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We aimed to examine the effects of Ramadan fasting (RF) and high-intensity short-term maximal performance on elite soccer players' shooting accuracy, executive function (EF), and perceptions. Sixteen Muslim elite players fasting during Ramadan underwent assessments before (BR), during (DR), and after Ramadan (AR). Soccer-specific technical performance was evaluated using the Loughborough Soccer Shooting Test (LSST) before and after a 5-metre shuttle run test (5mSRT), conducted at the same time-of-day (17:00 h). Performance metrics recorded included higher distance (HD), total distance (TD), and fatigue index (FI). RPE after a 5-min warm-up and each repetition of the 5mSRT were obtained, and the mean RPE score was calculated. Trail Making Test (TMT Parts A and B) were used after the warm-up and the 5mSRT. Perceived difficulty (PD) was assessed following the LSST. HD, TD, and FI were not affected by RF (p > 0.05). DR, RPE and accuracy scores in the LSST were significantly lower after the 5mSRT compared to BR (1.29 vs. 1.24 AU; 1.29 vs. 1.24, respectively). In conclusion, RF had no adverse effects on physical performance. However, when combined with high-intensity running sessions, RF may impact accuracy and PD, and these adverse effects seem to have been translated into EF.
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Desempenho Atlético , Cognição , Jejum , Islamismo , Percepção , Futebol , Humanos , Futebol/fisiologia , Futebol/psicologia , Jejum/fisiologia , Desempenho Atlético/fisiologia , Desempenho Atlético/psicologia , Adulto Jovem , Cognição/fisiologia , Masculino , Percepção/fisiologia , Função Executiva/fisiologia , Adulto , Fadiga , Esforço Físico/fisiologiaRESUMO
Studies on students' perceptions and expectations during physical education (PE) online learning remain scarce. Centered on self-determination theory, the present cross-sectional study aims to identify gender differences and predictors affecting motivation, psychological needs satisfaction (PNS), and academic achievement during PE online learning. Data were collected from Saudi students' (N = 308, 161 females and 147 males) responses to the PE autonomy, relatedness, competence, and motivation questionnaires. Welch's t-test for unequal sample sizes, multiple linear regression, and binary logistic regression were used to compare means and to predict the relationships between the independent and dependent variables. The results showed higher autonomy and competence perceptions in female than in male students, but no differences were observed in relatedness. Female students presented higher intrinsic motivations, lower amotivation perceptions than males. However, no gender differences were recorded in extrinsic motivation. Students with less experience in online learning and weak grade point averages (GPAs) are more susceptible to having a high level of amotivation. Gender, GPA, and prior experience with online learning are the common predictors for all PNS and amotivation, while GPA and prior experience with online learning are the determinants of intrinsic motivation. GPA is affected by prior experience with online learning, autonomy, competence, intrinsic motivation, and amotivation. Therefore, teachers are encouraged to adapt their didactic-pedagogical behaviors during PE online learning according to students' motivation and autonomy perceptions. Structuring teaching activities with more individualized support for autonomy, competence, intrinsic motivation, and students' online skills/competencies ensures better learning efficiency and academic achievements.
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Sucesso Acadêmico , Educação a Distância , Humanos , Masculino , Feminino , Motivação , Educação Física e Treinamento , Fatores Sexuais , Estudos Transversais , Arábia Saudita , Estudantes/psicologia , Satisfação Pessoal , Autonomia PessoalRESUMO
Optimizing fine motor coordination and cognitive abilities in middle childhood through new intervention programs remains one of the most essential orientations in motor development and skills proficiency. The present study aims to identify the effect of a structure-based program intervention, combining motor accuracy exercises with visual art activities (ceramics, pottery, and creations using raw materials), on fine motor coordination, selective attention, and reaction time in middle childhood. Sixty, right-handed typically developed male schoolchildren (age = 8.29 ± 0.74 years; body height = 130.25 ± 0.05 cm and body mass = 29.83 ± 4.68 kg; mean ± SD) volunteered to participate in the study. They were randomly assigned to a combined group intervention (MG) receiving a mixed program integrating visual art activities and motor accuracy exercises; an accuracy group intervention (AG) receiving oriented motor accuracy exercises; and a control group (CG). Selective attention, reaction time, and fine motor coordination skills (accuracy: darts throw; manual dexterity: grooved pegboard test) were measured. Repeated measure ANOVA, one-way ANOVA, and Kruskal-Wallis ANOVA were performed for analysis. The results showed higher changes in MG compared to AG in manual dexterity (p < 0.001), in motor accuracy (p < 0.001), and in reaction time (p < 0.01), but not in selective attention (p = 0.379). In addition, higher changes were recorded in AG compared to CG in motor accuracy (p < 0.05), reaction time (p < 0.05), and in selective attention (p < 0.01), but not in manual dexterity (p = 0.082). The structured combined program best assists accuracy, manual dexterity, reaction time, and selective attention. Therefore, instructors in sports academies and teachers at schools are advised to use the combined program in the training sessions and in the non-curricular activities, respectively, to improve fine motor coordination, selective attention, and reaction time in middle childhood.
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The interest in the efficiency of online learning was and remains a major concern to researchers especially during the worldwide pandemic crisis (COVID-19). Nonetheless, there is a lack of studies focusing on students' perceptions in online physical education (PE) learning sessions. Based on the self-determination theory (SDT), the present investigation aimed to explore psychological need satisfaction (PNS) to understand the autonomy, competence, and relatedness of Saudi PE students during the online sessions undertaken during the COVID-19 pandemic lockdown. PE students (N = 321, 161 females and 160 males) completed an online questionnaire composed of demographic characteristics, grade point average (GPA), sleep and physical activity (PA) habits, and the physical education autonomy relatedness competence scales (PE-ARCS). A t-test and one-way ANOVA were conducted and revealed that female students presented higher PNS compared with males. Students practicing PA had higher autonomy values than those not practicing PA (p = 0.001). However, no differences were recorded concerning competence and relatedness perceptions. The groups practicing walking, aerobic exercise, muscular training, and specialty training had higher values in autonomy and relatedness. The groups that slept for more than six hours a night, had previous experience with online learning, and had a GPA of more than three recorded higher PNS values. Correlation analysis showed high interdependence of the three PNS variables as well as with the variables of gender, experience with online learning, sleep hours, and type of PA practiced, but not with GPA or frequency of PA practice. The PNS values regarding online PE sessions were (i) higher in female students compared with males and (ii) related to previous experience in online learning, GPA, sleep habits, and type of PA. Walking, aerobic exercise, muscular training, and training in a specialty affected both autonomy and competence perception; however, relatedness was mainly affected by walking activity. Therefore, it is necessary to support ICT knowledge of students with low GPAs and to encourage them to adopt balanced sleep and physical activity habits to increase their perceptions of autonomy, competence, and relatedness in online PE lessons.
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COVID-19 , Educação a Distância , Masculino , Humanos , Feminino , Educação Física e Treinamento , COVID-19/epidemiologia , Pandemias , Arábia Saudita/epidemiologia , Controle de Doenças Transmissíveis , EstudantesRESUMO
Introduction: hemostasis hysterectomy is the radical treatment for postpartum hemorrhage. The purpose of this study is to identify risk factors, indications and complications of hemostasis hysterectomy and to determine factors influencing the types of approaches to hysterectomy. Methods: we conducted a monocentric descriptive and analytical retrospective study in the Department of Obstetrics and Gynecology at the Regional Hospital of Ben Arous from 2003 to 2019. Patients were classified according to the type of surgical treatment they received: total or subtotal hysterectomy. Results: seventy patients were included in the study. The rate of hemostasis hysterectomy was 1.3%. The average age of patients was 34.5 years (±5.1). Indications for hemostasis hysterectomy were dominated by placenta accreta (39% of cases; n=27), uterine inertia (34% of cases; n=24) and uterine rupture (16% of cases; n=11). Perioperative morbidity rate was 34 % (n=24). The most frequent complications were hemorrhagic shock (17%; n=12), disseminated intravascular coagulation (6%; n=4) and bladder lesions (6%; n=4). We reported six cases of maternal death, reflecting a rate of 8% (n=6). Subtotal hysterectomy was performed in 79% of patients (n=55) and 21% of women (n=15) underwent total hysterectomy. Placenta accreta was significantly associated with total hysterectomy group (aOR: 6.93, 95% CI: 1.07-44,80, p=0.042) and the average operation time was significantly shorter in subtotal hysterectomy group (aOR: 1.023; 95% CI: 1.009-1.03, p= 0.01). Conclusion: hysterectomy is essential in certain patients with severe postpartum hemorrhage. Placenta accreta is the main indication for hysterectomy. Total hysterectomy is not associated with an increased risk of complications compared to subtotal hysterectomy.
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Ginecologia , Placenta Acreta , Hemorragia Pós-Parto , Adulto , Feminino , Hemostasia , Hospitais , Humanos , Histerectomia/efeitos adversos , Placenta Acreta/epidemiologia , Placenta Acreta/cirurgia , Hemorragia Pós-Parto/etiologia , Gravidez , Estudos Retrospectivos , TunísiaRESUMO
Structuring warm-up (WU) in hot climate conditions before high-intensity efforts is still drawing the attention of researchers and practitioners. The present study investigates the effect of two WU durations (i.e.10 min: WU10 and 20 min: WU20) in a hot climate (~31°C), on thermal comfort, muscular power output and fatigue after a repeated-sprint test (RSA) in soccer players. Twelve amateur soccer players (age = 21.13 ± 1.8 years; height = 172.5 ± 4.6 cm and weight = 70.8 ± 5.1 kg) participated in a cross-over randomized study, and they underwent a soccer-specific RSA test, after two WU durations and on different days. Peak power (PP), mean power (MP) and the fatigue index (FI) were calculated and analysed. Likewise, thermal comfort/discomfort (TC), tympanic temperature (Ttym) and rating of perceived exertion (RPE) were recorded at rest, after WU and after RSA. The ANOVA showed a significant increase in MP after WU10 in comparison to WU20 by 1.9%, while PP remained similar between the two durations. A significant decline in muscular power in WU20 compared to WU10 appeared from the 5th sprinting repetition and continued to the end of the RSA. The WU20, compared to the WU10, produced higher RPE at post-WU (p < 0.001) and post-RSA (p = 0.018), and higher thermal discomfort sensation in both post-WU (p = 0.022) and post-RSA (p = 0.007) point of measures. Larger increases in Ttym were recorded after WU20 compared to WU10. WU10 in a hot climate (~31°C) best assists mean power output during soccer RSA, but not peak power. Extending the WU duration up to 20 min in a hot climate was revealed to be detrimental for muscular power output, inducing excessive thermal discomfort and fatigue. Therefore, it is important that trainers and soccer players carefully consider WU duration prior to competitions and training sessions in a hot climate, to optimize physiological responses.
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Improving acquisition and retention of new motor skills is of great importance. This study investigated the effects of progressive task difficulty manipulation (TD), combined with varying knowledge of results frequencies (KR) on performance accuracy and consistency when learning novel fine motor coordination tasks, and examined relationships between novel fine motor task performance and executive function (EF), working memory (WM), and perceived difficulty (PD). Thirty-six, right-handed, novice physical-education students (age = 10.72 ± 0.89 years) participated; participants were separated into three groups, receiving varying KR frequency (100%KR, 50%KR, and 33%KR). For each group, distance to the target was increased progressively (2 m, 2.37 m, and 3.56 m) to obtain three difficulty levels. We assessed performance during test sessions (pretest, post-test, Retention1 and Retention2) under free (FC) and time pressure (TPC) conditions. Results revealed that under FC, 100%KR improved significantly. Results revealed significant linear improvements in accuracy for 50%KR and 33%KR under TPC. New findings indicate that the association between TD and KR (50%KR) may provide more appropriate cognitive loads compared to 33%KR and 100%KR groups. These have implications for practitioners because, while strategies are clearly necessary for improving learning, the efficacy of the process appears to be based on the characteristics of the learners.
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Aprendizagem , Destreza Motora , Criança , Retroalimentação , Humanos , Análise e Desempenho de TarefasRESUMO
Amoebiasis is a parasitosis, mainly caused by Entamoeba histolytica (E. histolytica). It is a common disease in tropical and subtropical regions. E. histolytica possesses different mechanisms of pathogenicity, and might lead to the invasion and lysis of the intestinal epithelium. Outside of the high-risk regions, acute intestinal amoebiasis is a very rare condition, often leading to misdiagnosis and death, if not promptly treated. We discuss the cases of 18 and 43 year-old men without medical history, who presented to the emergency department complaining of acute abdominal pain along with fever. Following imaging features and clinical presentation, appendicitis and a complicated form of Crohn's disease were respectively suspected. Given the severity of the symptoms, an explorative laparotomy was performed showing in both cases an inflammatory aspect of the intestine. Histological examination concluded intestinal amoebiasis, a diagnosis that wasn't suspected at first. The learning point of these cases is considering invasive intestinal amoebiasis in patients presenting with an acute abdominal syndrome, even with no history of traveling abroad or immunodeficiency.
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BACKGROUND: This study addressed the lack of data on the effect of warm-up (WU) duration in hot-dry climate (~ 30 °C; ~ 18% RH), on thermoregulation, muscular power-output, and fatigue after specific soccer repeated-sprint test (RSA). METHODS: Eleven amateur soccer players participated in a cross-over randomized study and they underwent the Bangsbo repeated-sprint test, after three WU durations (i.e. WU10, WU15 and WU20 min) at 70% of MAV, and on different days. Peak power (PP), mean power (MP) and the fatigue index (FI) were recorded and analyzed. Likewise, heart rate (HR), tympanic temperature (Ttym), mean body temperature (MBT) and rating of perceived exertion (RPE) were recorded during each session. RESULTS: The repeated measure ANOVA showed that MP improved after WU15 in comparison to WU10 and WU20 (p = 0.04 and p = 0.001; respectively). Nonetheless, no significant effect on PP was recorded after all WU durations. FI during RSA increased after WU20 in comparison to WU15 and WU10 (p < 0.001 and p = 0.003; respectively). Higher RPE values (p < 0.001) were recorded after WU15 and WU20 in comparison to WU10 duration. The two-way ANOVA showed higher ΔTtym and ΔMBT values after WU15 and WU20 compared to WU10 (p = 0.039 and p < 0.001for Ttym; p = 0.005 and p < 0.001 for MBT, respectively). CONCLUSIONS: The WU15 at 70% of MAV better assists mean power-output during soccer RSA in hot-dry (~ 30 °C; 18% RH) climate, but not peak power. Reducing WU duration up to 10 min seems to be insufficient to induce beneficial physiological changes necessary for optimizing repeated-sprint performance, while its extension up to 20 min remains detrimental for muscular power and induces higher fatigue.
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Fatty acid sugar esters are non-ionic surfactant active agents with excellent performance and many uses. This work is devoted to the synthesis of sugar esters by the esterification reaction of sugar with mixed carboxylicpalmitic anhydrides using resin Amberlyst-15 as heterogeneous acid catalyst. These anhydrides should be stable and react as acylating agents. Influence of different reaction parameters, such as the molar ratio (sucrose/anhydride), the type of solvent and the reaction time on the yield of the esterification reaction were studied. The esterification reaction of sucrose with mixed palmitic benzoic anhydride leads to a mixture of sucrose esters of palmitic acid with a good percentage of conversion. The mixed anhydride was both reactive and selective for the preparation of fatty acid ester.
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Benzoatos/química , Ácidos Carboxílicos/química , Técnicas de Química Sintética/métodos , Ésteres/síntese química , Ácidos Graxos/síntese química , Ácido Palmítico/química , Sacarose/síntese química , Acilação , Catálise , Esterificação , Solventes , Estirenos , Tensoativos/síntese química , Fatores de TempoRESUMO
While augmented feedback (AF) is widely acknowledged to affect motor learning, the effects of mode of feedback on motor learning acquisition, retention, and perceived competence has rarely been studied. The present investigation analyzes the effects of verbal, haptic, and combined (verbal and haptic) feedback when learning a novel gymnastic parallel bars task. Forty-eight physical education students and four expert gymnastics teachers participated in the study. We divided the students into three AF groups (verbal, haptic, and combined) and a no-feedback control group (CG). One gymnastics teacher led the learning sessions, while the others evaluated student performances following familiarization, acquisition, and retention learning phases. All sessions were video recoded, and the experts gave blind assessments according to an adapted gymnastic point code. We recorded task perceived difficulty (PD) and students' perceived self-competency throughout the sessions. A repeated measures analysis of variance revealed a significant effect of AF mode on acquisition and retention such that combined AF was best for learning stability and retention (19.1% improvement for combined vs. 9.9% for haptic and 6.9% for verbal). Similarly, participants in the combined AF group, relative to the verbal and haptic AF groups, also reported lower perceived difficulty and higher perceived self-competency after the retention phase. PE teachers are encouraged to combine verbal and haptic AF when teaching new motor skills.
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Desempenho Atlético/fisiologia , Retroalimentação Sensorial/fisiologia , Destreza Motora/fisiologia , Prática Psicológica , Retenção Psicológica/fisiologia , Adulto , Feminino , Humanos , Masculino , Percepção da Fala/fisiologia , Percepção do Tato/fisiologia , Adulto JovemRESUMO
INTRODUCTION: Colonic occlusion is the mode of discovery of 8 to 29% of colonic neoplasms. Our objective is to compare the placement of stent versus colostomy in the management of obstructing cancer of the left colon. MATERIAL AND METHODS: We have carried out a systematic search of literature from MEDLINE, EMBASE and Cochrane Library database to identify articles related to the comparison of stent versus colostomy published between 2000 and 2016. RESULTS: We have identified 6 studies. Only one study was prospective comparative. Three studies were for curative purposes. The total number of patients was 7205. In the "stent" group, there was a decrease in the average length of hospital stay compared to the "stoma" group and there was a decrease in cost with a statistically significant relationship. There was no difference between the two groups in terms of 4 hospital mortality and early morbidity. CONCLUSION: In case of neoplastic occlusion of the left colon, the choice between colostomy or colonic stent depends on the therapeutic strategy. Indeed, for curative strategy or administration of anti-angiogenics, it is recommended to practice a colostomy. However, for palliative treatment, colonic stenting is the treatment to follow.
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Neoplasias do Colo/complicações , Colonoscopia , Colostomia , Obstrução Intestinal/terapia , Stents , Humanos , Obstrução Intestinal/etiologia , Cuidados PaliativosRESUMO
Heart sound analysis is commonly used by physicians during auscultations to evaluate cardiac activity as a first line. These sounds originate from heartbeats and the resulting blood flow, and can provide important information about heart function and hemodynamics. The monitoring of heart sounds in patients suffering from chronic cardiac pathologies can be useful to detect or prevent cardiac events. For this purpose, a bimodal implanted gastric stethoscope was developed allowing home monitoring of electrophysiological and mechanical parameters.An in-vivo experiment in pigs was carried out to validate the feasibility of heart sound detection from an accelerometer embedded in a stethoscope prototype implanted in the submucosal layer of the gastric wall. Data recorded over several weeks validate the tolerance and the sensitivity of the device. These promising preliminary results confirm the interest of considering the stomach as a strategic implantation site for heart sound monitoring.
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Ruídos Cardíacos , Implantes Experimentais , Monitorização Fisiológica/instrumentação , Estetoscópios , Animais , Auscultação , Humanos , Estômago , SuínosRESUMO
The article deals with the use of mixed anhydrides for the synthesis of fatty esters. Both aliphatic and aromatic acids are involved, indicating different behaviors according to the chain length of the aliphatic acid. We describe a novel and efficient method for the synthesis of fatty esters by the esterification reaction of primary, secondary and tertiary alcohols with mixed carboxylic-palmitic anhydrides using resin Amberlyst-15 as heterogeneous acid catalyst. Influence of various reaction parameters such as molar ratio (anhydride/alcohol), catalyst amount, type of alcohol and type of mixed anhydride were studied to optimize the conditions for maximum yield. Among tested anhydrides we quote mainly the 4-chlorobenzoic palmitic anhydride because it was both reactive and selective for the preparation of palmitic acid ester. This anhydride gave a good yield of palmitic ester.
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Anidridos/química , Ésteres/síntese química , Ácidos Graxos/química , Estirenos/química , Ácidos Carboxílicos/química , Catálise , Clorobenzoatos/química , Esterificação , Ácido Palmítico/químicaRESUMO
The aim of the study was to compare the effect of stretching procedures on global coordination and accuracy in instep soccer kicks achieved in different stress conditions. Twenty male young soccer players completed the global coordination test (GC), the instep kicking accuracy test in free (FKA) and in time-pressure (TPKA) conditions, either after static (SS), dynamic (DS), ballistic (BS) or no-stretching (CTR) protocols, on nonconsecutive days and in a randomized order. After performing a 5min standardized intensity jogging (70% of MAV), followed by stretching exercises for 10min, each participant completed, successively, the GC, FKA and TPKA tests. Accuracy data, heart-rate, rating of perceived exertion and task difficulty perception were recorded and analyzed using a two-way ANOVA. GC scores were analyzed using one way ANOVA with repeated measures. The results showed higher GC and TPKA performances after DS and BS procedures. However, there was no effect of the stretching procedures on FKA. The GC scores increased by 10.8% and 7.2% after DS and BS, respectively, but were not affected by SS. Compared to FKA, the TPKA accuracy significantly decreased by 20.2% after CTR (p<0.01) and 30.7% SS (p<0.001) with no significant difference after DS (10.1%; p>0.05) and BS (11.0%; p>0.05). The use of dynamic and ballistic stretching yielded to better GC scores and helped reducing the adverse effect of time-pressure on instep kicking accuracy. Consequently, dynamic and ballistic exercises can be recommended before practicing activities requiring coordination and lower limbs speed and accuracy.
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Desempenho Atlético/fisiologia , Exercícios de Alongamento Muscular , Futebol/fisiologia , Adolescente , Análise de Variância , Atletas , Criança , Humanos , Corrida Moderada , Extremidade Inferior/fisiologia , Masculino , Reprodutibilidade dos TestesRESUMO
BACKGROUND: The present study addressed the lack of data on the effect of different types of stretching on selected measures of throwing accuracy. We hypothesized that the stretching procedures, within pre-exercise warm-up, could affect the accuracy and the consistency in throwing darts performances under different stress conditions. METHODS: Eighteen right-handed schoolboys (13.1±0.4 years, 166±0.1 cm and 54.5±9 kg; mean±SD) completed the Darts Throwing Accuracy Test in free (FDT) and in time-pressure (TPDT) conditions, either after static (SS), dynamic (DS), ballistic (BS) or no-stretching (NS) protocols, on nonconsecutive days and in a counter-balanced randomized order. After performing 5 minutes of light standardized jogging and one of the three stretching protocols for 10 minutes, each participant completed the FDT and TPDT tests. Mean scores, missed darts and variability of scores, were recorded and analyzed using a two-way ANOVA with repeated measures. Heart rate (HR), ratings of perceived exertion (RPE) and the task difficulty perception (DP), were recorded through each experimental session. RESULTS: There was no effect of the stretching procedures on accuracy in FDT. However, in the TPDT condition, better performances were recorded after NS and SS compared to DS and BS. The accuracy performances decreased in TPDT by 9.6% after NS (P<0.01); 15.3% after DS (P<0.001) and 11.8% after BS (P<0.001); but not after SS (P<0.05). CONCLUSIONS: Static stretching helped reducing the adverse effects of time-pressure on darts throwing performance. Consequently, static exercises are recommended before practicing activities requiring both upper limbs speed and accuracy.
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Desempenho Atlético/fisiologia , Exercícios de Alongamento Muscular/métodos , Extremidade Superior/fisiologia , Exercício de Aquecimento/fisiologia , Análise de Variância , Feminino , Humanos , Masculino , Distribuição Aleatória , Estresse Psicológico/psicologiaRESUMO
To realize a practical and green chemistry, two important challenges need to be addressed, namely the effective process for the activation of reaction and efficient, eco-friendly and robust chemical methods for the reaction conversion to target products via highly selective catalytic and reactions. Ultrasonic energy promotes the conversion process through its special cavitational effects. Combined with anion-exchange resin as a heterogeneous, reusable and efficient catalyst, Ultrasonic energy enhances the Knoevenagel condensation and leads to reduced reaction time at lower reaction temperature with less amounts of solvent and catalyst.
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This paper presents an improved synthesis of trans-chalcones and α,α'-bis(arylmethylidene) cycloalkanones under ultrasound irradiation in the presence of commercial acid-resins as catalysts in solvent free conditions. Several trans-chalcones and α,α'-bis(arylmethylidene) cycloalkanones were synthesized in good yields and excellent selectivity in a short reaction time.
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Resinas de Troca de Cátion/química , Cetonas/síntese química , Poliestirenos/química , Sonicação , Estirenos/química , Ácidos Sulfônicos/química , Catálise , Cetonas/químicaRESUMO
Tunisian acid activated clay was investigated as catalyst in the esterification of stearic acid with ethyl alcohol, carried out in a semi-continuous reactor. Kinetic study shows that the reaction is first order with respect to acid concentration. The activation energy found was 21 kJ/mol. This result suggests that the reaction process was controlled by a diffusional step. A kinetic model, giving the apparent constant rate as a function of temperature and catalyst concentration, has been established. This equation has been then successfully applied for a complex mixture of fatty acid.
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Silicatos de Alumínio/química , Ésteres/síntese química , Ácidos Esteáricos/química , Ácidos Sulfúricos/química , Catálise , Argila , Ésteres/química , Etanol/química , Cinética , TunísiaRESUMO
This paper presents a novel solvent free method of synthesis of trans-chalcones. The method was based on ultrasound irradiation of the reagents (aryl methyl ketones and aryl aldehydes) in presence of commercial acid-montmorillonites as catalysts. The trans-chalcones were synthesized in high yields (85-95%) and excellent selectivity in a short reaction time.