Industrial University of Santander
  • Bucaramanga, Santander, Colombia
Recent publications
Background Pressure injuries (PIs), especially in the sacral region are frequent, costly, and increase morbidity and mortality of patients in an intensive care unit (ICU). These injuries can occur as a result of prolonged pressure and/or shear forces. Neuromuscular electrical stimulation (NMES) can increase muscle mass and improve local circulation, potentially reducing the incidence of PI. Methods We performed a randomized controlled trial to assess the efficacy and safety of NMES in preventing PI in critically ill patients. We included patients with a period of less than 48 h in the ICU, aged ≥ 18 years. Participants were randomly selected (1:1 ratio) to receive NMES and usual care (NMES group) or only usual care (control group—CG) until discharge, death, or onset of a PI. To assess the effectiveness of NMES, we calculated the relative risk (RR) and number needed to treat (NNT). We assessed the muscle thickness of the gluteus maximus by ultrasonography. To assess safety, we analyzed the effects of NMES on vital signs and checked for the presence of skin burns in the stimulated areas. Clinical outcomes were assessed by time on mechanical ventilation, ICU mortality rate, and length of stay in the ICU. Results We enrolled 149 participants, 76 in the NMES group. PIs were present in 26 (35.6%) patients in the CG and 4 (5.3%) in the NMES group ( p ˂ 0.001). The NMES group had an RR = 0.15 (95% CI 0.05–0.40) to develop a PI, NNT = 3.3 (95% CI 2.3–5.9). Moreover, the NMES group presented a shorter length of stay in the ICU: Δ = − 1.8 ± 1.2 days, p = 0.04. There was no significant difference in gluteus maximus thickness between groups (CG: Δ = − 0.37 ± 1.2 cm vs. NMES group: Δ = 0 ± 0.98 cm, p = 0.33). NMES did not promote deleterious changes in vital signs and we did not detect skin burns. Conclusions NMES is an effective and safe therapy for the prevention of PI in critically ill patients and may reduce length of stay in the ICU. Trial registration RBR-8nt9m4. Registered prospectively on July 20th, 2018, https://ensaiosclinicos.gov.br/rg/RBR-8nt9m4
Several experimental studies have shown that chemical modification of graphene oxide with n-alkylamines allow to control its interfacial activity in oil–water systems, altering its dispersibility and favoring the formation of emulsions. However, due to the complexity of its chemical structure and experimental limitations, the emulsification mechanism and interfacial properties have not been fully understood. In order to understand the behavior at the oil-water interface of alkylamine functionalized Graphene Oxide (GO) based materials, in this research we evaluated the interfacial activity of GO functionalized with different alkylamines (aGO) with different aliphatic chain lengths of 1, 3, 5, 7, 9 and 12 carbon atoms by Molecular Dynamics simulations. The dispersibility of the GO-based materials was analyzed and it was found that the Hydrophilic-Lipophilic Balance (HLB) of the GO can be controlled with the alkylamine chain length, making the GO more hydrophobic as the aliphatic chain length of the alkylamines becomes longer. Alkylamine chains bonded on the GO structure were capable to modifying the orientation relative to the Toluene/Water interface, going from parallel for the GO case to orthogonal for the aGO nanosheets, adopting a “head–tail” configuration due to the hydrophobic effect between the aliphatic chains and the Water molecules. Simulations also revealed that synergistic effect of aGO can decrease the interfacial tension of the Toluene-Water system as the aliphatic chain length and number of sheets increase obeying the Traube´s rule, indicating a behavior like molecular surfactant, where the IFT of the system decreases as the amount of surfactant increases.
Se trata de un paciente masculino con antecedente de artritis reumatoidea, síndrome de ojo seco y trasplante de córnea, hace 3 años. El paciente informa disminución de la agudeza visual en el ojo derecho. En el examen físico, se detecta una línea de rechazo en el meridiano a las 6 en la córnea e hiperemia conjuntival temporal. Un mes después refiere secreción excesiva y disminución de la agudeza visual (cuenta dedos a 3 metros). El examen reveló vascularización corneal de 360° y una perforación aséptica de la córnea central. La primera medida terapéutica fue cianoacrilato y lentes de contacto blandos, colirio de moxifloxacino al 0,5 % cada 4 horas, y colirio de hialuronato de sodio al 0,1 %. Quince días después no refirió mejoría, y su agudeza visual se redujo a cuenta dedos a 2 metros. Al examen, la neovascularización en cuatro cuadrantes y la prueba Seidel fueron positivas. Al día siguiente, se realizó un injerto conjuntival que mejoró el cuadro clínico; finalmente, se realizó un segundo trasplante tectónico de córnea. El abordaje terapéutico y quirúrgico de una perforación corneal depende del tamaño, forma, ubicación y causa de la lesión, siendo útiles los adhesivos tisulares de cianoacrilato en lesiones pequeñas.
Collagen bundle orientation (CBO) in myocardial infarct scars plays a major role in scar mechanics and complications after infarction. We aim to compare four histopathological methods for CBO measurement in myocardial scarring. Myocardial infarction was induced in 21 pigs by balloon coronary occlusion. Scar samples were obtained at 4 weeks, stained with Masson’s trichrome, Picrosirius red, and Hematoxylin–Eosin (H&E), and photographed using light, polarized light microscopy, and confocal microscopy, respectively. Masson’s trichrome images were also optimized to remove non-collagenous structures. Two observers measured CBO by means of a semi-automated, Fourier analysis protocol. Interrater reliability and comparability between techniques were studied by the intraclass correlation coefficient (ICC) and Bland–Altman (B&A) plots and limits of agreement. Fourier analysis showed an almost perfect interrater reliability for each technique (ICC ≥ 0.95, p < 0.001 in all cases). CBO showed more randomly oriented values in Masson’s trichrome and worse comparability with other techniques (ICC vs. Picrosirius red: 0.79 [0.47–0.91], p = 0.001; vs. H&E-confocal: 0.70 [0.26–0.88], p = 0.005). However, optimized Masson’s trichrome showed almost perfect agreement with Picrosirius red (ICC 0.84 [0.6–0.94], p < 0.001) and H&E-confocal (ICC 0.81 [0.54–0.92], p < 0.001), as well as these latter techniques between each other (ICC 0.84 [0.60–0.93], p < 0.001). In summary, a semi-automated, Fourier-based method can provide highly reproducible CBO measurements in four different histopathological techniques. Masson’s trichrome tends to provide more randomly oriented CBO index values, probably due to non-specific visualization of non-collagenous structures. However, optimization of Masson’s trichrome microphotographs to remove non-collagenous components provides an almost perfect comparability between this technique, Picrosirius red and H&E-confocal.
Composting is a promising process for green waste (GW) management. However, reducing the processing time and increasing end-product quality are aspects to be improved. A strategy to optimize GW composting is using bacterial strains and microbial consortia that stimulate lignocellulose degradation. This work systematically analyses the research trends on the use of those bacterial inoculants and microbial consortia. The information was analyzed according to three topics: (i) microbial role in the process; (ii) process optimization; and (iii) end-product quality. Research needs identified by our research include: (i) selection of bacterial consortia and optimization of inoculum concentration; (ii) correlation between enzymatic activity of indigenous and exogenous bacteria and nitrogen availability during the process; and (iii) stimulation of lignocellulose degradation and formation of humic substances considering end-product quality. This research contributes to planning future research endeavors related to the use of microbial inoculants to optimize GW composting. Graphical Abstract
Cetane number (CN) is one of the most important parameters affecting diesel fuel behavior. It is related to the time that elapses between fuel injection and beginning of combustion. To determine it, a combustion standardized test, under ASTM D613 regulation, needs to be carried out. As this process is limiting, since it requires a specific engine, CN can be approximated from the distillation temperatures of diesel fuels, providing another dimensionless parameter, named calculated cetane index (CCI). It also provides an approach to the explosion delay. ASTM D4737 standard is the regulation that allows its calculation. It is based on a four-term equation that may be applied to oil-derived products. Chemical composition of diesel fuel is composed exclusively of hydrocarbons of different nature. However, biodiesel is mainly composed of alkyl esters and, to a lesser extent, glycerides and glycerol impurities. This difference makes convenient to adapt the equation to biodiesel distillation curve. The aim of this work is to provide an alternative to CN calculation for biodiesel, based on CCI prediction. This manuscript presents distillation curves and density values of 14 different biodiesel types, from both animal and vegetable origin. This data, together with data from literature, have been used with non-linear equation modeling techniques. As a result, a modification of ASTM D4737 regulation with experimental data from biodiesel sources has been proposed. The proposed equation exhibits an error with respect to experimental data below 3.5% for most evaluated cases. Subsequently, it may be concluded that the proposed methodology may be applied to accurately calculate biodiesel CCI, as a substitute of CN.
Hydrogen is a bright energy vector that could be crucial to decarbonise and combat climate change. This energy evolution involves several sectors, including power backup systems, to supply priority facility loads during power outages. As buildings now integrate complex automation, domotics, and security systems, energy backup systems cause interest. A hydrogen-based backup system could supply loads in a multi-day blackout; however, the backup system should be sized appropriately to ensure the survival of essential loads and low cost. In this sense, this work proposes a sizing of fuel cell (FC) backup systems for low voltage (LV) buildings using the history of power outages. Historical data allows fitting a probability function to determine the appropriate survival of loads. The proposed sizing is applied to a university building with a photovoltaic generation system as a case study. Results show that the sizing of an FC-battery backup system for the installation is 7.6% cheaper than a battery-only system under a usual 330-minutes outage scenario. And 59.3% cheaper in the case of an unusual 48-hours outage scenario. It ensures a 99% probability of supplying essential load during power outages. It evidences the pertinence of an FC backup system to attend to outages of long-duration and the integration of batteries to support the abrupt load variations. This research is highlighted by using historical data from actual outages to define the survival of essential loads with total service probability. It also makes it possible to determine adequate survival for non-priority loads. The proposed sizing is generalisable and scalable for other buildings and allows quantifying the reliability of the backup system tending to the resilience of electrical systems.
The purpose of this study is to describe the efficacy of lateral supramalleolar flap as an option for soft tissue repair in open fractures of foot and ankle and to present the experience in 2 trauma units: Hospital Susana López de Valencia, Popayán Colombia, and Hospital Universitario de Santander, Bucaramanga Colombia. This is an observational, case series study including all patients with open fractures of foot and ankle who were treated from January 2016 to June 2021 and who required soft tissue coverage. Patients whose soft tissue injury was located on the anatomical area of the perforating peroneal artery, those with less than 6 months of follow-up and those who refused the proposed treatment were excluded. On the other hand, although literature reports flaps of up to 100 cm² (1), in our hands, this flap unsuitable for skin defects larger than 60 cm², and other procedures such as free flaps should be considered in these cases. Thirteen patients were selected, 9 men and 4 women, with a mean age of 30 years (12- 62 years) and mean follow-up duration of 10.3 months (6, 7, 8, 9, 10, 11, 12, 13, 14). In 11 patients, the mechanism of trauma involved a motorcycle accident. Mean flap size was 40 cm2 (30-48 cm²). Ten flaps survived with no acute problems, 2 presented with venous congestion and epidermolysis, which were treated conservatively, and 1 developed complete necrosis requiring reintervention. All interventions were performed by the authors belonging to the orthopedic trauma units from the involved hospitals. The lateral supramalleolar flap is an excellent alternative for the treatment of coverage defects caused by open foot and ankle fractures, producing satisfactory and predictable results in the hands of orthopedic surgeons with no specific training in microsurgical techniques. Level of clinical evidence: 4.
Bacteroides fragilis is one of the most common causative group of microorganisms that is associated with skin and soft tissue infections (SSTI). Metronidazole (MTZ) is the drug of choice used in the treatment of SSTI caused by the bacterium. However, owing to its physiochemical properties, MTZ have limited skin permeation, which render the drug unsuitable for the treatment of deep-rooted SSTIs. One strategy to overcome this limitation is to reformulate MTZ into nanosuspension which will then be loaded into dissolving microarray patches (MAPs) for the treatment of SSTIs caused by B. fragilis. Herein, we report for the first time on the preparation and optimisation of MAP loaded with MTZ nanosuspension (MTZ-NS). After screening a range of polymeric surfactants, we identified that Soluplus® resulted in the formation of MTZ-NS with the smallest particle size (115 nm) and a narrow PDI of 0.27. Next, the MTZ-NS was further optimised using a design of experiments (DoE) approach. The optimised MTZ-NS was then loaded into dissolving MAPs with varying MTZ-NS content. Furthermore, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) and cell proliferation assays along with LIVE/DEAD™ staining on the 3T3L1 cell line showed that the MTZ-NS loaded dissolving MAPs displayed minimal toxicity and acceptable biocompatibility. In vitro dermatokinetic studies showed that the MTZ-NS loaded MAPs were able to deliver the nitroimidazole antibiotic across all strata of the skin resulting in a delivery efficiency of 95 % after a 24-hour permeation study. Lastly, agar plating assay using bacterial cultures of B. fragilis demonstrated that MTZ-NS loaded MAP resulted in complete bacterial inhibition in the entire plate relative to the control group. Should this formulation be translated into clinical practice, this pharmaceutical approach may provide a minimally invasive strategy to treat SSTIs caused by B. fragilis.
Objective Novel foods and dietary practices, a lack of available land, and displacement by armed conflict have affected the ancestral food traditions practiced by the Inga community in Aponte, in Nariño, Colombia. These factors have led to problems with food security and malnutrition, which have impacted the growth and development of children. Therefore, this study is aimed at identifying the changes in ancestral food practices reported by Inga grandmothers, and the possibility of recuperating them in order to improve children’s health. Method A qualitative study was conducted that included 24 mothers with children under five years old and 25 grandmothers in nine Inga communities. Participants were recruited using snowball sampling. Free listing was used to identify changes in food patterns, and semi-structured interviews were conducted with 20 grandmothers to delve deeper into the subject. A translator of the Inga language facilitated communication, and the Inga researcher validated the translation using audio recordings. Each interview was transcribed and categorized for the purpose of analysis, using the NVivo 12 software. Results Free lists showed changes from a corn-based to a rice-based diet and a wide variety of non-ancestral food products. According to the grandmothers, “tiendas” have replaced traditional foods with those that are easy to prepare, which are attractive to mothers as well as to the children because of their flavor. Ancestral practices such as grinding, peeling, and log cooking are being abandoned. Government programs and daycare have incorporated new food that compete with traditional ones, with no clear evidence of an intercultural approach. Added to this is the dismissal by young mothers of the knowledge held by their grandmothers, which hinders the continuation of traditions. Conclusions The findings suggest that it is necessary to prevent the loss of the Inga food culture, and policies need to be created that promote and protect ancestral knowledge and that help to regain the value of the “chagra” farming system, with the support of elders, authorities who are recognized by the community, and government technicians, as recommended by the grandmothers who participated in this study.
The study of the reactivity of catalysts requires assessing chemical kinetics and mechanism in the absence of mass transport artifacts. Despite the existence of models and criteria for assessing the presence of mass transfer limitations during catalytic tests for gas-phase reactions in isothermal fixed bed reactors, the literature does not present straightforward protocols for performing the latter calculations. In this work, we present a systematic protocol for the calculations above. Particularly, the effectiveness factor for external and the Weisz-Prater number for the internal mass transfer limitations were developed. The oxidation of propane over mixed vanadium-aluminum (hydr)oxides was taken as a case study. Based on these protocols we perform a sensitivity study of the models. Results showed that the model for calculating the effectiveness factor was poorly sensitive to all the above modifications. Meanwhile, the Weisz-Prater number was much more sensitive to the studied modifications, even reaching deviations up to ~200%.
Monkeypox has been a global concern since May 2022 because cases have been reported from 19 non-endemic countries across three World Health Organization (WHO) regions [1]. The recent outbreak has sparked international concern, allowing for the dissemination of unregulated information through social media. Previous studies have highlighted the misinformation spread on Twitter (Twitter, Inc., San Francisco, CA) during recent public health emergencies, mainly Ebola, Yellow fever, and COVID-19 [2-6]. Therefore, we investigated the quality of monkeypox information on this social networking platform.
Experimental research has studied the emergence of fairness criteria such as merit and equality at increasingly younger ages. How much does the recognition and practice of these principles depend on the influence of central aspects of Western educated and industrialized societies? In an attempt to answer these questions, this article provides evidence regarding the choices of children in the Kogi indigenous community of the Sierra Nevada de Santa Marta, a traditional society living in the mountains of Northern Colombia that practices swidden agriculture, cattle-raising, and enjoys a special cultural status granted by the Colombian Constitution. Two groups of 6–7 and 10–11 year olds (N = 104) were tested on a modified dictator game and several scenarios from a resource distribution task including different fairness criteria. Our results point to the lack of focality of the idea of merit among Kogi children at these ages when deciding on third-party allocation tasks, even when the design prevented equal distribution.
Understanding the present-day crustal stress field is fundamental to comprehending active deformation in complex intraplate settings. This is especially true in the Colombian North Andean Block (C-NAB), where the Nazca, Caribbean, and South American plates interact. Our main goals of this study are: (1) to improve our understanding of seismotectonics of the C-NAB, (2) to test the hypothesis that slab geometry controls intraplate stresses, and (3) to evaluate the coherence between crustal stresses and strain field data obtained from GPS data. We show that south of the slab tear that separates the Nazca Plate from a northern plate (Caribbean Plate? Coiba Microplate?), a maximum horizontal compression (SHmax) trending N83°E is associated with a regional strike-slip faulting regime. In this region, the SHmax responds to the oblique subduction of the Nazca Plate, thus favoring the northeastern escape of the C-NAB. Oppositely, north of the slab tear, clockwise rotation in the SHmax to an NW–SE direction (N111°E) is associated with a regional thrust-faulting tectonic regime. Overall, the correspondence between SHmax and subducting slabs underscores relations between plate geometry, plate motion, and intraplate stresses. Finally, significant angular differences between the SHmax and horizontal shortening obtained from GPS displacements are important north of the slab tear and the western forearc region. We hypothesize that north of the slab tear, strain accumulation is enhanced due to the coupling between the upper plate and flat-slab subduction, causing clockwise rigid body rotation of the C-NAB.
Intermediate diaphragms (ID) in bridges with precast girders are intended to improve load distribution among girders. Despite this, their efficacy has been doubted recently due to the complex construction tasks needed to join them to the girders. Accordingly, this work aimed to determine the effect of the number of IDs on the distribution of vertical loads and girders response of a simply supported bridge. Four bridge layouts (0, 1, 2, and 3 IDs) were analyzed using 3D computational grillage models. The load distribution factors from the models were compared to those calculated using the Engesser-Courbon and Fauchart methods to determine the latter's accuracy in capturing the effect of the number of IDs. Moreover, the girders responses under the live loads in the current Colombian and Brazilian bridge design codes were assessed. The results show that the IDs have a more significant effect on the load distribution and deflection of interior girders than the exterior girders. Additionally, increasing the number of IDs reduced the maximum shear and torque while the bending moment and deflections remained nearly constant. Keywords Bridge, precast girders, intermediate diaphragms, live load, distribution factors, Engesser-Courbon, Fauchart, finite element method, grillage model. Graphical Abstract Theoretical and computational simulation of the effect of the number of intermediate diaphragms on the live load distribution factors and structural response of a precast girder bridge José Miguel Parra Benítez et al.
Chemical processes are usually catalytic transformations. The use of catalytic reagents can reduce the reaction temperature, decrease reagent-based waste, and enhance the selectivity of a reaction potentially avoiding unwanted side reactions leading to green technology. Chemical processes are also frequently based on multicomponent reactions (MCRs) that possess evident improvements over multistep processes. Both MCRs and catalysis tools are the most valuable principles of green chemistry. Among diverse MCRs, the three-component Strecker reaction (S-3-CR) is a particular transformation conducive to the formation of valuable bifunctional building blocks (α-amino nitriles) in organic synthesis, medicinal chemistry, drug research, and organic materials science. To be a practical synthetic tool, the S-3-CR must be achieved using alternative energy input systems, safe reaction media, and effective catalysts. These latter reagents are now deeply associated with nanoscience and nanocatalysis. Continuously developed, nanostructured silicate catalysts symbolize green pathways in our quest to attain sustainability. Studying and developing nanocatalyzed S-3-CR condensations as an important model will be suitable for achieving the current green mission. This critical review aims to highlight the advances in the development of nanostructured catalysts for technologically important Strecker-type reactions and to analyze this progress from the viewpoint of green and sustainable chemistry.
In this contribution, heterogeneous materials based on heteropolyacids (HPA, H 3 PW 12 0 40 hydrate) supported over several metal oxides (TiO 2 , SiO 2 , SBA-15, Al 2 O 3) were prepared using wetness impregnation, characterized by XRD, FTIR, SEM, acidity by TPD, nitrogen physisorption, RAMAN spectroscopy, 31 P NMR and then evaluated in the catalytic condensation of limonene with benzaldehyde. After incorporation of HPA over each support, no structural changes were observed as it was suggest by FTIR, RAMAN and XRD. Acidity analysis by TPD-NH 3 showed that increasing the HPA amount increases the acidity of the catalyst until it is constant (20-30%). HPA over alumina, silica and SBA-15 also showed high values of acidity but less than typical HPA/P25 catalyst (HPA over commercial Degussa P25). This last was one of the most selective materials (surface area of 39 m 2 /g and acidity of 187 µmol NH 3. g cat − 1) for the synthesis of 3-oxabyciclo[3.3.1]nonane (up to 80%) with a low selectivity to the limonene isomers by-products. The use of water as a solvent decreased considerably the catalytic activity. The same observation was found when the volume of the solvent increased to 30 mL. Besides, catalytic condensation can be performed at free solvent conditions and at room temperature; however, when decrease temperature, a higher number of isomers was observed rather than the desired product. In addition, catalytic condensation was also evaluated in biomass of essential oils and mixtures with sesquiterpenes showing good to excellent results. Typical LHHW mechanism was evident after kinetic analysis. HPA/P25 was shown to be a robust material since can be reused up to two times with a possible decrease in its catalytic activity.
Composting is an adequate method for treating and valorizing agricultural waste such as those from spring onion (SO) cultivation and chicken breeding (chicken manure–CM). However, the low content of Total Organic Carbon in the waste from SO and the high concentration of total nitrogen in CM are limitations for the composting process. This research studied the co-composting of SO and CM in a moorland ecosystem, together with locally available co-substrates such as biowaste (BW) and woodchips (WC), focusing on the effect of co-composting in process development and end-product quality. A pilot-scale experiment was carried out using three treatments in triplicated composting piles: (i) Treatment A: 43% CM + 41% BW + 16% WC; (ii) Treatment B: 52% CM + 32% SO + 16% WC, and (iii) Treatment C: 70% SO + 30% WC. Treatments A and B reached thermophilic temperatures after two days of the process start and remained at that level for 17 days. However, treatment B reached environmental temperature during curing in a shorter time (43 days) than treatment A (53 days). Treatment C did not achieve thermophilic temperatures. Tests carried out at the end of the process showed end-product stability and non-phytotoxic characteristics (germination indexes 80%). The fertility index of the products showed that treatments A and B presented values of 4.3 (over 5.0) while treatment C obtained a value of 2.5. From the perspective of agricultural use, products from the three treatments had limitations due to deficiencies in essential nutrients like phosphorus. Still, they had potential as a soil amendment for restoration processes. In summary, we have demonstrated that this waste, in combination with other organic materials, could be a good amendment for the composting process and the end product.
Human monkeypox (MPX) is a zoonotic viral disease caused by a member of the Orthopoxvirus genus, the monkeypox virus (MPXV). MPX has been reported primarily in endemic countries in Central and West Africa, with few imported cases to other regions.1 However, a rapidly emerging outbreak of monkeypox infection in over 20 non-endemic countries commenced in May 2022 and raised concerns because most patients had no travel history to endemic areas and were diagnosed through primary care and sexual health services and were mainly reported in men who have sex with men (MSM). Several men who developed monkeypox are living with HIV, but there are limited data on monkeypox and people living with HIV/AIDS (PLWHA). Previous studies in Africa found that people with uncontrolled HIV had worse outcomes, including more extensive and longer-lasting lesions, more complications, and several deaths.
Compressive covariance estimation has arisen as a class of techniques whose aim is to obtain second-order statistics of stochastic processes from compressive measurements. Recently, these methods have been used in various image processing and communications applications, including denoising, spectrum sensing, and compression. Notice that estimating the covariance matrix from compressive samples leads to ill-posed minimizations with severe performance loss at high compression rates. In this regard, a regularization term is typically aggregated to the cost function to consider prior information about a particular property of the covariance matrix. Hence, this paper proposes an algorithm based on the projected gradient method to recover low-rank or Toeplitz approximations of the covariance matrix from compressive measurements. The proposed algorithm divides the compressive measurements into data subsets projected onto different subspaces and accurately estimates the covariance matrix by solving a single optimization problem assuming that each data subset contains an approximation of the signal statistics. Furthermore, gradient filtering is included at every iteration of the proposed algorithm to minimize the estimation error. The error induced by the proposed splitting approach is analytically derived along with the convergence guarantees of the proposed method. The proposed algorithm estimates the covariance matrix of hyperspectral images from synthetic and real compressive samples. Extensive simulations show that the proposed algorithm can effectively recover the covariance matrix of hyperspectral images from compressive measurements with high compression ratios (8-15% approx) in noisy scenarios. Moreover, simulations and theoretical results show that the filtering step reduces the recovery error up to twice the number of eigenvectors. Finally, an optical implementation is proposed, and real measurements are used to validate the theoretical findings.
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5,816 members
Carlos Jaime Barrios Hernandez
  • High Performance and Scientific Computing Unit
Mayra Alejandra Machuca
  • School of Microbiology
Fabio Lora
  • Physics School
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Carrera 27, Calle 9, 68001000, Bucaramanga, Santander, Colombia
Head of institution
Prof. Hernán Porras Díaz
Website
www.uis.edu.co
Phone
57 7 6344000