University of the Andes (Chile)
  • Santiago, Las Condes, Region Metropolitana, Chile
Recent publications
This study assesses the feasibility of the incorporation of fibrillated polypropylene fibers (FPFs), an engineered multidimensional and multifilament fiber mostly used to reinforce concrete mixtures, into adobe mixtures (AMs), a traditional and manually-made material used to produce adobe blocks. The incorporation of FPFs was assessed using increasing dosages (0%, 0.25%, 0.5%, and 1% in wt% of clay soil) of FPFs. These fibers were gradually added and mixed with the clayey soil prior to incorporation of water to promote uniform mixtures with adequate fiber distribution to reduce the formation of fiber clusters. The impact of FPFs was evaluated in terms of its effects on the bulk density (physical), compressive and flexural strength (mechanical), flexural toughness indices (fracture) and water erosion resistance (durability) of AMs. Results indicate that increasing dosages of FPFs monotonically reduce average values of bulk density, as well as compressive and flexural strength of AMs. On the other hand, these increasing dosages of FPFs monotonically increase average values of water erosion resistance as well as flexural toughness indices, varying the flexural failure mode from brittle (unreinforced AM) to ductile (reinforced AMs) because of the adequate bonding and FPF-bridging effect after the crack generation as confirmed by instrumentation as well as digital image correlation evaluations implemented in this study. The significant reductions of bulk densities and compressive and flexural strengths obtained for fiber-reinforced AMs were related to the increasing number of fiber clusters found for increasing dosages of FPFs within the fiber-reinforced mixtures, which was evaluated using scanning electron microscopy analyses. For example, positively the AM incorporating 1% of FPFs increased, on average, the flexural toughness by 674% and reduced the bulk density and water erosion depth by, on average, 9% and 64%, respectively, when compared to the unreinforced AM. However, this large dosage of FPFs also generated a significant reduction of the compressive strength (60% on average) and the flexural strength (43% on average) when compared to the plain mixture. On the other hand, a small dosage of FPFs (0.25%) generated less significant improvements in terms of flexural toughness, bulk density, and water erosion (on average, increment of 58% and reductions of 2% and of 38%, respectively, when compared to the unreinforced AM). Yet, the latter mixture presented reductions, on average, of compressive and flexural strengths of 24% and 16%, respectively, when compared to the plain mixture, and these reductions were significantly smaller than the reductions obtained by the largest FPF dosage, due to the significantly smaller number of fiber clusters presented by the 0.25% dosage when compared to the 1% dosage. Finally, the mechanical performance limitations exhibited by the incorporation of FPFs, especially in large dosages, are related to generated fiber clusters due to the inherent morphology of these FPFs as well as the traditional manual confection process of AMs. Therefore, this study recommends the implementation of FPFs in AMs, but in small dosages and/or suggests the implementation of a mechanical mixing/compaction process that guarantee a more uniform fiber distribution that reduces the generation of fiber clusters.
Objective The aim was to evaluate early and medium-term outcomes of double fenestrated physician-modified endovascular grafts for total endovascular aortic arch repair. Methods This single-center retrospective analysis of prospectively-collected data included 100 patients, from January 2017 to December 2021, undergoing thoracic endovascular aortic repair (TEVAR) for zone 0. The fenestrations were a proximal larger fenestration that incorporated the brach2iocephalic trunk and left common carotid artery and a distal smaller fenestration for the left subclavian artery (LSA). Only the LSA fenestration was stented. Results The median duration for stent-graft modification was 23±6 minutes. Of the 100 patients, 70 were men. The mean patient age was 70±10.5 years. Indications for treatment included degenerative aortic arch aneurysm (n=32), dissecting aortic arch aneurysm after type A dissections (n=23) and (n=19) after type B dissections, acute complicated type B dissection (n=16), and other pathologies (n=10). Technical success rate was 97%. The 30 day mortality was 2% (n=2). Four patients (4%) had minor stroke with full recovery. One patient (1%) had a type IA endoleak, 1 patient (1%) had a type IB endoleak, and 2 patients (2%) have a type II endoleak from the LSA. Eight patients (8%) required reintervention: 1 type IA endoleak, 1 type IB endoleak, 1 retrograde type A dissection, and 5 because of access-related complications. During a mean follow-up of 24±7.2 months, there were no aortic rupture, paraplegia, and all supra-aortic trunks were patent. Conclusions Double homemade fenestrated TEVAR is both feasible and effective for total endovascular aortic arch repair avoiding the need for anatomical and extra-anatomical surgical revascularization. The long-term durability will need to be assessed in studies with long-term follow-up. Clinical Impact Double homemade fenestrated TEVAR is effective for total endovascular aortic arch repair avoiding the need for anatomical and extra-anatomical surgical revascularization. The standout feature of this double fenestrated device is its simple handling during operation with the proximal fenestrations being directed to the orifices of the BT and LCCA automatically when the LSA fenestration is catheterized and secured by covered stent placement. The deployment algorithm actively steers the operator away from superfluous manipulations of the device within the arch and avoids guidewire manipulation in carotid arteries. The long-term durability will need to be assessed in studies with long-term follow-up.
»: Anterior glenohumeral instability (AGI) is a challenging condition that requires close attention to osseous and soft-tissue abnormalities. The morphometric variance of the periarticular scapular anatomy may be involved in the pathogenesis of recurrent traumatic anterior instability. »: The Trillat procedure repositions the coracoid medially and downward by a partial wedge osteotomy, mimicking the sling effect of the Latarjet procedure by moving the conjoint tendon closer to the joint line in throwing position. The Trillat procedure decreases the coracohumeral distance without affecting the integrity of the subscapularis muscle and tendon. »: Joint preservation methods, such as the Trillat procedure, may be explored in older patients to treat AGI with simultaneous irreparable rotator cuff tears (RCTs) with a static centered head and a functional subscapularis. »: Shoulder hyperlaxity and instability can be challenging to treat with isolated soft-tissue procedures. In cases without glenoid bone loss, free bone block techniques are ineffective because of the subsequent potential graft resorption, apprehension, or recurrence. The Trillat surgery, in conjunction with an anteroinferior capsuloplasty, seems to be helpful in preventing recurrent instability and in reducing shoulder apprehension. »: Recently, several variations of the original technique have been described. In the future, anatomical, biomechanical, and clinical studies need to be conducted to further evaluate the morphometric characterization of the procedure, enhance the technical features, improve indications, and avoid coracoid impingement and other potential complications with the Trillat procedure.
Due to recent advances in machine learning, there has been an explosive development of multiple methodologies that automatically extract information from architectural floor plans. Nevertheless, the lack of a standard notation and the high variability in style and composition make it urgent to devise reliable and effective approaches to analyze and recognize objects like walls, doors, and rooms from rasterized images. For such reason, and with the aim of bringing some significant contribution to the state-of-the-art, this paper provides a critical revision of the methodologies and tools from rule-based and learning-based approaches between the years 1995 to 2021. Datasets, scopes, and algorithms were discussed to guide future developers to improve productivity and reduce costs in the construction and design industries. This study concludes that most research relies on a particular plan style, facing problems regarding generalization and comparison due to the lack of a standard metric and the limited public datasets. However, the study also highlights that combining existing tasks can be employed in various and increasing applications.
In previous publications, we showed that the incremental process of the chaotic diffusion of dissipative solitons in a prototypical complex Ginzburg-Landau equation, known, e.g., from nonlinear optics, is governed by a simple Markov process leading to an Anti-Persistent Random Walk of motion or by a more complex Hidden Markov Model with continuous output densities. In this article, we reveal the transition between these two models by examining the dependence of the soliton dynamics on the main bifurcation parameter of the cubic-quintic Ginzburg-Landau equation, and by identifying the underlying hidden Markov processes. These models capture the non-trivial decay of correlations in jump widths and sequences of symbols representing the symbolic dynamics of short and long jumps, the statistics of anti-persistent walk episodes, and the multimodal density of the jump widths. We demonstrate that there exists a physically meaningful reduction of the dynamics of an infinite-dimensional deterministic system to one of a probabilistic finite state machine and provide a deeper understanding of the soliton dynamics under parameter variation of the underlying nonlinear dynamics.
Background Previous representative health surveys conducted in Chile evidenced a high obesity prevalence rate among adults, especially in female and urban areas. Nevertheless, these have limited utility for targeted interventions and local source allocation for prevention. This study analyzes the increments in obesity prevalence rates in populations ≥15 years of age and the geographic variation at the regional level. We also assessed whether the obesity rates have different patterns on a smaller geographic level than national and regional ones. Methods This ecological study analyzed data from two representative national samples of adolescents and adults ≥15 years old, who participated in the last Chilean health surveys, 2009 (n = 5412) and 2016 (n = 6233). Obesity (body mass index≥30 kg/m²) rates were calculated on the national, regional, and Health service (HS) levels, being HS the smallest unit of analysis available. Obesity rates and relative increase to early identify target populations and geographic areas, with 95% confidence intervals (95% CI), were calculated using the sampling design of the national surveys, at the national and regional level, and by gender, age groups, and socioeconomic status. The Fay-Herriot (FH) models, using auxiliary data, were fitted for obesity rate estimates at the HS level. Results The relative increase in obesity rate was 37.1% (95%CI 23.3–52.9) at the national level, with a heterogeneous geographic distribution at the regional one. Southern regions had the highest obesity rates in both surveys (Aysén: 35.2, 95%CI 26.9–43.5 in 2009, 44.3 95%CI 37–51.7 in 2016), but higher increases were predominantly in the northern and central areas of the country (relative increase 91.1 95%CI 39.6–110.1 in Valparaiso and 81.6 95%CI 14.4–196.2 in Tarapacá). Obesity rates were higher in females, older age, and lower socioeconomic groups; nevertheless, relative increases were higher in the opposite ones. The FH estimates showed an obesity rates variation at the HS level, where higher rates tend to converge to specific HS areas of each region. Conclusion Obesity rates and relative increase are diverse across subnational levels and substantially differ from the national estimates, highlighting a pattern that converges to areas with low-middle income households. Our results emphasize geographical disparities in obesity prevalence among adults and adolescents.
Background: Predictive genetic tests are presently effective over several medical conditions, increasing the demand among patients and healthy individuals. Considering the psychological burden suspected familial dementia may carry on individuals, assessing personality, coping strategies, and mental health could aid clinicians in findings the appropriate time for delivering genetic test results and predict compliance regarding genetic counseling and expectations towards the genetic condition depending on the outcome. Objective: To describe the psychiatric, psychological, and coping characteristics of a sample of Spanish individuals at risk of familial dementia before genetic test results were given. Methods: We included 54 first degree relatives of patients diagnosed with Alzheimer’s disease, lobar frontotemporal degeneration, or prion diseases. The NEO-FFI-R, COPE, and HADS tests evaluated personality, coping strategies, and psychological distress, respectively. Results: Anxiety and depression were below the cut-off point for mild severity. Conscientiousness and Agreeableness were the most preponderant personality factors, while Neuroticism was the least. Positive reinterpretation and Acceptance were the most frequent coping strategies, and Denial and Alcohol and drug use were the least used. Ongoing medical pathologies increased depression, while psychiatric disorders worsened psychological distress. Conclusion: Contrary to our expectations, PICOGEN candidates showed psychological distress and personality traits within normative ranges, and the use of problem-focused coping strategies prevailed over avoidance coping strategies. Nevertheless, clinicians should pay particular attention to individuals attending genetic counseling who are women, aged, and present an ongoing psychiatric disorder and psychiatric history at inclusion to ensure their mental health and adherence throughout the process.
The subject of calculating the topological charge (TC) or vortex strength of optical vortices has generated divided opinions among scientists. This is due to the fact that proper analytical results are hard to support from the experimental point of view, leading to different results and conclusions. In this work we will present numerical data that shows the limits of TC measurements for practical fractional vortices and the possible challenges that high order measurements may pose. By analyzing the far field phase and the behavior of the transitions we have shown that they follow specific curves that depend not only on the TC but also on the beam waist. This leads us to present a new “strength staircase” for practical vortices. Our aim is to give some insight in practical scenarios that have not been taken into account in previous results.
Fats play multiple roles in determining the desirable characteristics of foods. However, there are health concerns about saturated and trans fats. Bigels have been proposed as a novel fat replacer in foods. This research evaluated the role of the type of hydrogel in the development of bigels to be used as fat replacers in cookies. Bigels were made with beeswax/canola oil oleogel and sodium alginate and carboxymethylcellulose hydrogels. The results showed that the peroxide value and binding capacity of bigels were affected by the type of hydrogel used. However, their fatty acid profile, p-anisidine value, oxidative stability, and texture remained unchanged. Using bigels as fat replacers, cookies were obtained with a hardness similar to those with original shortening, showing the potential of bigels for use in foods.
Background There is controversy regarding the treatment of symptomatic synovial cysts, specifically, the need for a concomitant fusion when surgical resection of the synovial cysts is required. We present a retrospective review of a series of patients treated for symptomatic synovial cysts of the lumbar region during the last 20 years by a single surgeon, analyzing the current available literature. Methods Retrospective review. The same surgical technique was applied to all patients. Demographic, clinical, surgical data and synovial cyst recurrence rate were recorded. Postoperative results reported by patients were documented according to the McNab score. Results Sixty nine subjects, with mean follow-up of 7.4 years. 62% (43) were female, with a mean 57.8 years at the time of surgery. In 91.3% (63), the primary management was conservative for a minimum period of 3 months. All subjects underwent surgery due to the failure of conservative treatment. The segment most operated on was L4–L5 (63.77%). 91.3% (63) of the sample reported excellent and good and 6 subjects (8.6%) fair or poor results. There was no evidence of synovial cysts recurrence at the operated level. Conclusion In symptomatic synovial cysts, it seems that conservative treatment is only effective in a limited number of patients and in the short term. Thus, the recommendation of a surgical indication should proceed as soon as the conservative management fails to result in significant symptom relief. Based on our results, we recommend, together with the resection of the cyst, the instrumentation of the segment to avoid its recurrence and the management of axial pain.
The E3 ubiquitin ligase RNF12 plays essential roles during development, and the gene encoding it, RLIM , is mutated in the X-linked human developmental disorder Tonne-Kalscheuer syndrome (TOKAS). Substrates of RNF12 include transcriptional regulators such as the pluripotency-associated transcriptional repressor REX1. Using global quantitative proteomics in male mouse embryonic stem cells, we identified the deubiquitylase USP26 as a putative downstream target of RNF12 activity. RNF12 relieved REX1-mediated repression of Usp26 , leading to an increase in USP26 abundance and the formation of RNF12-USP26 complexes. Interaction with USP26 prevented RNF12 autoubiquitylation and proteasomal degradation, thereby establishing a transcriptional feed-forward loop that amplified RNF12-dependent derepression of REX1 targets. We showed that the RNF12-USP26 axis operated specifically in mouse testes and was required for the expression of gametogenesis genes and for germ cell differentiation in vitro. Furthermore, this RNF12-USP26 axis was disrupted by RLIM and USP26 variants found in TOKAS and infertility patients, respectively. This work reveals synergy within the ubiquitylation cycle that controls a key developmental process in gametogenesis and that is disrupted in human genetic disorders.
Nonlinear finite-element model updating (FEMU) is a promising approach for post-event damage assessment of civil structures. This paper conducted FEMU for a full-scale reinforced concrete bridge column tested under a sequence of earthquakes and examined the evolution of seismic damage across different earthquake ground motions. It was found that using experimental data, FEMU can be applied to identify unknown key model parameters (e.g. bond-slip and core concrete parameters) and damage of the columns as represented by the change of the key parameters. In addition, the updated models demonstrated their ability to better predict the system response for future earthquakes.
Resumen Objetivos Determinar la prevalencia de déficit de vitamina D, así como evaluar la seguridad y efectividad de un nuevo método de carga con colecalciferol en pacientes adultos con fractura de tibia. Materiales y Métodos Se reclutaron a 56 pacientes consecutivos con edades entre 18 y 65 años con fractura de tibia ingresados en nuestro hospital durante 1 año. Se determinó el nivel de 25-hidroxivitamina D ([25(OH)-D]) al ingreso y tras suplementación con 100.000 UI semanales de colecalciferol, durante 3 o 5 semanas, en casos de insuficiencia ([25(OH)-D] entre 20 ng/mL y 29,9 ng/mL) o deficiencia ([25(OH)-D] < 20 ng/mL), respectivamente. Se determinó la prevalencia de hipovitaminosis D, el porcentaje de normalización de [25(OH)-D], y los efectos adversos. Resultados Se evaluaron 56 pacientes; 98,2% presentó hipovitaminosis D, y 28 (73,7%) y 10 (26,3%) presentaron déficit e insuficiencia, respectivamente. Tras la suplementación, 92,1% alcanzaron niveles [25(OH)-D] normales. Ningún paciente presentó efectos adversos. Discusión La prevalencia de deficiencia de vitamina D en nuestra población fue mayor a la reportada en la literatura. Comprobamos que un esquema de suplementación en altas dosis de vitamina D es seguro, y más efectivo que los previamente recomendados. Este esquema de suplementación puede ser implementado en futuros estudios randomizados. Conclusión La prevalencia de hipovitaminosis D en pacientes adultos chilenos con fractura de tibia fue alta (98,2%). El esquema de suplementación con vitamina D propuesto fue efectivo y seguro. Nivel de Evidencia Estudio terapéutico. Nivel 2.
Fractional vortex beams (FVBs) possess unique topological properties that are manifested in the vortex distribution. However, there are still discrepancies in the value of the vortex strength of FVBs at the far field. In this work we present a complete picture of the behavior of the phase singularities of non-integer (commonly known as fractional) beams in the Fraunhofer diffraction region and demonstrate a very good correspondence between experiments and simulations. As shown in the text, the original beam waist ω0 was found to be a key factor relating to the beam profile topology. This variable was measured in the process of calibrating the experiment. Finally, an experimental method to obtain the non-integer topological charge is proposed. This method only requires an analysis of the intensity, knowledge of the transition behaviors, and the beam waist.
Currently, researchers are focused on the study of cytokines as predictive biomarkers of peri-implantitis (PI) in order to obtain an early diagnosis and prognosis, and for treatment of the disease. The aim of the study was to characterize the peri-implant soft and hard tissues in patients with a peri-implantitis diagnosis. A descriptive observational study was conducted. Fifteen soft tissue (ST) samples and six peri-implant bone tissue (BT) samples were obtained from 13 patients who were diagnosed with peri-implantitis. All the samples were processed and embedded in paraffin for histological and immunohistochemical analyses. A descriptive and quantitative analysis of mast cells and osteocytes, A proliferation-inducing ligand (APRIL), B-cell activating factor (BAFF), osteonectin (ON), and ∝-smooth muscle actin (∝-SMA) was performed. We observed the presence of mast cells in peri-implant soft tissue in all samples (mean 9.21 number of mast cells) and osteocytes in peri-implant hard tissue in all samples (mean 37.17 number of osteocytes). The expression of APRIL-ST was 32.17% ± 6.39%, and that of APRIL-BT was 7.09% ± 5.94%. The BAFF-ST expression was 17.26 ± 12.90%, and the BAFF-BT was 12.16% ± 6.30%. The mean percentage of ON was 7.93% ± 3.79%, and ∝-SMA was 1.78% ± 3.79%. It was concluded that the expression of APRIL and BAFF suggests their involvement in the bone resorption observed in peri-implantitis. The lower expression of osteonectin in the peri-implant bone tissue can also be associated with a deficiency in the regulation of bone remodeling and the consequent peri-implant bone loss.
Case: A 49-year-old highly active man had a direct fall on the left shoulder, causing a chronic locked posterior shoulder dislocation. Radiographic analysis revealed a reverse Hill-Sachs lesion (RHSL) that affected 31% of the articular surface. He was successfully treated with a modified McLaughlin procedure that included a double-row suture anchor as a novel fixation approach to secure the lesser tuberosity transfer and the subscapularis tenodesis. Conclusion: The reported approach for reconstructing the RHSL provides adequate stability, pain reduction, and functional outcomes. It may be considered as an option for joint preservation in extensive humeral head defects.
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2,740 members
Gustavo Moncada
  • Oral Rehabilitation
Alberto Vergara-Fernández
  • Faculty of Engineering and Applied Sciences
Patricia Luz
  • Faculty of Medicine
Pelusa Orellana
  • School of Education
Jaime E Cisternas
  • Faculty of Engineering and Applied Sciences
Mons. Álvaro del Portillo #12455, 7620001, Santiago, Las Condes, Region Metropolitana, Chile
Head of institution
José Antonio Guzmán, PhD
( 56-2 ) 2618 1000