Low Diffusion Coefficient Values Research Articles

Excellent diffusion barrier property of amorphous NbMoTaW medium entropy alloy thin films used in Cu/Si Connect System

In this work, NbMoTaW medium entropy alloy (MEA) films with thickness of 40 nm were prepared by DC magnetron sputtering as a diffusion barrier material for Cu/Si Connect System. The microstructure and thermal property of Cu/NbMoTaW/Si and Cu/Si stacks in varies of annealing temperature (T) were studies by XRD, SEM, TEM and four-point probe measurement system. The results show that the amorphous NbMoTaW films can suppress Si inter-diffusion in Cu film when T is lower than 750 °C while electrical property of Cu/Si system without the barrier fails when T reaches 450 °C. Free of grain boundary, low diffusion coefficient value and stable structure of amorphous NbMoTaW MEA film are suggested to be the main reasons for the excellent barrier property.

РАННЯЯ ДИАГНОСТИКА ПОСЛЕДСТВИЙ НАРУШЕНИЯ МОЗГОВОГО КРОВООБРАЩЕНИЯ У ДЕТЕЙ С ПЕРИНАТАЛЬНЫМ ГИПОКСИЧЕСКИМ ПОРАЖЕНИЕМ ГОЛОВНОГО МОЗГА

Exposure to hypoxia in the perinatal period leads to significant structural changes in the brain (B), which are reflected in the further neuropsychic development of the child. In this regard, the assessment of the state of brain structures and cerebral circulation in young children using high-tech diagnostic methods is of particular importance. Objective of the study: to analyze the indicators of magnetic resonance imaging (MRI) of B structures for early diagnosis of the consequences of cerebrovascular accident in children who underwent hypoxia in the perinatal period. Materials and methods of research: single-center prospective open non-randomized longitudinal observational uncontrolled study were included in 144 newborns, who were stationed in the intensive care unit and intensive therapy units (ICU) of the Regional Perinatal Center of the Krasnodar Regional Clinical Hospital for severe asphyxia and/or intrauterine hypoxia. Among those included in the study were 76 full-term babies (FTBs) (group 1) and 68 premature newborns (PNs) (group 2). The gestational age (GA) of PNs was 29–37 (32.7±2.6) weeks. The sex composition of the groups (boys/girls) did not differ statistically significantly: n=41/35 – 54%/46% in the 1st group versus n=38/30 – 56%/44% in the 2nd group (p=0.816). All children underwent MRI of the B on 2–10 day of life with the determination of the measurement of diffusion coefficient (DC) in the mode of diffusion-weighted images. Children were observed up to 3 years of age in the follow-up department of the Krasnodar Krai Regional Children's Clinical Hospital. Results: in the PNs group, 35 (51%) GA was 29–32 weeks, in 33 (49%) children – 33–37 weeks. The revealed consequences of hypoxic B damage in children were determined by morphological changes in the nervous tissue and were characterized by objective MRI indicators. Analysis of the data obtained made it possible to identify the ranges of B ADI values, reflecting the subsequent neurological outcome. Further formation of neurological deficits (infantile cerebral palsy, disorders of psychoverbal development, symptomatic epilepsy) was noted in PNs with relatively low DC values 0.69–1.30×10–3mm2/s and 0.64–1.07×10–3mm2/s – for white and gray matter of the large hemispheres of the B, respectively; in PNs with relatively low and relatively high DC values of the white matter of the large hemispheres of the B 1.05–1.24×10–3mm2/s and 1.88–2.00×10–3mm2/s, gray matter of the B cerebral hemispheres 0, 93–1.06×10–3mm2/s and 1.36–1.47×10–3mm2/s. The effect of hypoxia in the intrapartum period was manifested by low DC indices, reflecting manifestations of cerebral ischemia. A significant increase in DC indicators was observed in hypoxic brain damage in the antenatal period and characterized atrophic changes in the nervous tissue. Based on the results of the analysis of B DC indices, reflecting manifestations of cerebral ischemia, statistically significant (p<0.01) direct highly correlated relationships were revealed between the DC indices of the white matter of the cerebral hemispheres and the indices of the DC of the gray matter of the cerebral hemispheres (rxy=0.975), the indices of the DC of the midbrain (rxy=0.714) in FTBs, between the indicators of the DC of the white matter of the cerebral hemispheres and the indicators of the DC of the gray matter (rxy=0.923), the indicators of the DC of the midbrain (rxy=0.787) in the PBs, which indicates the global nature of the hypoxic damage to the B. Conclusions: early diagnosis of cerebrovascular accidents in children using MRI data makes it possible to predict the further neurological outcome of perinatal hypoxic brain injures, contributes to the timely implementation of therapeutic and rehabilitation measures based on an objective assessment of the identified disorders.

Informativeness of whole-body diffusion-weighted magnetic resonance imaging and positron emission tomography with computed tomography in follicular lymphoma

This study conducted the possibilities of diffusion-weighted magnetic resonance imaging of the whole body diffusion WB-MRI (in comparison with positron emission tomography with computed tomography PET/CT) in assessing the volume and prevalence of the tumor, as well as determining bone marrow (BM) damage (for various cytological types) in the diagnosis and staging of the disease in patients with FL. A prospective comparative search study included 15 patients (4 men and 11 women, with a median age of 53 years) with newly diagnosed FL. Patients have not received antitumor chemotherapy previously. After the diagnosis was established, all patients (with the blindness of both the cases themselves and some specialists regarding the results of other specialists) were examined by PET/CT and diffusion WB-MRI, after which a BM examination was performed (histological examination and determination of B-cell clonality in BM puncture by PCR). Using the diffusion WB-MRI method, the prevalence of tumor lesion (nodal and extranodal foci) in each patient was estimated, and the total tumor volume was calculated, BM lesion was detected, and BM lesion volume was calculated. For lesions of different localization, the measured diffusion coefficient (DC) of the diffusion WB-MRI and the standardized rate of accumulation of the radiopharmaceutical in tissues (SUV) of the PET/CT method were determined and compared with each other (for the same areas). Statistical analysis was performed using the estimate of agreement (by Cohens kappa coefficient and asymptotic test) of the results of the compared methods. Estimates of the prevalence of tumor damage (lymph nodes and extranodal foci) using the diffusion WB-MRI and PET/CT methods were the same. High DC and SUV were observed in the peripheral lymph nodes, extranodal foci and bulky, low DC and SUV in the foci of BM. All 4 methods successfully determined BM damage, however, the diffusion WB-MRI had comparatively less negative results. The highest values of SUV and CD were noted in cases of the 3 grade of FL. Using the diffusion WB-MRI method, the prevalence of tumor lesion was assessed in each patient (nodal and extranodal foci were detected) and the total tumor volume was calculated, BM lesion detection was performed, and the volume of BM lesion was calculated. It is important to note that with the help of diffusion WB-MRI, it was possible to measure separately the total tumor volume (462025 cm3) and separately the volume of bulky (251358 cm3). The diffusion WB-MRI allowed us to differentiate the volume of tumor tissue (reduced as a result of treatment) and residual (fibrous-adipose) tissue in residual formations (which averaged 21% of the initial volume). The predictors of a poor antitumor response were the maximum SUV values (more than 14.0) and the minimum DC values (0.510-3mm2/s) in the BM foci. The diffusion WB-MRI allows for detailed visualization of BM lesions and surrounding soft tissues both in the debut of the FL and in the process of tracking the effectiveness of chemotherapy, which makes it possible to use it along with PET/CT. Diffusion WB-MRI allows to separately evaluate the volume of true tumor tissue and residual tissue. Cases of the 3 grade of FL (including the transformation of FL into diffuse B-large cell lymphoma) are isolated due to low DC values (and high SUV values) in the tumor tissue. BM foci of FL lesion also have (in comparison with nodal and extranodal foci) lower DC values. The predictors of a poor antitumor response were high (from 14.0 or more) SUV valuesin the tumor (and especially in bulky), and low (about 0.5103mm2/s) DC values of BM foci. The PET/CT and diffusion WB-MRI have proven to be reliable diagnostic tools for establishing the stage of FL and detecting BM damage. Diffusion WB-MRI for FL is an informative first-line diagnostic method that allows regular monitoring of the disease and early detection of foci of relapse and disease progression.

IN VITRO AND IN SILICO EVALUATION OF ANTICANCER ACTIVITY OF N,N-DIMETHYLAMINOMETHYLFERROCENE

The aim of this stydy was to examine the interaction of DNA with the ligand N,N-dimethylaminomethylferrocene (NDF) in buffer phosphate solution (pH = 7.2) by electronic spectroscopy, electrochemical and molecular docking technics. The electrochemical results showed that the binding constant and free binding energy of the addauct DNA-NDF is equal to 1.48×10-4 and -23,81 KJ.mol-1 respectively. These results were in good agreement with those obtained from electronic spectroscopie assays; furthermore the interaction was also confirmed by the low value of diffusion coefficient of the bounded ligand 1.83×10-8 cm2.s-1 as compared to the free ligand 2.13×10-8 cm2.s-1. In addition the in silico study by molecular docking confirms the obtained in vitro results. Molecular docking further indicated that the ligand is binds to DNA via a hydrogen bond between ist nitrogen atom and the oxygen number 4 of the deoxyadenine of the DNA B-chain.

Hydrodynamic and Electrophoretic Properties of Trastuzumab/HER2 Extracellular Domain Complexes as Revealed by Experimental Techniques and Computational Simulations.

The combination of hydrodynamic and electrophoretic experiments and computer simulations is a powerful approach to study the interaction between proteins. In this work, we present hydrodynamic and electrophoretic experiments in an aqueous solution along with molecular dynamics and hydrodynamic modeling to monitor and compute biophysical properties of the interactions between the extracellular domain of the HER2 protein (eHER2) and the monoclonal antibody trastuzumab (TZM). The importance of this system relies on the fact that the overexpression of HER2 protein is related with the poor prognosis breast cancers (HER2++ positives), while the TZM is a monoclonal antibody for the treatment of this cancer. We have found and characterized two different complexes between the TZM and eHER2 proteins (1:1 and 1:2 TZM:eHER2 complexes). The conformational features of these complexes regulate their hydrodynamic and electrostatic properties. Thus, the results indicate a high degree of molecular flexibility in the systems that ultimately leads to higher values of the intrinsic viscosity, as well as lower values of diffusion coefficient than those expected for simple globular proteins. A highly asymmetric charge distribution is detected for the monovalent complex (1:1 complex), which has strong implications in correlations between the experimental electrophoretic mobility and the modeled net charge. In order to understand the dynamics of these systems and the role of the specific domains involved, it is essential to find biophysical correlations between dynamics, macroscopic transport and electrostatic properties. The results should be of general interest for researchers working in this area.

Molecular and hydrodynamic properties of human epidermal growth factor receptor HER2 extracellular domain and its homodimer: Experiments and multi-scale simulations

BackgroundIn a broad range of human carcinomas gene amplification leads to HER2 overexpression, which has been proposed to cause spontaneous dimerization and activation in the absence of ligand. This makes HER2 attractive as a therapeutic target. However, the HER2 homodimerization mechanism remains unexplored. It has been suggested that the “back-to-back” homodimer does not form in solution. Notwithstanding, very recently the crystal structure of the HER2 extracellular domain homodimer formed with a “back-to-head” interaction has been resolved. We intend to explore the existence of such interactions. MethodsA combination of experiments, molecular dynamics and hydrodynamic modeling were used to monitor the transport properties of HER2 in solution. Results & conclusionsWe have detected the HER2 extracellular domain homodimer in solution. The results show a high degree of molecular flexibility, which ultimately leads to quite higher values of the intrinsic viscosity and lower values of diffusion coefficient than those corresponding to globular proteins. This flexibility obeys to the open conformation of the receptor and to the large fluctuations of the different domains. We also report that for obtaining the correct hydrodynamic constants from the modeling one must consider the glycosylation of the systems. General significanceConformational features of epidermal growth factor receptors regulate their hydrodynamic properties and control their activity. It is essential to understand the dynamics of these systems and the role of the specific domains involved. To find biophysical correlations between dynamics and macroscopic transport properties is of general interest for researches working in this area. This article is part of a Special Issue entitled “Biochemistry of Synthetic Biology - Recent Developments” Guest Editor: Dr. Ilka Heinemann and Dr. Patrick O'Donoghue.

Electrochemical studies on the reduction behaviour of ruthenium nitrosyl ions in nitric acid medium

To understand the low recovery of ruthenium from ruthenium nitrosyl nitrate solution by electro-deposition technique, electro-reduction behaviour of ruthenium nitrosyl complex [RuII–NO+]3+ in nitric acid medium was investigated using the potentiostatic electrolysis techniques, cyclic voltammetry and chronopotentiometry at Pt and glassy carbon working electrodes. Reduction of [RuNO]3+ was found to be quasi-reversible, one electron transfer process at both the electrodes. The diffusion coefficient (D 0) of [RuNO]3+ species estimated by these techniques was in the order of 10−8 cm2 s−1 and the heterogeneous electron transfer rate constant (k s) for the reduction of [RuNO]3+ was estimated to be about 10−5 cm s−1 using Klingler and Kochi equation. The very low diffusion coefficient value and the low separation percentage of Ru from ruthenium nitrosyl nitrate solution by electro-deposition technique are attributed to the existence of Ru(II) in different stable complexes instead of bare Ru(II) ions, in nitric acid medium.

Influence of Hot Implantation on Residual Radiation Damage in Silicon Carbide

Remarkable thermomechanical and electrical properties of silicon carbide (SiC) make this material very attractive for high-temperature, high-power, and high-frequency applications. Because of very low values of diffusion coefficient of most impurities in SiC, ion implantation is the best method to selectively introduce dopants over well-defined depths in SiC. Aluminium is commonly used for creating p-type regions in SiC. However, post-implantation radiation damage, which strongly deteriorates required electric properties of the implanted layers, is difficult to anneal even at high temperatures because of remaining residual damage. Therefore implantation at elevated target temperatures (hot implantation) is nowadays an accepted method to decrease the level of the residual radiation damage by avoiding ion beam-induced amorphization. The main objective of this study is to compare the results of the Rutherford backscattering spectroscopy with channeling and micro-Raman spectroscopy investigations of room temperature and 500 ◦C Al ion implantation-induced damage in 6H-SiC and its removal by high temperature (up to 1600 ◦C) thermal annealing.

Quantification of Scale and Monolith Surface Exposure Effects on Contaminant Leaching from Flowable Fill

The volumetric specific surface (S/V) of monoliths influences contaminant leachability. Small samples such as those used in laboratory-based leaching tests have higher S/V ratios than larger monoliths of controlled low-strength materials (CLSM) in utility and energy pipeline trenches. Quantitative relationships are herein derived for relating contaminant leaching rates from full-scale monolith-filled trenches in the field to laboratory leaching data. A field dimensional exposure modification factor, P, is derived with a magnitude range of 37.6 to 50.37 for trenches with length and cross-sectional area dimensional ranges of 10–15 m and 1–4 m, respectively. Then, P, which increases with CLSM sectional area, is applied to copper, arsenic, and selenium leaching data for CLSM comprising portland cement, aggregate, water, and fly ash, ranging in weight contents from 5 to 20%. The results of leaching with water and pH 5.5 leachant show that computed diffusion coefficients for the metals in the field, Def values are higher than values obtained for small samples through leaching tests in the laboratory. Furthermore, Def values are higher at low ash substitution levels than at higher levels. The highest Def values, which are at 5% ash content, are 2.09 × 10−4 m2/s (deionized water), 7.29 × 10−11 m2/s (pH 5.5) and 2.09 × 10−10 m2/s (pH 5.5) for copper, arsenic, and selenium, respectively. Apparently, at higher ash contents, cementation effects decrease monolith porosity to produce lower values of diffusion coefficient. Computed estimates of cumulative leaching fractions at high saturation are low for the contaminants and are directly proportional to Def values.

EFFECTS OF GLASS MICROFILLERS ON THE WATER-TRANSPORT BEHAVIOR OF POLYURETHANE COMPOSITES

Glass microspheres with unique composition and diameter, and modified by different surface treatments, were blended with polyurethane (PU) in various proportions to improve the liquid transport properties of the PU composites. Transport properties such as diffusion, permeability, and sorption coefficient were measured on various filler-filled PU composites at three different temperatures. These temperature-dependent parameters were used to provide a quantitative way to examine the effects of filler loading and the surface properties on the improvement of the water transport properties of PU composites. Results show that due to trapping at interfacial boundaries between filler and polymer, a high water affinity and large space for water activity is expected inside all the filler-filled composites. As a result, lower water diffusion (or high water resistivity) was found among all the filler-filled composites compared to that of filler-free composites. Besides, the more filler present in the composite, the longer the paths of the water molecules within the composites as the water penetration proceeds. Thus, lower diffusion coefficient values were observed for composites with large amounts of filler addition.

Interdiffusion in ternary Ni 3Al/Ni 3Al-X diffusion couples with X=Cr, Fe, Nb and Ti

The γ′ single phase interdiffusion in selected pseudo-binary sections of the Ni 3Al-X (X=Cr, Fe, Nb and Ti) ternary alloys was studied in temperature interval 1173–1533 K in order to assess the influence of the site-preference of components upon their diffusion rate. It was observed that ( a) Higher fraction of Cr or Fe on Al sublattice leads to lower values of D̃ XX ( Ni) . ( b) Both Ti and Nb, preferring strongly the Al sublattice, show significantly lower interdiffusion coefficients than Fe and Cr. ( c) The equation D̃ XX ( Ni) = D̃ AlAl ( Ni) holds for Ti and Nb, whereas the relation D̃ XX ( Ni) > D̃ AlAl ( Ni) is valid for Cr and Fe. ( d) Activation enthalpy of Q ii ( j) shows a systematic decrease with increasing valence electron number of the alloying element i. ( e) Nb shows a transient behavior Q—it has low values of diffusion coefficient compared to its site occupation but also a low activation energy.

Isotopic ion-exchange studies in heteroionic systems

Isotopic ion-exchange studies were carried out for Mn 2+ ions in the presence of Ba 2+, Sr 2+ Cs + and Na + ions, and for Na + ions in the presence Ba 2+ and Mn 2+ ions, from 0.1 N chloride solutions. Single Particle Radioactive Tracer technique was employed, and the exchanger Dowex 5OW-X8 was used. The Nernst-Planck model, taking into account the diffusion processes both in the film and in the resin bead, was employed to analyse the data Resin-phase self-diffusion coefficients obtained from the isotopic exchanges in the homo-ionic systems, and liquid-phase diffusion coefficients calculated from limiting ionic conductance data, were used. The computer results agreed well with the experimental data for the following cases: (i), Na + exchange in the presence of Ba 2+ and Mn 2+ ions; (ii), Mn 2+ ion in the presence of Na+ ions; and (iii), Mn 2+ exchange in the presence of Ba 2+, Sr 2+ and Cs + ions at higher fractions of Mn 2+ ions. However, lower values of diffusion coefficient of Mn 2+ ions could correlate the data with smaller fractions of Mn 2+ ions. It has been shown ibat resinphase diffusion mechanism of homovalent ions under similar environments is similar.

Freezing Potentials and Currents in Potassium Fluoride Solutions at Constant Growth Rates

The Workman–Reynolds effect was studied in the growth of ice on a monocrystalline seed, at constant growth rates and under steady-state conditions, from KF solutions at concentrations from 2 × 10−5 to 10 × 10−5 Normal. Freezing potentials increased with growth rate to a maximum of 12 V at 11.2 μm/s. Discharge currents through a 105 Ω shunt generally increased with freezing rate until a maximum of 1.5 μA at 11.2 μm/s. The charge transfer decreased with growth rate to 200 μC at 10.3 μm/s and then reached a maximum of 850 μC at 11.2 μm/s. Apparent diffusion coefficients of about 2 × 10−3 mm2/s increased slowly with growth rate until a rapid increase began, apparently associated with interface breakdown. Distribution coefficients of the order of 10−3, calculated from a criterion for constitutional supercooling, increased with concentration. Parameters for LeFebre’s model of the interface showed an interface thickness of about 6 mm, an interface capacitance near one-half pF/mm2, and an interface resistance of about 6 × 104 Ω/mm2. Several empirical relations between these quantities were disclosed. Comparison with values obtained for KC1 solutions with the same freezing cell shows that the KF solutions yielded higher values of freezing potential, charge transfer, and distribution coefficient, and lower values of diffusion coefficient, interface capacitance, and interface resistance.

Freezing Potentials and Currents in Potassium Fluoride Solutions at Constant Growth Rates

The Workman–Reynolds effect was studied in the growth of ice on a monocrystalline seed, at constant growth rates and under steady-state conditions, from KF solutions at concentrations from 2 × 10−5 to 10 × 10−5 Normal. Freezing potentials increased with growth rate to a maximum of 12 V at 11.2 μm/s. Discharge currents through a 105 Ω shunt generally increased with freezing rate until a maximum of 1.5 μA at 11.2 μm/s. The charge transfer decreased with growth rate to 200 μC at 10.3 μm/s and then reached a maximum of 850 μC at 11.2 μm/s. Apparent diffusion coefficients of about 2 × 10−3 mm2/s increased slowly with growth rate until a rapid increase began, apparently associated with interface breakdown. Distribution coefficients of the order of 10−3, calculated from a criterion for constitutional supercooling, increased with concentration. Parameters for LeFebre’s model of the interface showed an interface thickness of about 6 mm, an interface capacitance near one-half pF/mm2, and an interface resistance of about 6 × 104 Ω/mm2. Several empirical relations between these quantities were disclosed. Comparison with values obtained for KC1 solutions with the same freezing cell shows that the KF solutions yielded higher values of freezing potential, charge transfer, and distribution coefficient, and lower values of diffusion coefficient, interface capacitance, and interface resistance.