[Analysis on clinical characteristics of 13 extremely severe burn patients complicated with severe inhalation injury in August 2nd Kunshan factory aluminum dust explosion accident].

Objective: To investigate the clinical characteristics of extremely severe burn patients complicated with severe inhalation injury caused by dust explosion. Methods: The medical records of 13 extremely severe burn patients complicated with severe inhalation injury in August 2nd Kunshan factory aluminum dust explosion accident, who were admitted to the First Affiliated Hospital of Soochow University on August 2nd, 2014, were retrospectively analyzed. The following indicators were collected: (1) Acute Physiology and Chronic Health Evaluation Ⅱ (APACHE Ⅱ) score and Sequential Organ Failure Assessment (SOFA) score at post admission hour (PAH) 24. (2) Prognosis, death time, causes of death, and the mortality of patients with different sexes. (3) The number of times of airway electronic bronchoscopy, airway characteristics, and the corresponding onset time. (4) The number and result of microorganism culture of lesion tissue during the leukoplakia formation stage. Detection of Pseudomonas aeruginosa in patients with and without leukoplakia in airway mucosa. Fisher's exact probability test was used to detect the mortality of patients with different sexes. Kappa test was used to detect the relevancy between leukoplakia and Pseudomonas aeruginosa. Results: (1) The APACHE Ⅱ score of patients of this group at PAH 24 was (19±3) points, and the SOFA score was (12±3) points. (2) Eight patients survived, while 5 patients died, and the time of death was 19-46 (34±10) d after injury. The main cause of death was multiple organ dysfunction syndrome, which was secondary to severe infection. One of the 7 male patients and 4 of the 6 female patients died, but there was no significantly statistical difference in mortality between patients of the two sexes (P>0.05). (3) Airway electronic bronchoscopy was performed 4-25 (10±5) times among patients of this group. Hyperemia and edema were found in the airway mucosa of all the 13 patients 2-3 weeks after injury; ulcer was found in the airway mucosa of 5 patients 2-4 weeks after injury; leukoplakia was found in the airway mucosa of 7 patients 4-14 weeks after injury; granulation formed in the airway mucosa of 7 patients 10-15 weeks after injury, and airway patency was affected, which was solved after local clamping or replacement of lengthened tracheal cannula. (4) During the leukoplakia formation stage, 19 cases of microorganism culture were performed basing on airway lesion tissue, and the results were 15 cases of Pseudomonas aeruginosa, 5 cases of Acinetobacter baumannii, 2 cases of Serratia marcescens, as well as 1 case of Stenotrophomonas maltophilia, Burkholderia cepacia, and Proteus mirabilis each. Among 7 patients with airway mucosa leukoplakia, 6 patients were detected with Pseudomonas aeruginosa. Among 6 patients without airway mucosa leukoplakia, 1 patient was detected with Pseudomonas aeruginosa. The appearance of leukoplakia was consistent with the detection of Pseudomonas aeruginosa (Kappa=0.69, P<0.05). Conclusions: Most of these extremely severe burn patients complicated with severe inhalation injury caused by dust explosion survived, and there was no significant gender difference in mortality. Electronic bronchoscopy showed that the early manifestations of airway mucosa were hyperemia and edema, followed by varying degrees of erosion, ulcer, leukoplakia, and granulation formation, etc. Leukoplakia may be relevant to Pseudomonas aeruginosa infection.

Performance of InGaN based green laser diodes improved by using an asymmetric InGaN/InGaN multi-quantum well active region.

Series of green laser diodes (LDs) with different (In)GaN barrier layers are investigated. It is found that the optical confinement factor of multi-quantum well (MQW) always increases with increasing indium content of InGaN barrier layer, which results in a decrease of threshold current when indium content of InGaN barrier layer increases from 0 to 5%. However, when a high In content InGaN barrier is used (> 5%), both threshold current and slop efficiency of LDs deteriorate. It may be attributed to the waste of carriers in the potential well at the interface between the last barrier (LB) and the upper waveguide (UWG) layers, which is induced by the piezoelectric polarization effect in high In content InGaN LB layer. Therefore, a new LD structure using a thin thickness of the LB layer to reduce the effect of polarization shows a low threshold current and a high output power even when the In content of barrier layers is as large as 7%.

Evolution of differential efficiency in blue InGaN laser diodes before and after a lasing threshold.

The optical power emitting from the cavity facet of blue InGaN-based laser diodes (LDs) is measured to investigate the efficiency droop. The efficiency droop behavior of blue InGaN-based LDs near the threshold is confirmed in our experiments. From measurements of optical power at different wavelengths, it is analyzed that the droop behavior of LDs can be ascribed to the efficiency reduction of longer wavelengths. The efficiency of longer wavelengths is subject to the carrier occupation process in quantum levels. In addition, it is found that the droop behavior may be largely affected by the relatively large threshold current of InGaN-based LDs and the screening effect of polarization, and it can be suppressed by stimulated emission.

Investigation on the corrosive effect of NH3 during InGaN/GaN multi-quantum well growth in light emitting diodes.

Three series of samples with different NH3 flow rate are grown and the optical and structural properties are investigated. It is found that apart from a positive effect on keeping a high partial pressure of nitrogen to enhance indium incorporation, NH3 may also play a negative effect on indium incorporation during InGaN growth. Especially, when temperature is relatively high, the hydrogen generated from the dissociation of NH3 may suppress the chemical reaction which produces InN, leading to a reduced indium incorporation efficiency during the InGaN layer growth.

Emission efficiency enhanced by reducing the concentration of residual carbon impurities in InGaN/GaN multiple quantum well light emitting diodes.

A series of samples with varying growth pressure are grown and their optical and structural properties are investigated. It is found that the residual carbon concentration decreases when the reactor pressure increases from 80 to 450 Torr during the InGaN/GaN multiple quantum well growth. It results in an enhanced peak intensity of electroluminescence because carbon impurities can induce deep energy levels and act as non-radiative recombination centers in InGaN layers.

[Prognostic significance of serum procalcitonin in patients with extremely severe burn and sepsis].

OBJECTIVE: To analyze the changes in serum procalcitonin (PCT) in patients with extremely severe burn and sepsis, and to evaluate its clinical significance in the prognosis of patients. METHODS: Thirteen patients with extremely severe burn and sepsis injured in the aluminum dust explosion accident, which occurred in Kunshan of Jiangsu province, were admitted to our unit on August 2nd, 2014. They were involved in this retrospective study and divided into death group (n=5) and survival group (n=8) according to the outcome. Acute Physiology and Chronic Health Evaluation (APACHE) Ⅱ score and Sequential Organ Failure Assessment (SOFA) score at post admission hour (PAH) 24 were compared among the patients between two groups. Serum level of PCT, serum level of C-reactive protein (CRP), white cell count, neutrophils, platelet count, level of aspartate transaminase (AST), level of prealbumin (PA), level of creatinine, level of urea nitrogen, and level of blood sodium were compared among the patients between two groups in post admission week (PAW) 1, 2, 3, and 4. Data were processed with Fisher's exact test, analysis of variance for repeated measurement, t test, and Mann-Whitney test. Receiver operating characteristic (ROC) curves of serum PCT values were plotted to evaluate the predictive value for death of 13 patients in PAW 3 and 4. RESULTS: The differences in APACHE Ⅱ score and SOFA score at PAH 24 and serum level of CRP, white cell count, level of AST, level of creatinine, level of urea nitrogen, and level of blood sodium from PAW 1 to 4 of the patients between two groups were not statistically significant (with t values from -1.164 to 0.587, Z values from -1.872 to -0.442, P values above 0.05). The serum levels of PCT in patients of death group in PAW 3 and 4 were respectively (15.8±14.9) and (13.6±5.6) ng/mL, which were significantly higher than those of survival group [(2.4±1.8) and (4.9±6.1) ng/mL, with Z values respectively -2.635 and -2.208, P<0.05 or P<0.01]. The serum levels of PCT of patients in death group and survival group in PAW 1 and 2 were close (with Z values respectively -0.732 and -1.025, P values above 0.05). Compared with those of survival group, neutrophils in PAW 4 was significantly increased (t=-3.690, P<0.01), the platelet count in PAW 4 was significantly decreased (t=4.858, P<0.01), and the level of PA in PAW 2 was significantly increased in patients of death group (t=-2.320, P<0.05). There were no statistically significant differences in neutrophils, platelet count, and the level of PA at the other time points of patients between death group and survival group (with t values from -1.562 to 1.904, P values above 0.05). The total areas under ROC curves of serum level of PCT for predicting death of 13 patients with extremely severe burn and sepsis in PAW 3 and 4 were respectively 0.938 and 0.906, and 7.45 ng/mL and 8.77 ng/mL were respectively chosen as the optimal threshold values, with sensitivity of 75.0% and 100.0% and specificity of 100.0% and 87.5%. CONCLUSIONS: Serum level of PCT in PAW 3 and 4 can be used as the vital prognostic indicators for patients with extremely severe burn and sepsis, and it can be considered as a guide for rational treatment in clinic.

Differential resistance of GaN-based laser diodes with and without polarization effect.

In this paper, we used numerical calculation and simulation to investigate the differential resistance of GaN-based laser diodes (LDs) with and without polarization effect. We confirmed the existence of a kink at the vicinity of threshold current in the differential resistance curve of GaN-based LDs and found that the kink polarity can be reversed dependent on the polarization effect. The serial parasitic diodes should be included in the theoretical analysis of the equivalent circuit of the LD devices. We determined that the superposition effects of the n-side, active, and p-side regions of the LDs caused the kink and its polarity. We also found that the differential resistance before and after the threshold was dominated by the p-side region and its gradual reduction is related to an electron overflow into p-side. Finally, we studied the effects of cavity facet reflectivity on the kink.

Temperature dependence of photoluminescence spectra for green light emission from InGaN/GaN multiple wells.

Three green light emitting InGaN/GaN multiple quantum well (MQW) structures with different In composition grown by metal-organic chemical vapor deposition are investigated by the X-ray diffraction and the temperature-dependent photoluminescence (PL) measurements. It is found that when the In composition increases in the InGaN/GaN MQWs, the PL spectral bandwidth may anomalously decrease with increasing temperature. The reduction of PL spectral bandwidth may be ascribed to the enhanced non-radiative recombination process which may lower the light emission efficiency of the localized luminescent centers with shallow localization energy in the high-In-content InGaN quantum wells and also cause a reduction of integrated PL intensity.

Suppression of electron leakage by inserting a thin undoped InGaN layer prior to electron blocking layer in InGaN-based blue-violet laser diodes.

InGaN-based blue-violet laser diodes (LDs) suffer from electron leakage into the p-type regions, which could be only partially alleviated by employing the electron blocking layer (EBL). Here, a thin undoped InGaN interlayer prior to EBL is proposed to create an additional forbidden energy range above the natural conduction band edge, which further suppresses the electron leakage and thus improve the characteristics of LDs. Numerical device simulations reveal that when the proper composition and thickness of InGaN interlayer are chosen, the electron leakage could be efficiently eliminated without inducing any severe accumulation of electrons at the interlayer, resulting in a maximum output power of the device.

Al compositional inhomogeneity of AlGaN epilayer with a high Al composition grown by metal-organic chemical vapour deposition.

The Al compositional distribution of AlGaN is investigated by cathodoluminescence (CL). Monochromatic CL images and CL spectra reveal a lateral Al compositional inhomogeneity, which corresponds to surface hexagonal patterns. Cross-sectional CL images show a relatively uniform Al compositional distribution in the growth direction, indicating columnar growth mode of AlGaN films. In addition, a thin AlGaN layer with lower Al composition is grown on top of the buffer AlN layer near the bottom of the AlGaN epilayer because of the larger lateral mobility of Ga adatoms on the growth surface and their accumulation at the grain boundaries.

Non-exponential photoluminescence decay dynamics of localized carriers in disordered InGaN/GaN quantum wells: the role of localization length.

In this article, we report a combined experimental and theoretical study on the luminescence dynamics of localized carriers in disordered InGaN/GaN quantum wells. The luminescence intensity of localized carriers is found to exhibit an unusual non-exponential decay. Adopting a new model taking the radiative recombination and phonon-assisted hopping transition between different localized states into account, which was recently developed by Rubel et al., the non-exponential decay behavior of the carriers can be quantitatively interpreted. Combining with precise structure characterization, the theoretical simulations show that the localization length of localized carriers is a key parameter governing their luminescence decay dynamics.