This study examines correlations between COVID-19 infections and deaths in six countries across six continents (Afghanistan, Costa Rica, Colombia, Australia, Algeria, and Germany). Using a sigmoid dose–response model, we relate cumulative infections, (t), to cumulative deaths, D(t), treating deaths as a time-delayed response to the spread of infection through transmission networks. Both I(t) and D(t) follow modified sigmoidal equations, which we apply to N consecutive epidemic waves. Pearson (r) and Spearman (rs) correlation coefficients highlight strong correlations between the parameters of I(t) and D(t). We identify empirical laws linking infection parameters to death parameters, leading to a mortality equation D(t) expressed as a function of infection-related parameters. We also establish a novel expression for the epidemic fatality rate β_f . Cross-correlation analysis of infection and death spread rates ( V_I (t) and V_D (t) ) reveals an average time lag Δ t of 7–24 days across the six countries. The average fatality rate ⟨β (t)⟩ ranges from 0.16 to 3.92
The pronounced heterogeneity of high-Andean soils constitutes a critical constraint to the sustainable productivity of quinoa in southern Peru, where current yields (1.6 t ha−1) remain well below potential (>5 t ha−1). This study aimed to develop a spatially predictive model of a weighted soil quality index (SQIw), the edaphic supply of nitrogen (N), phosphorus (P) and potassium (K), and the agricultural gypsum requirement by integrating edaphoclimatic covariates through regression–kriging. A total of 198 quinoa-cultivated soil samples were analysed; a minimum data set (MDS) was defined using correlation and principal component analyses, and regression–kriging was applied to map SQIw and the variables of interest. The MDS comprised electrical conductivity (EC), organic matter (OM), available P, exchangeable Na, sand, clay, and effective cation exchange capacity (ECEC); exchangeable Na (Wi = 0.160) and available P (Wi = 0.158) received the largest weights in the SQIw. SQIw values ranged from 0.22 to 0.84 and supported a five-class soil quality taxonomy; spatial modelling revealed a dominance of moderate-quality soils across the territory (85.21% of the agricultural area, 13,461.19 ha). The model achieved R2 = 0.56, RMSE = 0.05, and MAE = 0.04 for SQIw. Most of the area (12,175.65 ha; 77%) exhibited an intermediate gypsum requirement (9.73–14.33 t ha−1). Nitrogen and phosphorus showed the greatest territorial limitations, whereas potassium was largely non-limiting (84.82–570.17 kg ha−1). These results indicate that sodicity and N–P deficiencies are the primary functional constraints; the generated maps enable prioritisation of gypsum amendments and targeted variable-rate fertilisation strategies to optimise the sustainability of quinoa production in the Altiplano.
La gestión del cronograma en proyectos de construcción, es una cuestión esencial para el éxito de un proyecto y refleja el nivel de eficiencia gerencial. Este trabajo identifica los factores críticos que conllevan a una deficiente gestión del cronograma, con la finalidad de plantear estrategias de mejora para el gerenciamiento eficiente. Se identificó 22 factores en base a la literatura y la entrevista a expertos para elaborar el cuestionario. Se llevaron a cabo encuestas de escala de valoración a los profesionales del rubro construcción en el Perú, para clasificar los factores identificados, empleando el modelo del índice de importancia relativa (RII). Se recogió 81 encuestas válidas. Los resultados muestran que los 10 primeros factores críticos que conllevan a la deficiente gestión del cronograma de construcción son: deficiente plan de gestión del cronograma, cooperación general de todas las áreas del proyecto, experiencia del gerente en proyectos de construcción, calidad del equipo de profesionales del proyecto, métodos de construcción deficientes, uso de tecnologías de información avanzada en el proceso de control, personal técnico especializado, gestión técnica del proyecto, conflicto entre los involucrados del proyecto, conocimiento del gerente de proyecto. En el ámbito de proyectos públicos los factores críticos se relacionan principalmente con la planificación, mientras que en el sector privado adquiere mayor importancia la coordinación de los involucrados. Se plantearon estrategias de mejora que pueden ser implementados por los gerentes, debido a que en estos profesionales recae la toma de decisiones.
Various tubers are cultivated in the Peruvian Andes. Olluco (Ullucus tuberosus) is consumed locally for its culinary qualities and nutritional value. In addition to its resistance to pests and extreme climatic conditions, this Andean tuber is an important source of starch. In this study, the extraction and characterization of the physical, chemical, technofunctional, and thermal properties of olluco starches from the Puka cheqche papalisa (PCP), Bela api chuqcha lisa (BACL), and Q’ello muro lisa (QML) varieties were conducted, with samples collected in 2024. Extraction yields ranged from 3.00 to 4.45%, viscosities from 6443.17 to 6892.77 cP, a high whiteness index from 90.43 to 93.52, water activity less than 0.55, and a heterogeneous particle size distribution. Amylose content ranged from 31.00 to 33.33%. FTIR analysis revealed similar functional groups and structural bonds across the varieties. For technofunctional properties, the QML variety exhibited greater water absorption, a higher solubility index, and greater swelling power. Pasting temperatures ranged from 68.70 to 71.10 °C, with low retrogradation. Thermal analysis showed good thermal stability from 104.46 to 268.42 °C, a low gelatinization temperature from 59.37 to 60.19 °C, and an enthalpy of up to 5.5757 J/g. Olluco starches have high potential for industrial applications, and their ease of cultivation makes them ideal for starch extraction.
Acid-generating mining waste and polymer waste are two of the most persistent environmental problems facing the mining and manufacturing sectors, respectively. We have investigated the co-recovery of these disparate waste streams for the production of unfired cementitious paving blocks. We established a statistically optimized formulation using response surface methodology (RSM) and a central composite design (CCD). We systematically evaluated three process variables: air-curing time (4-37 days), dosage of the waste mixture (5-68% by weight of dry solids: acid-generating mining waste, hydrated lime, and recycled polymer in a waste-to-polymer mass ratio of 1:1), and type of polymeric aggregate (recycled PET flakes versus granulated rubber). Compressive strength ranged from 4.5 to 42.1 MPa across the 40 experimental conditions. The resulting quadratic model was clearly significant (F = 186.31, p < 0.0001) with solid predictive parameters (R-2 = 0.9796; R(2)pred = 0.9627; adequate precision = 42.47). Desirability-based optimization, which limited air curing to industrially feasible timeframes (7-28 days) and maximized waste utilization within a 10-50% by weight, identified PET with 12.4 days of curing and a 50% by weight waste mixture as the optimal configuration, predicting a compressive strength of 37.3 MPa. This value exceeds the 32 MPa threshold for Type I heavy-traffic paving blocks; however, confirmatory tests yielded 34.09 +/- 1.08 MPa, indicating that production-scale use should include control of moisture content, compaction, and batch homogeneity. Scanning electron microscopy with energy-dispersive spectroscopy (SEM/EDS) and X-ray diffraction (XRD) demonstrated that PET inclusions promoted a denser and more continuous interfacial transition zone than shredded rubber, driven by physical entanglement and the pronounced microfilling effect of the fine waste particles.
