Soft Tissue Behavior During Limb Lengthening: An Experimental Study in Lambs

The effect of femoral elongation on skeletal muscle, nerves, and vessels was studied. Three groups of five lambs were used. After the intervention, the animals were killed at 2, 3, and 4 months. A left femoral elongation of 6 cm was practiced on all of them by means of callotasis, with a distraction rate of 0.5 mm every 12 hours. The femoral elongation process was evaluated by monthly x-ray films. The nucleic acid and protein levels in the muscular tissue were quantified at the level of the elongation focus and in the control extremity. The motor conduction velocity of the sciatic nerve was measured in both posterior limbs before the intervention and immediately before the lambs were killed. The arterial blood flow of both subsequent extremities was measured at the moment of death. A histological study of quadriceps muscle, sciatic nerves, artery, and subsequent femoral vein were examined histologically at the level of the elongation focus of both extremities. After elongation, no significant differences were observed in the muscle protein and nucleic acid levels with respect to the control extremity. No significant changes of the nerve conduction velocity were observed in any animal among the different groups. The arterial blood flow of the elongated extremity showed a progressive increase, reaching its maximum value 1 month after the distraction had terminated, with subsequent normalization. This increase of the blood flow was also observed in the control extremity, suggesting a possible systemic effect. The histological study revealed a comparative thickening of the endomysium and perimysium in the elongated muscle tissue, present at the end of the distraction and which was later normalized. No histological changes of the nerve stems undergoing distraction were observed either. During elongation, the arteries showed minimal histological changes. On the other hand, the veins showed areas of endothelial damage accompanied by thrombosis phenomena, especially at the end of the distraction period. The vascular morphology presented progressive normalization after the distraction phase

Testing the Flyby Anomaly with the GNSS Constellation

We propose the concept of a space mission to probe the so called flyby anomaly, an unexpected velocity change experienced by some deep-space probes using earth gravity assists. The key feature of this proposal is the use of GNSS systems to obtain an increased accuracy in the tracking of the approaching spacecraft, mainly near the perigee. Two low-cost options are also discussed to further test this anomaly: an add-on to an existing spacecraft and a dedicated mission.Comment: 8 pages, 1 figure, 4 table

Hemiepifisiodesis femoral distal mediante biomateriales reabsorbibles: Estudio experimental en el conejo

Se valoró experimentalmente un implante triangular compuesto de 3 tornillos metálicos unidos por un filamento de PDS II o Tendofil como método de epifisiodesis. Se utilizaron conejos esqueléticamente inmaduros, divididos en 4 Grupos, según el seguimiento postoperatorio (1,2,3 y 4 meses), subdivididos a su vez en 2 subgrupos según el filamento empleado. Se colocó el implante en la cara lateral de la epífisis femoral distal izquierda. La extremidad posterior derecha sirvió como control practicándose estudios radiológicos, histológicos e histomorfométrico. Las extremidades intervenidas presentaron una desviación en valgo significativa respecto a las control. El implante utilizado consiguió el frenado misario con ambos filamentos. Durante el primer mes, la eficacia del implante reabsorbible fue comparable al metálico. Posteriormente, el metálico resultó más eficaz. Los estudios histológicos e histomorfométrico mostraron un frenado asimétrico de la fisis intervenida. No hubo daños fisarios en relación con la degradación del implante reabsorbible. Nuestros resultados sugieron el diseño de implantes reabsorbibles en la cirugía del cartílago de crecimiento.A triangular implant compound by 3 metallic screws united by a filament (PDS II vs. Tendofil) as method of experimental epiphysiodesis was evaluated. They were used 32 immature rabbits, divided into 4 Groups acoording to the follow-up (1.2.3. and 4 months), and subdivided according to the employed filament. The implant was located at the lateral face of the distal left femoral epiphysis. The right extremity served as control. Radiographic, histologic and histomorphometric studies were performed. The operated legs presented a significant valgus deviation as compared to controls. The epiphysiodesis was achieved with both types of filaments. During the first month, the efficiency of the absorbable implant was comparable to the metallic. Thereafter, the metallic implant results more effective. Histologic and morphometric studies showed the hemiepiphysiodesis. No physeal damaged in relationship to the degradation of the absorbable implant was observed. Our results suggests the use of absorbable implant in growth plate surgery

The planetary nebula IC 4776 and its post-common-envelope binary central star

We present a detailed analysis of IC 4776, a planetary nebula displaying a morphology believed to be typical of central star binarity. The nebula is shown to comprise a compact hourglass-shaped central region and a pair of precessing jet-like structures. Time-resolved spectroscopy of its central star reveals periodic radial velocity variability consistent with a binary system. While the data are insufficient to accurately determine the parameters of the binary, the most likely solutions indicate that the secondary is probably a low-mass main sequence star. An empirical analysis of the chemical abundances in IC 4776 indicates that the common-envelope phase may have cut short the AGB evolution of the progenitor. Abundances calculated from recombination lines are found to be discrepant by a factor of approximately two relative to those calculated using collisionally excited lines, suggesting a possible correlation between low abundance discrepancy factors and intermediate-period post-common-envelope central stars and/or Wolf-Rayet central stars. The detection of a radial velocity variability associated with binarity in the central star of IC 4776 may be indicative of a significant population of (intermediate-period) post-common-envelope binary central stars which would be undetected by classic photometric monitoring techniques.Comment: Accepted for publication in MNRA

Asymmetric Sovereign Risk: Implications for Climate Change Preparation

Sovereign risk exhibits significantly asymmetric reactions to its determinants across the conditional distribution of credit spreads. This aspect, previously overlooked in the literature, carries relevant policy implications. Countries with elevated risk levels are disproportionately affected by climate change vulnerability compared to their lower-risk counterparts, especially in the short term. Factors such as inflation, natural resource rents, and the debt-to-GDP ratio exert different effects between low and high-risk spreads as well. Real growth and terms of trade have a stable but modest impact across the spread distribution. Notably, investing in climate change preparedness proves effective in mitigating vulnerability to climate change, in terms of sovereign risk, particularly for countries with low spreads and long-term debt (advanced economies), where readiness and vulnerability tend to counterbalance each other. However, for countries with high spreads and short-term debt, additional measures are essential as climate change readiness alone is insufficient to offset vulnerability effects in this case. Results also demonstrate that the actual occurrence of natural disasters is less influential than vulnerability to climate change in determining spreads

Sovereign Risk and Economic Complexity: Machine Learning Insights on Causality and Prediction

We investigate how a country’s economic complexity influences its sovereign yield spread with respect to the US. We analyze various maturities across 28 countries, consisting of 16 emerging and 12 advanced economies. Notably, a one-unit increase in the economic complexity index is associated to a reduction of about 87 basis points in the 10-year yield spread (p<0.01). However, this effect is largely non-significant for maturities under 3 years and, when significant (p<0.1), the reduction is around 54 bps. This suggests that economic complexity affects not only the level of the sovereign yield spreads but also the curve slope. Our first set of models utilizes Advanced causal machine learning tools, allowing us to control for a large set of potential confounders. This is crucial given our relatively small dataset of countries and roughly 15 years of data, as well as the low frequency of annual variables. In the second part of our analysis, we shift our focus to economic complexity’s predictive power. Our findings reveal that econòmic complexity is a robust predictor of sovereign spreads at 5-year and 10-year maturities, ranking among the top three predictors, alongside inflation and institutional factors like the rule of law. We also discuss the potential mechanisms through which economic complexity reduces sovereign risk and emphasize its role as a long-run determinant of productivity, output and income stability, and the likelihood of fiscal crises

Does economic complexity reduce the probability of a fiscal crisis?

Higher economic complexity of a country reduces the probability of suffering a fiscal crisis between 46% and 57%. Along with institutional factors, complexity is shown to be sufficient to describe the risk of facing episodes of fiscal distress. On the contrary, the role of variables frequently emphasized by the literature and policy markets, such as the debt-output ratio, real growth, inflation, terms of trade or fiscal balance, is very modest or insignificant. Development strategies that aim for greater economic complexity also promise to reduce countries’ fiscal vulnerabilit

Risk Spillovers between Global Corporations and Latin American Sovereigns: Global Factors Matter

We study volatility spillovers between the corporate sector’s and Latin American countries’ CDS. Daily data from October 14 2006 to August 23 2021 are employed. Spillovers are computed both for the raw data and for filtered series which factor out the effect of global common factors on the various CDS series. Results indicate that most spillovers occur within groups, i.e., within countries and within global corporations. However, considerable spillovers are also registered from LAC sovereigns to corporations and vice versa. Interesting differences are encountered between filtered and unfiltered data. Specifically, spillovers from countries to corporations are overestimated (in about 4.3 percentage points) and spillovers from corporations to sovereigns are underestimated (in about 5.8 percentage points) when unfiltered data is used. This result calls for a revision of results obtained from studies that do not consider the role of global common factors on system spillovers. Like in most related studies, spillovers show considerable time-variation, being larger during times of financial or economic distress. When looking at total system spillovers over time, those corresponding to unfiltered series are always larger than those corresponding to filtered series. The difference between the two time-series is largest in times of distress, indicating that global factors play a major role in times of crises. Similar conclusions are derived from network analysis

Characterization of suspension poly(vinyl chloride) resins and narrow polystyrene standards by size exclusion chromatography with multiple detectors: Online right angle laser-light scattering and differential viscometric detectors

This work reports the utilization of a multi-detector size chromatography for the characterization of poly(vinyl chloride) (PVC) resins prepared by suspension polymerization in the range of temperatures between 21 and 75 °C. The chromatography equipment offers the possibility of analyzing the samples in terms of their absolute molecular mass using a combination of three detectors (TriSEC): right angle light scattering (RALLS), a differential viscometer (DV) and refractive index (RI). The PVC resins were fully characterized concerning the molecular weight distribution (MWD), its dependence with intrinsic viscosity ([eta]) and molecular sizes (radius of gyration, Rg and hydrodynamic radius, Rh). Additionally, it is also presented the characterization of polystyrene narrow standards serving as reference polymers.http://www.sciencedirect.com/science/article/B6TWW-4HHGNVH-4/1/170871b80274a89470f2a790d3ed999

Estudio experimental en conejos de un nuevo vidrio bioactivo en la reconstrucción de defectos óseos

Objetivo: Se evaluó "in vivo" un vidrio bioactivo en la reparación de defectos óseos en animales esqueléticamente maduros e inmaduros. Material y Método: Se intervinieron 32 conejos machos de Nueva Zelanda divididos aleatoriamente en dos Grupos de 16: esqueléticamente maduros e inmaduros respectivamente. En todos ellos, se labró un defecto óseo en la cara lateral del cóndilo femoral. En la mitad de cada Grupo se relleno el defecto óseo con un implante de biovidrio. El resto sirvió como control. En los animales inmaduros, el defecto óseo resultó equivalente a una lesión fisaria tipo VI de Rang. El seguimiento fue de 4 meses. Se realizó un estudio radiográfico mensual, así como un estudio necrópsico, histológico e histomorfométrico de los especimenes. Resultados: Todos los animales finalizaron el estudio. No se observaron desviaciones axiales de las extremidades intervenidas en los animales inmaduros. El vidrio presentó una excelente osteointegración tanto en animales maduros como inmaduros, con evidencia de osteoconducción sobre su superficie, de forma simultánea a a su degradación y reabsorción, sin deformidades o ruturas. Las formación ósea inducida y reabsorción, sin deformidades o roturas. La formació ósea inducida por el vídrio fue la mayor en los niveles inmaduros respecto a los maduros. Los animales control presentaron una reparación del defecto óseo de menor calidad, con variaciones entre individuos. Conclusiones: El comportamiento "in vivo" el vidrio testado permite considerarlo como un material adecuado para la sustitución o reparación ósea, en el relleno de cavidades, la cobertura de superficie de implantes, y la vehiculización de sustancias. En cirugía del cartílago de crecimiento podría utilizarse como material de interposición tras la resección de puentes óseos fisarios.Objective: to evaluate the usefulness of a new bioactive glass in bone defect healing in rabbits. Material & Methods: 32 New Zeland rabbits were randomly distributed in two groups of 16: mature and immature respectively . In all of them, a bone defect was performed in the lateral surface of femoral distal epiphysis. A glass bioactive implant was placed in the bone defect of 8 animals in each group. The others served as control. In the immature rabbits, bone defect results as a Type VI physeal injury of Rang. Follow-up was 4 months. A standardised radiographic study was monthly performed, and after sacrifice, a histological and morphometric study on the femora was done. Results: All the animals survived the follow-up. No axial deviations of distal femoral growth were observed in immature rabbits. The tested glass showed an excellent osteointegration in all the animals, with osteoconduction evidence over its surface, accompanying degradation and resorption phenomena, but without deformities of break. Bone healing over the tested bioactive glass was higher in immature rabbitr than in mature animals. The control animals showed a poor bone defect healing, with variations among individuals. Conclusion: The in vivo behaviour of tested bioactive glasas suggests its use as possible bone substitute for cavities filling, implant surfaces, and as drugs vehicle. In growth plate surgery, it should be use as interposition material afeter physeal bone bridges resection