Monitoring of praseodymium(III) ions in aqueous solutions, soil and sediment samples by a PVC membrane sensor based on a furan-triazole derivative

A furan-triazole derivative has been explored as an ionophore for preparation of a highly selective Pr(III) membrane sensor. The proposed sensor exhibits a Nernstian response for Pr(III) activity over a wide concentration range with a detection limit of 5.2×10-8 M. Its response is independent of pH of the solution in the range 3.0-8.8 and offers the advantages of fast response time. To investigate the analytical applicability of the sensor, it was applied successfully as an indicator electrode in potentiometric titration of Pr(III) solution and also in the direct and indirect determination of trace Pr(III) ions in some samples

Stimulus-Change Probability and Inter-Stimulus Interval Effects on the Acoustic Change Complex

Introduction: The Acoustic change complex (ACC) is an obligatory cortical auditory evoked potential (CAEP) evoked by a change in the acoustic properties of an ongoing stimulus. The ACC may be considered a bio-marker of the stimulus change as discriminated at the level of the primary auditory cortex. Inter-stimulus interval (ISI) and stimulus-change probability are factors that affect the CAEP P1-N1-P2 onset response latency and amplitude. Specifically, CAEP onset responses increase in amplitude as stimulus ISI increases and probability decreases. It is likely that the effects of ISI and stimulus-change probability on the ACC are similar to those for the P1-N1-P2 onset complex. The present study was undertaken to test that prediction. The overarching goal of this work is to develop valid, efficient, sensitive and specific methods for using ACC in diagnostic audiology. Methods: Participants: Twenty young adults (mean age =27 years) with normal (<20 dB HL) pure tone hearing thresholds participated in this study. Stimuli: The stimuli were 1000 Hz and 2000 Hz pure tones, each with 400 ms total duration, which were further shaped with a 20 ms Hanning-filter rise-fall envelope and presented at 80 dBA SPL. The stimulus change direction was always from 2000 Hz to 1000 Hz. Two experiments were conducted. Tokens for Experiment 1 were created by concatenating the 400 ms tokens to create an 800 ms token. The ISI was defined as the time between the offset of the 800 ms token to the onset of the next 800 ms token. The two ISIs tested were 1 and 250 ms. Experiment 2 utilized an “odd-ball” stimulus paradigm in which the 2000 Hz toneburst served as the standard and the 1000 Hz token as the deviant. The response to the deviant is the ACC. The standard vs. deviant probabilities tested were 50-50%, and 80-20% and the two ISIs tested were 1 and 250 ms. In this case, the ISI was the time between stimulus offset and stimulus onset for the 400 ms token. Control trials, for which there was no stimulus change, were obtained for each ISI and probability condition in both Experiment 1 and Experiment 2. Results: Experiment 1: ACCs were present for all stimulus change trials for both ISI conditions. Analyses of variance indicated no significant differences in the amplitudes or latencies of ACC components as a function of stimulus ISI. Mean amplitudes for the ACC P1-N1’ and N1-P2’ components were 1.15 μV and 1.19 μV, respectively. Mean latencies for the ACC components P1’, N1’ and P2’ were 72.3 ms, 133.7 ms, and 197.4 ms, respectively. Experiment 2: ACCs were present for all stimulus change trials for every combination of ISI and probability. Analysis of variance revealed that the stimulus ISI and probability had significant effects on ACC component amplitudes. P1’-N1’ amplitudes were significantly lower for the 1 ms ISI (p=0.0071) and 50% probability (p<0.0001) conditions, with no significant interaction effects. Mean amplitudes ACC P1’-N1’ were 1.71 μV for 1ms ISI-50% condition compared to 4.58 μV for 250 ms ISI-20% probability conditions. For N1’-P2’ amplitude, only probability had a significant effect, with amplitudes smaller in the 50% probability condition (p<0.0001), mean =1.95 μV, compared to the 20% probability condition, mean =4.66 μV. The analyses indicated a significant difference in the ACC P1’ latency as a function of both ISI (p=0.002) and probability (p=0.0007), with no interaction effects. Significantly shorter P1’ latencies were found for the 250 ms ISI and 20% probability conditions. Stimulus probability (p=0.0164), but not ISI, also had an effect on ACC P2’, with latencies significantly earlier for the 50% probability compared to the 20% probability. Discussion: Reduced amplitude and prolonged latencies of peaks at short ISIs may be attributed to neural refractoriness. Longer ISIs lead to availability of longer recovery periods for neurons to overcome refractory effect, thus allowing the neurons to respond with higher discharge rates, resulting in larger amplitude response. Similarly, the interval between the frequency changes would be shorter in the 50% stimulus-change probability conditions in comparison to 20% probability conditions. Neurons contributing to the ACC, would have already responded for the previous frequency change, and entered refractory state, resulting in smaller amplitude ACC. The 20% probability condition is essentially an increased ISI condition (for stimulus change) compared to the 50% probability condition. This study indicates that the ISI of the change token is the major driver of ACC amplitude, and even a change probability of 20% leads to substantial gains in ACC amplitude and therefore, detectability. This has implications for the clinical use of ACC, in that a 50% probability may be used in the first instance, as a quick screen, but if the ACC is not present at that probability, a 20% probability condition should be tested.Dissertation not available (per author's request

Evaluation of Urban Agriculture Training Courses Using Kirkpatrick’s Model

The aim of the present study was to evaluate urban agricultural education effectiveness based on the Kirkpatrick model in Tehran, Iran. The study participants of this research were included all citizens participated in educational and counselling centers focused on flowers and plants in district two of Tehran municipality during 2016. The study participants consisted of 160 individuals, including 80 in the case group and 80 in the control group. The case group participated in urban agriculture training courses and the control group did not receive any training courses. The result showed a significant difference between the knowledge status of citizens before and after attending educational courses (p < 0.01). Also, more than 86% of the citizens perceived the courses' effectiveness at moderate to high levels. In addition, there was a significant difference between the case and control groups in terms of reaction and behavior levels (p < 0.01). The present study found that the urban agriculture training courses for citizens exhibited considerable effectiveness in the measurement results of the three levels of the Kirkpatrick model and that overall, the course had received positive evaluations. Therefore, these training courses can be recommended to enhance the knowledge of citizens about urban agriculture

Preparation of a Modified Octadecyl Silica Membrane Disk for Solid Phase Extraction of Lead(II) Ions in Different Real Samples and their Determination with ICP-AES

A solid phase extraction and inductively coupled plasma atomic emission spectrometry (ICP-AES) for the determination of lead(II) ions with octadecyl-bonded silica membrane disks modified by 4-methyl-N-{2-(4-methylbenzothioyl)aminoethyl}benzenecarbothioamide (MMAB) was studied. Extraction efficiency, and the effects of parameters such as flow rate, pH, type and the least amount of acid for stripping of lead(II) from the modified disks andbreak through volume were examined. The maximum capacity of the membrane disks modified by 4.0 mg of MMAB used was found to be 527 ± 4 µg of lead(II) ions. The preconcentration factor is 440 (for 2200 mL water sample and flow rate of 12 mL min-1) and detection limit of the proposed method is 85.4 ng mL-1. The developed method was successfully applied to the determination of lead(II) ions in blood, spinach, bean, hair, milk, pepper and various water samples

Analysis of Constrains Facing Urban Agriculture Development in Tehran, Iran

The purpose of the study was to identify the constrainsaffecting urban agriculture in Tehran, Iran. The statisticalpopulation of this study consisted of city dwellers within the 22municipal districts of Tehran out of which 320 individuals wereselected as the sample of the study. Cochran’s formula was usedto determine the sampling size based on stratified samplingmethod. A panel of experts confirmed the validity of the questionnaireused in this study. The calculated Cronbach’s alpha forthe main sections of the questionnaire was 0.95 and 0.93. Resultsof the ranking of constrains and challenges revealed that “highstart-up costs” and “lack of knowledge among managers andauthorities” were among the most important constrains. Theresults of factor analysis revealed that 7 factors including “education-research”, “infrastructure”, “support”, “regulations andpolicy making”, “technical”, “financial-economic” and “cultural”explained 67.36 of the variance. Although list of constrainsrevealed is not perfect, this work paves the way for furtherresearch regarding factors influencing urban agriculture. It alsoprovides interesting information for planners about the challengesof urban agriculture development

بررسی تأثیر جایگاه گوشی بر آستانه‌های ادیومتری صوت خالص در محدوده فرکانسی مرسوم

مقدمه: بدون شک ادیومتری صوت خالص از پایاترین آزمون‌های موجود جهت بررسی مشکلات سیستم شنوایی است. جایگاه گوشی، از جمله عواملی است که تأثیر زیادی بر ارزیابی دقیق آستانه‌ها دارد. پژوهش حاضر با هدف، بررسی تأثیر جایگاه گوشی بر آستانهظهای ادیومتری صوت خالص در محدوده فرکانسی مرسوم انجام شد. مواد و روش‌ها: در مطالعه مقطعی حاضر، 50 فرد بزرگسال (25 زن و 25 مرد) 25-18 ساله به صورت تصادفی ساده، انتخاب و مورد ارزیابی قرار گرفتند. از تمام افراد تاریخچه‌گیری، اتوسکوپی و تمپانومتری گرفته شد و سپس آستانه‌های شنوایی آن‌ها در محدوده فرکانسی مرسوم (با گام‌های 5 و 1 دسی‌بل) در هر دو گوش تعیین گردید. گوشی مربوط، یک بار توسط فرد آزمایشگر و بار دیگر توسط فرد آزمایش شونده بر روی گوش‌ها قرار داده شد و آستانه‌های شنوایی افراد به روش نزولی کسب و ثبت گردیدند. جهت تجزیه و تحلیل نتایج از آزمون Paired t استفاده شد. یافته‌ها: تفاضل آستانه‌های حاصل از تغییر جایگاه گوشی در تمام فرکانس‌های مورد ارزیابی در هر دو گوش از نظر آماری معنی‌دار بود (05/0 > P). نتیجه‌گیری: جایگاه گوشی بر آستانه‌های شنوایی در فرکانس‌های مرسوم تأثیرگذار بود و به همین دلیل توصیه می‌گردد که در ارزیابی‌های بالینی، جایگذاری گوشی در هر شرایطی توسط شنوایی‌شناس مربوط صورت پذیرد. کلید واژه‌ها: ادیومتری صوت خالص، جایگاه گوشی، آستانه شنوای