Multivariate analysis of phytoplankton standing crop in western harbor of Alexandria [Egypt] during spring and summer

Quantitative collections of phytoplankton were performed in the western harbor during spring and summer 1989, which represent the extreme conditions of both temperature and salinity. Seventy four species were recorded, belonging to Bacillariophyceae [43], Dinophyceae [14], Chlorophyceae [10], Cyanophyceae [4], Euglenophyceae [2] and one Silicoflagellate. Although numerous species were encountered, yet very few of them formed the main bulk of the community; namely, Euglena acus, Cycotella meneghiniana, Nitzschia closterium in spring, and Prorocentrum micans, Gessnerium mochimaensis, Skeletonema costatum during summer. Also, all these species are considered as indicator of pollution with except Gessenerium sp. The average phytoplankton standing crop reached about 156 and 194 thousand units.l-1 during spring and summer, respectively. The outer part of the harbor [western sector] was more productive than the inner part [Eastern sector]. Statistical analysis dealing with the changes in community structure was concerned with univariate [diversity] and multivariate [graphical and prediction] treatments. The latter one was applied to phytoplankton community data in relation to the physicochemical parameters. Results indicated that the western harbor is mostly polluted as supported by a moderate average of diversity value of 1.44. The graphical multivariate correspondence analysis was more advantageous over both clustering and MDS plots in that it gives the natural grouping of the stations, beside evaluating the leading classes and environmental variables responsible for community change. Multiple regression analysis illustrated also excellent equations model for the phytoplankton in the western harbor during spring and summer which can be applied to predict the phytoplankton crop in the two seasons

Aplicación del modelo de regresión lineal múltiple paso a paso al problema de la estimación de la anchura mesiodistal de caninos y premolares no erupcionados / Model aplication of multiple linear regression step by step at problem of mesiodistal estimation of canines and premolar unerupted

La predicción de la anchura mesiodistal de caninos y premolares permanentes no erupcionados y durante el estado de desarrollo de la dentición mixta, es de suma importancia para diagnosticar a pacientes que tienen pequeño o insuficiente espacio en los maxilares. Dicho problema ha sido tratado por muchos autores . En este sentido se han venido desarrollando modelos de regresión lineal cada vez más refinados, gracias a los extraordinarios avances alcanzados en el campo de la computación. Con miras a desarrollar ecuaciones de regresión que sirvan de instrumento de pronóstico para el caso venesolano se propone una aplicación del modelo de regresión lineal múltiple paso a paso