High frequency continuous birefringence-induced oscillations in spin-polarized vertical-cavity surface-emitting lasers.

Sustained, large amplitude and tunable birefringence-induced oscillations are obtained in a spin-vertical cavity surface-emitting laser (spin-VCSEL). Experimental evidence is provided using a spin-VCSEL operating at 1300 nm, under continuous-wave optical pumping and at room temperature. Numerical and stability analyses are performed to interpret the experiments and to identify the combined effects of pump ellipticity, spin relaxation rate, and cavity birefringence. Importantly, the frequency of the induced oscillations is determined by the device's birefringence rate, which can be tuned to very large values. This opens the path for ultrafast spin-lasers operating at record frequencies exceeding those possible in traditional semiconductor lasers and with ample expected impact in disparate disciplines (e.g., datacomms, spectroscopy).

Modeling thermal effects and polarization competition in vertical-cavity surface-emitting lasers.

We analyze the influence of thermal effects on the polarization-resolved light-current (LI) characteristics of verticalcavity surface-emitting lasers (VCSELs). We use a model that is an extension of the spin-flip model incorporating material gain that is frequency and temperature dependent, and a rate equation for the temperature of the active region, which takes into account decay to a fixed substrate temperature, Joule heating and nonradiative recombination heating. The model also incorporates the red shift for increasing temperature of the gain curve and of the cavity resonance. The temperature sensitivity of the lasing threshold current is found to be in good qualitative agreement with observations and with previous reports based on detailed microscopic models. The temperature dependence of the polarization switching point, when the dominant polarization turn off and the orthogonal polarization emerges, is characterized in terms of various model parameters, such as the room-temperature gain-cavity offset, the subtracte temperature, and the size of the active region.

Monopharmacologic general anaesthesia with sevoflurane in paediatric patient with Prader-Willi syndrome.

Prader-Willi syndrome (PWS) is a genetic disease caused by a loss of paternal genes located in chromosome 15. Children affected by this syndrome often have preterm delivery; during childhood the hallmarks are: severe infantile hypotonia and feeding problems. Afterward, neurologic manifestations, endocrine signs and dysmetabolic abnormalities are usually seen together with craniofacial manifestations and musculoskeletal abnormalities. Obesity causes sleep abnormalities including sleep apnea. The case we present is of a 5 year old child (CA) scheduled for strabismus surgery. The child has a lot of typical (PWS) signs. A number of anaesthesiologic problems are associated with (PWS). Some of them relate to obesity, others to facial dysmorphism. Moreover, the syndrome may give a prolonged and exaggerated response to every sedative drug. P.W.S. is also characterized by thermoregulatory disorders. Sleep apnea occurs often. Considering all these problems, we planned a monopharmacologic anaesthesiologic procedure using sevoflurane.

[Anesthesia with sevoflurane and orotracheal intubation for pediatric ophthalmic surgery of medium length in day hospital] . / Anestesia con Sevofluorano e intubazione orotracheale per interventi di oftalmochirurgia pediatrica di media durata in regime di day-hospital.

BACKGROUND: The aim of this study was to evaluate the discharge rate of children undergoing ophthalmic surgery of medium length (69-120') in a day-hospital regime under general anesthesia with orotracheal intubation and using Sevoflurane as the only anesthetic agent. EXPERIMENTAL PROTOCOL: prospective study. SETTING: the study was carried out in the operating theatre of the Ophthalmic Clinic at Florence University. PATIENTS: 58 pediatric patients aged 2-10 years, ASA I-II, 13-34 kg. OPERATIONS: correction of strabismus, cataract, glaucoma, palpebral ptosis and intubation of lacrimal tracts. Parameters measure: Any signs of reactivity in the airways to Sevoflurane on induction or reawakening (cough, bronchospasm, laryngospasm and psychomotor agitation), hemodynamic variables (heart rate and NIBP); reawakening time (from turning off the vaporiser to extubation), discharge time from recovery room (SatO2 > or = 97% in ambient atmosphere), discharge time from hospital (stable vital signs, response to simple and complex commands). RESULTS: The mean reawakening time was 7 min, discharge time from the recovery room was 20 min, discharge time from the hospital 80% after four hours, 100% after six hours. No respiratory and/or cardiovascular complications were reported nor psychomotor agitation. CONCLUSIONS: General anesthesia with Sevoflurane and Atracurium was found to be a realistic and reliable technique in pediatric ophthalmic surgery of medium length performed in day hospital.

[Latex allergy. An not rare intraoperative event]. / Allergia al lattice. Evento intraoperatorio non più raro.

Latex allergy has become a real problem among both surgical staff (paramedics and physicians) and patients especially pediatric patients with urogenital malformations and spina bifida. Latex allergy is produced from both natural molecules which compose the substance produced from Hevea brasiliensis (rubber tree) and industrial additives contents in latex devices. Diagnosis of latex allergy may be carried out through a preoperative Prik-test. A characteristic of latex allergy reaction is the starting of symptoms (more than 15 minutes after allergen contact). Pathophysiology of latex allergy is the same of all allergic reactions; it is an antigen-antibody reaction and type I or II reaction may occur. There are a lot of devices that surgeons and anesthesists use in the operative theatre and that should not be used in presence of a patient with latex allergy. Guaranteed latex-free devices should always be present in store.

Glycosylated hemoglobins and diabetic control assessment.

This historical development, biosynthesis, analysis, interpretation, and utilization of glycosylated hemoglobin determinations (HbA1 or HbA1c alone) are presented. The relationship between glycosylated hemoglobin determinations and assessment of diabetic control is discussed. HbA1 and HbA1c levels are elevated approximately twofold in diabetic patients. A correlation exists between abnormal fluctuations in blood glucose levels and HbA1 concentrations. The results of glycosylated hemoglobin determinations are not influenced by recent meals, physical activity, emotional stress, or inherited abnormalities. Although glycosylated hemoglobin determinations are subject to fewer variables than blood and urine glucose assessments, the clinician must be aware of the indications and limitations for their use. These indications and limitations are discussed.