Associating liver partition and portal vein ligation for staged hepatectomy (ALPPS) induces a rapid and extensive increase in liver volume. The functional quality of this hypertrophic response has ...been called into question because ALPPS is associated with a substantial incidence of liver failure and high perioperative mortality. This multicenter study aimed to evaluate functional liver regeneration in contrast to volumetric liver regeneration in ALPPS, using technetium-99m hepatobiliary scintigraphy and computed tomography volumetry, respectively.
Patients who underwent ALPPS and hepatobiliary scintigraphy in 6 centers were included. Hepatobiliary scintigraphy data were analyzed centrally at the Academic Medical Center in Amsterdam according to established protocols. Increase in liver function as measured by hepatobiliary scintigraphy after stage 1 of ALPPS was compared with the increase in liver volume. In addition, we analyzed the impact of liver function and volume on postoperative outcomes including liver failure, morbidity, and mortality.
In 60 patients, future liver remnant volume increased by a median 78% (interquartile range 48–110) during a median 8 (interquartile range 6–14) days after stage 1, while function as measured by hepatobiliary scintigraphy increased by a median 29% (interquartile range 1–55) throughout 7 days (interquartile range 6–10) in the 27 patients with paired measurements. After stage 2 of ALPPS, liver failure occurred in 5/60 (8%) patients, severe complications in 24/60 (40%), and mortality occurred in 4/60 (7%).
In ALPPS, volumetry overestimates liver function as measured by hepatobiliary scintigraphy and may be responsible for the high rate of liver failure. Quantitative liver function tests are highly recommended to avoid post hepatectomy liver failure.
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When reading a scientific manuscript, it is common to notice a lack of a core idea throughout the work. This means that the manuscript is composed of different parts that have little relationship ...with each other, creating a true chimera (a mythological animal made up of parts of different animals).A research work must have a core idea, a backbone that supports and develops the project. This backbone provides coherence and cohesion to the entire scientific work and should be based on the research question. The research question is the beginning and the most important aspect of the study, and all other components should be structured around it
Background Associating liver partition and portal vein ligation for staged hepatectomy (ALPPS) allows the resection of colorectal liver metastases with curative intent which would otherwise be ...unresectable and only eligible for palliative systemic therapy. This study aimed to compare outcomes of ALPPS in patients with otherwise unresectable colorectal liver metastases with matched historic controls treated with palliative systemic treatment. Methods All patients with colorectal liver metastases from the international ALPPS registry were identified and analyzed. Survival data were compared according to the extent of disease. Otherwise unresectable ALPPS patients were defined by at least 2 of the following criteria: ≥6 metastasis, ≥2 future remnant liver metastasis, ≥6 involved segments excluding segment 1. These patients were matched with patients included in 2, phase 3, metastatic, colorectal cancer trials (CAIRO and CAIRO2) using propensity scoring in order to compare survival. Results Of 295 patients with colorectal liver metastases in the ALPPS registry, 70 patients had otherwise unresectable disease defined by the proposed criteria. Two-year overall survival was 49% and 72% for patients with ≥2 and <2 criteria, respectively ( P = .002). Median disease-free survival was 6 months compared to 12 months ( P < .001) in the ≥2 and <2 criteria groups, respectively. Median overall survival was comparable between ALPPS patients with ≥2 criteria and case-matched patients who received palliative treatment (24.0 vs 17.6 months, P = .088). Conclusion Early oncologic outcomes of patients with advanced liver metastases undergoing ALPPS were not superior to results of matched patients receiving systemic treatment with palliative intent. Careful patient selection is essential in order to improve outcomes.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
•A phase-field continuum theory for brittle fracture in elastic–plastic solids is formulated, and its computational implementation is presented.•The theory is based on a virtual-power formulation in ...which two additional and independent kinematical descriptors are introduced.•The present phase-field model is suitable to analyze plastic deformation during surface separation in cracks.•The numerical model employs a mixed finite-element method and a splitting scheme with sub-stepping for time integration.•A number of well-known linear and non-linear fracture mechanics problems are solved.
The formulation of a phase-field continuum theory for brittle fracture in elastic–plastic solids and its computational implementation are presented in this contribution. The theory is based on a virtual-power formulation in which two additional and independent kinematical descriptors are introduced, namely the phase-field and the accumulated plastic strain. Further, it incorporates irreversibility of both phase-field and plastic strain evolutions by introducing suitable constraints and by carefully heeding the influence of those constraints on the kinetics underlying microstructural changes associated with plasticity and fracture.
The numerical implementation employs the finite-element method for spatial discretization and a splitting scheme with sub-stepping for the time integration. To illustrate its potential utility, we apply the model to a number of well known linear, as well as non-linear, fracture mechanics problems.
The described phase-field model, coupled with plasticity, provides a feasible technique to analyzing crack initiation and the subsequent crack growth resistance only if the length scale parameter included in the phase-field model is finite and treated as a material parameter which should be properly characterized.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
This contribution presents a two-scale formulation devised to simulate failure in materials with heterogeneous micro-structure. The mechanical model accounts for the nucleation of cohesive cracks in ...the micro-scale domain. The evolution and propagation of cohesive micro-cracks can induce material instability at the macro-scale level. Then, a cohesive crack is nucleated in the macro-scale model which considers, in a homogenized sense, the constitutive response of the intricate failure mode taking place at the smaller length scale.
The two-scale semi-concurrent model is based on the concept of Representative Volume Element (RVE). It is developed following an axiomatic variational structure. Two hypotheses are introduced in order to build the foundations of the entire theory, namely: (i) a mechanism for transferring kinematical information from macro-to-micro scale along with the concept of “Kinematical Admissibility”, and (ii) a Multiscale Variational Principle of internal virtual power equivalence between the involved scales of analysis. The homogenization formulae for the generalized stresses, as well as the equilibrium equations at the micro-scale, are consequences of the variational statement of the problem.
The present multiscale technique is a generalization of a previous model proposed by the authors (Sánchez et al., 2013; Toro et al., 2014) and could be viewed as an application of a recent contribution (Blanco et al., 2014). The main novelty in this article lies on the fact that failure modes in the micro-structure involve a set of multiple cohesive cracks, connected or disconnected, with arbitrary orientation, conforming a complex tortuous failure path. Following the present multiscale modeling approach, the tortuosity effect is introduced as a kinematical concept and has a direct consequence in the homogenized mechanical response.
Numerical examples are presented showing the potentialities of the model to simulate complex and realistic fracture problems in heterogeneous materials. In order to validate the multiscale technique in a rigorous manner, comparisons with the so-called DNS (Direct Numerical Solution) approach are also presented.
•A two-scale semi-concurrent formulation for material failure, based on the RVE concept, is addressed.•Effective cohesive laws are derived from solutions of micro–scale heterogeneous mechanical problems.•The model accounts for a strong coupling between micro and macro cohesive cracks.•Microscopic crack tortuosity is introduced as a kinematical concept having consequences on the homogenized responses.•Using this formulation, a two–scale model for concrete fracture problems has been developed and tested.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Abstract Background In times of modern surgery, transplantation and percutaneous techniques, pyogenic liver abscess (PLA) has essentially become a problem of biliary or iatrogenic origin. In the ...current scenario, diagnostic approach, clinical behavior and therapeutic outcomes have not been profoundly studied. This study analyzes the clinical and microbiological features, diagnostic methods, therapeutic management and predictive factors for recurrence and mortality of first episodes of PLA. Methods A retrospective single-center study was conducted including 142 patients admitted to the Hospital Italiano de Buenos Aires, between 2005 and 2015 with first episodes of PLA. Results Prevailing identifiable causes were biliary diseases (47.9%) followed by non-biliary percutaneous procedures (NBIPLA, 15.5%). Seventeen patients (12%) were liver recipients. Eleven patients (7.8%) died and 18 patients (13.7%) had recurrence in the first year of follow up. The isolation of multiresistant organisms (p = 0.041) and a history of cholangitis (p < 0.001) were independent risk factors for recurrence. Mortality was associated with serum bilirubin >5 mg/dL (p = 0.022) and bilateral involvement (p = 0.014) in the multivariate analysis. Conclusion NBPLA and PLA after transplantation may be increasing among the population of PLA in referral centers. History of cholangitis is a strong predictor for recurrence. Mortality is associated to hiperbilirrubinemia and anatomical distribution of the lesions.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
This paper is focused on the analysis of the sensitivity of the thermomechanical response of a macroscopic elastic body to changes that occur at the microstructure. This problem is a key issue in ...material design.
The sensitivity analysis relies on an accurate determination of the effective properties of the heterogeneous material. These effective properties are determined by computational homogenization. And their sensitivities, with respect to the parameters defining the microstructure, are then computed.
For an efficient evaluation of the thermomechanical response, we propose to build response surfaces for the effective material properties. The surfaces are generated in an offline stage, by solving a series of homogenization problems at the microscale. In such a way, the fully online multiscale response analysis reduces to a standard problem at the macroscale. Thus, an important reduction in computational time is achieved, which is a crucial advantage for material design.
The capability of the proposed methodology is shown in light of its application to the design of a thermally-loaded structure with variable microstructure. Considerable improvements in the structural response are achieved.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
La producción hortícola en la provincia de La Pampa, se encuentra en constante desarrollo. Los canales de comercialización de circuito corto, como los bolsones de hortalizas de producción local y ...diversificada, representa una oportunidad. La zanahoria, como hortaliza pesada, complementa los bolsones, sin embargo, se encuentra poca información técnica del cultivo en la zona. En este trabajo se evaluó el rendimiento y la calidad de un cultivo de material híbrido bienal de Zanahoria (Daucus carota L.) denominado SANGRIA (TAKII) en la Región Semiárida Pampeana. El ensayo se realizó en la huerta demostrativa de la AER INTA General Acha, provincia de La Pampa. El diseño experimental fue en bloques completos al azar con cuatro repeticiones. La parcela experimental fue de 5 m2 y la unidad muestral de 0,25 m2. La siembra se realizó a chorrillo el día 8 de marzo de 2021, a una densidad de semillas de 5 kg.ha-1. El riego fue por goteo. Se incorporó materia orgánica al suelo en forma de estiércol vacuno compostado a razón de 3 kg.m-2. El control de malezas fue de manera manual y raleo fue cada 0,03 m. Se utilizaron dos fechas diferentes para la cosecha, la primera fue el 7/7/2021 (T1) y la segunda fecha fue un mes después el 6/8/2021 (T2). En ambos momentos se midieron las siguientes variables: número total de raíces por metro cuadrado, rendimiento total en kg.ha-1, rendimiento comercial en kg.ha-1, peso de raíces de descarte en kg.ha-1, peso, largo y diámetro individual de las raíces. Se halló un mayor rendimiento total para T2 que para T1. Sin embargo, el hecho de que para T2 halla un mayor porcentaje de descarte que para T1, produjo una merma en el rendimiento comercial de T2, careciendo de diferencias significativas en esta última variable para los dos momentos de cosecha. El descarte se dio principalmente por raíces bifurcadas y por raíces chicas (menor a 10 cm). Los rendimientos comerciales de 36300 kg ha-1 y 43600 kg ha-1 para T1 y T2 respectivamente, indican que la Región Semiárida Pampeana es idónea para el cultivo de zanahorias bienales sumada a la calidad de raíces logradas.
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