Physiological Effects of Pulsed LED Light Added to a Task Lamp to Improve Alertness on Employees of Hospital or Shift Workers / Efectos Fisiológicos de Pulsos de Luz de Diodo Adicionados a una Lámpara de Trabajo para Mejorar el Estado de Alerta en Personal de Hospitales o Trabajadores por Turnos

Abstract The aim of this study is to investigate the effect of a continuous stream of pulses of monochromatic blue pulsed (BP) and a combination of blue and green pulsed (BGP) light-emitting diode (LED) light conditions on physiological responses. This study is an approach to clarify the most suitable LED combination and flickering frequency to evoke alertness when a continuous stream of pulsed LED light is delivered and may suggest applications of continuous pulsed light as support for task illumination for shift workers, hospital nurses, school students or office employees. Combinations were delivered by exposures of BPLED and BGPLED pulses at 100, 200, and 400 Hertz over two background light colors (BLC). Participants were exposed to 12 different light conditions in a counterbalanced procedure. By integrating measures of electroencephalogram (EEG) and pupil constriction; results suggested significant changes in responses during the interaction of BLC, LED, and EEG. Beta waves exhibited a statistically significance (p < 0.05) in arousal levels when exposed to BG light, although no active task was involved during exposure. Furthermore, pupil reacted with larger constriction towards BGPLED exposure than towards monochromatic BPLED exposure, thus demonstrating that a continuous stream of pulses can deliver the same irradiance as if delivered in a continuous flow and without affecting perception as no flickering was perceived in any of the conditions by a qualitative evaluation.

Resumen Este estudio tiene por objetivo determinar cuál es la combinación de luz LED más adecuada y la frecuencia de parpadeo que esta deba tener, para evocar un estado de alerta cuando se emite un flujo continuo de la misma al combinarla con una iluminación de ambiente; y poder sugerir aplicaciones como soporte para la iluminación de tareas para trabajadores por turnos, enfermeras, médicos, estudiantes; o en oficinas y hospitales. Es de original importancia resaltar que en el mercado no existe un producto comercial que se pueda ajustar para apoyar en el trabajo al estado de alerta, se tiene la limitante que estas son pruebas a nivel laboratorio y que posteriores pruebas serán necesarias para validar el producto final. El método usado se basó en las combinaciones que se administraron mediante exposiciones de luz azul pulsada (BPLED) y luz azul y verde combinadas (BGPLED) a frecuencias de 100, 200 y 400 Hz adicionadas a la iluminación ambiental (BLC). Los participantes fueron expuestos a 12 condiciones de luz diferentes en un experimento balanceado y contrapesado. Mediante la integración de medidas electroencefalográficas (EEG) y de constricción pupilar; los resultados sugirieron cambios significativos en las respuestas durante la interacción de BLC, LED y EEG. Las ondas beta mostraron una significancia estadística (p <0.05) en los niveles de activación cuando se expusieron a la luz BGPLED, además, la pupila reaccionó con una mayor constricción hacia la exposición a BGPLED que hacia la exposición BPLED monocromática, adicionalmente se demostró que un flujo continuo de pulsos puede proporcionar una irradiación igual a la que se emite en flujo continuo; se concluyó e identificó además la frecuencia (100 Hz) que mejor evoca estado de alerta encefalográfíca y sin afectar la percepción de los usuarios en cuanto a su percepción del ambiente de acuerdo a la evaluación cualitativa.

Physiological Effects of Blue Pulsed LED in an Indoor Lighting Environment / Efectos Fisiológicos de Luz LED Azul Intermitente en un Ambiente de Iluminación en Interiores

Abstract Purpose: An experiment was conducted to investigate the physiological effects of a continuous blue pulsed light emitting diode (BP-LED) added to a task lamp in an actual indoor lighting environment and its influence in alertness having as a final purpose to develop a commercial product that could be applied in situations similar to those depicted in the present work. Design methodology: Previous research studies have stated that the addition of pulsed light evokes physiological changes that may induce alertness. The participants were exposed to four different lighting conditions. Electroencephalograms (EEG), pupil sizes, heart rates (HR), performance tests, and subjective reactions were measured. Findings: Low colour temperature light and the BP-LED revealed an improved alertness according to the data from the EEG recordings. The intervention of the BP-LED in a high colour temperature ambiance was beneficial in maintaining high levels of alertness compared to the conditions where the BP-LED was not used. It was tested that the use of a BP-LED in a task lamp may be beneficial in improving or maintaining alertness levels in an indoor workplace ambiance. Originality and Value: Designing of an adequate workplace task lamp light that improves alertness for in-house, office, or classroom situations in which it is essential.

Resumen Propósito: Un experimento fue llevado a cabo para investigar los efectos fisiológicos que una luz azul LED pulsada de manera intermitente (BP-LED), adicionada a una lámpara de escritorio, y en un ambiente interior; pueda influir en el estado de alerta de una persona con la finalidad de desarrollar un producto comercial que pueda ser aplicado para los casos desarrollados y otros posibles escenarios. Metodología de Diseño: En estudios anteriores se establece que la adición de luz en pulsaciones evoca cambios fisiológicos que pueden inducir al estado de alerta. Los participantes experimentaron cuatro escenarios de iluminación. Se registraron mediciones con respecto a encefalografía (EEG), tamaño pupilar, ritmo cardiaco, prueba de performance, así como evaluación subjetiva. Hallazgos: Los datos de EEG revelaron un mayor estado de alerta durante la exposición a iluminación cálida aunado a luz BP-LED. La intervención de luz fría y BP-LED denotó ser benéfica en el nivel de estado de alerta en comparación con las condiciones donde el BP-LED no intervino. Se logró evaluar que el uso de BP-LED en una lámpara de escritorio puede ser benéfico para mejorar o mantener el estado de alerta cuando sea usado en un espacio interior. Originalidad y Valor: Propuesta para diseñar una luminaria de escritorio; para uso casero, laboral o de estudio; que mejore el estado de alerta de las personas.

Sweating responses during activation of the muscle metaboreflex in humans is altered by time of day.

AIM: The aim of the present study was to test for a time-of-day effect on sweating responses to activation of the muscle metaboreflex. METHODS: Eight male subjects each participated in two exercise sessions, one in the morning and one in the evening. Within each session there were two 60-s bouts of isometric handgrip (IHG) exercise at 50% maximal voluntary contraction. Prior to IHG, whole body warming by a water-perfused suit initiated mild sweating. The first bout of IHG exercise began at 06.00 hours (am) and 18.00 hours (pm). Blood circulation to the forearm was occluded for 120 s, beginning 5 s before the end of the second bout of IHG to activate the muscle metaboreflex. RESULTS: During both bouts of exercise, sweating rate (SR) on both the chest and right forearm significantly increased from the pre-exercise period in both am and pm sessions. SR rapidly decreased during first minute of recovery after the first bout of IHG exercise. However, during post-exercise ischaemia (PEI) after the second bout of IHG exercise, SR was maintained significantly above the pre-exercise level only in the pm session. The increases in SR on the chest and right forearm during PEI were significantly greater in the pm, than in the am, session. However, SR of the palm was not maintained during PEI. CONCLUSIONS: We conclude that under mild hyperthermic conditions, the sweating response in non-glabrous skin to activation of the muscle metaboreflex exhibits a time-of-day effect.

Changes in surface EMG and acoustic myogram parameters during static fatiguing contractions until exhaustion: influence of elbow joint angles.

The purpose of this study was to evaluate muscle fatigue using electromyogram (EMG) and acoustic myogram (AMG) signals of the shoulder and arm muscles during sustained holding tasks, with the elbow at different angles and at different levels of maximum voluntary contraction (MVC). The EMG and AMG of four muscles, including the upper trapezius (TP), anterior deltoid (DL), biceps brachii (BB), and brachioradialis (BR), were recorded during experiments using 10 healthy young males. The experiments were conducted under 9 pairs of conditions: 3 elbow angles (120 degrees, 90 degrees, and 60 degrees) and *3 levels of %MVC (20%, 40%, and 60%). Subjects were instructed to hold a weight equal to the designated %MVC at designated joint angles and asked to maintain that condition for as long as possible until exhaustion. Joint angles were also recorded by the electrogoniometers. The analysis of variance revealed that there was no significant effect of elbow angle on the mean MVC or on the endurance time. Elbow angle showed a significant effect on mean power frequency (MPF) of EMG in DL, BB, and BR, and a significant effect on root mean square (RMS) of EMG in four muscles. In BB and BR, MPF of EMG at 120 degrees was found to be significantly lower than 90 degrees and 60 degrees, respectively. There was a significant main effect of elbow angle on MPF of AMG for TP at 20% MVC; for DL at 20% and 40% MVC; for BB at 40% and 60% MVC; and for BR at the three levels of %MVC. The results showed that the range MPF of AMG for DL, BB, and BR was between 32 to 46 Hz, whereas that for TP was from 49 to 83 Hz. There was a significant effect of elbow angle on RMS of AMG in all four muscles in all experiments. At 20% MVC, a progressive increase in RMS of AMG was observed with time. In contrast, at 40% and 60% MVC, RMS showed very different behavior; specifically, it was found that RMS of AMG at 20% MVC significantly increased with increase of elbow angle. We conclude that RMS of AMG has a good and clear correlation with elbow angle at a low level of contraction.

The effects of hedonic properties of odors and attentional modulation on the olfactory event-related potentials.

The purpose of this study was to investigate the influence of the hedonic properties of odors and the attention of subjects on components of the olfactory event-related potentials (OERP). The subjects were seven healthy male students. Two odors (orange and eugenol) of different hedonic properties were presented to the subjects via a constant-flow olfactometer during an oddball paradigm under ignore and attend conditions, and the OERP were then established. The latencies of the OERP were not affected by the qualitatively different odors, whereas the amplitude of late positive component (P3) during the presentation of orange was significantly larger than that during the presentation of eugenol. On the other hand, the allocation of a subject's attention led to a decrease in the latency and to an increase in the amplitude of P3. Moreover, the amplitude of P3 increased significantly when the pleasant odor (orange) in the rare stimulus was presented under the attend condition. These results suggested that hedonic property, distribution of attention, and the interaction between these factors may influence the OERP components.

Effects of inhalation of essential oils on EEG activity and sensory evaluation.

The purpose of this study was to investigate EEG changes in subjects directly after inhalation of essential oils, and subsequently, to observe any effect on subjective evaluations. EEG and sensory evaluation were assessed in 13 healthy female subjects in four odor conditions. Four odor conditions (including lavender, chamomile, sandalwood and eugenol) were applied respectively for each subject in the experiment. The results were as follows. 1) Four basic factors were extracted from 22 adjective pairs by factor analysis of the sensory evaluation. The first factor was "comfortable feeling", the second "cheerful feeling", the third "natural feeling" and the fourth "feminine feeling". In the score of the first factor (comfortable feeling), the odors in order of high contribution are lavender, eugenol, chamomile and sandalwood. 2) Alpha 1 (8-10 Hz) of EEG at parietal and posterior temporal regions significantly decreased soon after the onset of inhalation of lavender oil (p < 0.01). Significant changes of alpha 1 were also observed after inhalation of eugenol or chamomile. The change after inhalation of sandalwood was not significant. These results showed that alpha 1 activity significantly decreased under odor conditions in which subjects felt comfortable, and showed no significant change under odor conditions in which subjects felt uncomfortable. These results suggest a possible correlation between alpha 1 activity and subjective evaluation.

Development and evaluation of the measurement system for the human shoulder joint based on the 6 DOF kinematic modelling.

Although numerical models on the shoulder complex joint are currently available, many are impractical because of the procedural complexity coupled with limited and mere simple simulations. The present study defined the clavicle-scapula system as the "base of the humerus" in determining the position of proximal head of humerus, rendering conclusive innovation of a six degree of freedom (DOF) shoulder complex joint model. Furthermore, a complete measurement system where evaluation by calibrating the actual values via the use of an electromagnetic tracking device (ETD) was developed based on the innovated model. The special calibration method using optimizing calculation to work out the rotational center of humerus was employed and actually tested if the theoretical consideration was practically available. As a result of accuracy check experiments, the measurement error was defined within 2-3 mm, indicating sufficient accuracy in studies for human movement. Our findings strongly advocate that the benefit of this novel measurement system would contribute to studies related to shoulder movements in physiological anthropology.

The effect of mental loads on muscle tension, blood pressure and blink rate.

Surface electromyogram (EMG), blood pressure (BP), blink rate (BR) and heart rate (HR) were recorded before and during 4 types of mental task. The mental task involved 3 tasks that encompassed the memory (M), visual search (VS) and color-word (CW) tasks besides the control task (CT) of maintaining a similar posture while focusing on a single spot on the computer screen. Except for CW, any voluntary movement for response to visual stimuli given were not demanded. Slightly but significant increases in integrated EMG (iEMG) were shown in terapezius, biceps and gastrocnemius muscles during tasks except for CT. Especially in the trapezius muscle during M, the most remarkable enhancements of iEMG and BP were shown. In VS and CW tasks, significant decreases in BR were observed, although in M and CT tasks there were no significant changes in it. There were no significant changes in HR in any type of tasks. The present study demonstrated the increase in muscle tension due to mental needs of cognitive tasks per se accompanying changes in BP and BR. And, enhancement of these physiological responses by memory loads and eyeball movement was discussed as a possible mechanism.

Automatic control of a robot camera for broadcasting based on cameramen's techniques and subjective evaluation and analysis of reproduced images.

With the goal of achieving an intelligent robot camera system that can take dynamic images automatically through humanlike, natural camera work, we analyzed how images were shot, subjectively evaluated reproduced images, and examined effects of camerawork, using camera control technique as a parameter. It was found that (1) A high evaluation is obtained when human-based data are used for the position adjusting velocity curve of the target; (2) Evaluation scores are relatively high for images taken with feedback-feedforward camera control method for target movement in one direction; (3) Keeping the target within the image area using the control method that imitates human camera handling becomes increasingly difficult when the target changes both direction and velocity and becomes bigger and faster, and (4) The mechanical feedback method can cope with rapid changes in the target's direction and velocity, constantly keeping the target within the image area, though the viewer finds the image rather mechanical as opposed to humanlike.

Comparison of predictive value for colorectal cancer in subjects with and without rectal bleeding.

BACKGROUND/AIMS: To clarify the association between a sign of rectal bleeding and colorectal cancer, and to reveal the relationship of rectal bleeding to the results of an immunochemical fecal occult blood test. METHODOLOGY: In a population-based cross sectional study, 30,138 subjects who received immunochemical fecal occult blood screening with a 2-day method were divided into two groups, according to the results of a questionnaire on a sign of rectal bleeding, and the positivity rate of an immunochemical occult blood test as well as the predictive value for colorectal cancer were compared in the two groups. RESULTS: The fecal occult blood test was positive in 8.8% of subjects with rectal bleeding and in 6.0% of subjects without rectal bleeding, and the predictive value was 6.4% and 3.3% in subjects with and without rectal bleeding, respectively, showing a significant difference in the positivity rate (p<0.001) as well as the predictive value (p<0.05) between these two groups. CONCLUSIONS: These findings indicate that there are positive relations between the subjects with rectal bleeding presentation and colorectal cancer, and a sign of rectal bleeding and the results of an immunochemical fecal occult blood test.

Evaluation and design of a small portable EMG amplifier with potential RMS output.

The present study attempted to design and evaluate a small portable electromyogram (EMG) amplifier that can output enhanced EMG and its root mean square (RMS) value. The production and design were of a laboratory scale without any special or high cost circuit construction. The designed amplifier was actually innovated according to the actual working conditions based on physiological anthropology. The present amplifier was compared with commercially available products and proved to be of practical use. The device was installed with a sufficiently small body depicting 8-channel variable gain AC amplifier and variable time-window RMS-to-DC converter. The prototype was battery-driven and well-shielded to minimize external noise interference.

Estimation of thermal sensation during varied air temperature conditions.

Seven male students were exposed to four varied air temperature environments: hot (37 degrees C) to neutral (27 degrees C) (HN), neutral to hot (NH), cool (17 degrees C) to neutral (CN), and neutral to cool (NC). The air temperature was maintained at the first condition for 20 min, then was changed to the second condition after 15 min and was held there for 20 min. Each subject wore a T-shirt, briefs, trunks, and socks. Each sat on a chair and was continuously evaluated for thermal sensation, thermal comfort, and air velocity sensation. Some physiological and thermal parameters were also measured every 5 s during the experiment. The correlation between thermal sensation and skin temperature at 15 sites was found to be poor. The subjects felt much warmer during the rising phase of the air temperature (CN, NH) than during the descending phase (HN, NC) at a given mean skin temperature. However, thermal sensation at the same heat flux or at the same value of the difference between skin and air temperature (delta(Tsk - Ta)) was not so different among the four experimental conditions, and the correlation between thermal sensation and heat flux or delta(Tsk - Ta) was fairly good. The multiple regression equation of the thermal sensation (TS) on 15 sites of skin temperature (Tsk; degrees C) was calculated and the coefficient of determination (R*2) was found to be 0.656. Higher coefficients of determination were found in the equations of thermal sensation for the heat flux (H; kcal.m-2.h-1) at the right and left thighs of the subjects and on delta(Tsk - Ta) (degrees C) at 4 sites. They were as follows: TS = 2.04 - 0.016 Hright - 0.036 Hleft; R*2 = 0.717, TS = 1.649 + 0.013 delta(Tsk - Ta)UpperArm - 0.036 delta(Tsk - Ta)Chest - 0.223 delta(Tsk - Ta)Thigh-0.083 delta(Tsk - Ta)LowerLeg; R*2 = 0.752, respectively.

Control of circadian variation in skin blood flow response to heat stress.

Six male subjects had their lower legs immersed in water at 42 degrees C for 60 min at 4 different times of the day to study whether the skin blood flow response to passive heat stress shows circadian variation in the relationship between skin blood flow and local sweating rate. When skin blood flow was plotted against local sweating rate, three distinct phases were observed. Phase A, an increase in skin blood flow without sweating was maximal at night. But the slope of the regression line did not change over the day in Phase C. These findings suggest that there is circadian variation in the skin blood flow response before onset of sweating during passive heat stress. This variation might be related, in part, to the circadian rhythm in vasoconstrictor activity.

Circadian variation of sweating responses to passive heat stress.

The aim of present study was to examine whether sweating responses to passive heat stress change with the circadian rhythm of internal temperature. Six men had their legs immersed in water at 42 degrees C for 60 min in an ambient temperature of 28 degrees C on four separate days. Experiments were conducted at four different times [06.00 h (morning), 12.00 h (daytime), 18.00 h (evening) and 24.00 h (night)]. We measured oesophageal temperature (Toes), mean body temperature (Tb), local sweating rate (msw) on the forehead, back, forearm and thigh, the densities of activated sweat gland (ASG) on the back, forearm and thigh, and the frequency of sweat expulsion per minute (Fsw) which has been suggested to represent central sudomotor activity. Sweat gland output (SGO) on each site was calculated by dividing msw by ASG. ASG was significantly higher on the forearm than on the back and thigh, and SGO was significantly lower on the forearm than on the back and thigh. However, ASG and SGO did not significantly change over the day. Tb and Toes thresholds for the onset of sweating showed a significant change with both the temperature rhythms at rest prior to each procedure, while the slopes of the relationships Fsw-Tb and msw-Fsw showed no significant difference over the day. We suggest that the circadian variation of sweating response to passive heat stress is regulated by a central sudomotor mechanism rather than by sweat gland function.

Circadian variation in skin blood flow responses to passive heat stress.

To examine whether there is a circadian variation in skin blood flow response to passive heat stress and maximal skin blood flow, which was measured by local warming to 42 degrees C for 45 min, we studied six men at an ambient temperature of 28 degrees C at four different times of day [0400-0700 (morning), 1000-1300 (daytime), 1600-1900 (evening), and 2200-0100 hours (night)], each time of day being examined on separate days. Heat stress at rest was performed by immersing the legs below the knee in hot water (42 degrees C) for 60 min. The esophageal temperature (Tes) at rest was significantly higher in the evening than in the morning. The maximal skin blood flow (SkBFmax) on both sites, back and forearm, did not show a significant difference among the four times of day. The variation in Tes thresholds for cutaneous vasodilation to heat stress was similar to the circadian rhythm in resting Tes. The relationship of the percentage of SkBFmax (%SkBF) with Tes was significantly lower in the morning than in the evening. The results suggest that the maximal skin blood flow during local warming does not show variation over the day, but the sensitivity of vasodilation to passive heat stress shows a circadian variation.

Basic study on the rectangular numeric keys for touch screen.

The present study was conducted to examine the optimum inter-key spacing of numeric rectangular keys for touch screens. Six male students (22-25 years old) and three female students (21-24 years old) participated in the experiment. Each subject performed the data entry task using rectangular keys of touch devices. These keys were arranged in both horizontal and vertical layouts. The sizes of the rectangular keys in both layouts were 12 x 21 mm and 15 x 39 mm, and each of the inter-key spacing of each key was 0, 3, 6, 12 and 21 mm. The response time with inter-key spacing of 3 mm was significantly faster than with the inter-key spacing of 0, 12 and 21 mm (p < 0.05). Keys of vertical position produced faster response time than that of horizontal position. The subjective ratings showed that the inter-key spacing of 6 mm was significantly better than the inter-key spacing of 0, 3, 12 and 21 mm (p < 0.05).

Fundamental study on the size and inter-key spacing of numeric keys for touch screen.

The purpose of this study was to reveal the optimum size and inter-key spacing of numeric square keys for touch screens. Six male students (22-25 years old) and three female students (21-24 years old) volunteered as subjects for this experiment. Each subject took part in data entry tasks using numeric square keys of touch devices. The sizes of keys were 6, 12, 21, 30 and 39 mm and each the inter-key spacing was 0, 3, 6, 12 and 21 mm. Response times with key sizes of 6 and 12 mm were significantly slower than with key sizes of 21 and 30 mm (p < 0.001). Furthermore, the key size of 6 mm significantly caused more errors than the key sizes of 12, 21, 30 and 39 mm (p < 0.05). The response time with inter-key spacing of 3 mm was significantly faster than with that of 0, 6, 12 and 21 mm (p < 0.001). Inter-key spacing of 0 mm significantly produced more errors than other inter-key spacing. Subjective ratings for inter-key spacing of 3, 6 and 12 mm were significantly better than those of 0 and 21 mm (p < 0.05). These results suggested that the optimum size of numeric square keys for touch screens should be more than 21 mm and optimum inter-key spacing should be from 3 to 6 mm. Optimum key size, however, must be selected with regard to the limitation of screen size.

Effects of cooling portions of the head on human thermoregulatory response.

Seven healthy young male students participated in this study. Each subject sat on a chair in an anteroom at 25 degrees C for 30 min and then entered a climatic chamber, controlled at 40 degrees C and R.H. 50%, and sat on a chair for 90 min. Cooling of frontal portion including the region around the eyes (FC), occipital portion (OC), and temporal portion (TC) began after 50 min of entering. An experiment without head cooling (NC) was also made for the control measurement. Thermal comfort and thermal sensation were improved by head cooling, but response was the same regardless of portion cooled. Although rectal temperature, mean skin temperature and heart rate showed no significant effect due to head cooling, forearm skin blood flow (FBF), sweat rate (SR), and body weight loss (delta Wt) had a tendency to be depressed. FBF in FC and TC decreased during head cooling, but that in OC and NC did not change significantly, while SR in FC was depressed. delta Wt showed total sweating to decrease by FC and TC, and FC to have greater inhibitory effect on sweating than OC. Thermal strain was evaluated by the modified Craig Index (I(s)). I(s) in FC decreased significantly more than in NC. Cooling of other portions of the head had no significant effect on I(s). Cooling of the frontal portion of the head may thus be concluded to have the most effect on thermoregulatory response in a hot environment.

Characteristics of Roman character input in Japanese word processing on keystroke interval time.

This study clarifies the characteristics of the time keys that are taken to enter Roman letters for Japanese sentences. First, test the appearance frequency of two consecutive characters of the alphabet in the input of English sentences and in the input of the Roman characters of Japanese sentences. Based on these results, we analyzed the features of stroke frequency of the keys in the Roman character input. Based on the result of the analysis, we clarified the features of the keystroke interval time for two consecutive characters in the Roman character input. Then, keys were struck to enter Japanese sentences for a fixed period of time and a test was made for the characteristics. As a result, the following points were clarified: 1) The time keys struck were divided into two large groups. One for two consecutive alphabet letters that corresponded to Kana, or the Japanese syllabary, and the other with no correspondence. The former had smaller values for the mean time and deviations, and the latter had larger values for them. 2) The subjects who struck a larger number of keys per unit time took less time in typing two consecutive letters which did not correspond to Kana.