Wettability and confinement size effects on stability of water conveying nanotubes.

This study investigates the wettability and confinement size effects on vibration and stability of water conveying nanotubes. We present an accurate assessment of nanotube stability by considering the exact mechanics of the fluid that is confined in the nanotube. Information on the stability of nanotubes in relation to the fluid viscosity, the driving force of the fluid flow, the surface wettability of the nanotube, and the nanotube size is missing in the literature. For the first time, we explore the surface wettability dependence of the nanotube natural frequencies and stability. By means of hybrid continuum-molecular mechanics (HCMM), we determined water viscosity variations inside the nanotube. Nanotubes with different surface wettability varying from super-hydrophobic to super-hydrophilic nanotubes were studied. We demonstrated a multiphase structure of nanoconfined water in nanotubes. Water was seen as vapor at the interface with the nanotube, ice shell in the middle, and liquid water in the nanotube core. The average velocity of water flow in the nanotube was obtained strongly depend on the surface wettability and the confinement size. In addition, we report the natural frequencies of the nanotube as functions of the applied pressure and the nanotube size. Mode divergence and flutter instabilities were observed, and the activation of these instabilities strongly depended on the nanotube surface wettability and size. This work gives important insights into understanding the stability of nanotubes conveying fluids depending on the operating pressures and the wettability and size of confinement. We revealed that hydrophilic nanotubes are generally more stable than hydrophobic nanotubes when conveying fluids.

Aquatic animal colors and skin temperature: Biology's selection for reducing oceanic dolphin's skin friction drag.

There is currently a growing interest in the area of drag reduction. In this work, the thermal effects of body color of some species of aquatics like Orcas and Dusky dolphins are investigated with respect to their swimming routes and geometric and behavioral characteristics. Considering the marine and atmospheric characteristics of these aquatics' routes, a thermal analysis is performed. The surrounding fluxes including the water flux, sun irradiation, and core temperature are considered in an energy balance to determine the skin temperature of the top side of the animal/organism's body. To study the effects of color on the surface temperature of the aquatic species, an experiment is carried out in the water on a flat plate with black and white color. Applying a turbulent analytical solution for heated boundary layers, it will be shown that the black color on the top of the bodies of these marine organisms is very efficient in terms of skin drag reduction. Moreover, to investigate the effects of the temperature on underwater skin friction drag reduction, the turbulent flow is simulated around a flat plate and a 2- dimensional modeled Killer whale at different temperatures. The results show that the top black body color of Orca and Dusky dolphin decreases their skin friction drag by 7%. This study will also provide the reason for this evolution of color scheme of other extremely fast marine animals, such as billfish, whales, and sharks. This method of drag reduction can be considered as one of the effective factors in skin drag reduction of underwater robots.

Primary headache disorders in the adult general population of Pakistan - a cross sectional nationwide prevalence survey.

BACKGROUND: The large geographical gaps in our knowledge of the prevalence and burden of headache disorders include almost all of Eastern Mediterranean Region (EMR). We report a nationwide population-based study in Pakistan, an EMR country with the sixth largest population in the world, conducted as a project within the Global Campaign against Headache. METHODS: We surveyed six locations from the four provinces of Pakistan: Punjab, Sindh, Khyber Pakhtunkhwa and Baluchistan. We randomly selected and visited rural and urban households in each. One adult member (18-65 years) of each household, also randomly selected, was interviewed by a trained non-medical interviewer from the same location using a previously-validated structured questionnaire translated into Urdu, the national language. We estimated 1-year prevalences of the headache disorders of public-health importance and examined their associations with demographic variables using multivariate analysis. RESULTS: There were 4223 participants (mean age 34.4 ± 11.0 years; male 1957 [46.3%], female 2266 [53.7%]; urban 1443 [34.2%], rural 2780 [65.8%]). Participation proportion was 89.5%. Headache in the previous year was reported by 3233 (76.6% [95% CI: 75.3-77.8%]). The age- and gender-adjusted 1-year prevalence of migraine was 22.5% [21.2-23.8%] (male 18.0% [16.8-19.2%], female 26.9% [25.6-28.2%]), of tension-type headache (TTH) 44.6% [43.1-46.1%] (male 51.2% [49.7-52.7%], female 37.9% [36.4-39.4%]), of probable medication-overuse headache 0.7% [0.5-1.0%] (male 0.7% [0.5-1.0%], female 0.8% [0.5-1.1%]) and of other headache on ≥15 days/month 7.4% [6.6-8.2%] (male 4.4% [3.8-5.0%], female 10.4% [9.5-11.3%]). Migraine was more prevalent in females by a factor of 3:2 although this association barely survived (P = 0.039) after correcting for other factors. TTH was more prevalent in males by about 4:3 (P = 0.026). All headache and migraine were age-related, peaking in the age group 40-49 years; TTH peaked a decade earlier. Higher education (P = 0.004) and income (P = 0.001) were negatively associated with prevalence of migraine. CONCLUSION: With three quarters of its population affected, headache disorders must be on the public-health agenda of Pakistan. Worldwide, these disorders are the third leading cause of disability; information from specific enquiry into the burden attributable to headache disorders in this country is needed to inform health policy and priority-setting, and will be reported soon.

Cataract extraction and patient vision-related quality of life: a cohort study.

AIMS: Cataract surgery is one of the most common surgeries performed, but its overuse has been reported. The threshold for cataract surgery has become increasingly lenient; therefore, the selection process and surgical need has been questioned. The aim of this study was to evaluate the changes associated with cataract surgery in patient-reported vision-related quality of life (VR-QoL). METHODS: A prospective cohort study was conducted. Consecutive patients referred to cataract clinics in an NHS unit in Scotland were identified. Those listed for surgery were invited to complete a validated questionnaire (TyPE) to measure VR-QoL pre- and post-operatively. TyPE has five different domains (near vision, distance vision, daytime driving, night-time driving, and glare) and a global score of vision. The influence of pre-operative visual acuity (VA) levels, vision, and lens status of the fellow eye on changes in VR-QoL were explored. RESULTS: A total of 320 listed patients were approached, of whom 36 were excluded. Among the 284 enrolled patients, 229 (81%) returned the questionnaire after surgery. Results revealed that the mean overall vision improved, as reported by patients. Improvements were also seen in all sub-domains of the questionnaire. CONCLUSION: The majority of patients appear to have improvement in patient-reported VR-QoL, including those with good pre-operative VA and previous surgery to the fellow eye. VA thresholds may not capture the effects of the quality of life on patients. This information can assist clinicians to make more informed decisions when debating over the benefits of listing a patient for cataract extraction.