Progresses and Challenges of Composite Laminates in Thin-Walled Structures: A Systematic Review.

Most engineering technologies, gadgets, and systems have been developed around the use of sophisticated materials. Composite laminates have found widespread application in various significant and innovative industries, such as aviation, maritime transportation, automobiles, and civil engineering. Recent studies have revealed that composite materials are extensively utilized in automotive, undersea, and structural applications. Extensive efforts have been dedicated to exploring the structural components constructed from composite materials due to their importance in engineering. While composite materials offer certain advantages over their metallic counterparts, they also present analysts and designers with intricate and challenging issues. Hence, this Review aims to highlight noteworthy studies on composite materials and their engineering applications, specifically focusing on structural components. Furthermore, this Review includes a comprehensive summary of the application of composite laminates, accompanied by a critical analysis of the existing literature in this field. By presenting this information, the Review intends to provide a valuable resource and guideline for researchers interested in leveraging composite materials for engineering structures.

A Study on the Effect of Piezoelectric Nonlinearity on the Bending Behaviour of Smart Laminated Composite Beam.

This paper presents a finite element analysis to model and analyze composite laminated beams with distributed piezoelectric actuators attached to the top and bottom surfaces considering nonlinear constitutive equations under a high electric field. The static response is presented for piezoelectric composite laminated beam using higher order electric field nonlinearity to assess the effect of electrostriction and elastostriction coefficient at a high electric field. A finite element approach based on higher-order shear deformation theory is applied for static analysis of composite laminated beams, varying the thickness and orientation of laminates, to verify the nonlinear effect under a high electric field. A good comparison of results is shown with the available results in the literature. The finding of the results highlights the importance of considering elastostriction term along with the electrostriction term in determining the deflection and stresses of the composite laminated beam.

Optimization of Structural Damage Repair with Single and Double-Sided Composite Patches through the Finite Element Analysis and Taguchi Method.

Over the last four decades, numerous studies have been conducted on the use of bonded composite repairs for aircraft structures. These studies have explored the repair of damaged plates through experimental, numerical, and analytical methods and have found that bonded composite repairs are effective in controlling crack damage propagation in thin plates. The use of double-sided composite repairs has been found to improve repair performance within certain limits. This study focuses on these limits and optimizes double-sided composite repairs by varying adhesive bond and composite patch parameters. The optimization process begins with a finite element analysis to determine the stress intensity factor (SIF) for various variables and levels, followed by the application of the Taguchi method to find the optimal combination of parameters for maximizing the normalized SIF. In conclusion, we successfully determined the stress intensity factor (SIF) for various variations and normalized it for optimization. An optimization study was then performed using the Taguchi design and the results were analyzed. Our findings demonstrate the repair performance of bonded composite patches using a cost-effective and energy-efficient approach.

A Review on Reductions in the Stress-Intensity Factor of Cracked Plates Using Bonded Composite Patches.

In aerospace engineering applications, lightweight material structures are considered to perform difficult service conditions and afford energy efficiency. Therefore, composite materials have gained popularity due to their light weights and high performances in structural design. Mechanical loads and environmental conditions primarily create damage to structural materials, thus numerous studies have considered the repair of the damaged structure. Bonded composite repairs are generally chosen, as they provide enhanced stress-transfer mechanisms and joint efficiencies with the increased use of advanced composite materials in primary and secondary aircraft structural components. Thus, it is essential to have reliable and repeatable bonded repair procedures to restore damaged structural components. However, composite bonded repairs, especially with primary structures, present several scientific challenges in the current existing repair technologies. In this review, a study has been done on the bonded composite repair of damaged structures with the stress-intensity factor (SIF) as the parameter for defining the extent of failure by composite repair and unrepaired material structures. In this work, various types of repair methods and the techniques used by researchers are critically reviewed, and future opportunities are explored. The present study was limited to the composite and aluminium materials that are common in aerospace applications.

Establishing biotinidase reference interval: A foundation stone for newborn screening of biotinidase deficiency in Pakistan.

OBJECTIVE: To determine the reference interval of biotinidase activity in healthy neonates. METHODS: The cross-sectional study was conducted at the Department of Chemical Pathology and Endocrinology, Armed Forces Institute of Pathology, Rawalpindi, Pakistan, from May to November 2019, and comprised blood samples collected from healthy neonates aged 2-6 days. The samples were collected on filter paper and analysed on genetic screening processor based on dissociation-enhanced lanthanide flouroimmunoassay. Data was analysed using SPSS 21. RESULTS: Of the 120 dried blood spot specimens, 81(67.5%) were from male babies and 39(32.5%) from female babies. Reference interval for biotinidase activity, based on 2.5th and 97.5th percentiles, was from 3.0 to 11.0 nmol/ml/min. CONCLUSIONS: Screening of newborns for biotinidase deficiency is crucial to prevent irreversible neurological damage.

Association of Serum Hyaluronic Acid and Laminin with Polymerase Chain Reaction Findings in Hepatitis C Patients.

OBJECTIVES: To find the association of serum hyaluronic acid and laminin levels with polymerase chain reaction (PCR) results in hepatitis C sero-positive patients; and the correlation among viral load, serum hyaluronic acid, and serum laminin levels. STUDY DESIGN: Cross-sectional descriptive study. PLACE AND DURATION OF STUDY: Department of Chemical Pathology and Endocrinology, Armed Forces Institute of Pathology (AFIP), Rawalpindi, Pakistan from December 2019 to July 2020. METHODOLOGY: One hundred and eighty diagnosed cases of hepatitis C patients were included in this study. To find association, cross tabulation was done after dividing into two groups according to their median by applying Chi-square test. Correlation of viral load, duration of disease, serum hyaluronic acid and laminin levels were calculated using Spearman's correlation. RESULTS: There were 124 (68.9%) males and 56 (31.1%) females. Median (IQR) age was 36 (32.3 - 45.0) years; while median duration of disease was 12 (8 - 18) months. There was a strong association between PCR positive cases with hyaluronic acid (p <0.001) and serum laminin levels (p <0.001). A strong relationship was found between viral load and serum hyaluronic acid (r =0.889, p <0.001), as well as with serum laminin (r =0.889, p <0.001). CONCLUSION: Current study established a strong significant association between PCR results and disease duration with levels of serum laminin and hyaluronic acid. The levels of serum laminin and serum hyaluronic acid also correlate well with viral load and duration of disease. Key Words: Hepatitis C, Hepatic fibrosis, Hyaluronic acid, Laminin.

Rare bleeding disorders: spectrum of disease and clinical manifestations in the Pakistani population.

BACKGROUND: Rare inherited coagulation factor deficiencies constitute an important group of bleeding disorders. A higher frequency of these disorders is seen in areas of high consanguinity. Our aim was to study the prevalence and spectrum of rare inherited bleeding disorders, characterize the severity of the deficiencies, identify different clinical manifestations, and evaluate different treatments provided. METHODS: This cross-sectional study was conducted in the Department of Haematology, Armed Forces Institute of Pathology Rawalpindi, between January 2014 and December 2018. A detailed history was taken, and an examination was performed. The signs and symptoms were noted, and the patients were diagnosed on the basis of a coagulation profile. The disease severity was assessed using factor assays. RESULTS: Among 2,516 patients with suspected coagulation disorders, 774 (30.8%) had an inherited bleeding disorder. Of the 774 patients, 165 (21.3%) had a rare bleeding disorder; 91 (55.2%) of them were males, and 74 (44.9%) were females, with a male-to-female ratio of 1.2:1. The median patient age was 9 years 3 months. The most common disorder was factor VII deficiency (46 patients, 27.9%). The most common clinical presentation was bruising in 102 (61.8%) and gum bleeding in 91 (55.2%) patients. CONCLUSION: The most common rare bleeding disorder in our population is factor VII deficiency. The prevalence of these bleeding disorders is high in our population due to a high number of consanguineous marriages.

Comparison of Estimated Glomerular Filtration Rate with Both Serum Creatinine and Cystatin C (eGFRcr-cys) versus Single Analyte (eGFRcr or eGFRcys) Using CKD-EPI and MDRD Equations in Tertiary Care Hospital Settings.

OBJECTIVES: To assess and compare the glomerular filtration rate (eGFR) estimated through MDRD and CKD-EPIcr equations in early and late stages of chronic kidney disease on biochemical marker creatinine (eGFRcr), cystatin C (eGFRcys); and combined (eGFRcr-cys), using CKD-EPI equation. STUDY DESIGN: Observational, comparative cross-sectional study. PLACE AND DURATION OF STUDY: Chemical Pathology and Endocrinology Department, Armed Forces Institute of Pathology (AFIP), Rawalpindi in collaboration with Armed Forces Institute of Urology (AFIU), Rawalpindi from October 2019 to March 2020. METHODOLOGY: GFR was assessed on the basis of creatinine clearance taking serum and 24-hour urinary specimens. MDRD and CKD-EPI equations were applied to calculate eGFR by serum creatinine (eGFRcr), cystatin C (eGFRcys), and combined (eGFRcr-cys). Pearson correlation technique was used to compare eGFR calculated by different equations with creatinine clearance in different stages of CKD. Performance of equations was evaluated and compared in different stage of CKD. RESULTS: A total of 181 subjects were enrolled. Median age was 57 years (IQR, 25). Median (IQR) GFR (ml/min/1.73m2) calculated by CrCl, MDRD, CKD-EPIcr, CKD-EPIcys and CKD-EPIcr-cys equations were 45.1 (41.5), 50.6 (23.8), 52.0 (28.0), 43.0 (65.0) and 45 (47), respectively. eGFR calculated by CKD-EPIcr had positive and slightly higher correlation (r=0.880) than MDRD study equation (r=0.867). While comparing the markers, it was observed that CKD-EPIcys had better correlation in early stages of CKD (r=0.889); whereas, CKD-EPIcr performed better in late stages (r=0.896). CKD-EPIcr-cys had the highest correlation (r=0.984) at all stages of CKD. CONCLUSION: eGFR calculated by CKD-EPI equation considered as better diagnostic efficient response than MDRD equation in diagnosis and staging of chronic kidney disease. While applying CKD-EPI equation for measurement of eGFR, eGFRcr-cys performs better than any of eGFRcr or eGFRcys at all stages of CKD. Key Words: Estimated glomerular filtration rate (eGFR), Cystatin C (Cys), Creatinine (Cr), Creatinine clearance (CrCl), CKD-EPI equation, MDRD equation.

Fouling-free ultrafiltration for humic acid removal.

Membrane fouling is a serious concern that significantly affects the membrane filtration process. In this study, an ultrafiltration (UF) membrane was developed with surface auto-regeneration potential by immobilizing a photocatalyst [titanium dioxide nanoparticles (TiO2 NPs)] on a hybrid polyvinylidene fluoride (PVDF) membrane to reduce fouling. The combination of photocatalysis and UF, namely, photocatalytic UF, induced the surface auto-regeneration potential to the membrane. The photocatalytic process was initiated after UV light reached the TiO2 NPs through a quartz window in the membrane containing cell. The membrane, with an optimized distribution of TiO2 NPs (3.04 g m-2), could completely regenerate itself during photocatalytic UF [with 2 mg L-1 humic acid (HA)] without experiencing membrane fouling during 90 min of filtration. The impact of temperature, an important factor for increasing the kinetic rate of the photocatalyst, was also studied. The results showed that an increase in temperature did not affect the photocatalytic process, but increased the permeate flux, which was attributed to the decrease in kinematic viscosity of the water. Finally, four consecutive photocatalytic UF cycles demonstrated the stability of the membrane for a fouling-free UF process.

Evaluation of random plasma glucose for assessment of glycaemic control in type 2 diabetes mellitus.

OBJECTIVE: To evaluate the accuracy of random plasma glucose in outpatients with type 2 diabetes mellitus for assessing glycaemic control. METHODS: This comparative, cross-sectional study was conducted at the chemical pathology department of PNS Shifa Hospital, Karachi, from August 2015 to March 2016, and comprised data of subjects with type 2 diabetes mellitus who reported for evaluation of glycaemic control in non-fasting state. All blood samples were analysed for random plasma glucose and glycated haemoglobin. Random plasma glucose was compared as an index test with glycated haemoglobin considering it as reference standard at a value of less than 7% for good glycaemic control. SPSS 20 was used for data analysis. RESULTS: Of the 222 subjects, 93(42%) had good glycaemic control. Random plasma glucose showed strong positive correlation with glycated haemoglobin (p=0.000).Area under curve for random plasma glucose as determined by plotting receiver operating characteristic curve against glycated haemoglobin value of 7% was 0.89 (95% confidence interval: 0.849-0.930). Random plasma glucose at cut-off value of 150 mg/dl was most efficient for ruling out poor glycaemic control among patients with type 2 diabetes mellitus with 90.7% sensitivity and69.9% specificity and Youden's index of 0.606. CONCLUSIONS: Random plasma glucose may be used to reflect glycaemic control in adults with type 2 diabetes mellitus in areas where glycated haemoglobin is not feasible.

The Extent of Heavy Metal Pollution and Their Potential Health Risk in Topsoils of the Massively Urbanized District of Shanghai.

Urbanization and industrialization increase the concentrations of heavy metals in soils, which affect human health. A total of 127 topsoil samples were collected from the massively urbanized and industrialized district of Shanghai: Baoshan District. The sampling sites were isolated based on the land-use practice: industrial area, roadside area, residential area, and agricultural area. The absolute concentrations of heavy metals (Zn, Cr, Ni, Mn, Cu, Pb, and Cd) were determined using atomic absorption spectrometry and compared with Shanghai and the National soil background values. The geoaccumulation index (Igeo) and Nemerow pollution index were used to determine the existence and severity of the pollution of heavy metals. Enrichment factor (EF) analysis, spatial variability of pollution, and multivariate statistical analyses also were employed to determine the anthropogenic loading of heavy metals, their spatial dependency, and correlation among their sources, respectively. Moreover, potential ecological risk and human health risk [carcinogenic risk (RI) and noncarcinogenic hazard (HI)] were evaluated. The average concentration of all the metals (accounted as 229, 128, 56, 719, 55, 119, and 0.3 mg kg-1 for Zn, Cr, Ni, Mn, Cu, Pb, and Cd, respectively) was many folds higher than the background values. The indices depicted that the pollution exists in all the sites and severity decreases in the following order: industrial soils > roadside soil > residential soils > agricultural soils. However, Zn, Pb, and Cd showed high levels of pollution in all the soils. The EF values suggested that the majority of heavy metals are anthropogenically loaded; spatial variability showed that the pollution is more concentrated in Songnan town; Pearson's correlation, principal component analysis (PCA), and cluster analysis suggested different sources of origin for the majority of the heavy metals. RI of Cr and Pb ranged between 2.8E-04 and 2.7E-07. However, HI was site-specific (only for Cr, Pb, Mn), and most of the sites were in Songnan town. This study could be used as a significant piece of information for management purposes to prevent heavy metal pollution and to protect human health.

Loss of basal forebrain P75(NTR) immunoreactivity in subjects with mild cognitive impairment and Alzheimer's disease.

The long-held belief that degeneration of the cholinergic basal forebrain was central to Alzheimer's disease (AD) pathogenesis and occurred early in the disease process has been questioned recently. In this regard, changes in some cholinergic basal forebrain (CBF) markers (e.g. the high affinity trkA receptor) but not others (e.g., cortical choline acetyltransferase [ChAT] activity, the number of ChAT and vesicular acetylcholine transporter-immunoreactive neurons) suggest specific phenotypic changes, but not frank neuronal degeneration, early in the disease process. The present study examined the expression of the low affinity p75 neurotrophin receptor (p75(NTR)), an excellent marker of CBF neurons, in postmortem tissue derived from clinically well-characterized individuals who have been classified as having no cognitive impairment (NCI), mild cognitive impairment (MCI), and mild AD. Relative to NCI individuals, a significant and similar reduction in the number of nucleus basalis p75(NTR)-immunoreactive neurons was seen in individuals with MCI (38%) and mild AD (43%). The number of p75(NTR)-immunoreactive nucleus basalis neurons was significantly correlated with performance on the Mini-Mental State Exam, a Global Cognitive Test score, as well as some individual tests of working memory and attention. These data, together with previous reports, support the concept that phenotypic changes, but not frank neuronal degeneration, occur early in cognitive decline. Although there was no difference in p75(NTR) CBF cell reduction between MCI and AD, it remains to be determined whether these findings lend support to the hypothesis that MCI is a prodromal stage of AD.