Sensitivity of vocal fold vibratory modes to their three-layer structure: implications for computational modeling of phonation

The sensitivity of the eigenmodes and eigenfrequencies of the human vocal fold to its three-layer structure is studied using finite-element modeling. The study covers a variety of three-dimensional vocal fold models ranging from an idealized, longitudinally uniform structure to a physiologically more realistic, longitudinally varying structure. Geometric parameters including the thickness of the ligament and cover layers as well as the ligament length are varied systematically. The results indicate that vocal fold vibratory modes are quite insensitive to the longitudinal variation in the thickness of the three layers as well as the variation in ligament length. However, significant overall changes in thickness of each layer can produce noticeable changes in these modes. The implications of these findings on computational modeling of phonation are discussed.

Direct-numerical simulation of the glottal jet and vocal-fold dynamics in a three-dimensional laryngeal model

An immersed-boundary method based flow solver coupled with a finite-element solid dynamics solver is employed in order to conduct direct-numerical simulations of phonatory dynamics in a three-dimensional model of the human larynx. The computed features of the glottal flow including mean and peak flow rates, and the open and skewness quotients are found to be within the normal physiological range. The flow-induced vibration pattern shows the classical "convergent-divergent" glottal shape, and the vibration amplitude is also found to be typical for human phonation. The vocal fold motion is analyzed through the method of empirical eigenfunctions and this analysis indicates a 1:1 modal entrainment between the "adduction-abduction" mode and the "mucosal wave" mode. The glottal jet is found to exhibit noticeable cycle-to-cycle asymmetric deflections and the mechanism underlying this phenomenon is examined.

Hotspot decorations map plasmonic patterns with the resolution of scanning probe techniques

In high definition mapping of the plasmonic patterns on the surfaces of nanostructures, the diffraction limit of light remains an important obstacle. Here we demonstrate that this diffraction limit can be completely circumvented. We show that upon illuminating nanostructures made of nickel and palladium, the resulting surface-plasmon pattern is imprinted on the structures themselves; the hotspots (regions of local field enhancement) are decorated with overgrowths, allowing for their subsequent imaging with scanning-probe techniques. The resulting resolution of plasmon pattern imaging is correspondingly improved.

Search for effects beyond the born approximation in polarization transfer observables in e(over→)p elastic scattering

Intensive theoretical and experimental efforts over the past decade have aimed at explaining the discrepancy between data for the proton electric to magnetic form factor ratio, G(E)/G(M), obtained separately from cross section and polarization transfer measurements. One possible explanation for this difference is a two-photon-exchange contribution. In an effort to search for effects beyond the one-photon-exchange or Born approximation, we report measurements of polarization transfer observables in the elastic H(e[over →],e(')p[over →]) reaction for three different beam energies at a Q(2)=2.5  GeV(2), spanning a wide range of the kinematic parameter ε. The ratio R, which equals μ(p)G(E)/G(M) in the Born approximation, is found to be independent of ε at the 1.5% level. The ε dependence of the longitudinal polarization transfer component P(ℓ) shows an enhancement of (2.3±0.6)% relative to the Born approximation at large ε.

A computational study of asymmetric glottal jet deflection during phonation

Two-dimensional numerical simulations are used to explore the mechanism for asymmetric deflection of the glottal jet during phonation. The model employs the full Navier-Stokes equations for the flow but a simple laryngeal geometry and vocal-fold motion. The study focuses on the effect of Reynolds number and glottal opening angle with a particular emphasis on examining the importance of the so-called "Coanda effect" in jet deflection. The study indicates that the glottal opening angle has no substantial effect on glottal jet deflection. Deflection in the glottal jet is always preceded by large-scale asymmetry in the downstream portion of the glottal jet. A detailed analysis of the velocity and vorticity fields shows that these downstream asymmetric vortex structures induce a flow at the glottal exit which is the primary driver for glottal jet deflection.

Vitamin D: a novel therapeutic approach for keloid, an in vitro analysis

BACKGROUND

Vitamin D and its metabolites play an important role in calcium homeostasis, bone remodelling, hormone secretion, cell proliferation and differentiation. Recent studies also suggest a beneficial role of vitamin D in slowing the progression of tissue fibrosis. However, their effects on dermal fibrosis and keloids are unknown. Objectives  To investigate the effect of 1,25-dihydroxyvitamin D3 (1,25D) in the pathogenesis of tissue fibrosis by keloid fibroblasts (KFs).

METHODS

KFs were cultured and exposed to different concentrations of 1,25D in the presence or absence of transforming growth factor (TGF)-β1. KF phenotypes and protein production were analysed by real-time reverse transcriptase-polymerase chain reaction, Western blot, immunofluorescence and multiplex enzyme-linked immunosorbent assay techniques. Collagen synthesis was evaluated by measuring (3) H-proline incorporation. The effect of 1,25D on cell proliferation and viability was evaluated by Formazan assay, proliferating cell nuclear antigen expression and the colorimetric conversion of 3-[4, 5-dimethylthiazol-2-yl]-2, 5-diphenyltetrazolium bromide.

RESULTS

We confirmed the presence of vitamin D receptors (VDRs) in cultured keloid fibroblasts. Fibroblasts transfected with a vitamin D response element reporter construct and exposed to the active vitamin D metabolite 1,25D showed increased promoter activity indicating VDR functionality in these cells. Incubation of KFs with 1,25D suppressed TGF-β1-induced collagen type I, fibronectin and α-smooth muscle actin expression. 1,25D also modulated plasminogen activator inhibitor-1 and matrix metalloproteinase-9 expression induced by TGF-β1. Interestingly, 1,25D induced hepatocyte growth factor mRNA expression and protein secretion in keloid fibroblasts.

CONCLUSIONS

This study highlights key mechanistic pathways through which vitamin D decreases fibrosis, and provides a rationale for studies to test vitamin D supplementation as a preventive and/or early treatment strategy for keloid and related fibrotic disorders.

Human papillomavirus 16 or 18 infection and prostate cancer risk: a meta-analysis

OBJECTIVE

Whether the oncogenic human papillomavirus (HPV) infection, especially infection with the most common subtypes 16 or 18, is related to prostate carcinogenesis remains conflicting. A meta-analysis with updated data was performed to obtain a more precise estimate of the association between them.

METHODS

Eligible studies were retrieved via both computer searches and review of references. The relation of HPV-16 or HPV-18 infection to prostate cancer (PC) was quantified separately. Stratified analyses based on HPV detection methods and geographic regions were also performed. Estimates of OR with 95% CI were summarized using the fixed-effect or random-effect models as appropriate.

RESULTS

Twenty-five eligible studies were retrieved. All the 25 studies were assigned for exploring the relation of HPV-16 infection to PC, while 13 studies provided additional information on HPV-18 simultaneously. In the overall estimates, the pooled OR indicated no significant increase of PC risk related with either HPV-16 (OR 1.09; 95% CI 0.97-1.23; P(heterogeneity) = 0.135) or HPV-18 (OR 1.05; 95% CI 0.89-1.24; P(heterogeneity) = 0.314) infection. Further quantitative assay of stratified data could also not yield any significant result, except the stratified analysis on HPV-16 DNA detection, which revealed higher HPV-16 DNA prevalence in PC cases (OR 1.54; 95% CI 1.07-2.20; P(heterogeneity) = 0.130).

CONCLUSIONS

Even though the overall estimates did not provide a supportive evidence for the causal role of HPV in prostate carcinogenesis, higher HPV-16 DNA prevalence in PC cases from the stratified analysis still indicated a potential association between HPV infection and PC risk in our meta-analysis.

Effects of orthotopic liver transplantation in inbred rats on bone biomechanical properties

AIM

To determine the effects of orthotopic liver transplantation in inbred rats on the mechanical properties of bones at different anatomic sites.

METHODS

The 24 rats that survived liver transplantation were paired with sham-operated rats of similar body weight. Six months after surgery, the lumbar vertebra, the proximal femur, and the middle femoral shaft were measured for their biomechanical properties and bone mineral density.

RESULTS

The ultimate force, the ultimate stress, the Young modulus and the bone mineral density of both the proximal femur and the middle femur shaft of the rats were significantly reduced in the liver transplant group. However, no significant change was observed in the various parameters that indicate the biomechanical properties and the bone mineral density of the lumbar vertebra.

CONCLUSIONS

Orthotopic liver transplantation impairs the biomechanical properties of the proximal femur and the middle femoral shaft. Orthotopic liver transplantation itself is one of the risk factors for posttransplant fracture.

A coupled sharp-interface immersed boundary-finite-element method for flow-structure interaction with application to human phonation

A new flow-structure interaction method is presented, which couples a sharp-interface immersed boundary method flow solver with a finite-element method based solid dynamics solver. The coupled method provides robust and high-fidelity solution for complex flow-structure interaction (FSI) problems such as those involving three-dimensional flow and viscoelastic solids. The FSI solver is used to simulate flow-induced vibrations of the vocal folds during phonation. Both two- and three-dimensional models have been examined and qualitative, as well as quantitative comparisons, have been made with established results in order to validate the solver. The solver is used to study the onset of phonation in a two-dimensional laryngeal model and the dynamics of the glottal jet in a three-dimensional model and results from these studies are also presented.

Real-time experimental demonstration of low-cost VCSEL intensity-modulated 11.25 Gb/s optical OFDM signal transmission over 25 km PON systems

The feasibility of utilising low-cost, un-cooled vertical cavity surface-emitting lasers (VCSELs) as intensity modulators in real-time optical OFDM (OOFDM) transceivers is experimentally explored, for the first time, in terms of achievable signal bit rates, physical mechanisms limiting the transceiver performance and performance robustness. End-to-end real-time transmission of 11.25 Gb/s 64-QAM-encoded OOFDM signals over simple intensity modulation and direct detection, 25 km SSMF PON systems is experimentally demonstrated with a power penalty of 0.5 dB. The low extinction ratio of the VCSEL intensity-modulated OOFDM signal is identified to be the dominant factor determining the maximum obtainable transmission performance. Experimental investigations indicate that, in addition to the enhanced transceiver performance, adaptive power loading can also significantly improve the system performance robustness to variations in VCSEL operating conditions. As a direct result, the aforementioned capacity versus reach performance is still retained over a wide VCSEL bias (driving) current (voltage) range of 4.5 mA to 9 mA (275 mVpp to 320 mVpp). This work is of great value as it demonstrates the possibility of future mass production of cost-effective OOFDM transceivers for PON applications.

Role of caveolin-1 in the pathogenesis of tissue fibrosis by keloid-derived fibroblasts in vitro

BACKGROUND

Recent studies have suggested that caveolin-1 (cav-1) plays an important role in the regulation of transforming growth factor (TGF)-β1 signalling and participates in the pathogenesis of tissue fibrosis. However, its effects on dermal fibrosis keloids are unknown.

OBJECTIVES

To investigate the effect of cav-1 in the pathogenesis of tissue fibrosis by keloid fibroblasts.

METHODS

Keloid fibroblasts were cultured and exposed to different concentrations of cav-1 cell-permeable peptides (cav-1p) in the presence of TGF-β1. Keloid fibroblast phenotypes and protein production were analysed by real-time reverse transcriptase-polymerase chain reaction, Western blot, and multiplex enzyme-linked immunosorbent assay techniques. The effect of cav-1p on cell viability was evaluated by MTT assay.

RESULTS

Cav-1 was markedly decreased in the keloid-derived fibroblasts. Moreover, cav-1p significantly reduced TGF-β receptor type I levels and Smad2/3 phosphorylation in response to added TGF-β1. Additionally, TGF-β1 decreased cav-1 expression in human skin fibroblasts. Cav-1 was able to suppress TGF-β1-induced extracellular matrix production in cultured keloid fibroblasts through regulation of the mitogen-activated protein kinase pathway.

CONCLUSIONS

Cav-1 appears to participate in the pathogenesis of tissue fibrosis in keloid. Restoration of cav-1 function by treatment with a cell-permeable peptide corresponding to the cav-1 scaffolding domain may be a novel therapeutic approach in keloid.

Wide bandwidth, low loss 1 by 4 wavelength division multiplexer on silicon for optical interconnects

We demonstrate an add/drop filter based on coupled vertical gratings on silicon. Tailoring of the channel bandwidth and wavelength is experimentally demonstrated. The concept is extended to implement a 1 by 4 wavelength division multiplexer with 6 nm channel separation, 3 nm bandwidth, a flat top response with < 0.8 dB ripple within the 3 dB passband, 1 dB insertion loss and 16 dB crosstalk suppression. The device is ultracompact, having a footprint < 2 X 10(-9)/2.

Scaling of the F2 structure function in nuclei and quark distributions at x>1

We present new data on electron scattering from a range of nuclei taken in Hall C at Jefferson Lab. For heavy nuclei, we observe a rapid falloff in the cross section for x>1, which is sensitive to short-range contributions to the nuclear wave function, and in deep inelastic scattering corresponds to probing extremely high momentum quarks. This result agrees with higher energy muon scattering measurements, but is in sharp contrast to neutrino scattering measurements which suggested a dramatic enhancement in the distribution of the "superfast" quarks probed at x>1. The falloff at x>1 is noticeably stronger in 2H and 3He, but nearly identical for all heavier nuclei.

Caesarean delivery on maternal request and childhood psychopathology: a retrospective cohort study in China

OBJECTIVE

To prospectively examine the association between mode of delivery and childhood psychopathology.

DESIGN

Retrospective cohort study.

SETTING

Eighteen counties and three cities in China.

POPULATION

A total of 4190 preschool children whose mothers were registered in a perinatal surveillance programme were assessed with the Child Behaviour Checklist (CBCL), an instrument to assess child emotional (internalising) and behavioural (externalising) problems.

METHODS

Differences in CBCL problem scores were analysed both quantitatively and categorically among children born by caesarean delivery on maternal request (CDMR), assisted vaginal delivery (AVD), and spontaneous vaginal delivery (SVD).

MAIN OUTCOME MEASURES

The CBCL total, externalising, and internalising scores.

RESULTS

There were significant differences in the mean scores of total (20.9, 23.0, and 25.0), externalising (7.6, 8.4, and 9.1), and internalising (4.7, 5.2, and 5.6) problems among children born by CDMR, SVD, and AVD, after adjusting for potential confounding factors (P = 0.007, 0.014, and 0.031). Children born by AVD were more likely than those born by SVD to have total (OR 1.43; 95% CI 1.10-1.86), externalising (OR 1.46; 95% CI 1.11-1.92), and internalising (OR 1.41; 95% CI 1.08-1.84) scores in the highest quartile, whereas children born by CDMR were less likely to have externalising scores in the highest quartile (OR 0.64; 95% CI 0.42-0.97). Furthermore, there were significant increasing linear trends on all problem scores, and in the odds of being in the highest quartile, from children born by CDMR to those born by SVD and AVD.

CONCLUSION

The likelihood of childhood psychopathological problems may be the lowest in children born by CDMR, followed by those born by SVD, whereas the highest probability was observed in those born by AVD.

The protein kinase Pak4 disrupts mammary acinar architecture and promotes mammary tumorigenesis

The Pak4 serine/threonine kinase is highly expressed in many cancer cell lines and human tumors. While several studies have addressed the role for Pak4 in transformation of fibroblasts, most human cancers are epithelial in origin. Epithelial cancers are associated not only with changes in cell growth, but also with changes in the cellular organization within the three dimensional (3D) architecture of the affected tissues. Here we used immortalized mouse mammary epithelial cells (iMMECs) as a model system to study the role for Pak4 in mammary tumorigenesis. iMMECs are an excellent model system for studying breast cancer they can grow in 3D-epithelial cell culture, where they form acinar structures that recapitulate in vivo mammary morphogenesis. While Pak4 is expressed at low levels in wild type iMMECs, it is overexpressed in response to oncogenes, such as oncogenic Ras and Her2/neu. Here we found that overexpression of Pak4 in iMMECs leads to changes in 3D acinar architecture that are consistent with oncogenic transformation. These include decreased central acinar cell death, abrogation of lumen formation, cell polarity alterations, and deregulation of acinar size and cell number. Furthermore, iMMECs overexpressing Pak4 form tumors when implanted into the fat pads of athymic mice. Our results suggest that overexpression of Pak4 triggers events that are important for the transformation of mammary epithelial cells. This is likely to be due to the ability of Pak4 to inhibit apoptosis and promote cell survival, and thus subsequent uncontrolled proliferation, and to its ability to deregulate cell shape and polarity.

A computational study of the effect of vocal-fold asymmetry on phonation

Unilateral laryngeal paralysis leads to tension imbalance and hence to asynchronous movements between the two vocal folds during phonation. In the current study, a computational model of phonation that couples a two-mass model of the vocal folds with a Navier-Stokes model of the glottal airflow, has been used to examine the dynamics of vocal fold configurations with tension imbalance and its implications for phonation. The simulations show that tension imbalance influences phonation onset, intensity as well as the fundamental phonation frequency. Distinct non-linear effects such as period-doubling bifurcation and preferential frequency selection are also observed.