A comparison of flexible coupling models for updating in rotating machinery response

This paper analyzes the effects of the mathematical models of flexible couplings in rotating mechanical systems in terms of their vibrational behavior. The residual unbalance of the coupled shafts is considered to be the main source of vibration in the rotating system. The moments and the frequencies of the forces, which result from these effects, are close to the natural frequencies of the mechanical system. Since the coupling is considered to be a flexible component in the power transmission system, it introduces a certain amount of mass, damping and stiffness to the system, influencing its natural frequencies. The present work shows the modeling of a mechanical rotor-bearing-coupling system, through the finite element method, used in this case to analyze the transverse vibrations of the system. Different modeling techniques were taken into account for this purpose. Such models are recommended for flexible couplings to analyze their influence on the natural frequencies of the system and on the unbalance response of the system. Afterwards, a model updating was carried out to fit the coupling stiffness and damping coefficients, using the minimum quadratic technique. Some sensitivity of the proposed models was observed in relation to the coupling parameters.235246Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq

Age at First Alcohol Use and Weapon Carrying among Adolescents: Findings from the 2019 Youth Risk Behavior Survey

Background Although studies have investigated the association between alcohol use and violent behaviors such as weapon carrying, few studies have examined the association between age at first alcohol use and weapon-carrying among adolescents. The objective of this study was to investigate the association between age at first alcohol use and weapon carrying among adolescents. Methods Data for this study came from the 2019 Youth Risk Behavior Survey. An analytic sample of 13,442 adolescents aged 14–18 years old (51% female) was analyzed using binary logistic regression. The outcome variable investigated in this study was weapon carrying during the past 30 days, and the main explanatory variable investigated was age at first alcohol use. Results Of the 13,442 adolescents, 13.5% carried a weapon during the past 30 days, and 15.4% reported having their first alcoholic drink before age 13. In the multivariable logistic regression, adolescents who reported having alcohol before age 13 had more than double the odds of carrying a weapon when compared to those who never had alcohol before age 13 (AOR = 2.32, p \u3c .001, 95% CI = 1.87-2.89). Other significant factors associated with weapon carrying include male gender, victim of bullying, teen dating violence, sexual violence, suicidal ideation, and history of substance use. Adolescents who self-identified as Black/African American or Hispanic were significantly less likely to carry a weapon when compared to adolescents who self-identified as non-Hispanic White. Conclusion The findings of this study underscore the importance of developing age appropriate intervention strategies to curb early initiation of alcohol use and weapon carrying among adolescents

An Aromatic Dyad Motif in Dye Decolourising Peroxidases Has Implications for Free Radical Formation and Catalysis

Dye decolouring peroxidases (DyPs) are the most recent class of heme peroxidase to be discovered. On reacting with H2O2, DyPs form a high‐valent iron(IV)‐oxo species and a porphyrin radical (Compound I) followed by stepwise oxidation of an organic substrate. In the absence of substrate, the ferryl species decays to form transient protein‐bound radicals on redox active amino acids. Identification of radical sites in DyPs has implications for their oxidative mechanism with substrate. Using a DyP from Streptomyces lividans, referred to as DtpA, which displays low reactivity towards synthetic dyes, activation with H2O2 was explored. A Compound I EPR spectrum was detected, which in the absence of substrate decays to a protein‐bound radical EPR signal. Using a newly developed version of the Tyrosyl Radical Spectra Simulation Algorithm, the radical EPR signal was shown to arise from a pristine tyrosyl radical and not a mixed Trp/Tyr radical that has been widely reported in DyP members exhibiting high activity with synthetic dyes. The radical site was identified as Tyr374, with kinetic studies inferring that although Tyr374 is not on the electron‐transfer pathway from the dye RB19, its replacement with a Phe does severely compromise activity with other organic substrates. These findings hint at the possibility that alternative electron‐transfer pathways for substrate oxidation are operative within the DyP family. In this context, a role for a highly conserved aromatic dyad motif is discussed

Structural Basis for the Aminoacid Composition of Proteins from Halophilic Archea

In order to survive in highly saline environments, proteins from halophilic archea have evolved with biased amino acid compositions that have the capacity to reduce contacts with the solvent

A subtle structural change in the distal haem pocket has a remarkable effect on tuning hydrogen peroxide reactivity in dye decolourising peroxidases from Streptomyces lividans

Dye decolourising peroxidases (DyPs) are oxidative haem containing enzymes that can oxidise organic substrates by first reacting with hydrogen peroxide. Herein, we have focused on two DyP homologs, DtpAa and DtpA, from the soil-dwelling bacterium Streptomyces lividans. By using X-ray crystallography, stopped-flow kinetics, deuterium kinetic isotope studies and EPR spectroscopy, we show that both DyPs react with peroxide to form Compound I (a FeIV=O species and a porphyrin π-cation radical), via a common mechanism, but the reactivity and rate limits that define the mechanism are markedly different between the two homologs (DtpA forms Compound I rapidly, no kinetic isotope effect; DtpAa 100-fold slower Compound I formation and a distinct kinetic isotope effect). By determining the validated ferric X-ray structure of DtpAa and comparing it with the ferric DtpA structure, we attribute the kinetic differences to a subtle structural repositioning of the distal haem pocket Asp side chain. Through site-directed mutagenesis we show the acid-base catalyst responsible for proton-transfer to form Compound I comprises a combination of a water molecule and the distal Asp. Compound I formation in the wild-type enzymes as well as their distal Asp variants is pH dependent, sharing a common ionisation equilibrium with an apparent pKa of ~ 4.5-5.0. We attribute this pKa to the deprotonation/protonation of the haem bound H₂O₂. Our studies therefore reveal a mechanism for Compound I formation in which the rate limit may be shifted from peroxide binding to proton-transfer controlled by the distal Asp position and the associated hydrogen-bonded water molecules

Detection of Mycobacterium tuberculosis in urine by Xpert MTB/RIF Ultra: A useful adjunctive diagnostic tool in HIV-associated tuberculosis.

In January 2017, the World Health Organisation recommended the Xpert® MTB/RIF Ultra assay (Ultra) for tuberculosis (TB) diagnosis. Ultra offers improved analytical sensitivity when compared with the initial Xpert® MTB/RIF (Xpert) assay for the detection of Mycobacterium tuberculosis. Ultra is therefore likely to be of particular benefit for detecting paucibacillary TB. We present a case from Uganda demonstrating Ultra positivity in urine from an HIV-infected patient presenting with altered mental status and urinary incontinence, and no other signs of active pulmonary or extrapulmonary TB. This represents the first published instance of a diagnosis of extrapulmonary TB made on the basis of a positive urine Ultra assay. The use of Ultra on urine may be a useful addition to the diagnostic armamentarium for disseminated TB in persons with HIV co-infection. The diagnostic accuracy of urine Ultra should be characterised further via prospective studies

Three Stages of Lysozyme Thermal Stabilization by High and Medium Charge Density Anions

Addition of high and medium charge density anions (phosphate, sulfate, and chloride) to lysozyme in pure water demonstrates three stages for stabilization of the protein structure. The first two stages have a minor impact on lysozyme stability and are probably associated with direct interaction of the ions with charged and partial charges on the protein’s surface. There is a clear transition between the second and third stages; in the case of sodium chloride, disodium sulfate and disodium hydrogen phosphate this is at 550, 210, and 120 mM, respectively. Stabilization of lysozyme can be explained by the free energy required to hydrate the protein as it unfolds. At low ion concentrations, the protein’s hydration layer is at equilibrium with the bulk water. After the transition, bulk water is depleted and the protein is competing for water with the ions. With competition for water between the protein and the ions at higher salt concentrations, the free energy required to hydrate the interior of the protein rises and it is this that stabilizes the protein structure

Tissue-specific transcriptome profiling of the citrus fruit epidermis and subepidermis using laser capture microdissection

Most studies of the biochemical and regulatory pathways that are associated with, and control, fruit expansion and ripening are based on homogenized bulk tissues, and do not take into consideration the multiplicity of different cell types from which the analytes, be they transcripts, proteins or metabolites, are extracted. Consequently, potentially valuable spatial information is lost and the lower abundance cellular components that are expressed only in certain cell types can be diluted below the level of detection. In this study, laser microdissection (LMD) was used to isolate epidermal and subepidermal cells from green, expanding Citrus clementina fruit and their transcriptomes were compared using a 20k citrus cDNA microarray and quantitative real-time PCR. The results show striking differences in gene expression profiles between the two cell types, revealing specific metabolic pathways that can be related to their respective organelle composition and cell wall specialization. Microscopy provided additional evidence of tissue specialization that could be associated with the transcript profiles with distinct differences in organelle and metabolite accumulation. Subepidermis predominant genes are primarily involved in photosynthesis- and energy-related processes, as well as cell wall biosynthesis and restructuring. By contrast, the most epidermis predominant genes are related to the biosynthesis of the cuticle, flavonoids, and defence responses. Furthermore, the epidermis transcript profile showed a high proportion of genes with no known function, supporting the original hypothesis that analysis at the tissue/cell specific levels can promote gene discovery and lead to a better understanding of the specialized contribution of each tissue to fruit physiology

Dose-resolved serial synchrotron and XFEL structures of radiation-sensitive metalloproteins

An approach is demonstrated to obtain, in a sample- and time-efficient manner, multiple dose-resolved crystal structures from room-temperature protein microcrystals using identical fixed-target supports at both synchrotrons and X-ray free-electron lasers (XFELs). This approach allows direct comparison of dose-resolved serial synchrotron and damage-free XFEL serial femtosecond crystallography structures of radiation-sensitive proteins. Specifically, serial synchrotron structures of a heme peroxidase enzyme reveal that X-ray induced changes occur at far lower doses than those at which diffraction quality is compromised (the Garman limit), consistent with previous studies on the reduction of heme proteins by low X-ray doses. In these structures, a functionally relevant bond length is shown to vary rapidly as a function of absorbed dose, with all room-temperature synchrotron structures exhibiting linear deformation of the active site compared with the XFEL structure. It is demonstrated that extrapolation of dose-dependent synchrotron structures to zero dose can closely approximate the damage-free XFEL structure. This approach is widely applicable to any protein where the crystal structure is altered by the synchrotron X-ray beam and provides a solution to the urgent requirement to determine intact structures of such proteins in a high-throughput and accessible manner