Light recycling in LED-pumped Ce:YAG luminescent concentrators.

We report the development of a high-brightness, high-power Ce:YAG luminescent concentrator pumped by 2240 blue LEDs in quasi-continuous wave operation (10 µs, 10  Hz). Using light confinement and recycling in the three space dimensions, the parallelepiped (1mm×14×mm×200mm) Ce:YAG emits a power of 145 W from a square output surface (1 × 1mm2) corresponding to a brightness of 4.6 kW/cm2/sr. This broadband yellow source has a unique combination of luminous flux (7.6 104 lm) and brightness (2.4 104 cd/mm2) and overcomes many other visible incoherent sources by one order of magnitude. This paper also proposes a deep understanding of the performance drop compared to a linear behavior when the pump power increases. Despite excited state absorption was unexpected for this low doped Ce:YAG pumped at a low irradiance level, we demonstrated that it affects the performance by tripling the losses in the concentrator. This effect is particularly important for small output surfaces corresponding to strong light recycling in the concentrator and to average travel distances inside the medium reaching meters.

CPAP Is Not Needed in Every Sleep Apnea Patient Awaiting Bariatric Surgery.

BACKGROUND: Obstructive sleep apnea (OSA) patients are at high risk of postoperative complications following bariatric surgery. The aim of our study was to compare peri- and postoperative outcomes in OSA patients awaiting laparoscopic bariatric surgery who were prescribed CPAP treatment or not before surgery using nocturnal home oximetry and capillary blood gas measurements. METHODS: Data on 1094 eligible patients were analyzed. In accordance with our algorithm, those with ODI < 25/h and pCO2 < 45 mmHg (358 mild/moderate apnea and 447 non-apneic) underwent surgery without previous treatment, whereas those with an ODI ≥ 25/h (n = 289) were prescribed CPAP. We compared peri- and postoperative outcomes in treated and untreated patients. RESULTS: Treated patients were significantly older with a higher body mass index and a higher percentage of men than non-apneic and untreated OSA. Hypertension and diabetes were significantly more prevalent in the treated and untreated OSA patients than in the non-apneic. Regarding the occurrence of cardiopulmonary complications, the incidence of cardiac arrhythmia was higher in the treated patients than in the non-apneic and the untreated OSA (2.4%; 0.6 and 0.5%, p = 0.03). The slightly longer length of hospital stay seen in treated patients compared to those of other groups (2.8 ± 1.7; 2.6 ± 2.1 and 2.6 ± 1.8 days, p = 0.03) was no longer observed after adjusting for age and BMI. CONCLUSIONS: There is no risk increase for complications following bariatric surgery in untreated patients presenting mild/moderate OSA identified by a noninvasive screening algorithm.

Raman chemical imaging for spectroscopic screening and direct quantification of falsified drugs.

Falsified drugs are a threat to the health of patients. The analytical control of such products contributes to the fight against this global issue. Raman chemical imaging is a method that relies on consecutive measurements at the surface of a sample, combining spectroscopy, microscopy and chemometrics. This article explores the capabilities of this analytical technique proposing an innovative methodology with spectroscopic screening for the identification of chemical compounds and the direct quantification of the active substance (without prior calibration). Two chemometric methods were used: Multivariate Curve Analysis - Alternate Least Squares for the qualitative analysis and Direct Classical Least Squares for the quantitative analysis. The methodology was optimized with samples prepared in the laboratory and validation parameters were studied. The methodology was then applied to real (authentic and falsified) samples of Viagra® and Plavix®. Despite the presence of fluorescence emission in some samples, the methodology succeeded in the detection of active pharmaceutical ingredients, and in the discrimination of three salts of clopidogrel (in generic formulations of Plavix®). The quantitative deviation from the reference method ranged from -15% to +24% of the active substance content. This deviation may be considered to be acceptable since it is sufficient for assessing the risk to the health of patients and for quickly alerting the health authorities.