Twist-Bend Nematic Glasses: The Synthesis and Characterisation of Pyrene-based Nonsymmetric Dimers

A selection of pyrene-based liquid crystal dimers have been prepared, containing either methylene-ether or diether linked spacers of varying length and parity. All the diether linked materials, CBOnO.Py (n=5, 6, 11, 12), exhibit conventional nematic and smectic A phases, with the exception of CBO11O.Py which is exclusively nematic. The methylene-ether linked dimer, CBnO.Py, with an even-membered spacer (n=5) was solely nematogenic, but odd-members (n=6, 8, 10) exhibited both nematic and twist-bend nematic phases. Replacement of the cyanobiphenyl fragment by cyanoterphenyl giving CT6O.Py, gave elevated melting and nematic-isotropic transition temperatures, and SmA and SmC_A phases were observed on cooling the nematic phase. Intermolecular face-to-face associations of the pyrene moieties drive glass formation, and all these materials have a glass transition temperature at or above room temperature. The stability of the glassy twist-bend nematic phase allowed for its study using AFM, and the helical pitch length, P_TB, was measured as 6.3 and 6.7 nm for CB6O.Py and CB8O.Py, respectively. These values are comparable to the shortest pitch of a twist-bend nematic phase measured to date.     

Role of mechanical milling on the synthesis and ionic transport properties of fast fluoride ion conducting materials

Journal of Solid State Electrochemistry - This review article presents the use of mechanical milling technique for the synthesis of a variety of fast fluoride ion conducting materials for different...     

A Pilot Survey of Vocal Health in Young Singers

The objective of this study was to determine the incidence of vocal problems in young choir singers and to correlate vocal problems with demographic and behavioral information. A questionnaire addressing vocal habits and hygiene was offered to 571 young choir singers, up to 25 years of age, who sing at least weekly; 129 (22.6%) responded. More than one-half of the respondents had experienced vocal difficulty, particularly older adolescents. Detrimental behaviors and circumstances surveyed were not reflective of the incidence of vocal difficulty, except for morning hoarseness, chronic fatigue, insomnia, and female gender after puberty. Voice care professionals should be aware that self-reported voice difficulties are common among young choral singers, especially postpubescent girls, and children with symptoms consistent with reflux (morning hoarseness) and emotional stress (insomnia). Laryngologists should communicate with choral conductors and singing teachers to enhance early identification and treatment of children with voice complaints, and to develop choral educational strategies that help decrease their incidence.     

Validity and Reliability of the Reflux Symptom Index (RSI)

Laryngopharyngeal reflux (LPR) is present in up to 50% of patients with voice disorders. Currently, there is no validated instrument that documents symptom severity in LPR. We developed the reflux symptom index (RSI), a self-administered nine-item outcomes instrument for LPR. The purpose of this investigation was to evaluate the psychometric properties of the RSI. For validity assessment, 25 patients with LPR were evaluated prospectively before and six months after b.i.d. treatment with proton pump inhibitors (PPI). Each patient completed the RSI as well as the 30-item voice handicap index (VHI). For reliability assessment, the study patients were given the RSI on two separate occasions before the initiation of treatment. Normative RSI data were derived from 25 age-matched and gender-matched controls taken from an existing database of asymptomatic individuals without any evidence of LPR. The mean RSI (+/- standard deviation) of patients with LPR improved from 21.2 (+/- 10.7) to 12.8 (+/- 10.0), and the mean VHI improved from 52.2 (+/- 24.7) to 41.5 (+/- 25.0) after 6 months of therapy (p = 0.001 and 0.065, respectively). Of the three VHI subscales (emotional, physical, functional), only the functional subscale improved significantly (p = 0.037). Patients who experienced a five point or better improvement in RSI were 11 times more likely to experience a five-point improvement in VHI (95% confidence interval = 1.7, 76.8). For reliability assessment, the first and second pretreatment RSIs were 19.9 (+/- 11.1) and 20.9 (+/- 9.6), respectively (correlation coefficient = 0.81, p < 0.001). The single-item correlation coefficients ranged from 0.41 to 0.91 (p < 0.05 for all items). The mean pretreatment RSI in patients with LPR was significantly higher than controls (21.2 versus 11.6; p < 0.001). The mean RSI of patients with LPR after 6 months of PPI therapy approached that of asymptomatic controls (p > 0.05). The RSI is easily administered, highly reproducible, and exhibits excellent construct and criterion-based validity.     

Application of the single comparator method to instrumental photon activation analysis

Journal of Radioanalytical and Nuclear Chemistry - Instrumental photon activation analysis (IPAA) is nondestructive and multi-elemental analysis method like instrumental neutron activation...     

Synthesis, DNA polymerase incorporation, and enzymatic phosphate hydrolysis of formamidopyrimidine nucleoside triphosphates

The nucleoside triphosphates of N6-(2-deoxy-alpha,beta-d-erythro-pentofuranosyl)-2,6-diamino-4-hydroxy-5-formamidopyrimidine (Fapy.dGTP) and its C-nucleoside analogue (beta-C-Fapy.dGTP) were synthesized. The lability of the formamide group required that nucleoside triphosphate formation be carried out using an umpolung strategy in which pyrophosphate was activated toward nucleophilic attack. The Klenow fragment of DNA polymerase I from Escherichia coli accepted Fapy.dGTP and beta-C-Fapy.dGTP as substrates much less efficiently than it did dGTP. Subsequent extension of a primer containing either modified nucleotide was less affected compared to when the native nucleotide is present at the 3'-terminus. The specificity constants are sufficiently large that nucleoside triphosphate incorporation could account for the level of Fapy.dG observed in cells if 1% of the dGTP pool is converted to Fapy.dGTP. Similarly, polymerase-mediated introduction of beta-C-Fapy.dG could be useful for incorporating useful amounts of this nonhydrolyzable analogue for use as an inhibitor of base excision repair. The kinetic viability of these processes is enhanced by inefficient hydrolysis of Fapy.dGTP and beta-C-Fapy.dGTP by MutT, the E. coli enzyme that releases pyrophosphate and the corresponding nucleoside monophosphate upon reaction with structurally related nucleoside triphosphates.     

A modeling concept of a mechanical system having a piecewise linear spring property for its diagnosis

Machine condition monitoring and fault diagnosis of rotating machinery are very important because of the wide use of rotating machinery in industry. Couplings and gears are used in many mechanical systems to connect elements and transmit power. The system is usually modeled as a single-degree-of-freedom system with a piecewise linear spring property, where the mass of main machine is only considered. In the present study, the dynamic behavior of a system with an unsymmetrical nonlinearity and a significant mass of the connecting part was investigated both experimentally and by numerical simulation. In the experiment, a 1/3 sub-harmonic oscillation was observed, but this oscillation was not found in the simulation using a single-degree-of-freedom system, in which the mass of the connecting part was ignored. However, when a two-degrees-of-freedom system was used that considered both the mass of the connecting part and the impact property, the 1/3 sub-harmonic oscillation was observed. Thus it is recognized that an adequate mathematical model for diagnosis in the early stage of abnormality must be selected on the basis of the mass ratio between the connecting part and the main body.