Developing Qualitative Plasmid DNA Reference Materials to Detect Mechanisms of Quinolone and Fluoroquinolone Resistance in Foodborne Pathogens

The aim of this study was to develop homogeneous and stable plasmid DNA reference materials for detecting the mechanisms of resistance to quinolones and fluoroquinolones in foodborne pathogens. The DNA fragments of 11 target genes associated with quinolone and fluoroquinolone resistance were artificially synthesized, inserted into plasmid vectors, and transferred into recipient cells. PCR and sequencing of DNA were performed to assess the genetic stability of the target DNA in recombinant Escherichia coli DH5α cells during subculturing for 15 generations. The limit of detection (LOD) of the target DNA was determined using PCR and real-time qualitative PCR (qPCR). The homogeneity and storage stability of plasmid DNA reference materials were evaluated in terms of plasmid DNA quantity, PCR-measured gene expression, and qPCR threshold cycle. All 11 target DNAs were successfully synthesized and inserted into vectors to obtain recombinant plasmids. No nucleotide mutations were identified in the target DNA being stably inherited and detectable in the corresponding plasmids during subculturing of recombinant strains. When the target DNA was assessed using PCR and qPCR, the LOD was ≤1.77 × 105 and 3.26 × 104 copies/μL, respectively. Further, when the reference materials were stored at 37 °C for 13 days, 4 °C for 90 days, and −20 °C for 300 days, each target DNA was detectable by PCR, and no mutations were found. Although the threshold cycle values of qPCR varied with storage time, they were above the LOD, and no significant differences were found in the quantity of each plasmid DNA at different timepoints. Further, the homogeneity and stability of the materials were highly consistent with the requirements of standard reference materials. To summarize, considering that our plasmid DNA reference materials conformed to standard requirements, they can be used to detect the mechanisms of quinolone and fluoroquinolone resistance in foodborne pathogens.

Production, Mechanical Properties and Biomedical Characterization of ZrTi-Based Bulk Metallic Glasses in Comparison with 316L Stainless Steel and Ti6Al4V Alloy

Microstructure, mechanical properties, corrosion resistance, and biocompatibility were studied for rapidly cooled 3 mm rods of Zr40Ti15Cu10Ni10Be25, Zr50Ti5Cu10Ni10Be25, and Zr40Ti15Cu10Ni5Si5Be25 (at.%) alloys, as well as for the reference 316L stainless steel and Ti-based Ti6Al4V alloy. Microstructure investigations confirm that Zr-based bulk metallic samples exhibit a glassy structure with minor fractions of crystalline phases. The nanoindentation tests carried out for all investigated composite materials allowed us to determine the mechanical parameters of individual phases observed in the samples. The instrumental hardness and elastic to total deformation energy ratio for every single phase observed in the manufactured Zr-based materials are higher than for the reference materials (316L stainless steel and Ti6Al4V alloy). A scratch tester used to determine the wear behavior of manufactured samples and reference materials revealed the effect of microstructure on mechanical parameters such as residual depth, friction force, and coefficient of friction. Electrochemical investigations in simulated body fluid performed up to 120 h show better or comparable corrosion resistance of Zr-based bulk metallic glasses in comparison with 316L stainless steel and Ti6Al4V alloy. The fibroblasts viability studies confirm the good biocompatibility of the produced materials. All obtained results show that fabricated biocompatible Zr-based materials are promising candidates for biomedical implants that require enhanced mechanical properties.

Study on the production of Reference Material (RM) for Vitamin B1, B2, B6 in health supplements

Vitamins are essential nutrients commonly found in food products in general and health supplements in particular. In order to accurately evaluate product quality, laboratories need to use reference material in analysis, proficiency assessment, method validation and ensure the validity of the results. The use of reference materials plays an important role in the quality control of test results and is a mandatory requirement for laboratories wishing to demonstrate appropriate competence as required by ISO/IEC 17025:2017. The need to provide reference materials for laboratories is huge. However, at present, there are very few domestic organizations that can produce reference materials, while the cost of buying reference materials from reputable firms in the world is expensive. In this study, we introduced the procedure and production reference materials for the analysis of B-group vitamins (B1, B2, B6). These reference materials were evaluated for homogeneity and stability in 322 days. The certified values are consistent with the concentrations of substances present in normal samples in practice. The measurement uncertainty ranges from 14.5 - 23.3 %. The reference materials can be used for internal quality control for domestic laboratories and is also a premise for further research on standard samples with different matrix and analytical criteria.

PHƯƠNG PHÁP K-ZERO TRONG PHÂN TÍCH KÍCH HOẠT NEUTRON (k0 - NAA)

Phân tích kích hoạt neutron (NAA) là một phương pháp phân tích vật lí hạt nhân không hủy mẫu với độ nhạy và độ chính xác cao có khả năng giải quyết nhiều bài toán thực tế trong nghiên cứu địa chất, khảo cổ, nông – sinh – y, vật liệu, môi trường… Trong NAA, có 3 loại nguồn neutron thường được sử dụng: nguồn đồng vị, máy gia tốc và lò phản ứng. Sử dụng nguồn neutron từ lò phản ứng hạt nhân nghiên cứu có thông lượng neutron cao, vì vậy đây là nguồn neutron cho NAA có nhiều ưu điểm nhất trong 3 loại nguồn kể trên. NAA có các phương pháp chuẩn hoá khác nhau: tuyệt đối, tương đối, chuẩn đơn và k-zero, trong đó phương pháp k-zero của NAA (k0-NAA) được đánh giá là phương pháp ổn định (về mặt sai số hệ thống) có độ nhạy và độ chính xác cao, đặc biệt khi nghiên cứu một số đối tượng như bài toán môi trường, địa chất, khảo cổ… quan tâm đặc biệt đến mối tương quan giữa các nguyên tố cho nhiều mẫu nghiên cứu thì thể hiện sự ưu việt vượt trội của phương pháp. Chính vì vậy mà phương pháp k0-NAA đã được chọn và sử dụng ở nhiều nơi trên thế giới như một phương pháp chuẩn (tham khảo) dùng để phê chuẩn (validation) cho các mẫu chuẩn – tham khảo (standard reference materials) và cũng là phương pháp chính trong nhiều đối tượng nghiên cứu.

Challenges Encountered and Technical Assistance Needed by Parents and Learners Utilizing Modular Distance Learning: Basis for a Proposed Support Program

The shift from face-to face to distance learning brought about by the outbreak of the COVID-19 pandemic is a major adjustment to all school administrators, teachers, students and parents. The study aimed to determine the challenges encountered and needed support of parents and learners in an elementary school of the Schools Division of Meycauayan City as basis for crafting a contextualized support program. It employed a mixed method design using survey-questionnaire and interview guide as data gathering tools to 123 parents and 10 learners respectively. Frequency and percentage were used to describe the demographic profile, frequency counts and ranking were used on the challenges encountered and support/technical assistance needed by parents while thematic analysis was used to describe the experiences of the learners. The study found out that difficulty in independent learning, difficulty in concentrating on studies and parent’s limited knowledge on the content of child’s lessons are the top struggles of parents in the modular distance learning while almost all learner-respondents describe their experiences of distance learning as difficult because of difficulty in learning by themselves, lack of reference materials for more examples, limited guidance from parents and teachers, challenges in load to research and difficulty in understanding English. Moreover, both respondents are unanimous in declaring that provision of additional reference materials will greatly help lessen the struggles they encountered. Therefore, it is recommended that the support program crafted should be implemented and monitored to fully reinforce the continuity of learning amidst the challenges encountered in the first quarter.

Supplemental Material: Biotite as a recorder of an exsolved Li-rich volatile phase in upper-crustal silicic magma reservoirs

Supplemental Figures S1–S8 (additional compositional information relevant to this study), and a supplemental dataset (all new data for this study and reference materials).<br>

Supplemental Material: Biotite as a recorder of an exsolved Li-rich volatile phase in upper-crustal silicic magma reservoirs

Supplemental Figures S1–S8 (additional compositional information relevant to this study), and a supplemental dataset (all new data for this study and reference materials).<br>

The Importance of Reference Materials and Method Validation for Advancing Research on the Health Effects of Dietary Supplements and Other Natural Products

Insufficient assessment of the identity and chemical composition of complex natural products, including botanicals, herbal remedies, and dietary supplements, hinders reproducible research and limits understanding mechanism(s) of action and health outcomes, which in turn impede improvements in clinical practice and advances in public health. This review describes available analytical resources and good methodological practices that support natural product characterization and strengthen the knowledge gained for designing and interpreting safety and efficacy investigations. The practice of validating analytical methods demonstrates that measurements of constituents of interest are reproducible and appropriate for the sample (e.g., plant material, phytochemical extract, and biological specimen). In particular, the utilization of matrix-based reference materials enables researchers to assess the accuracy, precision, and sensitivity of analytical measurements of natural product constituents, including dietary ingredients and their metabolites. Select case studies are presented where the careful application of these resources and practices has enhanced experimental rigor and benefited research on dietary supplement health effects.