High optical feedback tolerance of InAs/GaAs quantum dot lasers on germanium.

This work experimentally investigates the optical feedback sensitivity of InAs/GaAs quantum dot (Qdot) lasers epitaxially grown on Ge substrate. In comparison with a Qdot laser on GaAs substrate with identical epilayer and cavity structures, the Ge-based laser is found to exhibit lower sensitivity to the optical feedback, although it has a higher epitaxial defect density. Theoretical analysis proves that the high defect density strongly increases the damping factor while slightly reduces the linewidth broadening factor, which lead to high tolerance to the optical feedback. This work suggests the high potential of Qdot lasers on Ge for isolator-free operation in photonic integrated circuits.

miR-202 acts as a potential tumor suppressor in breast cancer.

Breast cancer affects ~10% of women worldwide and is responsible for ~12% of all cancer-associated mortalities. Breast cancer is more prone to metastasis compared with other types of cancer. Up to 5% of patients with breast cancer present with incurable metastasis and an additional 10-15% of patients develop metastases within 3 years of their initial diagnosis. MicroRNAs (miRNAs) are short RNAs, 21-25 nucleotides in length, that have been shown to significantly affect gene expression. In total >2,000 miRNAs have been identified and specific miRNAs have been revealed to be associated with cancer. In the present study, we observed that the majority of breast cancer specimens collected expressed low levels of miR-202 compared with adjacent tissues and normal cell lines. Mechanistic investigations identified KRAS as a potential target gene of miR-202 and it was demonstrated that miR-202 exerted its tumor-suppressive effects by regulating the expression of KRAS in breast cancer cells. Functional assays revealed that miR-202 significantly reduced cell proliferation, migration and invasion in vitro. In summary, these results indicate the function of miR-202 in breast cancer progression and suggest that its use within breast cancer therapy is promising.

Dynamic model and bandwidth characterization of InGaAs/GaAsSb type-II quantum wells PIN photodiodes.

In this work, we demonstrated a normal incident PIN InGaAs/GaAsSb type-II multiple quantum wells (MQW) photodiode on InP substrate for 2 µm wavelength high-speed operation. The photodiode has a responsivity of 0.35 A/W at room temperature at 2 µm, and a 3 dB bandwidth of 3.7 GHz. A carrier dynamic model is developed to study the bandwidth of the multiple quantum wells photodiode. Simulation results match the experimental data well, and analysis shows that hole transport limits the 3 dB bandwidth performance. By optimizing the MQW design, higher bandwidth performance (>10 GHz) can be achieved.

[Analysis of Gene Mutation Types of Thalassemia in Longyan Area of Fujian Province in China].

OBJECTIVE: To explore the type and distribution of thalassemia gene mutation in Longyan area of Fujian province in China, so as to provide a evidence for prenatal diagnosis and to reduce birth defects. METHODS: The mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH) and hemoglobin electrophoresis were used for screened the mutation types of thalassemia. Genotyping of the screened positive sample was performed by gap single polymerase chain reaction (gap-PCR) and reverse dot blot hybridization (RDB). RESULTS: Out of 7823 cases of routine positive blood test, 2826 cases were positive (36.12%) by using hemoglobin electrophoresis; 1905 out of 2710 cases were diagnosed as Mediterranean anemia by genetic test, with 24.35% of carrying rate; 1225 cases were positive alpha thalassaemia and the carrying rate was 15.66%, their major genetic types were --SEA/αα,-α3.7/αα,-α3.7/--SEA and -α4.2/αα, with carrying rate of 12.91%, 1.28%, 0.51% and 0.74%, respectively; 632 cases were positive ß thalassaemia, with carrying rate of 8.08%, the major genotypes were 654M/N,41-42M/N,17M/N,-28M/N and 27-28M/N and with carrying rate of 3.66%, 2.22%, 0.78%, 0.66% and 0.45%, respectively; 48 cases were diagnosed as both α- and ß-thalassemia, with the carrying rate of 0.61%. CONCLUSION: The main gene mutation types of α- and ß-thalassemia in Longyan area of Fujian Province in China were --SEA/aa and 654 M/N. As thalassemia gene mutation prevalents in Fujian, the screening of thalassemia genotypes for childbearing age woman has great significance for raising population quality.

Fluoride or/and aluminum induced toxicity in guinea pig teeth with the low expression of dentine phosphoprotein.

This study investigated the damage and expression of dentine phosphoprotein (DPP) in guinea pig teeth by the administration of fluoride (F) or/and aluminum (Al). Fifty-two guinea pigs were divided randomly into four groups (control, F, Al, and F+Al). F (150 mg NaF/L) or/and Al (300 mg AlCl3 /L) were added in their drinking water for 90 days. The levels of F ion, dentine sialophosphoprotein (DSPP) gene, and DPP protein in incisor and molar were determined, respectively. The results showed that the concentrations of F ion in F and F+Al groups were increased significantly. F induced the mottled enamel and irregular abrasion of teeth, which might occur as a consequence of depressed DSPP mRNA and DPP protein expression. Both the gene and protein expressions showed obvious decrease induced by Al, especially by F. There were no synergistic effects between F and Al, instead, Al inhibited the toxicity of F.

Influence of GaAsBi Matrix on Optical and Structural Properties of InAs Quantum Dots.

InAs/GaAsBi dot-in-well structures were fabricated using gas-source molecular beam epitaxy and investigated for its optical and structural properties. GaAsBi-strained buffer layer and strain reduction layer are both effective to extend the photoluminescence (PL) emission wavelength of InAs quantum dot (QD). In addition, a remarkable PL intensity enhancement is also obtained compared with low-temperature-grown GaAs-capped InAs QD sample. The GaAsBi matrix also preserves the shape of InAs QDs and leads to increase the activation energy for nonradiative recombination process at low temperature. Lower density and larger size of InAs QDs are obtained on the GaAsBi surface compared with the QDs grown on GaAs surface.

Detailed Study of the Influence of InGaAs Matrix on the Strain Reduction in the InAs Dot-In-Well Structure.

InAs/InGaAs dot-in-well (DWELL) structures have been investigated with the systematically varied InGaAs thickness. Both the strained buffer layer (SBL) below the dot layer and the strain-reducing layer (SRL) above the dot layer were found to be responsible for the redshift in photoluminescence (PL) emission of the InAs/InGaAs DWELL structure. A linear followed by a saturation behavior of the emission redshift was observed as a function of the SBL and SRL thickness, respectively. The PL intensity is greatly enhanced by applying both of the SRL and SBL. Finite element analysis simulation and transmission electron microscopy (TEM) measurement were carried out to analyze the strain distribution in the InAs QD and the InGaAs SBL. The results clearly indicate the strain reduction in the QD induced by the SBL, which are likely the main cause for the emission redshift.

Effects of fluoride and aluminum on expressions of StAR and P450scc of related steroidogenesis in guinea pigs' testis.

A lot of studies have shown that fluoride and aluminum have toxic effect on male reproductive system, but the mechanism of which and the interaction between fluoride and aluminum is still unknown. This study investigated the effects of fluoride (NaF) or/and aluminum (AlCl3) on serum testosterone level, gene and protein expression levels of Steroidogenic Acute Regulatory Protein (StAR) and Cytochrome P450 cholesterol side chain cleavage enzyme (P450scc) in the testes of guinea pigs. Fifty-two guinea pigs were divided randomly into four groups (Control, HiF, HiAl and HiF + HiAl). Fluoride (150 mg NaF/L) or/and aluminum (300 mg AlCl3/L) were orally administrated to male guinea pigs for 13 weeks. The results showed that F and Al reduced number and elevated abnormal ratio of sperm. Meanwhile, the concentrations of serum testosterone in all experimental groups were decreased. P450scc protein expression was significantly reduced in all treatment groups, and StAR expression was decreased remarkably in HiF group and HiF + HiAl group. The levels of StAR mRNA in three groups were reduced by 53.9%, 21.4% and 33.4%, respectively, while the expressions of P450scc mRNA were reduced by 67.8%, 17.0% and 47.8%. Therefore, we concluded that F induced the reduction in testosterone and sperm amount, and thus in lower fertility, which might occur as a consequence of depressed StAR and P450scc mRNA expression. There were no synergistic effects between F and Al, instead, Al weakened the toxicity of F to some extents. The results indicated that Al had antagonism effects on F.

Analysis of mode-hop free tuning of folded cavity grating feedback lasers.

We analytically study an external cavity laser structure including a folded cavity. A steering mirror is utilized in the folded cavity to deflect the intracavity laser beam. A mode-hop free tuning range of ∼400 GHz can be achieved by control of the steering mirror, and a fast tuning rate is expected because of the small mass of the steering mirror. This technique has potential for applications in spectroscopy for turbulent media, especially in the mid-infrared region.

Structural and optical characterizations of InPBi thin films grown by molecular beam epitaxy.

InPBi thin films have been grown on InP by gas source molecular beam epitaxy. A maximum Bi composition of 2.4% is determined by Rutherford backscattering spectrometry. X-ray diffraction measurements show good structural quality for Bi composition up to 1.4% and a partially relaxed structure for higher Bi contents. The bandgap was measured by optical absorption, and the bandgap reduction caused by the Bi incorporation was estimated to be about 56 meV/Bi%. Strong and broad photoluminescence signals were observed at room temperature for samples with xBi < 2.4%. The PL peak position varies from 1.4 to 1.9 µm, far below the measured InPBi bandgap.

Effects of dietary protein and calcium on thymus apoptosis induced by fluoride in female rats (Wistar rats).

Our previous studies showed that excessive fluoride (F) ingestion seriously damaged the nonspecific immune function in rabbits. However, the underlying mechanisms of the F-induced damage to the immune system are unclear. The purpose of this study was to investigate whether F induces thymus apoptosis in female rats and its underlying mechanisms by monitoring ultrastructural changes and DNA fragmentation. The results showed that excessive F induced ultrastructural changes and significantly increased the tail length and tailing ratio in thymus lymphocytes. Protein (Pr) supplementation markedly decreased the tailing ratio in thymus lymphocytes in the case of malnutrition. Furthermore, molecular analysis showed that excessive F ingestion significantly up-regulated the expression levels of caspase-3 and caspase-9 mRNA, whereas Pr and calcium (Ca) supplementation down-regulated the expression levels induced by excessive F in the case of malnutrition. In conclusion, these results indicate that excessive F up-regulates the expression levels of caspase-3 and caspase-9 mRNA and induces thymus apoptosis in female rats. Pr and Ca play key roles in process of F-induced thymus apoptosis in malnourished female rats.