Las diferencias entre el pretérito perfecto simple y el imperfecto son uno de los temas más complejos de la lengua española, no sólo para el estudiante, sino para el profesor, puesto que sistematizar los casos y hacerlos fácilmente comprensibles al alumno es tarea difícil. Los profesores de lengua, cuyas investigaciones han dado lugar a una serie de teorías y de corrientes metodológicas y didácticas que permiten enfocar la enseñanza de una lengua extranjera de manera muy distinta a como se hacía tradicionalmente. Vamos a repasar muy brevemente cuáles son estas teorías.

En primer lugar es necesario señalar en qué consiste el aprendizaje de una segunda lengua:

"El aprendizaje de una segunda lengua (L2) es el

Cancer is one of the critical health concerns. Health authorities around the world have devoted great attention to cancer and cancer causing factors to achieve control against the increasing rate of cancer. Carcinogens are the most salient factors that are accused of causing a considerable rate of cancer cases. Scientists, in different fields of knowledge, keep warning people of the imminent attack of carcinogens which are surrounding people in the environment and may launch their attack at any moment. The present paper aims to investigate the linguistic construction of the imminent carcinogen attack in English and Arabic scientific discourse. Such an investigation contributes to enhancing the scientists’ awareness of the linguistic co

This study aimed to identify the employment of the social networking platform «Twitter» in the 2016 presidential campaign led by the Republican candidate, Donald Trump; and analyse his tweets through his personal account on «Twitter»  for the period from: 10/ 8/2016 to: 11/ 8/2016 which represents the last month of the election campaign.

The study belongs to the type of descriptive studies using the analytical method through an analysis index that includes sub-categories and other secondary categories. The research has adopted the ordinary unit of information material (tweet) as an analysis unit for this purpose.

            A spectrophotometric- reverse flow injection analysis (rFIA) method has been proposed for the   determination of Nitrazepam (NIT) in pure and pharmaceutical preparations. The method is based upon the coupling reaction of NIT with a new reagent O-Coumaric acid (OCA) in the presence of sodium periodate in an aqueous solution. The blue color product was measured at 632 nm. The variation (chemical and physical parameters) related with reverse flow system were estimated. The linearity was over the range 15 - 450 µg/mL of NIT with detection limits and limit of quantification of 3.425 and 11.417 µg mL^-1 NIT,respectively. The sample throughput of 28 samples

Many studies of the relationship between COVID-19 and different factors have been conducted since the beginning of the corona pandemic. The relationship between COVID-19 and different biomarkers including ABO blood groups, D-dimer, Ferritin and CRP, was examined. Six hundred (600) patients, were included in this trial among them, 324 (56%) females and the rest 276 (46%) were males. The frequencies of blood types A, B, AB, and O were 25.33, 38.00, 31.33, and 5.33%, respectively, in the case group. Association analysis between the ABO blood group and D-dimer, Ferritin and CRP of COVID-19 patients indicated that there was a statistically significant difference for Ferritin (P≤0.01), but no-significant differences for both D-dimer and CRP.

Polyethersulfone (PES) ultrafiltration membrane blending NaX zeolite crystals as a hydrophilic additive was examined for zinc (II) and lead ions Pb (II) removal from aqueous solutions. The effect of NaX zeolite content on the permeation flux and removal efficiency was studied. The results showed that adding zeolite to the polymer matrix enhanced the permeation flux. The permeation flux of all the zeolite/PES matrix membranes was higher than the pristine membrane. No significant improvement was observed in the removal of Zn (II) ions using all prepared membranes as the removal percentage did not raise above 29.2%. However, the removal percentage of Pb (II) ions was enhanced to 97% using a membrane containing 0.9%wt. zeolite. Also, it was

In this research, we tackled the idea of absence and what companies it of interpretations and human, textual, philosophical and explanatory concerns. We also tackled the features and drawing them and identifying and lighting them by Ali Abdunnabi Az-Zaidi and how he read them as an Iraqi who writes in order to express a social, intellectual, political and religious reality in some of its aspects. The idea of absence and what accompanies it of pain or heartbreak or human change was a rich subject for all the writers and authors in the Iraqi theatre, and Ali Abdunnabi Az-Zaidi was one of them and the closest and most affected by it, who deserves discussion, explanation and briefing. The research problem was looking for the nature of absenc

Background: Immediate implant placement in the maxillary anterior region was challenging, especially with the jumping gap and limited primary implant stability. Objective: To assess the autogenous dentin graft biomaterial's ability to improve the esthetic outcomes of an immediately inserted implant. Methods: Twenty patients with non-restorable retained roots in the maxillary non-molar region surrounded by natural sound teeth were included in this study after a complete clinical and radiological examination, including patient health and clinical fitness for the immediate dental implant procedure. A single dental implant was inserted for each patient, and the resulting jump distance was filled with the mineralized dentin graft and co

Abstract:

The study focused on the application of smart tourism as one of the applications of electronic commerce in the form of (B2C) to attract tourists to Saudi Arabia, where the tourism sector is one of the important sectors on which the Kingdom depends on the diversity of its economy.

The purpose of the research: With the issuance of tourist visas for the first time the study noted a deterioration in the case of Saudi tourist sites over the Internet, which do not live up to this great interest by the Saudi government for this sector, which became vital to them. The study tried to identify the reality of the Saudi tourist sites through the Internet in order to identify the sui

Background: Studying and investigating the transverse strength(Ts), impact strength(Is), hardness (Hr) and surface roughness(Ra) of conventional and modified autopolymerizing acrylic resin with different weight percentages of biopolymer kraftlignin, after curing in different water temperatures; 40°C and 80°C. Material and Methods: Standard acrylic specimens were fabricated according to ADA specification No.12 for transverse strength, ISO 179 was used for impact testing, Shore D for hardness and profilometerfor surface roughness. The material lignin first dispersed in the monomer, then the powder PMMA is immediately added. Ligninadded in different weight percentages. Then cured using pressure pot (Ivomet) in two temperatures;40°C a