Mean Potential Difference Research Articles

Sustainable Energy Analysis of Nigerian Road Transportation Sector: Benchmarking against Global Trends

Sustainability of road transportation sector fuel exergy utilisation in Nigeria between 1990 and 2019 was examined and compared with the global trends in the same sector. Parameters used were exergy efficiency, depletion number, sustainability index and improvement potential. Petrol engines had the highest mean efficiency of 13.05% and heavy duty vehicles the lowest of 8.57%. Their respective mean depletion numbers were 0.8695 and 0.9143, while their mean sustainability index values were 1.1501 and 1.0937 respectively. However, petrol engines had the highest mean improvement potential of 2.07×1011 MJ and cars had the lowest value of 1.86×1010 MJ. When benchmarked against global values, petrol engines still had the highest mean potential difference value of 5.93×1010 MJ while cars had the lowest value of 6.02×109 MJ. Improvement potential values were largely influenced by exergy utilisation rates, the influence of which outweighed that of exergy efficiencies, of the different carriers.

Ion Release and Galvanic Corrosion of Different Orthodontic Brackets and Wires in Artificial Saliva

To investigate the galvanic corrosion of brackets manufactured by four different companies coupled with stainless steel (SS) or nickel-titanium (NiTi) wires in an artificial saliva solution. A total of 24 mandibular central incisor Roth brackets of four different manufacturers (American Orthodontics, Dentaurum, Shinye, ORJ) were used in this experimental study. These brackets were immersed in artificial saliva along with SS or NiTi orthodontic wires (0.016'', round) for 28 days. The electric potential difference of each bracket/ wire coupled with a saturated calomel reference electrode was measured via a voltmeter and recorded constantly. Corrosion rate (CR) was calculated, and release of ions was measured with an atomic absorption spectrometer. Stereomicroscope was used to evaluate all samples. Then, samples with corrosion were further assessed by scanning electron microscope and energy-dispersive X-ray spectroscopy. Two-way analysis of variance was used to analyze data. Among ions evaluated, release of nickel ions from Shinye brackets was significantly higher than that of other brackets. The mean potential difference was significantly lower in specimens containing a couple of Shinye brackets and SS wire compared with other specimens. No significant difference was observed in the mean CR of various groups (p > 0.05). Microscopic evaluation showed corrosion in two samples only: Shinye bracket coupled with SS wire and American Orthodontics bracket coupled with NiTi wire. Shinye brackets coupled with SS wire showed more susceptibility to galvanic corrosion. There were no significant differences among specimens in terms of the CR or released ions except the release of Ni ions, which was higher in Shinye brackets.

Effects of Lévy noise on the dynamics of sine-Gordon solitons in long Josephson junctions

.We numerically investigate the generation of solitons in current-biased long Josephson junctions in relation to the superconducting lifetime and the voltage drop across the device. The dynamics of the junction is modelled with a sine-Gordon equation driven by an oscillating field and subject to an external non-Gaussian noise. A wide range of α-stable Lévy distributions is considered as a noise source, with varying stability index α and asymmetry parameter β. In junctions longer than a critical length, the mean switching time (MST) from the superconductive to the resistive state assumes a value independent of the device length. Here, we demonstrate that this value is directly related to the mean density of solitons which move into or from the washboard potential minimum corresponding to the initial superconductive state. Moreover, we observe: (i) a connection between the total mean soliton density and the mean potential difference across the junction; (ii) an inverse behaviour of the mean voltage in comparison with the MST, with varying the junction length; (iii) evidence of non-monotonic behaviours, such as stochastic resonant activation and noise-enhanced stability, of the MST versus the driving frequency and noise intensity for different values of α and β; (iv) finally, these non-monotonic behaviours are found to be related to the mean density of the solitons formed along the junction.

Variations of cosmic ray muon flux during thunderstorms

Variations of the intensity of cosmic ray muons during thunderstorms are investigated. Linear and quadratic coefficients of regression of the muon flux with near-ground electric field are calculated and compared to the experimental data obtained with the Carpet air shower array in the Baksan Valley, North Caucasus. Based on correlations with the near-ground field, estimates are made of regression coefficients with the mean potential difference in the stratosphere, between the effective level of muon production and the ionosphere. It is shown that maximum observable muon effects (variations with amplitudes of 1%) correspond to a mean potential difference in the stratosphere of about 200 MV.

Angiotensin II receptors are expressed and functional in human esophageal mucosa

Only few studies have been devoted to the actions of the renin-angiotensin system (RAS) in the human gastrointestinal tract. The present study was undertaken to elucidate the expression and action of RAS in the human esophageal mucosa. Mucosal specimens with normal histological appearance were obtained from healthy subjects undergoing endoscopy and from patients undergoing esophagectomy due to neoplasm. Gene and protein expressions of angiotensin II (Ang II) receptor type 1 (AT(1)) and type 2 (AT(2)) and angiotensin-converting enzyme (ACE) were analyzed. In vivo functionality in healthy volunteers was reflected by assessing transmucosal potential difference (PD). Ussing chamber technique was used to analyze the different effects of Ang II on its AT(1) and AT(2) receptors. Immunoreactivity to AT(1) and AT(2) was localized to stratum superficiale and spinosum in the epithelium. ACE, AT(1), and AT(2) were found in blood vessel walls. Transmucosal PD in vivo increased following administration of the AT(1) receptor antagonist candesartan. In Ussing preparations mean basal transmural PD was -6.4 mV, epithelial current (I(ep)) 34 muA/cm(2), and epithelial resistance (R(ep)) 321 Omega.cm(2). Serosal exposure to Ang II increased PD as a result of increased I(ep), whereas R(ep) was constant. Ang II given together with the selective AT(1)-receptor antagonist losartan, or AT(2) agonist C21 given alone, resulted in a similar effect. Ang II given in presence of the AT(2)-receptor antagonist PD123319 did not influence PD, but I(ep) decreased and R(ep) increased. In conclusion, Ang II receptors and ACE are expressed in the human esophageal epithelium. The results suggest that AT(2)-receptor stimulation increases epithelial ion transport, whereas the AT(1) receptor inhibits ion transport and increases R(ep).

S1245 ROME III Subtyping Is Associated with Alterations in Intestinal Motility and Secretion, But Not with Sensitivity or Psychosocial Factors

Background: Visceral hypersensitivity, altered gastrointestinal motility and secretion, and psychosocial factors are considered to be of great importance for the symptom pattern in irritable bowel syndrome (IBS). The Rome III criteria propose subtyping of IBS patients based on stool form alone (Longstreth et al Gastroenterology 2006), but the association with the underlying pathophysiology is unknown. Aim: To evaluate the link between pathophysiological factors and Rome III subtyping. Methods: We included 129 IBS patients (96 females, 33 males; mean age 37 (19-67) years). The patients were subtyped according to the Rome III criteria based on one-week diaries, where the stool form (Bristol Stool Form scale) was reported. All patients underwent investigations to assess colonic motility (colonic transit time), small intestinal motility and secretion (antroduodenojejunal manometry with jejunal transmural potential difference (PD) measurement) and rectal sensorimotor function (rectal balloon distensions before and after meal intake). The patients also completed questionnaires to assess the severity of psychological, gastrointestinal and extraintestinal symptoms. Results: Fifty-five patients had IBS-D (diarrhea), 29 IBS-C (constipation), 11 IBS-M (mixed) and 34 IBS-U (unsubtyped). For the analyses M+U was combined into one group (“NonCNonD”). Colonic transit time differed between the subgroups (p<0.0001), with slower transit in IBS-C (1.8±2.9 (mean±SD) days), faster in IBS-D (1.0±1.4 days), and intermediate in the NonCNonD-group (1.4±2.0 days). There were also group differences in small intestinal motility, with higher contraction frequency in the fasted state (p<0.05), longer phase III duration (p<0.01) and faster propagation velocity of phase III (p<0.01) in IBS-D. The small intestinal secretion during phase III (mean PD × length of the secreting segment, calculated from duration and propagation velocity) also differed between the subtypes, with enhanced secretion in IBS-D (p<0.001). Also the mean fasted PD tended to be higher in IBS-D (p<0.05). Rectal sensitivity, compliance and the rectal tone response, as well as psychological or extraintestinal symptom severity was similar in the subtypes. The perceived severity of constipation (p<0.01) and diarrhea (p<0.01), but not other GI symptoms, also differed between the subtypes. Conclusion: Subtyping of IBS patients based on the stool form is associated with alterations small intestinal and colonic motility, as well as small intestinal secretion. However, other pathophysiological factors, as well as symptoms other than constipation and diarrhea, seem unrelated to the different Rome III-based IBS subtypes.

Electron and ion kinetics in magnetized capacitively coupled plasma source

One-dimensional particle-in-cell Monte Carlo collision simulations of magnetized argon plasmas in an asymmetric capacitively coupled plasma reactor are presented. At low pressure (10mTorr), electron kinetics are strongly affected by the magnetic field and transitions from nonlocal to local kinetic property occur with increasing magnetic field which are reflected in spatially resolved calculations of the electron-energy probability function. For high-energy electrons, the transition takes place when the energy-relaxation length is smaller than the system length. For low-energy electrons, however, the transition occurs when the electron-diffusion time scale in the energy space is shorter than the spatial-diffusion time scale in coordinate space. These observations are in agreement with experimental data and theoretical calculations deduced from the Boltzmann equation. The ion energy distribution function (IEDF) on the driven electrode changes from the ion-neutral collisional type to the ion-neutral collisionless type with increasing magnetic field strength. The maximum ion energy in the IEDF decreases and the angular spread in the ion angle distribution function slightly increases with increasing magnetic field strength. These changes are explained in terms of the ratio of the ion-transit time to rf frequency, the sheath length, and the mean potential difference between the driven electrode and the plasma. At high pressure (218mTorr), electron-neutral collisions disrupt electron gyromotion so that the effects of the magnetic field on electron and ion kinetics are greatly reduced.

Electrical potential difference between basal cell carcinoma, benign inflammatory lesions and normal tissue

Measurement of the resting electrical potential difference on the surface of the skin has been made on patients with suspected basal cell carcinoma. It was demonstrated that in fifty-five lesions from forty-nine patients, the mean electrical potential difference from thirty-six basal cell carcinomas was found to be +II mV, from nineteen benign inflammatory lesions it was found to be +2 mV, and from normal skin, contra-lateral to the lesions in both groups, it was found to be -3 mV. All the measurements are relative to a reference electrode placed under the tongue. The difference between the means for the inflammatory lesions and for the normal skin was found to be statistically insignificant, but the difference between these means and the mean potential difference for the basal cell carcinoma group was found to be highly significant (P less than 0-1%). However, the populations overlap to such an extent as to make the measurement, in its present form, useless as a diagnostic technique.

The Wulff Shape of Alumina: II, Experimental Measurements of Pore Shape Evolution Rates

The rate at which a facetted tetragonal cavity of nonequilibrium shape approaches a cubic equilibrium (Wulff) shape via surface diffusion was modeled. The shape relaxation rate of a facetted “stretched cylinder” was also modeled. For the first geometry, only an approximate solution based on linearizing the mean potential difference between the source and sink facets was obtained. For the stretched cylinder, both an approximate and an exact solution can be obtained; the approximate solution underestimates the evolution rate by a factor of ∼2. To assess the applicability of the models, nonequilibrium shape pores of identical initial geometry (∼20 μm × 20 μm × 0.5 μm) were introduced into (0001), {10[Onemacr]2}, {1120}, and {100} surfaces of sapphire single crystals using microfabrication techniques, ion‐beam etching, and hot pressing. The large (∼20 μm × 20 μm) faces of the pore are low‐index surfaces whose nature is dictated by the wafer orientation. A series of anneals was performed at 1900°C, and the approach of the pore shape to an equilibrium shape was monitored. The kinetics of shape evolution are highly sensitive to the crystallographic orientation and stability of the low‐index surface that dominates the initial pore shape. The measured variations of the pore aspect ratio were compared to those predicted by the kinetic model. The observations suggest that when the initial bounding surface is unstable, shape relaxation may be controlled by diffusion. However, surface‐attachment‐limited kinetics (SALK) appears to play a major role in determining the pore shape evolution rate in cases where the initial bounding surfaces have orientations that are part of the Wulff shape.

Conventional and modified nasal potential-difference measurement in cystic fibrosis.

Cystic fibrosis (CF) is associated with impaired ion transport across epithelial membranes and an increased transepithelial potential difference (PD) that can be measured in airway epithelium. The aim of this study was to investigate the diagnostic value of nasal PD in CF, and to test a modified approach to the measurement of this PD. The reproducibility and diagnostic sensitivity and specificity of nasal PD measurements were tested with the perfusion technique and with a simplified modification of the technique done with a novel, solid-state exploring electrode. With the perfusion method, basal PD values were different in CF patients (mean +/- SEM: -51.6 +/- 0.9 mV, n = 104) than in normal (-15.5 +/- 0.9 mV, n = 58, p < 0.01) subjects. CF patients with acute rhinitis or other nasal pathology had mean PD values that were intermediate between those of the patients and normal and disease-control groups (-28.3 +/- 1.2 mV, n = 40, p < 0.01, different from normal). The diagnostic sensitivity of the perfusion method for CF was 91.3%, and the specificity was 96.4%. PD measurements with the modified technique correlated highly with the results achieved with the perfusion method (r = 0.94, n +/- 158). The measurement of nasal PD effectively distinguishes CF from control subjects. Care must be taken in the interpretation of measurements made on acutely inflamed epithelium. The modified method was simpler than the conventional perfusion technique, and equally effective.

The mean electrostatic potential difference between liquid water and vacuum by MD simulation

A negative mean electrostatic potential relative to that of a vacuum exists in liquid water represented by the extended single point charge (SPC/E) model and can be computed by molecular dynamics simulations. The mean potential difference between the liquid phase and vacuum can also be estimated analytically from the charge distribution in the SPC/E water molecule with respect to its mass and force centers. Other models of water molecules are also discussed.

Composition dependence of discontinuousmagnetization in CuxFe3-xO4+δ

The spinel series CuxFe3-xO4 + δ, 0 ≤ δ ≤ 0.4 (where x = 0.2, 0.3, 0.4, 0.5, 0.6, 0.8 and 1.0) has been investigated by means of X-ray diffraction and Barkhausen jumps. Analysis of X-ray intensity data showed that this system separates into two phases at x < 1. The percentage of phase separation decreases with increasing copper content. The system shows a single phase at x = 1. The mean potential difference, VB, and the frequency, FB, of Barkhausen jumps were measured as a function of the magnetizing current. Addition of copper enhances the irreversible motion of domain walls. The sample with x = 1 shows the highest values of VB and FB. The potential energy of the walls increases with increasing copper content.

Effect of Oral Digoxin, Topical Ouabain and Salbutamol on Transepithelial Nasal Potential Difference in Patients with Cystic Fibrosis

1. Airway epithelium in cystic fibrosis is characterized by a defect in chloride secretion across the apical membrane and an increase in sodium absorption. The increased rate of sodium absorption can be inhibited in vitro by ouabain, a Na(+)-K(+)-ATPase inhibitor, and in cystic fibrosis patients the number and activity of nasal epithelial Na(+)-K(+)-ATPase pumps is increased. 2. We have performed a series of studies to determine whether drugs which modify airway epithelial Na(+)-K(+)-ATPase activity in vitro can modify nasal potential in cystic fibrosis patients in vivo. As transepithelial nasal potential difference measurements were used to study the effect of drug modulation of airway epithelial ion transport in vivo, the repeatability of the technique was first evaluated. In order to assess the effectiveness of the technique used for measuring nasal potential difference, a pilot study was carried out using topical amiloride, a drug which has previously been shown to inhibit airway epithelium sodium transport in vivo. We then studied the effects of ouabain and digoxin, two inhibitors of Na(+)-K(+)-ATPase, on nasal potential difference. 3. In study 1, nasal potential difference measurements were repeated on non-consecutive days in 20 patients with cystic fibrosis and 20 healthy individuals. Healthy subjects had a mean (SEM) potential difference value of -19.5 (0.9) mV with a 95% range for a single estimate of 75-133%. In patients with cystic fibrosis, the mean (SEM) potential difference was -40.4, (2.1) mV, with a 95% range for a single estimate of 74-136%.(ABSTRACT TRUNCATED AT 250 WORDS)

Scaling of transepithelial potential difference in the mammalian trachea

Tracheal epithelia of different mammalian species differ widely with regard to the relative rates of Na + absorption and Cl − secretion. However, the short circuit current, a measure of total ion transport, appears to be consistently greater in large than in small mammals. Thus, we hypothesized that the in vivo tracheal electrical potential difference (PD) would vary among species as a function of body mass (M). To test this hypothesis we measured PD in ten mammalian species that ranged 1000-fold in mass. The results in mV (mean ± SE, lumen negative) were: 11.4 ± 1.0 in mice; 11.6 ± 1.2 in gerbils; 12.9 ± 1.4 in rats; 19.3 ± 0.9 in guinea pigs; 27.2 ± 2.2 in ferrets; 23.0 ± 1.6 in cats; 27.0 ± 0.6 in rabbits; 32.5 ± 2.6 in dogs; 37.0 ± 1.9 in sheep; and 49.0 ± 3.3 in pigs. Log-log correlation analysis of mean PD (in mV) and M (in kg) yielded PD = 20.9 M 0.19 ( r = 0.96, P < 0.001). Analysis of published short circuit current (SCC, in μA/cm 2) data revealed a similar relationship: SCC = 38.2 M 0.21. Thus, the transepithelial electrical potential and active charge transport by the tracheal epithelium are allometric variables that may have direct physiological significance. These results raise questions regarding the importance of net osmotic solute and water transport across the tracheal epithelium.

Composition dependence of discontinuous magnetization in Ni1-xMgxFe2O4

The mean potential difference VB and the frequency FB of Bakhausen jumps were investigated for polycrystalline Ni1-xMgxFe2O4 where x=0, 0.2, 0.4, 0.8, 1.0. NiFe2O4 shows the lowest values of VB. The addition of Mg enhances the irreversible motion giving rise to higher values of VB and FB. When Mg content exceeds 0.4, the number of jumps begins to decrease. Mg addition affects the energetic situation of the domain walls.

Microstructure and Barkhausen jumps in an Ni-Cr eutectoid steel

The decomposition of austenite following the initial rapid formation of bainitic ferrite in a eutectoid steel containing nominally 1 wt.% Ni and 1 wt.% Cr isothermally transformed in the bainitic region of the time-temperature transformation diagram has been studied. The microstructure and kinetics were studied using both optical and electron microscopy. Also, the mean potential difference VB and the frequency FB of Barkhausen jumps were measured for various bainitic transformation products. Lower bainite with fine carbides shows the higher values of FB and VB. The formation of upper bainite with coarser carbides leads to a considerable decrease of FB and VB, while in the region of upper bainite and spiky pearlite FB and VB increase slightly. The relative amount of the eddy currents depends on the transformation products.

In vivo evidence of altered chloride but not potassium secretion in cystic fibrosis rectal mucosa

In cystic fibrosis, cyclic adenosine monophosphate-mediated chloride secretion is abnormal in respiratory, small intestinal, and rectal mucosa. Calcium-mediated chloride secretion is also aberrant in CF small intestinal mucosa in cystic fibrosis, in contrast to the respiratory epithelia, where it appears to be normal. To determine whether this disparity between calcium- and cyclic adenosine monophosphate-mediated chloride secretion exists in cystic fibrosis rectal mucosa in vivo, transrectal potential difference was measured in age-matched adult cystic fibrosis subjects (n = 8) and control subjects (n = 9) in response to 10-minute luminal perfusions of bethanechol (1 mmol/L) or theophylline (5 mmol/ L). In response to bethanechol, an initial (1-minute) negative change in potential difference (−1.4 ± 1.1 mV; mean ± SEM) was seen in control subjects, in contrast to a positive change in mean potential difference (+2.5 ± 1.0 mV) in cystic fibrosis subjects (control vs. cystic fibrosis, P < 0.05). After 1 minute, mean potential difference changes in both control and cystic fibrosis subjects were positive. Theophylline perfusion resulted in a significant (P < 0.01) difference in potential difference response between groups; at 10 minutes, the potential difference became more negative (−3.6 ± 1.4 mV) in control subjects and more positive in cystic fibrosis subjects (+3.9 ± 1.4 mV). To determine whether second messenger-mediated potassium secretion contributed to the observed potential difference changes in response to bethanechol and theophylline, studies were repeated in the presence of barium chloride, a known blocker of potassium conductance. In the control group, barium chloride significantly enhanced the theophylline-induced negative potential difference change (P < 0.05) and reduced the positive potential difference change seen with bethanechol alone. In subjects with cystic fibrosis, barium chloride completely abolished the previously seen positive potential difference change in response to either bethanechol or theophylline alone. These in vivo studies suggest that there is active potassium secretion in both control and cystic fibrosis rectal mucosa in response to cyclic adenosine monophosphate- and calcium-dependent secretagogues and that the magnitude of the potential difference changes attributable to barium-inhibitable potassium secretion is the same in cystic fibrosis and control subjects. In contrast, it appears that in cystic fibrosis rectal mucosa in vivo, calcium- as well as cyclic adenosine monophosphate-dependent chloride secretion is aberrant.

Energetics of OH − or H + dependent nitrate uptake by Catharanthus roseus cells: electrophysiological effects

The electrical potential across the plasmalemma and the tonoplast were recorded, in Catharanthus roseus cells, by pushing a glass microelectrode through a cell with the tip consecutively in the cell wall, the cytoplasm and the vacuole. The electrical potential difference between the cytoplasm and the external medium ( E CO) was about −71 mV and the mean potential difference at the tonoplast ( E VC) about +22 mV. In culture conditions, during the first two days following the transfer of the cells into a fresh medium, nitrate uptake by the cells was marked by a hyperpolarization of the plasmalemma (about −18 mV) and a simultaneous alkalinization of the external medium (1.3 pH units). Similar data were also obtained in short experiments (less than 10 min) with cells bathed in nitrate solutions (10 mM NaNO 3). Evidence for the existence of nitrate cotransport with H + or OH − as counterions at the plasmalemma is discussed.

Energetics of OH − or H + dependent nitrate uptake by Catharanthus roseus cells: Electrophysiological effects

The electrical potential across the plasmalemma and the tonoplast were recorded, in Catharanthus roseus cells, by pushing a glass microelectrode through a cell with the tip consecutively in the cell wall, the cytoplasm and the vacuole. The electrical potential difference between the cytoplasm and the external medium ( E CO) was about −71 mV and the mean potential difference at the tonoplast (E VC) about +22 mV. In culture conditions, during the first two days following the transfer of the cells into a fresh medium, nitrate uptake by the cells was marked by a hyperpolarization of the plasmalemma (about −18 mV) and a simultaneous alkalinization of the external medium (1.3 pH units). Similar data were also obtained in short experiments (less than 10 min) with cells bathed in nitrate solutions (10 mM NaNO 3). Evidence for the existence of nitrate cotransport with H + or OH − as counterions at the plasmalemma is discussed.

Determination of cell membrane resistance in cultured renal epithelioid (MDCK) cells: effects of cadmium and mercury ions

Previous studies have indicated that the cell membrane of Madin Darby Canine Kidney (MDCK) cells is hyperpolarized by a number of hormones and trace elements, in parallel with an enhancement of potassium selectivity. Without knowledge of the cell membrane resistance (Rm), however, any translation of potassium selectivity into potassium conductance remains equivocal. The present study was performed to determine the Rm of MDCK cells by cellular cable analysis. To this end, three microelectrodes were impaled into three different cells of a cell cluster; current was injected via one microelectrode and the corresponding voltage deflections measured by the other two microelectrodes. In order to extract the required specific resistances, the experimental data were analysed mathematically in terms of an electrodynamical model derived from Maxwell's equations. As a result, a mean Rm of 2.0 +/- 0.2 k omega cm2 and an intercellular coupling resistance (Rc) of 6.1 +/- 0.8 M omega were obtained at a mean potential difference across the cell membrane of -47.0 +/- 0.6 mV. An increase of the extracellular K+ concentration from 5.4 to 20 mmol/l depolarized the cell membrane by 16.2 +/- 0.5 mV and decreased Rm by 30.6 +/- 3.0%; 1 mmol/l barium depolarized the cell membrane by 20.1 +/- 1.1 mV and increased Rm by 75.9 +/- 14.3%. Omission of extracellular bicarbonate and carbon dioxide at constant extracellular pH caused a transient hyperpolarization (up to -60.4 +/- 1.4 mV), a decrease of Rm (by 75 +/- 4.5%) and a decrease of Rc (by 23.1 +/- 8.4%).(ABSTRACT TRUNCATED AT 250 WORDS)