Pre-exponential Factor Research Articles

The work to swing limbs in humans versus chimpanzees and its relation to the metabolic cost of walking

Compared to their closest ape relatives, humans walk bipedally with lower metabolic cost (C) and less mechanical work to move their body center of mass (external mechanical work, WEXT). However, differences in WEXT are not large enough to explain the observed lower C: humans may also do less work to move limbs relative to their body center of mass (internal kinetic mechanical work, WINT,k). From published data, we estimated differences in WINT,k, total mechanical work (WTOT), and efficiency between humans and chimpanzees walking bipedally. Estimated WINT,k is ~ 60% lower in humans due to changes in limb mass distribution, lower stride frequency and duty factor. When summing WINT,k to WEXT, between-species differences in efficiency are smaller than those in C; variations in WTOT correlate with between-species, but not within-species, differences in C. These results partially support the hypothesis that the low cost of human walking is due to the concerted low WINT,k and WEXT.

Kinetic analysis and dosimetric characteristics of the thermoluminescent glow curve of aquamarine (Be3Al2(SiO3)6:Fe)

Kinetic analysis of the thermoluminescent (TL) glow curve of aquamarine, a cyan variety of beryl (Be3Al2(SiO3)6), is reported. Samples were irradiated at room temperature using a90Sr/90Y β source at a rate of 0.10 Gy-1. Measurements made at 1 °C/s after irradiation from 1 to 100 Gy show a high intensity peak at 75 °C followed by three secondary peaks at 115, 189 and 302 °C respectively. The dose response of the high intensity peak (called the main peak) is linear within the first 20 Gy, but tends towards sub-linearity as the dose is close to 100 Gy. The signal decays with the time delay between irradiation and reading. It decays about 14% of its initial value, 600 s after irradiation. Reproducibility analysis shows that the material reproduces its response under identical experimental conditions with an uncertainty of 0.8% after 10 Gy beta dose irradiation. The kinetic analysis of the TL glow curve was carried out using the curve fitting method. The results show that the main peak follows first order kinetics, its activation energy is of the order of 1 eV and the frequency factor is between 1012 and 1014 s−1, while some secondary peaks follow general order kinetics.

Are Kidneys Affected by SARS-CoV-2 Infection? An Updated Review on COVID-19-Associated AKI.

Human kidneys are an important target of SARS-CoV-2 infection, and many renal abnormalities have been found in patients with SARS-CoV-2 infection, including proteinuria, hematuria, and acute kidney injury. Acute kidney injury is now considered a common complication of COVID-19, and the epidemiology of AKI in SARS-CoV-2-infected patients continues to be controversial. We have carried out a narrative review to evaluate the frequency and risk factors for AKI among patients hospitalized due to COVID-19, and the latest surveys on this topic have been included. The mechanisms by which AKI occurs in COVID-19 patients have also been reviewed. Multiple risk factors for the development of AKI in patients with SARS-CoV-2 infection have been identified; these have been classified in various groups (management and background factors, among others). SARS-CoV-2 targets the kidneys by indirect activity, but SARS-CoV-2 infects tubular epithelial cells and podocytes. We retrieved 24 reports (n = 502,593 unique patients with SARS-CoV-2 infection) and found an incidence of AKI of 31.8% (range, 0.5% to 56.9%). Only a minority (n = 2) of studies had a prospective design. We found that the AKI risk was greater in SARS-CoV-2 patients who underwent in-hospital deaths vs. those who survived; the summary estimate of the unadjusted RR of AKI was 2.63 (95% CI, 2.37; 2.93) (random-effects model). A stratified analysis showed that the incidence of AKI was greater in those reports where the frequency of COVID-19-positive patients having comorbidities (diabetes mellitus, arterial hypertension, and advanced age) was high. The unadjusted relative risk (aRR) of AKI was greater in SARS-CoV-2 patients who underwent ICU admission vs. those who did not; the pooled estimate of AKI risk was 2.64 (95% CI, 1.96; 3.56) according to the random-effects model. AKI is a common complication of hospitalized SARS-CoV-2-infected patients, and some comorbidities are important risk factors for it. The direct activity of the virus on the kidneys has been mentioned in the pathogenesis of AKI in SARS-CoV-2 patients. Further studies are ongoing in order to identify the mechanisms underlying the kidney injury in this population. The role of AKI on survival in SARS-CoV-2-infected patients is another area of active investigation.

Determination of Kinetic and Thermodynamic Parameters of Biomass Gasification with TG-FTIR and Regression Model Fitting

In this study, the decomposition of five different raw materials (maize, wheat and piney biomass, industrial wood chips and sunflower husk) were investigated using the TG-FTIR method to obtain raw data for model-based calculations. The data obtained from the thermogravimetric analysis served as a basis for kinetic analysis with three different isoconversional, model-free methods, which were the KAS, FWO and Friedman methods. Afterwards, the activation energy and the pre-exponential factor were determined, and no significant difference could be identified among the used methods (difference was under 5%), achieving 203–270 kJ/mol of Ea on average. Thereafter, the thermodynamic parameters were studied. Based on the TG-FTIR data, a logistic regression model was fitted to the data, which gives information about the thermal degradation and the obtained components with different heating rates. The FTIR analysis resulted in differential peaks corresponding to the studied components that were detected within the temperature range of 350–380 °C. The primary degradation processes occurred within a broader temperature range of 200–600 °C. Accordingly, in this work, the use of logistic mixture models as an alternative to traditional kinetic models for the description of the TGA process was also investigated, reaching adequate performance in fitting by a validation data coefficient of determination of R2 = 0.9988.

Comparison of estimated blood loss during living kidney transplantation according to the number of double-filtration plasmapheresis

BackgroundPlasmapheresis is an important preoperative desensitization treatment for ABO-incompatible living kidney transplantation. However, in cases with plasma exchange therapy (PET), it is necessary to consider the risks of perioperative bleeding and healthcare economic costs. This study investigated the association between intraoperative blood loss and the frequency of preoperative double-filtration plasmapheresis (DFPP) and explored the correlation between DFPP frequency and coagulation factors. Furthermore, the study examined the incidence of perioperative bleeding complications.MethodsWe enrolled 294 patients (205 men and 89 women) who underwent living kidney transplantation at our institution between January 2020 and March 2023, without PET or with only DFPP performed as PET. A single dose of rituximab (200 mg) was administered to ABO-incompatible living kidney transplant patients within 7 days before transplantation. In these patients, PET was performed until anti-blood group IgG and IgM antibody titers were reduced to 32 times or less.ResultsThe intraoperative blood loss increased in accordance with the DFPP sessions. The amount of bleeding significantly increased when DFPP was performed ≥ 2 sessions. Considering this, we initiated serum fibrinogen level measurements from the middle of the study and observed that serum fibrinogen levels decreased in correlation with the number of DFPP sessions. Fibrinogen levels dropped to critical levels (< 100 mg/dL) after three sessions of DFPP. Within the entire cohort, four patients (1.4%) underwent post-transplantation hematoma removal surgery, and among them, three had received DFPP before transplantation.ConclusionsThe number of DFPP procedures was associated with the amount of bleeding and serum fibrinogen levels during living kidney transplantation.

Synthesis of guar gum maleate under dry conditions: Reaction kinetics and characterization

In the present study, a novel environment friendly dry method for preparation of guar gum maleate (GGM) with varying degrees of substitution (DS; 0.02–1.04) was optimized. GGM with a maximum DS of 1.04 was successfully synthesized using guar gum (GG) and maleic anhydride (MA) in proportion of 1: 1 at 80 °C with 4 h of reaction time. The activation energy for the reaction was determined to be 36.91 ± 3.61 kJ mol−1 with pre-exponential factor of 1392 min−1. Esterification of GG was confirmed by FT-IR and 13C NMR. Analysis using size exclusion chromatography (SEC) indicated a decrease in weight average molecular weight (Mw) of the polymer with an increase in polydispersity index (PDI) due to esterification. In comparison with GG, GGM displayed increased hydrophobicity and reduced thermal stability, as analysed by differential scanning calorimetry (DSC). Rheological studies of GGM revealed that initial apparent viscosity decreased with increasing DS. For the first time, the study offered valuable insights on GGM synthesis under dry solvent-less reaction conditions enabling simpler and scalable synthesis process.

Understanding CO2 adsorption in layered double oxides synthesized by slag through kinetic and modelling techniques

As main by-product in iron and steel industry, high value-added utilization of blast furnace slag had received extensive attention. In this paper, a novelty technology was proposed for using blast furnace slag as raw material to obtain excellent CO2 adsorbent-layered double oxides. The characteristics of layered double hydroxides and layered double oxides were investigated in detailed. Most notably, the laminate structure of layered double hydroxides collapsed and the pore structure, particle size distribution and functional groups of the sample had been greatly changed. The layered double oxides were occupied by phases of CaO, Ca12Al14O32Cl2 and MgO. The transformation mechanism of the layered double oxides preparation was obtained. In addition, CO2 concentration and temperature influencing on CO2 adsorption of layered double oxides were studied and established a suitable kinetic model. The optimal kinetic mechanism model of CO2 adsorption by layered double oxides was PSO. The activation energy and pre-exponential factors were 56.88 kJ‧mol−1 and 12.26 min−1, respectively. Ultimately, CO2 adsorption capacity comparison and preliminary economic evaluation were conducted to assess the industrial feasibility of this technology. This work achieved the goals between CO2 reduction and high value-added utilization of solid waste in iron and steel industry.

Theoretical investigation on action mechanism and mollifying efficacy of propellant stabilizers.

This project performed quantum chemical computation, through kinetic and thermodynamic analyses to compare relative reactivity, reaction rate, and equilibrium composition from the possible pathways in connection with stabilizer-nitrodioxide reactions to determine the stability of the materials for practical application. Corresponding achievements have promoted the use of N-methyl-p-nitroaniline (MNA) and dinitrophenyl malonamide series (M3, M4, and M5) stabilizers as high priorities for selection. The Gaussian 09 program (G09) (Frisch et al 2009) and density functional theory (DFT) calculations with the B3LYP/6-31G(d,p) function were performed to obtain related geometric and thermodynamic energy data for the molecular systems in this study. The synchronous transit-guided quasi-Newton method (STQN) (Peng and Schlegel Isr J Chem 33:49, 1993) was applied through the QST3 procedure to identify single imaginary frequency-valued transition-state species. The related reaction rate constant (k) and pre-exponential factor (A) were obtained, based on transition state theory (Su 2008), using Eqs. 11 and 12.

A Fast Method of High-Frequency Induction Cladding Copper Alloy on Inner-Wall of Cylinder Based on Simulation and Experimental Study

To quickly repair the inner-surface damage to the hydraulic support cylinder caused by frequent scratches, corrosion, and wear in the process of fully mechanized coal mining, this paper proposes a method of high-frequency induction cladding (HIC) copper alloy on inner-wall of cylinder (IWC) to improve the corrosion, sealing and pressure retention performance of hydraulic cylinders combined with numerical simulation and experimental study. Firstly, a numerical temperature field model for HIC of copper alloy on the IWC is established to investigate various distribution patterns and influencing factors including frequency of induction heating, gap between coil and cladding, power supply rating, cladding thickness and side length of square section of induction coil, etc. Subsequently, an HIC test experiment is conducted to rigorously validate the numerical temperature field model and the experiment employs a meticulously collected dataset of temperature measurements, confirming the model’s accuracy and consistent alignment with anticipated changing trends. In addition, the experiment results were verified through microstructure observation, microhardness testing, friction-wear testing, and electrochemical corrosion parameters, which shows that the factors of induction heating frequency and others have obvious effects on the temperature field distribution of HIC copper alloy on the IWC. Under these working conditions (cladding thickness 1.5 mm, power supply rating 120 kW, heating frequency 120 kHz, gap between the cylindrical workpiece and the induction coil 3 mm, induction coil cross-sectional side length of 10 mm), the thermal impact on the cylinder barrel matrix is minimal, the metallurgical bonding between the cladding layer and the matrix is good, and there are no over burning and porosity defects.

Frequency and Risk Factors for Post-COVID-19 Functional Gastrointestinal Disorders After One Year

Objectives: In light of the global COVID-19 pandemic and the subsequent emergence of functional gastrointestinal disorders (FGIDs) post-recovery, this study aimed to evaluate the frequency and risk factors associated with FGIDs one year after recovering from COVID-19. Methods: This cross-sectional study included a total of 357 patients who had recovered from COVID-19 for a year and were seen at Al-Zahra Hospital in 2021. Participants were chosen through simple random sampling. The ROME questionnaire, alongside patients' clinical histories regarding irritable bowel syndrome (IBS) and its variants, functional dyspepsia (FD), and other GI symptoms, was utilized for data collection. Results: Findings indicated that one year post-COVID-19, the prevalence rates of IBS, GI symptoms, and FD stood at 15.4%, 44.9%, and 9.5%, respectively. It was observed that women had a higher propensity than men to develop these FGIDs (P-value = 0.044). Anxiety was linked to a 1.910-fold increase in IBS risk (P-value = 0.039), a 2.225-fold surge in GI symptoms (P-value &lt; 0.001), and a 1.110-fold rise in FD risk (P-value = 0.042). Moreover, depression was associated with a 1.772-fold and 3.753-fold elevated risk of developing IBS (P-value = 0.040) and FD (P-value &lt; 0.001), respectively. Conclusions: The findings suggest that FGIDs such as IBS, FD, and other GI symptoms are significant long-term sequelae of COVID-19 infection. Anxiety and depression appear to be key risk factors for these conditions, with a more pronounced impact observed in women than in men.

Exploring bioenergy prospects from malt bagasse: Insights through pyrolysis with multi-component kinetic analysis and thermodynamic parameter estimation

Malt bagasse is a by-product of little commercial value in the brewing industry. Under this scenario, the current study represents the first investigation aiming to determine the kinetic triplet and thermodynamic parameters for malt bagasse pyrolysis using a multi-component kinetic approach to elucidate its bioenergy prospects. The pyrolysis progress profiles of malt bagasse were obtained through slow pyrolysis experiments on a thermogravimetric scale in an inert atmosphere, employing four distinct heating rates (10, 15, 25, and 40 °C min−1). This investigation also used the Frazer-Suzuki deconvolution function to elucidate the relative contributions of hemicellulose, cellulose, and lignin to malt bagasse pyrolysis. Activation energies for devolatilization reactions were determined by the isoconversional methods of Friedman, Flynn-Wall-Ozawa, Kissinger-Akahira-Sunose, and Starink, and revealed the lowest and highest mean values for pseudo-hemicelluloses (158.3−215.3 kJ mol−1) and pseudo-lignin (279.5−294.8 kJ mol−1), respectively. Frequency factors in malt bagasse pyrolysis ranging from 8.9 × 1016 and 2.2 × 1023 min−1 offer evidence of a simplified reaction chemistry pathway in the conversion towards bioenergy production. The integral master plot indicates the involvement of order-based and geometrical contraction-based mechanisms in malt bagasse pyrolysis. After defining multiple kinetic triplets, a differential equation encompassing contributions from all pseudo-components was formulated, and the simulated results aligned closely with experimental data, accurately describing pyrolysis progress profiles with at least 92.8% precision. The thermodynamic analysis reveals positive ΔH and ΔG values, indicating the non-spontaneous nature of malt bagasse pyrolysis. Higher disorder in the resultant products is attributed to volatile release and molecular rearrangement and is signified by positive ΔS values compared to the initial reactants. This study provided valuable insights into the valorization of malt bagasse, offering crucial information for optimizing pyrolysis reactors, scaling, and designing malt bagasse conversion into valuable biofuels, constituting an effort towards bio-circular economy principles based on the zero-waste concept.

Multistep kinetic analysis of additive-enhanced plastic degradation

In the realm of non-isothermal degradation kinetics, the utilization of multi-heating rate data has unveiled a fascinating distributed apparent activation energy (Eα) profile when employing isoconversional methods. The advanced isoconversional method (AIC) emerges as a reliable tool, offering Eα values that evolve as chemical reactions progresses. This phenomenon finds its roots in the complex solid-state degradation of plastics, where long-chain hydrocarbons undergo intricate transformations into smaller components through a web of parallel and sequential reactions under the influence of heat. To comprehensively characterize this multifaceted kinetic process, variable pre-exponential factor (A) values were calculated, considering all available heating rate data, in conjunction with the isoconversional principle. These factors complement the changing Eα values, providing crucial insights into the evolving material transformations throughout the reaction. Remarkably, our investigation revealed that in the initial degradation stage, centered around the breakdown of Brominated Flame Retardant (BFR), the reaction follows a contracting spherical model (R3). Transitioning to the subsequent stage, the polymer material undergoes degradation following the diffusion model D4. The incorporation of the isoconversional principle and Criados' masterplot technique effectively facilitates the precise determination of all three kinetic parameters. The process layout we present holds considerable promise for advancing the understanding and control of complex kinetic phenomena.

The Oxidation Performance of a Carbon Soot Catalyst Based on the Pt-Pd Synergy Effect

Pt-Pd-based noble metal catalysts are widely used in engine exhaust aftertreatment because of their better carbon soot oxidation performance. At present, the synergistic effect of Pt and Pd in CDPFs, which is the most widely used and common doping method, in catalyzing the combustion of carbon smoke has not been reported, and it is not possible to give an optimal doping ratio of Pt and Pd. This paper investigates the carbon soot oxidation performance of different Pt/Pd ratios (Pt/Pd = 1:0, 10:1, 5:1, 1:1) based on physicochemical characterization and particle combustion kinetics calculations, aiming to reveal the Pt-Pd synergistic effect and its carbon soot oxidation law. The results show that Pt-based catalysts doped with Pd can improve the catalyst dispersion, significantly increase the specific surface area, and reduce the activation energy and reaction temperature of carbon soot reactions, but excessive doping of Pd leads to the enhancement of the catalyst agglomeration effect, a decrease in the specific surface area, and an increase in the activation energy and reaction temperature of the carbon soot reaction. The specific surface area and pore capacity of the catalyst are the largest, and the activation energy of particle oxidation and the pre-exponential factor are the smallest (203.44 kJ∙mol−1 and 6.31 × 107, respectively), which are 19.29 kJ∙mol−1 and 4.95 × 108 lower than those of pure carbon soot; meanwhile, the starting and final combustion temperatures of carbon soot (T10 and T90) are the lowest at 585.8 °C and 679.4 °C, respectively, which are 22.1 °C and 20.9 °C lower than those of pure carbon soot.

Catalytic pyrolysis of pine needles using metal functionalized spent adsorbent derived catalysts: Kinetics, thermodynamics and prediction modelling using artificial neural network (ANN) approach

The current study was indented towards the evaluation of synergism of spent aluminum hydroxide nanoparticle (AHNP) adsorbent derived catalysts in the degradation of pine (Pinus roxburghii) needles through kinetics and thermodynamics analysis. Distinct kinetic (such as activation energy and pre-exponential factors) and thermodynamic (such as entropy, enthalpy, and Gibbs free energy) parameters were estimated through isoconversional (OFA and KAS) models. The study also aimed to envisage the reaction mechanism for all the distinct processes via Criado z master plots. Results illustrated the significant impact of all the different AHNP-derived catalysts in easing up the biomass degradation process. The KAS method evaluated the average activation energy for non-catalytic degradation as 130.01 kJ/mol, while the values changed to 120.95, 121.69, 125.99, 148.47 and 127.37 kJ/mol for Ni/AO, Fe/AO, Cu/AO, Zn/AO and Mo/AO catalyzed degradation, respectively. Amongst all, nickel (Ni/AO) and iron-doped (Fe/AO) catalysts brought the highest reduction in activation energy owing to the provision of strong acidic sites, high specific surface area, and better metal dispersion; subsequently leading to the increased rate of molecular scission and cracking reactions. Values of pre-exponential factor and thermodynamic parameter also displayed the positive impact of catalysts in terms of lowering down the molecular collisions, enthalpy, and disorderness of the system. Furthermore, artificial neural network (ANN) was also employed for the prediction of the biomass degradation where high regression (∼0.99) as well as low mean squared error (<10−5) illustrated the accurate prediction of complex biomass degradation by the ANN technique. Thus, the waste AHNP-derived catalysts have significant potential to be employed for the catalytic pyrolysis of pine needles together with aiding the cost-competitiveness, environmental sustainability, and renewability of the process.

Power Consumption Prediction in Real-Time Multitasking Systems

The paper presents a practical methodology for the prediction of power consumption of a multitask real-time system. The authors briefly recall the structure of the original multitasking time-predictable system. The system has a regular and scalable architecture. It consists of many cores based on pipeline processing with threads’ interleaving mechanism. In previous works, the authors have presented a number of issues related to the methodology of designing a time-predictable system and the scheduling of hardware threads with different design goals and constraints. The current article presents an accurate method for measuring the dynamic power dissipated in a system for various scenarios and the system configuration. The proposed approach is based on continuous monitoring of the power consumed by the FPGA, transmitting the measurements to the computer from the measuring device, and online analysis of the obtained results. The authors based their power estimation method on the original task frequency factor (TF). A theoretical analysis was made, and a series of practical experiments were carried out. The results obtained enable accurate estimation of the power requirements for the tasks performed in the real-time system. The presented technique can be useful during the design stage of multitasking real-time systems.

Factors of frequency and productivity of diminution in early German dialect surveys

This paper examines the productivity of diminution – mainly on the noun – in two large-scale surveys of German dialects of the 19th and early 20th centuries. The starting point is the basic question whether German dialects use differently dimintutive suffixes and which dialect uses diminutives more frequently than others. In addition to morphological and semantic aspects, this question is linked to numerous sociolinguistic, methodological, and phonotactic factors. This leads for example to the general problem, to what extent dialect stereotypes influence classical dialect surveys. The approach is strictly empirical: The data discussed first are translations of the „Parable of the Prodigal Son“ (Luke 15:11–32) into German dialects from the early 19th century are examined (Radlof 1817; Stalder 1819). Subsequently an abbreviated sample of dialect translations of the 40 Wenker sentences from the late 19th and early 20th century is analyzed. Based on these datasets, different influencing factors are discussed that guide the use (and non-use) of diminutives.

Frequency and risk factors for inadequate preparation on boston bowel scale during colonoscopic examination.

Objective: To determine the frequency and risk factors for inadequate bowel preparation using Boston Bowel Preparation Scale. Study Design: Cross-sectional study. Setting: Gastroenterology Department, Liaquat National Hospital, Karachi, Pakistan. Period: September 2022 to June 2023. Methods: The study comprised of patients between 18 to 70 years undergoing colonoscopy. Boston bowel preparation score (BBPS) was used to evaluate the quality of bowel preparation before washing or suctioning. Total score was calculated taking sum of scores in all three segments. Adequate preparation was defined as all 3 BBPS segment scores ≥ 2. Results: In a total of 136 patients, the mean age was 55.8±14.1 years. The mean BBPS score was 5.7±3.5. Based on the criteria of overall adequate rate, inadequate preparation was seen among 44 (32.4%) patients. Lower risk of inadequate preparation was significantly associated with outpatient patients, patients consuming more water and patients with liquid stool consistency whereas odds were significantly higher among patients with age 50 years and above, males, diabetic patients, patients receiving movcal sachet and dulcolex for preparation, patients with lower number of stools (2-4 stools per day) and, patients receiving insulin. Conclusion: The risk of inadequate preparation was higher among older age patients, male gender, diabetic patients, and patients with less number of stools with semi solid consistency.

Study of the effect of implantation temperature on the migration behaviour of Xe implanted into glassy carbon.

The effect of implantation temperature on the migration behaviour of xenon (Xe) implanted into glassy carbon and the effect of annealing on radiation damage retained by ion implantation were investigated. Glassy carbon substrates were implanted with 320keV Xe+ to a fluence of 2×1016cm-2. The implantation process was performed at room temperature (RT) and 100°C Some of the as-implanted samples were isochronally annealed in vacuum at temperatures ranging from 300°C to 700°C in steps of 100°C for 10h. The as-implanted and annealed samples were characterized using Rutherford backscattering spectrometry (RBS) and Raman spectroscopy. The RT implanted depth profiles indicated that the migration of Xe towards the surface of glassy carbon was accompanied by a loss of Xe ions. The samples implanted at 100°C indicated no diffusion or loss of Xe after annealing at 300°C. However, annealing at temperatures ranging from 400°C to 700°C resulted in a slight shift in the Xe profile tail-end towards the bulk of glassy carbon. The diffusion coefficients (D) in the temperature range of 300°C-700°C for the RT and 100°C implanted samples, activation energies (Ea), and pre-exponential factors (Do), were extracted. The values of D ranged from (9.72±0.48)×10-21 to (1.87±0.09)×10-20m2/s with an activation energy of (6.25±0.31)×10-5eV for RT implanted samples, and the samples implanted at 100°C, D ranged from (3.85±0.19)×10-21 to (6.96±0.34)×10-20m2/s with activation energy of (4.10±0.02)×10-5eV. The Raman analysis revealed that implantation at the RT amorphised the glassy carbon structure while the samples implanted at 100°C showed mild damage compared to RT implantation. Annealing of the RT-implanted sample resulted in some recovery of the damaged region as a function of increasing annealing temperature.

Heterogeneous nucleation and dendritic growth of niobium under containerless electrostatic levitation

With the containerless electrostatic levitation method, the undercooling level and nucleation solidification mechanism of niobium samples of 99.7% and 99.95% in purity were comprehensively studied. The classical nucleation theory was used to measure and calculate the thermophysical and thermodynamic characteristics associated with the nucleation and solidification procedure. The measurement results show that the maximum undercooling of experimental samples is 455.7 K, while the hyper cooling limit of the niobium is derived at 739 K. The most probable nucleation undercooling, pre-exponential factor, nucleation activation energy, solid/liquid interface free energy, and the critical nucleus radius are determined. The dendrite growth velocity has a powerful relationship with undercooling, and the dendritic growth velocity of liquid niobium reaches 42.1 m/s at the undercooling of 454 K. The effect of the anisotropy of surface energy is taken into account, and the forecast results display excellent consistency with the experimental ones.

Frequency and risk factors of retinopathy of prematurity: a 5-year single-center study in a Tertiary Care Hospital

Aim Our study aimed to determine the frequency of retinopathy of prematurity (ROP) in a cohort of premature infants screened for ROP, to confirm the efficacy of our screening program used in the NICU to avoid childhood blindness. In addition, we aimed to study the associated risk factors affecting ocular status including birth weight (BW), gestational age (GA), mechanical ventilation, length of intensive care unit (ICU) stay, and number of ROP follow-up. Methods This was a retrospective cohort study conducted from March 2016 to March 2021. Data were retrieved from the records of preterm infants admitted to the neonatal intensive care unit in King Faisal Specialist Hospital and Research Center in Riyadh, Saudi Arabia. The included data: Comprised perinatal data such as sex, BW, GA, multifetal gestation, and delivery type. Neonatal course: Need for surfactant, oxygen therapy, and mechanical ventilation (MV) duration. Neonatal complications: Chronic lung diseases [(respiratory distress syndrome (RDS) and bronchopulmonary dysplasia (BPD)], sepsis, neonatal jaundice, patent ductus arteriosus (PDA), hydrocephalus, and intraventricular hemorrhage (IVH). ROP examination: stage, zone, plus disease, extent, treatment, and number of the follow-up. Results In all, 337 preterm infants met the screening criteria and were included in the study. The majority (52%, n=177) were male; 148 (43.9%) were products of multifetal gestation, the mean GA was 29.35±2.77, and the median BW was 1195.1±338 gm. Caesarean section was the main mode of delivery in 80.5% of our sample (269 babies). ROP was detected in 181 (53.7%) infants, of which 110 (32.6%) had Stage 1, 57 (17%) Stage 2, and 14 (4.15%) had Stage 3. The majority (89.4%) were involved in zone 2–3, and five patients had the plus disease (1.48%). The number of ROP follow-up ranged between 2 and 25 visits either in the NICU or in the eye clinic following their discharge with a mean of 2.347. Conclusion The incidence of ROP in our sample was high relative to other local studies, which was related to the relatively high number of multifetal gestations with high chance of low birth weight as our center is an expert facility in in vitro fertilization. Male patient had a high incidence of development of different stages of ROP. Preterm babies with complicated neonatal course like NEC, Chronic Lung Disease, and IVH had high incidence of development of ROP.