Dynamics of Optically-Generated Carriers in Si (100) and Si (111) Substrate-Grown GaAs/AlGaAs Core-Shell Nanowires

GaAs/Al0.1Ga0.9As core-shell nanowires (CSNWs), with average lateral size of 125 nm, were grown on gold nanoparticle-activated Si (100) and Si (111) substrates via molecular beam epitaxy. Room temperature-photoluminescence (RT-PL) from the samples showed bulk-like GaAs and Al0.1Ga0.9As bandgap emission peaks at 1.43 and 1.56 eV, respectively. Higher PL emission intensity of the sample on Si (111) compared to that on Si (100) is attributed to uniform Al0.1Ga0.9As shell passivation of surface states on Si (111)-grown CSNWs. Carrier dynamics in two different temporal regimes were studied. In the sub-nanosecond time scale (300-500 ps), time-resolved radiative recombination efficiency of carriers was examined. In the 0-4 ps range, surface field-driven ballistic transport of carriers was probed in terms of the radiated terahertz (THz) waves. Time-resolved PL measurements at 300 K revealed that the carrier recombination lifetime of the GaAs core on Si (100)-grown CSNWs is 333 ps while that on Si (111)-grown sample is 500 ps. Ultrafast photoexcitation of GaAs core on the two samples generated a negligible difference in the intensity and bandwidth of emitted THz radiation. This result is ascribed to the fact that the deposited GaAs material on both substrates produced samples with comparable NW densities and similar GaAs core average diameter of about 75 nm. The samples' difference in GaAs core's carrier recombination lifetime did not influence THz emission since the two processes involve distinct mechanisms. The THz spectrum of CSNWs grown on Si (111) exhibited Fabry-Perot modes that originated from multiple reflections of THz waves within the Si substrate.

Improving rate of decline of FEV1 in young adults with cystic fibrosis

BACKGROUND

CF is characterised by a progressive decline in lung function; reductions in this decline are often used as a measure of success in clinical trials. With improvements in treatment it may be that there has been a temporal shift in the pattern of the disease.

METHODS

318 patients born in five successive cohorts and attending a specialist clinic with at least two routine measurements of lung function made between the ages of 18 and 22 were included. The declines in their lung function were estimated and compared.

RESULTS

The mean (SE) slopes for percentage predicted forced expiratory volume in 1 second (FEV(1)) and forced vital capacity (FVC) were -1.53 (0.36)% and -1.27 (0.34)%, respectively (NS). The annual deterioration in FEV(1) was -2.49%, -1.99% -2.20%, -1.65%, and -0.65% from the earliest to the most recent birth cohort; a similar pattern was observed for changes in FVC. There were no differences between male and female patients. Patients infected with Pseudomonas had a greater average decline in FEV(1) (-1.6% v -1.1%).

CONCLUSIONS

The rates of decline in lung function in young adults with CF have diminished with successive birth cohorts. This has important implications for the design of clinical studies in this disease.

[Diarrhea during mechanical ventilation]

OBJECTIVE

To identify the causes of diarrhea during mechanical ventilation.

METHODS

We reviewed 56 cases, who have been mechanically ventilated for more than 48 hours, and also received both enteral and parental nutritional support in our RICU.

RESULTS

33 (57%) patients developed ventilator-associated pneumonia. 19 (33%) patients suffered from diarrhea, lasted 13 days on average. Spores with large quantities were found in stools of 8 patients, with hypha in three patients. There was imbalance of bacteria in faeces in 4 cases, manifested by decreases in rods and increases in cocci, in which E. faecalis were present in 3 patients. 9 patients suffered from diarrhea with no evidence rate of abnormalities in their faeces. Diarrhea was treated by adjustment of food temperature and rate of feeding. it is confirmed by Logistic regression that diarrhea during mechanical ventilation was correlated with ventilator associated pneumonia (VAP).

CONCLUSIONS

Diarrhea in mechanical ventilated patients in our RICU were attributed mainly to improper administration of enteral nutrition, disturbances of the microenvironment of the intestines, including fungal infection, imbalance between coccus and rod, even E. faecalis colonization. Limitation of broad-spectrum antibiotics administration, VAP control, and proper administration of formula are strongly recommended.

Pseudo-outer product based fuzzy neural network fingerprint verification system

Fingerprint identification has been used in law enforcement applications over the last century, and has become the de facto international standard for positive identification. With the emergence of automated fingerprint identification technologies, it has assisted in making the once labour-intensive process of classifying, searching and matching a thing of the past. As a biometrics proof of identification, not many have ventured into the world of fingerprint identification using fuzzy neural networks. In this paper, a database of fingerprint images is constructed and a fuzzy neural network called the pseudo outer product fuzzy neural network (POPFNN) [Zhou, R.W. & Quek, C. (1996). A pseudo outer-product based fuzzy neural network. Neural Networks, 9(9), 1569-1581] is trained to detect similarity between two fingerprints and decide whether they belong to the same person. The fundamental idea is that, given a person's fingerprints taken under different conditions, the POPFNN based fingerprint verification system should be sufficiently robust to distinguish the difference. The people providing the fingerprint samples are subjected to different 'adverse' conditions; from wetness to chemical treatments. Fingerprint images are taken after conditions such as: after a shower, holding pineapples (mild acid from fruit), after washing one's hands, etc. The characteristics of POPFNN, such as the learning, generalisation, and high computational abilities, make fingerprint verification particularly powerful when verifying authentic fingerprints subjected to external conditions and recognising spurious ones. In order to demonstrate the efficacy of POPFNN and its application in the fingerprint verification system (FVS), several types of experiments have been designed and implemented in this work. The experimental results and analysis are presented at the end of the paper for discussion.

Expression of TGF-beta 1, PDGF and IGF-1 mRNA in lung of bleomycin-A5-induced pulmonary fibrosis in rats

OBJECTIVE

To investigate the influence of alveolar macrophages (AMs), fibroblasts and interstitial cells on development of lung fibrosis, and the interactions among TGF-beta 1 PDGF and IGF-1 and these cytokines-effects on lung fibrosis.

MATERIAL AND METHODS

Expressions of TGF-beta 1, PDGF and IGF-1 mRNA in the lung cells and lung tissues in different stages of Bleomycin-A5-induced pulmonary fibrosis in rats were studied through Northern hybridization.

RESULTS

The expressions of TGF-beta 1 and PDGF mRNA reached their peaks in AMs of pulmonary fibrosis in rats on the 7th day after Bleomycin-A5 instillation. It was similar with that in the lung tissues. IGF-1 mRNA remained relatively stable in AMs during the course. PDGF and IGF-1 mRNA increased gradually in fibroblasts, and reached the highest expressions in the interstitial cells. There was almost no TGF-beta 1 mRNA expression in all groups of fibroblasts.

CONCLUSIONS

AMs are the main sources of TGF-beta 1 and PDGF in the lung tissues with fibrosis induced by Bleomycin-A5 AMs are activated in the first weekend and secrete TGF-beta 1 and PDGF to promote fibroblasts proliferation and fibrosis. As fibrosis developed, fibroblasts have established PDGF and IGF-1 autocrine and these three cytokines paracrine nets combined with the interstitial cells to promote lung fibrosis.