Metal-cavity quantum-dot lasers with enhanced thermal performance.

We designed, fabricated, and characterized thermal performances of Fabry-Pérot quantum-dot lasers with both metal-coated and conventional dielectric waveguides. With proper design, metals, such as Ag, Au, Cu, and Al can function as a low loss waveguide wall as well as an efficient heat remover. Metal-cavity waveguide lasers showed excellent threshold and characteristic temperature working above 120 °C, while dielectric waveguide lasers ceased operation near 80 °C under the same conditions. The thermal analysis of these lasers showed that metal-cavity lasers have approximately 1.5 times higher thermal conductivity compared with those of the dielectric lasers. We believe that the metal-coating of waveguides and the proper selection of metal efficiently remove the heat from the active region and enable stable lasing operation at high temperature.

Strong tunable slow and fast lights using a gain-clamped semiconductor optical amplifier.

Previously demonstrated slow light is still far from applications, particularly due to the limited bandwidth and control speed. Although semiconductor-based slow light has the high bandwidth and sub-nanosecond control speed, slow light was observed only in the absorption regime with attenuation, while fast light observed in the gain regime with amplification. The large power difference in two regimes makes the use of the optical delay impractical. We report novel slow light in the gain regime, with a high power comparable to that of fast light, utilizing the anomalous gain characteristic in a gain-clamped semiconductor optical amplifier. The slow light is tunable to fast light with the current as the only variable. Additional high speed operation, fast delay control, and wide range of operation wavelength make the present approach practical.

Cow's milk protein-specific T-helper type I/II cytokine responses in infants with necrotizing enterocolitis.

Enteral feeding, in particular with formula feeds, is associated with necrotizing enterocolitis (NEC). In this study, we have examined, in the systemic and mucosal immune compartments, for evidence of bovine milk antigen sensitization in infants with NEC. Eleven newborns with Bell's staging 2-3 NEC [median post-conceptional age 31 wk (range 27-41 wk)], 21 neonatal controls [33 (28-40) wk] and 15 infants undergoing intestinal resection or mucosal biopsy for non-inflammatory conditions [39 (34-42) wk] were studied. Spontaneous and antigen or mitogen elicited interferon-gamma (IFN-gamma) [T-helper type I (Th1)], interleukin (IL)-4 and IL-5 [T-helper type II (Th2)] responses were enumerated using single-cell enzyme-linked immunospot (ELISPOT) assay in peripheral blood (PBMC) or lamina propria mononuclear cells. NEC infants, compared with controls, showed a significant elevation in baseline PBMC cytokine secreting cells, vigorous mitogen responses (20- to 120-fold increase) for IFN-gamma, IL-4 and IL-5 (p < 0.001), strong responses to beta-lactoglobulin (betalg) (IFN-gamma > IL-4/IL-5, p < or = 0.001), and somewhat smaller casein responses. Similarly, in the lamina propria, a small but significant increase in spontaneous cytokine-secreting cells was detected in NEC infants (p < 0.01), with an IFN-gamma/IL-4 predominant phytohemagglutinin (PHA)/concanavalin-A (ConA) response. Three of nine NEC infants (but no controls) also showed a positive ELISPOT response to betalg (IFN-gamma only) but none to casein. We have thus demonstrated significant cow's milk protein (CMP) sensitization in NEC, at least in the systemic compartment (mixed Th1/Th2), with minimal mucosal activation in some cases. These novel findings provide a potential mechanism for a direct contributory role of CMP in the pathogenesis of NEC.

Electrically tunable slow and fast lights in a quantum-dot semiconductor optical amplifier near 1.55 microm.

We have demonstrated both slow light in the absorption regime and fast light in the gain regime of a 1.55 microm quantum-dot semiconductor optical amplifier at room temperature. The theory with coherent population oscillations and four-wave mixing effects agrees well with the experimental results. We have observed a larger phase delay at the excited state than that at the ground state transition, likely due to the higher gain and smaller saturation power of the excited state.

Demonstration of mode conversion in an irregular waveguide.

Communications wavelength waveguide mode conversion is demonstrated in an irregular metal-walled structure that was designed by using multiresolution optimization. Strong scatter and a large number of degrees of freedom allowed high-efficiency conversion in a device having a length of just a few wavelengths. The fabrication approach draws on standard semiconductor processing. Mode-selective reflectors, splitters, phase shifters, and other elements can be achieved by using this principle.

A comparison of clinical use of fluticasone propionate and beclomethasone dipropionate in pediatric asthma.

Inhaled steroids play a very important role in the prevention and treatment of asthma. Previous studies indicated that fluticasone propionate (FP) had low bioavailability and high local potency. However, the laboratory data in these studies were not obtained among Taiwan population. It is very important that native data should be established. Thus a 12-week research program was designed, involving 77 patients, 51 for FP group and 26 for beclomethasone dipropionate (BD) group. The objects were victims of moderate to severe asthma and their age ranged from 4 to 14 years old. An open, comparative and randomized method was adopted. Except for the 4-week-later daytime symptom score(P = 0.033, BD group was better), no other significant differences were found between the two groups in the symptom score improvement(P > 0.05). All the P-values for the daytime & night-time scores were lower than 0.001, which means obvious improvement after treatment in both groups. P-value for PEF improvement was 0.003 after 4 weeks (BD group was better) and 0.943 after 8 weeks; for FEV1 improvement, it was 0.005 after 4 weeks(BD group was better) and 0.252 after 8 weeks; and for FEV1/FVC improvements, it was 0.067 after 4 weeks and 0.097 after 8 weeks. There was no statistic significance in total eosinophil count (TEC), IgE, eosinophil cationic protein (ECP) serum level changes after 4 or 8 weeks. Adverse effects were all anticipated and no statistic significance showed up, either, between the two groups or in the cortisol levels (P > 0.05). In conclusion, native data indicated that the potency of 100 micrograms of FP was equal to that of 200 micrograms of BD and that few side effects were noted in FP group. It is recommended that this drug be introduced for clinical use.

Reference ranges for the linear dimensions of the intracranial ventricles in preterm neonates.

AIMS: To establish normal ranges, in preterm infants < 33 weeks' gestation, for measurements of the lateral, third, and fourth ventricles and to assess intra-observer and inter-observer reliability. To assess the effect of head position during scanning on lateral ventricle size. To determine whether sex influences ventricle size. METHODS: A prospective study involving infants < 33 weeks' gestational age (GA) at birth. Cranial ultrasound scans were done during the first 3 days of life. Linear dimensions of the anterior horn width and thalamo-occipital distance of the lateral ventricles, the width of the third ventricle, and the width and length of the fourth ventricle were measured. Measurements were plotted against GA and reference ranges produced. All measurements were tested for intra-observer and inter-observer reliability. Head position and sex differences were studied. RESULTS: 120 infants with known GA (23(+1) to 32(+6) weeks) had their intracranial ventricles measured. Reference ranges obtained were-anterior horn width: 0-2.9 mm; thalamo-occipital distance: 8.7-24.7 mm; third ventricle width: 0-2.6 mm; fourth ventricle width: 3.3-7.4 mm; fourth ventricle length: 2.6-6.9 mm. Dependent and non-dependent lateral ventricles did not differ significantly in size. There was no clinically significant difference in ventricular size between sexes. CONCLUSIONS: Reference ranges for the measurement of the intracranial ventricles in preterm infants from 23 to 33 weeks' GA are provided and can be used in the diagnosis and assessment of ventricular enlargement in preterm infants. All measurements have good intra-observer and inter-observer reliability. Head position at the time of scanning does not influence the asymmetry of the lateral ventricular measurements. The infant's sex does not influence ventricular size.

Why do preterm infants die in the 1990s?

OBJECTIVES: To describe the mortality rate for preterm infants (born 23-36 completed weeks' gestational age) and to determine the causes of death, focusing on avoidable causes. DESIGN AND SETTING: Prospective cohort study of preterm infants born at Royal Women's Hospital, Melbourne (a tertiary referral hospital with a neonatal intensive care unit and a special care nursery) from January 1994 to December 1996. SUBJECTS: 2475 consecutive liveborn infants with gestational ages from 23 to 36 weeks. MAIN OUTCOME MEASURES: Mortality rate during the primary hospitalisation, and causes of death. RESULTS: The total mortality rate was 4.8% (118/2475). The mortality rate declined with increasing maturity. The decrease in mortality was rapid between 23 and 28 weeks' gestational age, from 64.5% at 23 weeks to 4.0% at 28 weeks, then slower, falling to 0.4% at 36 weeks. Fifty of the 118 infants who died had lethal congenital anomalies. Lethal anomalies accounted for three-quarters of deaths in infants aged 28-36 weeks. The mortality rate in infants free of lethal anomalies was 2.8% (68/2425) and only 0.2% (4/1759) for infants aged 32-36 weeks. In the 68 infants without lethal anomalies who died, few obvious preventable causes were identified. CONCLUSIONS: Mortality rates fell rapidly between 23 and 28 weeks' gestational age. Survival rates for preterm infants born after 31 weeks' gestational age approached the survival rates of term infants. Lethal congenital anomalies were the most common cause of death; preventable causes of death were rare.

Changing mortality and causes of death in infants 23-27 weeks' gestational age.

OBJECTIVE: To contrast the mortality rates and changes in the causes of death of very preterm infants (23-27 weeks), before and after the introduction of exogenous surfactant in 1991, and to identify any preventable causes of death remaining in the 1990s. METHODOLOGY: This was a cohort study on consecutive preterm infants of 23-27 weeks' gestational age born in the Royal Women's Hospital, Melbourne, a level III perinatal centre. The infants were livebirths free of lethal anomalies from two distinct eras, 1983-90, and 1992-96, inclusive. The main outcome measures were mortality during the primary hospitalization and the causes of death before and after the introduction of exogenous surfactant in 1991. RESULTS: In 1983-90, 261 of 508 livebirths (51.4%) of 23-27 weeks' gestational age died, a significantly higher proportion than the 109 of 384 (28.4%) livebirths who died in the period 1992-96. The mortality rate fell significantly with increasing gestational age and was lower at each week of gestational age in 1992-96. More infants who died in 1992-96 were treated intensively in the neonatal intensive care unit (NICU). Of the group of infants who died or who were treated intensively in NICU, respiratory causes of death predominated. However, the causes of death changed over time. In 1992-96 proportionally fewer infants died from respiratory causes (1983-90, 82.5%; 1992-96, 60.0%; odds ratio (OR) 0.31, 95%; confidence interval (CI) 0.16-0.57), but more from septic causes (1983-90, 14.3%; 1992-96, 43.8%; OR 4.9, 95%; CI 2.6-9.2). CONCLUSIONS: As the mortality rate has fallen over time, respiratory causes of death have diminished, but septic causes of death have increased. Further advances in the use of exogenous surfactant and respiratory support may reduce respiratory deaths. Effective strategies to reduce nosocomial infections are urgently required.