Seasonal variation in allelopathic effects of corn residue on corn and cress seedlings

Several reports have revealed that corn (Zea mays L.) yields are reduced in a continuous corn cropping. This decrease in yield had been associated frequently with phytotoxins released from crop residues during the process of decomposition and from living plants. The objectives of this study were (1) to investigate the seasonal variation in allelopathic effects of corn residues left after harvest on corn seedling growth under varying tillage practices (no-till, disc, and plow) and (2) to investigate how these allelopathic substances were released from the corn plant or corn residues;Soil samples from fields previously planted to corn and with corn residues left after harvest were bioassayed using corn seedling growth in the growth chamber. Also, soil samples from a previously planted corn field and with corn plants currently growing were collected every month from April to September, 1982, for corn bioassay. The soil samples collected monthly were from plots with different tillage practices. The results showed that soil with corn residues produced shorter plants and smaller root, shoot, and biomass weights than the control (fallow soil). The most pronounced effect was on root weight. The April, August, and September soil samples were inhibitory to corn growth, whereas June and July soil samples had stimulatory effects. The April soil sample from the no-till treatment was the most inhibitory and produced plants which were yellow. Since the inhibitory effect of August and September soil samples probably could not have come from chemicals released from decomposing corn residues, another study was conducted. The results revealed that allelopathic substances were being released by living corn plants through root exudation or rain-leached substances;Using XAD-4 resin to trap allelopathic substances, the monthly soil samples were each attached to a circulating mechanism with XAD-4 resin column. The extracts from the column were bioassayed using cress seed germination. Cress seed germination index, germination rate, onset of 1% germination, and maximum germination percentage were derived using the SAS nonlinear regression program and the Richards\u27 function. The results showed that germination index and germination rate were inhibited by the samples from the months of April, May, August, and September but were stimulated by June and July soil samples

Prediction of two-phase choked-flow through safety valves

Different models of two-phase choked flow through safety valves are applied in order to evaluate their capabilities of prediction in different thermal-hydraulic conditions. Experimental data available in the literature for two-phase fluid and subcooled liquid upstream the safety valve have been compared with the models predictions. Both flashing flows and non- flashing flows of liquid and incondensable gases have been considered. The present paper shows that for flashing flows good predictions are obtained by using the two-phase valve discharge coefficient defined by Lenzing and multiplying it by the critical flow rate in an ideal nozzle evaluated by either Omega Method or the Homogeneous Non-equilibrium Direct Integration. In case of non-flashing flows of water and air, Leung/Darby formulation of the two-phase valve discharge coefficient together with the Omega Method is more suitable to the prediction of flow rate

Classification of Epileptic Activity Through Temporal and Spatial Characterization of Intracranial Recordings

Focal epilepsy is a chronic condition characterized by hyper-activity and abnormal synchronization of a specific brain region. For pharmacoresistant patients, the surgical resection of the critical area is considered a valid clinical solution, therefore, an accurate localization is crucial to minimize neurological damage. In current clinical routine the characterization of the Epileptogenic Zone (EZ) is performed using invasive methods, such as Stereo-ElectroEncephaloGraphy (SEEG). Medical experts perform the tag of neural electrophysiological recordings by visually inspecting the acquired data, a highly time consuming and subjective procedure. Here we show the results of an automatic multi-modal classification method for the evaluation of critical areas in focal epileptic patients. The proposed method represents an attempt in the characterization of brain areas which integrates the anatomical information on neural tissue, inferred using Magnetic Resonance Imaging (MRI) in combination with spectral features extracted from SEEG recordings

Conversational Discourse across Spanish Proficiency Levels

Este artículo analiza conversaciones en español escritas por participantes pertenecientes a cinco niveles de competencia comunicativa, en base a la realización de actos comunicativos, problemas gramaticales y grado de precisión, formas lingüísticas utilizadas en la formulación de algunos actos y la incorporación de determinados mecanismos textuales. La producción de los tres tipos principales de actos tiende a reflejar un patrón evolutivo a través de los niveles de competencia. El uso de marcadores deícticos y lazos correferenciales está condicionado por la competencia lingüística. A través del conocimiento del discurso en L1, los estudiantes de español como L2 participan en conversaciones desde niveles básicos.The conversations written by participants across five different Spanish proficiency levels are analyzed with respect to the realization of communicative acts, grammatical problems and accuracy rates, language forms used in formulating particular acts, and the incorporation of particular textual devices. The production of the three major types of acts tends to follow a developmental pattern across proficiency levels. The use of deictic markers and coreferential links is affected by language competence. By relying on their knowledge of L1 discourse principles, L2 Spanish learners can participate in conversations from the beginning levels

A [SU(6)]4^4 FLAVOR MODEL WITHOUT MIRROR FERMIONS

We introduce a three family extension of the Pati-Salam model which is anomaly-free and contains in a single irreducible representation the known quarks and leptons without mirror fermions. Assuming that the breaking of the symmetry admits the implementation of the survival hypothesis, we calculate the mass scales using the renormalization group equation. Finally we show that the proton remains perturbatively stable.Comment: Z PHYS. C63, 339 (1994

EMOTIONAL ELEMENTS ON LEARNING STYLE PREFERENCE OF HIGH AND LOW PERFORMING JUNIOR MARINE TRANSPORTATION STUDENTS

ABSTRACT This study aimed to determine the learning style of the Marine Transportation students in a private Asian university in terms of emotional elements as to motivation, persistence, responsibility and structure; and to compare the learning styles of high and low performing Marine Transportation students. Descriptive type of research was utilized in the study. Results showed that high and low performing students strongly agree that they enjoy learning and they get a sense of accomplishment from achieving and they like to learn most of the time especially when the subject is interesting. The high performing students have significantly higher persistence in completing the things they begun as well as in enjoying working on several tasks simultaneously. Both groups of marine students strongly agree that they feel best when they do things they know they should do while high performing students have significantly higher responsibility on doing conventional things depends on the tasks and on how they feel about the circumstances compared to the low performing students. Marine students wanted to be instructed completely in order for them to perform the activities accurately with the help of other members of the group through teamwork

Análisis de errores en la resolución de un problema de valor inciial

El siguiente trabajo de investigación se centra en el análisis de errores cometidos por alumnos de un curso de Análisis Matemático III del Ciclo Básico de las carreras de Ingeniería de la Facultad de Ciencias Exactas, Ingeniería y Agrimensura (FCEIA) de la Universidad Nacional de Rosario (UNR), en la resolución de una ecuación diferencial ordinaria de primer orden con condición inicial (problema de valor inicial, PVI). Está enmarcado en el proyecto 1ING299 “El aprendizaje de las Ecuaciones Diferenciales como herramientas de modelización en la Matemática básica para las carreras de Ingeniería” dirigido por la Lic. Martha Fascella de la FCEIA – UNR

Studying functional networks in human brain through intracerebral spontaneous EEG

none6G.Arnulfo; A.Pigorini; M.Massimini; L.Nobili; A.Schenone; M.M. FatoArnulfo, Gabriele; Pigorini, A.; Massimini, M.; Nobili, L.; Schenone, Andrea; Fato, MARCO MASSIM