Mechanical Behavior of Selective Laser Melting (SLM) Parts with Varying Thicknesses in a Saline Environment under Different Exposure Times.

A promising method for additive manufacturing that makes it possible to produce intricate and personalized parts is selective laser melting (SLM). However, the mechanical properties of as-corroded SLM parts are still areas of concern. This research investigates the mechanical behavior of SLM parts that are exposed to a saline environment containing a 3.5% NaCl solution for varying lengths of time. The exposure times chosen for this study were 10 days, 20 days, and 30 days. The results reveal that the tensile strength of the parts is significantly affected by the duration of exposure. Additionally, the study also examined the influence of porosity on the corrosion behavior of the parts. The analysis included studying the mass loss of the parts over time, and a regression analysis was conducted to analyze the relationship between exposure time and mass loss. In addition, the utilization of scanning electron microscopy (SEM) and X-ray photo spectroscopy (XPS) techniques yielded valuable insights into the fundamental mechanisms accountable for the observed corrosion and mechanical behavior. It was found that the presence of corrosion products (i.e., oxide layer) and pitting contributed to the degradation of the SLM parts in the saline environment. This research emphasizes the importance of considering part thickness in the design of SLM components for corrosive environments and provides insights for enhancing their performance and durability.

Physicochemical Properties and Simulation of Magnesium/Zinc Binary-Substituted Hydroxyapatite with Enhanced Biocompatibility and Antibacterial Ability.

Ionic substitution can effectively activate the surface of hydroxyapatite (HA) for bone repair and regeneration processes. Therefore in this study, magnesium (Mg)-, zinc (Zn)-, and Mg/Zn-codoped HA was prepared by a hydrothermal method. The results of experimental and first-principles calculations verify the existence of Mg and Zn ions in the HA structure by altering cell parameters, crystallinity, and particle size. The results also showed that Mg and Zn are actively accommodated at the Ca(1) and Ca(2) positions, which not only inhibit HA formation but also promote calcium-deficient HA, and when the codoping content increased to 10%Mg and 10%Zn, the HA transformed completely to the whitlockite phase. Furthermore, the impact of codoping on biocompatibility was examined by employing MC3T3 cells. The in vitro study revealed that 5%Mg and 5%Zn single and -codoped HA promoted the proliferation of MC3T3 cells and 5%Mg-doped and -codoped HA stimulated MC3T3 cell differentiation, while 5%Zn-doped and -codoped HA revealed worthy antibacterial properties. Overall, the obtained results demonstrate that cosubstituted HA (5%Mg and 5%Zn) is promising, which not only eradicates bacteria (Escherichia coli and Staphylococcus aureus) but also induces bone regeneration. These findings suggest that 5%Mg and 5%Zn binary-substituted HA is a very promising biomaterial for hard tissue scaffolds and bone repair.

Corrosion Behavior and Bio-Functions of the Ultrafine-Grained Ti6Al4V-5Cu Alloy with a Dual-Phase Honeycomb Shell Structure in Simulated Body Fluid.

Titanium alloys are widely used in biomedical applications. However, cases of implant failure due to fatigue fracture and bacterial infection are common. In addition, implants are susceptible to metal ions (Al, V) released by long-term exposure to human body fluids, which causes neuropathy, mental disorders, and other diseases. Thus, development of novel materials to achieve long-term safety of implants is currently a research hotspot. Recently, our research group has developed an ultrafine-grained Ti6Al4V-5Cu alloy with a unique "dual-phase honeycomb shell" (DPHS) structure, which possesses high fatigue strength and stability. This study further affirmed its higher corrosion behavior, antibacterial properties, and cytocompatibility compared to the coarse-grained Ti6Al4V and Ti6Al4V-5Cu alloys. The ultrafine-grained structure of Ti6Al4V-5Cu having DPHS increased the proportion of phases (Cu-rich phases, ß-phase, and Ti2Cu intermetallic phase) with a lower surface potential. It was observed that the developed microstructure was conducive to a stable configuration of the oxide (passive) layer on the alloy surface. In addition, the low-phase interfacial energies of the ultrafine-grained structure with DPHS even facilitated the improvement of the denseness of the protective passive film and eventually enhanced the corrosion behavior. Besides, the fine-Cu-rich phases and the micro-galvanic couples formed between them and the matrix significantly increased the contact frequency of bacteria, thus increasing the contact sterilization efficiency of the ultrafine-grained Ti6Al4V-5Cu alloy. These results showed that the new ultrafine-grained Ti6Al4V-5Cu alloy has excellent corrosion resistance and biological functions for clinical application.

Multi-Shaded Edible Films Based on Gelatin and Starch for the Packaging Applications.

Starch and gelatin are natural biopolymers that offer a variety of benefits and are available at relatively low costs. In addition to this, they are an appealing substitute for synthetic polymers for the manufacturing of packaging films. Such packaging films are not only biodegradable but are also edible. Moreover, they are environmentally friendly and remain extremely cost-effective. In lieu of this, films made from fish gelatin and cornstarch have been the subject of several experiments. The pristine gelatin films have poor performance against water diffusion but exhibit excellent flexibility. The goal of this study was to assess the performance of pristine gelatin films along with the addition of food plasticizers. For this purpose, solutions of gelatin/cornstarch were prepared and specified quantities of food colors/plasticizers were added to develop different shades. The films were produced by using a blade coating method and were characterized by means of their shaded colors, water vapor transmission rate (WVTR), compositional changes via Fourier transform infrared spectroscopy (FTIR), hardness, bendability, transparency, wettability, surface roughness, and thermal stability. It was observed that the addition of several food colors enhanced the moisture blocking effect, as a 10% reduction in WVTR was observed in the shaded films as compared to pristine films. The yellow-shaded films exhibited the lowest WVTR, i.e., around 73 g/m2·day when tested at 23 °C/65%RH. It was also observed that the films' WVTR, moisture content, and thickness were altered when different colors were added into them, although the chemical structure remained unchanged. The mechanical properties of the shaded films were improved by a factor of two after the addition of colored plasticizers. Optical examination and AFM demonstrated that the generated films had no fractures and were homogeneous, clear, and shiny. Finally, a biscuit was packaged in the developed films and was monitored via shore hardness. It was observed that the edible packed sample's hardness remained constant even after 5 days. This clearly suggested that the developed films have the potential to be used for packaging in various industries.

Role of inflammatory and hematological markers in predicting the complicated and perforated acute appendicitis in pediatric population: A cohort study.

Introduction: It is important to promptly assess the severity of appendicitis since late diagnosis can proceed towards perforation, peritonitis and sepsis. The main objective of this study is to decipher the ability of CRP, TLC and neutrophils in acute appendicitis to predict complications and perforation in pediatric age group. Methods: This cohort study was conducted in the Pediatric Surgery Department of Liaquat National Hospital, Karachi. It included all the patients diagnosed and operated on for acute appendicitis within the pediatric age group. Results: The median (IQR) age of study population was 9 (7-11) years, the majority of which fell into 6-12 years of age group with 70% males. Histopathology came out positive in 127 individuals. Out of those 127 patients, 45.9% (n = 62) had simple appendicitis and 48.1% (n = 65) had complicated appendicitis (n = 65), while 37 (27.4%) had shown perforation. The majority of individuals had suppurative appendicitis on histopathology (35.6%). On receiver operating characteristic (ROC) analysis, CRP has the highest specificity for complicated appendicitis and the highest positive likelihood ratio for both complicated and perforated appendicitis. Conclusion: CRP was observed in our study to be an independent marker of severity in acute appendicitis.

COVID-19 infection among pregnant and non-pregnant women: Comparison of biochemical markers and outcomes during COVID-19 pandemic, A retrospective cohort study.

Background: & Objectives: We conducted this single-centered retrospective study including female patients infected with COVID-19 with aim to compare laboratory findings and the outcomes between pregnant and non-pregnant women infected with COVID-19. Previous data rendered pregnant women as vulnerable population for COVID-19. Methods: We included 131 patients in our analysis out of which 60 were pregnant females and rest 71 were non-pregnant females. Results: Factors like fatigue, total leukocyte count (TLC) and neutrophils were higher in pregnant patients, while mean age, fever, hemoglobin, ferritin, D-dimer and use of mechanical ventilation was lower in pregnant patients as compared to non-pregnant females. Conclusion: Our study concluded that COVID-19 do not show significant high risk of disease severity when compared with non-pregnant females of similar age group.

Role of 25-hydroxyvitamin D in irritable bowel syndrome patients.

We conducted this study on patients diagnosed with irritable bowel syndrome without identifiable stressors and replaced them with vitamin D supplements for 3 months. Almost 97 cases have repeated the vitamin D status that appeared to be sufficient, while 14 patients were missing data for follow-up. The advised option was intramuscular injection replacement but 34 out of 97 were taken oral route for replacement of Vitamin D and incidental finding is noted that serum vitamin D levels rise less in the oral group than in the intramuscular group. Mean age of our subjects was 35.97 ± 9.89 years, comprising 54% males (n = 60) and 46% females (n = 51). In the outcomes of our study, 56.7% of individuals showed complete relief from IBS symptoms after vitamin D replacement, while 36.1% reported considerable improvement. Another 6.2% had exhibited moderate relief with about 14 individuals lost to follow-up.

Associated Factors With Uremic Pruritus in Chronic Hemodialysis Patients: A Single-Center Observational Study.

Background and objectives Uremic pruritus is a recurrent and delicate manifestation in patients suffering from end-stage renal disease. It is a consequence of multiple factors, primarily comprising of metabolic factors and complement activation along with interleukins. The objective of our study was to find out the associated factors of uremic pruritus in chronic hemodialysis patients. The secondary aim was to obtain cut-off values of all the markers predicting pruritus. Materials and methods A cross-sectional observational study was conducted in the nephrology department of a tertiary care hospital including 135 patients. The current occurrence of pruritus was diagnosed on the basis of a validated and reliable scale of pruritus among chronic kidney disease (CKD) patients in the local language. Multivariate logistic regression and receiver operating characteristic analysis were conducted to decipher the required objectives. Results Study participants had a mean age of 56.29 ± 10.51 years with 56.3% males and 43.7% females. Hypertension was frequent comorbidity (75.6%) followed by diabetes (51.9%). Mean body mass index (BMI), duration of CKD diagnosis, and hemodialysis onset were 26.55 ± 5.37 kg/m2, 6.58 ± 3.65 years, and 3.32 ± 2.09 years respectively. Pruritus was reported in 37.0% of the study participants. On multivariate logistic regression, presence of skin allergy (aOR: 8.100 [2.926-22.420], p<0.001), phosphate >4.5 mg/dL (aOR: 3.889 [1.118-15.532], p=0.033), female gender (aOR: 3.592 [1.337-9.655], p=0.011), albumin <3.5 g/dL (aOR: 2.987 [1.156-7.716], p=0.024) and potassium >5.1 mEq/L (aOR: 2.934 [1.030-8.355], p=0.044) were found significantly associated with pruritus. Conclusion Many factors were linked to pruritus in hemodialysis patients in the current study. The current study also significantly correlated certain factors with pruritus independently.

Mechanical, Biological, and Antibacterial Characteristics of Plasma-Sprayed (Sr,Zn) Substituted Hydroxyapatite Coating.

Implant-related infections are a major concern in total joint prostheses, occurring up to 3% in operations. In this work, 5% Zn2+ was added in HA to offset bacterial activity and 5% Sr2+ was also incorporated as a binary dopant to reduce the cytotoxic effect of Zn2+. The nanosized HA powder was synthesized by the hydrothermal method and then heat-treated at 600 °C for 4 h. The heat-treated powder was plasma-sprayed on a titanium alloy Ti-6Al-4V substrate. The addition of the dopant did not significantly influence the physical and mechanical properties of the coating. However, the cytocompatibility, antimicrobial, and contact-angle properties statistically enhanced. Moreover, the (Sr,Zn)-HA coating was post-heat treated at 500 and 600 °C for 3 h. X-ray diffraction confirmed that after heat treatment phase purity and crystallinity increased and residual stress decreased. Mechanical stability was evaluated by adhesive bond strength, and the results showed that after heat-treatment bonding strength increased from 26.81 ± 2.93 to 29.84 ± 3.62 and 34.66 ± 2.57 MPa, at 500 and 600 °C, respectively. Similar to the mechanical property, antibacterial activities and biological functions are also significantly improved. More interestingly, it was also observed that the Zn2+ ions released from the coating depend on Ca2+, P, and Sr2+ ions while Ca2+, P, and Sr2+ ions relied on heat treatment temperatures. However, (Sr,Zn)-HA coating at 600 °C demonstrates cytotoxic effects on MC3T3-E1 cells, characterized by poor cellular morphology on the coating surface and ultimately, cell death. The doping of Sr2+ with Zn2+, therefore, can offset the cytotoxic effects and enhanced biological performance. All of the outcomes of this study signify that (Sr,Zn)-HA coating heat-treated at 500 °C showed not only excellent mechanical and biological performance but also enhanced the antibacterial properties.

Causes and consequences of the deficiencies of the lower limbs in the Republic of Guinea.

PURPOSE: According to the last general census of 1996, the deficiency of lower limbs is the main cause of handicap in the Republic of Guinea. The objective of this study that took place in 2008 in Conakry is to analyze the main causes of this phenomenon, as well as to understand the reasons of their increase within the Guinean capital. METHOD: Our survey covered 244 Guineans out of which 170 men and 74 women were living in Conakry, aged between 10 and 68 years old (±12,6). RESULTS: The main causes of the deficiencies are the poliomyelitis after-effects (40%), as well as other risk factors such as the road accidents and the failure of the health system. Whatever the nature of the deficiencies, their compensation is mainly based on the technical supports such as tricycles and wheelchairs. However, they are distributed in a random way and without any medical follow-up. CONCLUSION: The orthopedic care in the Republic of Guinea is insufficient and inadequate. Hence, certain individuals who need it the most do not receive it. This type of care is not always helpful and sometimes harmful to the health of the disabled persons.