Oxygen Transfer on Substituted ZrO2, Bi2O3, and CeO2 Electrolytes with Platinum Electrodes II. A-C Impedance Study

An equivalent electrical circuit that describes the electrode processes on different electrolytes, using porous Pt electrodes,is given. Diffusional processes are important and have to be presented by Warburg components in the circuit. Theoverall electrode process is rate limited by diffusion of atomic oxygen on the electrode surface for stabilized zirconia andsubstituted ceria (low PO2). On stabilized bismuth sesquioxide diffusion of atomic oxygen on the electrolyte surface is ratelimiting at high PO2 while at low PO2 another process, probably diffusion of electronic species in the electrolyte, is dominant.One of these processes plays a role too on substituted ceria at high PO2, where a charge transfer process is dominant. Theseresults are consistent with the mechanisms developed in part I of this paper

High oxygen ion conduction in sintered oxides of the Bi2O3---Ln2O3 system

The conditions leading to optimum conductivity of the Bi2O3---Ln2O3 system were investigated. The highest conductivity was found for Ln = Er or Tm. Ordering in the oxygen lattice was investigated using neutron diffraction. Correlations were found between the neutron diffraction data and the conductivity

Preparation and properties of new oxygen ion conductors for use at low temperatures

Two new systems, Bi2O3---Er2O3 and ZrO2---Y2O3(CaO)---Bi2O3 were investigated. The first system has a homogeneous cubic, fluorite phase between 17.5 and 45.5 mol % Er2O3 and can be sintered to densities near 95% at 1200 K. At temperatures between 700 K and 1000 K the highest value of the a.c. oxygen ion conduction in this system is twice as much as the highest value found in the literature. In the second system concentrations of 1–3 mol % Bi2O3 act as an excellent sintering aid for ZrO2---Y2O3 and ZrO2---CaO samples which can be sintered to densities higher than 95% at temperatures of 1350 K. During this procedure a liquid ZrO2---Bi2O3 phase exists from which Bi2O3 partly evaporates with increasing sintering time. The oxygen ion conduction is little affected by the Bi2O3-rich second phase. The influence of annealing procedures up to 1570 K on the conduction in the ZrO2---Y2O3---Bi2O3 system is small despite weight losses up to 4%

Effect of grain boundaries on the conductivity of high-purity ZrO2---Y2O3 ceramics

Grain boundary conductivities are determined by complex impedance measurements (1–106 Hz) on high-purity ceramics prepared by the alkoxide synthesis and on less pure ceramics obtained from a commercial powder. The grain size was varied systematically in the region 0.36–55 μm. The grain boundary conductivity is strongly influenced by the grain size, impurities and cooling procedure. The grain boundary conductivity increases linearly with the grain size for small grain sizes (0.3 to 2–4 μm) and is constant for larger grain sizes. The calculated specific conductivity of the grain boundary for pure materials is about 100 times smaller than that of the bulk. The grain boundary thickness was estimated to be 5.4 nm. The activation energy of the grain boundary conductivity is 7 kJ mole−1 higher than of the bulk

Structure and conductivity of pyrochlore and fluorite type solid solutions

High oxygen conductivities can be achieved in cation ordered LnxZrl-x=xO2-l/2x (Ln=Gd, Nd) solid solutions with pyrochlore (P) structure. High values of the pre-exponential factor σo are correlated with the degree of anion disorder in the 8b oxygen sublattice (neutron diffraction). The activation energy ΔH is lowered by cation ordering (F-P transition; effect of ) due to the occurence of a preferential diffusion path. Maximum oxygen conductivity is achieved in (1−x)Bi2O3−x Ln2O3 solid solutions with fluorite related δ-Bi2O3 structure for Ln=Er and x=0.20. Neutron diffraction measurements indicate the occurence of short range ordering in “Er-O units” with relative small interatomic distances at T < 820 K. This leads to an increased activation energy

Structure and ionic conductivity of B_i2O₃ substituted with lanthanide oxides

A neutron diffraction study was performed on (Bi2O3)O.80(Er2O3)0.20 in the temperature region of 300–1100 K. There is no long-range ordering of vacancies. It is concluded from diffuse scattering that at low temperatures short-range ordering appears, leading to the occurrence of relatively short Ln-O distances. At temperatures above 870 K the oxygen lattice disorders.\ud \ud In the low temperature region of Bi2O3-Ln2O3 solid solutions with the δ-Bi2O3 structure the activation energy of the conductivity is determined by the strength of the Ln-O band. In the high temperature region the energy necessary for oxygen ions to migrate through the tetrahedron planes plays a role

Lack of uniform diagnostic criteria for cervical radiculopathy in conservative intervention studies: A systematic review

Purpose: Cervical radiculopathy (CR) is a common diagnosis. It is unclear if intervention studies use uniform definitions and criteria for patient selection. Our objective was to assess the uniformity of diagnostic criteria and definitions used in intervention studies to select patients with CR. Methods: We electronically searched the Cochrane Controlled Trials Register, MEDLINE, EMBASE and CINAHL. Studies were included when evaluating conservative interventions in randomised clinical trials (RCTs) in patients with CR. Selection criteria and definitions for patients with CR were extracted and evaluated on their uniformity. Results: Thirteen RCTs were included. Pain was used as an inclusion criterion in 11 studies. Inclusion based on the duration and location of pain varied between studies. Five studies used sensory symptoms in the arm as inclusion crite

Toward biological pacing by cellular delivery of Hcn2/SkM1

Electronic pacemakers still face major shortcomings that are largely intrinsic to their hardware-based design. Radical improvements can potentially be generated by gene or cell therapy-based biological pacemakers. Our previous work identified adenoviral gene transfer of Hcn2 and SkM1, encoding a "funny current" and skeletal fast sodium current, respectively, as a potent combination to induce short-term biological pacing in dogs with atrioventricular block. To achieve long-term biological pacemaker activity, alternative delivery platforms need to be explored and optimized. The aim of the present study was therefore to investigate the functional delivery of Hcn2/SkM1 via human cardiomyocyte progenitor cells (CPCs). Nucleofection of Hcn2 and SkM1 in CPCs was optimized and gene transfer was determined for Hcn2 and SkM1 in vitro. The modified CPCs were analyzed using patch-clamp for validation and characterization of functional transgene expression. In addition, biophysical properties of Hcn2 and SkM1 were further investigated in lentivirally transduced CPCs by patch-clamp analysis. To compare both modification methods in vivo, CPCs were nucleofected or lentivirally transduced with GFP and injected in the left ventricle of male NOD-SCID mice. After 1 week, hearts were collected and analyzed for GFP expression and cell engraftment. Subsequent functional studies were carried out by computational modeling. Both nucleofection and lentiviral transduction of CPCs resulted in functional gene transfer of Hcn2 and SkM1 channels. However, lentiviral transduction was more efficient than nucleofection-mediated gene transfer and the virally transduced cells survived better in vivo. These data support future use of lentiviral transduction over nucleofection, concerning CPC-based cardiac gene delivery. Detailed patch-clamp studies revealed Hcn2 and Skm1 current kinetics within the range of previously reported values of other cell systems. Finally, computational modeling indicated that CPC-mediated delivery of Hcn2/SkM1 can generate stable pacemaker function in human ventricular myocytes. These modeling studies further illustrated that SkM1 plays an essential role in the final stage of diastolic depolarization, thereby enhancing biological pacemaker functioning delivered by Hcn2. Altogether these studies support further development of CPC-mediated delivery of Hcn2/SkM1 and functional testing in bradycardia models.Therapeutic cell differentiatio

Indications of Linkage and Association of Gilles de la Tourette Syndrome in Two Independent Family Samples: 17q25 Is a Putative Susceptibility Region

Gilles de la Tourette syndrome (GTS) is characterized by multiple motor and phonic tics and high comorbidity rates with other neurobehavioral disorders. It is hypothesized that frontal-subcortical pathways and a complex genetic background are involved in the etiopathogenesis of the disorder. The genetic basis of GTS remains elusive. However, several genomic regions have been implicated. Among them, 17q25 appears to be of special interest, as suggested by various independent investigators. In the present study, we explored the possibility that 17q25 contributes to the genetic component of GTS. The initial scan of chromosome 17 performed on two large pedigrees provided a nonparametric LOD score of 2.41 near D17S928. Fine mapping with 17 additional microsatellite markers increased the peak to 2.61 (P=.002). The original families, as well as two additional pedigrees, were genotyped for 25 single-nucleotide polymorphisms (SNPs), with a focus on three genes in the indicated region that could play a role in the development of GTS, on the basis of their function and expression profile. Multiple three-marker haplotypes spanning all three genes studied provided highly significant association results (P<.001). An independent sample of 96 small families with one or two children affected with GTS was also studied. Of the 25 SNPs, 3 were associated with GTS at a statistically significant level. The transmission/disequilibrium test for a three-site haplotype moving window again provided multiple positive results. The background linkage disequilibrium (LD) of the region was studied in eight populations of European origin. A complicated pattern was revealed, with the pairwise tests producing unexpectedly high LD values at the telomeric TBCD gene. In conclusion, our findings warrant the further investigation of 17q25 as a candidate susceptibility region for GTS