Investigating the effect of light color temperature on selective attention, error and human reaction time

Background and aims: The reaction time of humans that affected by several factors includes the time that takes to stimulate the sensory organs and the stimulus effect is transmitted to the brain, then is perceived and the decision is made; consequently, the command resulting from the decision of the brain is sent from the brain to the functional organs. Failure to respond at the right time may result in human error and accidents. There are important factors that affect the reaction time. Attention is one of the important factors affecting the speed of the reaction. Selective attention and correct perception of several stimuli among the other stimuli is one of the effective factors in promoting performance and safety. Additionally, various environmental factors may be effective in determining selective attention, increasing the number of errors and the human response time in detecting triggers. Lighting is one of the factors affecting the processing mechanisms of the brain. In the design of indoor and outdoor lighting systems, the quality parameters of the lighting system are usually less considered. Color temperature is one of the most important qualitative parameters of light, which is measured by the Kelvin unit and is an indicator for the brightness and color of the light. The aim of this study was to investigate the effect of light color temperature on selective attention, error rate and reaction time. Methods: This research is an interventional and laboratory study in order to determine the effect of the light color temperature on human error, selective attention, and reaction time of students in Tarbiat Modares University (TMU) of Tehran during the fall of 2018. All students were in the same age range. The inclusion criteria for this study were; not having any eye-related diseases, such as diminished vision and subtlety, and mental-psychiatric disorders. On the day before performing the test, participants were informed to: have enough sleep and rest, adhere to a regular diet, and avoid taking medicines, coffee and caffeinated drinks. In this interventional study, 92 students (36 female and 56 male) from Tarbiat Modarres University of Tehran with an average age of 28.33 years were recruited as subjects. The measurements and tests related to selective attention and reaction time of individuals were performed in 4 locations with an equal lighting system and different color temperatures (3500, 4000, 5000, or 6500 degrees Kelvin). In the first step of the study, in order to determine the effect of light color temperature on the studied parameters, the participants were randomly divided into four groups with 24 subjects in each group. Before the main test was being performed, the participants were kept in rooms adjusted to a brightness of 3500° K to rest for at least 5 minutes in order to be adapted to the situation, and then, in the same conditions, to become familiar with the test method they were studied with the Stroop software. In the second step, each group was placed in a separate room where the levels of brightness had been designed with one of the lighting systems to yield a color temperature of 3500, 4000, 5000, and 6500° K. Cognitive performance tests including reaction time, accuracy and selective attention were measured using Stroop tests. Measurement of score interference and time interference, which are indicators for selective attention, were calculated by measuring the difference in the error rate and the reaction time in detecting incongruent and consonant words. Stroop test was used to determine the reaction time, error and other parameters. This test consists of two parts; the practice and the main test, each of them has two stages. The first step is to name the color of circular shapes that appears on the laptop monitor screen. The participant, upon viewing the image, applies pressure on keyboard buttons which are labeled with colors corresponding to the ones on the screen. The second step is to name the word which appears in a white box. The names of the colors appear, and as soon as the correct word is recognized, the participant should press the color word associated to the word on the keyboard. The third step, which is the main stage of the test, is a non-consistent word (red-green-blue) that shown randomly and sequentially on the monitor's screen. The subject must only press the keyboard button with the same color, only emphasizing the color and regardless of its connotation. In this test, 48 consistent colored words (the color of the word is identical with the meaning of the word; red, yellow, green and blue) and 48 non-consistent colored words (the color of the word is not the same as the word meaning; for example, the blue word shown in red). The time lap between the stimulants was 800 milliseconds and the duration of each of them was 2000 milliseconds. The subject's task was to select the correct color only. Finally, the data were analyzed using SPSS software. Results: Based on the results of this study, the highest mean of correct selection (474.49 ± 10.65) and the lowest mean of the correct ones (654.49 ± 11.77) were assigned to the color temperature of 6500 and 3500 ° K, respectively. Also, the highest mean of error rate (15.65 ± 9.77) and the lowest mean of error rate (10.94 ± 9.4) were reported at a color temperature of 3500 and 6500 ° K, respectively. According to the results of this study, with increase in color temperature from 3500 to 5000° Kelvin, the number of questions that were not responded decreased. Likewise, the number of unanswered questions for the color temperature of 6500 °K slightly increased compared to the color temperature of 5000 and 4000 °K. The results also indicated that, with an increase in color temperature from 3500 to 6500 °K, the reaction time to visual stimuli also decreased. The highest interference score was in the light color temperature of 3500 °K which indicates that the number of faults in naming inconsistent words relative to consonant words was higher in color temperature of 3500° K compared to other color temperatures. Also, according to Fig. 3, the maximum interference time was at 6500 ° K. This indicates that the performance time of the subjects in naming inconsistent words was higher relative to consonants in color temperature of 6,500° K compared to other color temperatures. Although the average response time under lighting condition with color temperature of 6500° K (718.95 ± 65.33) was less than the color temperature of 3500° K (728.58 ± 43.48), according to the results of the study, with a decrease in color temperature, the increase in mean response time was observed, but this difference was not significant (p p). Also, based on independent t-test (Table 2), there was a significant relationship between subjects' gender and variables such as interference score, interference time and number of unanswered questions. For all of these three variables (interference score, interference time and number of unanswered questions) mean in men was significantly lower than women (p <0.05). Based on subjects' gender, the average response time under different color temperatures showed that the response time (or reaction time) of female under lighting conditions with 3000 and 5,000 ° K was higher than male, while under lighting conditions with 4000 and 6500° K the response time of male was higher than female students. Although the average response time under different color temperatures was different between male and female subjects, based on the results of independent t-test, such difference was not significant. Conclusion: In general, the results of this study showed that when subjects are exposed to light color temperature of 6,500 ° K, the number of correct responses by them is higher than those exposed to other color temperatures, and with increasing the color temperature, the number of correct answers increases. Also, according to the results of this study, the error rate decrease by increasing color temperature of light source. Based on the results of this study, it is suggested to make use of light sources with a color temperature of 6,500 ° K in designing the lighting system of the places where human reaction time and error are high importance. Accordingly, it is recommended to repeat this study in other demographic groups, as well as taking into account the qualitative parameters of the lighting system in addition to its quantitative parameters. © 2020 Iran University of Medical Sciences. All rights reserved

The relations of job stress dimensions to safety climate and accidents occurrence among the workers

Based on a literature review, likely, there is a relationship between job stress and safety climate, and in this way, the accident occurrence is affected. Therefore, the present study was aimed to investigate the relations of job stress dimensions to safety climate and accidents occurrence among the workers using regression models. This cross-sectional study was carried out on 1530 male employees in 2019. People were randomly selected from various departments. The participants filled out the questionnaires, including demographical information and accident history questionnaire, the NIOSH generic job stress questionnaire, and the Nordic safety climate questionnaire. In addition, information on occupational experience and accident history was obtained from the health unit of the petrochemical company. In the end, data were analyzed using statistical tests of bivariate correlation, multivariate correlation, and logistic regression. Based on the bivariate analysis, the variables of job satisfaction (0.998), problem at work (0.900), depression (-0.836), and physical environment (-0.796) among the job stress dimensions had the highest correlation coefficients with the total score of the safety climate, respectively. The results of the logistic regression analysis with the adjustment of the effect of the safety climate indicated that the relationships between the dimensions of the job satisfaction (Wald = 6.50, OR = 4.96, and p-value<0.05) and social supports (Wald = 5.88, OR = 3.20, and p-value<0.05) with the accident occurrence were significant. To increase the positive safety climate and decrease the accident occurrence, industries must try to reduce job stress in the workplaces through controlling the important factors, such as low job satisfaction and poor social supports

Evaluating the Potential Risk of Musculoskeletal Disorders and Postural Loading of Task Postures in Bakery

Background: Bakery workers due to the nature of their job are at risk of musculoskeletal disorders caused by ergonomic factors. The purpose of this study was to evaluate the biomechanical risk factors for musculoskeletal disorders in bakery workers. Methods: In this study, all tasks of baking Sangak, Taftoon and Lavash in the bakeries in Gonabad were selected based on census method, and, Hierarchical Task Analysis (HTA) method was used for task analysis and job was degraded to tasks, actions and movements., LUBA and OCRA method was implemented to identify common risk factors in repetitive tasks that can contribute to develop musculoskeletal disorders of upper limbs. Finally, the results were analyzed using SPSS 17. Results: According to the results of this study, the score of OCRA index for employees as Chanegir (a person who makes dough balls) and baker investigated in 3 types of bakery was more than 4(red area). In general, LUBA score was obtained more than 10 for the 83.33% of workers in Tafton bakeries, 100% of Sangak bakery employees and 91.66 % of workers in Lavash bakery. LUBA score for any samples was not below 5 (action level one). Highest relative discomfort score for Nangeer (a person who takes bread out of oven) and baker of Tafton bakery was in back area and in Chanegir was neck and shoulder area.&nbsp; Highest relative discomfort score in Shater, Chanegir and Nangeer of lavash bakery is was lumbar area and neck and in Shater and Nangire of Sangak bakery was in elbow and wrist area. The correlation results of OCRA index and LUBA in Lavash, Sangak and Taftoon bakery were 0.26, 0.03 and 0.24 respectively. Conclusion: The results showed that the risk of musculoskeletal disorders due to repetitive tasks was relatively high in the bakeries and ergonomic interventions were required in order to redesign the job

Assessment of the Work Ability Index among Iranian Employees: A Systematic Review

Introduction and purpose: The ability to work is one of the important factors in predicting the working conditions, well-being, and health status of employees. The Work Ability Index (WAI) is one of the most reliable tools used widely to assess the work ability in employees. This study aimed to review the WAI score among Iranian employees. Methods: In this study, Persian and English articles published within 2005-2020 were extracted by searching Magiran, SID, SCOPUS, Web of Science, Google Scholar, and PubMed databases. The WAI and its relationship with individual and demographic factors, including age, work experience, gender, and education level, were examined. Results: A total of 42 articles that reported the mean and standard deviation of the WAI were selected. The review of the articles showed that a total of 11,231 subjects were investigated and the mean WAI was 38.35±5.88. Moreover, among job and demographic factors, WAI showed the most significant relationship with age and work experience. Conclusion: Based on the WAI classification, the score of employees was at a good level. However, in some occupations, it was observed that the work ability was at a moderate level, highlighting the adoption of control measures to improve the working environment

The effect of noise exposure on the level of sex hormones in male rats addicted to opium

Background and aim: Noise pollution was the most common environmental factor and widespread physical harmful agent in the workplaces. Large numbers of workers were exposed to noise pollution in various sectors of industry, agriculture, mineral and so on. In the 21st century, exposure to noise is recognized as one of the threats to the health of the community. Hearing loss (temporary or permanent), increased blood pressure, sleep disturbances, lack of concentration, and increased human error can be attributed to exposure to noise. World Health Organization (WHO) has identified noise as the second environmental stressor in the world. In Iran (As a developing country in the Middle East), more than 2 million workers are exposed to a noise level higher than 85 dB. Stress caused by noise can affect the level of sex hormones. A study by Nadri et al. found that exposure to 100 dBA continuous noise significantly reduced the level of sex hormones (testosterone, follicular stimulatory and luteinizing hormones). Addiction is one of the greatest problems of human societies which not only causes social and behavioral disorders, but also affects various aspects of physical health, imposes huge financial losses on individuals, families and society. Opium comes from opium poppy and consists of more than twenty alkaloids (combination of seventy compounds). Among the diverse varieties of narcotics, opium and heroin, they have the highest global consumption. The most commonly used drug opium is oral (swallowing) (49.5) and inhalation (drainage) ((59). For various reasons, such as having a common border with Afghanistan (as a producer of 90 percent of the world's opium), opium drug abuse among Iranian industrial workers has a relatively high prevalence. Some people believe that long-term use of low-dose opioids may prevent chronic illness (Such as cardiovascular disease) and prolong life. Addiction is a problem that has spread increasingly amongst different populations around the world, and the labor community is no exception to this rule. A study in the Asalouyeh industrial region (Located in the southwest of Iran) showed that drug use among camp workers is between 15 and 25, and the most commonly used opium. Reports indicate that opioids reduce the secretion of LH and FSH gonadotropins by inhibiting the release of gonadotropin releasing hormone secreted from the hypothalamus, while gonadotropins are crucial for the survival of testicular cells, and their reduction to planned cell death. The results of previous studies confirmed that exposure to noise and opium consumption alone had a downward effect on the level of sex hormones on human and animal samples. The aim of this study was to investigate the effects of exposure to noise and opium consumption on sex hormones in male animal models (rat). Methods: In this Experimental and cross-sectional study completed in 2018, 36 healthy adult male Wistar rats (purchased from the Tehran Pasteur Institute) were randomly divided into six groups (after initial screening from the point of view weight, age, etc.); control, exposure to noise (100 dB and 700-5700 Hz frequency range for 8h/day), consumption of opium solution(50 mg per case), consumption of opium solution(100 mg per case), exposure to noise (100 dB and 700-5700 Hz frequency range for 8h/day), consumption of opium solution(50 mg per case) and exposure to noise(100 dB and 700-5700 Hz frequency range for 8h/day) and consumption of opium solution(100 mg per case). The frequency range of 700 to 5700 Hz was chosen from a combination of 1000, 2000, and 4000 Hz central frequencies in octave band spectrum (based on rat and human hearing sensivity in this range). Noise level (100 dB) was produced by signal software and implemented by Cool -Edit software. After boosting with an amplifier, with installation of four speakers on top of the chamber, the noise was broadcast in the reverberant chamber. The dimensions of the reverberant chamber (Plexiglas) were selected based on the Bolts chart, the required space per rat and the animal welfare (49�59�30 cm with 5 mm thickness). The noise level was monitored during exposure by calibrated sound level meter (model cel-450) hourly. The air inside the chamber was changed 12 times every hour. Opium was prepared by getting the necessary Legal licenses from the police and the Food and Drug Administration and then opium solution (dissolved in hot distilled water) was fed to animals at different doses (50 and 100 mg per case) through gavage tube between 6:30 to 7:00. In order to ensure that the rats were addicted (groups 3, 4, 5, and 6), at the end of the first week, with naloxone injection (2 mg per kg), the hangover symptoms of the animal were evaluated and the addiction was confirmed. The ambient temperature of the animal house was adjusted throughout the test period in the range of 20-24 �. After 50 days (cycle of spermatogenesis in rats), following anesthesia (Xylazine - ketamine), blood samples were collected (5 ml of the left ventricle). Using centrifuge, the serum should be discarded at 3000 rpm for 15 minutes. Level of sex hormones (testosterone, follicular stimulatory and luteinizing hormones) was determined by specific rat kits (produced by Zelbio Company) and ELISA technique. The ethics of working with animals, according to the Helsinki Statement and the Ethics Committee of Tarbiat Modares University, were observed at all stages of the study. Data analysis was performed with SPSS software (version (22)) by using ANOVA test (Tukey Post hoc test). Results: This study is a first study in the world that examines the effect of exposure to noise and opium consumption on sex hormone levels in an animal model. In this study, noise could significantly suppress the levels of testosterone and luteinizing hormones, but did not affect the level of follicular stimulatory hormones. The results of this study (about the noise agent) are consistent with studies by Swami et al., Paramanik et al. And Rafuli et al. Both doses of opium solution (50 and 100 mg per case) can significantly reduce the level of sex hormones (testosterone, follicular stimulatory and luteinizing hormones). However, no significant difference was found between two doses in any of the examined hormones. In 2012, the study of Yasin Kahimin showed that levels of testosterone decreased significantly in opioid recipient groups, which were consistent with the results of the present study in relation to lowering the secretion of testosterone and LH. A study by Salman et al in 2010 showed that levels of testosterone, LH and FSH in opiate addicted men decreased significantly compared to control group. Sepehri et al. Study showed that levels of LH, FSH and testosterone levels in addicted people were significantly lower than those in the control group. Combining the two factors of noise and opium (with opium solution doses of 50 and 100 mg per rat) could have significant boosting effects in suppressing levels of testosterone and luteinizing hormones while this enhancing effect was assessed for an increase in follicular stimulatory hormones (Comparison of groups 5 and 6 compared to control group). Increasing the opium solution dose from 50 to 100 mg per rat did not make a significant difference in the level of sex hormones (comparison of groups 3 and 4 as well as groups 5 and 6). In this study, the noise and opium solution did not significantly change the rat weight in various groups compared to control group. In the first week of the study, gastrointestinal disorders (such as diarrhea) were observed in the exposed group, but over time, this disorder was eliminated. Conclusion: The use of opium for medicinal or recreational purposes has a high historical background in many parts of the world. Due to the effect of reducing noise and opium addiction on the level of testosterone and luteinizing hormones, it is suggested that in the periodic examinations of workers it should be emphasized by medical professionals as a prognosis for infertility. More studies are needed to determine the effect mechanism of noise and opium consumption on pituitary-gonad axis. In this study, only opium was used as one of the most commonly used drugs in the community. Therefore, it is suggested that future studies on narcotics such as heroin, cannabis, etc. should be put on the agenda of researchers. In order to cope with the destructive effects of exposure to noise and other harmful physical hazards in the working environments, various methods of engineering, management, or use of inexpensive and available antioxidants, such as cinnamon, can be used. Based on the results, it can be concluded that chronic consumption of opium can significantly decrease the function of gonad-pituitary secretion, and this can lead to suppression of libido and infertility. It is suggested that the effects of opium in different doses should be considered in future generations. © 2020 Iran University of Medical Sciences. All rights reserved

Morphological, acoustical, mechanical and thermal properties of sustainable green Yucca (Y. gloriosa) fibers: an exploratory investigation

BACKGROUND: The objective of this study was to evaluate the acoustical, morphological, mechanical and thermal properties of fibers extracted from the leaves of Yucca (Y. gloriosa) shrub. METHODS: Several tests were performed on either untreated or alkali-treated (5% NaOH) fibers. The chemical analysis of the fibers was performed to determine their lignin, cellulose, hemicellulose, wax and moisture content. Fourier transform infrared (FTIR) and thermogravimetric analysis were respectively employed to chemically and thermally analyze the fibers. The microscopic examination was also carried out using scanning electron microscope (SEM). INSTRON universal testing machine and an impedance tube system were employed for measuring the tensile properties of the fibers and the sound absorption coefficient values of the samples fabricated from the same fibers, respectively. RESULTS: The results from the experiments revealed that the fibers have low density (1.32 g/cm3) and higher cellulose content (66.36 wt.%,). The mechanical characterization of these fibers also confirmed they are similar to the other lignocellulose fibers used for the reinforcement of polymer matrix composites. The tensile strength test conducted on Yucca fibres showed that mechanical properties of alkali treated fibers are superior to the untreated fibers. The thermal analysis also demonstrated that the alkali treated fibres can thermally withstand temperatures of up to 364 °C which confirms the fact that the thermal stability of fibers was improved by alkali treatment. CONCLUSION: Fibers extracted from the leaves of Yucca demonstrated fair amounts of mechanical and thermal resistance and strength. The samples fabricated from Yucca fibers demonstrated fair levels of sound absorption coefficients particularly at higher frequency ranges which are typical to the other natural fibers. The possible use of Yucca fibers as either a reinforcing agent for composites or a sound absorbing medium is highly promising