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This article examines the production of musical nostalgia in High School Musical: The Musical: The Series (2019–23), one of the first series created for Disney’s streaming platform. On one level, the series serves as a nostalgic extension of the High School Musical franchise in its setting and narrative construction, and a nostalgic continuation of the teen-musical genre in its idealised depiction of high-school life mediated through song. At the same time, this nostalgia is coupled with an emphasis on the show’s newness: the series transposes the original film to a new format—a self-referential, multi-episodic mockumentary—and occupies a different temporal world, in which nostalgia is technologically mediated and constructed as part of the diegesis. Focusing on music, as a primary sensory input for the evocation of nostalgia, this study explores how The Series capitalises upon this nostalgia/modernity dichotomy to structure its narrative and engender brand affinity. Drawing together textual analyses of audiovisual sequences and practitioner testimony from the show’s creatives, it demonstrates how The Series uses music to develop Disney’s brand, harnessing the technological and creative promise of the Company’s proprietary streaming service, whilst simultaneously employing nostalgic strategies to reaffirm the status quo in aspects of its narrative.

This article examines the website Vocabulous, an innovative resource that combines Classics and English literacy. The aim of Vocabulous is to improve students' English vocabulary knowledge and skills using Latin and Greek root patterns. For example, the root ‘scrip’ meaning ‘write’ can help students understand that ‘inscription’, ‘manuscript’ and ‘transcription’ are all related to writing. Students use these roots to work out the meaning of unfamiliar vocabulary, so that by the end of the programme, they have the skills they need to decipher new words on their own. As Alex Quigley notes, ‘over 90% of the vocabulary of academic texts in school has Latin and Greek origins and therefore teaching etymology has positive implications for learning and cracking the academic code of school’ (Quigley, 2018: 71). This article discusses the pedagogy behind the site, the selection of Latin and Greek roots, the design of the questions (based on vocabulary acquisition research) and the use of animated videos to engage students. The article concludes by outlining the current Vocabulous trial with 10–13-year-olds in 50 schools across the UK, combining teacher testimonies with ideas for practical application in the classroom1. Vocabulous is funded by The SHINE Trust and is part of a research trial led by Professor Arlene Holmes-Henderson and Christ Church, Oxford. It will be available for school subscriptions from September 2023.

Abstract During sleep, recent memories are replayed by the hippocampus, leading to their consolidation, with a higher priority given to salient experiences. To examine the role of replay in the selective strengthening of memories, we recorded large ensembles of hippocampal place cells while male rats ran repeated spatial trajectories on two linear tracks, differing in either their familiarity or number of laps run. We observed that during sleep, the rate of replay events for a given track increased proportionally with the number of spatial trajectories run by the animal. In contrast, the rate of sleep replay events decreased if the animal was more familiar with the track. Furthermore, we find that the cumulative number of awake replay events occurring during behavior, influenced by both the novelty and duration of an experience, predicts which memories are prioritized for sleep replay, providing a more parsimonious neural correlate for the selective strengthening of memories.

Niemann Pick diseases types A (NPDA) and C (NPDC) are lysosomal storage disorders (LSDs) leading to cognitive impairment, neurodegeneration, and early death. NPDA and NPDC have different genetic origins, being caused by mutations in the acid sphingomyelinase (ASM) or the cholesterol transport protein NPC1, respectively. However, they share a common pathological hallmark in the accumulation of lipids in the endolysosomal compartment. Here, we tested the hypothesis that polyphenols reduce lipid overload in NPD cells by enhancing the secretion of extracellular vesicles (ECVs). We show that among the polyphenols tested, the ellagic acid metabolites, urolithin A and B, were the safest and most efficient in increasing ECV secretion. They reduced levels of accumulating lipids and lysosomal size and permeabilization in cultured bone marrow-derived macrophages and neurons from ASMko and NPC1 mutant mice, which mimic NPDA and NPDC, respectively. Moreover, oral treatment with ellagic acid reduced lipid levels, ameliorated lysosomal alterations, and diminished microglia activation in the brain of NPD mice. These results support the therapeutic value of ECV secretion and polyphenols for NPDs, which may also help treat other LSDs characterized by intracellular lipid overload.

Niemann-Pick disease type A (NPD-A) is a lysosomal storage disorder characterized by neurodegeneration and early death. It is caused by loss-of-function mutations in the gene encoding for acid sphingomyelinase (ASM), which hydrolyzes sphingomyelin into ceramide. Here, we evaluated the safety of cerebellomedullary (CM) cistern injection of adeno-associated viral vector serotype 9 encoding human ASM (AAV9-hASM) in nonhuman primates (NHP). We also evaluated its therapeutic benefit in a mouse model of the disease (ASM-KO mice). We found that CM injection in NHP resulted in widespread transgene expression within brain and spinal cord cells without signs of toxicity. CM injection in the ASM-KO mouse model resulted in hASM expression in cerebrospinal fluid and in different brain areas without triggering an inflammatory response. In contrast, direct cerebellar injection of AAV9-hASM triggered immune response. We also identified a minimally effective therapeutic dose for CM injection of AAV9-hASM in mice. Two months after administration, the treatment prevented motor and memory impairment, sphingomyelin (SM) accumulation, lysosomal enlargement, and neuronal death in ASM-KO mice. ASM activity was also detected in plasma from AAV9-hASM CM-injected ASM-KO mice, along with reduced SM amount and decreased inflammation in the liver. Our results support CM injection for future AAV9-based clinical trials in NPD-A as well as other lysosomal storage brain disorders.

Replay, the sequential reactivation within a neuronal ensemble, is a central hippocampal mechanism postulated to drive memory processing. While both rate and place representations are used by hippocampal place cells to encode behavioral episodes, replay has been largely defined by only the latter – based on the fidelity of sequential activity across neighboring place fields. Here, we show that dorsal CA1 place cells in rats can modulate their firing rate between replay events of two different contexts. This experience-dependent phenomenon mirrors the same pattern of rate modulation observed during behavior and can be used independently from place information within replay sequences to discriminate between contexts. Our results reveal the existence of two complementary neural representations available for memory processes.

Background & Aims: The molecular mechanisms driving the progression from early-chronic liver disease (CLD) to cirrhosis and, finally, acute-on-chronic liver failure (ACLF) are largely unknown. Our aim was to develop a protein network-based approach to investigate molecular pathways driving progression from early-CLD to ACLF. Methods: Transcriptome analysis was performed on liver biopsies from patients at different liver disease stages, including fibrosis, compensated cirrhosis, decompensated cirrhosis and ACLF, and control healthy livers. We created 9 liver-specific disease-related protein-protein interaction networks capturing key pathophysiological processes potentially related to CLD. We used these networks as a framework and performed gene set-enrichment analysis (GSEA) to identify dynamic gene profiles of disease progression. Results: Principal component analyses revealed that samples clustered according to the disease stage. GSEA of the defined processes showed an upregulation of inflammation, fibrosis and apoptosis networks throughout disease progression. Interestingly, we did not find significant gene expression differences between compensated and decompensated cirrhosis, while ACLF showed acute expression changes in all the defined liver disease-related networks. The analyses of disease progression patterns identified ascending and descending expression profiles associated with ACLF onset. Functional analyses showed that ascending profiles were associated with inflammation, fibrosis, apoptosis, senescence and carcinogenesis networks, while descending profiles were mainly related to oxidative stress and genetic factors. We confirmed by qPCR the upregulation of genes of the ascending profile and validated our findings in an independent patient cohort. Conclusion: ACLF is characterized by a specific hepatic gene expression pattern related to inflammation, fibrosis, apoptosis, senescence and carcinogenesis. Moreover, the observed profile is significantly different from that of compensated and decompensated cirrhosis, supporting the hypothesis that ACLF should be considered a distinct entity. Lay summary: By using transjugular biopsies obtained from patients at different stages of chronic liver disease, we unveil the molecular pathogenic mechanisms implicated in the progression of chronic liver disease to cirrhosis and acute-on-chronic liver failure. The most relevant finding in this study is that patients with acute-on-chronic liver failure present a specific hepatic gene expression pattern distinct from that of patients at earlier disease stages. This gene expression pattern is mostly related to inflammation, fibrosis, angiogenesis, and senescence and apoptosis pathways in the liver.

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Maximum heart rate (MHR) is widely used in the prescription and monitoring of exercise intensity, and also as a criterion for the termination of sub-maximal aerobic fitness tests in clinical populations. Traditionally, MHR is predicted from an age-based formula, usually 220-age. These formulae, however, are prone to high predictive errors that potentially could lead to inaccurately prescribed or quantified training or inappropriate fitness test termination. In this paper, we used functional data analysis (FDA) to create a new method to predict MHR. It uses heart rate data gathered every 5 seconds during a low intensity, sub-maximal exercise test. FDA allows the use of all the information recorded by monitoring devices in the form of a function, reducing the amount of information needed to generalize a model, besides minimizing the curse of dimensionality. The functional data model created reduced the predictive error by more than 50% compared to current models within the literature. This new approach has important benefits to clinicians and practitioners when using MHR to test fitness or prescribe exercise.

Abstract Fatty-acid-binding proteins (FABPs) are small intracellular proteins that coordinate lipid-mediated processes by targeting metabolic and immune response pathways. The aim of the study was to investigate plasma FABPs levels and their relationship with clinical outcomes in cirrhosis. Plasma levels of L-FABP1(liver and kidney), I-FABP2(intestine), and A-FABP4(adipocyte and macrophages) were measured in 274 patients with decompensated cirrhosis. Hepatic gene expression of FABPs was assessed in liver biopsies from patients with decompensated cirrhosis and in liver cell types from mice with cirrhosis. Immunohistochemistry of A-FABP4 in human liver biopsy was also performed. Plasma levels of FABPs were increased in patients with decompensated cirrhosis compared to those of healthy subjects (L-FABP1: 25 (17–39) vs 10 (9–17) ng/mL p = 0.001, I-FABP2: 1.1 (0.5–2.1) vs 0.6 (0.4–1) ng/mL p = 0.04 and A-FABP4: 37 (20–68) vs 16 (11–33) ng/mL p = 0.002), respectively. Increased A-FABP4 levels were associated with complications of cirrhosis, acute-on-chronic liver failure and poor survival. Hepatic A-FABP4 gene expression was upregulated in decompensated cirrhosis. Macrophages were the main liver cell that over-expressed A-FABP4 in experimental cirrhosis and increased A-FABP4 was found in macrophages of human biopsies by immunohistochemistry. A-FABP4 levels are increased in decompensated cirrhosis and correlate with poor outcomes. Liver macrophages appear to be the main source of A-FABP4 in decompensated cirrhosis.

Liver disease resulting from heart failure (HF) has generally been referred as “cardiac hepatopathy”. One of its main forms is congestive hepatopathy (CH), which results from passive venous congestion in the setting of chronic right-sided HF. The current spectrum of CH differs from earlier reports with HF, due to ischemic cardiomyopathy and congenital heart disease having surpassed rheumatic valvular disease. The chronic passive congestion leads to sinusoidal hypertension, centrilobular fibrosis, and ultimately, cirrhosis (“cardiac cirrhosis”) and hepatocellular carcinoma after several decades of ongoing injury. Contrary to primary liver diseases, in CH, inflammation seems to play no role in the progression of liver fibrosis, bridging fibrosis occurs between central veins to produce a “reversed lobulation” pattern and the performance of non-invasive diagnostic tests of liver fibrosis is poor. Although the clinical picture and prognosis is usually dominated by the underlying heart condition, the improved long-term survival of cardiac patients due to advances in medical and surgical treatments are responsible for the increased number of liver complications in this setting. Eventually, liver disease could become as clinically relevant as cardiac disease and further complicate its management.

In liver transplant (LT) recipients, Pneumocystis jirovecii pneumonia (PJP) is most frequently reported before 1992 when immunosuppressive regimens were more intense. It is uncertain whether universal PJP prophylaxis is still applicable in the contemporary LT setting. We aimed to examine the incidence of PJP in LT recipients followed at our institution where routine prophylaxis has never been practiced and to define the prophylaxis strategies currently employed among LT units in Spain. All LT performed from 1990 to October 2019 were retrospectively reviewed and Spanish LT units were queried via email to specify their current prophylaxis strategy. During the study period, 662 LT procedures were carried out on 610 patients. Five cases of PJP were identified, with only one occurring within the first 6 months. The cumulative incidence and incidence rate were 0.82% and 0.99 cases per 1000 person transplant years. All LT units responded, the majority of which provide prophylaxis (80%). Duration of prophylaxis, however, varied significantly. The low incidence of PJP in our unprophylaxed cohort, with most cases occurring beyond the usual recommended period of prophylaxis, questions a one-size-fits-all approach to PJP prophylaxis. A significant heterogeneity in prophylaxis strategies exists among Spanish LT centres.

In patients with liver cirrhosis the contribution of inherited and acquired prothrombotic disorders in the development of non-malignant portal vein thrombosis (PVT) is inconclusive. The purpose of this retrospective study was to examine the prevalence of thrombophilia in this setting at our center from January 2012 to November 2019. Tests included gene mutational analysis for Factor V Leiden, prothrombin G20210A, JAK2 (V617F), Calreticulin (CARL), in addition to activated protein C resistance, antithrombin III, protein C and S levels, and antiphospholipid antibodies. We included 77 patients, six of whom (7.8%) had a thrombophilic disorder: antiphospholipid syndrome in four patients, prothrombin gene mutation in one and factor V Leiden mutation in one. This latter patient had also been diagnosed with polycythemia vera years before PVT development. Complete thrombosis of the main portal vein and re-thrombosis after stopping anticoagulation were more frequent in patients with thrombophilia, but the rates of recanalization under anticoagulant therapy were similar among groups. No other difference was accounted between groups. The low prevalence of acquired and inherited thrombophilia found in patients with cirrhosis and PVT support testing for these disorders on an individual basis and avoiding universal screening to reduce costs and unwarranted testing.

The effect of forests on flow and flood lamination decreases as the magnitude and intensity of torrential events and the watershed surface increase, thus resulting negligible when extreme events affect large catchments. However the effect of forests is advantageous in case of major events, which occur more often, and is particularly effective in soil erosion control. As a result, forests have been extensively used for watershed management and restoration, since they regulate water and sediments cycles, preventing the degradation of catchments.

The concept of liver fibrosis and cirrhosis being static and therefore irreversible is outdated. Indeed, both human and animal studies have shown that fibrogenesis is a dynamic and potentially reversible process that can be modulated either by stopping its progression and/or by promoting its resolution. Therefore, the study of the molecular mechanisms involved in the pathogenesis of liver fibrosis is critical for the development of future antifibrotic therapies. The fibrogenesis process, common to all forms of liver injury, is characterized by the increased deposition of extracellular matrix components (EMCs), including collagen, proteoglycans, and glycoproteins (laminin and fibronectin 2). These changes in the composition of the extracellular matrix components alter their interaction with cell adhesion molecules, influencing the modulation of cell functions (growth, migration, and gene expression). Hepatic stellate cells and Kupffer cells (liver macrophages) are the key fibrogenic effectors. The antifibrogenic mechanism starts with the activation of Ly6Chigh macrophages, which can differentiate into macrophages with antifibrogenic action. The research of biochemical changes affecting fibrosis irreversibility has identified lysyl oxidase-like 2 (LOXL2), an enzyme that promotes the network of collagen fibers of the extracellular matrix. LOXL2 inhibition can decrease cell numbers, proliferation, colony formations, and cell growth, and it can induce cell cycle arrest and increase apoptosis. The development of a new humanized IgG4 monoclonal antibody against LOXL2 could open the window of a new antifibrogenic treatment. The current therapeutic target in patients with liver cirrhosis should focus (after the eradication of the causal agent) on the development of new antifibrogenic drugs. The development of these drugs must meet three premises: Patient safety, in non-cirrhotic phases, down-staging or at least stabilization and slowing the progression to cirrhosis must be achieved; whereas in the cirrhotic stage, the objective should be to reduce fibrosis and portal pressure.

MCP-1 (monocyte chemoattractant protein-1) is a proinflammatory cytokine involved in chemotaxis of monocytes. In several diseases, such as acute coronary syndromes and heart failure, elevated MCP-1 levels have been associated with poor outcomes. Little is known about MCP-1 in cirrhosis.To investigate the relationship between MCP-1 and outcome in decompensated cirrhosis.Prospective study of 218 patients discharged from hospital after an admission for complications of cirrhosis. Urine and plasma levels of MCP-1 and other urine proinflammatroy biomarkers: osteopontin(OPN), trefoil-factor3 and liver-fatty-acid-binding protein were measured at admission. Urine non-inflammatory mediators cystatin-C, β2microglobulin and albumin were measured as control biomarkers. The relationship between these biomarkers and the 3-month hospital readmission, complications of cirrhosis, and mortality were assessed.69 patients(32%) had at least one readmission during the 3-month period of follow-up and 30 patients died(14%). Urine MCP-1 and OPN levels, were associated with 3-month probability of readmission (0.85 (0.27-2.1) and 2003 (705-4586) ug/g creat vs 0.47 (0.2-1.1) and 1188 (512-2958) ug/g creat, in patients with and without readmission, respectively; p

In this paper we present a heterogeneous collaborative sensor network for electrical management in the residential sector. Improving demand-side management is very important in distributed energy generation applications. Sensing and control are the foundations of the “Smart Grid” which is the future of large-scale energy management. The system presented in this paper has been developed on a self-sufficient solar house called “MagicBox” equipped with grid connection, PV generation, lead-acid batteries, controllable appliances and smart metering. Therefore, there is a large number of energy variables to be monitored that allow us to precisely manage the energy performance of the house by means of collaborative sensors. The experimental results, performed on a real house, demonstrate the feasibility of the proposed collaborative system to reduce the consumption of electrical power and to increase energy efficiency.

In this paper we describe a localization and local communication system which allows situated agents to communicate locally, obtaining at the same time both the range and the bearing of the emitter without the need of any centralized control or any external reference. The system relies on infrared communications with frequency modulation and is composed of two interconnected modules for data and power measurement. Thanks to the open hardware license under which it is released, the research community can easily replicate the system at a low cost and/or adapt it for applications in sensor networks and in robotics.

En este trabajo se presenta un modelo de programación por metas no lineal devariable binaria para planificar el aprovechamiento de una plantación productora demadera en Cuba, donde se tienen en cuenta tanto objetivos económicos comoecológicos. Se trata de no superar ciertos niveles de volumen extraído, limitar la edad delos rodales a los que se aplica tala rasa, conseguir un bosque lo más equilibrado posiblerespecto a grupos de edad, superar ciertos niveles del valor actualizado neto en cadaperiodo de la planificación así como un umbral global prefijado de captura de carbonopara toda la planificación. Estos objetivos se tratan de superar teniendo en cuenta,además de restricciones técnicas relativas a los tratamientos, restricciones espaciales deadyacencias que limitan la superficie contigua máxima a la que se aplica tala rasa. Elresultado es un problema sumamente complejo, para el que se ha recurrido al métodometaheurístico basado en Scatter Search SSPMO a la hora de tratar su resolución. Conobjeto de contrastar la potencialidad del modelo propuesto, lo hemos aplicado a unaplantación de Pinus Caribaea situada en la provincia cubana de Pinar del Río.

Biomarkers are potentially useful in assessment of outcomes in patients with cirrhosis, but information is very limited. Given the large number of biomarkers, adequate choice of which biomarker(s) to investigate first is important.Analysis of potential usefulness of a panel of urinary biomarkers in outcome assessment in cirrhosis.Fifty-five patients with acute decompensation of cirrhosis were studied: 39 had Acute Kidney Injury (AKI) (Prerenal 12, type-1 HRS (hepatorenal syndrome) 15 and Acute Tubular Necrosis (ATN) 12) and 16 acute decompensation without AKI. Thirty-four patients had Acute-on-chronic liver failure (ACLF). A panel of 12 urinary biomarkers was assessed, using a multiplex assay, for their relationship with ATN, ACLF and mortality.Biomarker with best accuracy for ATN diagnosis was NGAL (neutrophil-gelatinase associated lipocalin): 36 [26-125], 104 [58-208] and 1807 [494-3,716] μg/g creatinine in Prerenal-AKI, type-1 HRS and ATN, respectively; p

Objectives. To examine relationships between conventional MRI measures and the paced auditory serial addition test (PASAT) and symbol digit modalities test (SDMT). Methods. A systematic literature review was conducted. Included studies had ≥30 multiple sclerosis (MS) patients, administered the SDMT or PASAT, and measured T2LV or brain atrophy. Meta-analysis of MRI/information processing speed (IPS) correlations, analysis of MRI/IPS significance tests to account for reporting bias, and binomial testing to detect trends when comparing correlation strengths of SDMT versus PASAT and T2LV versus atrophy were conducted. Results. The 39 studies identified frequently reported only significant correlations, suggesting reporting bias. Direct meta-analysis was only feasible for correlations between SDMT and T2LV (r=-0.45, P

FUNDAMENTO: El envejecimiento constituye probablemente uno de los factores más importantes que contribuyen a la aparición de hemopatías primarias adquiridas (HPA), la mayoría de carácter crónico. El propósito de este trabajo ha sido el estudiar la tasa de incidencia (TI) de HPA en una población de 522.621 habitantes (V: 252.721; M: 269.900), con un crecimiento vegetativo negativo (-1,4/10(5) habitantes/año), considerando por separado dicha incidencia en la población menor y la mayor de 60 años. MÉTODOS: Durante el periodo enero-diciembre de 1994, se realizó una estimación de las tasas de consulta y las tasas de incidencia de HPA en los pacientes procedentes del área, considerando separadamente los menores y los mayores de 60 años. Las categorías diagnósticas aplicadas fueron: gammapatías monoclonales de significado indeterminado (GMSI), según criterios de Kyle; mieloma múltiple (MM) y leucemia linfática crónica (LLC) según criterios del Myeloma Task Force, linfoma no Hodgkin (LNH) y enfermedad de Hodgkin (EH) siguiendo la clasificación REAL, síndromes mielodisplásicos (SMD) y leucemia aguda (LA) según la clasificación FAB, síndromes mieloproliferativos crónicos (SMPC), según el PVSG. Para el cálculo de las tasas de incidencia se utilizaron los métodos epidemiológicos descriptivos. RESULTADOS: La mayor tasa de consultas hematológicas por sospecha de HPA procedía de los mayores de 60 años (p

The improvement of odometry systems in collective robotics remains an important challenge for several applications. Social odometry is an online social dynamics which confers the robots the possibility to learn from the others. Robots neither share any movement constraint nor access to centralized information. Each robot has an estimate of its own location and an associated confidence level that decreases with distance traveled. Social odometry guides a robot to its goal by imitating estimated locations, confidence levels and actual locations of its neighbors. This simple online social form of odometry is shown to produce a self-organized collective pattern which allows a group of robots to both increase the quality of individuals' estimates and efficiently improve their collective performance.

The improvement of odometry systems in collective robotics remains an important challenge for several applications. Social odometry is an online social dynamics which confers the robots the possibility to learn from the others. Robots neither share any movement constraint nor access to centralized information. Each robot has an estimate of its own location and an associated confidence level that decreases with distance traveled. Social odometry guides a robot to its goal by imitating estimated locations, confidence levels and actual locations of its neighbors. This simple online social form of odometry is shown to produce a self-organized collective pattern which allows a group of robots to both increase the quality of individuals' estimates and efficiently improve their collective performance.

RESUMEN En este trabajo se resuelve el problema de Programación por Metas cuando las metas adoptan una forma fraccional lineal. La principal dificultad de este problema viene dada porque en el modelo de programación matemática que se ha de resolver para buscar soluciones que satisfagan los niveles de aspiración, surgen restricciones no lineales. Cuando existen soluciones que satisfacen todos los niveles de aspiración, el problema resulta fácil de resolver a través de la resolución de un problema lineal asociado. En este trabajo proponemos algoritmos para resolver este problema cuando no tenemos asegurada la existencia de dichas soluciones. Este estudio será llevado a cabo teniendo en cuenta todos los distintos enfoques de resolución de un problema de Programación por Metas, estableciendo algoritmos de búsqueda de las soluciones bajo todos estos enfoques, así como un análisis de sensibilidad de los niveles de aspiración.ABSTRACT This work deals with the resolution of the goal programming problem with linear fractional criteria. The main difficulty of these problems is the non-linear constraints of the mathematical programming models that have to be solved. When there exist solutions satisfying all target values, the problem is easy to solve by solving a linear problem. So, in this paper we deal with those instances where there is no guarantee such solutions exist, and therefore we look for those points in the opportunity set closest to the target values. This study has been done taking into account all the different approaches available for solving a goal programming problem, creating solution-search algorithms based on these approaches, and performing a sensitivity analysis of the target values.

Los bosques cubanos sufrieron una explotación indiscriminada en el pasado. A pesar de los esfuerzos realizados con los planes de reforestación, y el establecimiento de plantaciones, la estructura por edades de estos bosques está muy desequilibrada, lo que dificulta un flujo estable de bienes y servicios. En este trabajo se presenta la evolución de un modelo de planificación forestal con criterios múltiples, aplicado a dos plantaciones de Pinus Caribaea situadas en la región de Pinar del Río, Cuba, con el objetivo de lograr una estructura equilibrada de edades al finalizar el horizonte de planificación y con ello garantizar una estabilidad en el flujo de bienes y servicios sujeto a restricciones de área, volumen y manejo en general. El modelo se apoya en la Programación por Metas (PM) y evoluciona de un modelo de PM lexicográficas Lineal a un modelo lexicográfico con metas Fraccionales para terminar en un modelo con variable binaria y cuya resolución se lleva a cabo a través de métodos metaheurísticos. En el presente trabajo trataremos de establecer la evolución en la modelización de los principales objetivos propuestos y los resultados obtenidos en cada uno de ellos y analizaremos las conclusiones derivadas de este proceso investigador.

Dentro de la programación matemática no lineal, el problema que se ha abordado más en términos teóricos y algorítmicos es el problema convexo. Cuando estamos ante una función fraccional, no tenemos convexidad, pero sí otras buenas propiedades que pueden hacer más o menos fácil la elaboración de algoritmos propios de resolución del problema. En este trabajo nos centramos en adaptar el Método de las Ponderaciones, uno de los métodos clásicos de resolución a priori del problema multiobjetivo convexo, al caso no convexo de objetivos fraccionales lineales. Dado que no tenemos convexidad ni concavidad de las funciones objetivo, y esta condición es básica para la aplicación de dicho método, estudiaremos este inconveniente con profundidad, estableciendo condiciones bajo las cuales resulta válido este método como generador de los conjuntos eficiente y débilmente eficiente de nuestro problema. Para ello se plantea la necesidad de un estudio detallado de los conceptos de pseudoconvexidad, cuasiconvexidad, invexidad, pseudoinvexidad, etc.. Ofreceremos además un contraejemplo que nos muestra que, si no se dan las condiciones que previamente estableceremos, el Método de las Ponderaciones no es válido para generar todo el conjunto débilmente eficiente de nuestro problema

La potencialidad de los Métodos Interactivos para la resolución de problemas de Programación Multiobjetivo es clara. La mayoría de estos métodos han sido específicamente creados para resolver problemas lineales o convexos, sin embargo, el problema de Programación Fraccional Lineal Multiobjetivo no es lineal ni convexo. Por ello nuestro propósito ha sido la revisión de las Técnicas Interactivas más importantes de la literatura para comprobar su posible adaptación al caso Fraccional Lineal y desarrollar aquellas cuya adaptación a este caso haya sido posible. Para llevar a cabo este objetivo, partiremos de una clasificación de las principales Técnicas Interactivas existentes, viendo cuáles de ellas pueden ser aplicadas o adaptadas al caso Fraccional Lineal y cuáles no. Para estas últimas veremos las razones que nos llevan a no haber creído conveniente su adaptación al caso que nos ocupa. Todos los resultados y algoritmos obtenidos han sido implementados por los autores en un programa informático, denominado PFLMO, que resuelve, bajo entorno Windows, el problema específico de Programación Fraccional Lineal Multiobjetivo.

En el presente trabajo se presenta una mejora en la técnica más representativa de resolución del problema de Programación Fraccional Lineal Multiobjetivo, bajo el enfoque de la generación del conjunto eficiente: El algoritmo de Kornbluth y Steuer (1981). Benson (1985) estableció un fallo existente en este algoritmo al calcular un parámetro de vital importancia en el mismo. Sin embargo, el método alternativo que propuso Benson no resulta operativo pues se basa en la resolución de problemas paramétricos no lineales. En este trabajo, proponemos un nuevo método de cálculo de dicho parámetro, concluyendo en la creación de un algoritmo operativo aplicable a problemas reales. El algoritmo de Kornbluth y Steuer, así modificado, ha sido implementado en un programa bajo entorno Windows, de fácil utilización en problemas reales, llamado PFLMO y que aquí presentamos con un ejemplo