Natural Vibrations and Buckling of a Spatial Lattice Structure Using a Continuous Model Derived from an Energy Approach

A.M. Guzmán,M.B. Rosales,C.P. Filipich 한국강구조학회 2017 International Journal of Steel Structures Vol.17 No.2

Lattice structures composed by parallel members named chords (or legs for vertical configurations) and connected by diagonals are very common among steel constructions in Civil and Mechanical Engineering and in particular, in the telecommunications industry. In the present study, a continuous model of a typical spatial lattice structure is derived. The legs configure a triangular cross-section and the diagonals are arranged in a zig-zag pattern. The differential system is derived from the potential and kinematic energies of the discrete model as the sums of each component contribution. Then, after accepting that the number of diagonals is large enough, the sums are approximated in the limit with classical integrals. Thus, the discrete system is replaced with a continuous formulation. The natural vibration problem of a lattice mast with a zig-zag diagonal pattern is studied using the proposed model. Also, the axial load influence is also accounted for through the second-order effect allowing to solve the buckling problem. Static deflection problems are also addressed. The Hamilton principle application yields the governing differential system in terms of nine unknown displacements. Several examples are solved numerically and the results are compared with the outcomes of a finite element spacial model. It is shown that there is an excellent agreement. The proposed continuous model can represent adequately the spatial lattice with a strong reduction in the degrees of freedom and the time of computation of the solution in comparison with a finite element approach.

Can We Rely on the Rome IV Questionnaire to Diagnose Children With Functional Gastrointestinal Disorders?

( Desiree F Baaleman ),( Carlos A Velasco-benítez ),( Laura M Méndez-guzmán ),( Marc A Benninga ),( Miguel Saps ) 대한소화기기능성질환·운동학회 2021 Journal of Neurogastroenterology and Motility (JNM Vol.27 No.4

Background/Aims To investigate the intra-rater (test-retest) reliability of the diagnosis of functional gastrointestinal disorders (FGIDs) as measured by the Questionnaire on Pediatric Functional Gastrointestinal Disorders, Rome IV version (QPGS-IV) in children. Methods A prospective cohort study was conducted in a public school in Cali, Colombia. Children and adolescents between 11 and 18 years of age were given the self-report Spanish version of the QPGS-IV at day 0 (baseline) and at day 2 (48 hours later). Results The study protocol was completed by 215 children, of which 97 (45%) were excluded from analysis due to the inability to follow the questionnaire’s instructions. The final analysis included data of 118 children (mean age 15.0 ± SD 1.8 years old, 58.5% boys). The most common diagnoses were functional dyspepsia, functional constipation, and irritable bowel syndrome. We found a moderate intra-rater reliability (κ = 0.61-0.65) for diagnosing an FGID in general, a functional abdominal pain disorder, and the diagnosis of functional dyspepsia. We found a weak intra-rater reliability (κ = 0.46-0.54) for diagnosing a functional defecation disorder, functional constipation, irritable bowel syndrome, and the postprandial distress syndrome subtype of functional dyspepsia. Conclusions Our study shows that a large proportion of children cannot adequately complete the QPGS-IV and that the intra-rater reliability among those who did adequately follow the instructions is moderate. We advise to test the children’s understanding of the instructions prior to completion of questionnaires and recommend to not rely exclusively on a self-reported questionnaire to select, recruit, or evaluate pediatric patients for FGIDs for research purposes. (J Neurogastroenterol Motil 2021;27:626-631)

Transcriptome Analysis Unveils Gln3 Role in Amino Acids Assimilation and Fluconazole Resistance in Candida glabrata

( Francisco J. Pérez-de Los Santos ),( Luis Fernando García-ortega ),( Karina Robledo-márquez ),( Jesús Guzmán-moreno ),( Lina Riego-ruiz ) 한국미생물생명공학회(구 한국산업미생물학회) 2021 Journal of microbiology and biotechnology Vol.31 No.5

After Candida albicans, Candida glabrata is one of the most common fungal species associated with candidemia in nosocomial infections. Rapid acquisition of nutrients from the host is important for the survival of pathogens which possess the metabolic flexibility to assimilate different carbon and nitrogen compounds. In Saccharomyces cerevisiae, nitrogen assimilation is controlled through a mechanism known as Nitrogen Catabolite Repression (NCR). NCR is coordinated by the action of four GATA factors; two positive regulators, Gat1 and Gln3, and two negative regulators, Gzf3 and Dal80. A mechanism in C. glabrata similar to NCR in S. cerevisiae has not been broadly studied. We previously showed that in C. glabrata, Gln3, and not Gat1, has a major role in nitrogen assimilation as opposed to what has been observed in S. cerevisiae in which both factors regulate NCR-sensitive genes. Here, we expand the knowledge about the role of Gln3 from C. glabrata through the transcriptional analysis of BG14 and gln3Δ strains. Approximately, 53.5% of the detected genes were differentially expressed (DEG). From these DEG, amino acid metabolism and ABC transporters were two of the most enriched KEGG categories in our analysis (Up-DEG and Down-DEG, respectively). Furthermore, a positive role of Gln3 in AAA assimilation was described, as was its role in the transcriptional regulation of ARO8. Finally, an unexpected negative role of Gln3 in the gene regulation of ABC transporters CDR1 and CDR2 and its associated transcriptional regulator PDR1 was found. This observation was confirmed by a decreased susceptibility of the gln3Δ strain to fluconazole.

Potential Control of Foodborne Pathogenic Bacteria by Pediococcus pentosaceus and Lactobacillus graminis Isolated from Fresh Vegetables

C.J. González-Pérez1,I. Vargas-Arispuro,E. Aispuro-Hernández,C.L. Aguilar-Gil,Y.E. Aguirre-Guzmán,A. Castillo,A. Hernández-Mendoza,J.F. Ayala-Zavala,M.A. Martínez-Téllez1 한국미생물·생명공학회 2019 한국미생물·생명공학회지 Vol.47 No.2

The consumption of fresh vegetables has been related to recurrent outbreaks of foodborne diseases (FBD) worldwide. Therefore, the development of effective alternative technologies is necessary to improve the safety of these products. This study aimed to isolate and identify epiphytic lactic acid bacteria (LAB) from fresh fruits and leafy vegetables and characterize their antagonistic capacity due to their ability to produce bacteriocins or antibacterial compounds. For this, 92 LAB isolates from fruits and leafy vegetables were screened for antagonistic activity. Two strains with the highest and broadest antagonistic activities were selected for further characterization; one from cantaloupe melon (strain CM175) and one from cilantro leaves (strain C15). The cell-free supernatants (CFS) of CM175 and C15 were found to exhibit antagonistic activity against FBD-causing pathogens. The CM175 and C15 strains were identified as Pediococcus pentosaceus and Lactobacillus graminis, respectively. Notably, the P. pentosaceus CM175 CFS stopped the growth of Salmonella Typhimurium, Salmonella Saintpaul, Staphylococcus aureus, and Listeria monocytogenes, and delayed Escherichia coli O157:H7 growth. Moreover, L. graminis C15 CFS delayed the growth of all indicator pathogens, but did not completely stop it. Organic acids and bacteriocin-like molecules were determined to be possibly exerting the observed antagonistic activity of the identified LAB strains. Thus, application of the antagonistic compounds produced by Pediococcus pentosaceus and Lactobacillus graminis could be a novel and ecological strategy in developing antimicrobial biopreservatives for the food industry and mitigating FBD by reducing the biological contamination in fruit and vegetable orchards, mainly via their potential in controlling both gram-negative and gram-positive pathogenic bacteria.

Experimental and theoretical study of lead sulfide nanocrystals attached to nitrogen‑doped carbon nanotubes

B. Rebollo‑Plata,M. P. Sampedro,M. G. G?mez‑Espinoza,M. Guzm?n‑Altamirano,J. G. Cabal‑Velarde,O. Portillo‑Moreno,A. Lobo‑Guerrero,M. L?pez‑Fuentes,Ra?l A. Morales‑Luckie 한국탄소학회 2023 Carbon Letters Vol.33 No.1

Lead sulfide ( PbS ) nanocrystals anchored on nitrogen-doped multiwalled carbon nanotubes ( CNx ) have been synthesized employing an environmentally friendly and inexpensive wet chemistry process. CNx?PbS composites have been examined by scanning electron microscopy, X-ray diffraction and Raman spectroscopy. Theorical ab initio calculations have been developed to determine the samples structural, morphological and optical properties to explain the experimental evidences. The PbS nanoparticles exhibit of 4 nm to 27 nm particle size with a face-centered cubic crystal structure and are homogeneously distributed along the carbon nanotubes. The nitrogen-doped CNTs acts as binding sites for the PbS clusters as ab initio theoretical study suggests.