTTF) and can be determined using an Arrhenius plot. For oxygen vacancy electromigration, a lower barrier height phi(0) will favor a slow IR degradation process, but a lower phi(0) will also promote electronic carrier conduction across the barrier and decrease the insulation resistance. As a result, a moderate barrier height phi(0) (and therefore a moderate IR value) with a longer MTTF (smaller degradation rate constant ??) will result in a minimized IR degradation process and the most improved reliability in Ni-BaTiO3 multilayer ceramic capacitors.

Ligand-enhanced electrokinetic remediation of metal-contaminated marine sediments with high acid buffering capacity.

PubMed

Masi, Matteo; Iannelli, Renato; Losito, Gabriella

2016-06-01

The suitability of electrokinetic remediation for removing heavy metals from dredged marine sediments with high acid buffering capacity was investigated. Laboratory-scale electrokinetic remediation experiments were carried out by applying two different voltage gradients to the sediment (0.5 and 0.8 V/cm) while circulating water or two different chelating agents at the electrode compartments. Tap water, 0.1 M citric acid and 0.1 M ethylenediaminetetraacetic acid (EDTA) solutions were used respectively. The investigated metals were Zn, Pb, V, Ni and Cu. In the unenhanced experiment, the acid front could not propagate due to the high acid buffering capacity of the sediments; the production of OH(-) ions at the cathode resulted in a high-pH environment causing the precipitation of CaCO3 and metal hydroxides. The use of citric acid prevented the formation of precipitates, but solubilisation and mobilisation of metal species were not sufficiently achieved. Metal removal was relevant when EDTA was used as the conditioning agent, and the electric potential was raised up to 0.8 V/cm. EDTA led to the formation of negatively charged complexes with metals which migrated towards the anode compartment by electromigration. This result shows that metal removal from sediments with high acid buffering capacity may be achieved by enhancing the electrokinetic process by EDTA addition when the acidification of the medium is not economically and/or environmentally sustainable.

Detection and Separation of Inorganic Cations in Natural, Potable, and Wastewater Samples Using Capillary Zone Electrophoresis with Indirect UV Detection

PubMed Central

Varden, Lara; Bou-Abdallah, Fadi

2017-01-01

Capillary zone electrophoresis (CZE) is a sensitive and rapid technique for determining traces of inorganic cations in water samples. CZE with indirect UV-diode array detection (CZE-DAD) was utilized to identify several inorganic cations in natural, potable, and wastewater samples. A pH 4.35 background electrolyte system was employed and consisted of 15 mM imidazole, 8 mM malonic acid, 2 mM 18-crown-6 ether as complexing agents, 10% v/v methanol as an organic modifier with indirect absorbance reference at 214 nm. The CZE method involved electromigration injection at 5 kV for 5 s, a separation voltage of 20 kV at 25°C, and a detection wavelength of 280 nm. Six main cations (ammonium NH4+, potassium K+, calcium Ca2+, sodium Na+, magnesium Mg2+, and lead Pb2+) were tested, and all but lead, were detected in the water samples at concentrations between 0.03 and 755 ppm with a detection limit ranging between 0.023 and 0.084 ppm. The successful evaluation of the proposed methodology allowed us to reliably detect and separate six metal ions in different water samples without any pretreatment. All water samples were collected from Northern New York towns and the Raquette River water system, the third longest river in New York State and the largest watershed of the central and western Adirondacks. PMID:29057144

Insulation Resistance Degradation in Ni-BaTiO3 Multilayer Ceramic Capacitors

NASA Technical Reports Server (NTRS)

Liu, Donhang David

2015-01-01

Insulation resistance (IR) degradation in NiBaTiO3 multilayer ceramic capacitors has been characterized by the measurement of both time to failure (TTF) and direct current leakage current as a function of stress time under highly accelerated life test conditions. The measured leakage current time dependence data fit well to an exponential form, and a characteristic growth time tau (sub SD) can be determined. A greater value of tau (sub SD) represents a slower IR degradation process. Oxygen vacancy migration and localization at the grain boundary region results in the reduction of the Schottky barrier height and has been found to be the main reason for IR degradation in NiBaTiO3 capacitors. The reduction of barrier height as a function oftime follows an exponential relation of phi (t ) = phi (0) e (exp -2Kt), where 13 the degradation rate constant K Koe (Ek/kT) is inversely proportional to the mean TTF (MTTF) and can be determined using an Arrhenius plot. For oxygen vacancy electromigration, a lower barrier height phi (0) will favor a slow IR degradation process, but a lower phi (0) will also promote electronic carrier conduction across the barrier and decrease the IR. As a result, a moderate barrier height phi (0) (and therefore a moderate IR value) with a longer MTTF (smaller degradation rate constant K) will result in a minimized IR degradation process and the most improved reliability in NiBaTiO3 multilayer ceramic capacitors.

Physicochemical effects on uncontaminated kaolinite due to electrokinetic treatment using inert electrodes.

PubMed

Liaki, Christina; Rogers, Christopher D F; Boardman, David I

2008-07-01

To determine the consequences of applying electrokinetics to clay soils, in terms of mechanisms acting and resulting effects on the clay, tests were conducted in which an electrical gradient was applied across controlled specimens of English China Clay (ECC) using 'inert' electrodes and a 'Reverse Osmosis' water feed to the electrodes (i.e., to mimic electrokinetic stabilisation without the stabiliser added or electrokinetic remediation without the contaminant being present). The specimens in which electromigration was induced over time periods of 3, 7, 14 and 28 days were subsequently tested for Atterberg Limits, undrained shear strength using a hand shear vane, water content, pH, conductivity and zeta potential. Water flowed through the system from anode to cathode and directly affected the undrained shear strength of the clay. Acid and alkali fronts were created around the anode and cathode, respectively, causing changes in the pH, conductivity and zeta potential of the soil. Variations in zeta potential were linked to flocculation and dispersion of the soil particles, thus raising or depressing the Liquid Limit and Plastic Limit, and influencing the undrained shear strength. Initial weakening around the anode and cathode was replaced by a regain of strength at the anode once acidic conditions had been created, while highly alkaline conditions at the cathode induced a marked improvement in strength. A novel means of indicating strength improvement by chemical means, i.e., free from water content effects, is presented to assist in interpretation of the results.

Localized Pulsed Electrodeposition Process for Three-Dimensional Printing of Nanotwinned Metallic Nanostructures.

PubMed

Daryadel, Soheil; Behroozfar, Ali; Morsali, S Reza; Moreno, Salvador; Baniasadi, Mahmoud; Bykova, Julia; Bernal, Rodrigo A; Minary-Jolandan, Majid

2018-01-10

Nanotwinned-metals (nt-metals) offer superior mechanical (high ductility and strength) and electrical (low electromigration) properties compared to their nanocrystalline (nc) counterparts. These properties are advantageous in particular for applications in nanoscale devices. However, fabrication of nt-metals has been limited to films (two-dimensional) or template-based (one-dimensional) geometries, using various chemical and physical processes. In this Letter, we demonstrate the ambient environment localized pulsed electrodeposition process for direct printing of three-dimensional (3D) freestanding nanotwinned-Copper (nt-Cu) nanostructures. 3D nt-Cu structures were additively manufactured using pulsed electrodeposition at the tip of an electrolyte-containing nozzle. Focused ion beam (FIB) and transmission electron microscopy (TEM) analysis revealed that the printed metal was fully dense, and was mostly devoid of impurities and microstructural defects. FIB and TEM images also revealed nanocrystalline-nanotwinned-microstructure (nc-nt-microstructure), and confirmed the formation of coherent twin boundaries in the 3D-printed Cu. Mechanical properties of the 3D-printed nc-nt-Cu were characterized by direct printing (FIB-less) of micropillars for in situ SEM microcompression experiments. The 3D-printed nc-nt-Cu exhibited a flow stress of over 960 MPa, among the highest ever reported, which is remarkable for a 3D-printed material. The microstructure and mechanical properties of the nc-nt-Cu were compared to those of nc-Cu printed using the same process under direct current (DC) voltage.

Controllable Switching Filaments Prepared via Tunable and Well-Defined Single Truncated Conical Nanopore Structures for Fast and Scalable SiOx Memory.

PubMed

Kwon, Soonbang; Jang, Seonghoon; Choi, Jae-Wan; Choi, Sanghyeon; Jang, Sukjae; Kim, Tae-Wook; Wang, Gunuk

2017-12-13

The controllability of switching conductive filaments is one of the central issues in the development of reliable metal-oxide resistive memory because the random dynamic nature and formation of the filaments pose an obstacle to desirable switching performance. Here, we introduce a simple and novel approach to control and form a single silicon nanocrystal (Si-NC) filament for use in SiO x memory devices. The filament is formed with a confined vertical nanoscale gap by using a well-defined single vertical truncated conical nanopore (StcNP) structure. The physical dimensions of the Si-NC filaments such as number, size, and length, which have a significant influence on the switching properties, can be simply engineered by the breakdown of an Au wire through different StcNP structures. In particular, we demonstrate that the designed SiO x memory junction with a StcNP of pore depth of ∼75 nm and a bottom diameter of ∼10 nm exhibited a switching speed of up to 6 ns for both set and reset process, significantly faster than reported SiO x memory devices. The device also exhibited a high ON-OFF ratio, multistate storage ability, acceptable endurance, and retention stability. The influence of the physical dimensions of the StcNP on the switching features is discussed based on the simulated temperature profiles of the Au wire and the nanogap size generated inside the StcNP structure during electromigration.

Time-resolved mapping of water diffusion coefficients in a working soft actuator device.

PubMed

Naji, Leila; Chudek, John A; Baker, Richard T

2008-08-14

Diffusion-weighted imaging was employed to spatially map the distribution of the diffusion coefficient of water, D, in bare, water-soaked, Li(+)-exchanged, cast Nafion and in an ionic polymer-metal composite (IPMC) soft actuator element, prepared from this bare Nafion by impregnation with Pt electrodes. D was evaluated in two orthogonal directions: along one of the long dimensions of the sample (Dx) and through its thickness (Dz). D-maps of the IPMC element were obtained both in the absence of an applied potential and in situ during the application of a 3 V dc potential across the thickness of the sample. In the bare Nafion, D-maps showed uniform values of both Dx and Dz of about 6 x 10 (-10) m(2) s(-1). In the IPMC two effects were observed: (i) D at the electroded surfaces of the IPMC was higher than at the center of the sample; (ii) this difference was much greater in Dz than in Dx . Both effects were explained by the influence of the impregnated Pt electrodes on polymer structure. The D-maps in the electrochemical measurements showed high values of D (up to 8 x 10(-10) m(2) s(-1)) at the cathode and low values (from 1 x 10(-10) m(2) s(-1)) at the anode. This was explained in terms of the effect on the Nafion nanostructure of the forced electro-migration of Li(H2O)x(+) species toward the cathode.

Sample preconcentration with chemical derivatization in capillary electrophoresis. Capillary as preconcentrator, microreactor and chiral selector for high-throughput metabolite screening.

PubMed

Ptolemy, Adam S; Britz-McKibbin, Philip

2006-02-17

New strategies for integrating sample pretreatment with chemical analyses under a single format is required for rapid, sensitive and enantioselective analyses of low abundance metabolites in complex biological samples. Capillary electrophoresis (CE) offers a unique environment for controlling analyte/reagent band dispersion and electromigration properties using discontinuous electrolyte systems. Recent work in our laboratory towards developing a high-throughput CE platform for low abundance metabolites via on-line sample preconcentration with chemical derivatization (SPCD) is primarily examined in this review, as there have been surprisingly only a few strategies reported in the literature to date. In-capillary sample preconcentration serves to enhance concentration sensitivity via electrokinetic focusing of long sample injection volumes for lower detection limits, whereas chemical derivatization by zone passing is used to expand detectability and selectivity, notably for enantiomeric resolution of metabolites lacking intrinsic chromophores using nanolitre volumes of reagent. Together, on-line SPCD-CE can provide over a 100-fold improvement in concentration sensitivity, shorter total analysis times, reduced sample handling and improved reliability for a variety of amino acid and amino sugar metabolites, which is also amenable to automated high-throughput screening. This review will highlight basic method development and optimization parameters relevant to SPCD-CE, including applications to bacterial metabolite flux and biomarker analyses. Insight into the mechanism of analyte focusing and labeling by SPCD-CE is also discussed, as well as future directions for continued research.

Using transdermal iontophoresis to increase granisetron delivery across skin in vitro and in vivo: effect of experimental conditions and a comparison with other enhancement strategies.

PubMed

Cázares-Delgadillo, Jennyfer; Ganem-Rondero, Adriana; Quintanar-Guerrero, David; López-Castellano, Alicia C; Merino, Virginia; Kalia, Yogeshvar N

2010-03-18

The objectives of the study were (i) to investigate the effect of experimental parameters on the iontophoretic transport of granisetron, (ii) to identify the relative contributions of electromigration (EM) and electroosmosis (EO), (iii) to determine the feasibility of delivering therapeutic amounts of drug for the treatment of chemotherapy-induced nausea and vomiting and (iv) to test the in vitro results in a simple animal model in vivo. Preliminary in vitro studies using aqueous granisetron formulations investigating the effect of drug concentration (5, 10, 20 and 40 mM) and current density (0.1, 0.2, 0.3 mA cm(-2)) were performed using porcine ear skin. As expected, cumulative delivery in vitro at the 20 and 40 mM concentrations was significantly greater than that at 5 and 10mM, which were not statistically different (p<0.05). Increasing the applied current density from 0.1 to 0.3 mA cm(-2) resulted in a approximately 4.2-fold increase in iontophoretic flux. Furthermore, in the absence of Na(+) in the formulation, no dependence of iontophoretic flux on drug concentration was reported (at a granisetron concentration of 40 mM, the transport rate was 2.93+/-0.62 microg cm(-2)min(-1)). Co-iontophoresis of acetaminophen was used to show that EM was the predominant transport mechanism accounting for 71-86% of total granisetron delivery. In vivo studies in Wistar rats (40 mM granisetron; application of 0.3 mA cm(-2) for 5h with Ag/AgCl electrodes and salt bridges) showed an average iontophoretic input rate (k(input)) of 0.83+/-0.26 microg min(-1) and a maximum plasma concentration (C(max)) of 0.092+/-0.004 microg ml(-1). Based on these results and given the known pharmacokinetics, transdermal iontophoresis could achieve therapeutic drug levels for the management of chemotherapy-induced emesis using a reasonably sized (4-6 cm(2)) patch. Copyright 2010 Elsevier B.V. All rights reserved.

Two-stage earth-to-orbit vehicles with dual-fuel propulsion in the Orbiter

NASA Technical Reports Server (NTRS)

Martin, J. A.

1982-01-01

Earth-to-orbit vehicle studies of future replacements for the Space Shuttle are needed to guide technology development. Previous studies that have examined single-stage vehicles have shown advantages for dual-fuel propulsion. Previous two-stage system studies have assumed all-hydrogen fuel for the Orbiters. The present study examined dual-fuel Orbiters and found that the system dry mass could be reduced with this concept. The possibility of staging the booster at a staging velocity low enough to allow coast-back to the launch site is shown to be beneficial, particularly in combination with a dual-fuel Orbiter. An engine evaluation indicated the same ranking of engines as did a previous single-stage study. Propane and RP-1 fuels result in lower vehicle dry mass than methane, and staged-combustion engines are preferred over gas-generator engines. The sensitivity to the engine selection is less for two-stage systems than for single-stage systems.

SEMIPARAMETRIC ADDITIVE RISKS REGRESSION FOR TWO-STAGE DESIGN SURVIVAL STUDIES

PubMed Central

Li, Gang; Wu, Tong Tong

2011-01-01

In this article we study a semiparametric additive risks model (McKeague and Sasieni (1994)) for two-stage design survival data where accurate information is available only on second stage subjects, a subset of the first stage study. We derive two-stage estimators by combining data from both stages. Large sample inferences are developed. As a by-product, we also obtain asymptotic properties of the single stage estimators of McKeague and Sasieni (1994) when the semiparametric additive risks model is misspecified. The proposed two-stage estimators are shown to be asymptotically more efficient than the second stage estimators. They also demonstrate smaller bias and variance for finite samples. The developed methods are illustrated using small intestine cancer data from the SEER (Surveillance, Epidemiology, and End Results) Program. PMID:21931467

Combining evidence from multiple electronic health care databases: performances of one-stage and two-stage meta-analysis in matched case-control studies.

PubMed

La Gamba, Fabiola; Corrao, Giovanni; Romio, Silvana; Sturkenboom, Miriam; Trifirò, Gianluca; Schink, Tania; de Ridder, Maria

2017-10-01

Clustering of patients in databases is usually ignored in one-stage meta-analysis of multi-database studies using matched case-control data. The aim of this study was to compare bias and efficiency of such a one-stage meta-analysis with a two-stage meta-analysis. First, we compared the approaches by generating matched case-control data under 5 simulated scenarios, built by varying: (1) the exposure-outcome association; (2) its variability among databases; (3) the confounding strength of one covariate on this association; (4) its variability; and (5) the (heterogeneous) confounding strength of two covariates. Second, we made the same comparison using empirical data from the ARITMO project, a multiple database study investigating the risk of ventricular arrhythmia following the use of medications with arrhythmogenic potential. In our study, we specifically investigated the effect of current use of promethazine. Bias increased for one-stage meta-analysis with increasing (1) between-database variance of exposure effect and (2) heterogeneous confounding generated by two covariates. The efficiency of one-stage meta-analysis was slightly lower than that of two-stage meta-analysis for the majority of investigated scenarios. Based on ARITMO data, there were no evident differences between one-stage (OR = 1.50, CI = [1.08; 2.08]) and two-stage (OR = 1.55, CI = [1.12; 2.16]) approaches. When the effect of interest is heterogeneous, a one-stage meta-analysis ignoring clustering gives biased estimates. Two-stage meta-analysis generates estimates at least as accurate and precise as one-stage meta-analysis. However, in a study using small databases and rare exposures and/or outcomes, a correct one-stage meta-analysis becomes essential. Copyright © 2017 John Wiley & Sons, Ltd.

One-stage versus two-stage exchange arthroplasty for infected total knee arthroplasty: a systematic review.

PubMed

Nagra, Navraj S; Hamilton, Thomas W; Ganatra, Sameer; Murray, David W; Pandit, Hemant

2016-10-01

Infection complicating total knee arthroplasty (TKA) has serious implications. Traditionally the debate on whether one- or two-stage exchange arthroplasty is the optimum management of infected TKA has favoured two-stage procedures; however, a paradigm shift in opinion is emerging. This study aimed to establish whether current evidence supports one-stage revision for managing infected TKA based on reinfection rates and functional outcomes post-surgery. MEDLINE/PubMed and CENTRAL databases were reviewed for studies that compared one- and two-stage exchange arthroplasty TKA in more than ten patients with a minimum 2-year follow-up. From an initial sample of 796, five cohort studies with a total of 231 patients (46 single-stage/185 two-stage; median patient age 66 years, range 61-71 years) met inclusion criteria. Overall, there were no significant differences in risk of reinfection following one- or two-stage exchange arthroplasty (OR -0.06, 95 % confidence interval -0.13, 0.01). Subgroup analysis revealed that in studies published since 2000, one-stage procedures have a significantly lower reinfection rate. One study investigated functional outcomes and reported that one-stage surgery was associated with superior functional outcomes. Scarcity of data, inconsistent study designs, surgical technique and antibiotic regime disparities limit recommendations that can be made. Recent studies suggest one-stage exchange arthroplasty may provide superior outcomes, including lower reinfection rates and superior function, in select patients. Clinically, for some patients, one-stage exchange arthroplasty may represent optimum treatment; however, patient selection criteria and key components of surgical and post-operative anti-microbial management remain to be defined. III.

Relationship between the skeletal maturation of the distal attachment of the patellar tendon and physical features in preadolescent male football players.

PubMed

Nakase, Junsuke; Aiba, Tomohiro; Goshima, Kenichi; Takahashi, Ryohei; Toratani, Tatsuhiro; Kosaka, Masahiro; Ohashi, Yoshinori; Tsuchiya, Hiroyuki

2014-01-01

The aim of this study was to compare ultrasonography stages of the tibial tuberosity development and physical features. This study examined 200 knees in 100 male football players aged 10-15 years. Tibial tuberosity development on ultrasonography was divided into 3 stages: Sonolucent stage (stage S), Individual stage (stage I), and Connective stage (stage C). Age, height, quadriceps and hamstring muscle tightness, and muscle strength in knee extension and flexion were determined. These findings were compared with the respective stages of development. The tibial tuberosity was stage S in 27 knees, stage I in 69 knees, and stage C in 104 knees, with right and left sides at the same stage in 95 %. Average age and height significantly increased with advancing tibial tuberosity development. Quadriceps tightness increased with tibial tuberosity development. Hamstring tightness decreased with development. The strength of both knee extension and flexion increased with advancing development, with a greater change seen in knee extension, hamstring/quadriceps ratio: stage C, 0.74; stage A, 0.64; stage E, 0.53. Osgood-Schlatter pathogenesis reportedly involves increased quadriceps tightness with rapidly increasing femoral length during tibial tuberosity development. In this study, it was confirmed that quadriceps tightness increased, yet hamstring tightness decreased, suggesting that quadriceps tightness is not due to femoral length alone. Other factors, including muscle strength, may be involved. The study shows that thigh muscle tightness and thigh muscle performance change with the skeletal maturation of the distal attachment of the patellar tendon. These results add new information to the pathogenesis of Osgood-Schlatter disease.

Upper stage technology evaluation studies

NASA Technical Reports Server (NTRS)

1972-01-01

Studies to evaluate advanced technology relative to chemical upper stages and orbit-to-orbit stages are reported. The work described includes: development of LH2/LOX stage data, development of data to indicate stage sensitivity to engine tolerance, modified thermal routines to accommodate storable propellants, added stage geometries to computer program for monopropellant configurations, determination of the relative gain obtainable through improvement of stage mass fraction, future propulsion concepts, effect of ultrahigh chamber-pressure increases, and relative gains obtainable through improved mass fraction.

Study of Kidney Tumors in Younger Patients

ClinicalTrials.gov

2017-11-27

Clear Cell Sarcoma of the Kidney; Congenital Mesoblastic Nephroma; Diffuse Hyperplastic Perilobar Nephroblastomatosis; Rhabdoid Tumor of the Kidney; Stage I Renal Cell Cancer; Stage I Wilms Tumor; Stage II Renal Cell Cancer; Stage II Wilms Tumor; Stage III Renal Cell Cancer; Stage III Wilms Tumor; Stage IV Renal Cell Cancer; Stage IV Wilms Tumor; Stage V Wilms Tumor

Prognosis of canine patients with nasal tumors according to modified clinical stages based on computed tomography: a retrospective study.

PubMed

Kondo, Yumi; Matsunaga, Satoru; Mochizuki, Manabu; Kadosawa, Tsuyoshi; Nakagawa, Takayuki; Nishimura, Ryohei; Sasaki, Nobuo

2008-03-01

To evaluate the efficacy of clinical staging based on computed tomography (CT) imaging over the World Health Organization (WHO) staging system based on radiography for nasal tumors in dogs, a retrospective study was conducted. This study used 112 dogs that had nasal tumors; they had undergone radiography and CT and had been histologically confirmed as having nasal tumors. Among 112 dogs, 85 (75.9%) were diagnosed as adenocarcinoma. Then they were analyzed for survival time according to each staging system. More than 70% of the patients with adenocarcinoma were classified as having WHO stage III. The patients classified under WHO stage II tended to survive longer than those classified under WHO stage III. Dogs classified under WHO stage III were further grouped into CT stages III and IV, and CT stage III patients had a significantly longer survival time than CT stage IV patients. In addition, patients treated with a combination of surgery and radiation had a significantly longer survival time than the patients who did not receive any treatment in CT stage III. On the other hand, different treatment modalities did not show a significant difference in the survival time of CT stage IV dogs. The results suggest that WHO stage III dogs may have various levels of tumor progression, indicating that the CT staging system may be more accurate than the WHO staging system.

A systematic review of the evidence for single stage and two stage revision of infected knee replacement

PubMed Central

2013-01-01

Background Periprosthetic infection about the knee is a devastating complication that may affect between 1% and 5% of knee replacement. With over 79 000 knee replacements being implanted each year in the UK, periprosthetic infection (PJI) is set to become an important burden of disease and cost to the healthcare economy. One of the important controversies in treatment of PJI is whether a single stage revision operation is superior to a two-stage procedure. This study sought to systematically evaluate the published evidence to determine which technique had lowest reinfection rates. Methods A systematic review of the literature was undertaken using the MEDLINE and EMBASE databases with the aim to identify existing studies that present the outcomes of each surgical technique. Reinfection rate was the primary outcome measure. Studies of specific subsets of patients such as resistant organisms were excluded. Results 63 studies were identified that met the inclusion criteria. The majority of which (58) were reports of two-stage revision. Reinfection rated varied between 0% and 41% in two-stage studies, and 0% and 11% in single stage studies. No clinical trials were identified and the majority of studies were observational studies. Conclusions Evidence for both one-stage and two-stage revision is largely of low quality. The evidence basis for two-stage revision is significantly larger, and further work into direct comparison between the two techniques should be undertaken as a priority. PMID:23895421

Diffuse charge dynamics in ionic thermoelectrochemical systems.

PubMed

Stout, Robert F; Khair, Aditya S

2017-08-01

Thermoelectrics are increasingly being studied as promising electrical generators in the ongoing search for alternative energy sources. In particular, recent experimental work has examined thermoelectric materials containing ionic charge carriers; however, the majority of mathematical modeling has been focused on their steady-state behavior. Here, we determine the time scales over which the diffuse charge dynamics in ionic thermoelectrochemical systems occur by analyzing the simplest model thermoelectric cell: a binary electrolyte between two parallel, blocking electrodes. We consider the application of a temperature gradient across the device while the electrodes remain electrically isolated from each other. This results in a net voltage, called the thermovoltage, via the Seebeck effect. At the same time, the Soret effect results in migration of the ions toward the cold electrode. The charge dynamics are described mathematically by the Poisson-Nernst-Planck equations for dilute solutions, in which the ion flux is driven by electromigration, Brownian diffusion, and thermal diffusion under a temperature gradient. The temperature evolves according to the heat equation. This nonlinear set of equations is linearized in the (experimentally relevant) limit of a "weak" temperature gradient. From this, we show that the time scale on which the thermovoltage develops is the Debye time, 1/Dκ^{2}, where D is the Brownian diffusion coefficient of both ion species, and κ^{-1} is the Debye length. However, the concentration gradient due to the Soret effect develops on the bulk diffusion time, L^{2}/D, where L is the distance between the electrodes. For thin diffuse layers, which is the condition under which most real devices operate, the Debye time is orders of magnitude less than the diffusion time. Therefore, rather surprisingly, the majority of ion motion occurs after the steady thermovoltage has developed. Moreover, the dynamics are independent of the thermal diffusion coefficients, which simply set the magnitude of the steady-state thermovoltage.

Diffuse charge dynamics in ionic thermoelectrochemical systems

NASA Astrophysics Data System (ADS)

Stout, Robert F.; Khair, Aditya S.

2017-08-01

Thermoelectrics are increasingly being studied as promising electrical generators in the ongoing search for alternative energy sources. In particular, recent experimental work has examined thermoelectric materials containing ionic charge carriers; however, the majority of mathematical modeling has been focused on their steady-state behavior. Here, we determine the time scales over which the diffuse charge dynamics in ionic thermoelectrochemical systems occur by analyzing the simplest model thermoelectric cell: a binary electrolyte between two parallel, blocking electrodes. We consider the application of a temperature gradient across the device while the electrodes remain electrically isolated from each other. This results in a net voltage, called the thermovoltage, via the Seebeck effect. At the same time, the Soret effect results in migration of the ions toward the cold electrode. The charge dynamics are described mathematically by the Poisson-Nernst-Planck equations for dilute solutions, in which the ion flux is driven by electromigration, Brownian diffusion, and thermal diffusion under a temperature gradient. The temperature evolves according to the heat equation. This nonlinear set of equations is linearized in the (experimentally relevant) limit of a "weak" temperature gradient. From this, we show that the time scale on which the thermovoltage develops is the Debye time, 1 /D κ2 , where D is the Brownian diffusion coefficient of both ion species, and κ-1 is the Debye length. However, the concentration gradient due to the Soret effect develops on the bulk diffusion time, L2/D , where L is the distance between the electrodes. For thin diffuse layers, which is the condition under which most real devices operate, the Debye time is orders of magnitude less than the diffusion time. Therefore, rather surprisingly, the majority of ion motion occurs after the steady thermovoltage has developed. Moreover, the dynamics are independent of the thermal diffusion coefficients, which simply set the magnitude of the steady-state thermovoltage.

Immortality of Cu damascene interconnects

NASA Astrophysics Data System (ADS)

Hau-Riege, Stefan P.

2002-04-01

We have studied short-line effects in fully-integrated Cu damascene interconnects through electromigration experiments on lines of various lengths and embedded in different dielectric materials. We compare these results with results from analogous experiments on subtractively-etched Al-based interconnects. It is known that Al-based interconnects exhibit three different behaviors, depending on the magnitude of the product of current density, j, and line length, L: For small values of (jL), no void nucleation occurs, and the line is immortal. For intermediate values, voids nucleate, but the line does not fail because the current can flow through the higher-resistivity refractory-metal-based shunt layers. Here, the resistance of the line increases but eventually saturates, and the relative resistance increase is proportional to (jL/B), where B is the effective elastic modulus of the metallization system. For large values of (jL/B), voiding leads to an unacceptably high resistance increase, and the line is considered failed. By contrast, we observed only two regimes for Cu-based interconnects: Either the resistance of the line stays constant during the duration of the experiment, and the line is considered immortal, or the line fails due to an abrupt open-circuit failure. The absence of an intermediate regime in which the resistance saturates is due to the absence of a shunt layer that is able to support a large amount of current once voiding occurs. Since voids nucleate much more easily in Cu- than in Al-based interconnects, a small fraction of short Cu lines fails even at low current densities. It is therefore more appropriate to consider the probability of immortality in the case of Cu rather than assuming a sharp boundary between mortality and immortality. The probability of immortality decreases with increasing amount of material depleted from the cathode, which is proportional to (jL2/B) at steady state. By contrast, the immortality of Al-based interconnects is described by (jL) if no voids nucleate, and (jL/B) if voids nucleate.

Adaptation of Hunter Cynism Scale to Turkish: Validity and Reliability Study

ERIC Educational Resources Information Center

Kiraz, Zafer; Bakioglu, Fuad

2016-01-01

The aim of this study is to carry out the adaptation of Hunter Cynicism Scale to Turkish. For this purpose, this study consists of two stages. 311 university students participated in for the first stage and 313 university students participated in for the second stage of this study. In the first stage, translation, exploratory factor analysis,…

Ganetespib Window of Opportunity Study in Head and Neck Cancers

ClinicalTrials.gov

2016-07-22

Stage I Hypopharyngeal Squamous Cell Carcinoma; Stage I Laryngeal Squamous Cell Carcinoma; Stage I Oral Cavity Squamous Cell Carcinoma; Stage I Oropharyngeal Squamous Cell Carcinoma; Stage II Hypopharyngeal Squamous Cell Carcinoma; Stage II Laryngeal Squamous Cell Carcinoma; Stage II Oral Cavity Squamous Cell Carcinoma; Stage II Oropharyngeal Squamous Cell Carcinoma; Stage III Hypopharyngeal Squamous Cell Carcinoma; Stage III Laryngeal Squamous Cell Carcinoma; Stage III Oral Cavity Squamous Cell Carcinoma; Stage III Oropharyngeal Squamous Cell Carcinoma; Stage IVA Hypopharyngeal Squamous Cell Carcinoma; Stage IVA Laryngeal Squamous Cell Carcinoma; Stage IVA Oral Cavity Squamous Cell Carcinoma; Stage IVA Oropharyngeal Squamous Cell Carcinoma

Schoolteachers' Constructions of Desirable Educational Leadership: A Career-Stage Perspective

ERIC Educational Resources Information Center

Oplatka, Izhar; Tako, Eitan

2009-01-01

The current study aimed at exploring desirable constructions of educational leadership among Israeli schoolteachers at three different career stages, as well as tracing the origins of these constructions. Based on semi-structured interviews with 10 teachers at early-career stage, 10 at mid-career stage and 10 at late-career stage, the study first…

Phase I Study of Intravenous Triapine (IND # 68338) in Combination With Pelvic Radiation Therapy With or Without Weekly Intravenous Cisplatin Chemotherapy for Locally Advanced Cervical, Vaginal, or Pelvic Gynecologic Malignancies

ClinicalTrials.gov

2013-01-10

Recurrent Cervical Cancer; Recurrent Ovarian Epithelial Cancer; Recurrent Vaginal Cancer; Recurrent Vulvar Cancer; Stage III Vaginal Cancer; Stage IIIA Cervical Cancer; Stage IIIA Ovarian Epithelial Cancer; Stage IIIA Vulvar Cancer; Stage IIIB Cervical Cancer; Stage IIIB Ovarian Epithelial Cancer; Stage IIIB Vulvar Cancer; Stage IIIC Ovarian Epithelial Cancer; Stage IIIC Vulvar Cancer; Stage IV Ovarian Epithelial Cancer; Stage IVA Cervical Cancer; Stage IVA Vaginal Cancer; Stage IVB Cervical Cancer; Stage IVB Vaginal Cancer

Evaluation of skeletal maturity using maxillary canine, mandibular second and third molar calcification stages.

PubMed

Trakinienė, Giedrė; Smailienė, Dalia; Kučiauskienė, Ainė

2016-08-01

The objective of this study was to evaluate whether the calcification stages of maxillary canine, mandibular second molar, and mandibular third molar can be used for assessment of growth phase. The study group consisted of 274 subjects. Pre-treatment digital panoramic and lateral cephalometric radiographs of the patients were analysed. The patients' age was ranging from 7 to 19 years. Right maxillary canine, mandibular second molar and third molar were used as a sample. The teeth mineralization was assessed using modification of Gleiser and Hunt method. The skeletal maturation was assessed by the cervical vertebrae maturation (CVM) method. A significant association was found between CVM stage 2 and maxillary canine (UC) stage 4, mandibular second molar (LM2) stage 4, and mandibular third molar (LM3) stage 1. CVM stage 3 corresponded with UC stage 5, LM2 stage 5, LM3 stage 2. CVM stage 4 matched with UC stage 5, LM2 stage 6 and LM3 stage 3. The highest correlations between CVM and calcification stages were in the group of the maxillary canine (r = 0.812, P < 0.01) and mandibular second molar (r = 0.824, P < 0.01). Limitation of our study was that the study sample was not very big and the distribution value in the groups was very high, so it was impossible to check more statistical parameters. The calcification stages of UC, LM2, and LM3 as indicators of skeletal maturity could be clinically used with caution, until this method is verified with a larger sample group. © The Author 2015. Published by Oxford University Press on behalf of the European Orthodontic Society. All rights reserved. For permissions, please email: journals.permissions@oup.com.

Misstaging in nephroblastoma. Causes and consequences. A report of the Sixth Nephroblastoma Trial and Study of the International Society of Paediatric Oncology.

PubMed

de Kraker, J; Delemarre, J F; Lilien, M R; Tournade, M F

1999-06-01

In the Wilms tumour trials and studies of the International Society of Paediatric Oncology (SIOP), the postoperative treatment is based on the extension (stage) and the histological type. Incorrect staging results in under- or overtreatment. The authors studied the causes and consequences of misstaging in SIOP 6. In this study, the final stage was defined by a central panel of pathologists after review of the surgical and histopathological forms and study of representative microscopical sections. In 46 out of 509 trial patients there was a discrepancy between the final stage and the stage determined at the participating centres: 33 patients were understaged of whom 27 survived more than 5 years (18% died) and 13 patients were overstaged of whom 11 survived more than 5 years (15.3% died). All children with tumour extension into the renal pelvis and treated as stage I instead of stage II survived without evidence of disease. Therefore, it was decided to treat these children in the next study as a stage I. In 17 cases the treatment was based on the surgical stage before the pathological stage was known or the treatment was given according to the stage determined by the local pathologist without waiting for the panel review. The numbers are too small to conclude on the consequences of overtreatment on late effects. For all clinicians the main and most important conclusion of this study is: wait for the final pathology report before initiating postoperative therapy.

Clinical Study of Time Optimizing of Endoscopic Photodynamic Therapy on Esophageal and/or Gastric Cardiac Cancer

ClinicalTrials.gov

2015-12-10

Stage I Esophageal Adenocarcinoma; Stage II Esophageal Adenocarcinoma; Stage III Esophageal Adenocarcinoma; Stage I Esophageal Squamous Cell Carcinoma; Stage II Esophageal Squamous Cell Carcinoma; Stage III Esophageal Squamous Cell Carcinoma

64Cu DOTA-Trastuzumab PET/CT in Studying Patients With Gastric Cancer

ClinicalTrials.gov

2017-12-11

Adenocarcinoma of the Gastroesophageal Junction; Diffuse Adenocarcinoma of the Stomach; Intestinal Adenocarcinoma of the Stomach; Mixed Adenocarcinoma of the Stomach; Recurrent Gastric Cancer; Stage IA Gastric Cancer; Stage IB Gastric Cancer; Stage IIA Gastric Cancer; Stage IIB Gastric Cancer; Stage IIIA Gastric Cancer; Stage IIIB Gastric Cancer; Stage IIIC Gastric Cancer; Stage IV Gastric Cancer

Prospective Cohort Study Depending on the Use of Palliative Care for Advanced Stage of Cancer Patients

ClinicalTrials.gov

2017-09-05

Stage IV Breast Cancer; Stage IV Pancreatic Cancer; Stage IV Colon Cancer; Stage IV Gastric Cancer; Stage IV Lung Cancer; Stage IV Liver Cancer; Malignant Hematologic Neoplasm; Biliary Cancer Metastatic; Pediatric Leukemia; Pediatric Lymphoma; Pediatric Brain Tumor; Pediatric Solid Tumor

Bilateral Total Hip Arthroplasty: 1-Stage or 2-Stage? A Meta-Analysis.

PubMed

Shao, Hongyi; Chen, Chi-Lung; Maltenfort, Mitchell G; Restrepo, Camilo; Rothman, Richard H; Chen, Antonia F

2017-02-01

Total hip arthroplasty (THA) is one of the most successful orthopedic surgeries performed in the last 50 years. However, controversies still exist between conducting 1- or 2-stage bilateral THA. Using PubMed, Ovid, Embase, and Cochrane library databases, we searched for papers written between January 1995 and October 2015 that contained the following search terms: "one-stage or two-stage" or "simultaneous or staged," and "hip" and "arthroplasty or replacement." A meta-analysis was conducted with the collected pooled data about major and minor systemic complications, surgical complications, and other perioperative data associated with 1- and 2-stage bilateral THA. Statistical analysis was performed by the Mantel-Haenszel method, and the fixed effect model was used to analyze data. There were 13 studies with 17,762 patients who underwent 1-stage bilateral THA and 46,147 patients who underwent 2-stage bilateral THA. One-stage bilateral THA had a lower risk of major systemic complications, less deep venous thrombosis, and shorter operative time compared with 2-stage bilateral THA. There were no significant differences in death, pulmonary embolism, cardiovascular complication, infections, minor complications, and other surgical complications between procedures. One-stage bilateral THA was superior to 2-stage bilateral THA in terms of major systemic complication, deep venous thrombosis, and surgical time compared with 2-stage bilateral THA. However, this study does not encourage performing 1-stage over 2-stage bilateral THA. Higher evidence level studies are necessary for further analysis. Copyright © 2016 Elsevier Inc. All rights reserved.

Oral submucous fibrosis: A clinico-histopathological correlational study.

PubMed

Biradar, Sudharani Basawaraj; Munde, Anita Dnyanoba; Biradar, Basawaraj Chanabasappa; Shaik, Safia Shoeb; Mishra, Shweta

2018-01-01

The aim of this study was to correlate the clinical staging (clinical severity) with the histopathological staging (histopathological changes) of oral submucous fibrosis (OSF) patients, which would further assist the clinicians to formulate a definite treatment plan. The study group consisted of 50 subjects who were clinically and histologically diagnosed as OSF. Detailed information was gathered in a pretested proforma with emphasis on the various addictions. The clinical findings were noted; punch biopsy was performed followed by histological examination. Clinical and histological staging were divided into four stages, as Stages I-IV according to Khanna and Andrade classification. The 50 subjects were in the age range of 18-70 years, of which 20 patients were in clinical Group III, 15 were in histopathological stage III, 2, 1, and 2 in Stage II, Stage I, and Stage IV, respectively, out of 5 patients in clinical Group IV, 4 were in histopathological staging IV and 1 was in Stage III, out of 5 patients in clinical Group I, 3 and 2 were in histologic Stages II and I, respectively. Statistical analysis with Chi-square test showed high significance with P < 0.001. The correlation of clinical and histopathological staging was found to be highly significant, thus suggesting that the subject with clinically advanced OSF had extensive fibrosis histologically.

The Pediatric Oncology Group experience with the international staging system criteria for neuroblastoma. Member Institutions of the Pediatric Oncology Group.

PubMed

Castleberry, R P; Shuster, J J; Smith, E I

1994-11-01

An international consensus on the criteria for surgicopathologic staging (INSS) of patients with neuroblastoma has been published, but has not been validated. A retrospective study was conducted to assess if the INSS definitions identified prognostic subsets of patients with neuroblastoma. The initial operative and pathology reports were reviewed from 675 patients on Pediatric Oncology Group (POG) #8104, a stage- and age-related treatment study that used the POG surgicopathologic staging system. Of 596 eligible cases, there was concordance between the POG and INSS stages for the 193 patients with localized, resected disease (POG stage A), the 202 with distant metastases, the 51 with POG stage Ds (IVs) tumors, and 40 of the cases with grossly unresected, localized tumor without lymph node involvement (POG stage B). Of the remaining 19 patients with POG stage B tumors, five were INSS stage 2B and 14 INSS stage 3. All of the 91 cases with nonadherent, regional lymph node metastases (POG stage C) conformed to the definitions for INSS stage 2B (n = 42) or 3 (n = 49). In infants, there was no difference in event-free survival (EFS) among INSS stages 2A, 2B, or 3. In contrast, older children with INSS stage 3 disease had inferior EFS compared with INSS stage 2A or 2B tumors. We conclude the following: (1) the INSS identifies distinct patient subsets, particularly in children; (2) infants remain a favorable group, regardless of INSS/POG stage; and (3) the INSS deserves further prospective study especially in the light of recent biologic prognostic variables.

[Factors associated with advanced thyroid cancer in pediatric patients in a high specialty medical unit in Northeast Mexico].

PubMed

García-Castillo, Lizbeth Ariana; Bahena-García, Ana Laura; Sánchez-Sánchez, Luz María; del Carmen Palacios-Saucedo, Gerardo

2015-01-01

Thyroid cancer represents 2% of all childhood malignances. Its incidence rises 1.1% per year. In comparison with adults, childhood thyroid cancer is detected in a more advanced stage, but with a survival rate above 95%. The objective of this study was to evaluate whether there are factors associated with advanced stages of thyroid cancer in pediatric patients. Nineteen patients were included, 13 (68.4%) were female and six male, all between 7-15 years, with a median of 11 years. Fifteen in advanced and four in early stage. The median age of patients in advanced stage at time of diagnosis was 10.6 years (7-15) and 13.2 (12-14) were in early stage (p=0.075). There was a delay of nine months to get a diagnosis in advanced stage, and 7.2 in early stage (p=0.931). Three of the patients with advanced stage and two with early stage were from Nuevo León (Mexico) and the rest were foreign (p=0.567). In the group with advanced stage, two had thyroid cancer familiar history, and none in the early stage group (p=0.452). Nine patients in advanced stage and three in early stage presented thyroid nodule as the first sign of illness. Six patients in advanced stage and one in early stage presented goiter (p=0.590). None of the studied patients had radiation history. Six patients in advanced stage and one in early stage suffered from Hashimoto's Thyroiditis (p=0.590). Eleven in advanced stage and one in early stage had papillary histologic variety. Four in advanced stage and three in early stage had papillary histologic variety with a follicular patter (p=0.083). Eight patients presented lung metastasis at time of diagnosis (p=0.061). There are no factors associated with advanced stage thyroid cancer in pediatric populations. Although half of studied patients presented lung metastasis, treatment response and survival is satisfactory.

A Study to Evaluate Genetic Predictors of Aromatase Inhibitor Musculoskeletal Symptoms (AIMSS)

ClinicalTrials.gov

2015-05-07

Estrogen Receptor-positive Breast Cancer; Musculoskeletal Complications; Progesterone Receptor-positive Breast Cancer; Recurrent Breast Cancer; Stage IA Breast Cancer; Stage IB Breast Cancer; Stage II Breast Cancer; Stage IIIA Breast Cancer; Stage IIIB Breast Cancer; Stage IIIC Breast Cancer

A new model for the spectral induced polarization signature of bacterial growth in porous media

NASA Astrophysics Data System (ADS)

Zhang, C.; Revil, A.; Atekwana, E. A.; Jardani, A.; Smith, S.

2012-12-01

Recent biogeophysics studies demonstrated the sensitivity of complex conductivity to bacterial growth and microbial mediated mineral transformations in porous media. Frequency-domain induced polarization is a minimally invasive manner to measure the complex conductivity of a material over a broad range of frequencies. The real component of complex conductivity is associated with electromigration of the charge carriers, and the imaginary component represents reversible energy storage of charge carriers at polarization length scales. Quantitative relationship between frequency-domain induced polarization responses and bacterial growth and decay in porous media is analyzed in this study using a new developed model. We focus on the direct contribution of bacteria themselves to the complex conductivity in porous media in the absence of biomineralization. At low frequencies, the induced polarization of bacteria (α-polarization) is related to the properties of the electrical double layer surrounding the membrane surface of bacteria. Surface conductivity and α-polarization are due to the Stern layer of the counterions occurring in a brush of polymers coating the surface of the bacteria, and can be related to the cation exchange capacity of the bacteria. From the modeling results, at low frequencies (< 10 Hz), the mobility of the counterions (K+) in the Stern layer of bacteria is found to be extremely small (4.7×10-10 m2s-1 V-1 at 25°C), and is close to the mobility of the same counterions along the surface of clay minerals (Na+, 1.5×10-10 m2s-1 V-1 at 25°C). This result is in agreement with experimental observations and it indicates a very low relaxation frequency for the α-polarization of the bacteria cells (typically around 0.1 to 5 Hertz). By coupling this new model with reactive transport modeling in which the evolution of bacterial populations are usually described by Monod kinetics, we show that the changes in imaginary conductivity with time can be used to determine bacterial growth kinetics parameters such as the growth and endogenous decay coefficient.

Review of health information technology usability study methodologies

PubMed Central

Bakken, Suzanne

2011-01-01

Usability factors are a major obstacle to health information technology (IT) adoption. The purpose of this paper is to review and categorize health IT usability study methods and to provide practical guidance on health IT usability evaluation. 2025 references were initially retrieved from the Medline database from 2003 to 2009 that evaluated health IT used by clinicians. Titles and abstracts were first reviewed for inclusion. Full-text articles were then examined to identify final eligibility studies. 629 studies were categorized into the five stages of an integrated usability specification and evaluation framework that was based on a usability model and the system development life cycle (SDLC)-associated stages of evaluation. Theoretical and methodological aspects of 319 studies were extracted in greater detail and studies that focused on system validation (SDLC stage 2) were not assessed further. The number of studies by stage was: stage 1, task-based or user–task interaction, n=42; stage 2, system–task interaction, n=310; stage 3, user–task–system interaction, n=69; stage 4, user–task–system–environment interaction, n=54; and stage 5, user–task–system–environment interaction in routine use, n=199. The studies applied a variety of quantitative and qualitative approaches. Methodological issues included lack of theoretical framework/model, lack of details regarding qualitative study approaches, single evaluation focus, environmental factors not evaluated in the early stages, and guideline adherence as the primary outcome for decision support system evaluations. Based on the findings, a three-level stratified view of health IT usability evaluation is proposed and methodological guidance is offered based upon the type of interaction that is of primary interest in the evaluation. PMID:21828224

Phase I Study of Neoadjuvant Radiotherapy With 5-Fluorouracil for Rectal Cancer

ClinicalTrials.gov

2017-09-14

Mucinous Adenocarcinoma of the Rectum; Recurrent Rectal Cancer; Signet Ring Adenocarcinoma of the Rectum; Rectal Adenocarcinoma; Stage IIA Rectal Cancer; Stage IIB Rectal Cancer; Stage IIC Rectal Cancer; Stage IIIA Rectal Cancer; Stage IIIB Rectal Cancer; Stage IIIC Rectal Cancer

Correlation of the cell surface antigens with stage and grade in cancer of the bladder.

PubMed

Emmott, R C; Javadpour, N; Bergman, S M; Soares, T

1979-01-01

We examined 76 bladder tumors of various stages and grades for the presence of the ABO (H) cell surface antigen, using the specific red cell adherence technique. Of the grade I lesions studied 70 per cent were positive for the cell surface antigen and none of the 26 grade III tumors retained the antigens. When correlated with clinical stage the tumors showed no antigens for those of stages B1 to D, while 12 of 16 stage A lesions were positive for the antigen. When stage A lesions were studied and the findings were correlated with recurrence and metastasis/invasion rates the cell surface antigen was present on the initial tumor in only 1 lesion that recurred at an invasive stage. The findings of this study show that the specific red cell adherence technique may be valuable for predicting malignant potential in low grade, low stage cancer of the bladder. If supported by further investigation this technique may offer the capability of selecting low grade, low stage bladder tumors that are destined to invade or metastasize while they are at curable stages.

Influences of electric current on the wettability and interfacial microstructure in Sn/Fe system

NASA Astrophysics Data System (ADS)

Shen, Ping; Gu, Yan; Yang, Nan-Nan; Zheng, Rui-Peng; Ren, Li-Hua

2015-02-01

The wettability of oxidized and clean Fe substrates by liquid Sn was investigated using a dispensed sessile drop method with and without the application of a direct current (DC) and their interfacial microstructures were compared. The initial contact angles were 107 ± 3° at 623 K when the Fe substrate was covered by an oxide film, and they did not show an appreciable decrease during isothermal dwells in the absence of DC application but progressively decreased to 42 ± 3° when a 7.5 ampere current was applied. However, in the case of the oxide film being removed by a high-vacuum pre-annealing treatment at 1073 K, the current and its polarity had a negligible effect on the wetting behavior. Nevertheless, they had a noticeable influence on the interfacial microstructure. In the absence of DC, the interface was covered by a product layer consisting of a single FeSn2 phase for the samples tested at 623 K and the FeSn2/FeSn2 grain boundaries were incompletely wetted by the Sn melt; whereas, under DC, the reaction layer was much thicker and the Sn melt wet well the FeSn2/FeSn2 grain boundaries. Moreover, a FeSn phase also formed as a result of enhanced mass transfer. The amount of the FeSn phase was larger and the grain boundary wetting of FeSn2 by liquid Sn was better for the current flowing from the molten Sn drop to the Fe substrate due to an electromigration effect.

Nanocrystallized SrHA/SrHA SrTiO3/SrTiO3 TiO2 multilayer coatings formed by micro-arc oxidation for photocatalytic application

NASA Astrophysics Data System (ADS)

Han, Y.; Chen, D. H.; Zhang, L.

2008-08-01

Novel photocatalytic coatings containing strontium hydroxyapatite (SrHA), strontium titanate (SrTiO3), and TiO2 were formed by micro-arc oxidation (MAO) in an aqueous electrolyte containing strontium acetate and β-glycerophosphate disodium at 530 V for 0.1-5 min. The structure evolution of the coatings was investigated as a function of processing time, and the photocatalytic activity of the coatings was evaluated by measuring the decomposition rate of methyl orange under ultraviolet irradiation. During the MAO processing of the coatings, it was observed that some granules appeared in the electrolyte adjacent to the anode and they increased in amount as the processing time was prolonged. The obtained results show that the granules are amorphous and poorly crystallized SrHA with negative charges. The coating prepared for 5 min presents a microporous structure of SrHA/SrHA-SrTiO3/SrTiO3-TiO2 multilayers, in which the SrHA outermost layer and the SrHA-SrTiO3 intermediate layer are nanocrystallized. It is suggested that formation of the granules, electro-migration of the granules onto the pre-formed layer, and crystallization of the adhered granules are possible mechanisms for the formation of a SrHA/SrHA-SrTiO3/SrTiO3-TiO2 multilayer coating. This coating shows much higher photocatalytic decomposition efficiency relative to the MAO-formed TiO2 coating, and is expected to have an important photocatalytic application.

Dilemmas across different overseas liver transplant stages: Taiwan transplant recipient families' perspectives.

PubMed

Chen, H-M; Hu, R-H; Shih, F-Jong; Shih, F-J

2012-03-01

This study aimed to explore the dilemmas of Taiwanese overseas liver transplant recipient families (OLTRF) across three overseas liver transplant (OLT) stages in Taiwan and Mainland China. An exploratory qualitative method was employed using a purposive sample of OLTRF, who received guided face-to-face, semistructured interviews. Data were subjected to content analysis. Nineteen OLTRF (15 female, 4 male) aged between 29 and 71 years (mean 55.1) for 19 patients with end-stage liver diseases were interviewed. OLT stages including predeparture stage (first stage), stay in China stage (second stage), and reentry to Taiwan stage (third stage). Ten kinds of dilemmas were encountered: (1) unable to get transplantation immediately (first to second stages); (2) dilemma of choosing overseas transplantation (first to second stages); (3) uncertainty about the transplantation outcomes (second to third stages); (4) care pressure (second to third stages); (5) poor diet adaptation (second to third stages); (6) lack of trust in the medical care quality (second stage); (7) worry about not fulfilling family responsibilities (second stage); (8) lack of information (all stages); (9) financial pressure (all stages); and (10) frustration when seeking medical care (all stages). Taiwanese OLTRF's perspectives of their dilemmas through the OLT process were first revealed in this study. Both Western and Eastern health professionals might be empowered by better understanding of OLTRF's living experiences and concerns during the stages of overseas liver transplantation. Copyright © 2012 Elsevier Inc. All rights reserved.

Cutaneous Lymphoma International Consortium Study of Outcome in Advanced Stages of Mycosis Fungoides and Sézary Syndrome: Effect of Specific Prognostic Markers on Survival and Development of a Prognostic Model

PubMed Central

Scarisbrick, Julia J.; Prince, H. Miles; Vermeer, Maarten H.; Quaglino, Pietro; Horwitz, Steven; Porcu, Pierluigi; Stadler, Rudolf; Wood, Gary S.; Beylot-Barry, Marie; Pham-Ledard, Anne; Foss, Francine; Girardi, Michael; Bagot, Martine; Michel, Laurence; Battistella, Maxime; Guitart, Joan; Kuzel, Timothy M.; Martinez-Escala, Maria Estela; Estrach, Teresa; Papadavid, Evangelia; Antoniou, Christina; Rigopoulos, Dimitis; Nikolaou, Vassilki; Sugaya, Makoto; Miyagaki, Tomomitsu; Gniadecki, Robert; Sanches, José Antonio; Cury-Martins, Jade; Miyashiro, Denis; Servitje, Octavio; Muniesa, Cristina; Berti, Emilio; Onida, Francesco; Corti, Laura; Hodak, Emilia; Amitay-Laish, Iris; Ortiz-Romero, Pablo L.; Rodríguez-Peralto, Jose L.; Knobler, Robert; Porkert, Stefanie; Bauer, Wolfgang; Pimpinelli, Nicola; Grandi, Vieri; Cowan, Richard; Rook, Alain; Kim, Ellen; Pileri, Alessandro; Patrizi, Annalisa; Pujol, Ramon M.; Wong, Henry; Tyler, Kelly; Stranzenbach, Rene; Querfeld, Christiane; Fava, Paolo; Maule, Milena; Willemze, Rein; Evison, Felicity; Morris, Stephen; Twigger, Robert; Talpur, Rakhshandra; Kim, Jinah; Ognibene, Grant; Li, Shufeng; Tavallaee, Mahkam; Hoppe, Richard T.; Duvic, Madeleine; Whittaker, Sean J.; Kim, Youn H.

2015-01-01

Purpose Advanced-stage mycosis fungoides (MF; stage IIB to IV) and Sézary syndrome (SS) are aggressive lymphomas with a median survival of 1 to 5 years. Clinical management is stage based; however, there is wide range of outcome within stages. Published prognostic studies in MF/SS have been single-center trials. Because of the rarity of MF/SS, only a large collaboration would power a study to identify independent prognostic markers. Patients and Methods Literature review identified the following 10 candidate markers: stage, age, sex, cutaneous histologic features of folliculotropism, CD30 positivity, proliferation index, large-cell transformation, WBC/lymphocyte count, serum lactate dehydrogenase, and identical T-cell clone in blood and skin. Data were collected at specialist centers on patients diagnosed with advanced-stage MF/SS from 2007. Each parameter recorded at diagnosis was tested against overall survival (OS). Results Staging data on 1,275 patients with advanced MF/SS from 29 international sites were included for survival analysis. The median OS was 63 months, with 2- and 5-year survival rates of 77% and 52%, respectively. The median OS for patients with stage IIB disease was 68 months, but patients diagnosed with stage III disease had slightly improved survival compared with patients with stage IIB, although patients diagnosed with stage IV disease had significantly worse survival (48 months for stage IVA and 33 months for stage IVB). Of the 10 variables tested, four (stage IV, age > 60 years, large-cell transformation, and increased lactate dehydrogenase) were independent prognostic markers for a worse survival. Combining these four factors in a prognostic index model identified the following three risk groups across stages with significantly different 5-year survival rates: low risk (68%), intermediate risk (44%), and high risk (28%). Conclusion To our knowledge, this study includes the largest cohort of patients with advanced-stage MF/SS and identifies markers with independent prognostic value, which, used together in a prognostic index, may be useful to stratify advanced-stage patients. PMID:26438120

Cutaneous Lymphoma International Consortium Study of Outcome in Advanced Stages of Mycosis Fungoides and Sézary Syndrome: Effect of Specific Prognostic Markers on Survival and Development of a Prognostic Model.

PubMed

Scarisbrick, Julia J; Prince, H Miles; Vermeer, Maarten H; Quaglino, Pietro; Horwitz, Steven; Porcu, Pierluigi; Stadler, Rudolf; Wood, Gary S; Beylot-Barry, Marie; Pham-Ledard, Anne; Foss, Francine; Girardi, Michael; Bagot, Martine; Michel, Laurence; Battistella, Maxime; Guitart, Joan; Kuzel, Timothy M; Martinez-Escala, Maria Estela; Estrach, Teresa; Papadavid, Evangelia; Antoniou, Christina; Rigopoulos, Dimitis; Nikolaou, Vassilki; Sugaya, Makoto; Miyagaki, Tomomitsu; Gniadecki, Robert; Sanches, José Antonio; Cury-Martins, Jade; Miyashiro, Denis; Servitje, Octavio; Muniesa, Cristina; Berti, Emilio; Onida, Francesco; Corti, Laura; Hodak, Emilia; Amitay-Laish, Iris; Ortiz-Romero, Pablo L; Rodríguez-Peralto, Jose L; Knobler, Robert; Porkert, Stefanie; Bauer, Wolfgang; Pimpinelli, Nicola; Grandi, Vieri; Cowan, Richard; Rook, Alain; Kim, Ellen; Pileri, Alessandro; Patrizi, Annalisa; Pujol, Ramon M; Wong, Henry; Tyler, Kelly; Stranzenbach, Rene; Querfeld, Christiane; Fava, Paolo; Maule, Milena; Willemze, Rein; Evison, Felicity; Morris, Stephen; Twigger, Robert; Talpur, Rakhshandra; Kim, Jinah; Ognibene, Grant; Li, Shufeng; Tavallaee, Mahkam; Hoppe, Richard T; Duvic, Madeleine; Whittaker, Sean J; Kim, Youn H

2015-11-10

Advanced-stage mycosis fungoides (MF; stage IIB to IV) and Sézary syndrome (SS) are aggressive lymphomas with a median survival of 1 to 5 years. Clinical management is stage based; however, there is wide range of outcome within stages. Published prognostic studies in MF/SS have been single-center trials. Because of the rarity of MF/SS, only a large collaboration would power a study to identify independent prognostic markers. Literature review identified the following 10 candidate markers: stage, age, sex, cutaneous histologic features of folliculotropism, CD30 positivity, proliferation index, large-cell transformation, WBC/lymphocyte count, serum lactate dehydrogenase, and identical T-cell clone in blood and skin. Data were collected at specialist centers on patients diagnosed with advanced-stage MF/SS from 2007. Each parameter recorded at diagnosis was tested against overall survival (OS). Staging data on 1,275 patients with advanced MF/SS from 29 international sites were included for survival analysis. The median OS was 63 months, with 2- and 5-year survival rates of 77% and 52%, respectively. The median OS for patients with stage IIB disease was 68 months, but patients diagnosed with stage III disease had slightly improved survival compared with patients with stage IIB, although patients diagnosed with stage IV disease had significantly worse survival (48 months for stage IVA and 33 months for stage IVB). Of the 10 variables tested, four (stage IV, age > 60 years, large-cell transformation, and increased lactate dehydrogenase) were independent prognostic markers for a worse survival. Combining these four factors in a prognostic index model identified the following three risk groups across stages with significantly different 5-year survival rates: low risk (68%), intermediate risk (44%), and high risk (28%). To our knowledge, this study includes the largest cohort of patients with advanced-stage MF/SS and identifies markers with independent prognostic value, which, used together in a prognostic index, may be useful to stratify advanced-stage patients. © 2015 by American Society of Clinical Oncology.

Re-Infection Outcomes following One- and Two-Stage Surgical Revision of Infected Hip Prosthesis: A Systematic Review and Meta-Analysis

PubMed Central

Kunutsor, Setor K.; Whitehouse, Michael R.; Blom, Ashley W.; Beswick, Andrew D.

2015-01-01

Background The two-stage revision strategy has been claimed as being the “gold standard” for treating prosthetic joint infection. The one-stage revision strategy remains an attractive alternative option; however, its effectiveness in comparison to the two-stage strategy remains uncertain. Objective To compare the effectiveness of one- and two-stage revision strategies in treating prosthetic hip infection, using re-infection as an outcome. Design Systematic review and meta-analysis. Data Sources MEDLINE, EMBASE, Web of Science, Cochrane Library, manual search of bibliographies to March 2015, and email contact with investigators. Study Selection Cohort studies (prospective or retrospective) conducted in generally unselected patients with prosthetic hip infection treated exclusively by one- or two-stage revision and with re-infection outcomes reported within two years of revision. No clinical trials were identified. Review Methods Data were extracted by two independent investigators and a consensus was reached with involvement of a third. Rates of re-infection from 38 one-stage studies (2,536 participants) and 60 two-stage studies (3,288 participants) were aggregated using random-effect models after arcsine transformation, and were grouped by study and population level characteristics. Results In one-stage studies, the rate (95% confidence intervals) of re-infection was 8.2% (6.0–10.8). The corresponding re-infection rate after two-stage revision was 7.9% (6.2–9.7). Re-infection rates remained generally similar when grouped by several study and population level characteristics. There was no strong evidence of publication bias among contributing studies. Conclusion Evidence from aggregate published data suggest similar re-infection rates after one- or two-stage revision among unselected patients. More detailed analyses under a broader range of circumstances and exploration of other sources of heterogeneity will require collaborative pooling of individual participant data. Systematic Review Registration PROSPERO 2015: CRD42015016559 PMID:26407003

Two-stage revision of septic knee prosthesis with articulating knee spacers yields better infection eradication rate than one-stage or two-stage revision with static spacers.

PubMed

Romanò, C L; Gala, L; Logoluso, N; Romanò, D; Drago, L

2012-12-01

The best method for treating chronic periprosthetic knee infection remains controversial. Randomized, comparative studies on treatment modalities are lacking. This systematic review of the literature compares the infection eradication rate after two-stage versus one-stage revision and static versus articulating spacers in two-stage procedures. We reviewed full-text papers and those with an abstract in English published from 1966 through 2011 that reported the success rate of infection eradication after one-stage or two-stage revision with two different types of spacers. In all, 6 original articles reporting the results after one-stage knee exchange arthoplasty (n = 204) and 38 papers reporting on two-stage revision (n = 1,421) were reviewed. The average success rate in the eradication of infection was 89.8% after a two-stage revision and 81.9% after a one-stage procedure at a mean follow-up of 44.7 and 40.7 months, respectively. The average infection eradication rate after a two-stage procedure was slightly, although significantly, higher when an articulating spacer rather than a static spacer was used (91.2 versus 87%). The methodological limitations of this study and the heterogeneous material in the studies reviewed notwithstanding, this systematic review shows that, on average, a two-stage procedure is associated with a higher rate of eradication of infection than one-stage revision for septic knee prosthesis and that articulating spacers are associated with a lower recurrence of infection than static spacers at a comparable mean duration of follow-up. IV.

Rho-Isp Revisited and Basic Stage Mass Estimating for Launch Vehicle Conceptual Sizing Studies

NASA Technical Reports Server (NTRS)

Kibbey, Timothy P.

2015-01-01

The ideal rocket equation is manipulated to demonstrate the essential link between propellant density and specific impulse as the two primary stage performance drivers for a launch vehicle. This is illustrated by examining volume-limited stages such as first stages and boosters. This proves to be a good approximation for first-order or Phase A vehicle design studies for solid rocket motors and for liquid stages, except when comparing to hydrogen-fueled stages. A next-order mass model is developed that is able to model the mass differences between hydrogen-fueled and other stages. Propellants considered range in density from liquid methane to inhibited red fuming nitric acid. Calculated comparisons are shown for solid rocket boosters, liquid first stages, liquid upper stages, and a balloon-deployed single-stage-to-orbit concept. The derived relationships are ripe for inclusion in a multi-stage design space exploration and optimization algorithm, as well as for single-parameter comparisons such as those shown herein.

Research Productivity by Career Stage among Korean Academics

ERIC Educational Resources Information Center

Jung, Jisun

2014-01-01

This study explores Korean academics' changes in research productivity by career stage. Career stage in this study is defined as a specific cohort based on one's length of job experience, with those in the same stage sharing similar interests, values, needs, and tasks; it is categorized into fledglings, maturing academics, established academics,…

Lunar lander and return propulsion system trade study

NASA Technical Reports Server (NTRS)

Hurlbert, Eric A.; Moreland, Robert; Sanders, Gerald B.; Robertson, Edward A.; Amidei, David; Mulholland, John

1993-01-01

This trade study was initiated at NASA/JSC in May 1992 to develop and evaluate main propulsion system alternatives to the reference First Lunar Outpost (FLO) lander and return-stage transportation system concept. Thirteen alternative configurations were developed to explore the impacts of various combinations of return stage propellants, using either pressure or pump-fed propulsion systems and various staging options. Besides two-stage vehicle concepts, the merits of single-stage and stage-and-a-half options were also assessed in combination with high-performance liquid oxygen and liquid hydrogen propellants. Configurations using an integrated modular cryogenic engine were developed to assess potential improvements in packaging efficiency, mass performance, and system reliability compared to non-modular cryogenic designs. The selection process to evaluate the various designs was the analytic hierarchy process. The trade study showed that a pressure-fed MMH/N2O4 return stage and RL10-based lander stage is the best option for a 1999 launch. While results of this study are tailored to FLO needs, the design date, criteria, and selection methodology are applicable to the design of other crewed lunar landing and return vehicles.

The Prognostic Value of the 8th Edition of the American Joint Committee on Cancer (AJCC) Staging System in HER2-Enriched Subtype Breast Cancer, a Retrospective Analysis.

PubMed

Zhou, Bin; Xu, Ling; Ye, Jingming; Xin, Ling; Duan, Xuening; Liu, Yinhua

2017-08-01

The American Joint Committee on Cancer (AJCC) released its 8th edition of tumor staging which is to be implemented in early 2018. The present study aimed to analyze the prognostic value of AJCC 8th edition Cancer Staging System in HER2-enriched breast cancer, on a retrospective cohort. This study was a retrospective single-center study of HER2-enriched breast cancer cases diagnosed from January 2008 to December 2014. Clinicopathological features and follow up data including disease-free survival (DFS) and overall survival (OS) were analyzed to explore prognostic factors for disease outcome. We restaged patients based on the 8th edition of the AJCC cancer staging system and analyzed prognostic value of the Anatomic Stage Group and the Prognostic Stage Group. The study enrolled 170 HER2-enriched subtype breast cancer patients with 5-year disease free survival (DFS) of 85.1% and 5-year overall survival (OS) of 86.8%. Prognostic stages of 117 cases (68.8%) changed compared with anatomic stages, with 116 upstaged cases and 1 downstaged case. The Anatomic Stage Groups had a significant prognostic impact on DFS (χ 2 =16.752, p<0.001) and OS (χ 2 =25.038, p<0.001). The Prognostic Staging Groups had a significant prognostic impact on DFS (χ 2 =6.577, p=0.037) and OS (χ 2 =21.762, p<0.001). In the multivariate analysis, both stage groups were independent predictors of OS. Both Anatomic and Prognostic Stage Groups in the 8th edition of the AJCC breast cancer staging system had prognostic value in HER2-enriched subtype breast cancer. The Prognostic Stage system was a breakthrough on the basis of anatomic staging system. Copyright© 2017, International Institute of Anticancer Research (Dr. George J. Delinasios), All rights reserved.

Odor and VOC Emissions from Pan Frying of Mackerel at Three Stages: Raw, Well-Done, and Charred

PubMed Central

Ahn, Jeong-Hyeon; Szulejko, Jan E.; Kim, Ki-Hyun; Kim, Yong-Hyun; Kim, Bo-Won

2014-01-01

Many classes of odorants and volatile organic compounds that are deleterious to our wellbeing can be emitted from diverse cooking activities. Once emitted, they can persist in our living space for varying durations. In this study, various volatile organic compounds released prior to and during the pan frying of fish (mackerel) were analyzed at three different cooking stages (stage 1 = raw (R), stage 2 = well-done (W), and stage 3 = overcooked/charred (O)). Generally, most volatile organic compounds recorded their highest concentration levels at stage 3 (O), e.g., 465 (trimethylamine) and 106 ppb (acetic acid). In contrast, at stage 2 (W), the lowest volatile organic compounds emissions were observed. The overall results of this study confirm that trimethylamine is identified as the strongest odorous compound, especially prior to cooking (stage 1 (R)) and during overcooking leading to charring (stage 3 (O)). As there is a paucity of research effort to measure odor intensities from pan frying of mackerel, this study will provide valuable information regarding the management of indoor air quality. PMID:25405596

Developmental Stages in School Computer Use: Neither Marx Nor Piaget.

ERIC Educational Resources Information Center

Lengel, James G.

Karl Marx's theory of stages can be applied to computer use in the schools. The first stage, the P Stage, comprises the entry of the computer into the school. Computer use at this stage is personal and tends to center around one personality. Social studies teachers are seldom among this select few. The second stage of computer use, the D Stage, is…

Timing of maturation and predictors of Tanner stage transitions in boys enrolled in a contemporary British cohort.

PubMed

Monteilh, Carolyn; Kieszak, Stephanie; Flanders, W Dana; Maisonet, Mildred; Rubin, Carol; Holmes, Adrianne K; Heron, Jon; Golding, Jean; McGeehin, Michael A; Marcus, Michele

2011-01-01

This study describes the timing of puberty in 8- to 14-year-old boys enrolled in the Avon Longitudinal Study of Parents and Children (ALSPAC) and identifies factors associated with earlier achievement of advanced pubic hair stages. Women were enrolled during pregnancy and their offspring were followed prospectively. We analysed self-reported pubic hair Tanner staging collected annually. We used survival models to estimate median age of attainment of pubic hair stage >1, stage >2 and stage >3 of pubic hair development. We also constructed multivariable logistic regression models to identify factors associated with earlier achievement of pubic hair stages. Approximately 5% of the boys reported Tanner pubic hair stage >1 at age 8; 99% of boys were at stage >1 by age 14. The estimated median ages of entry into stages of pubic hair development were 11.4 years [95% confidence interval (CI) 11.3, 11.4] for stage >1, 12.7 years [95% CI 12.7, 12.8] for stage >2 and 13.5 years [95% CI 13.5, 13.6] for stage >3. Predictors of younger age at Tanner stage >1 included low birthweight, younger maternal age at delivery and being taller at age 8. Associations were found between younger age at attainment of stage >2 and gestational diabetes and taller or heavier body size at age 8. Being taller or heavier at age 8 also predicted younger age at Tanner stage >3. The results give added support to the strong influence of pre-adolescent body size on male pubertal development; the tallest and heaviest boys at 8 years achieved each stage earlier and the shortest boys later. Age at attainment of pubic hair Tanner stages in the ALSPAC cohort are similar to ages reported in other European studies that were conducted during overlapping time periods. This cohort will continue to be followed for maturational information until age 17. © 2010 Blackwell Publishing Ltd.

Core compressor exit stage study. Volume 4: Data and performance report for the best stage configuration

NASA Technical Reports Server (NTRS)

Wisler, D. C.

1981-01-01

The core compressor exit stage study program develops rear stage blading designs that have lower losses in their endwall boundary layer regions. The test data and performance results for the best stage configuration consisting of Rotor-B running with Stator-B are described. The technical approach in this efficiency improvement program utilizes a low speed research compressor. Tests were conducted in two ways: (1) to use four identical stages of blading to obtain test data in a true multistage environment and (2) to use a single stage of blading to compare with the multistage test results. The effects of increased rotor tip clearances and circumferential groove casing treatment are evaluated.

Development of molecular markers for zebrafish (Danio rerio) ovarian follicle growth assessment following in-vitro culture in cryopreservation studies.

PubMed

Anil, Siji; Rawson, David; Zhang, Tiantian

2018-05-29

Development of in vitro culture protocol for early stage ovarian follicles of zebrafish is important since cryopreserved early stage ovarian follicles would need to be matured in vitro following cryopreservation before they can be fertilised. Development of molecular markers for zebrafish (Danio rerio) ovarian follicle growth assessment following in vitro culture of early stage zebrafish ovarian follicles in ovarian tissue fragments is reported here for the first time although some work has been reported for in vitro culture of isolated early stage zebrafish ovarian follicles. The main aim of the present study was to develop molecular markers in an optimised in vitro culture protocol for stage I and stage II zebrafish ovarian follicles in ovarian tissue fragments. The effect of concentration of the hormones human chorionic gonadotropin and follicle stimulating hormones, and additives such as Foetal Bovine Serum and Bovine Serum Albumin were studied. The results showed that early stage zebrafish ovarian fragments containing stage I and stage II follicles which are cultured in vitro for 24 h in 20% FBS and 100mIU/ml FSH in 90% L-15 medium at 28 °C can grow to the size of stage II and stage III ovarian follicles respectively. More importantly the follicle growth from stage I to stage II and from stage II to stage III were confirmed using molecular markers such as cyp19a1a (also known as P450aromA) and vtg1 genes respectively. However, no follicle growth was observed following cryopreservation and in vitro culture. Copyright © 2018 Elsevier Inc. All rights reserved.

Cross-sectional analysis of penile length in males 13 to 15 years old according to pubertal development stages.

PubMed

Soydan, Hasan; Akyol, İlker; Ates, Ferhat; Yilmaz, Omer; Dursun, Furkan; Baykal, Kadir

2012-10-01

Genital development is affected by pubertal process to a great extent, and puberty is a complex phenomenon that is influenced by multiple factors resulting in individual differences. We studied penile length and its relationship to pubertal stage in boys 13 to 15 years old. Healthy boys who were candidates for military high school were evaluated between June and July 2011. Age, residence and body mass index were recorded. Stretched penile length was measured. Pubic hair was assessed according to Tanner and Marshall staging. Genital puberty stage was defined by measurement of testicular volume with Prader orchidometer. Relationship of penile length to age, residence, pubertal stages and body mass index was evaluated statistically. A total of 1,539 boys were included in the study. Mean ages and number of patients according to genital stage were as follows. Mean age was 14 years for genital stage 1 (5 patients), 13.9 years (range 13 to 15) for stage 2 (194), 14.07 years (13 to 15) for stage 3 (965) and 14.11 years (13 to 15) for stage 4 (375). Linear regression analysis revealed a significant effect of body mass index, genital stage and pubic hair stage on penile length (p <0.001) but no significant effect of age or residence. Mean penile length was significantly different among different age groups and among pubertal stages. However, mean penile lengths of different age groups within the same pubertal stage were similar. Penile length during puberty should be evaluated individually according to the current pubertal stage. Our study offers a reliable reference table of penile length for pubertal age group. Copyright © 2012 American Urological Association Education and Research, Inc. Published by Elsevier Inc. All rights reserved.

Minimally Invasive Surgical Staging for Ovarian Carcinoma: A Propensity-Matched Comparison With Traditional Open Surgery.

PubMed

Ditto, Antonino; Bogani, Giorgio; Martinelli, Fabio; Signorelli, Mauro; Chiappa, Valentina; Scaffa, Cono; Indini, Alice; Leone Roberti Maggiore, Umberto; Lorusso, Domenica; Raspagliesi, Francesco

2017-01-01

Growing evidence supports the safety of a laparoscopic approach for patients affected by apparent early-stage ovarian cancer. However, no well-designed studies comparing laparoscopic and open surgical staging are available. In the present investigation we aimed to provide a balanced long-term comparison between these 2 approaches. Retrospective study (Canadian Task Force classification II-2). Tertiary center. Data of consecutive patients affected by early-stage ovarian cancer who had laparoscopic staging were matched 1:1 with a cohort of patients undergoing open surgical staging. The matching was conducted by a propensity-score comparison. Laparoscopic and open surgical staging. Fifty patient pairs (100 patients: 50 undergoing laparoscopic staging vs 50 undergoing open surgical staging) were included. Demographic and baseline oncologic characteristics were balanced between groups (p > .2). We observed that patients undergoing laparoscopic staging experienced longer operative time (207.2 [71.6] minutes vs 180.7 [47.0] minutes; p = .04), lower blood loss (150 [52.7] mL vs 339.8 [225.9] mL; p < .001), and shorter length of hospital stay (4.0 [2.6] days vs 6.1 [1.6] days; p < .001) compared with patients undergoing open surgical staging. No conversion to open surgery occurred. Complication rate was similar between groups. No difference in survival outcomes were observed, after a mean (SD) follow-up of 49.5 (64) and 52.6 (31.7) months after laparoscopic and open surgical staging, respectively. Our findings suggest that the implementation of minimally invasive staging does not influence survival outcomes of patients affected by early-stage ovarian cancer. Laparoscopic staging improved patient outcomes, reducing length of hospital stay. Further large prospective studies are warranted. Copyright © 2016 AAGL. Published by Elsevier Inc. All rights reserved.

Phase I Study of IMRT and Molecular-Image Guided Adaptive Radiation Therapy for Advanced HNSCC

ClinicalTrials.gov

2016-10-27

Salivary Gland Squamous Cell Carcinoma; Stage II Salivary Gland Cancer; Stage II Squamous Cell Carcinoma of the Hypopharynx; Stage II Squamous Cell Carcinoma of the Lip and Oral Cavity; Stage II Squamous Cell Carcinoma of the Oropharynx; Stage II Verrucous Carcinoma of the Oral Cavity; Stage III Salivary Gland Cancer; Stage III Squamous Cell Carcinoma of the Hypopharynx; Stage III Squamous Cell Carcinoma of the Lip and Oral Cavity; Stage III Squamous Cell Carcinoma of the Oropharynx; Stage III Verrucous Carcinoma of the Oral Cavity; Stage IV Salivary Gland Cancer; Stage IV Squamous Cell Carcinoma of the Hypopharynx; Stage IV Squamous Cell Carcinoma of the Lip and Oral Cavity; Stage IV Squamous Cell Carcinoma of the Oropharynx; Stage IV Verrucous Carcinoma of the Oral Cavity

Stage III nasopharyngeal angiofibroma: Improving results with endoscopic-assisted midfacial degloving and modification to the Fisch staging system.

PubMed

Shah, Saurin R; Keshri, Amit; Patadia, Simple; Sahu, Rabi Narayan; Srivastava, Arun Kumar; Behari, Sanjay

2015-10-01

To study outcomes with endoscopic-assisted midfacial degloving for Fisch stage III nasopharyngeal angiofibroma and propose a new staging system. Retrospective study of patients with Fisch stage III juvenile nasopharyngeal angiofibroma (JNA) including preoperative angiography, intraoperative blood loss and residue/recurrence following surgery. Tertiary care superspecialty referral center. Fifteen consecutive patients with Fisch stage III JNA undergoing operations over a period of 18 months. Preoperative angiography details, intraoperative blood loss, residue/recurrence, complications of surgery. Transarterial embolization with particulate agents followed by endoscopic-assisted midfacial degloving provides excellent outcomes with Fisch stage III JNAs. The modified Fisch staging system proposed would allow better preoperative evaluation and comparison of outcomes with different treatment options for stage III JNAs. Copyright © 2015 European Association for Cranio-Maxillo-Facial Surgery. Published by Elsevier Ltd. All rights reserved.

Overview of the Beta II Two-Stage-To-Orbit vehicle design

NASA Technical Reports Server (NTRS)

Plencner, Robert M.

1991-01-01

A study of a near-term, low risk two-stage-to-orbit (TSTO) vehicle was undertaken. The goal of the study was to assess a fully reusable TSTO vehicle with horizontal takeoff and landing capability that could deliver 10,000 pounds to a 120 nm polar orbit. The configuration analysis was based on the Beta vehicle design. A cooperative study was performed to redesign and refine the Beta concept to meet the mission requirements. The vehicle resulting from this study was named Beta II. It has an all-airbreathing first stage and a staging Mach number of 6.5. The second stage is a conventional wing-body configuration with a single SSME.

Is knowledge translation adequate? A quality assurance study of staging investigations in early stage breast cancer patients.

PubMed

Han, Dolly; Hogeveen, Sophie; Sweet Goldstein, Miriam; George, Ralph; Brezden-Masley, Christine; Hoch, Jeffrey; Haq, Rashida; Simmons, Christine E

2012-02-01

After primary surgery, patients diagnosed with early stage breast cancer undergo radiological investigations based on pathologic stage of disease to rule out distant metastases. Published guidelines can aid clinicians in determining which tests are appropriate based on stage of disease. We wished to assess the consistency of radiological staging in an academic community oncology setting with standard guidelines and to determine the overall impact of non-adherence to these guidelines. A retrospective cohort study was conducted for new breast cancer patients seen at a single institution between January 2009 and April 2010. Patients were included if initial diagnosis and primary surgery was at this institution. Pathologic stage and radiological tests completed were recorded. A literature review was performed and the results were compared with those from this study to determine overall adherence rates. Subsequently, a cost analysis was performed to determine the financial impact at this centre. 231 patients met eligibility criteria for inclusion in this study. A large proportion of patients were over-staged with 129 patients (55%) undergoing unnecessary investigations according to guidelines. Specifically, 59% of stage I patients and 58% of stage II patients were over-investigated. Distant metastases at the time of diagnosis were found in three patients, all of whom had stage III disease (1.3%). The literature reviewed revealed similar non-adherence rates in other centres. The estimated cost of such non-adherence is in the range of $78 (CDN) per new early stage breast cancer patient seen at this centre. This oncology centre has a low adherence to practice guidelines for staging investigations in breast cancer patients, with 55% of patients undergoing unnecessary tests. Very few patients had metastases at diagnosis, and all had pathological stage III disease. Efforts may need to focus on improving knowledge translation across clinical oncology settings to increase guideline adherence.

Whole-body MRI versus 18F-FDG PET/CT for pretherapeutic assessment and staging of lymphoma: a meta-analysis.

PubMed

Wang, Danyang; Huo, Yanlei; Chen, Suyun; Wang, Hui; Ding, Yingli; Zhu, Xiaochun; Ma, Chao

2018-01-01

18 F-fluorodeoxyglucose ( 18 F-FDG) positron emission tomography/computed tomography (PET/CT) is the reference standard in staging of 18 F-FDG-avid lymphomas; however, there is no recommended functional imaging modality for indolent lymphomas. Therefore, we aimed to compare the performance of whole-body magnetic resonance imaging (WB-MRI) with that of 18 F-FDG PET/CT for lesion detection and initial staging in patients with aggressive or indolent lymphoma. We searched the MEDLINE, EMBASE, and CENTRAL databases for studies that compared WB-MRI with 18 F-FDG PET/CT for lymphoma staging or lesion detection. The methodological quality of the studies was assessed using version 2 of the "Quality Assessment of Diagnostic Accuracy Studies" tool. The pooled staging accuracy ( μ ) of WB-MRI and 18 F-FDG PET/CT for initial staging and for assessing possible heterogeneity ( χ 2 ) across studies were calculated using commercially available software. Eight studies comprising 338 patients were included. In terms of staging, the meta-analytic staging accuracies of WB-MRI and 18 F-FDG PET/CT for Hodgkin lymphoma and aggressive non-Hodgkin lymphoma (NHL) were 98% (95% CI, 94%-100%) and 98% (95% CI, 94%-100%), respectively. The pooled staging accuracy of 18 F-FDG PET/CT dropped to 87% (95% CI, 72%-97%) for staging in patients with indolent lymphoma, whereas that of WB-MRI remained 96% (95% CI, 91%-100%). Subgroup analysis indicated an even lower staging accuracy of 18 F-FDG PET/CT for staging of less FDG-avid indolent NHLs (60%; 95% CI, 23%-92%), in contrast to the superior performance of WB-MRI (98%; 95% CI, 88%-100%). WB-MRI is a promising radiation-free imaging technique that may serve as a viable alternative to 18 F-FDG PET/CT for staging of 18 FDG-avid lymphomas, where 18 F-FDG PET/CT remains the standard of care. Additionally, WB-MRI seems a less histology-dependent functional imaging test than 18 F-FDG PET/CT and may be the imaging test of choice for staging of indolent NHLs with low 18 F-FDG avidity.

A new system for assessment of growth using mandibular canine calcification stages and its correlation with modified MP3 stages.

PubMed

Hegde, Gautham; Hegde, Nanditha; Kumar, Anil; Keshavaraj

2014-07-01

Orthodontic diagnosis and treatment planning for growing children must involve growth prediction, especially in the treatment of skeletal problems. Studies have shown that a strong association exists between skeletal maturity and dental calcification stages. The present study was therefore taken up to provide a simple and practical method for assessing skeletal maturity using a dental periapical film and standard dental X-ray machine, to compare the developmental stages of the mandibular canine with that of developmental stages of modified MP3 and to find out if any correlation exists, to determine if the developmental stages of the mandibular canine alone can be used as a reliable indicator for assessment of skeletal maturity. A total of 160 periapical radiographs, of the mandibular right canine and the MP3 region was taken and assessed according to the Dermirjian's stages of dental calcification and the modified MP3 stages. The correlation coefficient between MP3 stages and developmental stages of mandibular canine was found to be significant in both male and female groups. When the canine calcification stages were compared with the MP3 stages it was found that with the exception of the D stage of canine calcification the remaining stages showed a very high correlation with the modified MP3 stages. The correlation between the mandibular canine calcification stages, and the MP3 stages was found to be significant. The canine calcification could be used as a sole indicator for assessment of skeletal maturity.

The religiousness as a way of coping with anxiety in women with breast cancer at different disease stages.

PubMed

Janiszewska, Justyna; Buss, Tomasz; de Walden-Gałuszko, Krystyna; Majkowicz, Mikołaj; Lichodziejewska-Niemierko, Monika; Modlińska, Aleksandra

2008-12-01

Anxiety is an unpleasant emotion affecting patients with cancer, and there are various ways of coping with it. Little is known about the relationship between the anxiety level and physical, somatic or spiritual (e.g. religiousness) factors in breast cancer patients at different stages of the disease. The purpose of the study was to assess the intensity of anxiety at different stages of breast cancer, to define the relationship between religiousness and physical (somatic) condition and anxiety in the study subjects and to find out if religiousness is an effective coping strategy at any breast cancer stage. The study involved 180 women aged between 28 and 77, who were qualified to one of five study groups, according to their disease stage. The following research instruments were used: the State-Trait Anxiety Inventory (STAI), Scale of Personal Religiousness, the Rotterdam Symptom Checklist as well as medical history and data from patients' medical records. There is a significant correlation between state anxiety and trait anxiety measured by STAI in study groups. Breast cancer stage differentiates the study groups in respect of revealed anxiety level. Somatic condition has no significant impact on the intensity of anxiety in terminal breast cancer patients. Amongst the studied variables, only religiousness is an important factor that influences the anxiety level of end-stage cancer patients. The obtained results allow us to conclude that: (a) religiousness is an effective factor of coping with anxiety only of the end-stage breast cancer patients; (b) cancer stage is a differentiating factor in respect of revealed anxiety level in study subjects; (c) exacerbation of somatic symptoms does not influence the anxiety level in terminal cancer patients and at disease-free period.

A two-stage design for multiple testing in large-scale association studies.

PubMed

Wen, Shu-Hui; Tzeng, Jung-Ying; Kao, Jau-Tsuen; Hsiao, Chuhsing Kate

2006-01-01

Modern association studies often involve a large number of markers and hence may encounter the problem of testing multiple hypotheses. Traditional procedures are usually over-conservative and with low power to detect mild genetic effects. From the design perspective, we propose a two-stage selection procedure to address this concern. Our main principle is to reduce the total number of tests by removing clearly unassociated markers in the first-stage test. Next, conditional on the findings of the first stage, which uses a less stringent nominal level, a more conservative test is conducted in the second stage using the augmented data and the data from the first stage. Previous studies have suggested using independent samples to avoid inflated errors. However, we found that, after accounting for the dependence between these two samples, the true discovery rate increases substantially. In addition, the cost of genotyping can be greatly reduced via this approach. Results from a study of hypertriglyceridemia and simulations suggest the two-stage method has a higher overall true positive rate (TPR) with a controlled overall false positive rate (FPR) when compared with single-stage approaches. We also report the analytical form of its overall FPR, which may be useful in guiding study design to achieve a high TPR while retaining the desired FPR.

Changes in blood flow during one stage lengthening of bone: an experimental study in rats.

PubMed

Kwon, S T; Chung, C Y

2000-06-01

Distraction osteogenesis is a well-accepted method of bone lengthening. Its disadvantages, however, are that it requires an external fixator and takes a long time. One-stage lengthening therefore offers certain advantages. A first point of reference for the safe limits of this procedure might be the changes of blood flow, and this is also the crucial factor in deciding on the appropriate method of lengthening, particularly where the hand or foot is involved. Using a laser Doppler flowmeter we measured blood flow in the dorsum of the foot after using bilateral minimonofixators to lengthen the tibias of 15 Sprague-Dawley rats. They were lengthened in four stages: stage 0 (before lengthening); stage I--12.5%; stage II--25%; and stage III--31.25% of lengthening. The blood flow during stage I decreased to 79% compared to that of stage 0; 16% during stage II; and 1% during stage III. This study suggests that the maximal permissible extent of lengthening might be less than a quarter according to the blood flow as suggested by this animal model.

A Multi-Stage Longitudinal Comparative Design Stage II Evaluation of the Changing Lives Program: The Life Course Interview (RDA-LCI)

ERIC Educational Resources Information Center

Arango, Lisa Lewis; Kurtines, William M.; Montgomery, Marilyn J.; Ritchie, Rachel

2008-01-01

The study reported in this article, a Multi-Stage Longitudinal Comparative Design Stage II evaluation conducted as a planned preliminary efficacy evaluation (psychometric evaluation of measures, short-term controlled outcome studies, etc.) of the Changing Lives Program (CLP), provided evidence for the reliability and validity of the qualitative…

Implementing WebQuest Based Instruction on Newton's Second Law

ERIC Educational Resources Information Center

Gokalp, Muhammed Sait; Sharma, Manjula; Johnston, Ian; Sharma, Mia

2013-01-01

The purpose of this study was to investigate how WebQuests can be used in physics classes for teaching specific concepts. The study had three stages. The first stage was to develop a WebQuest on Newton's second law. The second stage involved developing a lesson plan to implement the WebQuest in class. In the final stage, the WebQuest was…

Comparison of Individual Criteria and Externally Imposed Criteria for Stage Allocation: Findings from an Internet Study Addressing Physical Activity

ERIC Educational Resources Information Center

Richert, Jana; Lippke, Sonia; Schwarzer, Ralf

2010-01-01

Stage-matched interventions can only be more effective than "one-size-fits-all" interventions if they target participants' specific needs. Therefore, individuals must be allocated to a stage that truly reflects their mindsets. Various criteria for stage allocation exist. This study's objective was to demonstrate the impact of different…

Exemplar Units of Work for English. Key Stage 3: National Strategy.

ERIC Educational Resources Information Center

Department for Education and Skills, London (England).

These exemplar units of work for National Strategy Key Stage 3 English show how medium and short-term planning can be based on the Key Stage 3 Framework objectives and support the implementation of Curriculum 2000. The Key Stage 3 English strand introduces pupils to more specialist study of language and literature and supports the study of…

Two-stage unilateral versus one-stage bilateral single-port sympathectomy for palmar and axillary hyperhidrosis†

PubMed Central

Ibrahim, Mohsen; Menna, Cecilia; Andreetti, Claudio; Ciccone, Anna Maria; D'Andrilli, Antonio; Maurizi, Giulio; Poggi, Camilla; Vanni, Camilla; Venuta, Federico; Rendina, Erino Angelo

2013-01-01

OBJECTIVES Video-assisted thoracoscopic sympathectomy is currently the best treatment for palmar and axillary hyperhidrosis. It can be performed through either one or two stages of surgery. This study aimed to evaluate the operative and postoperative results of two-stage unilateral vs one-stage bilateral thoracoscopic sympathectomy. METHODS From November 1995 to February 2011, 270 patients with severe palmar and/or axillary hyperhidrosis were recruited for this study. One hundred and thirty patients received one-stage bilateral, single-port video-assisted thoracoscopic sympathectomy (one-stage group) and 140, two-stage unilateral, single-port video-assisted thoracoscopic sympathectomy, with a mean time interval of 4 months between the procedures (two-stage group). RESULTS The mean postoperative follow-up period was 12.5 (range: 1–24 months). After surgery, hands and axillae of all patients were dry and warm. Sixteen (12%) patients of the one-stage group and 15 (11%) of the two-stage group suffered from mild/moderate pain (P = 0.8482). The mean operative time was 38 ± 5 min in the one-stage group and 39 ± 8 min in the two-stage group (P = 0.199). Pneumothorax occurred in 8 (6%) patients of the one-stage group and in 11 (8%) of the two-stage group. Compensatory sweating occurred in 25 (19%) patients of the one-stage group and in 6 (4%) of the two-stage group (P = 0.0001). No patients developed Horner's syndrome. CONCLUSIONS Both two-stage unilateral and one-stage bilateral single-port video-assisted thoracoscopic sympathectomies are effective, safe and minimally invasive procedures. Two-stage unilateral sympathectomy can be performed with a lower occurrence of compensatory sweating, improving permanently the quality of life in patients with palmar and axillary hyperhidrosis. PMID:23442937

Two-stage unilateral versus one-stage bilateral single-port sympathectomy for palmar and axillary hyperhidrosis.

PubMed

Ibrahim, Mohsen; Menna, Cecilia; Andreetti, Claudio; Ciccone, Anna Maria; D'Andrilli, Antonio; Maurizi, Giulio; Poggi, Camilla; Vanni, Camilla; Venuta, Federico; Rendina, Erino Angelo

2013-06-01

Video-assisted thoracoscopic sympathectomy is currently the best treatment for palmar and axillary hyperhidrosis. It can be performed through either one or two stages of surgery. This study aimed to evaluate the operative and postoperative results of two-stage unilateral vs one-stage bilateral thoracoscopic sympathectomy. From November 1995 to February 2011, 270 patients with severe palmar and/or axillary hyperhidrosis were recruited for this study. One hundred and thirty patients received one-stage bilateral, single-port video-assisted thoracoscopic sympathectomy (one-stage group) and 140, two-stage unilateral, single-port video-assisted thoracoscopic sympathectomy, with a mean time interval of 4 months between the procedures (two-stage group). The mean postoperative follow-up period was 12.5 (range: 1-24 months). After surgery, hands and axillae of all patients were dry and warm. Sixteen (12%) patients of the one-stage group and 15 (11%) of the two-stage group suffered from mild/moderate pain (P = 0.8482). The mean operative time was 38 ± 5 min in the one-stage group and 39 ± 8 min in the two-stage group (P = 0.199). Pneumothorax occurred in 8 (6%) patients of the one-stage group and in 11 (8%) of the two-stage group. Compensatory sweating occurred in 25 (19%) patients of the one-stage group and in 6 (4%) of the two-stage group (P = 0.0001). No patients developed Horner's syndrome. Both two-stage unilateral and one-stage bilateral single-port video-assisted thoracoscopic sympathectomies are effective, safe and minimally invasive procedures. Two-stage unilateral sympathectomy can be performed with a lower occurrence of compensatory sweating, improving permanently the quality of life in patients with palmar and axillary hyperhidrosis.

Phase II Study of Everolimus Beyond Progression

ClinicalTrials.gov

2017-09-29

Estrogen Receptor-positive Breast Cancer; HER2-negative Breast Cancer; Progesterone Receptor-positive Breast Cancer; Recurrent Breast Cancer; Stage IIIA Breast Cancer; Stage IIIB Breast Cancer; Stage IIIC Breast Cancer; Stage IV Breast Cancer

Effect of hydronephrosis on survival in advanced stage cervical cancer.

PubMed

Goklu, Mehmet Rıfat; Seckin, Kerem Doga; Togrul, Cihan; Goklu, Yasemin; Tahaoglu, Ali Emre; Oz, Murat; Ertas, Ibrahim Egemen

2015-01-01

Hydronephrosis is frequently encountered in advanced stage cervical cancers, and may be associated with mortality. In the present study, we aimed to demonstrate the effect of hydronephrosis on survival in patients with inoperable advanced stage cervical cancer. The study data were acquired by retrospective analysis of the patient records belonging to 165 women with FIGO (International Federation of Gynecology and Obstetrics) stage-IIIB or more advanced cervical cancer, which were not surgical candidates. Parameters including patient age, pathological diagnosis, disease stage, pelvic sidewall extension, presence of hydronephrosis and administration of chemoradiation were analyzed. Further, the effects of these variables on survival were assessed. P values less than 0.05 were considered statistically significant. The distribution of the study patients according to disease stage was as follows: 131 (79.4%) had stage-IIIB, 18 (10.9%) had stage-IVB and 16 (% 9.7) patients had stage-IVA disease. Hydronephrosis was not evident in 91 (55.2%) of these patients, whereas 41 (24.8%) had unilateral and 33 (20%) patients had bilateral hydronephrosis. When compared to mean survival in patients who did not have hydronephrosis, survival was significantly shortened in patients who had bilateral and unilateral hydronephrosis (p<0.05). There was no significant survival difference between patients with unilateral and bilateral hydronephrosis (p>0.05). Although patient age, pathological type, pelvic involvement, and chemotherapy treatment rates were similar (p>0.05), radiotherapy requirement rate and disease stage were significantly different among the study groups (p<0.05). Hydronephrosis was found to be a significant predictor of poor survival in patients with advanced stage cervical cancer, irrespective of unilateral or bilateral involvement.While waiting for future studies with larger sample sizes, we believe that the FIGO stages in advanced cervical cancer could further be stratified into subgroups according to presence or absence of hydronephrosis.

Prevalence of age-related macular degeneration in a large European cohort: results from the population-based Gutenberg Health Study.

PubMed

Korb, Christina A; Kottler, Ulrike B; Wolfram, Christian; Hoehn, René; Schulz, Andreas; Zwiener, Isabella; Wild, Philipp S; Pfeiffer, Norbert; Mirshahi, Alireza

2014-09-01

The aim of this study was to describe the sex- and age-specific prevalence of age-related macular degeneration (AMD) and its correlation with urban or rural residence in a large and relatively young European cohort. We evaluated fundus photographs from participants in the Gutenberg Health Study (GHS), a population-based, prospective, observational, single-centre study in the Rhineland-Palatine region in midwestern Germany. The participants were 35-74 years of age at enrolment. The fundus images were classified as described in the Rotterdam Study and were graded independently by two experienced ophthalmologists (CK and UBK) based on the presence of hard and soft drusen, retinal pigmentary abnormalities, and signs of atrophic or neovascular age-related macular generation (AMD). Photographs from 4,340 participants were available for grading. Small, hard drusen (<63 μm, stages 0b and 0c) were present in 37.4% of participants (95% confidence interval [CI], stage 0b, 31.6% [30.3-33.7]; stage 0c, 5.8% [5.1-6.5]). Early AMD (soft drusen, pigmentary abnormalities, stages 1-3) was present in 3.8% of individuals in the youngest age group (35-44 years) (95% CI, stage 1a, 0.4% [0.3-0.5%]; stage 1b, 3.2% [2.9-3.5%]; stage 2a, 0.1% [0.1-0.2%]; stage 2b, 0% [0-0.0%]; stage 3, 0.1% [0.1-0.2%]), whereas late AMD (stages 4a and 4b) did not appear in the youngest age group. In all age groups, signs of early AMD were detected in 11.9% of individuals (stage 1a, 2.1% [1.7-2.6]; stage 1b, 8.0% [7.2-8.8]; stage 2a, 1.0% [0.7-1.3]; stage 2b, 0.5% [0.3-0.7]; stage 3, 0.3% [0.2-0.6]). Late AMD (geographic atrophy or neovascular AMD) was found in 0.2% of individuals (stage 4a, 0.1 % [0.0-0.2]; stage 4b, 0.1% [0.0-0.2]). AMD increased significantly with age (odds ratio [OR], 1.09; 95% CI, 1.08-1.10). Sex, iris colour, and residence (rural vs. urban) were not associated with different rates of AMD. In this study, the prevalence of AMD increased dramatically with age; however, although AMD is usually thought to occur after age 50, signs of early AMD were found in 3.8% of individuals in the youngest age group (younger than 45 years). This population-based sample is the first to provide substantial epidemiologic data from a large German cohort, including data on macular degeneration in younger age groups and incidence data after recall.

Experimental Study of Thermal Field Evolution in the Short-Impending Stage Before Earthquakes

NASA Astrophysics Data System (ADS)

Ren, Yaqiong; Ma, Jin; Liu, Peixun; Chen, Shunyun

2017-08-01

Phenomena at critical points are vital for identifying the short-impending stage prior to earthquakes. The peak stress is a critical point when stress is converted from predominantly accumulation to predominantly release. We call the duration between the peak stress and instability "the meta-instability stage", which refers to the short-impending stage of earthquakes. The meta-instability stage consists of a steady releasing quasi-static stage and an accelerated releasing quasi-dynamic stage. The turning point of the above two stages is the remaining critical point. To identify the two critical points in the field, it is necessary to study the characteristic phenomena of various physical fields in the meta-instability stage in the laboratory, and the strain and displacement variations were studied. Considering that stress and relative displacement can be detected by thermal variations and peculiarities in the full-field observations, we employed a cooled thermal infrared imaging system to record thermal variations in the meta-instability stage of stick slip events generated along a simulated, precut planer strike slip fault in a granodiorite block on a horizontally bilateral servo-controlled press machine. The experimental results demonstrate the following: (1) a large area of decreasing temperatures in wall rocks and increasing temperatures in sporadic sections of the fault indicate entrance into the meta-instability stage. (2) The rapid expansion of regions of increasing temperatures on the fault and the enhancement of temperature increase amplitude correspond to the turning point from the quasi-static stage to the quasi-dynamic stage. Our results reveal thermal indicators for the critical points prior to earthquakes that provide clues for identifying the short-impending stage of earthquakes.

Continuous monitoring of seasonal phenological development by BBCH code

NASA Astrophysics Data System (ADS)

Cornelius, Christine; Estrella, Nicole; Menzel, Annette

2010-05-01

Phenology, the science of recurrent seasonal natural events, is a proxy for changes in ecosystems due to recent global climate change. Phenological studies mostly deal with data considering the beginning of different development stages e.g. budburst or the beginning of flowering. Just few studies focus on the end of phenological stages, such as the end of flowering or seed dispersal. Information about the entire development cycle of plants, including data of the end of stages, are received by observing plants according to the extended BBCH-scale (MEIER 1997). The scale is a standardized growth stage key which allows a less labor intensive, weekly observation rhythm. Every week frequencies of all occurring phenological stages are noted. These frequencies then constitute the basis to interpolate the development of each phenological stage, even though it was not being seen during field work. Due to the lack of studies using this kind of key for observations over the entire development cycle there is no common methodology to analyze the data. So our objective was to find a method of analysis, with which onset dates as well as endpoints of each development stage could be defined. Three different methods of analysis were compared. Results show that there is no significant difference in onset dates of phenological stages between all methods tested. However, the method of pooled pre/post stage development seems to be most suitable for climate change studies, followed by the method of cumulative stage development and the method of weighted plant development.

A prospective cohort study of acute kidney injury in multi-stage ultramarathon runners: the Biochemistry in Endurance Runner Study (BIERS).

PubMed

Lipman, Grant S; Krabak, Brian J; Waite, Brandee L; Logan, Sarah B; Menon, Anil; Chan, Garrett K

2014-01-01

The purpose of the study was to evaluate the prevalence of acute kidney injury (AKI) during a multi-stage ultramarathon foot race. A prospective observational study was taken during the Gobi 2008; Sahara 2008; and Namibia 2009 RacingThePlanet 7-day, 6-stage, 150-mile foot ultramarathons. Blood was analyzed before, and immediately after stage 1 (25 miles), 3 (75 miles), and 5 (140 miles). Creatinine (Cr), glomerular filtration rate (GFR), and incidence of AKI were calculated and defined by RIFLE criteria. Thirty participants (76% male, mean age 40 + 11 years) were enrolled. There were significant declines in GFR after each stage compared with the pre-race baseline (p < 0.001), with the majority of participants (55-80%) incurring AKI. The majority of study participants encountered significant renal impairment; however, no apparent cumulative effect was observed, with resolution of renal function to near baseline levels between stages.

Error reduction and representation in stages (ERRIS) in hydrological modelling for ensemble streamflow forecasting

NASA Astrophysics Data System (ADS)

Li, Ming; Wang, Q. J.; Bennett, James C.; Robertson, David E.

2016-09-01

This study develops a new error modelling method for ensemble short-term and real-time streamflow forecasting, called error reduction and representation in stages (ERRIS). The novelty of ERRIS is that it does not rely on a single complex error model but runs a sequence of simple error models through four stages. At each stage, an error model attempts to incrementally improve over the previous stage. Stage 1 establishes parameters of a hydrological model and parameters of a transformation function for data normalization, Stage 2 applies a bias correction, Stage 3 applies autoregressive (AR) updating, and Stage 4 applies a Gaussian mixture distribution to represent model residuals. In a case study, we apply ERRIS for one-step-ahead forecasting at a range of catchments. The forecasts at the end of Stage 4 are shown to be much more accurate than at Stage 1 and to be highly reliable in representing forecast uncertainty. Specifically, the forecasts become more accurate by applying the AR updating at Stage 3, and more reliable in uncertainty spread by using a mixture of two Gaussian distributions to represent the residuals at Stage 4. ERRIS can be applied to any existing calibrated hydrological models, including those calibrated to deterministic (e.g. least-squares) objectives.

An Evaluation of One- and Three-Parameter Logistic Tailored Testing Procedures for Use with Small Item Pools.

ERIC Educational Resources Information Center

McKinley, Robert L.; Reckase, Mark D.

A two-stage study was conducted to compare the ability estimates yielded by tailored testing procedures based on the one-parameter logistic (1PL) and three-parameter logistic (3PL) models. The first stage of the study employed real data, while the second stage employed simulated data. In the first stage, response data for 3,000 examinees were…

[Cervical vertebrae: Mandibular growth dynamism indicators?].

PubMed

Raberin, Monique; Cozor, Ilinca; Gobert-Jacquart, Stéphanie

2012-03-01

A study of mandibular growth maturation was performed on a population of 103 patients during orthodontic treatment (69 girls and 34 boys) from 11 to 16 years, having initially a Class II skeletal discrepancy. The relationship between wrist maturation indices and the cervical vertebrae maturation was studied by Lamparski classification. Significant correlations were found between Björk stages, MP3=, MP3 cap and MP3 U and respectively Lamparski stages as CVS 2, CVS 3-4 and CVS 5-6. This retrospective longitudinal study identified three mandibular variables at three different maturation stages according to Björk classification and to the six stages of Lamparski classification. The relationships between these different maturation stages and a quantitative mandibular response permit to estimate optimal time for our orthodontic therapy. The results indicate a significant increase in mandibular length between CVS 4 and CVS 5, suggesting the persistence of a condylar response to a stimulation therapy after CVS3 or CVS 4 stages (MP3 cap). Mandibular growth seems to continue after MP3 U stage or CVS 5 stage. © EDP Sciences, SFODF, 2012.

Developing Statistical Physics Course Handout on Distribution Function Materials Based on Science, Technology, Engineering, and Mathematics

NASA Astrophysics Data System (ADS)

Riandry, M. A.; Ismet, I.; Akhsan, H.

2017-09-01

This study aims to produce a valid and practical statistical physics course handout on distribution function materials based on STEM. Rowntree development model is used to produce this handout. The model consists of three stages: planning, development and evaluation stages. In this study, the evaluation stage used Tessmer formative evaluation. It consists of 5 stages: self-evaluation, expert review, one-to-one evaluation, small group evaluation and field test stages. However, the handout is limited to be tested on validity and practicality aspects, so the field test stage is not implemented. The data collection technique used walkthroughs and questionnaires. Subjects of this study are students of 6th and 8th semester of academic year 2016/2017 Physics Education Study Program of Sriwijaya University. The average result of expert review is 87.31% (very valid category). One-to-one evaluation obtained the average result is 89.42%. The result of small group evaluation is 85.92%. From one-to-one and small group evaluation stages, averagestudent response to this handout is 87,67% (very practical category). Based on the results of the study, it can be concluded that the handout is valid and practical.

A new system for assessment of growth using mandibular canine calcification stages and its correlation with modified MP3 stages

PubMed Central

Hegde, Gautham; Hegde, Nanditha; Kumar, Anil; Keshavaraj

2014-01-01

Objective: Orthodontic diagnosis and treatment planning for growing children must involve growth prediction, especially in the treatment of skeletal problems. Studies have shown that a strong association exists between skeletal maturity and dental calcification stages. The present study was therefore taken up to provide a simple and practical method for assessing skeletal maturity using a dental periapical film and standard dental X-ray machine, to compare the developmental stages of the mandibular canine with that of developmental stages of modified MP3 and to find out if any correlation exists, to determine if the developmental stages of the mandibular canine alone can be used as a reliable indicator for assessment of skeletal maturity. Materials and Methods: A total of 160 periapical radiographs, of the mandibular right canine and the MP3 region was taken and assessed according to the Dermirjian's stages of dental calcification and the modified MP3 stages. Results and Discussion: The correlation coefficient between MP3 stages and developmental stages of mandibular canine was found to be significant in both male and female groups. When the canine calcification stages were compared with the MP3 stages it was found that with the exception of the D stage of canine calcification the remaining stages showed a very high correlation with the modified MP3 stages. Conclusion: The correlation between the mandibular canine calcification stages, and the MP3 stages was found to be significant. The canine calcification could be used as a sole indicator for assessment of skeletal maturity. PMID:25210386

Application of magnetic resonance imaging in diagnosis of Uterus Cervical Carcinoma.

PubMed

Peng, Jidong; Wang, Weiqiang; Zeng, Daohui

2017-01-01

Effective treatment of Uterus Cervical Carcinoma (UCC) rely heavily on the precise pre-surgical staging. The conventional International Federation of Gynecology and Obstetrics (FIGO) system based on clinical examination is being applied worldwide for UCC staging. Yet its performance just appears passable. Thus, this study aims to investigate the value of applying Magnetic Resonance Imaging (MRI) with clinical examination in staging of UCC. A retrospective dataset involving 164 patients diagnosed with UCC was enrolled in this study. The mean age of this study population was 46.1 years (range, 28-#x2013;75 years). All patients underwent operations and UCC types were confirmed by pathological examinations. The tumor stages were determined by two experienced Gynecologist independently based on FIGO examinations and MRI. The diagnostic results were also compared with the post-operative pathologic reports. Statistical data analysis on diagnostic performance was then done and reported. The study results showed that the overall accuracy of applying MRI in UCC staging was 82.32%, while using FIGO staging method, the staging accuracy was 59.15%. MRI is suitable to evaluate tumor extent with high accuracy, and it can offer more objective information for the diagnosis and staging of UCC. Compared with clinical examinations based on FIGO, MRI illustrated relatively high accuracy in evaluating UCC staging, and is worthwhile to be recommended in future clinical practice.

Postoperative radiotherapy and tumor recurrence after complete resection of stage II/III thymic tumor: a meta-analysis of cohort studies.

PubMed

Ma, Jietao; Sun, Xin; Huang, Letian; Xiong, Zhicheng; Yuan, Meng; Zhang, Shuling; Han, Cheng-Bo

2016-01-01

Whether postoperative radiotherapy (PORT) is effective for reducing the recurrence risk in patients who received complete resection of the stage II or III thymic tumors has not been determined. A meta-analysis was performed by combining the results of all available controlled trials. PubMed, Cochrane's Library, and the Embase databases were searched for studies which compared the recurrence data for patients with complete resection of the stage II or III thymic tumors assigned to an observing group, or a PORT group. A random effect model was applied to combine the results. Nineteen studies, all designed as retrospective cohort studies were included. These studies included 663 patients of PORT group and 617 patients of observing group. The recurrence rate for the patients in PORT group and observing group were 12.4% and 11.5%, respectively. Results of our study indicated that PORT has no significant influence on recurrent risk in patients with stage II or III thymic tumor after complete resection (odds ratio 1.02, 95% confidence interval 0.55-1.90, P=0.96). When stratified by stages, our meta-analyses did not indicate any significant effects of PORT on recurrent outcomes in either the stage II or the stage III patients. Moreover, subsequent analysis limited to studies only including patients with thymoma or thymic carcinoma also did not support the benefits of PORT on recurrent outcomes. Although derived from retrospective cohort studies, current evidence did not support any benefit of PORT on recurrent risk in patients with complete resection of the stage II or III thymic tumors.

Disease staging as a measure of disease severity.

PubMed

Kohyama, Jun; Fujitani, Shigeki; Umesato, Yoshimasa; Kataoka, Hitomi

2015-06-24

Disease staging, first developed in 1970, has been used to assess the levels of biological severity, defined as the risk of organ failure or death, of specific medical diseases. Because few studies to date have evaluated disease staging in Japan, a small pilot study was designed to determine whether disease staging is available and useful in actual medical practice in Japan. The relationships between disease staging and length of stay, medical costs and age were retrospectively evaluated in patients admitted to Japan Association for Development of Community Medicine - Tokyo Bay Urayasu Ichikawa Medical Center for appendicitis, type 2 diabetes mellitus, and cerebrovascular diseases from April 2012 to March 2013. Patients were easily staged based on information at the time of hospital discharge. Disease stages were found to be affected significantly by length of hospital stay and medical costs. Age also affected disease stages in patients with appendicitis. These findings indicate that disease staging was available in Japan and was affected by hospital resources, including length of hospital stay and medical costs.

Evaluation Study for Secondary Stage EFL Textbook: EFL Teachers' Perspectives

ERIC Educational Resources Information Center

Al Harbi, Abdullah Abdul Muhsen

2017-01-01

This study aimed at evaluating EFL textbook for secondary stage in Saudi Public schools. Participants consisted of (100) male teachers and (73) female teachers teaching secondary stage students in two cities: Madinah and Dowadmi. The tool of the study designed to cover five dimensions: layout and design, the objectives of the textbook, teaching…

Effect of maturity at harvest for whole-crop barley and oat on dry matter intake, sorting, and digestibility when fed to beef cattle.

PubMed

Rosser, C L; Beattie, A D; Block, H C; McKinnon, J J; Lardner, H A; Górka, P; Penner, G B

2016-02-01

The objectives were to evaluate the effect of harvest maturity of whole-crop oat (Study 1) and whole-crop barley (Study 2) on forage intake and sorting, ruminal fermentation, ruminal digestibility, and total tract digestibility when fed to beef heifers. In Study 1, 3 ruminally cannulated heifers (417 ± 5 kg) were used in a 3 × 3 Latin square design with 24-d periods. Whole-crop oat forage harvested at the late milk (LMILK), hard dough (HD), or ripe (RP) stages was fed for ad libitum intake and heifers were supplemented (1% of BW) with alfalfa pellets, barley grain, canola meal, and a mineral and vitamin pellet. Maturity at harvest for whole-crop oat did not affect ( ≥ 0.058) forage intake, DE intake, amount of forage refused, ruminal short-chain fatty acid concentration, or digestibility of DM, OM, NDF, and ADF. Ruminal starch digestibility decreased ( < 0.001) from 92.6% at the LMILK stage to 90.0% at the RP stage, with total tract starch digestibility decreasing ( = 0.043) from 95.8% at the LMILK stage to 94.8% at the RP stage. Ruminal CP digestibility was reduced at the HD stage compared with the LMILK and RP stages ( < 0.001). Mean ruminal pH was greatest for the LMILK stage (6.36; = 0.003) compared with the HD and RP stages (6.30 and 6.28, respectively). In Study 2, 6 ruminally cannulated heifers (273 ± 16 kg) were used in a replicated 3 × 3 Latin square design with 24-d periods. Dietary treatments included ad libitum access to whole-crop barley harvested at the LMILK, HD, or RP stage and a constant rate (0.8% BW) of supplement containing alfalfa pellets, barley grain, canola meal, and a mineral and vitamin pellet. Dry matter intake, ruminal content mass, and feeding behavior were not affected by harvest maturity ( ≥ 0.16). There was a decrease in total tract digestibility of DM, OM, and NDF observed at the HD stage compared with the LMILK and RP stages ( ≤ 0.004). Ruminal NDF digestibility decreased from 69.7% at the LMILK stage to 54.4% at the HD stage and 54.9% at the RP stage ( = 0.001), whereas ruminal ADF digestibility decreased from 70.0% at the LMILK stage to 44.4% at the HD stage and 42.5% at the RP stage ( = 0.002). Minimum and mean ruminal pH were least for the LMILK stage, intermediate at the RP stage, and greatest at the HD stage ( = 0.016 and = 0.031, respectively). These data suggest that despite reductions in ruminal digestibility of NDF and ADF with advancing maturity, harvesting whole-crop oat and barley forage at the HD and RP stages of maturity did not negatively affect DMI, fermentation characteristics, or DE relative to whole-crop cereal forage harvested at the LMILK stage.

A stage-normalized function for the synthesis of stage-discharge relations for the Colorado River in Grand Canyon, Arizona

USGS Publications Warehouse

Wiele, Stephen M.; Torizzo, Margaret

2003-01-01

A method was developed to construct stage-discharge rating curves for the Colorado River in Grand Canyon, Arizona, using two stage-discharge pairs and a stage-normalized rating curve. Stage-discharge rating curves formulated with the stage-normalized curve method are compared to (1) stage-discharge rating curves for six temporary stage gages and two streamflow-gaging stations developed by combining stage records with modeled unsteady flow; (2) stage-discharge rating curves developed from stage records and discharge measurements at three streamflow-gaging stations; and (3) stages surveyed at known discharges at the Northern Arizona Sand Bar Studies sites. The stage-normalized curve method shows good agreement with field data when the discharges used in the construction of the rating curves are at least 200 cubic meters per second apart. Predictions of stage using the stage-normalized curve method are also compared to predictions of stage from a steady-flow model.

Study of Ponatinib in Patients With Lung Cancer Preselected Using Different Candidate Predictive Biomarkers

ClinicalTrials.gov

2018-01-17

Adenocarcinoma of the Lung; Extensive Stage Small Cell Lung Cancer; Limited Stage Small Cell Lung Cancer; Recurrent Non-small Cell Lung Cancer; Recurrent Small Cell Lung Cancer; Stage IIIA Non-small Cell Lung Cancer; Stage IIIB Non-small Cell Lung Cancer; Stage IV Non-small Cell Lung Cancer

Para-aortic lymphadenectomy in advanced stage cervical cancer, a protocol for comparing safety, feasibility and diagnostic accuracy of surgical staging versus PET-CT; PALDISC trial.

PubMed

Tax, Casper; Abbink, Karin; Rovers, Maroeska M; Bekkers, Ruud L M; Zusterzeel, Petra L M

2018-01-01

Currently, a PET-CT is used to assess the need for extended field radiotherapy of para-aortic lymph nodes (PALN) in International Federation of Gynaecology and Obstetrics (FIGO) stage IB2, IIA2-IVA (locally advanced stage) cervical cancer. A small study established a sensitivity and specificity estimate for PALN metastases of 50% (95% CI; 7-93%) and 83% (95% CI; 52-98%), respectively. Surgical staging of PALN may lead to a higher diagnostic accuracy. However, surgical staging of para-aortic lymph nodes in locally advanced stage cervical cancer is not common practice. Therefore, a phase 2 randomised controlled trial is needed to assess its safety and feasibility. In addition to standard imaging (MRI or CT scan) with PET-CT, 30 adult women with FIGO stage IB2, IIA2-IVA cervical cancer will be randomised to receive either surgical staging or usual PET-CT staging. Administering extended field radiotherapy will be based on lymphadenectomy results for the intervention group and on the PET-CT results for the control group. Follow-up visits at 0, 3, 6, 9 and 12 months will assess health-related quality of life and progression-free survival.Primary safety and feasibility outcomes of surgical staging will be assessed by calculating means with 95% confidence intervals for duration of surgery, number of complications, blood loss, nodal yield after para-aortic lymphadenectomy and treatment delay due to surgical staging. Secondary patient-centred outcomes on quality of life and first year survival will be documented and compared between the two groups. Estimates of sensitivity, specificity and negative and positive predictive values of MRI, PET-CT and surgical staging will be presented with 95% CI.. All analysis will be performed according to the intention to treat principle. This study will assess safety and feasibility, expressed as the number and severity of complications, effect on quality of life and the treatment delay due to surgically staging para-aortic lymph nodes in locally advanced cervical cancer. It will provide insight in the diagnostic accuracy of the PET-CT and detection rate of missed (micro)metastases due to surgical staging. This information will be used to assess the necessity for a phase 3 study on the diagnostic accuracy of the PET-CT and surgical staging. If a phase 3 study is deemed necessary, current data can be used for sample size calculation of such a phase 3 study. Nederlands Trial Register/Dutch Trial Registry (www.trialregister.nl), NTR4922. Registered on 24 November 2014.

[Automation and organization of technological process of urinalysis].

PubMed

Kolenkin, S M; Kishkun, A A; Kol'chenko, O L

2000-12-01

Results of introduction into practice of a working model of industrial technology of laboratory studies and KONE Specific Supra and Miditron M devices are shown as exemplified by clinical analysis of the urine. This technology helps standardize all stages and operations, improves the efficiency of quality control of laboratory studies, rationally organizes the work at all stages of the process, creates a system for permanent improvement of the efficiency of investigations at the preanalytical, analytical, and postanalytical stages of technological process of laboratory studies. As a result of introduction of this technology into laboratory practice, violations of quality criteria of clinical urinalysis decreased from 15 to 8% at the preanalytical stage and from 6 to 3% at the analytical stage. Automation of the analysis decreased the need in reagents 3-fold and improved the productivity at the analytical stage 4-fold.

Improvements in stage of change correlate to changes in dietary intake and clinical outcomes in a 5-year lifestyle intervention in young high-risk Sri Lankans.

PubMed

Guess, N; Vasantharajah, L; Gulliford, M; Viberti, G; Gnudi, L; Karalliedde, J; Wijesuriya, M

2016-09-01

The objectives of a stage-matched approach to lifestyle change are that individuals progress forward through the stages of change. It also posits that progression through the stages of change is associated with positive changes in lifestyle behaviours. Measuring the relationship between stage of change and food intake is challenging due to the plurality of dietary behaviours. Furthermore, it is not clear whether changes in behaviour are sustained long-term. In this study we assess the movement through stages of change in the intensive (visits every 3months) and control groups (visits annually) of a large-scale primary prevention study in cardiovascular disease, carried out in 2637 children and young adults in Sri Lanka between 2007 and 2012. We also examine their relationship to dietary behaviours and clinical outcomes. We demonstrate that individuals in both groups continue to progress through stages of change over the course of the study and that measures of dietary behaviours improved from baseline to final follow-up. We also demonstrate that stage of change positively correlates to dietary behaviours including the ratio of recommended:not-recommended items, unpolished:polished starches and low-fat:high-fat food items throughout each year of the study. Finally, participants in the later stages of change at Y2, Y3 and Y4, had a significantly attenuated increase in weight and waist circumference at the final visit in both groups. We therefore demonstrate the usefulness of stage-matched approach in modifying complex dietary behaviours, and that stage of change is a valid measure of dietary behaviours across a large population over time. Copyright © 2016 Elsevier Inc. All rights reserved.

Socioeconomic position and surgery for early-stage non-small-cell lung cancer: A population-based study in Denmark.

PubMed

Kærgaard Starr, Laila; Osler, Merete; Steding-Jessen, Marianne; Lidegaard Frederiksen, Birgitte; Jakobsen, Erik; Østerlind, Kell; Schüz, Joachim; Johansen, Christoffer; Oksbjerg Dalton, Susanne

2013-03-01

To examine possible associations between socioeconomic position and surgical treatment of patients with early-stage non-small-cell lung cancer (NSCLC). In a register-based clinical cohort study, patients with early-stage (stages I-IIIa) NSCLC were identified in the Danish Lung Cancer Register 2001-2008 (date of diagnosis, histology, stage, and treatment), the Central Population Register (vital status), the Integrated Database for Labour Market Research (socioeconomic position), and the Danish Hospital Discharge Register (comorbidity). Logistic regression analyses were performed overall and separately for stages I, II and IIIa. Of the 5538 eligible patients with stages I-IIIa NSCLC diagnosed 2001-2008, 53% underwent surgery. Higher stage, older age, being female and diagnosis early in the study period were associated with higher odds for not receiving surgery. Low disposable income was associated with greater odds for no surgery in stage I and stage II patients as was living alone for stage I patients. Comorbidity, a short diagnostic interval and small diagnostic volume were all associated with higher odds for not undergoing surgery; but these factors did not appear to explain the association with income or living alone for early-stage NSCLC patients. Early-stage NSCLC patients with low income or who live alone are less likely to undergo surgery than those with a high income or who live with a partner, even after control for possible explanatory factors. Thus, even in a health care system with free, equal access to health services, disadvantaged groups are less likely to receive surgery for lung cancer. Copyright © 2012 Elsevier Ireland Ltd. All rights reserved.

The experiences of Taiwanese older individuals at different stages of Parkinson disease.

PubMed

Liao, Ying-Chun; Wu, Yih-Ru; Tsao, Lee-Ing; Lin, Hung-Ru

2013-12-01

Parkinson disease (PD) is a progressive neurological condition, usually occurring among older individuals. Along with increasing handicaps in daily life, patients with PD also face problems with psychosocial adjustment. This study explored the experiences of older Taiwanese individuals at different stages of PD. Qualitative design with in-depth interviews was conducted with participants being treated at the neurology outpatient department in a teaching hospital in northern Taiwan. The study included nine men and six women, aged 65-80 years, with PD at stages 1-4. Comparative analysis of the interviews revealed four themes: ignorance of symptoms, loss of control, gradual deterioration, and a deep sense of helplessness. In stage 1, symptoms were not significant at the onset of PD. For most participants, others first detected the symptoms, rather than themselves. During stage 2, although they could still care for themselves, they became very anxious when the effects of medication disappeared and their reactions slowed before they took the next dose. During stage 3, the physical capacity of the body decreased gradually and affected the patient's participation in social activities. In stage 4, older patients gradually became dependent on others in their daily lives. They were upset and worried that the symptoms would worsen and make them become a burden for their children. By understanding the perceptions of elderly patients at different stages of PD, this study has organized the key care requirements into four stages. These include the following: (1) provide more information on the disease in stage 1, (2) increase guidance on regular medication usage and establish a support system in stage 2, (3) highlight the importance of a safe living environment and encourage participation in support groups in stage 3, and (4) assist patients to find the meaning of life and value of existence in stage 4.

Spheno-Occipital Synchondrosis Fusion Correlates with Cervical Vertebrae Maturation.

PubMed

Fernández-Pérez, María José; Alarcón, José Antonio; McNamara, James A; Velasco-Torres, Miguel; Benavides, Erika; Galindo-Moreno, Pablo; Catena, Andrés

2016-01-01

The aim of this study was to determine the relationship between the closure stage of the spheno-occipital synchondrosis and the maturational stage of the cervical vertebrae (CVM) in growing and young adult subjects using cone beam computed tomography (CBCT). CBCT images with an extended field of view obtained from 315 participants (148 females and 167 males; mean age 15.6 ±7.3 years; range 6 to 23 years) were analyzed. The fusion status of the synchondrosis was determined using a five-stage scoring system; the vertebral maturational status was evaluated using a six-stage stratification (CVM method). Ordinal regression was used to study the ability of the synchondrosis stage to predict the vertebral maturation stage. Vertebrae and synchondrosis had a strong significant correlation (r = 0.89) that essential was similar for females (r = 0.88) and males (r = 0.89). CVM stage could be accurately predicted from synchondrosis stage by ordinal regression models. Prediction equations of the vertebral stage using synchondrosis stage, sex and biological age as predictors were developed. Thus this investigation demonstrated that the stage of spheno-occipital synchondrosis, as determined in CBCT images, is a reasonable indicator of growth maturation.

Spheno-Occipital Synchondrosis Fusion Correlates with Cervical Vertebrae Maturation

PubMed Central

Fernández-Pérez, María José; McNamara, James A.; Velasco-Torres, Miguel; Benavides, Erika; Galindo-Moreno, Pablo; Catena, Andrés

2016-01-01

The aim of this study was to determine the relationship between the closure stage of the spheno-occipital synchondrosis and the maturational stage of the cervical vertebrae (CVM) in growing and young adult subjects using cone beam computed tomography (CBCT). CBCT images with an extended field of view obtained from 315 participants (148 females and 167 males; mean age 15.6 ±7.3 years; range 6 to 23 years) were analyzed. The fusion status of the synchondrosis was determined using a five-stage scoring system; the vertebral maturational status was evaluated using a six-stage stratification (CVM method). Ordinal regression was used to study the ability of the synchondrosis stage to predict the vertebral maturation stage. Vertebrae and synchondrosis had a strong significant correlation (r = 0.89) that essential was similar for females (r = 0.88) and males (r = 0.89). CVM stage could be accurately predicted from synchondrosis stage by ordinal regression models. Prediction equations of the vertebral stage using synchondrosis stage, sex and biological age as predictors were developed. Thus this investigation demonstrated that the stage of spheno-occipital synchondrosis, as determined in CBCT images, is a reasonable indicator of growth maturation. PMID:27513752

Recommendations for choosing an analysis method that controls Type I error for unbalanced cluster sample designs with Gaussian outcomes.

PubMed

Johnson, Jacqueline L; Kreidler, Sarah M; Catellier, Diane J; Murray, David M; Muller, Keith E; Glueck, Deborah H

2015-11-30

We used theoretical and simulation-based approaches to study Type I error rates for one-stage and two-stage analytic methods for cluster-randomized designs. The one-stage approach uses the observed data as outcomes and accounts for within-cluster correlation using a general linear mixed model. The two-stage model uses the cluster specific means as the outcomes in a general linear univariate model. We demonstrate analytically that both one-stage and two-stage models achieve exact Type I error rates when cluster sizes are equal. With unbalanced data, an exact size α test does not exist, and Type I error inflation may occur. Via simulation, we compare the Type I error rates for four one-stage and six two-stage hypothesis testing approaches for unbalanced data. With unbalanced data, the two-stage model, weighted by the inverse of the estimated theoretical variance of the cluster means, and with variance constrained to be positive, provided the best Type I error control for studies having at least six clusters per arm. The one-stage model with Kenward-Roger degrees of freedom and unconstrained variance performed well for studies having at least 14 clusters per arm. The popular analytic method of using a one-stage model with denominator degrees of freedom appropriate for balanced data performed poorly for small sample sizes and low intracluster correlation. Because small sample sizes and low intracluster correlation are common features of cluster-randomized trials, the Kenward-Roger method is the preferred one-stage approach. Copyright © 2015 John Wiley & Sons, Ltd.

Meta‐analysis using individual participant data: one‐stage and two‐stage approaches, and why they may differ

PubMed Central

Ensor, Joie; Riley, Richard D.

2016-01-01

Meta‐analysis using individual participant data (IPD) obtains and synthesises the raw, participant‐level data from a set of relevant studies. The IPD approach is becoming an increasingly popular tool as an alternative to traditional aggregate data meta‐analysis, especially as it avoids reliance on published results and provides an opportunity to investigate individual‐level interactions, such as treatment‐effect modifiers. There are two statistical approaches for conducting an IPD meta‐analysis: one‐stage and two‐stage. The one‐stage approach analyses the IPD from all studies simultaneously, for example, in a hierarchical regression model with random effects. The two‐stage approach derives aggregate data (such as effect estimates) in each study separately and then combines these in a traditional meta‐analysis model. There have been numerous comparisons of the one‐stage and two‐stage approaches via theoretical consideration, simulation and empirical examples, yet there remains confusion regarding when each approach should be adopted, and indeed why they may differ. In this tutorial paper, we outline the key statistical methods for one‐stage and two‐stage IPD meta‐analyses, and provide 10 key reasons why they may produce different summary results. We explain that most differences arise because of different modelling assumptions, rather than the choice of one‐stage or two‐stage itself. We illustrate the concepts with recently published IPD meta‐analyses, summarise key statistical software and provide recommendations for future IPD meta‐analyses. © 2016 The Authors. Statistics in Medicine published by John Wiley & Sons Ltd. PMID:27747915

Adherence to GOLD guideline treatment recommendations among pulmonologists in Turkey.

PubMed

Sen, Elif; Guclu, Salih Zeki; Kibar, Isil; Ocal, Ulku; Yilmaz, Veysel; Celik, Onur; Cimen, Filiz; Topcu, Fusun; Orhun, Meltem; Tereci, Hikmet; Konya, Aylin; Ar, Idilhan; Saryal, Sevgi

2015-01-01

Low adherence to Global initiative for chronic Obstructive Lung Disease (GOLD) guideline recommendations has been reported worldwide. There has been no study on the adherence to GOLD guidelines for COPD treatment in Turkey. To investigate the rates of adherence to GOLD 2010 guidelines for COPD treatment among pulmonologists. A multi-center, cross-sectional, observational study was carried out in eleven pulmonary outpatient clinics across Turkey. Adherence to GOLD was evaluated through hospital records. Demographic and clinical data were recorded. Study included 719 patients (mean age: 62.9±9.7 years; males 85.4%) of whom 16 was classified as GOLD Stage I, 238 as II, 346 as III, and 119 as IV, and only 59.5% received appropriate treatment. Rates of guideline adherence varied across GOLD stages (I, 6.3%; II, 14.7%; III, 84.4%; and IV, 84%). Causes of inappropriate therapies were overtreatment (Stage I, 100% and Stage II, 91.1%), undertreatment (Stage III, 3.3% and Stage IV, 10.9%) and lack of treatment (Stage II, 3.8%; Stage III, 2.3%; and Stage IV, 5.9%). The most preferred regimen (43.4%) was long-acting β2-agonist-inhaled corticosteroid-long-acting muscarinic antagonist. Overall, 614 patients (89%) received treatment containing inhaled corticosteroid. Pulmonologists in Turkey have low rates of adherence to GOLD guidelines in COPD treatment. Inappropriateness of therapies was due to overtreatment in early stages and excessive use of inhaled corticosteroid (ICS) in all disease stages.

A modified varying-stage adaptive phase II/III clinical trial design.

PubMed

Dong, Gaohong; Vandemeulebroecke, Marc

2016-07-01

Conventionally, adaptive phase II/III clinical trials are carried out with a strict two-stage design. Recently, a varying-stage adaptive phase II/III clinical trial design has been developed. In this design, following the first stage, an intermediate stage can be adaptively added to obtain more data, so that a more informative decision can be made. Therefore, the number of further investigational stages is determined based upon data accumulated to the interim analysis. This design considers two plausible study endpoints, with one of them initially designated as the primary endpoint. Based on interim results, another endpoint can be switched as the primary endpoint. However, in many therapeutic areas, the primary study endpoint is well established. Therefore, we modify this design to consider one study endpoint only so that it may be more readily applicable in real clinical trial designs. Our simulations show that, the same as the original design, this modified design controls the Type I error rate, and the design parameters such as the threshold probability for the two-stage setting and the alpha allocation ratio in the two-stage setting versus the three-stage setting have a great impact on the design characteristics. However, this modified design requires a larger sample size for the initial stage, and the probability of futility becomes much higher when the threshold probability for the two-stage setting gets smaller. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.

Students' Development of Representational Competence Through the Sense of Touch

NASA Astrophysics Data System (ADS)

Magana, Alejandra J.; Balachandran, Sadhana

2017-06-01

Electromagnetism is an umbrella encapsulating several different concepts like electric current, electric fields and forces, and magnetic fields and forces, among other topics. However, a number of studies in the past have highlighted the poor conceptual understanding of electromagnetism concepts by students even after instruction. This study aims to identify novel forms of "hands-on" instruction that can result in representational competence and conceptual gain. Specifically, this study aimed to identify if the use of visuohaptic simulations can have an effect on student representations of electromagnetic-related concepts. The guiding questions is How do visuohaptic simulations influence undergraduate students' representations of electric forces? Participants included nine undergraduate students from science, technology, or engineering backgrounds who participated in a think-aloud procedure while interacting with a visuohaptic simulation. The think-aloud procedure was divided in three stages, a prediction stage, a minimally visual haptic stage, and a visually enhanced haptic stage. The results of this study suggest that students' accurately characterized and represented the forces felt around a particle, line, and ring charges either in the prediction stage, a minimally visual haptic stage or the visually enhanced haptic stage. Also, some students accurately depicted the three-dimensional nature of the field for each configuration in the two stages that included a tactile mode, where the point charge was the most challenging one.

A Phase I/II Study of Oblimersen Plus Cisplatin and Fluorouracil in Gastric & Esophageal Junction Cancer

ClinicalTrials.gov

2015-06-10

Adenocarcinoma of the Esophagus; Adenocarcinoma of the Gastroesophageal Junction; Diffuse Adenocarcinoma of the Stomach; Intestinal Adenocarcinoma of the Stomach; Mixed Adenocarcinoma of the Stomach; Recurrent Esophageal Cancer; Recurrent Gastric Cancer; Squamous Cell Carcinoma of the Esophagus; Stage III Esophageal Cancer; Stage IIIA Gastric Cancer; Stage IIIB Gastric Cancer; Stage IIIC Gastric Cancer; Stage IV Esophageal Cancer; Stage IV Gastric Cancer

Analysing growth and development of plants jointly using developmental growth stages

PubMed Central

Dambreville, Anaëlle; Lauri, Pierre-Éric; Normand, Frédéric; Guédon, Yann

2015-01-01

Background and Aims Plant growth, the increase of organ dimensions over time, and development, the change in plant structure, are often studied as two separate processes. However, there is structural and functional evidence that these two processes are strongly related. The aim of this study was to investigate the co-ordination between growth and development using mango trees, which have well-defined developmental stages. Methods Developmental stages, determined in an expert way, and organ sizes, determined from objective measurements, were collected during the vegetative growth and flowering phases of two cultivars of mango, Mangifera indica. For a given cultivar and growth unit type (either vegetative or flowering), a multistage model based on absolute growth rate sequences deduced from the measurements was first built, and then growth stages deduced from the model were compared with developmental stages. Key Results Strong matches were obtained between growth stages and developmental stages, leading to a consistent definition of integrative developmental growth stages. The growth stages highlighted growth asynchronisms between two topologically connected organs, namely the vegetative axis and its leaves. Conclusions Integrative developmental growth stages emphasize that developmental stages are closely related to organ growth rates. The results are discussed in terms of the possible physiological processes underlying these stages, including plant hydraulics, biomechanics and carbohydrate partitioning. PMID:25452250

[Analysis of histoprognostic factors for the non metastatic rectal cancer in a west Algerian series of 58 cases].

PubMed

Mesli, Smain Nabil; Regagba, Derbali; Tidjane, Anisse; Benkalfat, Mokhtar; Abi-Ayad, Chakib

2016-01-01

The aim of our study was to analyze histoprognostic factors in patients with non-metastatic rectal cancer operated at the division of surgery "A" in Tlemcen, west Algeria, over a period of six years. Retrospective study of 58 patients with rectal adenocarcinoma. Evaluation criterion was survival. Parameters studied were sex, age, tumor stage, tumor recurrence. The average age was 58 years, 52% of men and 48% of women, with sex-ratio (1,08). Tumor seat was: middle rectum 41.37%, lower rectum 34.48% and upper rectum 24.13%. Concerning TNM clinical staging, patients were classified as stage I (17.65%), stage II (18.61%), stage III (53.44%) and stage IV (7.84%). Median overall survival was 40 months ±2,937 months. Survival based on tumor staging: stage III and IV had a lower 3 years survival rate (19%) versus stage I, II which had a survival rate of 75% (P = 0.000) (95%). Patients with tumor recurrences had a lower 3 years survival rate compared to those who had no tumoral recurrences (30.85% vs 64.30% P = 0.043). In this series, univariate analysis of prognostic factors affecting survival allowed to retain only three factors influencing survival: tumor size, stage and tumor recurrences. In multivariate analysis using Cox's model only one factor was retained: tumor recurrence.

Relationship between dental calcification and skeletal maturation in a Peruvian sample.

PubMed

Lecca-Morales, Rocío M; Carruitero, Marcos J

2017-01-01

the objective of the study was to determine the relationship between dental calcification stages and skeletal maturation in a Peruvian sample. panoramic, cephalometric and carpal radiographs of 78 patients (34 girls and 44 boys) between 7 and 17 years old (9.90 ± 2.5 years) were evaluated. Stages of tooth calcification of the mandibular canine, first premolar, second premolar, and second molar and the skeletal maturation with a hand-wrist and a cervical vertebrae method were assessed. The relationships between the stages were assessed using Spearman's correlation coefficient. Additionally, the associations of mandibular and pubertal growth peak stages with tooth calcification were evaluated by Fisher's exact test. all teeth showed positive and statistically significant correlations, the highest correlation was between the mandibular second molar calcification stages with hand-wrist maturation stages (r = 0.758, p < 0.001) and with vertebrae cervical maturation stages (r = 0.605, p < 0.001). The pubertal growth spurt was found in the G stage of calcification of the second mandibular molar, and the mandibular growth peak was found in the F stage of calcification of the second molar. there was a positive relationship between dental calcification stages and skeletal maturation stages by hand-wrist and cervical vertebrae methods in the sample studied. Dental calcification stages of the second mandibular molar showed the highest positive correlation with the hand-wrist and cervical vertebrae stages.

Stages of Change or Changes of Stage? Predicting Transitions in Transtheoretical Model Stages in Relation to Healthy Food Choice

ERIC Educational Resources Information Center

Armitage, Christopher J.; Sheeran, Paschal; Conner, Mark; Arden, Madelynne A.

2004-01-01

Relatively little research has examined factors that account for transitions between transtheoretical model (TTM) stages of change. The present study (N=787) used sociodemographic, TTM, and theory of planned behavior (TPB) variables, as well as theory-driven interventions to predict changes in stage. Longitudinal analyses revealed that…

Is Single-stage Revision Safe Following Infected Total Knee Arthroplasty? A Critical Review.

PubMed

Vaishya, Raju; Agarwal, Amit Kumar; Rawat, Sudheer K; Singh, Harsh; Vijay, Vipul

2017-08-30

With the improvement in outcomes and modern prosthesis design, total knee arthroplasty (TKA) has now become a commonly performed surgery. It is postulated that a total of 2-5% of the primary and revision TKA becomes infected every year, requiring a revision procedure which to date is the conventional two-stage revision. The diagnosis and treatment of these periprosthetic infections is a major and challenging task, as it requires precise identification of the pathogen, meticulous debridement, and postoperative rehabilitation. To date, there have been very few studies in existing literature comparing the outcomes of single-stage versus two-stage procedure in infected TKA. The aim of the review was to provide the clinicians an insight into the outcome of the single-stage procedure compared to two-stage procedures and to suggest ways to improve the results further. In the following critical review, a total of 669 cases that underwent either a single or two-stage revision for infected TKA were studied. The postoperative functional scores were comparable in most studies during the early postoperative period. Our data supports the use of a single-stage revision surgery in infected TKA as an alternative to a conventional two-stage procedure. However, larger prospective and multicentric trials are required to validate our findings.

Language Learning at Key Stage 2: Findings from a Longitudinal Study

ERIC Educational Resources Information Center

Cable, Carrie; Driscoll, Patricia; Mitchell, Rosamond; Sing, Sue; Cremin, Teresa; Earl, Justine; Eyres, Ian; Holmes, Bernardette; Martin, Cynthia; Heins, Barbara

2012-01-01

This paper discusses some of the findings from a 3-year longitudinal study of language learning in the upper stage of English primary schools, i.e. at Key Stage 2. This largely qualitative study (commissioned by the then Department for Children, Schools and Families) was designed to explore and document developing provision and practice in a…

Logical Reasoning in Middle Childhood: A Study of Piagetian Concrete Operations Stage.

ERIC Educational Resources Information Center

Hooper, Frank H.; And Others

This 4-year longitudinal study of logical reasoning found complex interrelationships among different cognitive processes of children ages 6 to 15. Piaget's stage theory is discussed in the introduction, with a focus on the concrete operational stage in middle childhood. In the study, a representative array of logical concept tasks and short-term…

Dental Age Estimation (DAE): Data management for tooth development stages including the third molar. Appropriate censoring of Stage H, the final stage of tooth development.

PubMed

Roberts, Graham J; McDonald, Fraser; Andiappan, Manoharan; Lucas, Victoria S

2015-11-01

The final stage of dental development of third molars is usually helpful to indicate whether or not a subject is aged over 18 years. A complexity is that the final stage of development is unlimited in its upper border. Investigators usually select an inappropriate upper age limit or censor point for this tooth development stage. The literature was searched for appropriate data sets for dental age estimation and those that provided the count (n), the mean (x¯), and the standard deviation (sd) for each of the tooth development stages. The Demirjian G and Demirjian H were used for this study. Upper and lower limits of the Stage G and Stage H data were calculated limiting the data to plus or minus three standard deviations from the mean. The upper border of Stage H was limited by appropriate censoring at the maximum value for Stage G. The maximum age at attainment from published data, for Stage H, ranged from 22.60 years to 34.50 years. These data were explored to demonstrate how censoring provides an estimate for the correct maximum age for the final stage of Stage H as 21.64 years for UK Caucasians. This study shows that confining the data array of individual tooth developments stages to ± 3sd provides a reliable and logical way of censoring the data for tooth development stages with a Normal distribution of data. For Stage H this is inappropriate as it is unbounded in its upper limit. The use of a censored data array for Stage H using Percentile values is appropriate. This increases the reliability of using third molar Stage H alone to determine whether or not an individual is over 18 years old. For Stage H, individual ancestral groups should be censored using the same technique. Copyright © 2015 Elsevier Ltd and Faculty of Forensic and Legal Medicine. All rights reserved.

Assessment of Growth Using Mandibular Canine Calcification Stages and Its Correlation with Modified MP3 Stages.

PubMed

Nayak, Reshma; Nayak, Us Krishna; Hegde, Gautam

2010-01-01

Orthodontic diagnosis and treatment planning for growing children must involve growth prediction, especially in the treatment of skeletal problems. Studies have shown that a strong association exists between skeletal maturity and dental calcification stages. The present study was therefore taken up to provide a simple and practical method for assessing skeletal maturity using a dental periapical film and standard dental X-ray machine, to compare the developmental stages of the mandibular canine with that of developmental stages of modified MP3 and to find out if any correlation exists, to determine if the developmental stages of the mandibular canine alone can be used as a reliable indicator for assessment of skeletal maturity. A total of 160 periapical radiographs (80 males and 80 females), of the mandibular right canine and the MP3 region was taken and assessed according to the Dermirjian's stages of dental calcification and the modified MP3 stages. The correlation between the developmental stages of MP3 and the mandibular right canine in male and female groups, is of high statistical significance (p = 0.001). The correlation coefficient between MP3 stages and developmental stages of mandibular canine and chronological age in male and females was found to be not significant. The correlation between the mandibular canine calcification stages and MP3 stages was found to be significant. The developmental stages of the mandibular canine could be used very reliably as a sole indicator for assessment of skeletal maturity.

DEVELOPMENT OF COLD CLIMATE HEAT PUMP USING TWO-STAGE COMPRESSION

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

Shen, Bo; Rice, C Keith; Abdelaziz, Omar

2015-01-01

This paper uses a well-regarded, hardware based heat pump system model to investigate a two-stage economizing cycle for cold climate heat pump applications. The two-stage compression cycle has two variable-speed compressors. The high stage compressor was modelled using a compressor map, and the low stage compressor was experimentally studied using calorimeter testing. A single-stage heat pump system was modelled as the baseline. The system performance predictions are compared between the two-stage and single-stage systems. Special considerations for designing a cold climate heat pump are addressed at both the system and component levels.

Postoperative radiotherapy and tumor recurrence after complete resection of stage II/III thymic tumor: a meta-analysis of cohort studies

PubMed Central

Ma, Jietao; Sun, Xin; Huang, Letian; Xiong, Zhicheng; Yuan, Meng; Zhang, Shuling; Han, Cheng-Bo

2016-01-01

Background Whether postoperative radiotherapy (PORT) is effective for reducing the recurrence risk in patients who received complete resection of the stage II or III thymic tumors has not been determined. A meta-analysis was performed by combining the results of all available controlled trials. Methods PubMed, Cochrane’s Library, and the Embase databases were searched for studies which compared the recurrence data for patients with complete resection of the stage II or III thymic tumors assigned to an observing group, or a PORT group. A random effect model was applied to combine the results. Results Nineteen studies, all designed as retrospective cohort studies were included. These studies included 663 patients of PORT group and 617 patients of observing group. The recurrence rate for the patients in PORT group and observing group were 12.4% and 11.5%, respectively. Results of our study indicated that PORT has no significant influence on recurrent risk in patients with stage II or III thymic tumor after complete resection (odds ratio 1.02, 95% confidence interval 0.55–1.90, P=0.96). When stratified by stages, our meta-analyses did not indicate any significant effects of PORT on recurrent outcomes in either the stage II or the stage III patients. Moreover, subsequent analysis limited to studies only including patients with thymoma or thymic carcinoma also did not support the benefits of PORT on recurrent outcomes. Conclusion Although derived from retrospective cohort studies, current evidence did not support any benefit of PORT on recurrent risk in patients with complete resection of the stage II or III thymic tumors. PMID:27524907

Small Launch Vehicle Concept Development for Affordable Multi-Stage Inline Configurations

NASA Technical Reports Server (NTRS)

Beers, Benjamin R.; Waters, Eric D.; Philips, Alan D.; Threet, Grady E., Jr.

2014-01-01

The Advanced Concepts Office at NASA's George C. Marshall Space Flight Center conducted a study of two configurations of a three stage, inline, liquid propellant small launch vehicle concept developed on the premise of maximizing affordability by targeting a specific payload capability range based on current industry demand. The initial configuration, NESC-1, employed liquid oxygen as the oxidizer and rocket propellant grade kerosene as the fuel in all three stages. The second and more heavily studied configuration, NESC-4, employed liquid oxygen and rocket propellant grade kerosene on the first and second stages and liquid oxygen and liquid methane fuel on the third stage. On both vehicles, sensitivity studies were first conducted on specific impulse and stage propellant mass fraction in order to baseline gear ratios and drive the focus of concept development. Subsequent sensitivity and trade studies on the NESC-4 configuration investigated potential impacts to affordability due to changes in gross liftoff weight and/or vehicle complexity. Results are discussed at a high level to understand the severity of certain sensitivities and how those trade studies conducted can either affect cost, performance or both.

Small Launch Vehicle Concept Development for Affordable Multi-Stage Inline Configurations

NASA Technical Reports Server (NTRS)

Beers, Benjamin R.; Waters, Eric D.; Philips, Alan D.; Threet, Grady E. Jr.

2013-01-01

The Advanced Concepts Office at NASA's George C. Marshall Space Flight Center conducted a study of two configurations of a three-stage, inline, liquid propellant small launch vehicle concept developed on the premise of maximizing affordability by targeting a specific payload capability range based on current industry demand. The initial configuration, NESC-1, employed liquid oxygen as the oxidizer and rocket propellant grade kerosene as the fuel in all three stages. The second and more heavily studied configuration, NESC-4, employed liquid oxygen and RP-1 on the first and second stages and liquid oxygen and liquid methane fuel on the third stage. On both vehicles, sensitivity studies were first conducted on specific impulse and stage propellant mass fraction in order to baseline gear ratios and drive the focus of concept development. Subsequent sensitivity and trade studies on the NESC-4 concept investigated potential impacts to affordability due to changes in gross liftoff weight and/or vehicle complexity. Results are discussed at a high level to understand the impact severity of certain sensitivities and how those trade studies conducted can either affect cost, performance, or both.

Systematic review: The model for end-stage liver disease--should it replace Child-Pugh's classification for assessing prognosis in cirrhosis?

PubMed

Cholongitas, E; Papatheodoridis, G V; Vangeli, M; Terreni, N; Patch, D; Burroughs, A K

2005-12-01

Prognosis in cirrhotic patients has had a resurgence of interest because of liver transplantation and new therapies for complications of end-stage cirrhosis. The model for end-stage liver disease score is now used for allocation in liver transplantation waiting lists, replacing Child-Turcotte-Pugh score. However, there is debate as whether it is better in other settings of cirrhosis. To review studies comparing the accuracy of model for end-stage liver disease score vs. Child-Turcotte-Pugh score in non-transplant settings. Transjugular intrahepatic portosystemic shunt studies (with 1360 cirrhotics) only one of five, showed model for end-stage liver disease to be superior to Child-Turcotte-Pugh to predict 3-month mortality, but not for 12-month mortality. Prognosis of cirrhosis studies (with 2569 patients) none of four showed significant differences between the two scores for either short- or long-term prognosis whereas no differences for variceal bleeding studies (with 411 cirrhotics). Modified Child-Turcotte-Pugh score, by adding creatinine, performed similarly to model for end-stage liver disease score. Hepatic encephalopathy and hyponatraemia (as an index of ascites), both components of Child-Turcotte-Pugh score, add to the prognostic performance of model for end-stage liver disease score. Based on current literature, model for end-stage liver disease score does not perform better than Child-Turcotte-Pugh score in non-transplant settings. Modified Child-Turcotte-Pugh and model for end-stage liver disease scores need further evaluation.

A Phase 2 Study of Cediranib in Combination With Olaparib in Advanced Solid Tumors

ClinicalTrials.gov

2018-06-04

Estrogen Receptor Negative; HER2/Neu Negative; Metastatic Pancreatic Adenocarcinoma; Pancreatic Ductal Adenocarcinoma; Progesterone Receptor Negative; Stage III Breast Cancer AJCC v7; Stage III Non-Small Cell Lung Cancer AJCC v7; Stage III Pancreatic Cancer AJCC v6 and v7; Stage III Small Cell Lung Carcinoma AJCC v7; Stage IIIA Breast Cancer AJCC v7; Stage IIIA Non-Small Cell Lung Cancer AJCC v7; Stage IIIA Small Cell Lung Carcinoma AJCC v7; Stage IIIB Breast Cancer AJCC v7; Stage IIIB Non-Small Cell Lung Cancer AJCC v7; Stage IIIB Small Cell Lung Carcinoma AJCC v7; Stage IIIC Breast Cancer AJCC v7; Stage IV Breast Cancer AJCC v6 and v7; Stage IV Non-Small Cell Lung Cancer AJCC v7; Stage IV Pancreatic Cancer AJCC v6 and v7; Stage IV Small Cell Lung Carcinoma AJCC v7; Triple-Negative Breast Carcinoma; Unresectable Pancreatic Carcinoma

Describing the Process of Adopting Nutrition and Fitness Apps: Behavior Stage Model Approach

PubMed Central

Sproesser, Gudrun; Schupp, Harald T; Renner, Britta

2018-01-01

Background Although mobile technologies such as smartphone apps are promising means for motivating people to adopt a healthier lifestyle (mHealth apps), previous studies have shown low adoption and continued use rates. Developing the means to address this issue requires further understanding of mHealth app nonusers and adoption processes. This study utilized a stage model approach based on the Precaution Adoption Process Model (PAPM), which proposes that people pass through qualitatively different motivational stages when adopting a behavior. Objective To establish a better understanding of between-stage transitions during app adoption, this study aimed to investigate the adoption process of nutrition and fitness app usage, and the sociodemographic and behavioral characteristics and decision-making style preferences of people at different adoption stages. Methods Participants (N=1236) were recruited onsite within the cohort study Konstanz Life Study. Use of mobile devices and nutrition and fitness apps, 5 behavior adoption stages of using nutrition and fitness apps, preference for intuition and deliberation in eating decision-making (E-PID), healthy eating style, sociodemographic variables, and body mass index (BMI) were assessed. Results Analysis of the 5 behavior adoption stages showed that stage 1 (“unengaged”) was the most prevalent motivational stage for both nutrition and fitness app use, with half of the participants stating that they had never thought about using a nutrition app (52.41%, 533/1017), whereas less than one-third stated they had never thought about using a fitness app (29.25%, 301/1029). “Unengaged” nonusers (stage 1) showed a higher preference for an intuitive decision-making style when making eating decisions, whereas those who were already “acting” (stage 4) showed a greater preference for a deliberative decision-making style (F4,1012=21.83, P<.001). Furthermore, participants differed widely in their readiness to adopt nutrition and fitness apps, ranging from having “decided to” but not yet begun to act (stage 2; nutrition: 6.88%, 70/1017; fitness: 9.23%, 95/1029) to being “disengaged” following previous adoption (stage 5; nutrition: 13.77%, 140/1017; fitness: 15.06%, 155/1029). Conclusions Using a behavior stage model approach to describe the process of adopting nutrition and fitness apps revealed motivational stage differences between nonusers (being “unengaged,” having “decided not to act,” having “decided to act,” and being “disengaged”), which might contribute to a better understanding of the process of adopting mHealth apps and thus inform the future development of digital interventions. This study highlights that new user groups might be better reached by apps designed to address a more intuitive decision-making style. PMID:29535078

Describing the Process of Adopting Nutrition and Fitness Apps: Behavior Stage Model Approach.

PubMed

König, Laura M; Sproesser, Gudrun; Schupp, Harald T; Renner, Britta

2018-03-13

Although mobile technologies such as smartphone apps are promising means for motivating people to adopt a healthier lifestyle (mHealth apps), previous studies have shown low adoption and continued use rates. Developing the means to address this issue requires further understanding of mHealth app nonusers and adoption processes. This study utilized a stage model approach based on the Precaution Adoption Process Model (PAPM), which proposes that people pass through qualitatively different motivational stages when adopting a behavior. To establish a better understanding of between-stage transitions during app adoption, this study aimed to investigate the adoption process of nutrition and fitness app usage, and the sociodemographic and behavioral characteristics and decision-making style preferences of people at different adoption stages. Participants (N=1236) were recruited onsite within the cohort study Konstanz Life Study. Use of mobile devices and nutrition and fitness apps, 5 behavior adoption stages of using nutrition and fitness apps, preference for intuition and deliberation in eating decision-making (E-PID), healthy eating style, sociodemographic variables, and body mass index (BMI) were assessed. Analysis of the 5 behavior adoption stages showed that stage 1 ("unengaged") was the most prevalent motivational stage for both nutrition and fitness app use, with half of the participants stating that they had never thought about using a nutrition app (52.41%, 533/1017), whereas less than one-third stated they had never thought about using a fitness app (29.25%, 301/1029). "Unengaged" nonusers (stage 1) showed a higher preference for an intuitive decision-making style when making eating decisions, whereas those who were already "acting" (stage 4) showed a greater preference for a deliberative decision-making style (F 4,1012 =21.83, P<.001). Furthermore, participants differed widely in their readiness to adopt nutrition and fitness apps, ranging from having "decided to" but not yet begun to act (stage 2; nutrition: 6.88%, 70/1017; fitness: 9.23%, 95/1029) to being "disengaged" following previous adoption (stage 5; nutrition: 13.77%, 140/1017; fitness: 15.06%, 155/1029). Using a behavior stage model approach to describe the process of adopting nutrition and fitness apps revealed motivational stage differences between nonusers (being "unengaged," having "decided not to act," having "decided to act," and being "disengaged"), which might contribute to a better understanding of the process of adopting mHealth apps and thus inform the future development of digital interventions. This study highlights that new user groups might be better reached by apps designed to address a more intuitive decision-making style. ©Laura M König, Gudrun Sproesser, Harald T Schupp, Britta Renner. Originally published in JMIR Mhealth and Uhealth (http://mhealth.jmir.org), 13.03.2018.

Self-consistent modeling of electrochemical strain microscopy of solid electrolytes

DOE PAGES

Tselev, Alexander; Morozovska, Anna N.; Udod, Alexei; ...

2014-10-10

Electrochemical strain microscopy (ESM) employs a strong electromechanical coupling in solid ionic conductors to map ionic transport and electrochemical processes with nanometer-scale spatial resolution. To elucidate the mechanisms of the ESM image formation, we performed self-consistent numerical modeling of the electromechanical response in solid electrolytes under the probe tip in a linear, small-signal regime using the Boltzmann–Planck–Nernst–Einstein theory and Vegard's law while taking account of the electromigration and diffusion. We identified the characteristic time scales involved in the formation of the ESM response and found that the dynamics of the charge carriers in the tip-electrolyte system with blocking interfaces canmore » be described as charging of the diffuse layer at the tip-electrolyte interface through the tip contact spreading resistance. At the high frequencies used in the detection regime, the distribution of the charge carriers under the tip is governed by evanescent concentration waves generated at the tip-electrolyte interface. The ion drift length in the electric field produced by the tip determines the ESM response at high frequencies, which follows a 1/f asymptotic law. The electronic conductivity, as well as the electron transport through the electrode-electrolyte interface, do not have a significant effect on the ESM signal in the detection regime. The results indicate, however, that for typical solid electrolytes at room temperature, the ESM response originates at and contains information about the very surface layer of a sample, and the properties of the one-unit-cell-thick surface layer may significantly contribute to the ESM response, implying a high surface sensitivity and a high lateral resolution of the technique. On the other hand, it follows that a rigorous analysis of the ESM signals requires techniques that account for the discrete nature of a solid.« less

Metal-filled carbon nanotube based optical nanoantennas: bubbling, reshaping, and in situ characterization.

PubMed

Fan, Zheng; Tao, Xinyong; Cui, Xudong; Fan, Xudong; Zhang, Xiaobin; Dong, Lixin

2012-09-21

Controlled fabrication of metal nanospheres on nanotube tips for optical antennas is investigated experimentally. Resembling soap bubble blowing using a straw, the fabrication process is based on nanofluidic mass delivery at the attogram scale using metal-filled carbon nanotubes (m@CNTs). Two methods have been investigated including electron-beam-induced bubbling (EBIB) and electromigration-based bubbling (EMBB). EBIB involves the bombardment of an m@CNT with a high energy electron beam of a transmission electron microscope (TEM), with which the encapsulated metal is melted and flowed out from the nanotube, generating a metallic particle on a nanotube tip. In the case where the encapsulated materials inside the CNT have a higher melting point than what the beam energy can reach, EMBB is an optional process to apply. Experiments show that, under a low bias (2.0-2.5 V), nanoparticles can be formed on the nanotube tips. The final shape and crystallinity of the nanoparticles are determined by the cooling rate. Instant cooling occurs with a relatively large heat sink and causes the instant shaping of the solid deposit, which is typically similar to the shape of the molten state. With a smaller heat sink as a probe, it is possible to keep the deposit in a molten state. Instant cooling by separating the deposit from the probe can result in a perfect sphere. Surface and volume plasmons characterized with electron energy loss spectroscopy (EELS) prove that resonance occurs between a pair of as-fabricated spheres on the tip structures. Such spheres on pillars can serve as nano-optical antennas and will enable devices such as scanning near-field optical microscope (SNOM) probes, scanning anodes for field emitters, and single molecule detectors, which can find applications in bio-sensing, molecular detection, and high-resolution optical microscopy.

Spatiotemporal pH dynamics in concentration polarization near ion-selective membranes.

PubMed

Andersen, Mathias B; Rogers, David M; Mai, Junyu; Schudel, Benjamin; Hatch, Anson V; Rempe, Susan B; Mani, Ali

2014-07-08

We present a detailed analysis of the transient pH dynamics for a weak, buffered electrolyte subject to voltage-driven transport through an ion-selective membrane. We show that pH fronts emanate from the concentration polarization zone next to the membrane and that these propagating fronts change the pH in the system several units from its equilibrium value. The analysis is based on a 1D model using the unsteady Poisson-Nernst-Planck equations with nonequilibrium chemistry and without assumptions of electroneutrality or asymptotically thin electric double layers. Nonequilibrium chemical effects, especially for water splitting, are shown to be important for the dynamical and spatiotemporal evolution of the pH fronts. Nonetheless, the model also shows that at steady state the assumption of chemical equilibrium can still lead to good approximations of the global pH distribution. Moreover, our model shows that the transport of the hydronium ion in the extended space charge region is governed by a balance between electromigration and water self-ionization. On the basis of this observation, we present a simple model showing that the net flux of the hydronium ion is proportional to the length of the extended space charge region and the water self-ionization rate. To demonstrate these effects in practice, we have adopted the experiment of Mai et al. (Mai, J.; Miller, H.; Hatch, A. V. Spatiotemporal Mapping of Concentration Polarization Induced pH Changes at Nanoconstrictions. ACS Nano 2012, 6, 10206) as a model problem, and by including the full chemistry and transport, we show that the present model can capture the experimentally observed pH fronts. Our model can, among other things, be used to predict and engineer pH dynamics, which can be essential to the performance of membrane-based systems for biochemical separation and analysis.

Hair analysis for abused drugs by capillary zone electrophoresis with field-amplified sample stacking.

PubMed

Tagliaro, F; Manetto, G; Crivellente, F; Scarcella, D; Marigo, M

1998-04-05

The present paper describes the methodological optimisation and validation of a capillary zone electrophoresis method for the determination of morphine, cocaine and 3,4-methylenedioxymethamphetamine (MDMA) in hair, with injection based on field-amplified sample stacking. Diode array UV absorption detection was used to improve analytical selectivity and identification power. Analytical conditions: running buffer 100 mM potassium phosphate adjusted to pH 2.5 with phosphoric acid, applied potential 10 kV, temperature 20 degrees C, injection by electromigration at 10 kV for 10 s, detection by UV absorption at the fixed wavelength of 200 nm or by recording the full spectrum between 190 and 400 nm. Injection conditions: the dried hair extracts were reconstituted with a low-conductivity solvent (0.1 mM formic acid), the injection end of the capillary was dipped in water for 5 s without applying pressure (external rinse step), then a plug of 0.1 mM phosphoric acid was loaded by applying 0.5 psi for 10 s and, finally, the sample was injected electrokinetically at 10 kV for 10 s. Under the described conditions, the limit of detection was 2 ng/ml for MDMA, 8 ng/ml for cocaine and 6 ng/ml for morphine (with a signal-to-noise ratio of 5). The lowest concentration suitable for recording interpretable spectra was about 10-20-times the limit of detection of each analyte. The intraday and day-to-day reproducibility of migration times (n = 6), with internal standardisation, was characterised by R.S.D. values < or = 0.6%; peak area R.S.D.s were better than 10% in intraday and than 15% in day-to-day experiments. Analytical linearity was good with R2 better than 0.9990 for all the analytes.

Electrokinetic treatment of polluted soil at pilot level coupled to an advanced oxidation process of its wastewater

NASA Astrophysics Data System (ADS)

Ochoa, B.; Ramos, L.; Garibay, A.; Pérez-Corona, M.; Cuevas, M. C.; Cárdenas, J.; Teutli, M.; Bustos, E.

2016-02-01

Soil contaminated with hydrocarbons is a current problem of great importance. These contaminants may be toxic, can retain water and block gas exchange with the atmosphere, which produces a poor-quality soil unsuitable for ecological health. Electroremediation is among the treatments for the removal of such contaminants. In this research, a pilot-level electroremediation test was applied using a circular arrangement of electrodes with a Ti cathode at the middle of the cell surrounded by six IrO2-Ta2O5 | Ti anodes. The presence of an NaOH electrolyte helps to develop the electromigration and electro-osmosis of gasoline molecules (at 1126 mg kg-1) surrounded by Na+ ions. The hydrocarbons are directed towards the cathode and subsequently removed in an aqueous Na+ - hydrocarbon solution, and the -OH migrates to the anode. During electrokinetic treatment, the physicochemical characteristics of the soil close to either the cathode or anode and at the half-cell were evaluated during the three weeks of treatment. During that time, more than 80% of hydrocarbons were removed. Hydrocarbons removed by the electrokinetic treatment of gasoline-polluted soil were collected in a central wastewater compartment and subsequently treated with a Fenton-type advanced oxidation process. This achieved more than 70% mineralization of the hydrocarbons to CO2 and H2O within 1.5 h; its low toxicity status was verified using the Deltatox® kit test. With this approach, the residual water complied with the permissible limits of COD, pH, and electrical conductivity for being discharged into water bodies, according to Mexican norm NOM-001-SEMARNAT-1996.

Accelerated Metastable Solid-liquid Interdiffusion Bonding with High Thermal Stability and Power Handling

NASA Astrophysics Data System (ADS)

Huang, Ting-Chia; Smet, Vanessa; Kawamoto, Satomi; Pulugurtha, Markondeya R.; Tummala, Rao R.

2018-01-01

Emerging high-performance systems are driving the need for advanced packaging solutions such as 3-D integrated circuits (ICs) and 2.5-D system integration with increasing performance and reliability requirements for off-chip interconnections. Solid-liquid interdiffusion (SLID) bonding resulting in all-intermetallic joints has been proposed to extend the applicability of solders, but faces fundamental and manufacturing challenges hindering its wide adoption. This paper introduces a Cu-Sn SLID interconnection technology, aiming at stabilization of the microstructure in the Cu6Sn5 metastable phase rather than the usual stable Cu3Sn phase. This enables formation of a void-free interface yielding higher mechanical strength than standard SLID bonding, as well as significantly reducing the transition time. The metastable SLID technology retains the benefits of standard SLID with superior I/O pitch scalability, thermal stability and current handling capability, while advancing assembly manufacturability. In the proposed concept, the interfacial reaction is controlled by introducing Ni(P) diffusion barrier layers, designed to effectively isolate the metastable Cu6Sn5 phase preventing any further transformation. Theoretical diffusion and kinetic models were applied to design the Ni-Cu-Sn interconnection stack to achieve the targeted joint composition. A daisy chain test vehicle was used to demonstrate this technology as a first proof of concept. Full transition to Cu6Sn5 was successfully achieved within a minute at 260°C as confirmed by scanning electron microscope (SEM) and x-ray energy dispersive spectroscopy (XEDS) analysis. The joint composition was stable through 10× reflow, with outstanding bond strength averaging 90 MPa. The metastable SLID interconnections also showed excellent electromigration performance, surviving 500 h of current stressing at 105 A/cm2 at 150°C.

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

Lawrence R. Sita

Ferrocene-based molecular components for nanoelectronics offer a number of distinct advantages relative to all carbon frameworks due to metal-centered molecular states that should be closer in energy to the Fermi levels of the metal electrodes in metal / molecule / metal heterojunctions. Given this, the overall goal of the project was to investigate the conduction physics of a variety of proposed ferrocene diode / transistor designs in order to address the fundamental question; can electron transport within nm-length scale structures be modulated in a controlled fashion? During the funded period, substantial progress towards achieving this goal was made by surmountingmore » a number of scientific and technical obstacles. More specifically, a concise and general synthetic route to several mono- and diferrocene dithiols and monothiols was achieved that now allows for the directed and controlled assembly of a variety of metal / molecule /metal test structures for the single molecule conductance measurements and the fabrication of self-assembled monolayers (SAMs) on Au(111) that are amenable to quantitative electrochemical characterization of electron-transfer rates. Most importantly, by using an electromigrated test structure, reproducible I/V data for one of the ferrocene dithiol molecules have been collected which exhibit surprisingly high conductance. Exceptional agreement of this result with theory serves to substantiate the original hypothesis that metal-centered states within a molecular bridge can indeed serve to establish higher conductance relative to all-organic molecular bridges. Overall, the successful demonstration of the ability of ferrocene-molecular frameworks to serve as exceptional molecular conductors will play an important role in the continued evolution in design of molecular components for nanoelectronic devices, which in turn, will have a positive impact on the science and potential technologies associated with these systems.« less

Reliability and Characteristics of Wafer-Level Chip-Scale Packages under Current Stress

NASA Astrophysics Data System (ADS)

Chen, Po-Ying; Kung, Heng-Yu; Lai, Yi-Shao; Hsiung Tsai, Ming; Yeh, Wen-Kuan

2008-02-01

In this work, we present a novel approach and method for elucidating the characteristics of wafer-level chip-scale packages (WLCSPs) for electromigration (EM) tests. The die in WLCSP was directly attached to the substrate via a soldered interconnect. The shrinking of the area of the die that is available for power, and the solder bump also shrinks the volume and increases the density of electrons for interconnect efficiency. The bump current density now approaches to 106 A/cm2, at which point the EM becomes a significant reliability issue. As known, the EM failure depends on numerous factors, including the working temperature and the under bump metallization (UBM) thickness. A new interconnection geometry is adopted extensively with moderate success in overcoming larger mismatches between the displacements of components during current and temperature changes. Both environments and testing parameters for WLCSP are increasingly demanded. Although failure mechanisms are considered to have been eliminated or at least made manageable, new package technologies are again challenging its process, integrity and reliability. WLCSP technology was developed to eliminate the need for encapsulation to ensure compatibility with smart-mount technology (SMT). The package has good handing properties but is now facing serious reliability problems. In this work, we investigated the reliability of a WLCSP subjected to different accelerated current stressing conditions at a fixed ambient temperature of 125 °C. A very strong correlation exists between the mean time to failure (MTTF) of the WLCSP test vehicle and the mean current density that is carried by a solder joint. A series of current densities were applied to the WLCSP architecture; Black's power law was employed in a failure mode simulation. Additionally, scanning electron microscopy (SEM) was adopted to determine the differences existing between high- and low-current-density failure modes.

Coupled simulation of CFD-flight-mechanics with a two-species-gas-model for the hot rocket staging

NASA Astrophysics Data System (ADS)

Li, Yi; Reimann, Bodo; Eggers, Thino

2016-11-01

The hot rocket staging is to separate the lowest stage by directly ignite the continuing-stage-motor. During the hot staging, the rocket stages move in a harsh dynamic environment. In this work, the hot staging dynamics of a multistage rocket is studied using the coupled simulation of Computational Fluid Dynamics and Flight Mechanics. Plume modeling is crucial for a coupled simulation with high fidelity. A 2-species-gas model is proposed to simulate the flow system of the rocket during the staging: the free-stream is modeled as "cold air" and the exhausted plume from the continuing-stage-motor is modeled with an equivalent calorically-perfect-gas that approximates the properties of the plume at the nozzle exit. This gas model can well comprise between the computation accuracy and efficiency. In the coupled simulations, the Navier-Stokes equations are time-accurately solved in moving system, with which the Flight Mechanics equations can be fully coupled. The Chimera mesh technique is utilized to deal with the relative motions of the separated stages. A few representative staging cases with different initial flight conditions of the rocket are studied with the coupled simulation. The torque led by the plume-induced-flow-separation at the aft-wall of the continuing-stage is captured during the staging, which can assist the design of the controller of the rocket. With the increasing of the initial angle-of-attack of the rocket, the staging quality becomes evidently poorer, but the separated stages are generally stable when the initial angle-of-attack of the rocket is small.

Impact of SciELO and MEDLINE indexing on submissions to Jornal de Pediatria.

PubMed

Blank, Danilo; Buchweitz, Claudia; Procianoy, Renato S

2005-01-01

To evaluate the impact of SciELO and MEDLINE indexing on the number of articles submitted to Jornal de Pediatria. Analysis of total article submission, submission of articles from foreign countries and acceptance figures in the following periods: stage I - pre-website (Jan 2000-Mar 2001); stage II - website (Apr 2001-Jul 2002); stage III - SciELO (Aug 2002-Aug 2003); stage IV - MEDLINE (Sep 2003-Dec 2004). There was a significant trend toward linear increase in the number of submissions along the study period (p = 0.009). The number of manuscripts submitted in stages I through IV was 184, 240, 297, and 482, respectively. The number of submissions was similar in stages I and II (p = 0.148), but statistically higher in Stage III (p < 0.001 vs. Stage I and p = 0.006 vs. Stage II) and Stage IV (p < 0.001 vs. stages I and II, and p < 0.05 vs. stage III). The rate of article acceptance decreased during the study period. The number of original articles published has been stable since the 2001 March/April issue (n = 10), when the journal reached a printed page limit, leading to stricter judgment criteria and a relative decrease in acceptance rate. The number of foreign submissions in stages I through IV was 1, 2, zero and 17, respectively, with p < 0.001 for the comparison of stage IV with previous stages. SciELO indexing was associated with an increase in Brazilian manuscript submissions to Jornal de Pediatria, whereas MEDLINE indexing led to an increase in both Brazilian and foreign submissions.

Phase I Study of Cetuximab With RO4929097 in Metastatic Colorectal Cancer

ClinicalTrials.gov

2015-05-15

Colon Mucinous Adenocarcinoma; Colon Signet Ring Cell Adenocarcinoma; Rectal Mucinous Adenocarcinoma; Rectal Signet Ring Cell Adenocarcinoma; Recurrent Colon Carcinoma; Recurrent Rectal Carcinoma; Stage IVA Colon Cancer; Stage IVA Rectal Cancer; Stage IVB Colon Cancer; Stage IVB Rectal Cancer

The Effects of Probe Similarity on Retrieval and Comparison Processes in Associative Recognition.

PubMed

Zhang, Qiong; Walsh, Matthew M; Anderson, John R

2017-02-01

In this study, we investigated the information processing stages underlying associative recognition. We recorded EEG data while participants performed a task that involved deciding whether a probe word triple matched any previously studied triple. We varied the similarity between probes and studied triples. According to a model of associative recognition developed in the Adaptive Control of Thought-Rational cognitive architecture, probe similarity affects the duration of the retrieval stage: Retrieval is fastest when the probe is similar to a studied triple. This effect may be obscured, however, by the duration of the comparison stage, which is fastest when the probe is not similar to the retrieved triple. Owing to the opposing effects of probe similarity on retrieval and comparison, overall RTs provide little information about each stage's duration. As such, we evaluated the model using a novel approach that decomposes the EEG signal into a sequence of latent states and provides information about the durations of the underlying information processing stages. The approach uses a hidden semi-Markov model to identify brief sinusoidal peaks (called bumps) that mark the onsets of distinct cognitive stages. The analysis confirmed that probe type has opposite effects on retrieval and comparison stages.

Comparative performances of staging systems for early hepatocellular carcinoma.

PubMed

Nathan, Hari; Mentha, Gilles; Marques, Hugo P; Capussotti, Lorenzo; Majno, Pietro; Aldrighetti, Luca; Pulitano, Carlo; Rubbia-Brandt, Laura; Russolillo, Nadia; Philosophe, Benjamin; Barroso, Eduardo; Ferrero, Alessandro; Schulick, Richard D; Choti, Michael A; Pawlik, Timothy M

2009-08-01

Several staging systems for patients with hepatocellular carcinoma (HCC) have been proposed, but studies of their prognostic accuracy have yielded conflicting conclusions. Stratifying patients with early HCC is of particular interest because these patients may derive the greatest benefit from intervention, yet no studies have evaluated the comparative performances of staging systems in patients with early HCC. A retrospective cohort study was performed using data on 379 patients who underwent liver resection or liver transplantation for HCC at six major hepatobiliary centres in the USA and Europe. The staging systems evaluated were: the Okuda staging system, the International Hepato-Pancreato-Biliary Association (IHPBA) staging system, the Cancer of the Liver Italian Programme (CLIP) score, the Barcelona Clinic Liver Cancer (BCLC) staging system, the Japanese Integrated Staging (JIS) score and the American Joint Committee on Cancer/International Union Against Cancer (AJCC/UICC) staging system, 6th edition. A recently proposed early HCC prognostic score was also evaluated. The discriminative abilities of the staging systems were evaluated using Cox proportional hazards models and the bootstrap-corrected concordance index (c). Overall survival of the cohort was 74% at 3 years and 52% at 5 years, with a median survival of 62 months. Most systems demonstrated poor discriminatory ability (P > 0.05 on Cox proportional hazards analysis, c approximately 0.5). However, the AJCC/UICC system clearly stratified patients (P < 0.001, c = 0.59), albeit only into two groups. The early HCC prognostic score also clearly stratified patients (P < 0.001, c = 0.60) and identified three distinct prognostic groups. The early HCC prognostic score is superior to the AJCC/UICC staging system (6th edition) for predicting the survival of patients with early HCC after liver resection or liver transplantation. Other major HCC staging systems perform poorly in patients with early HCC.

Performance evaluation of two-stage fuel cycle from SFR to PWR

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

Fei, T.; Hoffman, E.A.; Kim, T.K.

2013-07-01

One potential fuel cycle option being considered is a two-stage fuel cycle system involving the continuous recycle of transuranics in a fast reactor and the use of bred plutonium in a thermal reactor. The first stage is a Sodium-cooled Fast Reactor (SFR) fuel cycle with metallic U-TRU-Zr fuel. The SFRs need to have a breeding ratio greater than 1.0 in order to produce fissile material for use in the second stage. The second stage is a PWR fuel cycle with uranium and plutonium mixed oxide fuel based on the design and performance of the current state-of-the-art commercial PWRs with anmore » average discharge burnup of 50 MWd/kgHM. This paper evaluates the possibility of this fuel cycle option and discusses its fuel cycle performance characteristics. The study focuses on an equilibrium stage of the fuel cycle. Results indicate that, in order to avoid a positive coolant void reactivity feedback in the stage-2 PWR, the reactor requires high quality of plutonium from the first stage and minor actinides in the discharge fuel of the PWR needs to be separated and sent back to the stage-1 SFR. The electricity-sharing ratio between the 2 stages is 87.0% (SFR) to 13.0% (PWR) for a TRU inventory ratio (the mass of TRU in the discharge fuel divided by the mass of TRU in the fresh fuel) of 1.06. A sensitivity study indicated that by increasing the TRU inventory ratio to 1.13, The electricity generation fraction of stage-2 PWR is increased to 28.9%. The two-stage fuel cycle system considered in this study was found to provide a high uranium utilization (>80%). (authors)« less

In-hospital mortality for children with hypoplastic left heart syndrome after stage I surgical palliation: teaching versus nonteaching hospitals.

PubMed

Berry, Jay G; Cowley, Collin G; Hoff, Charles J; Srivastava, Rajendu

2006-04-01

Teaching hospitals are perceived to provide a higher quality of care for the treatment of rare disease and complex patients. A substantial proportion of stage I palliation for hypoplastic left heart syndrome (HLHS) may be performed in nonteaching hospitals. This study compares the in-hospital mortality of stage I palliation between teaching and nonteaching hospitals. The authors conducted a retrospective cohort study using the Kids' Inpatient Database 1997 and 2000. Patients with HLHS undergoing stage I palliation were identified using International Classification of Diseases, Ninth Revision, Clinical Modification diagnostic and procedural codes. Seven hundred fifty-four and 880 discharges of children with HLHS undergoing stage I palliation in 1997 and 2000, respectively, were identified. The in-hospital mortality for the study population was 28% in 1997 and 24% in 2000. Twenty percent of stage I palliation operations were performed in nonteaching hospitals in 1997. Two percent of operations were performed in nonteaching hospitals in 2000. In 1997 only, in-hospital mortality remained higher in nonteaching hospitals after controlling for stage I palliation hospital volume and condition-severity diagnoses. Low-volume hospitals performing stage I palliation were associated with increased in-hospital mortality in 1997 and 2000. Patients with HLHS undergoing stage I palliation in nonteaching hospitals experienced increased in-hospital mortality in 1997. A significant reduction in the number of stage I palliation procedures performed in nonteaching hospitals occurred between 1997 and 2000. This centralization of stage I palliation into teaching hospitals, along with advances in postoperative medical and surgical care for these children, was associated with a decrease in mortality. Patients in low-volume hospitals performing stage I palliation continued to experience increased mortality in 2000.

Design study for a staged Very Large Hadron Collider

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

Peter J. Limon et al.

Advancing accelerator designs and technology to achieve the highest energies has enabled remarkable discoveries in particle physics. This report presents the results of a design study for a new collider at Fermilab that will create exceptional opportunities for particle physics--a two-stage very large hadron collider. In its first stage, the machine provides a facility for energy-frontier particle physics research, at an affordable cost and on a reasonable time scale. In a second-stage upgrade in the same tunnel, the VLHC offers the possibility of reaching 100 times the collision energy of the Tevatron. The existing Fermilab accelerator complex serves as themore » injector, and the collision halls are on the Fermilab site. The Stage-1 VLHC reaches a collision energy of 40 TeV and a luminosity comparable to that of the LHC, using robust superferric magnets of elegant simplicity housed in a large-circumference tunnel. The Stage-2 VLHC, constructed after the scientific potential of the first stage has been fully realized, reaches a collision energy of at least 175 TeV with the installation of high-field magnets in the same tunnel. It makes optimal use of the infrastructure developed for the Stage-1 machine, using the Stage-1 accelerator itself as the injector. The goals of this study, commissioned by the Fermilab Director in November 2000, are: to create reasonable designs for the Stage-1 and Stage-2 VLHC in the same tunnel; to discover the technical challenges and potential impediments to building such a facility at Fermilab; to determine the approximate costs of the major elements of the Stage-1 VLHC; and to identify areas requiring significant R and D to establish the basis for the design.« less

Surgical management and outcome of locoregional neuroblastoma: comparison of the Childrens Cancer Group and the international staging systems.

PubMed

Haase, G M; Atkinson, J B; Stram, D O; Lukens, J N; Matthay, K K

1995-02-01

Although precise anatomic staging is prognostically important in neuroblastoma, most widely employed staging systems remain incompatible. The International Neuroblastoma Staging System (INSS) was formulated to incorporate the basic elements of several systems to and define the significance of tumor resectability, anatomic "midline," and lymph node involvement. The authors sought to determine the applicability and value of the INSS compared with the classic Evans system. Between 1980 and 1992, 424 children with the diagnosis of local or regional neuroblastoma were entered in Childrens Cancer Group (CCG) clinical trials. The patients were assigned to Evans stage I, II, or III, by clinical and surgicopathologic assessment, and were treated uniformly by Group-wide therapy protocols. INSS stage 1, 2A, 2B, or 3, was applied, by retrospective analysis, to the children in the earlier studies, and by prospective evaluation of recent patients in the current studies. Survival and relapse-free survival (RFS) rates were determined and compared, based on age at diagnosis, extent of resection, and staging reassignment. All 87 Evans stage I patients were classified as INSS stage 1 and had a 92% 3-year RFS rate. Of the 144 Evans stage II patients, 65 also qualified as INSS stage 1 patients, with an 82% RFS rate. The other 79 stage II children remained in INSS stage 2A or 2B and had a 70% RFS rate (P = .10). Of the 193 Evans stage III patients, 24 were reassigned to INSS stage 1 (85% RFS rate) and 33 to stage 2A or 2B (65% survival rate; 61% RFS rate).(ABSTRACT TRUNCATED AT 250 WORDS)

Thoroughness of Mediastinal Staging in Stage IIIA Non-Small Cell Lung Cancer

PubMed Central

Vest, Michael T.; Tanoue, Lynn; Soulos, Pamela R.; Kim, Anthony W.; Detterbeck, Frank; Morgensztern, Daniel; Gross, Cary P.

2011-01-01

Introduction Guidelines recommend that patients with clinical stage IIIA non-small cell lung cancer (NSCLC) undergo histologic confirmation of pathologic lymph nodes. Studies have suggested that invasive mediastinal staging is underutilized, though practice patterns have not been rigorously evaluated. Methods We used the Surveillance, Epidemiology, and End Results-Medicare database to identify patients with stage IIIA NSCLC diagnosed from 1998 through 2005. Invasive staging and use of positron emission tomography (PET) scanning were assessed using Medicare claims. Multivariable logistic regression was used to identify patient characteristics associated with use of invasive staging. Results Of 7583 stage IIIA NSCLC patients, 1678 (22%) underwent invasive staging. Patients who received curative intent cancer treatment were more likely to undergo invasive staging than patients who did not receive cancer specific therapy (30% vs. 9.8%, adjusted odds ratio [OR} 3.31, 95% CI 2.78–3.95). The oldest patients (age 85–94) were less likely to receive invasive staging than the youngest ((age 67–69) (27.6 % vs. 11.9%, OR 0.46, 95% CI 0.34–0.61)). Sex, marital status, income and race were not associated with the use of the invasive staging. The use of invasive staging was stable throughout the study period, despite an increase in the use of PET scanning from less than 10% of patients prior to 2000 to almost 70% in 2005. Conclusion Nearly 80% of Medicare beneficiaries with stage IIIA NSCLC do not receive guideline adherent mediastinal staging; this failure cannot be entirely explained by patient factors or a reliance on PET imaging. Incentives to encourage use of invasive staging may improve care. PMID:22134069

Treatment Patterns and Health Resource Utilization Among Patients Diagnosed With Early Stage Resected Non-Small Cell Lung Cancer at US Community Oncology Practices.

PubMed

Buck, Philip O; Saverno, Kimberly R; Miller, Paul J E; Arondekar, Bhakti; Walker, Mark S

2015-11-01

Data on adjuvant therapy in resected non-small cell lung cancer (NSCLC) in routine practice are lacking in the United States. This retrospective observational database study included 609 community oncology patients with resected stage IB to IIIA NSCLC. Use of adjuvant therapy was 39.1% at disease stage IB and 64.9% to 68.2% at stage II to IIIA. The most common regimen at all stages was carboplatin and paclitaxel. Platin-based adjuvant chemotherapy has extended survival in clinical trials in patients with completely resected non-small cell lung cancer (NSCLC). There are few data on the use of adjuvant therapy in community-based clinical practice in the United States. This was a retrospective observational study using electronic medical record and billing data collected during routine care at US community oncology sites in the Vector Oncology Data Warehouse between January 2007 and January 2014. Patients aged ≥ 18 years with a primary diagnosis of stage IB to IIIA NSCLC were eligible if they had undergone surgical resection. Treatment patterns, health care resource use, and cost were recorded, stratified by stage at diagnosis. The study included 609 patients (mean age, 64.8 years, 52.9% male), of whom 215 had stage IB disease, 130 stage IIA/II, 110 stage IIB, and 154 stage IIIA. Adjuvant systemic therapy after resection was provided to 345 (56.7%) of 609 patients, with lower use in patients with stage IB disease (39.1%) than stage II to IIIA disease (64.9-68.2%) (P < .0001). The most common adjuvant regimen at all stages was the combination of carboplatin and paclitaxel. There were no statistically significant differences in office visits or incidence of hospitalization by disease stage. During adjuvant treatment, the total monthly median cost per patient was $17,389.75 (interquartile range, $8,815.61 to $23,360.85). Adjuvant systemic therapy was used in some patients with stage IB NSCLC and in the majority of patients with stage IIA to IIIA disease. There were few differences in regimen or health care resource use by disease stage. Copyright © 2015 The Authors. Published by Elsevier Inc. All rights reserved.

Relationship of psychological factors with physical activity stage of change in prime-and middle-aged Japanese.

PubMed

Mori, Keiko; Suzuki, Hisao; Wang, Da-Hong; Takaki, Jiro; Takigawa, Tomoko; Ogino, Keiki

2009-04-01

The present study aimed to investigate the status of physical activity and the differences in psychological factors associated with physical activity from the perspective of transtheoretical model stages between prime- and middle-aged Japanese. The study involved 375 prime-aged volunteers (175 men, 200 women) and 557 middle-aged volunteers (247 men, 310 women) living in Kuse, a town in Okayama Prefecture, Japan. We found that the prime-aged men at the preparation stage had significantly higher self-efficacy scores than at the contemplation stage (p<0.01). Middle-aged men had significantly higher self-efficacy scores at the contemplation stage than at the precontemplation stage (p<0.001). Middle-aged women, meanwhile, had significantly higher self-efficacy scores at the maintenance stage than at the action stage (p<0.01), and at the contemplation stage than at the precontemplation stage (p<0.001). The present findings provide valuable information about the differences in psychological factors affecting physical activity between prime-aged and middle-aged community-dwelling Japanese. This information may be useful to health professionals as they develop effective community-based intervention programs for target populations.

Emergency skill training--a randomized controlled study on the effectiveness of the 4-stage approach compared to traditional clinical teaching.

PubMed

Greif, Robert; Egger, Lars; Basciani, Reto M; Lockey, Andrew; Vogt, Andreas

2010-12-01

The "4-stage approach" has been widely accepted for practical skill training replacing the traditional 2 stages ("see one, do one"). However, the superior effectiveness of the 4-stage approach was never proved. To evaluate whether skill training with the 4-stage approach results in shorter performance time needed for a successful percutaneous needle-puncture cricothyroidotomy, and consequently in a reduced number of attempts needed to perform the skill in <60s compared to traditional teaching. Randomized controlled single-blinded parallel group study at the University Hospital Bern. With IRB approval and informed consent 128 undergraduate medical students were randomized in four groups: traditional teaching, no stage 2, no stage 3, and 4-stage approach for the training of cricothyroidotomy. Everyone watched a video of the cricothyroidotomy as stage 1 followed by skill training in the respective teaching group. Participants had to perform the cricothyroidotomy 10 times on skin-covered pig larynxes. Performance time was measured from skin palpation to trachea ventilation. Study participants filled out a self-rating on competency during the training. Performance time for each attempt was comparable in all groups and improved similarly to reach a performance time of <60 s. Self-rating revealed that all groups felt equally competent throughout. Even if the 4-stage approach is widely accepted and used as a didactic method for skill teaching we could not find evidence that its use or omitting stage 2 or 3 results in superior learning of an emergency skill compared to traditional teaching. Copyright © 2010 Elsevier Ireland Ltd. All rights reserved.

Gene expression profiles in stage I uterine serous carcinoma in comparison to grade 3 and grade 1 stage I endometrioid adenocarcinoma.

PubMed

Mhawech-Fauceglia, Paulette; Wang, Dan; Kesterson, Joshua; Syriac, Susanna; Clark, Kimberly; Frederick, Peter J; Lele, Shashikant; Liu, Song

2011-03-23

Endometrial cancer is the most common gynecologic malignancy in the developed countries. Clinical studies have shown that early stage uterine serous carcinoma (USC) has outcomes similar to early stage high grade endometrioid adenocarcinoma (EAC-G3) than to early stage low grade endometrioid adenocarcinoma (EAC-G1). However, little is known about the origin of these different clinical outcomes. This study applied the whole genome expression profiling to explore the expression difference of stage I USC (n = 11) relative to stage I EAC-G3 (n = 11) and stage I EAC-G1 (n = 11), respectively. We found that the expression difference between USC and EAC-G3, as measured by the number of differentially expressed genes (DEGs), is consistently less than that found between USC and EAC-G1. Pathway enrichment analyses suggested that DEGs specific to USC vs. EAC-G3 are enriched for genes involved in signaling transduction, while DEGs specific to USC vs. EAC-G1 are enriched for genes involved in cell cycle. Gene expression differences for selected DEGs are confirmed by quantitative RT-PCR with a high validation rate. This data, although preliminary, indicates that stage I USC is genetically similar to stage I EAC-G3 compared to stage I EAC-G1. DEGs identified from this study might provide an insight in to the potential mechanisms that influence the clinical outcome differences between endometrial cancer subtypes. They might also have potential prognostic and therapeutic impacts on patients diagnosed with uterine cancer.

Preoperative high-resolution magnetic resonance imaging can identify good prognosis stage I, II, and III rectal cancer best managed by surgery alone: a prospective, multicenter, European study.

PubMed

Taylor, Fiona G M; Quirke, Philip; Heald, Richard J; Moran, Brendan; Blomqvist, Lennart; Swift, Ian; Sebag-Montefiore, David J; Tekkis, Paris; Brown, Gina

2011-04-01

To assess local recurrence, disease-free survival, and overall survival in magnetic resonance imaging (MRI)-predicted good prognosis tumors treated by surgery alone. The MERCURY study reported that high-resolution MRI can accurately stage rectal cancer. The routine policy in most centers involved in the MERCURY study was primary surgery alone in MRI-predicted stage II or less and in MRI "good prognosis" stage III with selective avoidance of neoadjuvant therapy. Data were collected prospectively on all patients included in the MERCURY study who were staged as MRI-defined "good" prognosis tumors. "Good" prognosis included MRI-predicted safe circumferential resection margins, with MRI-predicted T2/T3a/T3b (less than 5 mm spread from muscularis propria), regardless of MRI N stage. None received preoperative or postoperative radiotherapy. Overall survival, disease-free survival, and local recurrence were calculated. Of 374 patients followed up in the MERCURY study, 122 (33%) were defined as "good prognosis" stage III or less on MRI. Overall and disease-free survival for all patients with MRI "good prognosis" stage I, II and III disease at 5 years was 68% and 85%, respectively. The local recurrence rate for this series of patients predicted to have a good prognosis tumor on MRI was 3%. The preoperative identification of good prognosis tumors using MRI will allow stratification of patients and better targeting of preoperative therapy. This study confirms the ability of MRI to select patients who are likely to have a good outcome with primary surgery alone.

Tooth mineralization stages as a diagnostic tool for assessment of skeletal maturity.

PubMed

Surendran, Sharmila; Thomas, Eapen

2014-01-01

The objective of this study was to determine whether dental calcification can be used as a first-level diagnostic tool for assessment of skeletal maturity. A total of 150 healthy subjects (79 boys, 71 girls; mean age, 12.19 ± 2.03 years; range, 8-16 years) were enrolled in the study. Dental maturity was assessed through the calcification stages from panoramic radiographs of the mandibular canine, the first and second premolars, and the second molar. Determination of skeletal maturity was according to the modified middle phalanx of third finger (MP3) stages method on digital radiographs. Diagnostic ability was evaluated according to the dental maturation stages for each tooth for identification of the MP3 stages and the growth phases (prepubertal, pubertal, postpubertal) using positive likelihood ratios. Dental maturation stage E of the first premolars and the combination of canine stage F, first premolar stage E, second premolar stage E, and second molar stage D (FEED) gave the highest values for identification of the prepubertal growth phase, and stage H of the second molar had the highest value for identification of the postpubertal growth phase. Dental maturation assessment is only useful for diagnosis of the prepubertal and postpubertal growth phases. Copyright © 2014 American Association of Orthodontists. Published by Mosby, Inc. All rights reserved.

Do hospital treatments represent a 'teachable moment' for quitting smoking? A study from a stage-theoretical perspective.

PubMed

Dohnke, B; Ziemann, C; Will, K E; Weiss-Gerlach, E; Spies, C D

2012-01-01

Hospital treatments are assumed to be a 'teachable moment'. This phenomenon, however, is only poorly conceptualised and untested. A stage-theoretical perspective implies that a cueing event such as hospital treatments is a teachable moment if a stage progression, change of cognitions, or both occur. This concept is examined in a cross-sectional study by comparing smokers in two treatment settings, an emergency department (ED) and inpatient treatment after elective surgery, with smokers in a control setting. Setting differences were hypothesised in stage distribution, and levels of and stage differences in social-cognitive factors under control for possible confounders. Stage, social-cognitive factors and possible confounders were assessed in 185 ED smokers, 193 inpatient smokers and 290 control smokers. Compared to control smokers, ED and inpatient smokers were in higher stages; they perceived fewer risks and cons; inpatient smokers reported more concrete plans. Stage differences in self-efficacy among ED and inpatient smokers differed from those among control smokers, but the former corresponded more strongly to the theoretical stage assumptions. The results suggest that hospital treatments lead to a stage progression and change of corresponding cognitions, and thus represent a 'teachable moment'. Stage-matched interventions should be provided but consider differences in cognitions to be effective.

Performances of single and two-stage pulse tube cryocoolers under different vacuum levels with and without thermal radiation shields

NASA Astrophysics Data System (ADS)

Kasthurirengan, Srinivasan; Behera, Upendra; Nadig, D. S.; Krishnamoorthy, V.

2012-06-01

Single and two-stage Pulse Tube Cryocoolers (PTC) have been designed, fabricated and experimentally studied. The single stage PTC reaches a no-load temperature of ~ 29 K at its cold end, the two-stage PTC reaches ~ 2.9 K in its second stage cold end and ~ 60 K in its first stage cold end. The two-stage Pulse Tube Cryocooler provides a cooling power of ~ 250 mW at 4.2 K. The single stage system uses stainless steel meshes along with Pb granules as its regenerator materials, while the two-stage PTC uses combinations of Pb along with Er3Ni / HoCu2 as the second stage regenerator materials. Normally, the above systems are insulated by thermal radiation shields and mounted inside a vacuum chamber which is maintained at high vacuum. To evaluate the performance of these systems in the possible conditions of loss of vacuum with and without radiation shields, experimental studies have been performed. The heat-in-leak under such severe conditions has been estimated from the heat load characteristics of the respective stages. The experimental results are analyzed to obtain surface emissivities and effective thermal conductivities as a function of interspace pressure.

Applying NGS Data to Find Evolutionary Network Biomarkers from the Early and Late Stages of Hepatocellular Carcinoma

PubMed Central

Wu, Chia-Chou; Lin, Chih-Lung; Chen, Ting-Shou

2015-01-01

Hepatocellular carcinoma (HCC) is a major liver tumor (~80%), besides hepatoblastomas, angiosarcomas, and cholangiocarcinomas. In this study, we used a systems biology approach to construct protein-protein interaction networks (PPINs) for early-stage and late-stage liver cancer. By comparing the networks of these two stages, we found that the two networks showed some common mechanisms and some significantly different mechanisms. To obtain differential network structures between cancer and noncancer PPINs, we constructed cancer PPIN and noncancer PPIN network structures for the two stages of liver cancer by systems biology method using NGS data from cancer cells and adjacent noncancer cells. Using carcinogenesis relevance values (CRVs), we identified 43 and 80 significant proteins and their PPINs (network markers) for early-stage and late-stage liver cancer. To investigate the evolution of network biomarkers in the carcinogenesis process, a primary pathway analysis showed that common pathways of the early and late stages were those related to ordinary cancer mechanisms. A pathway specific to the early stage was the mismatch repair pathway, while pathways specific to the late stage were the spliceosome pathway, lysine degradation pathway, and progesterone-mediated oocyte maturation pathway. This study provides a new direction for cancer-targeted therapies at different stages. PMID:26366411

Gifted' Teachers Stages of Concerns for Integrating E-Learning in the Gifted Schools in Jordan

ERIC Educational Resources Information Center

Al-Shabatat, Ahmad Mohammad

2014-01-01

No study has investigated the gifted' teachers stages of concerns for integrating e-learning in their teaching. Thus, this study was conducted to explore these concerns. Mixed methods were used to gather data around the research questions. A number of 22 gifted' teachers participated in this study. The Arabic version of the Stage of Concern…

The Mainstream Problems Coping Students with Hearing Disability in Najran Region

ERIC Educational Resources Information Center

Saleem, Suhib Saleem

2017-01-01

This study aimed to explore the problems facing the students with hearing disability in Najran region based on gender, study stage, and type of disability. The sample of the study consisted of 17 males, 13 females, 16 students with hearing disability in the intermediate stage, and 14 students in the secondary stage in public schools. While the…

It Is Only a Stage They Are Going Through: The Development of Student Teachers.

ERIC Educational Resources Information Center

Piland, Diane E.; Anglin, Jacqueline M.

1993-01-01

Describes student teachers' developmental stages. After reviewing pertinent literature, the paper examines a recent study that qualitatively and quantitatively outlined stages of development applicable to contemporary student teaching contexts. The study found that each of five student teachers passed through four developmental stages…

Spectral characteristics of caries-related autofluorescence spectra and their use for diagnosis of caries stage

NASA Astrophysics Data System (ADS)

Son, Sung-Ae; Jung, Kyeong-Hoon; Ko, Ching-Chang; Kwon, Yong Hoon

2016-01-01

The purpose of the present study was to identify factors useful for diagnosis of the caries stage from laser-induced autofluorescence (AF) spectra. Affected teeth were accurately staged and allocated to four groups: sound, stage II, stage III, or stage IV. A 405-nm laser was used to produce AF spectra. The spectrum factors analyzed were spectrum slope at 550 to 600 nm, spectral area from 500 and 590 nm, and intensity ratio of peaks 625 and 667 nm (625/667 nm). DIAGNOdent was used as control measurement. AF spectra of sound teeth had a peak near 500 nm followed by a smooth decline to 800 nm. As caries progressed, some specimens in stages II to IV showed one or two peak(s) near 625 and 667 nm. Slopes at 550 to 600 nm and areas under the curve at 500 to 590 nm were significantly different (p<0.001) for each stage. Two-peak ratios were also significantly different (p<0.001) except for stage III and stage IV. DIAGNOdent readings for sound and stage II and stage III and IV were not significantly different. Among the studied factors, the spectrum slope at 550 to 600 nm and area under curve at 500 to 590 nm could be useful treatment decision-making tools for carious lesions.

Analysing growth and development of plants jointly using developmental growth stages.

PubMed

Dambreville, Anaëlle; Lauri, Pierre-Éric; Normand, Frédéric; Guédon, Yann

2015-01-01

Plant growth, the increase of organ dimensions over time, and development, the change in plant structure, are often studied as two separate processes. However, there is structural and functional evidence that these two processes are strongly related. The aim of this study was to investigate the co-ordination between growth and development using mango trees, which have well-defined developmental stages. Developmental stages, determined in an expert way, and organ sizes, determined from objective measurements, were collected during the vegetative growth and flowering phases of two cultivars of mango, Mangifera indica. For a given cultivar and growth unit type (either vegetative or flowering), a multistage model based on absolute growth rate sequences deduced from the measurements was first built, and then growth stages deduced from the model were compared with developmental stages. Strong matches were obtained between growth stages and developmental stages, leading to a consistent definition of integrative developmental growth stages. The growth stages highlighted growth asynchronisms between two topologically connected organs, namely the vegetative axis and its leaves. Integrative developmental growth stages emphasize that developmental stages are closely related to organ growth rates. The results are discussed in terms of the possible physiological processes underlying these stages, including plant hydraulics, biomechanics and carbohydrate partitioning. © The Author 2014. Published by Oxford University Press on behalf of the Annals of Botany Company. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Tough Adults, Frail Babies: An Analysis of Stress Sensitivity across Early Life-History Stages of Widely Introduced Marine Invertebrates

PubMed Central

Pineda, M. Carmen; McQuaid, Christopher D.; Turon, Xavier; López-Legentil, Susanna; Ordóñez, Víctor; Rius, Marc

2012-01-01

All ontogenetic stages of a life cycle are exposed to environmental conditions so that population persistence depends on the performance of both adults and offspring. Most studies analysing the influence of abiotic conditions on species performance have focussed on adults, while studies covering early life-history stages remain rare. We investigated the responses of early stages of two widely introduced ascidians, Styela plicata and Microcosmus squamiger, to different abiotic conditions. Stressors mimicked conditions in the habitats where both species can be found in their distributional ranges and responses were related to the selection potential of their populations by analysing their genetic diversity. Four developmental stages (egg fertilisation, larval development, settlement, metamorphosis) were studied after exposure to high temperature (30°C), low salinities (26 and 22‰) and high copper concentrations (25, 50 and 100 µg/L). Although most stressors effectively led to failure of complete development (fertilisation through metamorphosis), fertilisation and larval development were the most sensitive stages. All the studied stressors affected the development of both species, though responses differed with stage and stressor. S. plicata was overall more resistant to copper, and some stages of M. squamiger to low salinities. No relationship was found between parental genetic composition and responses to stressors. We conclude that successful development can be prevented at several life-history stages, and therefore, it is essential to consider multiple stages when assessing species' abilities to tolerate stress. Moreover, we found that early development of these species cannot be completed under conditions prevailing where adults live. These populations must therefore recruit from elsewhere or reproduce during temporal windows of more benign conditions. Alternatively, novel strategies or behaviours that increase overall reproductive success might be responsible for ensuring population survival. PMID:23077518

The Prevalence of Stages of Heart Failure in Primary Care: A Population-Based Study.

PubMed

Jorge, Antonio Lagoeiro; Rosa, Maria Luiza G; Martins, Wolney A; Correia, Dayse Mary S; Fernandes, Luiz Claudio M; Costa, Jean A; Moscavitch, Samuel D; Jorge, Bruno Afonso L; Mesquita, Evandro T

2016-02-01

Planning strategies to prevent heart failure (HF) in developing countries require epidemiologic data in primary care. The purpose of this study was to estimate the prevalence of HF stages and their phenotypes, HF with preserved ejection fraction (HFPEF), and HF with reduced EF (HFREF) and to determine B-type natriuretic peptide (BNP) levels to identify HF in the adult population. This is a cross-sectional study including 633 individuals, aged ≥45 years, who were randomly selected and registered in a primary care program of a medium-sized city in Brazil. All participants were underwent clinical evaluations, BNP measurements, electrocardiograms, and tissue Doppler echocardiography in a single day. The participants were classified as stage 0 (healthy, 11.7%), stage A (risk factors, 36.6%), stage B (structural abnormalities, 42.7%), or stage C (symptomatic HF, 9.3%). Among patients with HF, 59% presented with HFPEF and 41% presented with HFREF. The mean BNP levels were 20 pg/mL(-1) in stage 0, 20 pg/mL(-1) in stage A, 24 pg/mL(-1) in stage B, 93 pg/mL(-1) in HFPEF, and 266 pg/mL(-1) in HFREF. The cutoff BNP level with optimal sensitivity (92%) and specificity (91%) to identify HF was 42 pg/mL(-1). The present study demonstrated a high prevalence of individuals at risk for HF and the predominance of HFPEF in a primary care setting. The clinical examination, along with BNP and tissue Doppler echocardiography, may facilitate early detection of stages A and B HF and allow implementation of interventions aimed at preventing progression to symptomatic HF. Copyright © 2015 Elsevier Inc. All rights reserved.

Controlling the COD removal of an A-stage pilot study with instrumentation and automatic process control.

PubMed

Miller, Mark W; Elliott, Matt; DeArmond, Jon; Kinyua, Maureen; Wett, Bernhard; Murthy, Sudhir; Bott, Charles B

2017-06-01

The pursuit of fully autotrophic nitrogen removal via the anaerobic ammonium oxidation (anammox) pathway has led to an increased interest in carbon removal technologies, particularly the A-stage of the adsorption/bio-oxidation (A/B) process. The high-rate operation of the A-stage and lack of automatic process control often results in wide variations of chemical oxygen demand (COD) removal that can ultimately impact nitrogen removal in the downstream B-stage process. This study evaluated the use dissolved oxygen (DO) and mixed liquor suspended solids (MLSS) based automatic control strategies through the use of in situ on-line sensors in the A-stage of an A/B pilot study. The objective of using these control strategies was to reduce the variability of COD removal by the A-stage and thus the variability of the effluent C/N. The use of cascade DO control in the A-stage did not impact COD removal at the conditions tested in this study, likely because the bulk DO concentration (>0.5 mg/L) was maintained above the half saturation coefficient of heterotrophic organisms for DO. MLSS-based solids retention time (SRT) control, where MLSS was used as a surrogate for SRT, did not significantly reduce the effluent C/N variability but it was able to reduce COD removal variation in the A-stage by 90%.

Optimization of multi-stage dynamic treatment regimes utilizing accumulated data.

PubMed

Huang, Xuelin; Choi, Sangbum; Wang, Lu; Thall, Peter F

2015-11-20

In medical therapies involving multiple stages, a physician's choice of a subject's treatment at each stage depends on the subject's history of previous treatments and outcomes. The sequence of decisions is known as a dynamic treatment regime or treatment policy. We consider dynamic treatment regimes in settings where each subject's final outcome can be defined as the sum of longitudinally observed values, each corresponding to a stage of the regime. Q-learning, which is a backward induction method, is used to first optimize the last stage treatment then sequentially optimize each previous stage treatment until the first stage treatment is optimized. During this process, model-based expectations of outcomes of late stages are used in the optimization of earlier stages. When the outcome models are misspecified, bias can accumulate from stage to stage and become severe, especially when the number of treatment stages is large. We demonstrate that a modification of standard Q-learning can help reduce the accumulated bias. We provide a computational algorithm, estimators, and closed-form variance formulas. Simulation studies show that the modified Q-learning method has a higher probability of identifying the optimal treatment regime even in settings with misspecified models for outcomes. It is applied to identify optimal treatment regimes in a study for advanced prostate cancer and to estimate and compare the final mean rewards of all the possible discrete two-stage treatment sequences. Copyright © 2015 John Wiley & Sons, Ltd.

Comparison of T stage, N stage, multifocality, and bilaterality in papillary thyroid carcinoma patients according to the presence of coexisting lymphocytic thyroiditis.

PubMed

Park, Jin Young; Kim, Dong Wook; Park, Ha Kyung; Ha, Tae Kwun; Jung, Soo Jin; Kim, Do Hun; Bae, Sang Kyun

2015-01-01

This study aimed to assess the relationship between coexisting lymphocytic thyroiditis and T-N stages of papillary thyroid carcinoma (PTC) by histopathological analysis. The study included 653 patients who underwent thyroid surgery for PTC at our hospital. Each case was classified as either Hashimoto's thyroiditis (HT), non-Hashimoto type of lymphocytic thyroiditis (NHLT), or normal according to the histopathology of thyroid parenchyma. Patient age, gender, surgical modality, location, T stage, N stage, multifocality and bilaterality were compared according to the histopathology. The prevalence of coexisting lymphocytic thyroiditis was 25.8% (169/653); HT (7.5%, 49/653) and NHLT (18.3%, 120/653). There were no significant differences in T stage, N stage, multifocality and bilaterality with regard to coexisting lymphocytic thyroiditis, regardless of whether HT and NHLT were considered collectively or discretely. Primary tumor size (p < 0.0001), location (p = 0.0011), N stage (p < 0.0001), multifocality (p < 0.0001) and bilaterality (p < 0.0001) differed significantly according to T stage, and gender (p = 0.0193), primary tumor size (p < 0.0001), T stage (p < 0.0001), multifocality (p < 0.0001) and bilaterality (p < 0.0001) differed significantly according to N stage. PTC patients with coexisting lymphocytic thyroiditis did not differ from those with normal parenchyma in terms of T stage, N stage, multifocality and bilaterality.

Relationship between dental calcification and skeletal maturation in a Peruvian sample

PubMed Central

Lecca-Morales, Rocío M.; Carruitero, Marcos J.

2017-01-01

ABSTRACT Objective: the objective of the study was to determine the relationship between dental calcification stages and skeletal maturation in a Peruvian sample. Methods: panoramic, cephalometric and carpal radiographs of 78 patients (34 girls and 44 boys) between 7 and 17 years old (9.90 ± 2.5 years) were evaluated. Stages of tooth calcification of the mandibular canine, first premolar, second premolar, and second molar and the skeletal maturation with a hand-wrist and a cervical vertebrae method were assessed. The relationships between the stages were assessed using Spearman’s correlation coefficient. Additionally, the associations of mandibular and pubertal growth peak stages with tooth calcification were evaluated by Fisher’s exact test. Results: all teeth showed positive and statistically significant correlations, the highest correlation was between the mandibular second molar calcification stages with hand-wrist maturation stages (r = 0.758, p < 0.001) and with vertebrae cervical maturation stages (r = 0.605, p < 0.001). The pubertal growth spurt was found in the G stage of calcification of the second mandibular molar, and the mandibular growth peak was found in the F stage of calcification of the second molar. Conclusion: there was a positive relationship between dental calcification stages and skeletal maturation stages by hand-wrist and cervical vertebrae methods in the sample studied. Dental calcification stages of the second mandibular molar showed the highest positive correlation with the hand-wrist and cervical vertebrae stages. PMID:28746492

Sinonasal mucosal melanoma: retrospective survival study of 25 patients.

PubMed

Vandenhende, C; Leroy, X; Chevalier, D; Mortuaire, G

2012-02-01

To determine potential prognostic factors for survival in patients with mucosal malignant melanoma of the sinonasal tract. Patients managed between 1991 and 2008 were assessed retrospectively. The seventh edition Union for International Cancer Control (7th UICC) tumour-node-metastasis classification was used for tumour staging. Kaplan-Meier and log rank tests were used for survival analysis. Twenty-five patients were studied (six were tumour stage three, eight tumour stage four(a) and 11 tumour stage four(b)). Surgery was performed on 23 patients (92 per cent). Fifteen received post-operative radiotherapy. Mean follow up was 31.3 months (range, two to 99 months). Three-year disease-free survival was improved in patients with stage four tumour arising from the nasal fossa, versus other sites, and in those with stage four tumour treated with surgery plus adjuvant radiotherapy, versus other treatments. Patients with melanoma of the nasal cavity have very poor survival rates. Treatment is still based on adequate surgical resection with safe margins. In this study, post-operative radiotherapy improved local control only for stage four tumours.

Topographic mapping of electroencephalography coherence in hypnagogic state.

PubMed

Tanaka, H; Hayashi, M; Hori, T

1998-04-01

The present study examined the topographic characteristics of hypnagogic electroencephalography (EEG), using topographic mapping of EEG power and coherence corresponding to nine EEG stages (Hori's hypnagogic EEG stages). EEG stages 1 and 2, the EEG stages 3-8, and the EEG stage 9 each correspond with standard sleep stage W, 1 and 2, respectively. The dominant topographic components of delta and theta activities increased clearly from the vertex sharp-wave stage (the EEG stages 6 and 7) in the anterior-central areas. The dominant topographic component of alpha 3 activities increased clearly from the EEG stage 9 in the anterior-central areas. The dominant topographic component of sigma activities increased clearly from the EEG stage 8 in the central-parietal area. These results suggested basic sleep process might start before the onset of sleep stage 2 or of the manually scored spindles.

Morphogenesis of the human excretory lacrimal system

PubMed Central

de la Cuadra-Blanco, C; Peces-Peña, M D; Jáñez-Escalada, L; Mérida-Velasco, J R

2006-01-01

The aim of this study was to determine the principal developmental stages in the formation of the excretory lacrimal system in humans and to establish its morphogenetic period. The study was performed using light microscopy on serial sections of 51 human specimens: 33 embryos and 18 fetuses ranging from 8 to 137 mm crown–rump length (CR; 5–16 weeks of development). Three stages were identified in the morphogenesis of the excretory lacrimal system: (1) the formative stage of the lacrimal lamina (Carnegie stages 16–18); (2) the formative stage of the lacrimal cord (Carnegie stages 19–23); and (3) the maturative stage of the excretory lacrimal system, from the 9th week of development onward. A three-dimensional reconstruction of the excretory lacrimal system was performed from serial sections of an embryo at the end of the embryonic period (27 mm CR). PMID:16879594

New insights into membrane fouling in submerged MBR under sub-critical flux condition.

PubMed

Li, Jianfeng; Zhang, Xiuxiu; Cheng, Fangqin; Liu, Yu

2013-06-01

This study investigated the membrane fouling in MBRs under sub-critical flux condition. Results showed membrane fouling at subcritical flux evolved through a three-stage process: a slow linear increase in transmembrane pressure (TMP) (stage I), followed by an exponential increase in TMP (stage II), and finally a rapid linear TMP rise was observed at stage III. It was found that bound EPS would play a significant role in fouling development at stage I, while SMPs appeared to be the major contributor to self-accelerating fouling phenomena observed at stage II. At stage III, the entire membrane was covered by a cake layer of flocs, as the result, the fouling rate was likely determined by floc characteristics. This study offers new insights into the fouling development under sub-critical flux condition. Copyright © 2013 Elsevier Ltd. All rights reserved.

Metagenomic Profiling of the Bacterial Community Changes from Koji to Mash Stage in the Brewing of Soy Sauce.

PubMed

Wang, Hongbin; Wei, Quanzeng; Gui, Shuqi; Feng, Yongrui; Zhang, Yong; Liu, Yihan; Lu, Fuping

2017-12-04

The improvement of soy sauce fermentation is restricted by the insufficient information on bacterial community. In this study, bacterial communities in the koji and mash stage were compared based on next-generation sequencing technology. A total of 29 genera were identified in the koji stage, while 34 in the mash stage. After koji stage, 7 genera disappeared and 12 new genera appeared in the mash stage. The dominant bacteria were Kurthia, Weissella and Staphylococcus in the koji stage and Staphylococcus, Kurthia, Enterococcus and Leuconostoc in the mash stage. The results provided insights into the microbial communities involved in soy sauce fermentation.

Assessment of Growth Using Mandibular Canine Calcification Stages and Its Correlation with Modified MP3 Stages

PubMed Central

Nayak, US Krishna; Hegde, Gautam

2010-01-01

Background and objectives Orthodontic diagnosis and treatment planning for growing children must involve growth prediction, especially in the treatment of skeletal problems. Studies have shown that a strong association exists between skeletal maturity and dental calcification stages. The present study was therefore taken up to provide a simple and practical method for assessing skeletal maturity using a dental periapical film and standard dental X-ray machine, to compare the developmental stages of the mandibular canine with that of developmental stages of modified MP3 and to find out if any correlation exists, to determine if the developmental stages of the mandibular canine alone can be used as a reliable indicator for assessment of skeletal maturity. Methods A total of 160 periapical radiographs (80 males and 80 females), of the mandibular right canine and the MP3 region was taken and assessed according to the Dermirjian’s stages of dental calcification and the modified MP3 stages. Results The correlation between the developmental stages of MP3 and the mandibular right canine in male and female groups, is of high statistical significance (p = 0.001). The correlation coefficient between MP3 stages and developmental stages of mandibular canine and chronological age in male and females was found to be not significant. Conclusions The correlation between the mandibular canine calcification stages and MP3 stages was found to be significant. The developmental stages of the mandibular canine could be used very reliably as a sole indicator for assessment of skeletal maturity. PMID:27625553

Phase I IGART Study Using Active Breathing Control and Simultaneous Boost for Patients With NSCLC

ClinicalTrials.gov

2015-03-18

Adenocarcinoma of the Lung; Large Cell Lung Cancer; Squamous Cell Lung Cancer; Stage IIA Non-small Cell Lung Cancer; Stage IIB Non-small Cell Lung Cancer; Stage IIIA Non-small Cell Lung Cancer; Stage IIIB Non-small Cell Lung Cancer

The balance effect of acupuncture therapy among stroke patients.

PubMed

Huang, Shih-Wei; Wang, Wei-Te; Yang, Tsung-Hsien; Liou, Tsan-Hon; Chen, Guan-Yu; Lin, Li-Fong

2014-08-01

To analyze how acupuncture therapy affects balance in patients experiencing their first stroke and to identify the stroke group with greatest improvement in balance after acupuncture intervention. Retrospective case-control study. Ward of a medical university hospital. A total of 629 stroke patients were enrolled initially; 345 patients met the study criteria and 132 were analyzed (66 each in the study and control groups). The study group received physiotherapy combined with acupuncture and the control group received only physiotherapy. The Postural Assessment Scale for Stroke patients (PASS) was used to evaluate balance. This balance scale system can be subdivided into static balance (PASS-MP, maintain posture) and dynamic balance (PASS-CP, change posture). This study revealed no statistically significant improvement of balance in the study group (t test). When patients with high Brunnstrom stage (Br stage) and low Br stage were analyzed separately, once again no statistical difference was detected between the study and control groups of those with high Br stage. However, among low-Br stage patients, the study group showed significant improvement in static balance (mean PASS-MP score±standard deviation: 4.7±3.7) compared with the control group (PASS-MP score: 2.8±2.7) (p<0.05). In first-ever stroke patients with a low Br stage, acupuncture therapy can improve static balance during rehabilitation. However, the effect on balance was limited among high-Br stage patients. This study provides information valuable to patients with hemiplegic stroke because it suggests that acupuncture can be used to improve balance. A prospective double-blind, randomized, controlled study design is recommended for future studies in patients with hemiplegic stroke.

Colorectal cancer staging: comparison of whole-body PET/CT and PET/MR.

PubMed

Catalano, Onofrio A; Coutinho, Artur M; Sahani, Dushyant V; Vangel, Mark G; Gee, Michael S; Hahn, Peter F; Witzel, Thomas; Soricelli, Andrea; Salvatore, Marco; Catana, Ciprian; Mahmood, Umar; Rosen, Bruce R; Gervais, Debra

2017-04-01

Correct staging is imperative for colorectal cancer (CRC) since it influences both prognosis and management. Several imaging methods are used for this purpose, with variable performance. Positron emission tomography-magnetic resonance (PET/MR) is an innovative imaging technique recently employed for clinical application. The present study was undertaken to compare the staging accuracy of whole-body positron emission tomography-computed tomography (PET/CT) with whole-body PET/MR in patients with both newly diagnosed and treated colorectal cancer. Twenty-six patients, who underwent same day whole-body (WB) PET/CT and WB-PET/MR, were evaluated. PET/CT and PET/MR studies were interpreted by consensus by a radiologist and a nuclear medicine physician. Correlations with prior imaging and follow-up studies were used as the reference standard. Correct staging was compared between methods using McNemar's Chi square test. The two methods were in agreement and correct for 18/26 (69%) patients, and in agreement and incorrect for one patient (3.8%). PET/MR and PET/CT stages for the remaining 7/26 patients (27%) were discordant, with PET/MR staging being correct in all seven cases. PET/MR significantly outperformed PET/CT overall for accurate staging (P = 0.02). PET/MR outperformed PET/CT in CRC staging. PET/MR might allow accurate local and distant staging of CRC patients during both at the time of diagnosis and during follow-up.

Morphological study on the pressure ulcer-like dermal lesions formed in the rat heel skin after transection of the sciatic nerves.

PubMed

Haba, Daijiro; Minami, Chie; Miyagawa, Miki; Arakawa, Takamitsu; Miki, Akinori

2017-01-01

Due to transection of bilateral sciatic nerves, pressure ulcer-like dermal lesion occurred in the hairy skin covering of the heel skin in almost all rats. In the present study, chronological changes of the rat heel skin after the transection were morphologically and immunohistochemically examined. In the heel skin, redness and swelling began by 3days after the operation, and open wound formed by 17days. At the redness and swelling stage, edema extensively occurred in the dermis. At the thickening stage, the epidermis at the pressed site became transiently thicker, and at the whitening stage, rapidly thinner. At these stages, the epidermis in the skin surrounding the pressed site became gradually thicker. At the yellow scar stage, the skin was covered only by necrotic tissues and horny layer. These layers were scratched during walking and turning, and the yellow scar stage became the open wound stage. Inflammatory reaction began at the thickening stage, and at the yellow scar and open wound stages, necrosis, infiltration of inflammatory cells and dilation of small blood vessels were observed. These morphological features are quite similar to those in the human pressure ulcer. These findings suggest that these dermal injuries could compare the human pressure ulcer for medical treatment and depressurization in future study. Copyright © 2016 Elsevier GmbH. All rights reserved.

Empirical study of classification process for two-stage turbo air classifier in series

NASA Astrophysics Data System (ADS)

Yu, Yuan; Liu, Jiaxiang; Li, Gang

2013-05-01

The suitable process parameters for a two-stage turbo air classifier are important for obtaining the ultrafine powder that has a narrow particle-size distribution, however little has been published internationally on the classification process for the two-stage turbo air classifier in series. The influence of the process parameters of a two-stage turbo air classifier in series on classification performance is empirically studied by using aluminum oxide powders as the experimental material. The experimental results show the following: 1) When the rotor cage rotary speed of the first-stage classifier is increased from 2 300 r/min to 2 500 r/min with a constant rotor cage rotary speed of the second-stage classifier, classification precision is increased from 0.64 to 0.67. However, in this case, the final ultrafine powder yield is decreased from 79% to 74%, which means the classification precision and the final ultrafine powder yield can be regulated through adjusting the rotor cage rotary speed of the first-stage classifier. 2) When the rotor cage rotary speed of the second-stage classifier is increased from 2 500 r/min to 3 100 r/min with a constant rotor cage rotary speed of the first-stage classifier, the cut size is decreased from 13.16 μm to 8.76 μm, which means the cut size of the ultrafine powder can be regulated through adjusting the rotor cage rotary speed of the second-stage classifier. 3) When the feeding speed is increased from 35 kg/h to 50 kg/h, the "fish-hook" effect is strengthened, which makes the ultrafine powder yield decrease. 4) To weaken the "fish-hook" effect, the equalization of the two-stage wind speeds or the combination of a high first-stage wind speed with a low second-stage wind speed should be selected. This empirical study provides a criterion of process parameter configurations for a two-stage or multi-stage classifier in series, which offers a theoretical basis for practical production.

Comparison of the AJCC, MSTS, and Modified Spanier Systems for Clinical and Pathologic Staging of Osteosarcoma.

PubMed

Cates, Justin M M

2017-03-01

The prognostic performance of the 2 most commonly used staging systems for skeletal sarcoma (the American Joint Committee on Cancer [AJCC] and Musculoskeletal Tumor Society [MSTS] systems) have never been compared analytically. Another staging system originally proposed by Spanier has not yet been validated. Given the recent release of the 8th edition of the AJCC Cancer Staging Manual, this study was designed to directly compare these anatomic staging systems in a series of 153 high-grade, intramedullary osteosarcomas. Kaplan-Meier curves were plotted and pairwise comparisons between each stage category were performed. Predictive accuracy of each staging system for determining 5-year disease-free survival was evaluated by comparing areas under receiver-operating characteristic curves generated from logistic regression analysis. Multiple concordance indices were calculated using bootstrapping methods (200 replications). ρk and R were estimated as measures of the variation in survival outcomes explained by the regression models. The AJCC, MSTS, and a modified version of the Spanier staging systems showed similar discriminatory abilities and no significant differences in the levels of contrast between different tumor stages across staging systems. Addition of T-category information from each staging system contributed significant prognostic information compared with a Cox proportional hazard regression model consisting only of the presence or absence of metastatic disease as a measure of disease extent. Concordance indices and predictive accuracy for 5-year disease-free survival were not significantly different among the different staging systems either. Similar findings were observed after accounting for other important prognostic variables. Additional studies are necessary to determine performance parameters of each staging system for other types of skeletal sarcoma. Prognostic performance of osteosarcoma staging systems would also be improved by incorporating nonanatomic prognostic variables into staging algorithms.

Radiographic assessment of skeletal maturation stages for orthodontic patients: hand-wrist bones or cervical vertebrae?

PubMed

Lai, Eddie Hsiang-Hua; Liu, Jen-Pei; Chang, Jenny Zwei-Chieng; Tsai, Shih-Jaw; Yao, Chung-Chen Jane; Chen, Mu-Hsiung; Chen, Yi-Jane; Lin, Chun-Pin

2008-04-01

The skeletal maturation status of a growing patient can influence the selection of orthodontic treatment procedures. Either lateral cephalometric or hand-wrist radiography can be used to assess skeletal development. In this study, we examined the correlation between the maturation stages of cervical vertebrae and hand-wrist bones in Taiwanese individuals. The study group consisted of 330 male and 379 female subjects ranging in age from 8 to 18 years. A total of 709 hand-wrist and 709 lateral cephalometric radiographs were analyzed. Hand-wrist maturation stages were assessed using National Taiwan University Hospital Skeletal Maturation Index (NTUH-SMI). Cervical vertebral maturation stages were determined by the latest Cervical Vertebral Maturation Stage (CVMS) Index. Spearman's rank correlation was used to correlate the respective maturation stages assessed from the hand-wrist bones and the cervical vertebrae. The values of Spearman's rank correlation were 0.910 for males and 0.937 for females, respectively. These data confirmed a strong and significant correlation between CVMS and NTUH-SMI systems (p less than 0.001). After comparison of the mean ages of subjects in different stages of CVMS and NTU-SMI systems, we found that CVMS I corresponded to NTUH-SMI stages 1 and 2, CVMS II to NTUH-SMI stage 3, CVMS III to NTUHSMI stage 4, CVMS IV to NTUH-SMI stage 5, CVMS V to NTUH-SMI stages 6, 7 and 8, and CVMS VI to NTUH-SMI stage 9. Our results indicate that cervical vertebral maturation stages can be used to replace hand-wrist bone maturation stages for evaluation of skeletal maturity in Taiwanese individuals.

The proportion cured of patients diagnosed with Stage III-IV cutaneous malignant melanoma in Sweden 1990-2007: A population-based study.

PubMed

Eriksson, Hanna; Lyth, Johan; Andersson, Therese M-L

2016-06-15

The survival in cutaneous malignant melanoma (CMM) is highly dependent on the stage of the disease. Stage III-IV CMM patients are at high risk of relapse with a heterogeneous outcome, but not all experience excess mortality due to their disease. This group is referred to as the cure proportion representing the proportion of patients who experience the same mortality rate as the general population. The aim of this study was to estimate the cure proportion of patients diagnosed with Stage III-IV CMM in Sweden. From the population-based Swedish Melanoma Register, we included 856 patients diagnosed with primary Stage III-IV CMM, 1990-2007, followed-up through 2013. We used flexible parametric cure models to estimate cure proportions and median survival times (MSTs) of uncured by sex, age, tumor site, ulceration status (in Stage III patients) and disease stage. The standardized (over sex, age and site) cure proportion was lower in Stage IV CMMs (0.15, 95% CI 0.09-0.22) than non-ulcerated Stage III CMMs (0.48, 95% CI 0.41-0.55) with a statistically significant difference of 0.33 (95% CI = 0.24-0.41). Ulcerated Stage III CMMs had a cure proportion of 0.27 (95% CI 0.21-0.32) with a statistically significant difference compared to non-ulcerated Stage III CMMs (difference 0.21; 95% CI = 0.13-0.30). The standardized MST of uncured was approximately 9-10 months longer for non-ulcerated versus ulcerated Stage III CMMs. We could demonstrate a significantly better outcome in patients diagnosed with non-ulcerated Stage III CMMs compared to ulcerated Stage III CMMs and Stage IV disease after adjusting for age, sex and tumor site. © 2016 UICC.

Use of leaning vanes in a two stage fan

NASA Technical Reports Server (NTRS)

Rao, G. V. R.; Digumarthi, R. V.

1975-01-01

The use of leaning vanes for tone noise reduction was examined in terms of their application in a typical two-stage high pressure ratio fan. In particular for stages designed with outlet guide vanes and zero swirl between stages, leaning the vanes of the first stage stator was studied, since increasing the number of vanes and the gap between stages do not provide the desired advantage. It was shown that noise reduction at higher harmonics of blade passing frequency can be obtained by leaning the vanes.

The Influence of Social Determinants on Late Stage Breast Cancer for Women in Mississippi.

PubMed

Fortune, Melody L

2017-02-01

Breast cancer is the most common diagnosed cancer in women exacting an emotional and economic hardship for them and their families. There are no known causes of breast cancer, but there are certain genetic, social, and environment risk factors that pre-dispose women to this disease. Also, diagnosis at later stages of disease has been shown to have adverse outcomes for many as compared to early stages. The social determinants researched to examine their influence on breast cancer outcomes were race, health insurance, and income. The results of this study confirmed that race and health insurance were the two major factors that negatively impacted stages of breast cancer diagnoses. The purpose of this study was to investigate the influence that social determinants have on stage of breast cancer diagnoses. This research focused on three social determinants that research demonstrated had an influence on stages of breast cancer diagnoses (race, income, and lack of health insurance). Bivariate analyses were conducted to examine the relationships between race and income, race and health insurance, and race and stage of diagnosis. The findings confirmed what was suspected for Mississippians; more African Americans had lower incomes, had less health insurance coverage, and were diagnosed at later stages of breast cancer disease. Only race and health insurance directly affected late stage diagnosis in analyses for this study. The influence of income on stage of breast cancer diagnosis was not statistically significant. The results of these analyses demonstrated that African American women in Mississippi were disproportionately diagnosed at late stage breast cancer as opposed to early stage. An individual cannot alter the genetic factor of race, but some of the disparate health outcomes that appear to be associated with race may be behavioral or socio-economically based and can be addressed, which could impact health outcomes. Adequate health insurance could positively impact stage of breast cancer diagnoses, ultimately reducing health disparities and premature death.

Stage progression and neurological symptoms in Trypanosoma brucei rhodesiense sleeping sickness: role of the CNS inflammatory response.

PubMed

MacLean, Lorna; Reiber, Hansotto; Kennedy, Peter G E; Sternberg, Jeremy M

2012-01-01

Human African trypanosomiasis progresses from an early (hemolymphatic) stage, through CNS invasion to the late (meningoencephalitic) stage. In experimental infections disease progression is associated with neuroinflammatory responses and neurological symptoms, but this concept requires evaluation in African trypanosomiasis patients, where correct diagnosis of the disease stage is of critical therapeutic importance. This was a retrospective study on a cohort of 115 T.b.rhodesiense HAT patients recruited in Eastern Uganda. Paired plasma and CSF samples allowed the measurement of peripheral and CNS immunoglobulin and of CSF cytokine synthesis. Cytokine and immunoglobulin expression were evaluated in relation to disease duration, stage progression and neurological symptoms. Neurological symptoms were not related to stage progression (with the exception of moderate coma). Increases in CNS immunoglobulin, IL-10 and TNF-α synthesis were associated with stage progression and were mirrored by a reduction in TGF-β levels in the CSF. There were no significant associations between CNS immunoglobulin and cytokine production and neurological signs of disease with the exception of moderate coma cases. Within the study group we identified diagnostically early stage cases with no CSF pleocytosis but intrathecal immunoglobulin synthesis and diagnostically late stage cases with marginal CSF pleocytosis and no detectable trypanosomes in the CSF. Our results demonstrate that there is not a direct linkage between stage progression, neurological signs of infection and neuroinflammatory responses in rhodesiense HAT. Neurological signs are observed in both early and late stages, and while intrathecal immunoglobulin synthesis is associated with neurological signs, these are also observed in cases lacking a CNS inflammatory response. While there is an increase in inflammatory cytokine production with stage progression, this is paralleled by increases in CSF IL-10. As stage diagnostics, the CSF immunoglobulins and cytokines studied do not have sufficient sensitivity to be of clinical value.

Factors Associated with Exercise Motivation among African-American Men.

PubMed

Mohammed, Alana; Harrell, Jules P; Makambi, Kepher H; Campbell, Alfonso L; Sloan, Lloyd Ren; Carter-Nolan, Pamela L; Taylor, Teletia R

2016-09-01

The primary aims of this study were to: (1) characterize exercise stages of change among a sample of African-American men, (2) determine if exercise motivation was associated with self-reported exercise behavior, and (3) examine if groups of personal (i.e., age, BMI, income, educational attainment, and perceived health), psycho-social (i.e., exercise self-efficacy, personality type, social influence), and environmental factors (i.e., neighborhood safety) predicted stages of change for physical exercise among African-American men. One hundred seventy African-American male participants were recruited for this study (age: 47.63(10.23) years). Participants completed a self-report questionnaire assessing study variables. Multinomial logistic regression models were used to examine the association of exercise stages of change with an array of personal, psychosocial, and environmental factors. BMI, exercise self-efficacy, and nighttime neighborhood safety were entered as independent variables in the full model. BMI and exercise self-efficacy continued to be significant predictors of exercise stages of change in the full model. Obese men had a 9.24 greater odds of being in the action stage of change than in the maintenance stage. Also, men reporting greater exercise self-efficacy had lower odds of being in the lower stages of change categories (pre-preparation, preparation, and action) than in the maintenance stage. Our results confirmed that using an ecological framework explained more of the variance in exercise stages of change than any of the individual components alone. Information gleaned from this study could inform interventionists of the best ways to create tailored exercise programs for African-American men.

The effects of EGF and IGF-1 on FSH-mediated in vitro maturation of domestic cat oocytes derived from follicular and luteal stages.

PubMed

Yıldırım, Koray; Vural, M Rıfat; Küplülü, Sükrü; Ozcan, Ziya; Polat, I Mert

2014-04-01

The objective of this study was to evaluate the influence of epidermal growth factor (EGF) and insulin like growth factor-I (IGF-1) on the in vitro maturation of cat oocytes recovered from follicular and luteal stage ovaries. Oocytes from follicular (n=580) and luteal (n=209) stages were harvested and divided into four groups, which were cultured in FSH-mediated maturation medium supplemented with: (1) EGF alone (25ng/mL); (2) IGF-1 alone (100ng/mL); (3) EGF+IGF-1 (25ng/mL EGF+100ng/mL IGF-I); or (4) no growth factor (control). The proportion of follicular stage oocytes reaching the metaphase II stage was significantly higher than that of oocytes obtained at the luteal stage in both control and study groups (p<0.001). The percentages of oocytes reaching the metaphase II stage during the follicular period were 62.6% in control; 70.9% in EGF; 72.8% in IGF-1, and 78.1% in EGF+IGF-1 groups, whereas the respective values for gametes collected from luteal stage ovaries were 12.5%, 17.5%, 12.5%, and 16.9%. Additionally, the differences between the study and control groups were significant in the case of follicular stage oocytes. Finally, supplementing the maturation medium with EGF and/or IGF-1 significantly enhanced the meiotic maturation of oocytes recovered from follicular stage ovaries. The present study also demonstrated that the combination of EGF and IGF-I provides an additional or synergic effect on meiotic maturation of oocytes recovered from the follicular stage. Copyright © 2014 Society for Biology of Reproduction & the Institute of Animal Reproduction and Food Research of Polish Academy of Sciences in Olsztyn. Published by Elsevier Urban & Partner Sp. z o.o. All rights reserved.

Modeling the mechanical properties of liver fibrosis in rats.

PubMed

Zhu, Ying; Chen, Xin; Zhang, Xinyu; Chen, Siping; Shen, Yuanyuan; Song, Liang

2016-06-14

The progression of liver fibrosis changes the biomechanical properties of liver tissue. This study characterized and compared different liver fibrosis stages in rats in terms of viscoelasticity. Three viscoelastic models, the Voigt, Maxwell, and Zener models, were applied to experimental data from rheometer tests and then the elasticity and viscosity were estimated for each fibrosis stage. The study found that both elasticity and viscosity are correlated with the various stages of liver fibrosis. The study revealed that the Zener model is the optimal model for describing the mechanical properties of each fibrosis stage, but there is no significant difference between the Zener and Voigt models in their performance on liver fibrosis staging. Therefore the Voigt model can still be effectively used for liver fibrosis grading. Copyright © 2016 Elsevier Ltd. All rights reserved.

Phase I-II Study of Fluorouracil in Combination With Phenylbutyrate in Advanced Colorectal Cancer

ClinicalTrials.gov

2013-01-31

Mucinous Adenocarcinoma of the Colon; Mucinous Adenocarcinoma of the Rectum; Recurrent Colon Cancer; Recurrent Rectal Cancer; Signet Ring Adenocarcinoma of the Colon; Signet Ring Adenocarcinoma of the Rectum; Stage IVA Colon Cancer; Stage IVA Rectal Cancer; Stage IVB Colon Cancer; Stage IVB Rectal Cancer

Pubertal Stage, Body Mass Index, and Cardiometabolic Risk in Children and Adolescents in Bogotá, Colombia: The Cross-Sectional Fuprecol Study

PubMed Central

Ramírez-Vélez, Robinson; García-Hermoso, Antonio; Agostinis-Sobrinho, Cesar; Mota, Jorge; Santos, Rute; Correa-Bautista, Jorge Enrique; Peña-Guzmán, Carlos Andrés; Domínguez-Sánchez, María Andrea; Schmidt-RioValle, Jacqueline; González-Jiménez, Emilio

2017-01-01

This study explored the association between pubertal stage and anthropometric and cardiometabolic risk factors in youth. A cross-sectional study was conducted in 2877 Colombian children and adolescents (9–17.9 years of age). Weight, height, and waist circumference were measured and body mass index (BMI) was calculated. A biochemical study was performed to determine the cardiometabolic risk index (CMRI). Blood pressure was evaluated and pubertal stage was assessed with the Tanner criteria. Hierarchical multiple regression analyses were performed. The most significant variable (p < 0.05) in the prognosis of cardiometabolic risk was found to be the BMI in both boys and girls. In the case of girls, the pubertal stage was also a CMRI predictive factor. In conclusion, BMI was an important indicator of cardiovascular risk in both sexes. Pubertal stage was associated with cardiovascular risk only in the girls. PMID:28640231

Pubertal Stage, Body Mass Index, and Cardiometabolic Risk in Children and Adolescents in Bogotá, Colombia: The Cross-Sectional Fuprecol Study.

PubMed

Ramírez-Vélez, Robinson; García-Hermoso, Antonio; Agostinis-Sobrinho, Cesar; Mota, Jorge; Santos, Rute; Correa-Bautista, Jorge Enrique; Peña-Guzmán, Carlos Andrés; Domínguez-Sánchez, María Andrea; Schmidt-RioValle, Jacqueline; González-Jiménez, Emilio

2017-06-22

This study explored the association between pubertal stage and anthropometric and cardiometabolic risk factors in youth. A cross-sectional study was conducted in 2877 Colombian children and adolescents (9-17.9 years of age). Weight, height, and waist circumference were measured and body mass index (BMI) was calculated. A biochemical study was performed to determine the cardiometabolic risk index (CMRI). Blood pressure was evaluated and pubertal stage was assessed with the Tanner criteria. Hierarchical multiple regression analyses were performed. The most significant variable ( p < 0.05) in the prognosis of cardiometabolic risk was found to be the BMI in both boys and girls. In the case of girls, the pubertal stage was also a CMRI predictive factor. In conclusion, BMI was an important indicator of cardiovascular risk in both sexes. Pubertal stage was associated with cardiovascular risk only in the girls.

Effects of wearing rubber gloves on activities of the forearm and shoulder muscles during different dishwashing stages

PubMed Central

Yoo, Won-Gyu

2015-01-01

[Purpose] The present study examined the effects of wearing rubber gloves on the activities of the forearm and shoulder muscles during two dishwashing stages. [Subjects] This study included 10 young females. [Methods] The participants performed two dishwashing stages (washing and rinsing) with and without rubber gloves. The activities of the wrist flexor and upper trapezius muscles were measured using wireless electromyography. [Results] During the washing stage, the activities of the wrist flexor and upper trapezius muscles were significantly greater without gloves than with gloves when performing the same tasks. However, during the rinsing stage, the activities of these muscles did not differ significantly according to the use of gloves. [Conclusion] Dishwashers should wear gloves during the washing stage to prevent wrist and shoulder pain. PMID:26311980

Lazy gene (la) responsible for both an agravitropism of seedlings and lazy habit of tiller growth in rice (Oryza sativa L.).

PubMed

Abe, K; Takahashi, H; Suge, H

1996-12-01

Using an isogenic line of rice having lazy gene (la), we studied the correlation between the agravitropic response at the young seedling stage and the lazy habit (prostrate growth of tillers) at the more advanced stage of growth. In this study, it was found that both agravitropism and lazy habit were controlled by the single recessive la gene. That is, F2 segregants of Kamenoo x lazy-Kamenoo, which had an agravitropic response at their young seedling stage, showed a lazy habit of growth in the more advanced stage of vegetative growth. On the other hand, seedlings that showed normal gravitropic curvature at their early stage of growth had an upright growth in the mature stage.

Integrating macro- and micro-level approaches in the explanation of population change

PubMed Central

Billari, Francesco C.

2015-01-01

Demographers study population change across time and place, and traditionally they place a strong emphasis on a long-range view of population change. This paper builds on current reflections on how to structure the study of population change and proposes a two-stage perspective. The first stage, discovery, focuses on the production of novel evidence at the population level. The second stage, explanation, develops accounts of demographic change and tests how the action and interaction of individuals generate what is discovered in the first stage. This explanatory stage also provides the foundation for the prediction of demographic change. The transformation of micro-level actions and interactions into macro-level population outcomes is identified as a key challenge for the second stage. Specific instances of research are discussed. PMID:25912913