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Forest fires intensify sediment transport and aggravate local and off-site consequences of soil erosion. This study evaluates the influence of post-fire measures on structural and functional sediment connectivity (SC) in five fire-affected Mediterranean catchments, which include 929 sub-catchments, by using the "aggregated index of connectivity" (AIC) at two temporal scenarios: I) immediately after the fire and before implementing post-fire practices ('Pre-man'), and II) two years after the fire ('Post-man'). The latter includes all the emergency stabilization practices, that are hillslope barriers, check-dams and afforestation. The stream system was set as the target of the computation (STR), to be representative of intense rainfall-runoff events with effective sediment delivery outside the catchments. Output normalization (AICN) allows comparing the results of the five basins between them. The sedimentological analysis is based on specific sediment yield (SSY) -measured at the check-dams installed after the fire -, and this data is used for output evaluation. Stream density and slope variables were the most influential factors on AICN-STR results at the sub-catchment scale. Post-fire hillslope treatments (barriers when built in high densities and afforestation) significantly reduced AICN-STR in comparison with untreated areas in both structural and functional approaches. Despite the presence of hillslope treatments, the higher erosive rainfall conditions resulted in higher AICN-STR values in the Post-man scenario (functional approach). A positive and good correlation was found between the measured SSY and the AICN-STR changes due to the post-fire practices and vegetation recovery, showing the good correspondence of the computation results and the real sediment dynamics of the studied catchments. Overall, AICN demonstrated to be a useful and versatile tool for post-fire management, which needs further research to optimize its applicability.
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Incendios , Ríos , Ecosistema , Bosques , Humanos , SueloRESUMEN
Knowledge of forest soil ecology is necessary to assess vulnerability to disturbances, such as wildfires, and improve its microbial diversity and functional value. Soil microbiota play an important role in forest soil processes and are a key driver of postfire recovery, but they are very vulnerable to heat. According to future scenarios for climate and land-use change, fire regimes will undergo transformations in semiarid terrestrial ecosystems, mainly in the Mediterranean Basin. To develop tools for forest management in fire-prone areas, i.e., fire prevention, we assessed the impact of prescribed burnings on soil microorganisms in Mediterranean mixed pine forests. We hypothesised that low severity fire burns would not influence the functional diversity of soil microorganisms, although the burning season could influence that response due to seasonal variations in its vulnerability. We used the Biolog EcoPlate System to record soil biological indicators and assess the effect of the prescribed burning season (early or late season) on bacterial communities, including the soil-plant interphase. The soil microbiome response differed significantly according to vegetation coverage but prescribed burning season was not directly related. Burning increased the proportions of soil organic matter and soil organic carbon, and also promoted cation-exchange capacity and total phosphorus, which were higher following spring burns. Microbial richness and the Shannon-Weaver diversity index both showed a positive correlation with vegetation cover. However, microbial richness was triggered after burning uncovered patches of vegetation. We also noted differences in the usage pattern for the six substrate groups defined in our study: the use of carboxylic acids, amino acids and carbohydrates was higher in unburned plots and those subject to late burns, whereas amino acids did not predominate in early burn plots.
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Incendios , Pinus , Carbono , Ecosistema , Bosques , Estaciones del Año , SueloRESUMEN
Zika virus (ZIKV) is an emerging mosquito-borne flavivirus transmitted mainly by Aedes species of mosquitos. Although the infection is usually mild and self-limiting, it is emerging as a public health challenge in tropical and subtropical countries owing to its unprecedented pathogenicity and increased risk for fetal malformations and neurological symptoms. Cutaneous manifestations as for other mosquito-borne viruses remain a hallmark of the disease. This article provides a detailed overview on ZIKV infection, including its varied cutaneous clinical manifestations and diagnostic aspects, and also provides detailed insights into its pathogenesis in human skin.
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Exantema/etiología , Enfermedades de la Piel/virología , Piel/patología , Infección por el Virus Zika/complicaciones , Virus Zika , Diagnóstico Diferencial , Fiebre/etiología , Humanos , Infección por el Virus Zika/patologíaRESUMEN
While there has been a keen interest in studying computation at the edge of chaos for dynamical systems undergoing a phase transition, this has come under question for cellular automata. We show that for continuously deformed cellular automata, there is an enhancement of computation capabilities as the system moves towards cellular automata with chaotic spatiotemporal behavior. The computation capabilities are followed by looking into the Shannon entropy rate and the excess entropy, which allow identifying the balance between unpredictability and complexity. Enhanced computation power shows an increase of excess entropy, while the system entropy density has a sudden jump to values near one. The analysis is extended to a system of non-linear locally coupled oscillators that have been reported to exhibit spatiotemporal diagrams similar to cellular automata.
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In the Mediterranean Basin, changes in climate and fire regime (increased recurrence and severity) reduce ecosystem services after wildfires by increasing soil degradation and losses in plant diversity. Our study was a biological approach to relate soil properties to vegetation recovery and burn severity. We focused our study on the natural recovery of the soil-plant interphase in Pinus halepensis Mill. forests located in the SE of Iberian Peninsula, a semiarid climate. We included some chemical properties 3 years after fire (available phosphorus (P) and soil organic carbon (Corg), among others), and biological soil indicators 3 and 5 years after fire (i.e. basal soil respiration (BSR), microbial biomass carbon (Cmic), carbon mineralization coefficient (Cmineral), metabolic quotient (qCO2) and microbial quotient (Cmic:Corg)). We analyzed the activity of three different enzymes: urease (UR), phosphatase (PHP) and ß-glucosidase (GLU). The changes in most chemical properties were ephemeral, but P and Corg showed higher values in burned areas, and the highest were found for low-moderate severity. Plant recovery was the triggering factor for the recovery of Corg and biological soil function. Burn severity and time after fire influenced Cmic and the Cmic:Corg, which were higher for moderate-high severity 3 years later, but were below the unburned values 5 years after fire. The microbial activities of GLU and UR were recovered in burned areas 5 years after fire. The PHP values lowered according to higher burn severity and time after fire. The soil ecological trends obtained by a principal component analysis revealed a relationship linking GLU, BSR and qCO2 that explained soil response to burn severity. PHP, Cmic and Cmic:Corg explained most of the variability related to time after fire. Our results provide insights into how burn severity, in Mediterranean fire-prone Aleppo pine stands, modulated the natural plant recovery linked to soil biochemical and microbiological response to fire. High burn severity limited natural vegetation recovery, and both reduced biological soil functionality. This knowledge can be implemented in post-fire planning to apply post-fire management (for mitigation and restoration) in which the "no intervention" tool should be contemplated. These findings provide information to be applied in adaptive forest management to improve the resilience of vulnerable ecosystems and to reduce burn severity in future fire events.
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Incendios , Pinus , Incendios Forestales , Ecosistema , Bosques , SueloRESUMEN
Prescribed fire removes or reduces the plant material that is prone to forest fires by creating fuel discontinuity and minimising fire intensity. This forest management tool potentially impacts Mediterranean ecosystems hydrological response by influencing water infiltration into soil. As direct measurements (e.g. by infiltrometers) of unsaturated infiltration in soil subjected to prescribed fires are scarce, this study has evaluated changes in soil hydraulic conductivity (SHC) using Minidisk infiltrometer after prescribed fires in representative plots of forests in the Iberian Peninsula under Mediterranean semi-arid conditions: (i) pure forest of Black pine Arnold ssp salzmannii; (ii) mixed forest of Maritime and Black pine; (iii) mixed forest of Aleppo and Maritime pine. The results have shown that fire reduced the organic layer thickness and its organic matter content. Consequently, after the prescribed fire the water content of burned plots was always lower than in untreated soils; conversely, the reverse soil behaviour was noticed before applying fire. Compared to the untreated soils, and with very few exceptions, prescribed fire did not cause significant changes in SHC. No general patterns in the comparisons between treatments (burned/unburned soils), in time evolution after fires and in the interactions between these effects were detected. This means that the SHC of burned soils followed the temporal variations of untreated soils. The lack of significance of these differences between treatments could be due to the low-fire severity and the limited effect of temperature in the mineral layer on soil hydraulic properties. This effect was expected and agrees with other studies. Overall prescribed fires did not alter SHC in Mediterranean forest ecosystems under unsaturated conditions since fire was of low-severity.
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Postfire restoration practices encompass those which aim to reduce negative wildfire impacts and to improve burned area rehabilitation. Contour-felled log debris (CFD) and log erosion barriers (LEB) are two techniques used worldwide on hillslopes after wildfires in order to avoid soil erosion. In this context, it is essential to evaluate how these restoration techniques can affect soil properties by increasing or decreasing wildfire impacts. The effects on several physico-chemical and biological soil parameters were here investigated by comparing three differently treated post-fire zones. Three randomly 20â¯×â¯20â¯m distributed plots were set up five years after wildfire in the burned and contour-felled log debris areas (CFD plots), three others in the burned and log erosion barriers area (LEB plots) and three others in the burned and unmanaged plots (BNa plots). Three more plots were set up in an unburned area close to the burned area (UB plots). The results revealed that LEB and, to a lesser extent CFD, improved postfire soil quality, which a priori favoured helped the recovery of ecosystem functions. Our results also indicate greater efficacy of LEB and CFD in retaining sediments by limiting loss of nutrients, which is considered essential to recover vegetation after a wildfire. Post-fire restoration plans should consider the use of LEB and CFD when aiming to favour ecosystem recovery processes after wildfires.
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Incendios , Incendios Forestales , Ecosistema , Bosques , SueloRESUMEN
A recently introduced model of coupled nonlinear oscillators in a ring is revisited in terms of its information processing capabilities. The use of Lempel-Ziv based entropic measures allows to study thoroughly the complex patterns appearing in the system for different values of the control parameters. Such behaviors, resembling cellular automata, have been characterized both spatially and temporally. Information distance is used to study the stability of the system to perturbations in the initial conditions and in the control parameters. The latter is not an issue in cellular automata theory, where the rules form a numerable set, contrary to the continuous nature of the parameter space in the system studied in this contribution. The variation in the density of the digits, as a function of time is also studied. Local transitions in the control parameter space are also discussed.
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INTRODUCTION: Admission to intensive care unit (ICU) is a difficult and stressful time for the patient, with the application of different techniques, such as intubation and ventilation support withdrawal or "weaning", which may fail due to anxiety. OBJECTIVES: To determine whether Reiki is useful in reducing weaning failure, as well as reducing the number of days of mechanical ventilation (MV), length of stay in ICU, amount of sedatives, amines, and antipsychotics. METHOD: Randomized clinical trial. SCOPE: ICU of a Level III University Hospital. POPULATION: ICU patients connected to Mechanical Ventilation for more than 48hours, with a signed informed consent. Patients in a terminal condition or potential organ donors were excluded. SAMPLE: 256 patients divided into two groups: intervention group (GI) and placebo (GP). The intervention involves the application of Reiki, and a simulated technique within the placebo group. An analysis was made of the absolute and relative frequencies, with a significance level of P<.05, 95% CI RESULTS: The percentage of failures at weaning was 9% in GI and 9.5% in GP (P=.42). The mean number of days on MV was 8.85 days for GI and 9.66 for the GP (P=.53). The mean dose of sedatives: GI 1078mg and 1491mg GP. The dose of Haloperidol was lower in the GI (5.30mg vs 16.81mg GP) (P=.03, 95% CI; -21.9 to -1.13). CONCLUSIONS: Reiki reduces the agitation of patients. A decrease was objectively observed in the number of days of Mechanical Ventilation, length of stay, lower doses of sedatives, and a slight decrease in the weaning failure in the GI. No statistically significant difference was found in the main variable.
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Tacto Terapéutico , Desconexión del Ventilador , Femenino , Humanos , Unidades de Cuidados Intensivos , Masculino , Persona de Mediana Edad , Resultado del TratamientoRESUMEN
The escalation of global warming, high temperatures, and wildfire frequency in dry ecosystems, including semi-arid landscapes, has resulted in increased wildfire regimes, compromising ecosystem resistance and resilience. To mitigate these risks, prescribed burning (PB) is being employed as a preventive measure to modify fuel loads in forest ecosystems. However, fire can also impact soil structure and microbiota, which play critical roles in nutrient cycling, biodiversity conservation, and overall ecosystem functioning. Therefore, understanding post-fire processes is essential for sustainable forest management. However, while previous studies have explored the effects of prescribed fire management on semi-arid soil properties in Mediterranean forest ecosystems, gaps remain in our understanding of its specific impact on the physical structure, chemical composition, and biological activities of soils. In this study, we conducted early spring PB in SE Spain in 2021 and assessed the ecological and temporal effects of PB on semi-arid soils. Soil respiration (SR) measurements using automatic CO2 flow chambers were employed to evaluate microbiota recovery. To examine impacts on soil structure we evaluated physicochemical characteristics, soil hydraulic conductivity (SHC), and soil water repellency (SWR). No significant differences were observed in any of the variables studied after one year. However, immediate effects were detected shortly after the PB. Our research specifically targeted soil structure and microbiota in a semi-arid landscape with poor soils, characterized by slower recovery and potentially fragile ecosystems. These results provide valuable insights for forest management practices, indicating that prescribed fire management strategies in similar ecosystems are unlikely to cause adverse effects on soil health. However, further research is warranted to explore the potential effects of prescribed fire intensity and seasonality. Future studies can focus on investigating these factors to provide more targeted recommendations for effective forest management strategies and wildfire prevention efforts.
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INTRODUCTION: Anterior glenohumeral dislocation in patients older than 60 years is related to rotator cuff lesion because of its pre-existing degenerative condition. However, in this age group, the scientific evidence fails to elucidate whether rotator cuff lesions are the cause or consequence of recurrent shoulder instability. The objective of this paper is to describe the prevalence of rotator cuff injuries in a series of consecutive shoulders in patients older than 60 years who suffered a first episode of traumatic glenohumeral dislocation, and its correlation with rotator cuff injuries in both shoulders. METHODS: Retrospectively, 35 patients over 60 years of age who had a first episode of unilateral traumatic anterior glenohumeral dislocation and who had MRI of both shoulders were studied, evaluating both shoulders with MRI to determine the structural damage correlation of the rotator cuff and long head of the biceps between them. RESULTS: When assessing the existence of partial or complete injury to the supraspinatus and infraspinatus tendons, the concordance on the affected and healthy sides, we have shown concordant results on both sides in 88.6 and 85.7%, respectively. The Kappa concordance coefficient was 0.72 for supraspinatus and infraspinatus tendons tear. Of the total of 35 cases evaluated, 8 (22.8%) presented at least some alteration in the tendon of the long head of the biceps on the affected side and only one (2.9%) on the healthy side, where the Kappa coefficient of concordance was 0.18. Of the 35 cases evaluated, 9 (25.7%) presented at least some retraction in the tendon of the subscapularis muscle on the affected side, while no participant showed signs of retraction in the tendon of this muscle on the healthy side. CONCLUSIONS: Our study has found a high correlation of the presence of a postero-superior rotator cuff injury after presenting a glenohumeral dislocation between the shoulder that has suffered the event and the presumably healthy contralateral shoulder. Nevertheless, we have not found this same correlation with subscapularis tendon injury and medial biceps dislocation.
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INTRODUCTION: Anterior glenohumeral dislocation in patients older than 60 years is related to rotator cuff lesion because of its pre-existing degenerative condition. However, in this age group, the scientific evidence fails to elucidate whether rotator cuff lesions are the cause or consequence of recurrent shoulder instability. The objective of this paper is to describe the prevalence of rotator cuff injuries in a series of consecutive shoulders in patients older than 60 years who suffered a first episode of traumatic glenohumeral dislocation, and its correlation with rotator cuff injuries in both shoulders. METHODS: Retrospectively, 35 patients over 60 years of age who had a first episode of unilateral traumatic anterior glenohumeral dislocation and who had MRI of both shoulders were studied, evaluating both shoulders with MRI to determine the structural damage correlation of the rotator cuff and long head of the biceps between them. RESULTS: When assessing the existence of partial or complete injury to the supraspinatus and infraspinatus tendons, the concordance on the affected and healthy sides, we have shown concordant results on both sides in 88.6 and 85.7%, respectively. The Kappa concordance coefficient was 0.72 for supraspinatus and infraspinatus tendons tear. Of the total of 35 cases evaluated, 8 (22.8%) presented at least some alteration in the tendon of the long head of the biceps on the affected side and only one (2.9%) on the healthy side, where the Kappa coefficient of concordance was 0.18. Of the 35 cases evaluated, 9 (25.7%) presented at least some retraction in the tendon of the subscapularis muscle on the affected side, while no participant showed signs of retraction in the tendon of this muscle on the healthy side. CONCLUSIONS: Our study has found a high correlation of the presence of a postero-superior rotator cuff injury after presenting a glenohumeral dislocation between the shoulder that has suffered the event and the presumably healthy contralateral shoulder. Nevertheless, we have not found this same correlation with subscapularis tendon injury and medial biceps dislocation.
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Coupled nonlinear oscillators are ubiquitous in dynamical studies. A wealth of behaviors have been found mostly for globally coupled systems. From a complexity perspective, less studied have been systems with local coupling, which is the subject of this contribution. The phase approximation is used, as weak coupling is assumed. In particular, the so-called needle region, in parameter space, for Adler-type oscillators with nearest neighbors coupling is carefully characterized. The reason for this emphasis is that, in the border of this region to the surrounding chaotic one, computation enhancement at the edge of chaos has been reported. The present study shows that different behaviors within the needle region can be found and a smooth change of dynamics could be identified. Entropic measures further emphasize the region's heterogeneous nature with interesting features, as seen in the spatiotemporal diagrams. The occurrence of wave-like patterns in the spatiotemporal diagrams points to nontrivial correlations in both dimensions. The wave patterns change as the control parameters change without exiting the needle region. Spatial correlation is only achieved locally at the onset of chaos, with different clusters of oscillators behaving coherently while disordered boundaries appear between them.
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OBJECTIVE: To determinate the adherence and barriers of our early mobilization protocol in patients who had received mechanical ventilation >48h in routine daily practice through clinical information system during all Intensive Care Unit (ICU) stay. DESIGN: Observational and prospective cohort study. SETTING: Polyvalent ICU over a three-year period (2017-2019). PATIENTS: Adult patients on mechanical ventilation >48h who met the inclusion criteria for the early mobilization protocol. INTERVENTIONS: None. MAIN VARIABLES OF INTEREST: Demographics, adherence to the protocol and putative hidden adherence, total number of mobilizations, barriers, artificial airway/ventilatory support at each mobilization level and adverse events. RESULTS: We analyzed 3269 stay-days from 388 patients with median age of 63 (51-72) years, median APACHE II 23 (18-29) and median ICU stay of 10.1 (6.2-16.5) days. Adherence to the protocol was 56.6% (1850 stay-days), but patients were mobilized in only 32.2% (1472) of all stay-days. The putative hidden adherence was 15.6% (509 stay-days) which would increase adherence to 72.2%. The most common reasons for not mobilizing patients were failure to meeting the criteria for clinical stability in 241 (42%) stay-days and unavailability of physiotherapists in 190 (33%) stay-days. Adverse events occurred in only 6 (0.4%) stay-days. CONCLUSIONS: Data form Clinical Information System showed although adherence was high, patients were mobilized in only one-third of all stay-days. Knowing the specific reason why patient were not mobilized in each stay-day allow to develop concrete decisions to increase the number of mobilizations.
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Ambulación Precoz , Unidades de Cuidados Intensivos , Adulto , Humanos , Persona de Mediana Edad , Anciano , Estudios Prospectivos , Ambulación Precoz/métodos , Tiempo de Internación , Sistemas de Información , Estudios Observacionales como AsuntoRESUMEN
Climate change has led to altered fire patterns in the Mediterranean basin due to rising temperatures and greenhouse gas emissions, diminishing the resilience of forest ecosystems. To address this threat, forest management increasingly employs preventive measures like controlled burns, aiming to mitigate wildfire damage. However, understanding the impact of prescribed burns on vegetation remains crucial. Our study focuses on assessing the ecological effects of early-season prescribed burns on Macrochloa tenacissima communities within Pinus halepensis Mill forests on the Iberian Peninsula. These forests, with southeast-facing slopes and arid soils, heavily rely on alpha grass for post-fire recovery, acting as a shield against runoff and erosion. Yet, the presence of highly flammable resprouting species can lead to rapid combustible material accumulation. We evaluated parameters like coverage, floral diversity (α-diversity), aboveground plant biomass, photosynthetic activity, and chemical leaf properties of alpha grass, a year after a low-intensity controlled burn. Comparing burnt and unburnt areas revealed significant changes in α-diversity and ecophysiology of Macrochloa tenacissima due to early-season prescribed burns. These short-term shifts underscore the need for further exploration of underlying mechanisms. Our analysis also showed distinct shifts in alpha grass leaf chemical composition between the two plot types, potentially impacting post-fire recovery strategies. Although prescribed burning might not be optimal for reducing fire risk in resprouting species-dominated forests, it conserves native plants and enhances ecosystem diversity, providing valuable ecological benefits. In conclusion, our research deepens our understanding of early-season burning's repercussions on flammable vegetation dynamics and combustible material availability in semi-arid landscapes. It contributes to standardized management protocols, aiding effective forest service administration and wildfire risk reduction.
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Incendios , Pinus , Incendios Forestales , Ecosistema , Poaceae , PlantasRESUMEN
Climate change worsening due to global warming and progressive abandonment in rural areas mean that wildfires are increasing in extent and severity terms, and are one of the major disturbances in the Mediterranean Basin. To mitigate these disturbances, preventive management tools need to be used. Fire employment is being implemented, known as prescribed burnings, as forestry actions to change vegetation lines both vertically and horizontally to eliminate forest fuel load continuity. This study aimed to know the ecological effects of late prescribed burning treatments under mixed trees. Prescribed burns were carried out in October 2019 in the municipality of Ayna, Albacete (SE Spain). To assess the short-term (12-month) fire impact on soil, we measured soil respiration with a CO2 flow chamber and analyzed soil physico-chemical properties. We also used minidisc infiltrometers to analyze soil repellency and soil hydraulic conductivity over a 1-year monitoring period. In addition, we evaluated the effects on tree strata by performing chemical nature analyses of fallen needles in Pinus pinaster after prescribed burning. According to our initial hypotheses, the results did not show significant changes in any parameter evaluated during the study period. However, some variables were affected in the first 3 months, needlefall and in microbiological activity, such as variations in soil physico-chemical properties, which can be due to long dry seasons combined with prescribed burning. This study attempts to observe and make known the effects that low-intensity prescribed burning has on soil and needlefall, which are relevant for updating forest management tools.
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Incendios , Pinus , Suelo/química , Bosques , Agricultura Forestal , ÁrbolesRESUMEN
Three-dimensional (3D) printing includes a group of technologies by means of which it is possible to generate three-dimensional objects from binary information. Orthopedics and traumatology are fields of medicine in which 3D planning has had the greatest impact, especially in trauma and oncological orthopedics. Applications of this technique include diagnosis, surgical planning, intraoperative guide creation, custom implants, surgical training, orthotic and prosthetic impression, and bioprinting. Advantages have been demonstrated in its use, such as greater technical precision, shorter surgical times, decreased blood loss and less exposure to X-rays. Although the process is increasingly optimized and accessible due to advances in software and automation, it is a technique that requires adequate training. The objective of this review is to offer an approach to this technology and its basic principles.
La impresión en tres dimensiones (3D) incluye un grupo de tecnologías por medio de las cuales es posible generar objetos tridimensionales a partir de información binaria. La ortopedia y traumatología es uno de los campos de la medicina en los que mayor impacto ha tenido la planificación 3D, en especial en trauma y ortopedia oncológica. Las aplicaciones de esta técnica incluyen el diagnóstico, planificación quirúrgica, creación de guías intraoperatorias, implantes personalizados, entrenamiento quirúrgico, impresión de ortesis y prótesis y la bioimpresión. Se han demostrado ventajas en su uso como la mayor precisión técnica, el acortamiento de tiempos quirúrgicos, disminución de pérdida sanguínea y menor exposición a rayos. Si bien el proceso está cada vez más optimizado y accesible por los avances en software y automatización, es una técnica que requiere un entrenamiento adecuado. El objetivo de esta revisión es ofrecer un acercamiento a esta tecnología y sus principios básicos.
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Procedimientos Ortopédicos , Ortopedia , Traumatología , Humanos , Impresión Tridimensional , Prótesis e ImplantesRESUMEN
The application of focused shockwaves and radial pressure waves in musculoskeletal pathology has had a great development in the last decade. Although most of the publications have highlighted their safety and efficacy, poor results and complications can occur. This review analyzes the main causes of its poor results, adverse effects, and complications, emphasizing their prevention.
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This paper reports in situ FTIR studies on the oxidation of formate at polycrystalline Pt in aqueous KOH. Data are presented which show that hydroxyl species play a major role in the electro-oxidation of small organic molecules under alkaline conditions at polycrystalline Pt, and that a number of possible mechanistic pathways are possible. Small changes in experimental conditions appear to be able to cause the reaction to flick between these pathways; for example, the presence of oxygen has a marked effect upon the observed electrochemistry. In contrast to acid solution, our postulated model includes the formation of intermediates bonded through O atoms, rather than C, as being an important option in alkaline solution. Finally, the pH distribution across the reflective electrode in external reflectance IR is modelled and significant variations in pH across the electrode surface in FTIR cells predicted and confirmed experimentally.
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This paper reviews work carried out over a number of years to try to elucidate the mechanism of oxygen reduction and methanol oxidation in alkaline solution. We have sought to achieve this by combining electrochemical, spectroscopic and solid-state chemical approaches, bringing together as wide a variety of techniques as possible both to shed light on the mechanisms and to point the way to more effective and efficient fuel cells. This work has become considerably more topical in recent years with the development of anion-exchange electrolyte membranes that can operate in alkaline environments, an important advance since it permits both the use of non-noble-metal catalysts and organic fuels at the anode, the latter precluded in aqueous alkaline electrolyte due to precipitation of inorganic carbonates at the electrode surface.