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Biomedical subjects

J H Wei

Publications and source records attributed to J H Wei.

At least 19 recordsLinked to original sources
PubMed2004

Structure determination of surface magic clusters.

The structure of a type of surface magic cluster is determined by a combination of scanning tunneling microscopy, density-functional calculations, and dynamical low energy electron diffraction. The diffraction method is applicable because these clusters created through hierarchical self-organization of Ga deposited onto a Si(111)-7x7 surface have identical size and structure and form an ordered array with exact translational symmetry. The unprecedented detailed structure information provided by the diffraction measurement is consistent with direct microscopic imaging and theoretical calculations.

Journal Article↗
PubMed2001

The hemispheric difference of semantic processing of Chinese characters in two dimensions as revealed by ERPs.

An experiment was conducted to examine the hemispheric dominance in semantic processing of Chinese characters. Results showed that N1 is the earliest component that reflects the semantic processing of Chinese characters. Although N1 of the left hemisphere is larger in amplitude, that of the right hemisphere is shorter in latency. Based on these findings, the authors propose that the left hemisphere does not start processing until the necessary information has been transferred from the right hemisphere. Once the left hemisphere starts processing, its intensity is stronger. Thus, it is more appropriate to differentiate hemispheric processing dominance into two dimensions: speed and intensity. Moreover, the semantic cognition onset of Chinese characters occurs from 100 ms to 160 ms in the posterior perceptual processing area of brain.

Adult↗
PubMed2001

[Comparison of effects of 5 and 20 Hz magnetic field on cerebral ischemia in rats].

OBJECTIVE: To compare the effects of 5 Hz and 20 Hz magnetic field on cerebral ischemia in rats. METHOD: After cerebral ischemia was produced by ligation of the left general carotid artery, rats were stimulated by magnetic fields of 5 Hz and 20 Hz respectively and pathological changes in neurocytes were observed. RESULT: (1) Different pathological changes were observed in different cells; (2) The extent of damage of pyramidal cells was milder in 5 Hz magnetic field groups than those in the control group, and the effect was not remarkable in the 20 Hz group; (3) The effect on astroglia was worse in 5 Hz group than that in control and 20 Hz group. CONCLUSION: Magnetic field stimulation influences cerebral ischemic reaction with frequency-dependency.

Animals↗
PubMed2001

[Changes of brain potentials related to auditory location discrimination during simulated weightlessness].

Objective. To study changes of brain response in distinguishing auditory location during simulated weightlessness. Method. The event-related potentials (ERPs) during auditory location discrimination were compared between head down tilt (HDT) and head up tilt (HUT) conditions among 14 healthy subjects. Result. (1) Both the target (T) and non-target (NT) auditory signals induced significant ERPS; (2) The slow potential was significantly lower for both T and NT-ERPs during HDT as compared with that during HUT; (3) The reduction of mean slow potential amplitude during HDT was more significant for the target signals from right-rear position and lightest for the target signals from right-front position. This phenomenon was more remarkable at left-front area. Conclusion. These data provide further evidence that the higher brain function was affected by simulated weightlessness.

Aerospace Medicine↗
PubMed2001

[Changes of early components of auditory ERPs during HDT-simulated weightlessness].

Objective. To study changes of early components of the auditory ERPs during simulated weightlessness. Method. The event-related potentials (ERPs) during an auditory location discrimination were compared between head down tilt (HDT) and head up tilt (HUT) conditions in 14 normal subjects. Result. The early components of T-ERPs and NT-ERPs decreased significantly during HDT as compared with that during HUT. The reduction of mean potential amplitude during HDT was more marked at left-forehead area (F5). Conclusion. These data provided further evidence showing that the early activity process of brain was also affected by simulated weightlessness.

Adult↗
PubMed2001

[Research into estimating lumen center of dark region in colon image via cubic B-spline wavelet].

In this paper, a new method is presented to detect the edge of a colonscope image using cublic B-spline wavelet. This method can make up for the shortcoming of traditional method, resulting from blue dark area in colonscope image through estimating the circle centers. These estimated circle centers which have arc-shaped edge lines are weighted to obtained the lumen centers. This center is used to navigate colon endoscope in colonscopic operation.

Algorithms↗
PubMed2001

[Systemic breeding of the new variety of Biantiao ginseng (Panax ginseng)].

OBJECTIVE: To breed new varieties of Biantiao ginseng for high yield and fine quality. METHODS: Systemic breeding methods were applied. About 3,000 outstanding Biantiao ginseng roots were selected and planted in breeding field, and self-crossed for four generations. During the course, inferior lines or plants were rejected. Then strain comparison, identification of resistance to black-speck disease, and analysis of active compositions were carried out. RESULTS: "Biantiao 1" (BT1), the first new variety of Biantiao ginseng, with green stems and thick, long, elegant roots and median resistance to black-speck disease, has been harvested since 20 years. The percentage of Biantiao ginseng roots and yield were 15% and 30% higher than the control's respectively. The content of total ginsenosides and the main monomers was 1.8%-2.5% higher than the control's. The characteristics of overground part and root of BT1 were uniform and stable. CONCLUSIONS: BT1, a new excellent ginseng variety, has a good potential value to be generalized in ginseng production.

Breeding↗
PubMed2000

[EEG synchronization index spectrum: definition, calculation and the changes related to visual selective response].

OBJECTIVE: EEG synchronization is usually estimated in terms of coherence amplitude, but the estimation is with apparent uncertainty because of the poor resolution both in time and frequency. The purpose of this work is to surmount this problem. METHOD: A new definition of EEG synchronization index spectrum [SynI(f)] was developed basing on the distribution characteristics of EEG coherence phase which was calculated by a tested algorithm with 1 s and 1 Hz resolution. The basic feature and its changes during visual selective responses were calculated in 25 normal subjects. EEG signals were recorded from 9 locations in two conditions: looking at the central LED only(VC) and making switch response to the target LED flash signals (T) differentially (DR): switch to left or right for Ts from left (LVF) or right (RVF) visual field, repectively but making no response to the non-target ones (NT). RESULT: (1) The frequency dependency of SynI varied with brain location, e.g., SynI was higher in alpha range than others at frontal locations but the situation reversed at posterior locations. (2) The SynIs between midline and right brain locations were higher than that between mid line and left ones. (3) As compared with VC, SynI was increased in DR condition at central and posterior brain locations but not frontal ones, it happened mainly in 7-23 Hz at central locations but in 1-4 Hz at posterior ones. (4) The augmentation of SynI in DR was greater for T than for NT signals. CONCLUSION: The results indicated that the SynI(f) was meaningful for studying the frequency-spatial feature of EEG synchronization change among brain locations related to cognitive activities.

Aerospace Medicine↗
PubMed2000

Unsymmetrical response features of left and right brain to signals from left and right visual fields at different cognitive levels.

OBJECTIVE: To study the response characteristics of left and right brain to signals from left (LVF) and right (RVF) visual fields during cognitive activity. METHOD: ERPs at 9 locations to LVF and RVF signals were compared in 23 normal subjects in 3 task conditions: looking forward only (VC); making switch response to target signals (T) only (SR); making switch response to T differentially (DR). RESULT: (1) Significant difference in ERPs was found between that induced by LVF and RVF signals on left brain especially at frontal location (F5), which appeared as slow negative deflection induced by T and NT from RVF in SR and DR; (2) Condition-dependent unsymmetrical features between left and right brain were found: the slow potential at F5 was significantly more negative in T and contralateral spatial relation (i. e., left brain for RVF) but more positive in NT and ipsilateral relation than that at F6. CONCLUSION: Signals with psychological meaning in RVF might cause more psychological load as suggested by the results obtained in this study.

Adult↗
PubMed1999

Cross-modal selective attention to visual and auditory stimuli modulates endogenous ERP components.

In two experiments event-related potentials (ERPs) to visual and auditory stimuli were measured in 12 healthy subjects. A cross-modal and delayed response paradigm was used that allows ERPs to be obtained separately to attended and unattended stimuli under conditions in which unattended stimuli are less likely to be covertly or randomly attended. The results showed: (1) N1 enhancement with attention for standard stimuli in auditory and visual modalities and for deviant stimuli in the visual modality; (2) The onset time and scalp distribution of both the N1 for attend condition and Nd1 were similar regardless of standard or deviant stimuli in the auditory and visual modality; the onset time of Nd1 elicited by auditory and visual deviant stimuli was earlier than that of the unattended N1, and their scalp distributions were different; and (3) The Nd1 components elicited by auditory and visual deviant stimuli were distributed over the respective primary sensory areas, but Nd1 components evoked by auditory and visual standard stimuli were distributed over the frontal scalp. These results suggest that the attended N1 enhancement is primarily caused by a component with endogenous origins and that the early attention effect occurs before the exogenous components. The results support the view that the cross-modal attention to deviant stimuli modulates modality-specific processing in the brain, whereas attention to standard stimuli affects modality-nonspecific or supramodal brain systems.

Adult↗
PubMed1999

Effects of semantic discrimination of Chinese words on N400 component of event-related potentials.

20 subjects' event-related brain potentials were measured during a lexical decision task in which Chinese characters were used in both conditions of related (antonym) and unrelated words. Analysis indicated that the mean reaction time for unrelated words was 130 msec. longer than that elicited by related words. The condition of unrelated words elicited a significant N450, and an obvious P500 was evoked by related words at each of the 17 recording sites. Furthermore, the amplitudes of N210 and N450 were larger in the left hemisphere than in the right hemisphere but the amplitude of P500 was larger in the right hemisphere than in the left hemisphere.

Adolescent↗
PubMed1999

[Effect of extremely low frequency magnetic field on brain response to selective mental arithmetic under simulated weightlessness].

Objective. To study effects of extremely low frequency magnetic field (ELMF) on brain function state during weightlessness. Method. The brain event-related potentials (ERPs) during a selective mental arithmetic task were compared in 40 normal subjects (20-25 yrs) before and after ELMF (5 Hz) stimulation during simulated weightlessness (head down tilt -10 degrees, HDT). Result. The amplitude of slow positive potentials which were supposed to be related to the mental arithmetic activity decreased significantly especially in 100 min after HDT, but it did not decrease significantly after ELMF stimulation. Conclusion. ELMF stimulation may improve the brain function state during simulated weightlessness.

Adult↗
PubMed1993

Effects of eye position on event-related potentials during auditory selective attention.

Event-related potentials (ERPs) were recorded from normal subjects who received random sequences of tone pips from loudspeakers located to the left and right of a central point. The task was to detect occasional higher pitched tones (targets) from one designated speaker. The negative difference (Nd) wave between ERPs for relevant and irrelevant tones was largest when subjects fixated on the relevant speaker, smallest when subjects fixated on the irrelevant speaker, and intermediate in a central fixation. In addition, the Nd modulation for the left tones was produced by the more negative (or less positive) shift of irrelevant-stimulus ERPs and the less negative shift of relevant-stimulus ERPs associated with fixating away from the relevant speaker. These findings suggest the possibility of both facilitatory and inhibitory effects of eye position on auditory spatial attention. The substantial modulation of ERPs due to eye position also indicated the necessity of fixation control in auditory attention ERP research.

Adult↗
PubMed1993

Relatively between extrication wave of mental load (EML) and emotion.

This experiment which was divided into three items studied the relativity between normal human emotion and extrication wave of mental load (EML) in a paradigm of combining CNV feedback with EML. Fourteen young persons were taken as subjects. After Fz, Cz, Pz, P3-T5 and P4-T6 were recorded, shorter EML latency and higher EML amplitude were caused by positive emotion in comparison with those caused by negative emotion. EML changes of the five recorded points were consistent under the effects of positive and negative emotions. This experiment also discussed the question of EML brain sources. Under the emotional conditions provided in the present experiment, EML possibly can be regarded as ERP index reflecting its positive and negative attributes.

Acoustic Stimulation↗
PubMed1993

[Effects of ranitidine on ventricular refractory period and fibrillation threshold of normal and ischemic ventricle in rabbits].

Effects of ranitidine (Ran) on ventricular refractory period and fibrillation threshold of normal and ischemic ventricle were investigated in pentobarbitone anesthetized rabbits. In saline-treated rabbits, relative refractory period (RRP) and effective refractory period (ERP) were shortened from 132 +/- 24 to 126 +/- 25 ms (n = 10, P < 0.05) and from 118 +/- 22 to 108 +/- 27 ms (n = 10, P < 0.05) in boundary zone of ventricular ischemic regions, respectively. The ventricular fibrillation threshold (VFT) was decreased from 5.5 +/- 1.4 to 2.8 +/- 1.1 V (n = 10, P < 0.01) after coronary artery ligation (CAL). Ran (25 mg.kg-1, i.v.) not only prevented these changes, but also lengthened RRP from 123 +/- 14 to 136 +/- 10 ms (P < 0.05) and ERP from 111 +/- 16 to 126 +/- 12 ms (P < 0.05), and increased VFT from 4.7 +/- 0.8 to 7.4 +/- 1.8 V (P < 0.01) in normal ventricle. The results suggest that Ran may have anti-arrhythmic effects in rabbits.

Animals↗
PubMed1990

Early afterdepolarization in mouse atrial fibers induced by 3.0 mM K+ and the inhibitory effects of tetrodotoxin and nifedipine.

Early afterdepolarization (EAD) was induced under superfusion of Tyrode solution (K+ = 3.0 mM) at a longer cycle length in mouse atrial fibers. The relationships between the duration and the number of triggered bursts and cycle length were exponential (n = 17). Thus, EAD possesses the property of cycle length dependence. Under a moderate concentration of TTX (4.0 microM) or nifedipine (5.0 microM) treatment, EAD was partially inhibited but maintained cycle length dependence. When a high concentration of the drugs (30 microM and 8.0 microM, respectively) was applied, EAD was abolished at all cycle lengths of driving stimulation. It is suggested that both inward currents (INa and ICa) are involved in the generation of EAD in mouse atrial fibers.

Action Potentials↗
PubMed1989

Effect of simulated weightlessness on the response characteristics of human brain.

In order to systematically investigate the effects of simulated weightlessness on the function state of human brain, 15 degrees head-down tilt (HDT) was used to simulate weightlessness, and the response changes of event-related EEG power spectra, medium-frequency synchronous potentials and slow-waves were examined in the present study. It was found that HDT had characteristic effects on the above EEG responses, suggesting that the effects mainly occurred in the brain's regulatory system, therefore, resulting in changes of the brain function state.

Adolescent↗