Transient flow-driven distortion of a nematic liquid crystal in channel flow with dissipative weak planar anchoring

Motivated by the one-drop-filling (ODF) method for the industrial manufacturing of liquid crystal displays, we analyze the pressure-driven flow of a nematic in a channel with dissipative weak planar anchoring at the boundaries of the channel. We obtain quasisteady asymptotic solutions for the director angle and the velocity in the limit of small Leslie angle, in which case the key parameters are the Ericksen number and the anchoring strength parameter. In the limit of large Ericksen number, the solution for the director angle has narrow reorientational boundary layers and a narrow reorientational internal layer separated by two outer regions in which the director is aligned at the positive Leslie angle in the lower half of the channel and the negative Leslie angle in the upper half of the channel. On the other hand, in the limit of small Ericksen number, the solution for the director angle is dominated by splay elastic effects with viscous effects appearing at first order. As the Ericksen number varies, there is a continuous transition between these asymptotic behaviors, and in fact the two asymptotic solutions capture the behavior rather well for all values of the Ericksen number. The steady-state value of the director angle at the boundaries and the timescale of the evolution toward this steady-state value in the asymptotic limits of large and small Ericksen number are determined. In particular, using estimated parameter values for the ODF method, it is found that the boundary director rotation timescale is substantially shorter than the timescale of the ODF method, suggesting that there is sufficient time for significant transient flow-driven distortion of the nematic molecules at the substrates from their required orientation to occur.

Asymmetric band gap shift in electrically addressed blue phase photonic crystal fibers

In this paper, we present electrooptic experiments on photonic crystal fibers filled with a liquid crystalline blue phase. These fibers guide light via photonic band gaps (PBGs). The blue phase is isotropic in the field-off state but becomes birefringent under an electric field. This leads to a polarization dependent shift of the PBGs. Interestingly, the effect on the PBGs is asymmetrical: while the short wavelength edges of the PBGs shift, the long wavelength edges are almost unaffected. By performing band gap and modal analyses via the finite element simulations, we find that the asymmetric shift is the result of the mixed polarization of the involved photonic bands. Finally, we use the band gap shifts to calculate effective Kerr constants of the blue phase.

Chemically induced twist-bend nematic liquid crystals, liquid crystal dimers, and negative elastic constants

Here we report the chemical induction of the twist-bend nematic phase in a nematic mixture of ether-linked liquid crystal dimers by the addition of a dimer with methylene links; all dimers have an odd number of groups in the spacer connecting the two mesogenic groups. The twist-bend phase has been identified from its optical texture and x-ray scattering pattern as well as NMR spectroscopy, which demonstrates the phase chirality. Theory predicts that the key macroscopic property required for the stability of this chiral phase formed from achiral molecules is for the bend elastic constant to tend to be negative; in addition the twist elastic constant should be smaller than half the splay elastic constant. To test these important aspects of the prediction we have measured the bend and splay elastic constants in the nematic phase preceding the twist-bend nematic using the classic Frederiks methodology and all three elastic constants employing the dynamic light scattering approach. Our results show that, unlike the splay, the bend elastic constant is small and decreases significantly as the transition to the induced twist-bend nematic phase is approached, but then exhibits unexpected behavior prior to the phase transition.

Lower environmental temperature delays and prolongs myogenic regulatory factor expression and muscle differentiation in rainbow trout (Onchrhynchus mykiss) embryos

The effect of different temperatures (4 degrees C and 12 degrees C) on myogenic regulatory factors (MyoD and myogenin) and myosin heavy chain (MyHC) expression was investigated in rainbow trout (Onchrhynchus mykiss) during early development. MyoD is first switched on at stage 14 [about 5 somites are formed (1/2 epiboly)] while myogenin mRNA is expressed at stage 15 [around 15 somites are visible (2/3 epiboly)] at both temperatures. Subsequently (up to at least stage 20), the most caudal somites exhibit less myogenin mRNA at 4 degrees C compared to 12 degrees C. At the eyed stage (stage 23-24), both myogenin mRNA and protein are present in greater amounts throughout all myotomes at the lower temperature, with mRNA levels in warmer (12 degrees C) embryos at 83% for MyoD and 72% for myogenin of the levels seen in 4 degrees C embryos. Conversely, however, at this same stage, fast-MyHC mRNA and protein are more abundant in 12 degrees C than in 4 degrees C embryos. This indicates relatively advanced muscle differentiation at the warmer temperature. At hatching, myogenin-positive cells are concentrated within the myosepta at both temperatures and they are also sparsely distributed in the myotome at 4 degrees C, but not at 12 degrees C. MyoD, myogenin, and MyHC levels provide an indication of differentiation of muscle cells. These findings suggest that myogenic regulatory factor expression is delayed but prolonged by the lowering of temperature.

TEMPERATURE AND MYOGENIC FACTOR TRANSCRIPT LEVELS DURING EARLY DEVELOPMENT DETERMINES MUSCLE GROWTH POTENTIAL IN RAINBOW TROUT(ONCORHYNCHUS MYKISS) AND SEA BASS (DICENTRARCHUS LABRAX)

The influence of changes in environmental temperature on the mRNA levels of myogenic regulatory factors (MRFs), i.e. MyoD and myogenin, as well as myosin heavy chain (MyHC) were studied during early larval development in rainbow trout and sea bass. Phosphoimager analysis of northern blots indicated that there is an optimum temperature for the RNA transcript levels of MRF and MyHC RNA in trout and in sea bass larvae. In the trout strain studied, the highest concentration for MRF and MyHC transcripts was found at 8°C rather than 4°C or 20°C. In European sea bass, the highest concentrations of MRF and MyHC mRNA were observed at 15-20°C rather than 13°C. Raising sea bass larvae at 15°C was associated with higher MyHC gene expression as well as a trend towards an increase in total muscle fibre number and higher growth rates after transfer at ambient temperature. Results suggest that mRNA levels of MRF and MyHC can be used to optimise early development. An experiment in which the temperature was changed illustrates the consequence of precise temporal expression of MRF genes in specifying muscle fibre number at critical stages during early development.

Increasing the esthetics, production and profit of fabricating ceramic restorations with an alternative build-up technique

The purpose of this article is to demonstrate the advantages and benefits of utilizing The Dry Powder Technique during the fabrication of ceramic restorations. This article explains how to create esthetically superior restorations using an unlimited number of porcelain powders while conserving time and materials. By utilizing dry powder storage containers, kolinsky sable brushes, capillary attraction and multiple oven firing procedures, a ceramist may control grain size distribution, color and contour with a minimum of effort and maximum of results.

Identification and expression analysis of two developmentally regulated myosin heavy chain gene transcripts in carp (Cyprinus carpio)

Whilst developmentally regulated genes for the myosin heavy chain (MyoHC) have been characterised in mammalian, avian and amphibian species, no developmental MyoHC gene has previously been characterised in a species of fish. In this study, we identify two developmentally regulated MyoHC gene transcripts (named Eggs22 and Eggs24) in carp (Cyprinus carpio) and characterise their expression patterns during embryonic and larval development. The transcripts showed an identical temporal pattern of expression commencing 22 h post-fertilisation (18 degrees C incubation temperature), coincident with the switch from exclusive expression of genes for beta-actin to expression of genes for both beta- and alpha-actin, and continuing for 2 weeks post-hatching. No expression of these myosin transcripts was detected in juvenile or adult carp. Wholemount in situ hybridisation showed that both transcripts are expressed initially in the rostral region of the developing trunk and progress caudally. Both are expressed in the developing pectoral fin and protractor hyoideus muscles. However, the muscles of the lower jaw express only the Eggs22 transcript. No expression of either transcript was detected in cardiac or smooth muscle. A distinct chevron pattern of expression was observed in the myotomal muscle. This was shown to be caused by localisation of the mRNAs to the myoseptal regions of the fibres, the sites of new sarcomere addition during muscle growth, suggesting transport of MyoHC mRNA transcripts. The 3′ untranslated region of the Eggs24 transcript contains a 10 base pair motif (AAAATGTGAA) which is shown to be also present in the 3′ untranslated regions of MyoHC genes from a wide range of species. Possible reasons for the need for developmental isoforms of myosin heavy chain isoforms are discussed.

Fibroblast growth factor receptors: lessons from the genes

The fibroblast growth factor receptors (FGFRs) are a family of transmembrane tyrosine kinases involved in signalling via interactions with the family of fibroblast growth factors (FGFs). Genetic findings have provided a way of dissecting these interactions. Mutations in three members of the FGFR family have been found in patients with birth defects involving craniosynostosis (premature fusion of the cranial sutures) or skeletal abnormalities. Analyses of the spectrum of mutations found predict that many of them will result in ligand-independent activation of the receptors. Amino acids have also been identified that are likely to be important in determining the specificity of FGFR-FGF interactions.

Craniosynostosis associated with FGFR3 pro250arg mutation results in a range of clinical presentations including unisutural sporadic craniosynostosis

Several mutations involving the fibroblast growth factor receptor (FGFR) gene family have been identified in association with phenotypically distinct forms of craniosynostosis. One such point mutation, resulting in the substitution of proline by arginine in a critical region of the linker region between the first and second immunoglobulin-like domains, is associated with highly specific phenotypic consequences in that mutation at this point in FGFR1 results in Pfeiffer syndrome and analogous mutation in FGFR2 results in Apert syndrome. We now show that a much more variable clinical presentation accompanies analogous mutation in the FGFR3 gene. Specifically, mental retardation, apparently unrelated to the management of the craniosynostosis, appears to be a variable clinical consequence of this FGFR3 mutation.

A recurrent mutation, ala391glu, in the transmembrane region of FGFR3 causes Crouzon syndrome and acanthosis nigricans

Mutations in the fibroblast growth factor receptor 2 (FGFR2) gene have previously been identified in Crouzon syndrome, an autosomal dominant condition involving premature fusion of the cranial sutures. Several different missense and other mutations have been identified in Crouzon syndrome patients, clustering around the third immunoglobulin-like domain. We report here the identification of a mutation in the transmembrane region of FGFR3, common to three unrelated patients with classical Crouzon syndrome and acanthosis nigricans, a dermatological condition associated with thickening and abnormal pigmentation of the skin. The mutation within the FGFR3 transcript was determined by direct sequencing as a specific gcg to gag transversion, resulting in an amino acid substitution ala391glu within the transmembrane region.

Spectrum of craniosynostosis phenotypes associated with novel mutations at the fibroblast growth factor receptor 2 locus

The causative relationship between several of the syndromic forms of craniosynostosis and mutations in the fibroblast growth factor receptor (FGFR) loci is now well established. However, within the group of patients with craniosynostosis, there are several families and sporadic cases whose clinical features differ in variable degrees from the classically described syndromes of craniosynostosis. In this communication we present novel FGFR2 mutations associated with a spectrum of craniosyostosis phenotypes in 4 sporadic cases and in one family in which craniosynostosis segregates. The mutation and phenotype data presented emphasise the clinical variability of mutations at this locus and underline the plasticity of the phenotype-genotype relationship in this important group of congenital malformation syndromes. Mutations found were tyrosine 105 to cysteine, glycine 338 to glutamic acid, serine 351 to cysteine and glycine 384 to arginine. These are the first reported mutations in the first immunoglobulin-like loop (tyrosine 105 to cysteine) and the transmembrane domain (glycine 384 to arginine) of FGFR2, providing further insights into the mechanism of abnormal receptor function in FGFR2 mutations.

Friedreich's ataxia: a defect in signal transduction?

We have previously assigned the mutation causing Friedreich's ataxia (FRDA) to 9q13 by genetic linkage and fluorescent in situ hybridization analysis, and identified recombination events which position the gene centromeric to D9S5. We report here the extension of a yeast artificial chromosome contig to span the 860 kb interval immediately proximal to this marker, which includes the D9S886 and D9S887/888 loci reported to flank the FRDA locus, and the construction of a high resolution cosmid contig initiated from the D9S888 locus. Exon trapping and cDNA library screening strategies have resulted in the isolation of a candidate gene which traverses the centromeric boundary of the FRDA critical region. The gene spans a genomic interval greater than 220 kb with at least two of the coding exons located proximal to the D9S887/888 loci. Expression is complex, with multiple transcripts detected in a variety of tissues and evidence of alternative splicing and developmental control. The predicted amino acid sequence for the 2.7 kb transcript reported here shows a marked homology to the deduced amino acid sequence of the Saccharomyces cerevisiae MSS4 protein, proposed to function within the phosphoinositide cycle, suggesting a potential role for the human homologue in signal transduction. Whilst no evidence for mutation has been detected in this transcript, the sequence represents only one of the shorter alternatively spliced species identified by Northern analysis and direct sequencing. This gene remains a strong candidate for FRDA.

The regulation of pulmonary immunity

No evidence has emerged which suggests that the principles of immunity derived from studies on cells from other body sites are contradicted in the lung and its associated lymphoid tissue. What is clear, however, is that the environment dictates the types of cells, their relationship to one another, and what perturbing events will set in motion either the development of an "active" immune response or tolerance. Investigating mechanisms for the development of lung immunity has increased our understanding of how human diseases develop and is continuing to suggest new ways to manipulate pulmonary immune responses. Demonstration that lung cells regulate both nonspecific inflammation and immunity through the expression of adhesion molecules and the secretion of cytokines offers hope for ways to design more effective vaccines, enhance microbial clearance in immunosuppressed hosts, and to suppress manifestations of immunologically mediated lung disease. Important lung diseases targeted for intensive research efforts in the immediate future are tuberculosis, asthma, and fibrotic lung disease. Perhaps even the common cold might be conquered. Considering the pace of current research on lung immunity, it may not be too ambitious to predict that these diseases may be conquered in the next decade.

Physical evidence for the position of the Friedreich's ataxia locus FRDA proximal to D9S5

Orientation of the Friedreich's ataxia locus (FRDA) with respect to D9S15 and D9S5 has proved critical to the design of subsequent cloning strategies. The rarity of recombination events between FRDA and these markers, originally used to determine assignment to human chromosome region 9q13-->q21.1, has necessitated the instigation of physical mapping studies to determine order and, hence, the precise location of the disease gene. Simultaneous fluorescence in situ hybridisation using cosmid clones located in close proximity to the ends of a 1.2-Mb yeast artificial chromosome clone extending into the FRDA candidate region provides physical evidence for the order of the marker loci to be cen-D9S202-D9S5-D9S15-qter. The possibility that a pericentric inversion, occurring naturally in approximately 1% of the normal population, may affect the order of markers within this region has been eliminated. Considered in association with the interpretation of a recombination event detected in a single affected individual, these data indicate that the FRDA locus is located proximal to D9S5.

Genetic recombination events which position the Friedreich ataxia locus proximal to the D9S15/D9S5 linkage group on chromosome 9q

The absence of recombination between the mutation causing Friedreich ataxia and the two loci which originally assigned the disease locus to chromosome 9 has slowed attempts to isolate and characterize the genetic defect underlying this neurodegenerative disorder. A proximity of less than 1 cM to the linkage group has been proved by the generation of high maximal lod score (Z) to each of the two tightly linked markers D9S15 (Z = 96.69; recombination fraction [theta] = .01) and D9S5 (Z = 98.22; theta = .01). We report here recombination events which indicate that the FRDA locus is located centromeric to the D9S15/D9S5 linkage group, with the most probable order being cen-FRDA-D9S5-D9S15-qter. However, orientation of the markers with respect to the centromere, critical to the positional cloning strategy, remains to be resolved definitively.

Identification of CpG islands in a physical map encompassing the Friedreich's ataxia locus

The Friedreich's ataxia locus has been previously assigned to chromosome 9q 13-21.1 by the demonstration of tight linkage to two anonymous DNA markers. MCT112 (Z greater than 80, theta = 0) and DR47 (Z greater than 50, theta = 0). The absence of recombination between these three loci has prevented the resolution of gene/probe order in this region, impeding strategies for gene isolation. We report physical mapping over a 4-Mb genomic interval, linking the markers MCT112 and DR47 on a common 460-kb NotI fragment and identifying 11 CpG islands in the 1.7-Mb interval most likely to contain the Friedreich's ataxia locus. Four of these islands were detected only by analysis of three YAC clones spanning a 700-kb interval including the MCT112/DR47 cluster. Without clear evidence of the precise location of the disease locus from recombination events, each of these regions must be considered as specifying a potential "candidate" sequence for the mutated gene.

Prenatal diagnosis of Friedreich ataxia

Friedreich ataxia is a progressive neurodegenerative disorder affecting the peripheral and central nervous systems. One in 50,000 of the population are affected by this recessively inherited disorder, with onset usually before puberty. The recent localization of the disease locus to chromosome 9 has made it possible to provide genetic counselling to families with at least one affected child. Tight linkage of the disease mutation to an anonymous DNA marker MCT112 (D9S15) has been shown with a pairwise lod score of 36.1 at 0 = 0. We report here the first prenatal diagnosis in Friedreich ataxia. Using MCT112 and the confidence interval approach, we have calculated risks for a fully informative family with one affected sib.

Cardiopulmonary adaptation at rest and during exercise 10 years after Mustard atrial repair for transposition of the great arteries

Discordance exists between apparently reduced systemic right ventricular function and the reported asymptomatic state of many patients after atrial repair for transposition of the great arteries. To evaluate this clinical observation, cardiopulmonary response to exercise in 17 asymptomatic patients with no significant postoperative hemodynamic abnormalities was assessed by upright bicycle ergometry according to a modified Jomes protocol 11.5 +/- 1.5 years after Mustard atrial repair. Seventeen age- and sex-matched normal adolescents constituted the control group. Incremental exercise was performed to determine maximum work capacity, heart rate, blood pressure, oxygen saturation, and minute ventilation. Cardiac output was computed at rest and during steady-state exercise by a carbon dioxide rebreathing method at 50% of the maximum workload achieved during incremental exercise. Height and weight were similar in patients and controls (p greater than .05). Resting pulmonary function variables were normal in all subjects. At peak exercise, respiratory quotient was greater than 1 in both patients and controls (1.12 +/- 0.09 and 1.09 +/- 0.08 respectively, p greater than .05). Patients achieved a lower peak heart rate (172 +/- 14 vs 185 +/- 11 beats/min, p less than .01), lower maximum work capacity (2.3 +/- 0.6 vs 3.3 +/- 0.7 W/kg, p less than .01). The ratio of minute ventilation at peak exercise to maximum resting voluntary ventilation was normal (less than or equal to 80%) in both groups. The ventilatory equivalent for oxygen was similar at rest, but significantly higher in patients than in control subjects at peak exercise (42 +/- 7 vs 36 +/- 5, p less than .006).(ABSTRACT TRUNCATED AT 250 WORDS)

Variant angina in an 11 year old boy

Variant angina is a syndrome in which ischemic cardiac pain occurs with ST segment elevation. The syndrome is due at least in part to coronary vasospasm. Although well documented in adults, there are no known reports of this syndrome in children. The clinical, electrocardiographic and echocardiographic findings in an 11 year old boy with variant angina are reported.

Rib cage and abdominal contributions to ventilatory response to CO2 in infants

We have measured the ventilatory response to inhaled CO2 of six newborn infants in rapid-eye-movement (REM) and non-REM (NREM) sleep. Ventilatory responses were measured using the Read rebreathing technique. The response was further partitioned into the volume contributions of the rib cage and abdominal compartment using the respiratory inductance plethysmograph. Sleep state was defined by electroencephalogram, electrooculogram, and behavioral criteria. In NREM sleep, there was a highly significant linear correlation between both tidal volume (VT) and instantaneous minute ventilation (VI) with CO2. Among infants, the slope of VT varied from 1.0 to 0.34 ml X Torr-1 X kg-1. However, these differences were largely due to differences in rib cage contribution, which varied from 0.56 to -0.08 ml X Torr-1 X kg-1. The abdominal contribution was similar among infants (0.41-0.56 ml X Torr-1 X kg-1). In REM, the slopes of VI were less steep than in NREM, with greater breath-to-breath variability. Slopes of VT also tended to be lower. The abdominal responses were similar to those in NREM, whereas the rib cage response was low and negative in three studies. We conclude that the slope of the CO2 response curve is primarily determined by the extent of rib cage recruitment.

Effects of a face mask and pneumotachograph on breathing in sleeping infants

The effect of facial attachments on breathing was measured by respiratory induction plethysmography (RIP) during quiet sleep in 32 studies in 18 infants. The addition of a face mask plus pneumotachograph led to an increase in tidal volume (VT) (22.0 +/- 13.5%, p less than 0.01) during 5-min sleep studies when compared to measurements using RIP alone. Applying only the mask rim also led to an increase in VT (14.6 +/- 3.1%, p less than 0.05). A significant increase in VT was noted in 3 of 6 infants studied when a lightweight cardboard ring was in place perinasally. Respiratory frequency fell significantly in the mask/pneumotachograph group (-5.9 +/- 10.0%, p less than 0.05) and with the mask rim (-7.4 +/- 8.8%, p less than 0.01), but there was individual infant variation. Minute ventilation rose significantly (19.1 +/- 16.9%, p less than 0.01) only with the addition of the mask and pneumotachograph. Instrument deadspace can account for some of the increase in VT noted, but in its absence, sensory stimulation of the trigeminal area can augment tidal breathing.

Effect of acute induced metabolic alkalosis on 800-m racing time

Six trained middle-distance runners wer studied under alkalotic (NaHCO3 ingestion), placebo (CaCO3 ingestion), and control conditions to determine the effect of an acute induced metabolic alkalosis on time to run an 800-m race. Pre-exercise, following NaHCO3 ingestion, pH and standard [HCO3-] were significantly higher. In the alkalotic condition, subjects ran faster (2.9 s) and the corresponding post-exercise values for blood [lactate] and extracellular H+ were higher than in the control and placebo conditions, suggesting an increased anaerobic energy contribution. These results support the speculation that the increase in extracellular buffering following NaHCO3 ingestion facilitated H+ efflux from the cells of working muscle, thereby delaying the decrease in intracellular pH and postponing fatigue. It is concluded that the ingestion of NaHCO3 by trained middle-distance runners prior to an 800-m race has an ergogenic benefit.