Invisible Gateway by Superscattering Effect of Metamaterials.

Illusion devices, such as superscatterer and invisible gateway, have been theoretically studied under the theory of transformation optics and folded geometry transformations. The realization of these devices needs building blocks of metamaterials with negative permittivities and permeabilities. However, superscattering effects, such as stopping wave propagation in an air channel, have not been verified from illusion devices physically because of the challenge of metamaterial design, fabrication, and material loss. In this Letter, we implement a big metamaterial superscatterer, and experimentally demonstrate its superscattering effect at microwave frequencies by field-mapping technology. We confirm that superscattering is originated from the excitation of surface plasmons. Integrated with superscatterer, we experimentally display that an invisible gateway could stop electromagnetic waves in an air channel with a width much larger than the cutoff width of the corresponding rectangular waveguide. Our results provide a first direct observation of superscattering effect of double negative metamaterials and invisible gateway for electromagnetic waves. It builds up an ideal platform for future designs of other illusion devices.

Effects of extremely low frequency magnetic field on anxiety level and spatial memory of adult rats.

BACKGROUND: As the widespread use of electric devices in modern life, human are exposed to extremely low frequency magnetic fields (ELF MF) much more frequently than ever. Over the past decades, a substantial number of epidemiological and experimental studies have demonstrated that ELF MF (50 Hz) exposure is associated with increased risk of various health effects. The present study examined the effects of chronic exposure to ELF MF on anxiety level and spatial memory of adult rats. METHODS: The 50-Hz ELF MF was used during the whole experimental procedures and the value of magnetic field (MF) was set to 2 mT. Adult rats were divided randomly to control, MF 1 hour and MF 4 hours group. Anxiety-related behaviors were examined in the open field test and the elevated plus maze; changes in spatial learning and memory were determined in Morris water maze after 4 weeks of daily exposure. RESULTS: Rats in MF 4 hours group had increased anxiety-like behaviors with unaltered locomotor activity. In the Morris water maze test, rats had reduced latency to find the hidden platform and improved long-term memory of former location of platform without changes in short-term memory and locomotor activity. CONCLUSION: Chronic ELF MF exposure has anxiogenic effect on rats, and the promoting effects on spatial learning and long-term retention of spatial memory.

[A field study on the work load and muscle fatigue at neck-shoulder in female sewing machine operators by using surface electromyography].

OBJECTIVE: To study neck and shoulder work-related muscle fatigue of female sewing machine operators. METHODS: 18 health female sewing machine operators without musculoskeletal disorders work in Beijing garment industry factory as volunteers in participate of this study. The maximal voluntary contraction (MVC) and 20% MVC of bilateral upper trapezium and cervical erectors spinae was tested before sewing operations, then the whole 20 time windows (1 time window = 10 min) sewing machine operations was monitored and the surface electromyography (sEMG) signals simultaneously was recorded after monitoring the 20%MVC was tested. Use amplitude analysis method to reduction recorded EMG signals. RESULTS: During work, the median load for the left cervical erector spinae (LCES), right cervical erector spinae (RCES), left upper trapezium (LUT) and right upper trapezium (RUT) respectively was 6.78 ± 1.05, 6.94 ± 1.12, 5.68 ± 2.56 and 6.47 ± 3.22, work load of right is higher than the left; static load analysis indicated the value of RMS(20%MVC) before work was higher than that value after work, the increase of right CES and UT RMS(20%MVC) was more; the largest 20%MVE of bilateral CES occurred at 20th time window, and that of bilateral UT happened at 16th. CONCLUSIONS: The work load of female sewing machine operators is sustained "static" load, and work load of right neck-shoulder is higher than left, right neck-shoulder muscle is more fatigable and much serious once fatigued.

[Effects of chronic exposure of power frequency magnetic field on neurobehavior in rats].

OBJECTIVE: To observe the effect of chronic exposure to extremely low frequency magnetic field on neurobehavioral of adult rats. METHODS: Fifty Hz sinusoidal extremely low frequency magnetic field (ELF-MF) was used in this experimental procedure and the strength of magnetic field was fixed at 2 mT. Thirty male adult rats were divided randomly into 3 groups: (1) no ELF MF exposure (control group, n=10); (2) exposure to ELF MF 1 h/day (MF1h group, n=10); (3) exposure to ELF MF 4 h/day (MF4h group, n=10). The neurobehavioral changes of rats were detected by the open field test, elevated plus maze test and light/dark box test. RESULTS: Compared with controls, no significant difference was found in rats of MF1h group in any test. Rats in MF4h group showed increased thigmotaxis, more grooming in the open field test; less time spent in open arms, central part and more time spent in closed arms. However, no significant difference was observed in the light/dark test in MF1h or MF4h group. CONCLUSION: Chronic ELF MF exposure has an anxiogenic effect on rats, which is dependent on the daily exposure duration.

Effect of energy compound on skeletal muscle strain injury and regeneration in rats.

This study was designed to determine whether the supplement of energy compound could attenuate strain-induced damage to skeletal muscle in rats. Energy compound is a saline mixture of the following ingredients: ATP (10mg), Coenzyme-A (50 units), Coenzyme-Q(10) (50mg), Cytochrome C (30 mg) and Vitamin B(6) (50mg). Experimental animals were injured in right gastrocnemius muscles by a strain injury model. Energy compound groups were given energy compound 10 ml/kg body weight per day since injured, while saline groups were given saline at the same dose. And a sham operation was performed on the right hindlimb of control group. Plasma was centrifuged to measure lactate dehydrogenase (LDH), lactic acid (La) and creatine kinase (CK) on 3, 7 and 14 d post injury. Muscles were removed and fixed for histology observation and immunohistochemistry assay of desmin and vimentin. The results showed a similar tendency of plasma CK, La and LDH in saline and energy compound groups, while the lower level was found in the energy-compound group. The histological examination of muscle sections revealed a lower degree of damage in the energy compound group in which the expression levels of desmin and vimentin were higher than in the saline group. It is suggested that energy compound supplement may attenuate strain-induced muscle damage and facilitate its regeneration.

Chronic exposure to low-intensity magnetic field improves acquisition and maintenance of memory.

Although past research has suggested that acute exposure to extremely low-frequency magnetic field (ELF MF) impairs learning and memory function, data on chronic exposure remain scarce. In this study, we examined the changes in spatial learning and memory by the Morris water maze test after 4 weeks of daily exposure of rats to a 50-Hz magnetic field of 2 mT for either 1 or 4 h. We found that chronic exposure to ELF MF reduced the latency to find the hidden platform and improved long-term memory of former location of platform without affecting the short-term memory and motor activity. These findings for the first time indicate that chronic exposure to ELF MF exerts a positive effect on the acquisition and maintenance of spatial memory.

Anxiogenic effect of chronic exposure to extremely low frequency magnetic field in adult rats.

Previous study has suggested some relations between extremely low frequency magnetic field (ELF MF) and the emotional state of human beings and animals. The aim of the present study was to investigate whether the anxiety level could be affected by repeated ELF MF exposure of different daily durations. Adult SD rats were submitted to no exposure, MF exposure 1h/day or 4h/day for 25 days. Anxiety-related behaviors were examined in the open field test (OFT), the elevated plus maze (EPM), and light/dark box on the 21th, 23th and 25th exposure day, respectively. Results demonstrated that MF exposure 4h/day increased the anxiety-like behaviors in rats in the open field test and the elevated plus maze test, without altering their locomotor activity, but had no effect in the light/dark box test. Moreover, MF exposure 1h/day had no effect in any test. These findings indicate that chronic ELF MF exposure has anxiogenic effect in rats, which is dependent on the daily exposure duration and it is more sensitive to void space than to strong light.

[Changes of nitric oxide and nitric-oxide synthase in the development of cold-induced hypertension].

OBJECTIVE: To study the changes of nitric oxide(NO) and nitric-oxide synthase(NOS) in the development of cold-induced hypertension (CIH). METHODS: Sixty male Sprague-Dawley adult rats were used. Thirty were exposed to cold (4 +/- 1) degrees C as cold-treated group while the other 30 were at (25 +/- 1) degrees C as controls, 4 hours a day for 6 weeks for both groups. Systolic blood pressure (SBP) and heart rate were measured twice every week. Each group was further subdivided into three groups, 10 rats each. A subgroup of the cold-treated and control rats were sacrificed at 2, 4 and 6 week. Plasma was saved to measure superoxide dismutase (SOD) and malondiadehycle (MDA), while heart was homogenated to measure NO, NOS. RESULTS: 1 SBP increased during 6 weeks of exposure to cold. From the second week, SBP of cold-treated group [(94.16 +/- 3.81) mm Hg] was significantly greater than that of control group [(88.77 +/- 4.45 mm Hg), P<0.01]. The highest SBP level was achieved at the sixth week [(116.78 +/- 3.79)mm Hg, P<0.01]. 2 Compared to the control group, SOD in cold-treated group decreased significantly from the second week, and maintained throughout the time of exposure to cold (P<0.05). MDA levels did not differ significantly between cold-treated and control groups though it increased mildly during 6 weeks of cold exposure (P>0.05). Heart NOS in cold-treated group decreased significantly from the fourth week to the sixth week. And a mild decrease was observed in heart NO of cold-treated group during 6 weeks of exposure (P>0.05). CONCLUSION: Cold-induced hypertension is induced in rats after repeated exposure to cold. The levels of NOS, NO decrease accordingly to the rise of blood pressure. This indicates that the dysfunction of NO and NOS is involved in the development of CIH.