Semilogarithmic Research Articles

Ultraviolet, Did the Cell See It from the Side or the Bottom? Assessment and Modeling of UV Effects on Cultured Cells Using the CL-1000 UV-Crosslinker.

Numerous natural extracts and compounds have been evaluated for their ability to mitigate the adverse effects of ultraviolet (UV) overexposure. However, variability in the UV doses that trigger biological responses across studies likely arises from inconsistencies in UV exposure standardization. We hypothesize that these discrepancies are due to variations in culture plates and dishes. The UV dose (D) required to reduce cell viability by 50% differed by a factor of ten between 3.5 cm dishes and 96-well plates. Similarly, the EC50 dose for IL-6 release (D1/2) varied, potentially correlating with the surface area (S). UV exposure to wells with increasing height in 3.5 cm dishes resulted in a decrease in IL-6 release, suggesting that the greater the well height, the more it may influence UV exposure through reflection or shielding effects, thereby contributing to the physiological effects on the cells. To compare these differences among plates, we defined the height-to-diameter ratio (r). Analysis revealed a linear correlation between D1/2 and S in a log-log plot, and between D1/2 and r in a semi-log plot. From this, we defined two empirical indices σ and ρ for UV dose adjustment. A deductive model was also developed to derive a D' value that adjusts UV doses without requiring training. As with σ and ρ, the UV dose D was effectively adjusted using D' as well. These attempts suggest that D' offers a foundational framework for evaluating UVB effects on cultured cells.

Sodium Alginate/MXene-Based Flexible Humidity Sensors with High-Humidity Durability and Application Potentials in Breath Monitoring and Non-Contact Human-Machine Interfaces.

Flexible humidity sensors (FHSs) with fast response times and durability to high-humidity environments are highly desirable for practical applications. Herein, an FHS based on crosslinked sodium alginate (SA) and MXene was fabricated, which exhibited high sensitivity (impedance varied from 107 to 105 Ω between 10% and 90% RH), good selectivity, prompt response times (response/recover time of 4 s/11 s), high sensing linearity (R2 = 0.992) on a semi-logarithmic scale, relatively small hysteresis (~5% RH), good repeatability, and good resistance to highly humid environments (negligible changes in sensing properties after being placed in 98% RH over 24 h). It is proposed that the formation of the crosslinking structure of SA and the introduction of MXene with good conductivity and a high specific surface area contributed to the high performance of the composite FHS. Moreover, the FHS could promptly differentiate the respiration status, recognize speech, and measure fingertip movement, indicating potential in breath monitoring and non-contact human-machine interactions. This work provides guidance for developing advanced flexible sensors with a wide application scope in wearable electronics.

Minimal assay detects population-level senescence in the aquatic plant <i>Lemna minor</i>

At the population level, senescence occurs when older individuals have increased risk of death and reduced reproduction compared to younger individuals. We investigated senescence in the aquatic plant <i>Lemna minor</i> (common duckweed), an important species for plant senescence research. Our objectives were to (1) confirm or refute the presence of population-level senescence in this model species; (2) develop a minimal assay of senescence requiring only once-weekly data collection; and (3) test whether there were appreciable differences in senescence in plants grown in glass compared to polystyrene petri dishes, with an aim to reducing single-use plastic waste and long-term research materials costs. We found that weekly survival arced downward with age when viewed on a semi-log plot, and weekly production of descendants decreased with age, with both findings indicating population-level senescence that matched previous work using more frequent data-collection (per Objectives 1 and 2). Additionally, we found no noteworthy differences in senescence between plants grown in glass versus polystyrene petri dishes (per Objective 3). The use of weekly data collection could liberate personnel resources for other research-group functions, and could make the <i>Lemna</i> system suitable for senescence- or demography-education exercises. The use of glass dishes could reduce lab waste and expense.

In-depth quantitative and theoretical study of ambident electrophilies of 2-bromo-3-X-5-nitrothiophenes

As part of our continuing studies into the electron deficient nature of five-membered ring heterocycles, specifically 2‑methoxy-3-X-5-nitrothiophenes and 3-X-5-nitrothiophene, we report here a kinetic study of σ-complexation reactions involving 2‑bromo-3,5-dinitrothiophene 1 and various nitroalkyl anions in aqueous solution at 20 °C. Theoretical calculations at the density functional theory (DFT) level were performed to confirm the proposed mechanism. From the previously reported nucleophilicity parameters N and sN for the nucleophiles 2 and the derived second-order rate constants, the electrophilicity parameter (E) at the C-4 position of thiophene 1 was quantified according to the linear free enthalpy relationship log k (20 °C) = sN (E + N). Mayr's approach accurately predicted the rate constants for the reactions of this thiophene 1 with a series of para-substituted phenoxide anions in water at 20 °C. A reasonable correlation between calculated global electrophilicity index ω values and experimental electrophilic reactivities was observed and discussed.

The biodemography of human aging (Gompertz-Makeham law) applied to surgical mortality modelling: a retrospective national cohort study.

The Gompertz-Makeham law describes a characteristic pattern of mortality in human populations where death rate is near constant between age 18 and 30 years (Makeham's Law) and rises exponentially thereafter (Gompertz Law). This pattern has not been described in surgical populations, but if true, would have important implications for understanding surgical risk and design and interpretation of surgical risk models. The aim of this study was to determine if the Gompertz-Makeham law applies to perioperative mortality risk and the conditions under which it may apply. We examined the relationship between age and 1-month postoperative all-cause mortality risk in a 10-year New Zealand administrative dataset comprising of 5,615,100 surgical procedures from 2007 to 2016. The dataset includes patient and surgical factors including procedures, American Society of Anesthesiologist's physical status score (ASA-PS), diagnoses and other relevant details. Semi-logarithmic graphs of mortality risk and age were plotted. Linear regression models were fitted, with regression line slope and Pearson's correlation coefficient calculated. The primary outcome occurred in 114,782 (2.0%) of 5,615,100 included participants. The Gompertz-Makeham law seems to apply to the national surgical population as a whole (slope = 0.0241, R2 = 0.971). The law applies in all subgroups studied including sex, ASA-PS, surgical acuity, surgical severity category, cancer status and ethnicity (slopes 0.0066 to 0.0307, R2 0.771 to 0.990). Important interactions were found between age, mortality risk and three high risk groups (cancer diagnosis, ASA-PS 4-5 and high surgical severity). The Gompertz-Makeham law seems to apply in a national cohort of surgical patients. The inflection point for increased 1-month risk is apparent at age 30 years. A strict exponential rise in mortality risk occurs thereafter. This finding improves our understanding of surgical risk and suggests a concept-driven approach to improve modelling of age and important interactions in future surgical risk models.

Assessment of thermal and physicochemical properties of mechanic village soils derived from two different geological formations in Ogun State, Nigeria

This study assessed and compared selected soil properties, oil and grease content, and thermophysical parameters of sandy loam soils from two representative automobile mechanic village (MV) on two different geological formations in Ogun State, Nigeria. The two locations: Abeokuta and Sagamu are situated on a basement complex and Cretaceous-sedimentary formations, respectively. Ten sample points were established on each MV. Physico-chemical and in-situ thermal properties were measured using standard methods and KD2 Pro thermal analyzer, respectively. Three different regression models (linear, semi-log and double-log) were generated for the prediction of thermal conductivity ( λ s ) and specific heat capacity ( C s ). Topsoils in both MVs are slightly acidic to neutral, with an average oil and grease content > 100 mg/kg. Results of thermophysical parameters revealed that the average λ s values in MV soils of basement complex and sedimentary backgrounds were 1.656 and 1.988 W/mK, respectively. The average C s values in Abeokuta and Sagamu MV soils are 2.295 and 3.043 MJ/m3K, respectively. The regression analysis showed that the double log model performed better than both linear and semi log models for predicting λ s at both locations. All the tested regression models have good prediction effects on C s at location within cretaceous sedimentary, whereas linear and double-log models proved feasible for predicting C s at location underlain by basement complex.

Additional applications of the Lambert W function to solid state physics

Analytical solutions are always desirable in physics for the sake of mathematical exactness and physical insight. In this study, I obtain closed-form analytical expressions for various physical quantities taken from solid state physics. More precisely, I derive analytical expressions in terms of the Lambert W function for the work function and the field-enhancement factor of a field emitting material from the Fowler–Nordheim equation. Additionally, I derive similar analytical expressions for the localization length and the density of states in amorphous semiconductors from the Mott hopping conductivity. Similarly, I also derive analytical formulae based on the Lambert W function to compute the extrinsic-intrinsic transition temperature in a partially compensated semiconductor and the Kondo exchange coupling constant. All the obtained results are exact and explicit. Moreover, some of them allow a direct determination of some physical quantities of interest compared to their indirect determination from semi-logarithmic experimental plots. The findings of this paper are accessible and suitable for students enrolled in graduate solid state physics courses.

Factors associated with cost of adverse events in the intensive care unit: an economic evaluation performed in Bogotá, Colombia

BackgroundThe costs of adverse health events represent a significant burden of disease. Management of these adverse events also entails high costs to healthcare systems, reaching up to US$110 516.25 in...

Flexural fatigue behavior of ultra-high performance fiber reinforced concrete

Even though UHPFRC has been extensively utilized in infrastructures owing to its excellent mechanical properties, its fatigue behavior remains unclear because related research is very limited. In this study, the fatigue characteristics of UHPFRC were investigated using a four-point bending experiment. In this study, the fatigue characteristics of UHPFRC were investigated using a four-point bending experiment. To determine the fatigue load conditions, static tests were conducted at different loading speeds and ages before, during, and after the fatigue tests. The obtained mechanical properties exhibited a clear dependence on loading rate and age duration. Consequently, a loading frequency of 3 Hz, which is close to that experienced in real infrastructures, was employed in the fatigue tests. A linear S-N relation with a 0.87 fatigue endurance limit was obtained on a semi-logarithmic scale. Additionally, the fatigue life showed a close relationship with the initial cycle deformation. Correspondingly, threshold values of deformation indicators were proposed for predicting the occurrence of fatigue failure. Furthermore, a linear positive relationship was found between the density of multiple fine cracks and fatigue life, based on post-fatigue crack measurements using a microscope. The relatively narrow crack width compared to other cementitious composites demonstrated UHPFRC's superior resistance to corrosion factors. Consistent with the linear S-N relation, the structural degradation appears to be governed by a fiber slippage-to-pull mechanism, as no fiber rupture was observed.

The influence of self-assembled particle layer on particle collision properties

Interactions between particle and particle layers are fundamental in modeling deposition processes. The complex mechanical behaviors of these layers pose significant challenges in precisely predicting the rebound characteristics of incident particle, especially at the micron and nanoscale. Very few related experimental studies have been reported in this area. To better control the structure of particle layers and offer a path to more systematic research, this study introduces the particle self-assembly method, combined with high-speed imaging technology, to investigate the influence of particle monolayer, their diameters, and impact velocity on critical capture velocity (vcr), normal coefficient of restitution (COR), and angle deflection of incident particles. Results indicate that self-assembled particle layers remain stable within an impact velocity range and experimental data within this stable range exhibit good repeatability. These layers significantly enhance kinetic energy dissipation. A semi-logarithmic plot revealed a negative linear relationship between vcr and particle size ratio. The effect of particle layer on COR depends on particle layer diameter and impact velocity. Specifically, the dissipation of particle layer diminishes and approaches zero for smaller layer particles (0.5 μm), but increases and stabilizes for larger particles (2 μm). Moreover, statistical results indicate that angle deflection decreases as particle size ratio increases, aligning with a power-law relationship predicted by Monte Carlo simulations. Overall, this study presents a novel method for understanding micro and nano particle layers' influence on incident particle dynamics.

Aboveground biomass estimation models for Tectona grandis Linn f. plantation in Nnamdi Azikiwe University, Awka, Nigeria

Tree biomass is considered a useful indicator of structural and functional attributes of forest ecosystems across a wide range of environmental conditions. The aboveground biomass refers to the living vegetation above the soil, including stem, stump, branches, bark, seeds, and foliage. Teak (Tectona grandis Linn f.) is a popular exotic tree species in Nigeria; it is widely grown in both large scale and small community woodlots. The objective of this study was to develop models for estimation of biomass content of Teak plantation in Nnamdi Azikiwe University, Awka, Nigeria for sustainable management. Data on the diameter at breast height (D) and total height (H) of all teak stands in the plantation were recorded. Non-destructive method using an existing equation was used to estimate the aboveground biomass (AGB) of the individual stands from stump diameter. The Data was subjected to descriptive statistics, bivariate correlation analysis and fitted to six (6) linear regression functions. A total of 295 trees were measured with mean AGB of 18.61 kg. Out of the AGB prediction models developed for the study area, the Semi Log 3 (B5) model had the best predictive ability; with the highest adjusted coefficient of determination (0.984) and the lowest standard error of estimate (0.308), and Akaike information criterion (-690.974). Model B5 (B=0.764+0.764D-0.105lnH) is therefore recommended for future inventory and management of the plantation.

Foreign Direct Investment Inflows into SAARC Countries: Trend Analysis

The study examines the relationship between institutional quality and FDI inflows in SAARC nations from 1981 to 2020. It employs Simple Linear and Semi log linear regression to draw conclusions. The findings indicate that corruption, political stability, government effectiveness, and GDP per capita have a positive and statistically significant influence on FDI inflows. The Semi log linear regression results show that all estimates of government effectiveness, GDP per capita, and trade openness are positive and statistically significant. This research suggests that institutional quality is important for the growth of FDI inflows. As a result, policymakers should prioritize effective institutional reforms to create a favorable investment environment and attract FDI inflows in SAARC countries.

Reactivity of diethyl benzylidenemalonates with secondary cyclic amine dimers in acetonitrile: Structure-reactivity relationships and mechanism

We report on a kinetic study for the nucleophilic addition reactions of diethyl 4-X-substituted benzylidenemalonates 1a-c (X = N(CH3)2, OCH3 and CH3) with N-nucleophiles, such as morpholine 2a, piperidine 2b and pyrrolidine 2c by UV–vis spectroscopy in acetonitrile solution at 20 °C. The Hammett plots demonstrate much better linear correlations with σp+ constants than with σp constants. These results are best interpreted in terms of ground state stabilization through resonance interactions between the electron-donating substituent and the CO2Et group. The effect of amine basicity on the reaction rate was examined quantitatively, leading to linear correlations with high βnuc values in the 0.82–0.93 range. The origin of the abnormally high βnuc values was interpreted in terms of dimer mechanism. Finally, with the help of our new proposed linear free energy relationship log k1K (20 °C) = sN (E + N) + log K, the stability of the dimer amines (K) have been evaluated from the measured apparent second-order rate constant (k1K) and the previously reported E, N and sN parameters of the employed electrophiles 1a-c and nucleophiles 2a-c. Additionally, a complementary theoretical study utilizing Density Functional Theory (DFT) with the B3LYP/6-311g(d,p) method was conducted in acetonitrile. An attempt is made to establish the correlation between equilibrium constant and stabilization energy the studied systems.

Characterization of X-ray Beam for Half and Quarter Value Layers

Introduction: The aim of this work is to assess the penetrating ability of an X-ray beam through a specific material, in conditions of narrow-beam geometry. Materials and Methods: During the experiment, samples were switched with the X-ray tube turned off, and the primary intensity of the unshielded X-ray beam (fixed 2.5mm shielding) was measured. Parameters were kept constant throughout, and the electrometer was used to stabilize the readings. Subsequent measurements aimed to determine the Half-Value Layer (HVL) and Quarter-Value Layer (QVL) by interpolating various sample slices to achieve intensity values of I/2 and I/4, respectively. The data were used to plot and analyze HVL and QVL graphs, providing insights into the attenuation properties of the X-ray beam through different materials. Findings of the result: The primary findings indicated that the initial unshielded X-ray beam intensity, with parameters set to 37.5 kV and 40 mA, provided a stable baseline measurement. The results showed a consistent decrease in intensity with increased sample thickness, confirming the exponential attenuation of X-rays. The HVL was determined by identifying the sample thickness that reduced the initial intensity by half, and the QVL by the thickness reducing it to one-fourth. The experimental data closely followed theoretical predictions, with HVL and QVL values providing a quantitative measure of the material's attenuation properties. Conclusion: Graphical analysis of the results demonstrated clear linear relationships on a semi-logarithmic scale, validating the accuracy of the measurement process and the reliability of the electrometer readings. These findings contribute to a better understanding of X-ray attenuation in different materials, which is crucial for various applications in medical physics and radiography.

Correlation of hormone receptor positive HER2-negative/MammaPrint high-2 breast cancer with triple negative breast cancer: Results from gene expression data from the ISPY2 trial.

573 Background: A subset of Hormone Receptor positive (HR+), HER2 negative (HER2-) breast cancers (BCs) classified by the MammaPrint (MP) assay as High-2 (MP-H2) show clinical behavior similar to triple-negative (TN) BC. The aim of this analysis was to assess molecular similarities between the HR+/HER2-/MP-H2 (HR+/MP-H2), HR+/HER2-/MP-High-1 (HR+/MP-H1), and TN/MP-H2 (TN/MP-H2) BCs. Methods: Gene expression data used for this analysis [GEO GSE194040] was derived from pre-treatment samples of the I-SPY2 trial, which is an ongoing multicentric randomized Phase II neoadjuvant platform trial for high-risk stage II or III BC. Six hundred eighty-four pretreatment samples were included in this analysis: 274 corresponded to HR+/MP-H1, 105 to HR+/MP-H2, and 305 to TN/MP-H2, accounting for 7 experimental plus a control arm. We used principal component and distance analyses, differentially expressed genes (analysis performed for pairwise comparisons of the 3 subtypes, a linear model, log fold-change and moderated-t p-values relative to a minimum fold-change threshold of fc = 1.5), gene set enrichment analysis using KEGG and GO, and Ingenuity Pathway Analysis, as well as 32 previously defined qualifying biomarkers to study similarities in biology between the subgroups. Results: On principal component and distance analyses, results reveal close similarity between HR+/MP-H2 and TN/MP-H2 indicating shared transcriptomic features. Gene expression analysis revealed that HR+/MP-H2 tumors resemble TN/MP-H2 more than HR+/MP-H1 cancers. Differential gene expression analysis revealed that HR+/MP-H2 and TN/MP-H2 cancers presented only two differentially expressed genes, compared to HR+/MP-H1 and HR+/MP-H2, which presented 577 differentially expressed genes. Upon pathway analysis, HR+/MP-H1 cancers presented the most significant upregulation in the glucocorticoid receptor signaling, DHCR24, and HOTAIR pathways, compared to HR+/MP-H2 cancers. Furthermore, HR+/MP-H2 and TN/MP-H2 shared enrichment of DNA repair and cell cycle pathways. In addition, various biomarkers were analyzed, and among the most representative shared biomarkers for HR+/MP-H2 and TN/MP-H2 were immune features, higher proliferation, and a lower expression of ESR1 co-expressed genes as compared to HR+/MP-H1 cancers. The rates of pathologic complete response were 41% for TN/MP-H2, 31% for HR+/MP-H2, and 11% HR+/MP-H1 cancers among all included patients. Conclusions: A subset of HR+ cancers defined by MP-H2 status closely resemble TN in molecular and clinical features. The similarity of pCR rates for MP-2 observed within either HR+/HER2- and TN is supported by our findings of similarity of active biology between HR+/MP-2 and TN/MP-2. These findings have implications for understanding the biology of HR+/MP-H2 BCs and optimizing treatment strategies.

Pixel Screening in Lifetime-Based Temperature Mapping Using β-NaYF4:Nd3+,Yb3+ by Time-Gated Near-Infrared Fluorescence Imaging on Deep Tissue in Live Mice.

Near-infrared fluorescence (NIRF) thermometry is an emerging method for the noncontact measurement of in vivo deep temperatures. Fluorescence-lifetime-based methods are effective because they are unaffected by optical loss due to excitation or detection paths. Moreover, the physiological changes in body temperature in deep tissues and their pharmacological effects are yet to be fully explored. In this study, we investigated the potential application of the NIRF lifetime-based method for temperature measurement of in vivo deep tissues in the abdomen using rare-earth-based particle materials. β-NaYF4 particles codoped with Nd3+ and Yb3+ (excitation: 808 nm, emission: 980 nm) were used as NIRF thermometers, and their fluorescence decay curves were exponential. Slope linearity analysis (SLA), a screening method, was proposed to extract pixels with valid data. This method involves performing a linearity evaluation of the semilogarithmic plot of the decay curve collected at three delay times after cutting off the pulsed laser irradiation. After intragastric administration of the thermometer, the stomach temperature was monitored by using an NIRF time-gated imaging setup. Concurrently, a heater was attached to the lower abdomens of the mice under anesthesia. A decrease in the stomach temperature under anesthesia and its recovery via the heater indicated changes in the fluorescence lifetime of the thermometer placed inside the body. Thus, NaYF4:Nd3+/Yb3+ functions as a fluorescence thermometer that can measure in vivo temperature based on the temperature dependence of the fluorescence lifetime at 980 nm under 808 nm excitation. This study demonstrated the ability of a rare-earth-based NIRF thermometer to measure deep tissues in live mice, with the proposed SLA method for excluding the noisy deviations from the analysis for measuring temperature using the NIRF lifetime of a rare-earth-based thermometer.

Shear rate and roughness effect on clay-steel interface strength properties in CU and CPD drainage conditions

Based on the concept of the preformed failure plane, this paper conducted a series of clay-interface tests using a modified triaxial apparatus that can directly measure the interface pore pressure, to investigate the shear rate and interface roughness effect on the deviator stress, interface excess pore pressure, interface stress path, and interface friction angle in both consolidated undrained (CU) and consolidated partially drained (CPD) interface drainage conditions. In general, the specimen with the clay-steel interface had a lower shear strength than the pure clay specimen under the same testing conditions. In CU tests, the total and effective interface friction angles increase approximately linearly with the shear rate in the semi-logarithmic scale, while in CPD tests, both the total and effective interface friction angles decrease with increasing shear rate. Moreover, the increased surface roughness is found to enhance the interface shear strength and the maximum interface pore pressure at a given shear rate and confining pressure. In CU tests, both the normalized efficiency parameter E and the corresponding interface friction angle increase with the average roughness (Ra) in a logarithmic relationship, but it is difficult to describe the positive correlation perfectly in CPD tests.

DETERMINANTS AND IMPACT OF PUBLIC EXPENDITURE IN ODISHA

The theoretical framework and rationale of the study assess the most important fiscal parameter of the state of Odisha i.e., Expenditure parameter. As we know, aggregate of the expenditure of the state consists of Revenue expenditure and Capital expenditure, among which the largest share is contributed by Revenue expenditure. The paper highlights the responsiveness of expenditure to the automatic change in NSDP Elasticity approach, position of odisha among the 18 major non-special category states in terms of infrastructural development, bank credit, factory employment, level of urbanisation etc. and also examine the causative relationship between SDP and different expenditure variables in Odisha. The study is based on secondary source of data for the State from different government publications, Budget documents, Finance Accounts etc. The paper used different methodologies for analysis, which includes simple statistical techniques such as, ratio, percentage, and also Regression Analysis to estimate growth. In this regard models like, semi log, multiple regression, correlation, VAR models are used to analyse the time series data from 1980-81 to 2014-15 on revenue and capital expenditure of state finances . Apart from that to show the response of revenue expenditure to the automatic change in NSDP, Elasticity approach is utilized. The major results of the study are that higher growth in total expenditure in period t-1 leads to higher growth of SDP in period t. The same result holds only in case of growth of Total Non-Plan Expenditure. The results of VAR Granger Casualty Test are similar to the VAR Model excepting that Total Non-Plan Expenditure is found independent of SDP and there is also independence of SDP from Total Non-Plan Expenditure. KEY WORDS: budget, capital, elasticity, finance, grants, growth, NSDP, expenditure, VAR

On the Voltage Dependent Series Resistance, Interface Traps, and Conduction Mechanisms in the Al/(Ti-doped DLC)/p-Si/Au Schottky Barrier Diodes (SBDs)

In this study, Al-(Ti:DLC)-pSi/Au Schottky barrier diode (SBD) was manufactured instead of conventional metal / semiconductor (MS) with and without an interlayer and then several fundamental electrical-characteristics such as ideality factor (n), barrier height B series and shunt resistances (Rs, Rsh), concentration of acceptor atoms (NA), and width of depletion-layer (Wd) were derived from the forward-reverse bias current/voltage (I-V), capacitance and conductance as a function of voltage (C/G-V) data using various calculation-methods. Semi logarithmic IF-VF plot shows a linear behavior at lower-voltages and then departed from linearity as a result of the influence of series resistance/Rs and organic-interlayer. Three linear regions can be seen on the double-logarithmic IF-VF plot. with different slopes (1.28, 3.14, and 1.79) in regions with low, middle, and high forward bias, which are indicated that Ohmic-mechanism, trap-charge-limited-current (TCLC) mechanism, and space-charge-limited-current (SCLC) mechanism, respectively. Energy dependent surface states (Nss) vs (Ess-Ev) profile was also obtained from the Card-Rhoderick method by considering voltage-dependence of n and B and they were grown from the mid-gap energy up to the semiconductor's valance band (Ev). To see the impact of Rs for 1 MHz, the measured C/G-V graphs were amendment. All results are indicated that almost all electrical parameters and conduction mechanism are quite depending on Rs, Nss, and calculation method due the voltage dependent of them.

Effect of pH on primary and secondary crack propagation in sandstone under constant stress (creep) loading

Time-dependent, chemically assisted crack propagation behavior in rocks is fundamental to understanding the long-term stability of civil engineering structures. In this study, we investigated the propagation of primary and secondary cracks in macrofractured sandstone in distilled water (pH = 5.6) and in an aqueous solution of hydrochloric acid (HClaq, pH = 1.82) using digital image correlation (DIC), comparing the results to those from experiments performed in air. Results show that for the macrofracture angles γ = 0 and 90°, the nucleation position r of the primary crack is not affected by pH, and always occurs at the fracture tip (r = 0) and fracture center (r = 1), respectively. For γ = 30, 45, and 60°, r increases quasi-linearly with the increase of γ in semi-log plots, and an increase in pH moves the primary crack away from the fracture tip. For a given γ, an increase in pH produces an increase in the kink angle k1 of the secondary crack. The influence of pH on secondary crack propagation is most pronounced at high γ values. As the pH increases, the location of the secondary cracks gradually turns counterclockwise with a decreasing swing range, from 37° at pH 1.82–35° at pH 5.6. The secondary crack is inclined at a maximum of 30° and 32° to the maximum principal stress direction at pH 1.82 and pH 5.6, respectively. Right-lateral shear secondary cracks with well-developed tensile tail fractures are more prevalent in higher pH environments. The comparison with dry experiments indicates that distilled water is more aggressive than HClaq. The significant loss of calcium ions in distilled water and the reduction of large pore volume fraction in HClaq are considered the main reasons for the deterioration of the pH effect.