Publications by authors named "David Contreras"

Our aim was to evaluate a foster cow-calf rearing system on the adoption or acceptance of fostered calves, milk production and udder health, as well as calf health and weight gain, and to compare this fostering system to traditional rearing. The foster group (FG) consisted of 8 cows each suckling 3 fostered calves with continuous contact. The control group (CG) was a conventional milking system, whereby cows and control calves were kept separate.

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The surface-assisted assembly of DNA origami lattices is a potent method for creating molecular lithography masks. Lattice quality and assembly kinetics are controlled by various environmental parameters, including the employed surface, the assembly temperature, and the ionic composition of the buffer, with optimized parameter combinations resulting in highly ordered lattices that can span surface areas of several cm. Established assembly protocols, however, employ assembly times ranging from hours to days.

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This work examines the photocatalytic capacity of FeO-TiO catalysts for inactivating Enterococcus faecalis in water and compares it to a peroxide-assisted process. The influence of HO, PMS, pH, and temperature is assessed. Material stability and free radical species involved in disinfection are also evaluated.

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The aim of this study was to compare the levels of reactive oxygen species (ROS) in and embryos cryopreserved using either slow freezing or vitrification. Embryos were divided into four groups based on subspecies and freezing method: slow freezing (BiSF; = 8), vitrification (BiVT; = 10), slow freezing (BtSF; = 9), and vitrification (BtVT; = 6). After thawing, the embryos were incubated with CellRox Green and images were obtained using a confocal microscope.

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Saxitoxin (STX) represents a marine toxin of significant concern due to its deleterious implications for aquatic ecosystems and public food safety. As a potent paralytic agent, the role of STX in obstructing voltage-gated sodium channels (VGSCs) is well-characterized. Yet, the mechanistic details underlying its low-dose toxicity remain largely enigmatic.

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Carbazole and triphenylamine, are two well-known hole transporting units that are attached to electron transporting unit 4,5-diazafluorene in a fascinating way to bring out non-planar configuration of a molecule. The synthesized compound exhibits good thermal stability (T > 515 °C) and high glass transition temperature (T, 191 °C). Optical bandgap (E) obtained from solid state absorption spectra was calculated to be 2.

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Article Synopsis
  • The Mexican government initiated the Seguro Popular program in 2003 to improve health care access for the poor, but it was replaced by INSABI in 2019 amidst the COVID-19 pandemic.
  • The percentage of uninsured households nearly doubled from 2018 to 2020, leading to significant increases in catastrophic and excessive health expenditures, especially among those without insurance.
  • Almost all Mexican states experienced a rise in excessive health expenses, with the most severe impacts noted in central and southern regions of the country.
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The catalytic oxidation of phenethoxybenzene as a lignin model compound with a β-O-4 bond was conducted using the Keggin-type polyoxometalate nanocatalyst (TBA)[PMoVO]. The optimization of the process's operational conditions was carried out using response surface methodology. The statistically significant variables in the process were determined using a fractional factorial design.

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The Fenton and Fenton-like reactions are based on the decomposition of hydrogen peroxide catalyzed by Fe(II), primarily producing highly oxidizing hydroxyl radicals (HO∙). While HO∙ is the main oxidizing species in these reactions, Fe(IV) (FeO) generation has been reported as one of the primary oxidants. FeO has a longer lifetime than HO∙ and can remove two electrons from a substrate, making it a critical oxidant that may be more efficient than HO∙.

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Context: Patients' mental health has been recognized as important in providing patient-centered care in athletic training.

Objective: To evaluate stress, sport anxiety, neuroticism, and coping in student-athletes.

Design: Cross-sectional study.

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Polyphenols are bioactive substances that participate in the prevention of chronic illnesses. High content has been described in G. Forst (calafate), a wild berry extensively distributed in Chilean-Argentine Patagonia.

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Adolescent social conditions profoundly affect vulnerability to drug abuse. Preclinical studies have shown that preventing social interactions during adolescence increases the rewarding effects of drugs like alcohol, cocaine, or amphetamines, however, little data exist regarding the impact of social isolation on nicotine effects. The current study evaluated the effects of differential rearing conditions during adolescence (isolation or group rearing) on (1) conditioned place preference induced by low nicotine doses (0.

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A sensitive electroanalytical method for the determination of arsenite, based on a heterostructure of aminated multiwalled carbon nanotubes and gold nanoparticles, was applied in an electrocoagulation (EC) treatment for the elimination of arsenite. A sensitive quantitative response was obtained in the determination of As in a secondary effluent from a wastewater treatment plant from Santiago (Chile). The preconcentration stage was optimized through a Central Composite Face design, and the most sensitive peak current was obtained at 200 s and -600 mV of time and accumulation potential, respectively, after a differential pulse voltammetry sweep.

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The interactions and the protective effect of the carotenoid crocin (CRO) on human erythrocytes (RBC) and molecular models of its membrane were investigated. The latter consisted of bilayers of dimyristoylphosphatidylcholine (DMPC) and dimyristoylphosphatidylethanolamine (DMPE), representative of phospholipid classes located in the outer and inner monolayers of the RBC membrane, respectively. X-ray diffraction, differential scanning calorimetry (DSC) and electronic paramagnetic resonance spectroscopy (EPR) showed that CRO produced structural perturbations in DMPC bilayers and in isolated unsealed human erythrocyte membranes.

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Rare earth (RE- Pr, Er and Nd) doped ZnO nanostructures were prepared through simple wet chemical precipitation route. The RE doping induced interesting morphological transition from spherical to flower like structures were analyzed. The X-ray diffraction (XRD) measurements revealed that the prepared materials were of highly crystalline in nature and RE dopant ions did not altered the crystal structure of ZnO.

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Article Synopsis
  • The study focuses on a bacteria that causes piscirickettsiosis, a widespread disease affecting salmon in Chilean farms, and explores how bacteria use acyl-homoserine lactones (AHLs) for communication to regulate important biological functions.* -
  • Researchers combined a fluorescent biosensor and gas chromatography-mass spectrometry (GC/MS) to successfully detect AHLs produced by specific bacterial strains, confirming the presence of N-acetyl-L-homoserine Lactone.* -
  • The findings suggest the possibility of an alternate pathway for AHL synthesis, highlighting the need for further research to understand this crucial bacterial process better.*
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Relapsing polychondritis (RP) is a rare and, if not treated, potentially lethal autoimmune disorder. Involvement of central nervous system (CNS) in RP is rare and, when present, makes it extremely difficult to diagnose. In this report, we present a case of a 22-year-old Hispanic woman who presented with sudden onset of headache and blurred vision.

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Small community cattle farmers in the tropics are facing challenges to deliver quality products whilst under pressure to increase milk and beef yields per cow. These challenges could be partially met by crossbreeding Bos taurus with Bos indicus (F1) cattle utilizing embryo transfer (ET) technology. The Bos taurus infusion would increase milk production, whilst the Bos indicus influence can improve resistance to the harsh environment of the tropics.

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Background: The communication between the brain and the immune system is a cornerstone in animal physiology. This interaction is mediated by immune factors acting in both health and pathogenesis, but it is unclear how these systems molecularly and mechanistically communicate under changing environmental conditions. Behavioural fever is a well-conserved immune response that promotes dramatic changes in gene expression patterns during ectotherms' thermoregulatory adaptation, including those orchestrating inflammation.

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Lemierre syndrome was first documented in the literature in 1936, and is defined as septic thrombophlebitis of the internal jugular vein. It is typically a result of oropharyngeal infection causing local soft tissue inflammation, which spreads to vasculature, and promotes formation of septic thrombi within the lumen, persistent bacteremia, and septic emboli. We present the case of a 24-year-old incarcerated man, who presented with leukocytosis and a right-sided tender, swollen neck after undergoing left mandibular molar extraction for an infected tooth.

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Diabetic muscle infarction (DMI) is a rare complication of poorly controlled type 1 and type 2 diabetes seen mostly in those who have already experienced microvascular complications. Currently, the incidence and prevalence of DMI are difficult to conclude, and there is no clear algorithm or standard of care in managing this condition. Pathogenesis of the microangiopathy of DMI remains unclear.

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The increasing occurrence of cyanobacterial blooms worldwide represents an important threat for both the environment and public health. In this context, the development of risk analysis and management tools as well as sustainable and cost-effective treatment processes is essential. The research project TALGENTOX, funded by the Ibero-American Science and Technology Program for Development (CYTED-2019), aims to address this ambitious challenge in countries with different environmental and social conditions within the Ibero-American context.

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Epirubicin is a cytotoxic drug used in the treatment of different types of cancer and increasing evidence suggests that its target is cell membranes. In order to gain insight on its toxic effects, intact red blood cells (RBC), human erythrocyte membranes and molecular models were used. The latter consisted in bilayers of dimyristoylphosphatidylcholine (DMPC) and dimyristoylphosphatidylethanolamine (DMPE), phospholipid classes found mainly in the outer and inner monolayers of the human erythrocyte membrane, respectively.

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Background: Different natural substances, chitosan, inactive dry yeasts and freeze-dried aqueous extracts from two wine industry by-products (stems and shoots) were used in red winemaking as possible alternatives to SO . The resistance to oxidation of wines was evaluated by electron paramagnetic resonance. The phenolic composition of wines was analyzed by high-performance liquid chromatography-diode array detection/electrospray ionization mass spectrometry, antioxidant activity was determined by DPPH (1,1-diphenyl-2-picrylhydrazyl radical) and ABTS [2,2'-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) radical cation] assays and spectrophotometric measurements of color were compared.

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The potential of different natural antioxidants to inhibit the 1-hydroxyethyl radical formation in SO-free wines was analyzed by electron paramagnetic resonance (EPR). Chitosan, glutathione, inactive dry yeast, oak and grape seed extracts, and ascorbic acid were tested in white and red wines. The ability of these substances to prevent the formation of acetaldehyde after the Fenton reaction and the oxygen consumption capacity were measured.

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