Thermoelectric properties of PbTe-based materials driven near the ferroelectric phase transition from first principles

The thermoelectric figure of merit, ZT, is a dimensionless parameter used to characterise the efficiency of a thermoelectric material. One of the most common techniques to improve ZT is to suppress lattice thermal conductivity via nanostructuring. However, this approach often comes with the cost of reduced electrical conductivity and Seebeck coefficient, resulting in only modest increases to ZT. Using the first principles Boltzmann transport framework, we show that driving PbTe-based materials to the verge of the soft mode (ferroelectric) phase transition could be a powerful strategy to reduce their lattice thermal conductivity while potentially preserving the electrical properties beneficial for a large ZT. The proposed concept is based on the induction of considerably softened zone-centre transverse optical modes, increasing their anharmonic coupling with low-frequency heatcarrying acoustic phonons and reducing phonon lifetimes at all frequencies. We illustrate this concept by applying biaxial tensile (001) strain to PbTe and its alloys with PbSe; and by alloying PbTe with a rhombohedral material, GeTe, reducing the lattice thermal conductivity by a factor of 2−3 compared to PbTe. Furthermore, by tuning the chemical composition of Pb1−xGexTe alloys, we also investigate the roles of proximity to the phase transition, mass disorder, and phase of the alloy in reducing the lattice thermal conductivity. Finally, we take the first steps towards a fully ab initio calculation of the figure of merit of PbTe-based materials near the phase transition by considering electron-phonon interactions, and find fair agreement between the calculated electronic mobility of PbTe and experiment. Due to certain symmetry forbidden electron-phonon coupling, we anticipate that our outlined approach may not degrade electronic properties beneficial for a large ZT. This proposed concept is general and offers a promising new strategy to potentially increase thermoelectric efficiency

Ocular Demodex folliculorum: prevalence and associated symptoms in an Irish population

Purpose To investigate the prevalence of ocular Demodex folliculorum (DF) in an Irish population. To validate a modified Ocular Surface Disease Index questionnaire and employ it to evaluate the relationship between dry eye symptoms and the presence of DF. Methods One hundred and fifty-six subjects were enrolled in an epidemiological cross-sectional prevalence study. Each subject completed a novel questionnaire on ocular symptoms and was assessed for the presence of DF. Data was analysed to assess prevalence and to search for significant links between each symptom and DF. Results An overall prevalence of 68% was found. Total mean number of DF found on microscopic examination was 3.83 mites per subject (range 0–25). The presence of symptoms was higher among individuals with DF (P = 0.04). Itch was found to be the symptom most significantly associated with the presence and number of DF (P = 0.025 and P = 0.035, respectively). The questionnaire showed good internal consistency (Cronbach’s alpha; a[0.7) and good reliability (Intra-class Correlation Co-efficient; ICC[0.7). The sensitivity and specificity of a positive symptom result using the questionnaire were 70.8% and 46.9%, respectively. Conclusion There is a strong association between the prevalence of DF and symptoms, in particular itchy eyes. However, not all patients with DF will be symptomatic. The newly developed questionnaire is a reliable instrument for measuring change in symptoms over a period of time and suitable for observing patient reported outcomes in interventional treatment studies

Car-Park Management using Wireless Sensor Networks

A complete wireless sensor network solution for car-park management is presented in this paper. The system architecture and design are first detailed, followed by a description of the current working implementation, which is based on our DSYS25z sensing nodes. Results of a series of real experimental tests regarding connectivity, sensing and network performance are then discussed. The analysis of link characteristics in the car park scenario shows unexpected reliability patterns which have a strong influence on MAC and routing protocol design. Two unexpected link reliability patterns are identified and documented. First, the presence of the objects (cars) being sensed can cause significant interference and degradation in communication performance. Second, link quality has a high temporal correlation but a low spatial correlation. From these observations we conclude that a) the construction and maintenance of a fixed topology is not useful and b) spatial rather than temporal message replicates can improve transport reliability

The Prevalence of Demodex Folliculorum on Eyelashes of Symptomatic and Asymptomatic Normal Patients

Purpose To examine the prevalence of Demodex Folliculorum (DF) on the eyelashes of symptomatic and asymptomatic patients. DF is an eight legged ectoparasite present in humans. It is most commonly found on the face; cheeks, nose, chin and eyelashes. Ocular symptoms of DF infestation on the eyelashes include itching, dryness, surface irritation, burning, foreign body sensation, photophobia and reduced vision1 Method Students and patients of the National Optometry Centre (NOC) (n=54), aged 19 – 78 years of age were assessed and sub-divided into 4 groups; Group (1) Control (n=12), Group (2) Signs, no symptoms (n = ?), Group (3) Symptoms, no signs (n = ?) and Group (4) Signs and symptoms (n = ?). Each subject completed a novel DF questionnaire on ocular symptoms and lifestyle. Habitual distance visual acuity was assessed and a slit lamp examination was conducted. 8 lashes – 2 from each eyelid were manipulated and epilated for microscopic examination. Presence of DF was noted and adult DF count was recorded using the modified Coston method2. Results A two-way ANOVA was used to analyse the prevalence of DF (significance level p ≤ 0.05). The DF count significantly increased with age (p = 0.000), contact lens wear (p = 0.037), skin conditions (p = 0.025) and frequency of cleaning pillow case (p = 0.005). There was no significant link (p ≥ 0.05) between the DF count and gender, wearing make-up, allergies, the method of washing and drying pillow cases, method and frequency of lid hygiene routine. A two-way ANOVA was also used to analyse the age and lifestyle of patients who were more symptomatic (significance level p ≤ 0.05). Patient were more symptomatic with age (p = 0.000), contact lens wear (p = 0.032), less frequent lid hygiene routine (p = 0.001), method of lid hygiene (p = 0.000), less frequent pillow case cleaning (p = 0.032), air dried pillow case (p = 0.025), allergies (p = 0.000), skin conditions (p = 0.011), wearing mascara (p = 0.000). Conclusion The prevalence of DF and symptoms increase with age, contact lens wear, skin conditions and frequency of cleaning pillow cases. Whilst patients with less frequent lid hygiene routine, different method of lid hygiene routine, allergies and who air dried their pillow case were more symptomatic, the DF count did not increase. Therefore some patients can be symptomatic without an increase in DF count. Further data collection is ongoing

The Efficacy of Warm Compresses in the Treatment of Meibomian Gland Dysfunction and Demodex Folliculorum Blepharitis

Purpose: To investigate and compare the effect of warm compresses on meibomian gland dysfunction and Demodex folliculorum blepharitis. Methods: Forty-two subjects (13 males, 29 females; mean age of 56.45 years) enrolled and completed the two-month warm compress treatment study. Three warm compress therapies were compared: Warm face cloth, MGDRx EyeBag® and OPTASETM Moist Heat Mask. Subjects attended for four visits: baseline, two weeks, four weeks, and eight weeks. Subjective symptoms, osmolarity, non-invasive tear break-up time, ocular surface staining, Schirmer I test, meibum expressibility and clarity, and eyelash manipulation and epilation to assess for the presence of Demodex folliculorum, were measured at each visit. Results: Meibomian gland dysfunction, based on a composite score of meibum quality and expressibility, reduced significantly with the MGDRx EyeBag® and the OPTASETM Moist Heat Mask (p \u3c .05). There was no significant difference in efficacy for treating meibomian gland dysfunction between the two devices (p = .29). No improvement in meibomian gland dysfunction was detected with the warm face cloth. Only the OPTASETM Moist Heat Mask significantly reduced the quantity of Demodex folliculorum over eight-weeks of treatment (p = .036, only baseline to week eight significant p = .008). Symptoms and ocular surface staining improved significantly in all three groups (p \u3c .05). There was no significant change observed in osmolarity, non-invasive tear break-up time or Schirmer I test within each group (p \u3e .05, respectively). Conclusion: TheMGDRx EyeBag® and the OPTASETM Moist Heat Mask exhibited superior efficacy in treating signs and symptoms of meibomian gland dysfunction, compared to the use of a warm face cloth, over the eight-week period. The OPTASETM Moist Heat Mask demonstrated dual therapeutic abilities, treating both meibomian gland dysfunction and Demodex folliculorum blepharitis. Repeated application of heat for the treatment ofmeibomian gland dysfunctionmay continue to present a good home-remedy option for patients

Issues associated with planning, implementing, managing and operating public transport projects in Ireland

Whilst considering the context to which public transport is planned in Ireland and internationally, the research has been concerned with studying the methodology and the roles of key stakeholders for the planning, implementation, management and operation of public transport projects in order to gauge the efficiency and suitability of the Irish planning process in relation to our international counterparts The paper will present principal findings from structured interviews undertaken with key stakeholders involved in the Irish process and will provide a basis for debating the issues raised as a consequence of these interviews.. Key issues raised include: 1) the possible complexity of the planning process in Ireland, 2) the role of political agendas in the decision making process; and, 3) the governance and institutional arrangements for planning public transport projects in Ireland in contrast to other international countries