Degree Of Constriction Research Articles

TheCaloglossa leprieuriiComplex (Delesseriaceae, Rhodophyta) in the Americas: the Elucidation of Overlooked Species Based on Molecular and Morphological Evidence

Abstract The red algal genus Caloglossa (Delesseriaceae, Ceramiales) in the New World is represented by Caloglossa leprieurii sensu lato. The earliest name for any species in the genus, other than the basionym Delesseria leprieurii, is Apiarium apiculum. On the basis of comparative morphological data, and rbcL and LSU rDNA sequence analyses, the C. leprieurii complex in the New World is found to include four species: C. leprieurii, C. apomeiotica, C. apicula comb, nov., and C. ruetzleri sp. nov. The four species can be distinguished by subtle vegetative characters, including rhizoid morphology, the degree of constriction at the thallus nodes, presence or absence of adventitious branches, number of cell rows cut off from the first axial cell of the main axis, and the position of the cystocarp on the blades. A dichotomous key highlights the diagnostic vegetative characters to separate species of the C. leprieurii complex that occur in the Americas. Caloglossa leprieurii is a tropical species from the Caribb...

Articulatory–acoustic kinematics: The production of American English /s/

Due to its aerodynamic, articulatory, and acoustic complexities, the fricative /s/ is known to require high precision in its control, and to be highly resistant to coarticulation. This study documents in detail how jaw, tongue front, tongue back, lips, and the first spectral moment covary during the production of /s/, to establish how coarticulation affects this segment. Data were obtained from 24 speakers in the Wisconsin x-ray microbeam database producing /s/ in prevocalic and pre-obstruent sequences. Analysis of the data showed that certain aspects of jaw and tongue motion had specific kinematic trajectories, regardless of context, and the first spectral moment trajectory corresponded to these in some aspects. In particular contexts, variability due to jaw motion is compensated for by tongue-tip motion and bracing against the palate, to maintain an invariant articulatory-aerodynamic goal, constriction degree. The change in the first spectral moment, which rises to a peak at the midpoint of the fricative, primarily reflects the motion of the jaw. Implications of the results for theories of speech motor control and acoustic-articulatory relations are discussed.

Phonological differentiation before age two in a Tagalog–Spanish–English trilingual child

This study focuses on a trilingual toddler's ability to differentiate her Tagalog, Spanish and English productions on phonological/phonetic grounds. Working within the articulatory phonology framework, the word-initial segments produced by the child in Tagalog, Spanish and English words at age 1;10 were narrowly transcribed by two researchers and her accuracy levels in employing/reproducing the specific gestural properties of word-initial consonants (e.g. constricting organ, location, degree and glottal gestures) were compared across languages. The child's phonetic inventories in each language were also compared to those produced by monolingual peers to assess whether trilingual exposure had any consequence on phonological production. The results indicate that the child's accuracy levels in word-initial segments differed significantly from language to language reflecting distinct levels of phonological development. The child's performance with organ and location was indeed higher in her stronger language(s), while success in reproducing constriction degree tended to be greater in those languages with a larger variety of fricatives. The child also produced a variety of language-specific phonemes that went beyond the average monolingual inventory, suggesting that multilingual exposure might lead to a heightened attention towards the phonological properties of these languages, thereby enhancing phonological production.

High on altitude: new attitudes toward human cerebral blood flow regulation and altitude acclimatization

High on altitude: new attitudes toward human cerebral blood flow regulation and altitude acclimatization

Use of adipose tissue-derived stromal cells for prevention of esophageal stricture after circumferential EMR in a canine model

EMR is an accepted treatment for early esophageal carcinoma. However, resection of a large mucosal area often causes postoperative esophageal stricture. To investigate the efficacy of autologous adipose tissue-derived stromal cells (ADSCs) for prevention of stricture formation after EMR in dogs. Animal study. University research center. Ten beagle dogs were randomized into a control group and an ADSCs-injected (ADSC) group. The ADSCs were isolated from autologous adipose tissue. Immediately after circumferential esophageal EMR, about 5 × 10(6) ADSCs suspended in 8 mL of phosphate-buffered saline solution were injected endoscopically into the residual submucosa of the ADSC group, whereas the control group received only 8 mL of phosphate-buffered saline solution. Dysphagia score, weight loss, rate of mucosal constriction, and histologic assessments. In the control and ADSC groups, the median dysphagia scores were 4 and 1 (P < .043), the mean degrees of mucosal constriction were 75.7% and 45.3% (P < .008), and the numbers of nascent microvessels in the submucosal layer were 7.4 and 16.2 per unit area (P = .007), respectively. Atrophy and fibrosis of the muscularis propria layer were observed in the control group. Animal study, small sample size. Injection therapy with autologous ADSCs suppresses constriction of the esophageal mucosa and improves clinical symptoms after circumferential EMR in this canine model.

Analytical investigations of varying cross section microstructures on charge transfer in solid oxide fuel cell electrodes

An extended surface modeling concept (electrochemical fin) is applied to charge transport within the SOFC electrode microstructure using an analytical modeling approach analogous to thermal fin analysis. This model is distinct from similar approaches applied to SOFC electrode microstructure in its application of a governing equation that allows for variable cross-section geometry. The model presented is capable of replicating experimentally observed electrode behavior inclusive of sensitivity to microstructural geometry, which stands in contrast to existing models that apply governing equations analogous to a constant cross-section thermal fin equation. Insights learned from this study include: the establishment of a suite of dimensionless parameters and performance metrics that can be applied to assess electrode microstructure, the definition of microstructure-related transport regimes relevant to electrode design, and correlations that allow performance predictions for electrodes that provide cell structural support. Of particular note, the variable cross-section modeling approach motivates the definition of a sintering quality parameter that quantifies the degree of constriction within the conducting network of the electrode, a phenomenon that exerts influence over electrode polarization. One-dimensional models are presented for electrochemical fins of several cross-sectional geometries with the ultimate goal of developing a general tool that enables the prompt performance evaluation of electrode microstructures. Such a tool would facilitate SOFC microstructural design by focusing more detailed modeling efforts on the most promising microstructures.

Dynamical account of how /b, d, g/ differ from /p, t, k/ in Spanish: Evidence from labials

This study examines articulatory lenition of intervocalic stops in Spanish and tests the theories that 1) /b, d, g/ have an intended target for closure equal to that of /p, t, k/ and 2) spirantization of /b, d, g/ is caused by undershoot due to their short duration phrase medially. Consistent with past acoustic studies, subjects produce /b/ with incomplete closure phrase medially and complete closure phrase initially. Additionally, /b/ is shorter than /p/ phrase medially though not initially. For /b/, though not for /p/, there is a correlation between constriction degree and duration, consistent with the theory of dynamical undershoot. The results from the study are accurately modeled with a virtual target for /b/ slightly beyond the point of articulator contact. Such a target results in full closure at long durations (such as found phrase initially) and incomplete closure at shorter durations. Based on this evidence, it is proposed that /b, d, g/ differ from /p, t, k/ in three ways: they are shorter, lack a devoicing gesture, and have a target closer to - but still beyond - the point of articulator contact.

Relationship between Circulating Platelet Counts and Ductus Arteriosus Patency after Indomethacin Treatment

To determine whether low platelet counts are related to the incidence of patent ductus arteriosus (PDA) after indomethacin treatment in preterm human infants. Multivariable logistic regression modeling was used for a cohort of 497 infants, who received indomethacin (within 15 hours of birth). Platelet counts were not related to the incidence of permanent closure after indomethacin constriction. There was a relationship between platelet counts and the initial degree of constriction; however, this relationship appeared to be primarily influenced by the high end of the platelet distribution curve. PDA incidence was similar in infants with platelet counts < 50 × 10⁹/L and those with platelet counts above this range. Only when platelet counts were consistently >230 ×10⁹/L was there a decrease in PDA incidence. In contrast to the evidence in mice, low circulating platelet counts do not affect permanent ductus closure (or ductus reopening) in human preterm infants.

Determining Nanocapillary Geometry from Electrochemical Impedance Spectroscopy Using a Variable Topology Network Circuit Model

Solid-state nanopores and nanocapillaries find increasing use in a variety of applications including DNA sequencing, synthetic nanopores, next-generation membranes for water purification, and other nanofluidic structures. This paper develops the use of electrochemical impedance spectroscopy to determine the geometry of nanocapillaries. A network equivalent circuit element is derived to include the effects of the capacitive double layer inside the nanocapillaries as well as the influence of varying nanocapillary radius. This variable topology function is similar to the finite Warburg impedance in certain limits. Analytical expressions for several different nanocapillary shapes are derived. The functions are evaluated to determine how the impedance signals will change with different nanocapillary aspect ratios and different degrees of constriction or inflation at the capillary center. Next, the complex impedance spectrum of a nanocapillary array membrane is measured at varying concentrations of electrolyte to separate the effects of nanocapillary double layer capacitance from those of nanocapillary geometry. The variable topology equivalent circuit element model of the nanocapillary is used in an equivalent circuit model that included contributions from the membrane and the measurement apparatus. The resulting values are consistent with the manufacturer's specified tolerances of the nanocapillary geometry. It is demonstrated that electrochemical impedance spectroscopy can be used as a tool for in situ determination of the geometry of nanocapillaries.

Articulation from acoustics: Estimating constriction degree from the acoustic signal.

Voiced stops in Spanish (/b/, /d/, /g/) are often realized as approximants with incomplete supralaryngeal closure. A number of studies have shown that these are not allophonic variants but rather form part of a continuum of productions, influenced by a number of segmental and prosodic factors. Most work on this topic has used indirect acoustic measurements to estimate articulatory constriction degree. These methods include energy difference in CV (intensity minimum of the consonant over intensity maximum of adjacent vowels), spectral tilt, and maximum rising velocity of the intensity envelope in the CV transition [Kingston, LASP 3, (2008)]. These acoustic measures of constriction, while generally showing the same overall patterns, at times show significant differences in exact results [Hualde et al., LSRL (2010)]. The current study tests the accuracy of all three measures by comparing the acoustic results with articulatorily constriction degree, measured via electromagnetic articulometry (EMA). Comparisons are conducted using only /b/, as calculation of articulatory constriction degree using EMA is more accurate for bilabials than for coronals or velars. The results show for the first time the relative accuracy of three widely used acoustic tools for estimating articulatory constriction degree.

Temporal analysis of articulatory speech errors using direct image analysis of real time magnetic resonance imaging.

Articulometry studies have demonstrated that speech errors often involve gestural intrusions that are coproduced with other gestures and can go unnoticed because they are not always perceived to be segmental errors. [Mowrey and MacKay (1990)]. Real time magnetic resonance imaging was used to examine tongue movement during the production of English minimal pairs “cop-top,” “kid-kim,” “sop-shop,” and “bad-bang.” Subjects’ upper airways were imaged in the midsagittal plane while they uttered repetitions of each word pair as rapidly as possible for 15 sec. Degree of constriction in each region of interest (labial, alveolar, post-alveolar, and velic) was automatically tracked with direct image processing techniques. We calculate the mean intensity of temporally correlated pixels in that region–a metric which has been found to provide a robust estimate of constriction degree in noisy data. [Lammert (in preparation).] Gestural intrusions are observed throughout these data; frequency of occurrence increases with speech rate. Intrusions are invariably synchronous with the alternating contrastive gesture, e.g., additional velic gestures are observed at the same time as the tongue tip constriction in the word pair “cop-top.” These data are consistent with the hypothesis that speech production involves the coordination of dynamically defined action units. [Goldstein et al. (2007).]

Dynamics of tidal volume and ventilation heterogeneity under pressure-controlled ventilation during bronchoconstriction: a simulation study

The difference in effectiveness between volume-controlled ventilation (VCV) and pressure-controlled ventilation (PCV) on mechanically ventilated patients during bronchoconstriction is not totally clear. PCV is thought to deliver a more uniform distribution of ventilation than VCV, but the delivered tidal volume could be unstable and affected by changes in the degree of constriction. To explore the magnitude of these effects, we ran numerical simulations with both modes of ventilation in a network model of the lung in which we incorporated not only the pressure and flow dynamics along the airways but also the effect of cycling pressures and tissue tethering forces during breathing on the dynamic equilibrium of the airway smooth muscle (ASM) (Venegas et al., Nature 434: 777-782). These simulations provided an illustration of changes in airway radii, the total delivered tidal volume stability, and distribution of ventilation following a transition from VCV to PCV and during progressively increasing ASM activation level. These simulations yielded three major results. First, the ventilation heterogeneity and patchiness in ventilation during steady-state VCV were substantially reduced after the transition to PCV. Second, airway radius, tidal volume, and the distribution of ventilation under severe bronchoconstriction were highly sensitive to the setting of inspiratory pressure selected for PCV and to the degree of activation of the ASM. Third, the dynamic equilibrium of active ASM exposed to cycling forces is the major contributor to these effects. These insights may provide a theoretical framework to guide the selection of ventilation mode, the adjustment of ventilator settings, and the interpretation of clinical observations in mechanically ventilated asthmatic patients.

Vowel constrictions are recoverable from formants

The area function of the vocal tract in all of its spatial detail is not directly computable from the speech signal. But is partial, yet phonetically distinctive, information about articulation recoverable from the acoustic signal that arrives at the listener's ear? The answer to this question is important for phonetics, because various theories of speech perception predict different answers. Some theories assume that recovery of articulatory information must be possible, while others assume that it is impossible. However, neither type of theory provides firm evidence showing that distinctive articulatory information is or is not extractable from the acoustic signal. The present study focuses on vowel gestures and examines whether linguistically significant information, such as the constriction location, constriction degree, and rounding, is contained in the speech signal, and whether such information is recoverable from formant parameters. Perturbation theory and linear prediction were combined, in a manner similar to that in Mokhtari (1998) [Mokhtari, P. (1998). An acoustic-phonetic and articulatory study of speech-speaker dichotomy. Doctoral dissertation, University of New South Wales], to assess the accuracy of recovery of information about vowel constrictions. Distinctive constriction information estimated from the speech signal for ten American English vowels were compared to the constriction information derived from simultaneously collected X-ray microbeam articulatory data for 39 speakers [ Westbury (1994). Xray microbeam speech production database user's handbook. University of Wisconsin, Madison, WI]. The recovery of distinctive articulatory information relies on a novel technique that uses formant frequencies and amplitudes, and does not depend on a principal components analysis of the articulatory data, as do most other inversion techniques. These results provide evidence that distinctive articulatory information for vowels can be recovered from the acoustic signal.

Cerebral Malaria: A Vasculopathy

Cerebral Malaria: A Vasculopathy

The discrimination, perception, and production of two German /r/ allophones by two groups of American English speakers.

The German /r/ sound is one of the most difficult sounds for American English (AE) speakers learning German as a foreign language. Part of this difficulty may be due to its rich phonetic variation. The standard German /r/ variant [R] and dialectal variant [R′] are achieved by varying the tongue constriction degree while keeping place of articulation constant [Schiller and Mooshammer (1995)]. The close articulatory proximity of these allophones provides an opportunity for testing the relationship between perception and production in L2 sound acquisition. The aim of this study is to investigate how well experienced AE speakers and naive AE speakers can discriminate and produce the difference between the uvular fricative [R] versus the uvular trill [R′]. Two groups of AE subjects who participated in an imitation study were prompted to produce single words beginning with either [R] or [R′]. Subjects also participated in a discrimination and categorization test. Preliminary results suggest that inexperienced AE can discriminate [R] versus [R′] well. They often perceive the sounds as /h/ and are more successful at producing [R′] than [R]. Experienced speakers also discriminate the two sounds well, perceive both sounds as the German /r/ and struggle more with producing [R′] than [R].

Circumferential mural bands in the small intestine causing simple obstructive colic: a case series

Circumferential mural band (CMB) in the small intestine is an emerging condition in Ireland. The clinical presentation is a simple obstruction of the small intestine of unknown aetiology. Horses affected with CMB in the small intestine have a good prognosis following surgical decompression into the caecum. A retrospective study was carried out and 28 cases identified from 559 colic surgeries performed over a 5.5 year period. An exploratory celiotomy was performed in every case. A simple obstruction at the mid or distal jejunum was identified caused by a CMB, which was multiple in some cases. All of the horses except 2 had undergone a regular anthelmintic programme. Manual decompression of the small intestine into the caecum resulted in resolution of the simple jejunal obstruction. A constricted segment of small intestine was resected in one case, as the degree of constriction was severe. A full thickness biopsy was taken from another case. Histopathology was performed on both samples. All horses recovered from surgery and were discharged from the hospital 7-32 days post operatively. Short-term complications were observed. Survival rate was 100% at long-term follow-up. Histopathology showed inflammatory infiltration in the submucosa, muscularis and serosa with eosinophils predominating. Parasites were not detected. Small intestine circumferential mural bands have a good prognosis after surgical decompression of the small intestine into the caecum.

The Interaction Between the Oropharyngeal Geometry and Aerosols via Pressurised Metered Dose Inhalers

This study investigated the effect of oropharyngeal geometry on inhaled aerosol characteristics via pressurised metered dose inhalers (pMDIs), both with or without spacers. Seven adult oropharyngeal models with different centreline lengths, total volumes, and degrees of constriction were employed as induction ports for a laser diffraction particle size analyser and cascade impactor. Particle size change over time, mass median aerodynamic diameter (MMAD), average median volume diameter (D(V)50), inhaled doses, and oropharyngeal depositions (percentage of the nominal dose) for aerosols via suspension and ultrafine pMDIs with or without spacers at 30 l/min airflow were determined. Variations in oropharyngeal geometry caused significant variations in inhaled particle size distributions, doses, oropharyngeal drug depositions, and particle size change over time when pMDIs were used without spacers. However, inhaled aerosol characteristics had marginal variations for the ultrafine pMDI plus large volume spacer (MMAD range: 0.69-0.78 microm, D(V)50 range: 1.27-1.36 microm, inhaled dose range: 46.46-52.92%). It was found that the amounts of inhaled aerosol particles with aerodynamic size of less than 0.83 microm via pMDIs plus large volume spacer were slightly affected by the oropharyngeal geometry. Inhaling ultrafine aerosols via spacers may reduce the effect of oropharyngeal geometry on inhaled aerosol properties.

Noninvasive assessment of coronary artery bypass graft with 64-slice CT: comparison with invasive coronary angiography

In composite arterial coronary grafts (CACGs), transport phenomena and geometry may considerably alter blood flow dynamics. CACGs aim at revascularizing pathological arteries according to the human anatomy. However, the exact mechanisms causing the failure of coronary bypass grafting are not yet well elucidated. In the present study, computational fluid dynamics (CFD) techniques are applied for the simulation of multi-branched CACGs under physiologically realistic inflow waveforms. The numerical solution is obtained by a finite-volume method formulated in non-orthogonal, curvilinear coordinates and a multi-grid approach. The geometrical models, consisting of idealized and rigid vessels, include the typical T- and a rather new Π-graft configuration. The stenotic effect is also investigated by comparing computational results for three different degrees of area constriction, namely 25%, 50% and 75%, as well as the case without stenosis. Different grafting distances and various inflow rate ratios are imposed, to give an insight into haemodynamical alterations of CACGs and to study the process of restenosis. The results focus on the interaction between the grafts and coronary flows in terms of spatial and temporal variations of velocity and wall shear stress (WSS) distribution. Prominent variations among the different geometries, concerning the velocity profiles and secondary flow motion, are shown. Moreover, the residual flow emerging from different degrees of area constriction shows that low and oscillating shear stresses may arise for even moderate stenotic fields.

Utilization of shape memory in external vein-graft meshes allows extreme diameter constriction for suppressing intimal hyperplasia: A non-human primate study

Constrictive external Nitinol meshes have been shown to suppress neointimal tissue formation and preserve endothelial integrity in vein grafts. As this mitigating effect increased with the degree of constriction, we investigated whether extreme constriction was possible without leading to detrimental luminal encroachment. A senescent non-human primate model (Chacma baboons/bilateral femoral interposition grafts) mimicking the clinical size-mismatch between vein grafts and run-off arteries was used. Control grafts were either untreated (group 1) or spray-coated with fibrin glue (group 2). Nitinol meshes constricting the lumen by <or=80% (group 3) were compared with longitudinally pleated meshes of identical circumference that constricted the lumen by >90% (group 4). Anastomotic size mismatch at implantation was expressed as quotient of cross-sectional area of run-off artery to vein graft (Q(C)). At 6 months, all vein grafts without mesh support showed thick eccentric layers of neointimal tissue (group 1: 348 +/- 130 microm [Q(C) median at implant 0.19]; group 2: 318 +/- 142 microm [Q(C) median at implant 0.17]). Fibrin glue-spraying had no effect. In contrast, neointimal tissue was absent in all mesh-supported grafts (P < .007 in all cases) both at 6 weeks/6 months (group 3: 7.5 +/- 8.8 mum and 2.5 +/- 4.4 microm [Q(C) median at implant 1.47]; group 4: 1.3 +/- 0.6 microm and 3.8 +/- 5.6 microm [Q(C) median at implant 3.09]). Except for mild tissue buckling (fold height <356 microm) in one group 3 graft, none of the mesh-constricted grafts showed wall folds. Endothelial coverage was only complete in the mesh-supported groups (100% in group 3 and 4 vs 85 +/- 14%; P < .023 in group 1). Fibrin glue alone (52 +/- 48%) did not preserve endothelialization of control grafts (P < .38). Extreme vein graft constriction using external Nitinol meshes is possible without detrimental tissue buckling. Although moderate constriction was found to be sufficient for mitigating diffuse intimal hyperplasia and endothelial detachment, extreme constriction may occasionally be required to eliminate luminal irregularities.

Dimensional analysis of human saphenous vein grafts: Implications for external mesh support

Constrictive external mesh support of vein grafts was shown to mitigate intimal hyperplasia in animal experiments. To determine the degree of constriction required for the elimination of dimensional irregularities in clinically used vein grafts, a detailed anatomic study of human saphenous veins was conducted. In 200 consecutive patients having coronary artery bypass grafting, harvested saphenous veins (length 34.4 +/- 10.8 cm) were analyzed regarding diameter irregularities, side branch distribution, and microstructure. The mean outer diameter of surgically distended saphenous veins was 4.2 +/- 0.6 mm (men, 4.3 +/- 0.6 mm vs women, 3.9 +/- 0.5 mm; P < .0001). Although the outer diameter significantly decreased over the initial 18 cm (-7.6%; P < .0001), the overall increase between malleolus and thigh was not significant (+11.2%). Smaller-diameter veins (<3.5 mm) had more pronounced diameter fluctuations than larger veins (31.8% +/- 11.0% vs 21.2% +/- 8.8%; P < .0001), with more than 71% of all veins showing caliber changes of more than 20%. There was 1 side branch every 5.4 +/- 4.3 cm, with a significantly higher incidence between 20 and 32 cm from the malleolus (P < .0001 to distal, P < .0004 to proximal). Generally, women had more side branches than men (0.30 +/- 0.15 cm(-1) vs 0.25 +/- 0.12 cm(-1); P = .0190). Thick-walled veins (565.7 +/- 138.4 mum) had a significantly higher number of large side branches (P < .0001), and thin-walled veins (398.7 +/- 123.2 mum) had significantly more small side branches (P < .0001). Pronounced intimal thickening ("cushions") was found in 28% of vessels (119.8 +/- 28.0 mum vs 40.1 +/- 18.2 mum; P < .0001). Although the preferential location of side branches may be addressed by the deliberate discarding of infragenicular vein segments, a diameter constriction of 27% on average would eliminate diameter irregularities in 98% of vein grafts.