Commercial and Custom Quartz Tuning Forks for Quartz Enhanced Photoacoustic Spectroscopy: Stability under Humidity Variation.

This work investigates the behavior of commercial and custom Quartz tuning forkss (QTF) under humidity variations. The QTFs were placed inside a humidity chamber and the parameters were studied with a setup to record the resonance frequency and quality factor by resonance tracking. The variations of these parameters that led to a 1% theoretical error on the Quartz Enhanced Photoacoustic Spectroscopy (QEPAS) signal were defined. At a controlled level of humidity, the commercial and custom QTFs present similar results. Therefore, commercial QTFs appear to be a very good candidates for QEPAS as they are also affordable and small. When the humidity increases from 30 to 90 %RH, the variations in the custom QTFs' parameters remain suitable, while commercial QTFs show unpredictable behavior.

Highly Sensitive Capacitive MEMS for Photoacoustic Gas Trace Detection.

An enhanced MEMS capacitive sensor is developed for photoacoustic gas detection. This work attempts to address the lack of the literature regarding integrated and compact silicon-based photoacoustic gas sensors. The proposed mechanical resonator combines the advantages of silicon technology used in MEMS microphones and the high-quality factor, characteristic of quartz tuning fork (QTF). The suggested design focuses on a functional partitioning of the structure to simultaneously enhance the collection of the photoacoustic energy, overcome viscous damping, and provide high nominal capacitance. The sensor is modeled and fabricated using silicon-on-insulator (SOI) wafers. First, an electrical characterization is performed to evaluate the resonator frequency response and nominal capacitance. Then, under photoacoustic excitation and without using an acoustic cavity, the viability and the linearity of the sensor are demonstrated by performing measurements on calibrated concentrations of methane in dry nitrogen. In the first harmonic detection, the limit of detection (LOD) is 104 ppmv (for 1 s integration time), leading to a normalized noise equivalent absorption coefficient (NNEA) of 8.6 ⋅ 10-8 Wcm-1 Hz-1/2, which is better than that of bare Quartz-Enhanced Photoacoustic Spectroscopy (QEPAS), a state-of-the-art reference to compact and selective gas sensors.

Quantum dots to probe temperature and pressure in highly confined liquids.

A new in situ technique for temperature and pressure measurement within dynamic thin-film flows of liquids is presented. The technique is based on the fluorescence emission sensitivity of CdSe/CdS/ZnS quantum dots to temperature and pressure variations. In this respect, the quantum dots were dispersed in squalane, and their emission energy dependence on temperature and pressure was calibrated under static conditions. Temperature calibration was established between 295 K and 393 K showing a temperature sensitivity of 0.32 meV K-1. Pressure calibration was, in turn, conducted up to 1.1 GPa using a diamond anvil cell, yielding a pressure sensitivity of 33.2 meV GPa-1. The potential of CdSe/CdS/ZnS quantum dots as sensors to probe temperature and pressure was proven by applying the in situ technique to thin films of liquids undergoing dynamic conditions. Namely, temperature rises have been measured in liquid films subjected to shear heating between two parallel plates in an optical rheometer. In addition, pressure rises have been measured in a lubricated point contact under pure rolling and isothermal conditions. In both cases, the measured values have been successfully compared with theoretical or numerical predictions. These comparisons allowed the validation of the new in situ technique and demonstrated the potential of the quantum dots for further mapping application in more complex and/or severe conditions.

Neonatal suppurative parotitis over the last 4 decades: report of three new cases and review.

BACKGROUND: Neonatal suppurative parotitis is a rare disease. Only 32 cases were reported in the English-language literature between 1970 and 2004. METHODS: We searched Medline for acute, neonatal, bacterial, suppurative, parotitis, facial, preauricular swelling starting from 1970, limiting our search to the English-language literature. We reviewed all the reported cases together with three more managed in our department. RESULTS: We identified nine new cases since 2004. The total number of patients reviewed was 44, including our patients. Most of them were male (77%). The majority developed unilateral inflamed parotid swelling (77%) and exuded pus from the ipsilateral Stensen duct. Fever was seen in fewer than half of them (47%). Premature babies constituted a third of the patients. Staphylococcus aureus was the leading causative agent (61%). Most patients responded well to conservative treatment with antibiotics (77%). The most frequently used combination of antibiotics was an anti-staphylococcal agent with either an aminoglycoside or a third-generation cephalosporin. A minority required surgical drainage. No deaths were reported in the group studied after 1970. CONCLUSION: Neonatal suppurative parotitis is rare but easy to diagnose and if readily treated with appropriate antibiotics the outcome is excellent.

Appropriateness of pediatric hospitalization in a general hospital in Kuwait.

OBJECTIVES: To determine the rate of inappropriate pediatric admissions using the Pediatric Appropriateness Evaluation Protocol (PAEP) and to examine variables associated with inappropriateness of admissions. SUBJECTS AND METHODS: A prospective study was conducted in the Department of Pediatrics, Farwania General Hospital, Kuwait, to examine successive admissions for appropriateness of admission as well as several sociodemographic characteristics over a 5-month period (August 2010 to December 2010). A total of 1,022 admissions were included. RESULTS: Of the 1,022 admissions, 416 (40.7%) were considered inappropriate. Factors associated with a higher rate of inappropriate admission included older age of patients and self-referral. CONCLUSION: The rate of inappropriate hospitalization of children was high in Farwania Hospital, Kuwait, probably due to the relatively free health care services, parental preference for hospital care, easy access to hospital services, and insufficient education about the child's condition.

Ethylmalonic encephalopathy. Another patient from Kuwait.

We report a Kuwaiti girl with ethylmalonic encephalopathy. She presented at the age of 4 months with chronic mucoid diarrhea and delayed psychomotor development, and at 6 months she developed myoclonic epilepsy. She was found to have central hypotonia with pyramidal tract signs, acrocyanosis, and petechiae. Plasma lactate level was elevated. Blood spot and urine for organic acids results were consistent with the diagnosis of ethylmalonic encephalopathy. Cerebral MRI showed basal ganglia and white matter changes. Gene mutation study revealed homozygous deletion of exon 4 of the ETHE1 gene. The patient died at 14 months after extensive bronchopneumonia. Our objective is to alert physicians to the existence of such a devastating disease in our community and their role in the early diagnosis in the index patient for proper genetic counseling.