OBJECTIVES: To describe the mechanisms and management of cold air-provoked respiratory symptoms. STUDY DESIGN: A literature review. METHODS: The review includes human epidemiological studies, human and animal experimental studies, as well as human studies about management of the cold air-provoked respiratory symptoms. RESULTS: Cold air is unlikely to be a causal factor initiating respiratory diseases but a symptom trigger. In the present review, the airway responses beyond these symptoms were divided into three types. The short-term responses are those that develop within minutes in response to sudden cooling of the airways. Subjects with asthma or rhinitis are especially prone to these responses. The long-term responses are those that develop in response to repeated and long-standing cooling and drying of the airways, usually in endurance athletes. Finally, there are the physiological, reflex-mediated lower-airway responses to cooling of the skin or upper airways. CONCLUSIONS: The mechanisms beyond cold air-provoked respiratory symptoms vary considerably and mainly depend on the individual`s susceptibility and the ventilation level during the cold exposure. An understanding of these mechanisms is essential for successful management of the symptoms. Keywords: asthma; chronic obstructive pulmonary disease; cold climate; respiratory; rhinitis; signs and symptom (Int J Circumpolar Health 2007; 66(2):91-100)

Cold air-provoked respiratory symptoms: the mechanisms and management.

The present state-of-the-art in understanding the mechanisms of the formation of porous silicon (PS) and its physical properties is reviewed, with special emphasis on problems which were not much in the focus of existing review literature: mechanisms of the pore growth, stability of the PS properties in environment and electrical properties of PS layers. Emerging applications of porous silicon in different fields of technology are outlined.

Porous silicon—mechanisms of growth and applications

Breathing cold air without proper temperature exchange can induce strong respiratory autonomic responses including cough, airway constriction and mucosal secretion, and can exacerbate existing asthma conditions and even directly trigger an asthma attack. Vagal afferent fiber is thought to be involved in the cold-induced respiratory responses through autonomic nerve reflex. However, molecular mechanisms by which vagal afferent fibers are excited by cold remain unknown. Using retrograde labeling, immunostaining, calcium imaging, and electrophysiological recordings, here we show that a subpopulation of airway vagal afferent nerves express TRPM8 receptors and that activation of TRPM8 receptors by cold excites these airway autonomic nerves. Thus activation of TRPM8 receptors may provoke autonomic nerve reflex to increase airway resistance. This putative autonomic response may be associated with cold-induced exacerbation of asthma and other pulmonary disorders, making TRPM8 receptors a possible target for prevention of cold-associated respiratory disorders.

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TRPM8 mechanism of autonomic nerve response to cold in respiratory airway

Crystallization of a-SiC:H films obtained by PECVD technique at low temperatures and results on corrosion by reactive ion etching (RIE) of these films are presented. The crystallization process was characterized by FTIR and XRD analysis; these results show evidences of crystallization with the formation of cubic SiC polycrystals (3C–SiC). The optimized RIE parameters for as-deposited a-SiC:H films indicates a maximum etch rate for 60% O2 in the gas mixture. With this condition the etch rate increases linearly with the rf power. Increasing process pressures leads to a monotonic etch rate increase, remaining nearly constant at a maximum value of 125 nm/min for pressures in the 200–300 mTorr range. For the annealed films a strong influence of the degree of crystallinity on the etch rate is observed approaching values similar to those reported for 3C–SiC plasma etching.

Post thermal annealing crystallization and reactive ion etching of SiC films produced by PECVD

SiC/Co composite particles with a core-shell structure were successfully prepared by electroless plating of cobalt on the surface of SiC particles It is found that the mass gain and reaction duration of electroless plating process are evidently affected by the initial pH value and bath temperature Content of amorphous cobalt in the plating layer increases with the increase of the initial pH value and the bath temperature Saturation magnetization of the composite particles rests on the mass gain, and the coercivity is determined by the microstructure of the plating layer

Microstructure and magnetic properties of SiC/Co composite particles prepared by electroless plating

Porous silicon obtained by anodization in the transition regime

In this paper a reactive ion etching process on amorphous silicon carbide (a-SiC) films is characterized by varying the carbon content from 0.73 molar fraction of C (Xc = 0.73) to Xc = 0 (pure a-Si). The film composition was analyzed by electron microprobe analysis. The effect of hydrogen presence in the deposition chamber and of the material doping on the etch rate was considered. The etch rate in a CF 4 O 2 plasma was investigated as a function of the r.f. power and gas pressure in the etching chamber, taking the loading effect also into account. An appreciable induction time was observed only for pure a-Si. The etch rate, increased in carbon-films, was found to be almost linearly related to the optical energy gap of the material. However, the etch rate was not a consistent function of Xc. An analytical relation between etching rate and r.f. power is proposed. Varying the gas pressure, and a-SiC etch rate slowly rises, remains nearly constant at a maximum value in the range 30–60 mTor, after which it decreases. However, no decrease at higher pressure was seen for the a-Si: H films.

Reactive ion etching characterization of a-SiC: H in CF4/O2 plasma

It is shown that the multipulse free‐running ruby laser irradiation of z‐cut LiNbO3 single‐crystalline samples with 400 A‐thick Ti deposits results, under certain conditions, in an efficient Ti indiffusion with minimum perturbation. Implanted zones exhibit optical characteristics appropriate for the preparation of optical devices.

Evidence of refractive index change by Ti indiffusion into LiNbO3 substrate as a result of multipulse free‐running ruby laser irradiation

We studied Ti in-diffusion as an effect of multipulse laser irradiation, in either visible of ultraviolet (u.v.) spectral ranges, of LiNbO3 single-crystalline structures with Ti coatings of two different thicknesses. It is shown that while u.v. (excimer, λ ≈ 308 nm) laser irradiation causes a complete expulsion of the Ti deposit, the visible (ruby, λ ≈ 694·3 nm) laser irradiation at intermediate incident laser fluence (up to ≈ 0·7 J cm−2) promotes efficient Ti in-diffusion from the thin (400 A width) Ti deposit down to a micrometre range implantation depth.

One-step in-diffusion as a result of multipulse laser irradiation of LiNbO3 single crystalline substrates covered with thin Ti deposits. On the effect of the radiation wavelength

Non-linear thermo-optical properties of doped glasses can be studied with the help of the photodeflection method. We report thermal diffusivity measurements obtained through the photodeflection method in its transverse configuration in both quasi-continuous and pulsed irradiation. The photodeflection method was suitably optimized for the case of glasses with very low thermal diffusivity.

L. Schirone

Papers

Porous silicon obtained by anodization in the transition regime

Reactive ion etching characterization of a-SiC: H in CF4/O2 plasma

Evidence of refractive index change by Ti indiffusion into LiNbO3 substrate as a result of multipulse free‐running ruby laser irradiation

One-step in-diffusion as a result of multipulse laser irradiation of LiNbO3 single crystalline substrates covered with thin Ti deposits. On the effect of the radiation wavelength

Photodeflection method applied to the thermal characterization of CuCl and Cu2O glasses