168 research outputs found
Optimization of the investment casting process
Rapid prototyping is an important technique for manufacturing. This work refers to the manufacture of hollow patterns made of polymeric materials by rapid prototyping technologies for its use in the preparation of ceramic molds in the investment casting process. This work is focused on the development of a process for manufacturing patterns different from those that currently exist due to its hollow interior design, allowing its direct use in the fabrication of ceramic molds; avoiding cracking and fracture during the investment casting process, which is an important process for the foundry industry
Optimiranje postupka kalupljenja u ljevaÄŤkom procesu
Rapid prototyping is an important technique for manufacturing. This work refers to the manufacture of hollow patterns made of polymeric materials by rapid prototyping technologies for its use in the preparation of ceramic molds in the investment casting process. This work is focused on the development of a process for manufacturing patterns different from those that currently exist due to its hollow interior design, allowing its direct use in the fabrication of ceramic molds; avoiding cracking and fracture during the investment casting process, which is an important process for the foundry industry.Brzo razvijanje prototipa važna je proizvodna tehnika. Ovaj se rad odnosi na proizvodnju šupljih kalupa izrađenih od polimerskih materijala pomoću tehnologija brzog razvijanja prototipa za uporabu u izradi keramičkih modela u postupku kalupljenja ljevačkog procesa. Ovaj rad je usmjeren na razvijanje postupka za proizvodnju kalupa drukčijih od onih kakvi trenutno postoje i to zbog svoje šuplje unutarnje izvedbe čime se omogućava izravna uporaba u izradi keramičkih modela te se izbje gava pucanje i lom tijekom postupka kalupljenja ljevačkog procesa koji predstavlja važan postupak u ljevaoničkoj industriji
Study of process parameters on aluminium foam formation in the Al-6Si-3Mg alloy
The aim of this research was to study the process parameters that promote foam formation by injecting N2 into Al-6Si-3Mg wt % molten alloy with silicon carbide particles additions (SiC). An experimental design was proposed, in which the contents of SiC particles were 0, 10, 30 and 50 wt %, and the overheating was defined as ΔT= TF - TL , where TL is the liquidus temperature and was determined by the cooling curve method and the foaming temperatures were selected as TF at 630, 610, 580 and 570 °C. Flow and pressure of air blow were constant, 2,0 lt/min and 4,0 atm, respectively. The foam formation was possible only under two experimental conditions, 10 wt % SiC at ΔT > 12 °C and 30 wt % SiC at ΔT > 10 °C. The foams obtained under these conditions were stable, while with other conditions of experiments, bubble coallesence occurred. Finally, it was concluded that the foam formation occurred by SiC contents lower than 30 wt % SiC and temperatures slightly above the liquidus
Ion channels and neuronal excitability in polyglutamine neurodegenerative diseases
Abstract
Polyglutamine (polyQ) diseases are a family composed of nine neurodegenerative inherited disorders (NDDs) caused by pathological expansions of cytosine-adenine-guanine (CAG) trinucleotide repeats which encode a polyQ tract in the corresponding proteins. CAG polyQ repeat expansions produce neurodegeneration via multiple downstream mechanisms; among those the neuronal activity underlying the ion channels is affected directly by specific channelopathies or indirectly by secondary dysregulation. In both cases, the altered excitability underlies to gain- or loss-of-function pathological effects. Here we summarize the repertoire of ion channels in polyQ NDDs emphasizing the biophysical features of neuronal excitability and their pathogenic role. The aim of this review is to point out the value of a deeper understanding of those functional mechanisms and processes as crucial elements for the designing and targeting of novel therapeutic avenues
Impact of a Costello Syndrome-Causing Mutation on Learning and Myelin-Producing Cells
Background:Costello Syndrome (CS) is a rare genetic disorder caused by hyperactivating mutations in the HRAS gene, which controls the RAS/MAPK intracellular pathway. Symptoms of CS typically include neurocognitive developmental delays, increased risk of autism spectrum disorder, intellectual disabilities, and other neurological issues. Additionally, most CS patients present with white matter (WM) abnormalities. WM has been proposed to regulate learning due to its roles in increasing/synchronizing action potentials and protecting neuronal axons. Females of a myelin-focused mouse model of CS (PlpCre;HRasG12V; pHRas) show learning deficits in a myelin-regulated test (the complex running wheel; CW) that resolve with time. To shed light onto the mechanisms of these learning deficits, the goal of our study is to describe changes in oligodendrocyte (OL; myelin-producing cells) lineage cells in pHRas mice.
Methods: To correlate the cellular and functional impact of HRas mutation on OL lineage (OLL) cells, HRas mutation was induced in mature OLs (mOL) using a tamoxifen-inducible system. Four months after recombination, mice were subjected to the voluntary CW test (a wheel with unevenly spaced rungs), and learning curves were analyzed. An acquisition phase of 14 days was followed by a break from CWs of 3 weeks and a second CW phase of 7 days (memory of skills acquired). After the second exposure to the CW, mice were euthanized, and brain sections were collected for staining with DAPI (nucleated cells), GFP (recombinant cells), PDGFRα (oligodendrocyte precursor cells; OPCs), and Sox10 (OLL cells). Then, cell quantification was performed after conducting confocal imaging. Seven regions of the corpus callosum, across 4 coronal sections, were analyzed for regional differences in the numbers of PDGFR+ OPCs and Sox10+ OLL cells.
Results: Our antecedents show that at 2 weeks and 2 months post-mutation, there were significant decreases in distance, average speed, and max speed ran, as well as activity in mutant mice compared to WTs (defective learning curves). However, at 4 months post-mutation, there were no significant differences in learning curves between mutant and WT mice. We then wondered how OPC populations remained at 4 months post-tamoxifen when differences in behavioral phenotypes were no longer detected. We observed that the number of PDGFR+ OPCs decreased in the lateral region of the most anterior coronal section of the corpus callosum, suggesting non-cell-autonomous effects of pHRas on proliferation and/or differentiation of OPCs.
Conclusion: Taken together, our results shed light on the role of the HRas mutation on CS mouse models that show transient learning deficits on the CW after the induction of the mutation. Our working hypothesis is that decreased number of OPCs may be a result of an increase in their differentiation into mOLs (to form myelin that restores learning) but lead to a proliferative exhaustion state. We propose an immediate impact (weeks) of HRas mutation on learning that is ameliorated by OPC differentiation \u3c 4 months post-injection. Finding the mechanism of these events can aid in the understanding of this disease and in designing therapeutic treatments based on restoration of myelin function
Quinupristin/dalfopristin in Staphylococcus aureus endophthalmitis: a case report
<p>Abstract</p> <p>Introduction</p> <p>The intravitreal injection of antibiotics remains the mainstay of therapy for postoperative endophthalmitis. Bacterial resistance, however, is still a pitfall in achieving an adequate response to treatment. Quinupristin/dalfopristin might be a feasible therapeutic option in these cases.</p> <p>Case presentation</p> <p>A 55-year-old Hispanic man had endophthalmitis secondary to <it>Staphylococcus aureus </it>in his right eye and was treated with intravitreal 0.4 mg/0.1 ml quinupristin/dalfopristin injection. Inflammation and pain remission were observed at four days after injection. The final best-corrected visual acuity was 20/40.</p> <p>Conclusion</p> <p>Although vancomycin remains the first-line intravitreal antibiotic therapy against infectious endophthalmitis caused by Gram-positive bacteria, quinupristin/dalfopristin exhibits similar efficacy and is theoretically more active against vancomycin-resistant strains, with no apparent retinal toxicity.</p
3D characterization of CdSe nanoparticles attached to carbon nanotubes
The crystallographic structure of CdSe nanoparticles attached to carbon
nanotubes has been elucidated by means of high resolution transmission electron
microscopy and high angle annular dark field scanning transmission electron
microscopy tomography. CdSe rod-like nanoparticles, grown in solution together
with carbon nanotubes, undergo a morphological transformation and become
attached to the carbon surface. Electron tomography reveals that the
nanoparticles are hexagonal-based with the (001) planes epitaxially matched to
the outer graphene layer.Comment: 7 pages, 8 figure
In-Vivo Hyperspectral Human Brain Image Database for Brain Cancer Detection
The use of hyperspectral imaging for medical applications is becoming more
common in recent years. One of the main obstacles that researchers find when
developing hyperspectral algorithms for medical applications is the lack of
specific, publicly available, and hyperspectral medical data. The work
described in this paper was developed within the framework of the European
project HELICoiD (HypErspectraL Imaging Cancer Detection), which had as a main
goal the application of hyperspectral imaging to the delineation of brain
tumors in real-time during neurosurgical operations. In this paper, the
methodology followed to generate the first hyperspectral database of in-vivo
human brain tissues is presented. Data was acquired employing a customized
hyperspectral acquisition system capable of capturing information in the Visual
and Near InfraRed (VNIR) range from 400 to 1000 nm. Repeatability was assessed
for the cases where two images of the same scene were captured consecutively.
The analysis reveals that the system works more efficiently in the spectral
range between 450 and 900 nm. A total of 36 hyperspectral images from 22
different patients were obtained. From these data, more than 300 000 spectral
signatures were labeled employing a semi-automatic methodology based on the
spectral angle mapper algorithm. Four different classes were defined: normal
tissue, tumor tissue, blood vessel, and background elements. All the
hyperspectral data has been made available in a public repository.Comment: 19 pages, 12 figure
Detrimental Effects of Non-Functional Spermatozoa on the Freezability of Functional Spermatozoa from Boar Ejaculate
In the present study, the impact of non-functional spermatozoa on the cryopreservation success of functional boar spermatozoa was evaluated. Fifteen sperm-rich ejaculate fractions collected from five fertile boars were frozen with different proportions of induced non-functional sperm (0 –native semen sample-, 25, 50 and 75% non-functional spermatozoa). After thawing, the recovery of motile and viable spermatozoa was assessed, and the functional of the spermatozoa was evaluated from plasma membrane fluidity and intracellular reactive oxygen species (ROS) generation upon exposure to capacitation conditions. In addition, the lipid peroxidation of the plasma membrane was assessed by the indirect measurement of malondialdehyde (MDA) generation. The normalized (with respect to a native semen sample) sperm motility (assessed by CASA) and viability (cytometrically assessed after staining with Hoechst 33342, propidium iodide and fluorescein-conjugated peanut agglutinin) decreased (p<0.01) as the proportion of functional spermatozoa in the semen samples before freezing decreased, irrespective of the semen donor. However, the magnitude of the effect differed (p<0.01) among boars. Moreover, semen samples with the largest non-functional sperm subpopulation before freezing showed the highest (p<0.01) levels of MDA after thawing. The thawed viable spermatozoa of semen samples with a high proportion of non-functional spermatozoa before freezing were also functionally different from those of samples with a low proportion of non-functional spermatozoa. These differences consisted of higher (p<0.01) levels of intracellular ROS generation (assessed with 5-(and-6) chloromethyl-20,70-dichlorodihydrofluorescein diacetate acetyl ester; CM-H2DCFDA) and increased (p<0.01) membrane fluidity (assessed with Merocyanine 540). These findings indicate that non-functional spermatozoa in the semen samples before freezing negatively influence the freezability of functional spermatozoa
Desarrollo multidisciplinario en investigaciĂłn y docencia del centro universitario UAEM Valle de MĂ©xico
DESARROLLO MULTIDISCIPLINARIO EN INVESTIGACIĂ“N Y DOCENCIA DEL CENTRO UNIVERSITARIO UAEM VALLE DE MÉXICOLa Universidad AutĂłnoma del Estado de MĂ©xico ha evolucionado a travĂ©s de sus 188 años de historia, dedicada a la educaciĂłn, la investigaciĂłn, la cultura y el deporte, como sus grandes ejes rectores, formadora de hombres y mujeres con un alto sentido humanista y Ă©tico, contribuyendo a lograr nuevas y mejores formas de existencia y convivencia social. Durante el proceso de desconcentraciĂłn de la UAEM, se crearon las Unidades AcadĂ©micas y Centros Universitarios para brindar el servicio de educaciĂłn a más jĂłvenes en todo el Estado de MĂ©xico, este Centro Universitario fue uno de los primeros y a sus veinte años de existencia se está consolidando como uno de los mejores. Es en los Ăşltimos años que se ha venido impulsando la investigaciĂłn al contar con cuerpos acadĂ©micos, en formaciĂłn y en consolidaciĂłn, con infraestructura de primera tanto en equipo como en laboratorios especializados, con profesores de tiempo completo que participan en congresos, seminarios y presentan publicaciones en revistas indexadas. Por ello para celebrar esos veinte años de existencia de esta honorable instituciĂłn, se planeĂł la compilaciĂłn de esta obra que es parte del quehacer multidisciplinario en investigaciĂłn y docencia como parte del Plan de Desarrollo 2013-2017, de esta administraciĂłn. Esta obra reĂşne investigaciones tanto de profesores como de alumnos desde las diferentes ramas del saber en las que se inscriben sus siete licenciaturas, ActuarĂa, AdministraciĂłn, ContadurĂa, Derecho, EconomĂa, Relaciones EconĂłmicas Internacionales e Informática Administrativa, tanto presencial como a distancia, asĂ como sus tres ingenierĂas, Industrial, en ComputaciĂłn y Sistemas y Comunicaciones, asĂ como gracias a la vinculaciĂłn y colaboraciĂłn acadĂ©mico – cientĂfica que se tiene con otras instituciones de educaciĂłn superior a nivel nacional, como el Instituto TecnolĂłgico de Orizaba, la Universidad AutĂłnoma de San Luis PotosĂ, la Universidad Nacional AutĂłnoma de MĂ©xico, la Universidad AutĂłnoma Metropolitana, Universidad PolitĂ©cnica de Victoria, el Instituto PolitĂ©cnico Nacional entre otras. En el capĂtulo 1 se abordan seis temáticas diferentes de vanguardia en el área de las IngenierĂas, en los capĂtulos 2 y 3 se incluyen temas de interĂ©s y gran relevancia en materia de ciencias sociales, polĂtica y economĂa. Se hace extensivo un reconocimiento para todos los que participaron tanto en la revisiĂłn de los trabajos, como en la compilaciĂłn del producto final de este Libro intitulado “Desarrollo Multidisciplinario en InvestigaciĂłn y Docencia del Centro Universitario UAEM Valle de MĂ©xico”
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