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Notes: The correlation between the structural (average size and density) and optoelectronic properties [band gap and photoluminescence (PL)] of Si nanocrystals embedded in SiO2 is among the essential factors in understanding their emission mechanism. This correlation has been difficult to establish in the past due to the lack of reliable methods for measuring the size distribution of nanocrystals from electron microscopy, mainly because of the insufficient contrast between Si and SiO2. With this aim, we have recently developed a successful method for imaging Si nanocrystals in SiO2 matrices. This is done by using high-resolution electron microscopy in conjunction with conventional electron microscopy in dark field conditions. Then, by varying the time of annealing in a large time scale we have been able to track the nucleation, pure growth, and ripening stages of the nanocrystal population. The nucleation and pure growth stages are almost completed after a few minutes of annealing time at 1100 °C in N2 and afterward the ensemble undergoes an asymptotic ripening process. In contrast, the PL intensity steadily increases and reaches saturation after 3–4 h of annealing at 1100 °C. Forming gas postannealing considerably enhances the PL intensity but only for samples annealed previously in less time than that needed for PL saturation. The effects of forming gas are reversible and do not modify the spectral shape of the PL emission. The PL intensity shows at all times an inverse correlation with the amount of Pb paramagnetic centers at the Si–SiO2 nanocrystal–matrix interfaces, which have been measured by electron spin resonance. Consequently, the Pb centers or other centers associated with them are interfacial nonradiative channels for recombination and the emission yield largely depends on the interface passivation. We have correlated as well the average size of the nanocrystals with their optical band gap and PL emission energy. The band gap and emission energy shift to the blue as the nanocrystal size shrinks, in agreement with models based on quantum confinement. As a main result, we have found that the Stokes shift is independent of the average size of nanocrystals and has a constant value of 0.26±0.03 eV, which is almost twice the energy of the Si–O vibration. This finding suggests that among the possible channels for radiative recombination, the dominant one for Si nanocrystals embedded in SiO2 is a fundamental transition spatially located at the Si–SiO2 interface with the assistance of a local Si–O vibration. © 2002 American Institute of Physics.

Notes: A reproducible method for the fabrication of ZnO transducers on InSb substrates is described. These transducers are being used for ultrasonic attenuation measurements over a wide low-frequency range (90–600 MHz) at very low temperatures(0.1–4.2 K). They have been characterized by their x-ray diffraction patterns, their insertion loss, and their contribution to the acoustic attenuation in InSb at low temperatures.

Notes: 1 Type 2 diabetes is associated with diverse oral pathologies in which salivary flow reduction is one of the causes of these oral abnormalities. Scarce literature exists regarding noradrenergic transmission and adrenergic-induced salivary flow in submaxillary and parotid glands of type 2 diabetic rats. 2 We studied noradrenergic transmission as well as the secretory response to α1- and β-adrenoceptor stimulation in the parotid and submaxillary glands of type 2 diabetic rats. 3 Diabetic rats exhibited diminished neuronal uptake, release and endogenous content of noradrenaline (NE) in both salivary glands. Further, NE synthesis was also diminished accompanied by decreased tyrosine hydroxylase activity. Salivary flow responses to α1-(methoxamine) and β-(isoprenaline) adrenoceptor stimulation were reduced in the submaxillary as well as the parotid glands of diabetic rats. 4 Our results suggest that the reduction of noradrenergic transmission in the salivary glands of type 2 diabetic rats is in part responsible for the diminished salivary flow evoked by α1- and β-adrenergic stimulation. Reduced noradrenergic activity may contribute to the pathophysiology of oral abnormalities in diabetic patients.

Notes: Background: Few cases of allergy to pine nuts have been described. We report a case of anaphylactic reaction to pine nuts. The patient needed to be treated in the emergency room due to a systemic reaction immediately after eating pine nuts. Methods: The patient was studied by prick tests and prick by prick tests. Specific IgE was measured by CAP and by SDS–PAGE/immunoblotting by a diffusion method. Results: The patient showed positive prick by prick tests to pine nuts (12 mm of maximum wheal diameter). Specific IgE was positive (0.79 kU/l). The patient's serum recognized several proteins by immunoblot. However, a 17-kDa allergen band was detected with high intensity. This protein was found to be sensitive to reducing agents, losing its IgE-binding properties after reduction. Conclusions: The patient presented an IgE-mediated reaction and detected a 17-kDa protein from pine nuts not previously described.

Notes: Background: This study aimed to investigate the influence of patient selection criteria, i.e., mite-allergic individuals exposed and not exposed to Dermatophagoides siboney and Blomia tropicalis, on the biologic activity of mite extracts. Determination of the potency of mite extracts in vivo requires selection of patients with a clinical history of mite allergy. In Scandinavia, there are some anamnestic criteria for mite allergy, whereas in the tropics, where patients are continuously exposed to high levels of mites, selection of patients with mite allergy by clinical history is difficult. Methods: A total of 210 Cuban asthmatics with continuous symptoms, and 43 Swedes with a clinical history of mite allergy were investigated. Skin prick tests were performed with D. siboney, D. pteronyssinus, D. farinae, B. tropicalis, Acarus siro, Lepidoglyphus destructor, and Tyrophagus putrescentiae extracts. For analysis of the biologic activity of mite extracts, Cuban patients were divided into four groups:1)all patients skin-test-positive to mites2)patients positive to mites, but not to other inhalant allergens3)patients reacting most to the mite species analyzed4)patients reactive only to mites and reacting most to the mite species analyzed.The biologic potency was calculated according to the Nordic Guidelines. Results: Due to cross-reactivity between mites, Swedish mite-sensitive patients, with a clear clinical history of mite allergy, but not exposed to D. siboney and B. tropicalis, were more skin reactive to these mites than were Cubans. The estimated potency increased gradually to 〉200% in group 4. In group 1 Cubans, the reactivity to all mites but B. tropicalis was lower than that in mite-sensitive Swedes. Conclusions: According to the influence of patient selection criteria on the estimation of the potency of mite extracts, the determination of the biologic activity of allergenic extracts in subjects without a clear-cut clinical history should be replaced by new methods when available.

Notes: Background The role of Pyroglyphid mites in IgE-mediated serisitizalion has been well eslahlished. Although mites belonging to the genus Dermatophagoidess dominate in the acarofauna of domestic dust. non-pyroglyphid mites might also be of clinical importance. In Cuba, Dermatophagoides siboney is found in dust coexisting with D. pteronyssiuus and Blomia tropicalis. Dermatophagoides forinae is not found. Storage mites, such as Acorus siro, Lepidoglyphus destructor and Tyrophagus putrescentiae might also be present.Objective The aim of this study was to investigate the allergenic relationships among the mites present in the environment of allergic patients in Cuba.Methods The crossreactivialty between an extract of D. siboney and the above mentioned six mites was studied by specific IgE inhibition, using sera of mite-sensitive patients after incubation with serial dilutions of D. sibaney.Results The inhibitory effect of D. sidiney extract was more pronounced against D. farinae. 91%, than against D. pyteronyssinus, 62%. Specific IgE to B. tropicali, A. siro, L. destructor and T. putrescentiae were inhibited to a much lesser extent, i.e. between 47 and 58%. The correlation between IgE to D. siboney and IgE to D. pteronyssinus and D. farinae was of 0.92 and 0.90. respectively. A weaker correlation was found between D. siboney and L. destructor (0.7), A. siro (0.67), B. tropicalis (0.54) and T. putrescentiae (0.51).Conclusion Thus. D. siboney seems to be most closely related to D. farinae.