[The Analysis of Microcavity-Integrated Graphene Photodetector's SNR Based on 1.06 µm].

Avalanche photodiode is widely used in laser rangefinder due to high gain characteristics, but introduces highly additive noise during the time of current's multiplication that makes laser rangefinder's SNR meet bottleneck. This paper proposes a method of designing a high SNR's graphene photodetector based on microcavity. The graphene's unique optoelectronic properties make it an ideal platform for a variety of photonic applications, such as fast lasers, optical modulators, transparent electrodes, and ultrafast photodetectors. It has been recognized internationally to have dominant advantages in photodetectors due to its high carrier mobility, gapless spectrum, and frequency-independent absorption coefficient. With the wavelength of 1.06 µm, the mechanism of light waves' transmission in the cavity and the graphehne's absorption are studied by using optical transmission matrix method and scattering matrix method; the light absorption model of the graphene photodetector based on microcavity is established. Device's final quantum efficiency reaches 91.2%, respectively reaches 0.778 A·W(-1), its full width at half maximum (FWHM) reaches 6 nm; the influence between graphene's position in the microcavity and device's absorption shows that device's absorption's peak value changes periodically with graphene's position under resonant condition, and the variety of length of microcavity does not have any influence on the peak value, but changes the graphene's position when absorption reaches peak value, on the condition that the length of microcavity is n times of half of wavelength, the number of device's absorption peak value is 2n with the variety of graphene's position, and all the peak values are symmetrical with respect to the center of microcavity, the final graphene's position is 0.402 8 mm away from the top mirror of microcavity, and the absorption reaches 94%, Compared with single layer graphene, the absorption rate increases 16 dB; By solving SNR equation of the graphene photodetector based on microcavity and SNR equation of the avalanche photodiode, eventually finds that the SNR of the graphene photodetector based on microcavity is 90.3, which raises 10 dB compared with the avalanche photodiode's. Theoretical analysis shows the graphene photodetector based on microcavity has high absorption rate, high quantum efficiency, and high SNR. In this paper, the research achievements provide a theoretical reference to update and design higher SNR photodetector used in laser rangefinder's receiving system.

[NR2B-pERK1/2-pElk-1 signaling contributes to the avoidance learning and memory of rats].

AIM: To investigate whether NR2B-pERK1/2-pElk-1 signaling contributes to the Y-maze learning and memory of rat brain. METHODS: 45 adult male SD rats were divided into 4 groups: (1) Ifenprodil peritoneal injection group (Ifenprodil ip, n = 14); (2) DMSO peritoneal injection group(DMSO ip, n = 15); (3) Ifenprodil cerebral ventricle injection group (Ifenprodil ic, n = 8); (4) DMSO cerebral ventricle injection group(DMSO ic, n = 8). Y-maze training and test were used as an learning and memory enhancing stimulus. Immunohistochemical and Western blotting methods were used for detecting pERK1/2 and pElk-1 expression intensity of different brain regions. RESULTS: Compared with the DMSO ip group, the ifenprodil ip group showed no change on the Y-maze learning score (P > 0.05), but its Y-maze memory score tested 24 after learning decreased (P < 0.05). Ifenprodil peritoneal injection made brain pERK1/2 and pElk-1 expression decreased generally. In hippocampus, marginal division of striatum(MrD), amygdala,these changes were more significant (P < 0.05). Compared with the DMSO ic group, the reconsolidation of Y-maze memory tested 6 hours after ifenprodil injection was impaired in ifenprodil ic group (P < 0.05). The OD value of pERK1/2 and pElk-1 positive bands in ifenprodil ic group attenuated generally. The pElk-1 positive bands of caudate putamen and MrD almost disappeared in ifenprodil ic group. CONCLUSION: NR2B is essential for the formation of long-term memory, reconsolidation of Y-maze memory. The deactivation of NR2B by ifenprodil will impair these courses. Meanwhile, the deactivation of NR2B attenuates pERK1/2 and pElk-1 expression of learning and memory related regions after Y-maze learning and memory reconsolidation test. In MrD and caudate putamen, the pElk-1 expression are completely blocked by ifenprodil after memory reconsolidation test.

[Diagnosis and treatment of neonatal inspiratory dyspnea].

OBJECTIVE: To analyze the causes and the clinical characteristics of the neonatal inspiratory dyspnea; so to raise the diagnosis and cure rate of the disease. METHODS: Eleven new born infants with severe inspiratory dyspnea were investigated from March, 2001 to June, 2004 in Shenzhen children's hospital. Six infants were male and 5 were female. The average age was 7.2 days ( range from 8 hours to 28 days). Four cases were hospitalized with trachea intubation. Three of them can not cry, and 2 cases were diagnosed as bilateral vocal cord paralysis, 1 case as multiple cranial nerve palsy with direct laryngoscopy. Two cases couldn't drink milk continuously and accompanied with deteriorated inspiratory dyspnea, and were diagnosed as congenital adenoid hypertrophy and neonatal rhinitis respectively with compute tomography and magnetic resonance imaging. Among the 6 cases with persistent inspiratory dyspnea, four of them were diagnosed as congenital laryngocele by direct laryngoscope, one case was diagnosed as subglottic stenosis by tracheoscopy and one case was confirmed to be thoracic tracheostenosis when tracheotomy performed. RESULTS: Four congenital laryngoceles and one case congenital adenoid hypertrophy were cured with surgery. Two bilateral vocal cord paralysies and one case of subglottic stenosis received tracheotomy. One neonatal rhinitis case applied 0.25% ephedrine. One case of thoracal tracheostenosis died. The parents of the infant with multiple cranial nerve palsy refused to accept any treatment. CONCLUSIONS: The laryngoscope examination is recommended for patients with neonatal inspiratory dyspnea. It is necessary for patients with persistent dyspnea to be examined by tracheoscopy as early as possible.