Static and dynamic solution properties of monodisperse oligofluorenes.

Dynamic light scattering techniques were employed for the study of molecular and collective properties of newly synthesized oligomers (n = 3-7) of the polyfluorene in toluene solutions. At low concentrations, the molar mass, interaction parameter, optical anisotropy and the transport coefficients for translational and rotational diffusion provide a consistent description using a rigid rod model with thickness b = 0.6 nm and length L = nl (l = 0.75 nm). This description is in agreement with the persistence length (6-7 nm) reported for the fluorene polymers. In the non-dilute regime, the estimated concentration for the lyotropic transition further supports the proposed molecular shape and the second slow process in the intermediate scattering function relates to the formation of almost spherical clusters above about 30%.

Orientation dynamics in isotropic phases of model oligofluorenes: glass or liquid crystal.

Orientation molecular dynamics were investigated in a series of "defect-free" oligofluorenes by depolarized dynamic light scattering and dynamic NMR spectroscopy. Typical liquid crystalline pretransitional dynamics were observed upon cooling the isotropic phase to the liquid crystalline phase with strong increase of the scattered intensity and slowing down of the characteristic time of the probed collective relaxation. This is well accounted for by the Landau-de Gennes theory, however, with a strong temperature dependence of the viscosity coefficient, reflecting the proximity of the glass transition. For the trimer the two transitions almost overlap and the molecular orientation coincide with the alpha-relaxation associated with the glass transition. The NMR measurements confirm that the time scale of the dynamics is completely governed by the glass process, yet the geometry of the motion is anisotropic, yielding order parameters ranging from 0.15 to 0.25 for the long axis in the liquid crystalline phase. The glass transition is therefore geometrically restricted with poorly ordered mesophase which is consistent with the weak transverse phonons in the light scattering experiment down to Tg+20 K.

Older individuals have increased oro-nasal breathing during sleep.

Breathing route during sleep has been studied very little, however, it has potential importance in the pathophysiology of sleep disordered breathing. Using overnight polysomnography, with separate nasal and oral thermocouple probes, data were obtained from 41 subjects (snorers and nonsnorers; 25 male and 16 female; aged 20-66 yrs). Awake, upright, inspiratory nasal resistance (Rn) was measured using posterior rhinomanometry. Each 30-s sleep epoch (not affected by apnoeas/hypopnoeas) was scored for presence of nasal and/or oral breathing. Overnight, seven subjects breathed nasally, one subject oro-nasally and the remainder switched between nasal and oro-nasal breathing. Oral-only breathing rarely occurred. Nasal breathing epochs were 55.79 (69.78) per cent of total sleep epochs (%TSE; median (interquartile range)), a value not significantly different to that for oro-nasal (TSE: 44.21 (68.66)%). Oro-nasal breathing was not related to snoring, sleep stage, posture, body mass index, height, weight, Rn (2.19 (1.77) cm H2O x L(-1) x sec(-1)) or sex, but was positively associated with age. Subjects > or = 40 yrs were approximately six times more likely than younger subjects to spend >50% of sleep epochs utilising oro-nasal breathing. Ageing is associated with an increasing occurrence of oro-nasal breathing during sleep.

Prediction and observation of sustained oscillations in a sheared liquid crystalline polymer.

Experimental observations of sustained oscillations of both shear stress and first normal stress differences are reported in flowing liquid crystalline polymers in a limited range of shear rates. The results can be described by considering the response of a rigid-rod model. Depending on the initial conditions, the frequency spectrum of the stress signal contains either one or two characteristic frequencies. This can be explained by the occurrence of either pure "wagging" or the coexistence of wagging and "log-rolling" behavior of the director.

Uncommon clinical course of multiple osteochondromatosis in a patient with a long-term history of Cushing's disease.

Cushing's disease (CD), the chronic endogenous hypercortisolism derived from an ACTH-secreting pituitary adenoma, and multiple osteochondromatosis (MO), a congenital mesoderm dyschondroplasia, represent two distinct rare neoplastic diseases. Clinical appearance of MO usually occurs during the first-second decade of life. In fact, the growth of osteochondromas parallels the patient's growth, then becoming quiescent after the closure of the epiphyses and the achievement of final stature. Here we describe an uncommon case of a patient with a long-term history of childhood-onset CD, who surprisingly developed MO during the third decade of life, after the remission of CD. Indeed, a female patient had been followed for CD from the age of 12 to the age of 24 years, when CD definitively remitted. At the age of 26 the patient complained progressively worsening backache and pain at level of hips and feet. Standard radiography of skeleton showed multiple bone dysmorphisms at level of the four limbs, spine and pelvis consistent with multiple osteochondromas and exostoses. A diagnosis of MO was performed. Total body bone scintigraphy with 99mTc-MDP revealed an increased uptake of the radioligand, suggesting an increased metabolic turnover in correspondence of the majority of the osteochondromas. However, the negativity of the majority of the lesions at 99mTc-DMSA scintigraphy and the histological diagnosis of benign osteochondroma of the only positive lesion at 99mTc-DMSA evidenced that the high metabolic activity of the osteochondromas was not due to malignant transformation. However, the activity of the lesions was highly surprising considering that they usually become quiescent after the achievement of the final stature. In last analysis, the uncommon characteristics of MO and, particularly, its occurrence after stable remission of hypercortisolism, suggests a possible role of glucocorticoids in influencing the clinical course of the skeletal disease. The inhibitory effect of hypercortisolism on bone growth and maturation could explain the block in the proliferation of skeletal lesions during the developmental age, where CD was in the active phase, and the opposite effect of stimulation of the ostochondromas growth during stable normalization of cortisol secretion, after CD remission.

Influence of intra-oral maxillary sports mouthguards on the airflow dynamics of oral breathing.

PURPOSE: Mouthguards worn during sporting competition may influence oral airway flow dynamics and potentially increase airflow resistance during mouth breathing. METHODS: We measured oral airflow resistance (RO) in 10 normal subjects (four men, six women, age 29 +/- 3 yr, mean +/- SEM) wearing two different custom-made maxillary mouthguards. RESULTS: During tidal mouthpiece breathing (jaw position controlled), inspiratory R(O) (at (1.4 L x s(-1)) increased from 0.22 (0.15-0.46) cm H2O x L(-1) x s(-1) (median and interquartile range) to 0.47 (0.24-0.52) cm H2O x L(-1) x s(-1) with mouthguard 1 (general sports mouthguard) and from 0.34 (0.27-0.51) to 0.46 (0.39-0.86) cm H2O x L(-1) x s(-1) (N = 8) with mouthguard 2 (laminated, field hockey mouthguard, both P < 0.05). With oral only mask breathing (jaw position not controlled), inspiratory R(O) (at 0.4 L x s(-1)) increased to 1.02 (0.42-1.57) cm H2O x L(-1) x s(-1) (P < 0.03, compared with mouthpiece) but was variably affected by both mouthguards. At 1.0 L x s(-1), there was a tendency for both mouthguards to increase inspiratory R(O); however, this effect only reached significance for mouthguard 1 during mouthpiece breathing. CONCLUSION: Thus, although maxillary mouthguards do increase R(O) when jaw position is controlled, individual subjects respond differently when in control of mouth opening. This may be related to variable recruitment of compensatory mechanisms (e.g. mouth opening and/or oral airway dilator muscle activity).

Nasal dilator strips increase maximum inspiratory flow via nasal wall stabilization.

OBJECTIVE: Inspiratory flow limitation associated with collapse of the nasal vestibular walls is a feature of nasal breathing at high ventilatory levels. We examined whether an external nasal dilator strip (ENDS) device (Breathe Right, CNS Inc., Chanhassen, MN) influences maximum inspiratory and expiratory flow rates. STUDY DESIGN: Prospective, randomized. METHODS: We studied 20 Caucasian subjects (13 female, 7 male; age range, 16-49 y) performing maximum-effort nasal flow-volume loop studies with (ENDS) and without ENDS (control) and following topical nasal decongestant (oxymetazoline hydrochloride, 0.2 mg per nostril). RESULTS: ENDS increased peak inspiratory flow from 2.55+/-0.24 L/s (mean+/-standard error [SE]) to 2.86+/-0.25 L/s and forced inspiratory flow at 50% of vital capacity from 2.23+/-0.24 L/s to 2.53+/-0.24 L/s (both, P<.0001), but had no effect on maximum expiratory flows. Nasal decongestant increased the forced expiratory volume in 1 second from 3.39+/-0.22 L/s to 3.59+/-0.22 L/s and the average forced expiratory flow over 25% to 75% of vital capacity from 3.31+/-0.31 L/s to 3.61+/-0.28 L/s (both, P< or = .008), but had no effect on maximum inspiratory flows. The combination of decongestant and ENDS increased both inspiratory and expiratory maximum flows. CONCLUSION: Since ENDS selectively increases maximum nasal inspiratory flow rates, we conclude that ENDS increases inspiratory nasal patency during maximum inspiratory efforts through the nose by supporting the lateral nasal vestibular walls and making them more resistant to collapse.

Nasal vestibule wall elasticity: interactions with a nasal dilator strip.

We studied the effect of an adhesive external nasal dilator strip (ENDS) on external nasal geometry in 20 healthy Caucasian adults (10 men, 10 women; age 21-45 yr). The recoil force exerted by ENDS was estimated by bending the device (n = 10) with known weights. In the horizontal direction, a small/medium-sized ENDS in situ exerted a unilateral recoil force of 21.4-22.6 g. Application of ENDS resulted in a displacement of the lateral nasal vestibule walls that had both anterosuperior and horizontal components and that was maintained over an 8-h period. The resultant unilateral nasal vestibule wall displacement at the tip of the device was at 47.6 +/- 2.0 degrees to the horizontal (as related to the plane of the device when in situ) and had a magnitude of 3.5 +/- 0.1 mm. ENDS increased external nasal cross-sectional area by 23.0-65.3 mm2. Nasal vestibule wall compliance was estimated at 0.05-0.16 mm/g. Thus ENDS applies a relatively constant abducting force irrespective of nasal width. Variable responsiveness to ENDS may be related to differences in elastic properties of the nasal vestibule wall.

Soft palate muscle responses to negative upper airway pressure.

The afferent pathways and upper airway receptor locations involved in negative upper airway pressure (NUAP) augmentation of soft palate muscle activity have not been defined. We studied the electromyographic (EMG) response to NUAP for the palatinus, tensor veli palatini, and levator veli palatini muscles in 11 adult, supine, tracheostomized, anesthetized dogs. NUAP was applied to the nasal or laryngeal end of the isolated upper airway in six dogs and to four to six serial upper airway sites from the nasal cavity to the subglottis in five dogs. When NUAP was applied at the larynx, peak inspiratory EMG activity for the palatinus and tensor increased significantly (P < 0.05) and plateaued at a NUAP of -10 cmH2O. Laryngeal NUAP failed to increase levator activity consistently. Nasal NUAP did not increase EMG activity for any muscle. Consistent NUAP reflex recruitment of soft palate muscle activity only occurred when the larynx was exposed to the stimulus and, furthermore, was abolished by bilateral section of the internal branches of the superior laryngeal nerves. We conclude that soft palate muscle activity may be selectively modulated by afferent activity originating in the laryngeal and hypopharyngeal airway.

Epiglottic movements during breathing in humans.

1. Using X-ray fluoroscopy we measured antero-posterior (A-P) and cranio-caudal (C-C) displacements of the epiglottic tip (ET), corniculate cartilage and hyoid bone in seven seated, normal human subjects (age 34 +/- 3 years; mean +/- S.E.M.; 4 males, 3 females) breathing via a nasal mask or mouthpiece with (RL) and without (UB) a fixed resistive load. 2. During UB, via either mouth or nose, there were no significant A-P ET movements. During RL via the nose the ET at peak expiratory flow was 2.6 +/- 1.3 mm cranial to its position at peak inspiratory flow (P < 0.05, ANOVA). C-C movements of the ET correlated strongly with C-C movements of the corniculate cartilage and hyoid bone. 3. The ET, corniculate cartilage and hyoid bone (at zero airflow) were situated more caudally during oral UB than for any other condition. 4. When present, epiglottic movements during breathing do not appear to be independent of those of the larynx and hyoid. Furthermore, epiglottic position may be related to the level of upper airway resistance.