Effect of surface treatment of recycled concrete aggregate by cement -silica fume slurry on compressive strength of concrete

Recycled concrete aggregate (RCA) used as an alternative to natural aggregate (NA) contains weak adhered mortar. The adhered mortar adversely affects the properties of RCA, and compressive strength of concrete with RCA. Therefore, a treatment method by coating surface of RCA with cement-silica fume slurry (CSS) at concentrations of 20, 40, and 60% was done to evaluate its effects on crushing value and water absorption of RCA, and compressive strength of concrete with treated RCA. The replacements of natural coarse aggregate by RCA for concrete production were 0, 25, and 50% by volume. Compressive strength of the concrete having a constant water-to-cement ratio of 0.35 was tested at ages of 3, 7, 28, and 56 days. Results showed that crushing value and water absorption of the treated RCA were more improved when compared with those of the untreated RCA due to new products formed from cement hydration and pozzolanic reactions on its surface detected by using scanning electron microscope. The surface treatment with CSS at concentration of 60% was the most effective method when compared with that with CSS at concentrations of 20 and 40%. The higher the concentration of CSS, the higher the compressive strength of concrete with the treated RCA. The treatment of RCA led to a significant improvement of compressive strength of the concrete at later ages (i.e., at 28 and 56 days) when compared with the concrete using untreated RCA

Effect of surface treatment of recycled concrete aggregate by cement -silica fume slurry on compressive strength of concrete

Recycled concrete aggregate (RCA) used as an alternative to natural aggregate (NA) contains weak adhered mortar. The adhered mortar adversely affects the properties of RCA, and compressive strength of concrete with RCA. Therefore, a treatment method by coating surface of RCA with cement-silica fume slurry (CSS) at concentrations of 20, 40, and 60% was done to evaluate its effects on crushing value and water absorption of RCA, and compressive strength of concrete with treated RCA. The replacements of natural coarse aggregate by RCA for concrete production were 0, 25, and 50% by volume. Compressive strength of the concrete having a constant water-to-cement ratio of 0.35 was tested at ages of 3, 7, 28, and 56 days. Results showed that crushing value and water absorption of the treated RCA were more improved when compared with those of the untreated RCA due to new products formed from cement hydration and pozzolanic reactions on its surface detected by using scanning electron microscope. The surface treatment with CSS at concentration of 60% was the most effective method when compared with that with CSS at concentrations of 20 and 40%. The higher the concentration of CSS, the higher the compressive strength of concrete with the treated RCA. The treatment of RCA led to a significant improvement of compressive strength of the concrete at later ages (i.e., at 28 and 56 days) when compared with the concrete using untreated RCA

Fostering innovative behavior in the aviation industry: The role of perceived supervisor support and work group diversity

The research primarily seeks to understand how supervisor support can directly and indirectly enhance the service innovative behavior (SIB) of flight attendants via work engagement. Moreover, although there has been some research on the effect of group diversity on organizational performance, the results have not been consistent. Thus, this study addresses this gap by investigating how work group diversity can make variance in the relationship between work engagement and innovative behavior of flight attendants. The sample size of 242 flight attendants working at the central airport in Ho Chi Minh City, Vietnam, has been taken for the study. To test hypotheses, structural equation modeling and bootstrapping were employed. This study provided an evidence for the positive nexus between perceived supervisor support and SIB. Additionally, the results shed light on a mediation mechanism of work engagement for the association between flight attendants' perception of their supervisor and innovative behavior. Furthermore, tenure diversity and job position diversity in a work group were proved to play a moderating role in the relationship between work engagement and service innovative behavior. Specifically, flight attendants are more willing to exhibit innovative behaviors when working in a homogeneous group in terms of tenure and job position rather than in a heterogeneous group. The empirical results contributed to the diversity management literature and broadened the understanding of how to activate the service innovative behavior of employees. From a managerial perspective, managers should pay attention to the characteristics of employees when organizing teamwork. © Long Nguyen Le Hoang, Huong Nguyen Thi Thu, Viet-Anh Ho, 202

Determination of the Administration Routes, Doses and Appropriate Age to Vaccinate With Ornitin Triple Vaccine For Cross-breed Colored Broilers in Vietnam

The study was to determine the appropriate dose and administration route of Ornitin Triple vaccine in cross-breed coloured broilers in Vietnam by evaluating the antibody titer against Ornithobacterium rhinotracheale (ORT) and local reactions at injection sites on chickens after vaccination. The study was divided into 2 trials. Both trials were designed with 3 vaccine dose groups: 0.0ml (control group), 0.25ml and 0.5ml and 2 different administration routes: subcutaneous at neck (SC) and intramuscular at breast (IM) injection. The result showed that, no statistically significant difference was found between antibody titer of two administration routes as well as 2 vaccine doses until 13-week-old. Local reactions at the injection sites of IM route was less severe than SC at neck and in higher dose would produce a more severe swelling reaction. Daily weight gain was found to have a slight decrease in the vaccinated groups within 2 weeks after vaccination, however, no statistically significant difference was found in later stage (P > 0.05). In conclusion, Ornitin Triple can be used to vaccinate by IM with the dose of 0.25ml for coloured broilers at early age (3-week-old), or 0.5ml for older birds and should be careful for some reactions at the injection sites

Acidifiers as Alternatives for Antibiotics Reduction and Gut Health Improvement for Poultry and Swine

Using antibiotics of low doses as feed additives could support to improve poultry and swine performances. However, these applications have caused resistance of bacteria and antibiotic residues in foods of animal origins. Therefore, efforts were focused on solutions to replace antibiotics as growth promoters (AGPs). There are many alternatives for AGPs, in which organic acids are one of the important alternatives. The aim of this chapter is to review publications on these acids and their other forms namely as acidifiers using as feed additives including their names and forms, mode of actions, spectrum against bacteria, combinations among them, and latest updates on their effects on swine and poultry production. The scientific findings show that acidifiers can inhibit pathogenic bacteria growth, improve nutrient digestibility, enhance immunity and overall gut health, consequently increase performances of poultry and swine. Several acids and their salts in both liquid and solid forms have been studied and applied as poultry and swine feed additives; however, the efficacy levels and the mode of actions are dependent on the single acidifiers, their salts, and combinations among them. The uses of acidifiers in their salts and derivative forms and mixtures of different acidifiers seem to be more favorable

Ownership Concentration and Accounting Conservatism: The Moderating Role of Board Independence

The purpose of this study is to examine the moderating effect of board independence on the relationship between ownership concentration and accounting conservatism. Using fixed-effect regressions for a sample of 165 Vietnamese listed companies from 2007 to 2017, the results revealed that the proportion of outstanding shares owned by the largest shareholder is negatively associated with accounting conservatism and board independence plays a moderating role in this relationship. Our results are robust after applying alternative measures of the largest ownership and correcting for potential endogeneity using fixed-effects regression with instrumental variables. Overall, our evidence shows that firms with concentrated ownership should keep a high non-executive ratio to maintain accounting conservatism. In other words, increasing the number of non-executive directors on boards in firms with a substantial proportion of shares held by the largest shareholder is likely to strengthen the information environment, giving financial reporting more credibility.JEL Classification: G30; G32. Doi: 10.28991/ESJ-2023-07-01-07 Full Text: PD

Prevalence and impacts of self-medication in a disadvantaged setting: the importance of multi-dimensional health interventions

BackgroundSelf-medication is recognized as an effective form of treatment and is increasingly encouraged to treat minor illnesses. However, misuse of self-medication leaves devastating impacts on human health and causes antimicrobial resistance. Using medication without a prescription among farmers could cause more severe effects on their health than non-farm workers since they suffer from several occupational hazards such as excessive exposure to pesticides.MethodsA cross-sectional study was conducted in 197 residents living in Moc Chau from August to September. A structured questionnaire and face-to-face were used to collecting data. The multivariate logistic model was applied to indicate associated factors with the self-medication.ResultsThe prevalence of self-medication among farmers was 67%. Pain relievers (66.7%) and antibiotics (32.5%) were the types of medicines that were the most commonly purchased and used without a medical prescription. Ethnics and health status also significantly affected the self-medication practice as well as the purchase and use of antibiotics. The distance to travel to a medical center and the dangerous or difficult travel, participants with arthritis or inpatient treatment had significantly associated with buying and using the medicine and antibiotics without the medical prescription of farmers.ConclusionOur research highlights a considerably high prevalence of self-medication among farmers residing in the mountainous area of Vietnam. Individual factors such as ethnics, health status, distance to health centers, and dangerous or difficult travel were found to be related to the SM practice as well as the purchase and use of antibiotics. From that, the current study suggests interventions. For instance, official guidelines are needed to raise awareness and minimize the disadvantages of self-medication; and digital health technologies should be applied to reduce the gap in healthcare service between mountainous and other areas of Vietnam

PRELIMINARY STUDY ON CHEMICAL MECHANISM OF DECREASE OF TETRODOTOXIN CONTENT IN OVARIES OF A PUFFER FISH Lagocephalus inermis (Temminck and Schlegel, 1850) FERMENTED WITH RICE BRAN

Tetrodotoxins in salted and fermented ovaries with rice bran of a puffer fish Lagocephalus inermis (Temminck Schlegel, 1850) during five months were determined by high-performance liquid chromatography with fluorometric detector (HPLC- FLD). The analysed results showed that the original ovaries contained only tetrodotoxin with content of 7.59 µg/g fresh weight. 4,9-Anhydrotetrodotoxin - an isomer which is less toxic than tetrodotoxin has been found in all ovary samples since the second month. Tetrodotoxin in the ovaries disappeared in the 4th month of the experiment. In addition, 4,9-anhydrotetrodotoxin level in ovaries increased during fermentation. The present study contributes to clarifying the chemical mechanism of decreasing tetrodotoxin content in fermented ovary of puffer fish.Tetrodotoxins in salted and fermented ovaries with rice bran of a puffer fish Lagocephalus inermis (Temminck and Schlegel, 1850) during five months were determined by high-performance liquid chromatography with fluorometric detector (HPLC- FLD). The analysed results showed that the original ovaries contained only Tetrodotoxin with content of 7.59 µg/g fresh weight. 4,9-Anhydrotetrodotoxin- an isomer which is less toxic than Tetrodotoxin has been found in all ovary samples since the second month. Tetrodotoxin in the ovaries disappeared in the 4th month of the experiment. In addition, 4,9-Anhydrotetrodotoxin level in ovaries increased during fermentation. The present study contributes to clarify the chemical mechanism of decreasing Tetrodotoxin content in fermented ovary of puffer fish

MỘT SỐ ĐẶC TÍNH CỦA CANXI HYDROXYAPATIT CHIẾT XUẤT TỪ XƯƠNG CÁ NGỪ VẰN Katsuwonus pelamis

This paper is concerned with certain properties of calcium hydroxyapatite from skipjack tuna bone (Katsuwonus pelamis) which are by-products of fish export industry. Hydroxyapatite Ca10(PO4)6(OH)2 and β-tricalcium phosphate Ca3(PO4)2, the high-value compounds, have been successfully extracted from skipjack tuna bones. The bones were heated at different temperatures of 600oC, 900oC, 1200oC. While at 600oC hydroxyapatites were obtained with Ca/P ratio of 1.658, comparable to the value of 1.67 found in human bone; the hydroxyapatite crystals of average size of 0.25 µm were formed with the same size distribution. In case of heated bone samples at 900°C and 1200°C, the calcium formed were biphasic calcium phosphate composed of hydroxyapatite and β-tricalcium phosphate; the Ca/P ratio was between 1.660–1.665; the calcium crystals of more than 1 µm were highly porous and connected to each other in priority orientation of tube direction.Bài báo này trình bày kết quả nghiên cứu về một số đặc tính của canxi hydroxyapatit chiết xuất từ xương cá ngừ Katsuwonus pelamis, một sản phẩm phụ từ ngành xuất khẩu thịt cá ngừ. Các hợp chất có giá trị là hydroxyapatit Ca10(PO4)6(OH)2 và β-tricanxi phosphat β-TCP Ca3(PO4)2 đã được chiết xuất thành công từ xương cá ngừ vằn. Xương cá ngừ được nung ở các nhiệt độ khác nhau 600, 900 và 1.200oC. Dạng canxi thu được khi nung mẫu ở 600oC là hydroxyapatit với tỉ lệ Ca/P 1,658 gần với tỉ lệ Ca/P 1,67 trong xương người; các tinh thể hydroxyapatit có kích thước trung bình 0,25 µm và sự phân bố kích thước tương đối đồng đều. Đối với mẫu xương được xử lý ở 900 và 1.200oC, canxi thu được là hỗn hợp hai pha hydroxyapatit Ca10(PO4)6(OH)2 và β-tricanxi phosphat Ca3(PO4)2; tỉ lệ Ca/P từ 1,660–1,665, các tinh thể canxi có độ xốp cao và liên kết với nhau theo hướng ưu tiên kiểu hình ống với kích thước lớn hơn 1 µm

Viral Metagenomic Analysis of Cerebrospinal Fluid from Patients with Acute Central Nervous System Infections of Unknown Origin, Vietnam.

Central nervous system (CNS) infection is a serious neurologic condition, although the etiology remains unknown in >50% of patients. We used metagenomic next-generation sequencing to detect viruses in 204 cerebrospinal fluid (CSF) samples from patients with acute CNS infection who were enrolled from Vietnam hospitals during 2012-2016. We detected 8 viral species in 107/204 (52.4%) of CSF samples. After virus-specific PCR confirmation, the detection rate was lowered to 30/204 (14.7%). Enteroviruses were the most common viruses detected (n = 23), followed by hepatitis B virus (3), HIV (2), molluscum contagiosum virus (1), and gemycircularvirus (1). Analysis of enterovirus sequences revealed the predominance of echovirus 30 (9). Phylogenetically, the echovirus 30 strains belonged to genogroup V and VIIb. Our results expanded knowledge about the clinical burden of enterovirus in Vietnam and underscore the challenges of identifying a plausible viral pathogen in CSF of patients with CNS infections