Low Friction Flows of Liquids at Nanopatterned Interfaces

With the recent important development of microfluidic systems, miniaturization of flow devices has become a real challenge. Microchannels, however, are characterized by a large surface to volume ratio, so that surface properties strongly affect flow resistance in submicrometric devices. We present here results showing that the concerted effect of wetting . properties and surface roughness may considerably reduce friction of the fluid past the boundaries. The slippage of the fluid at the channel boundaries is shown to be drastically increased by using surfaces that are patterned at the nanometer scale. This effect occurs in the regime where the surface pattern is partially dewetted, in the spirit of the 'superhydrophobic' effects that have been recently discovered at the macroscopic scales. Our results show for the first time that, in contrast to the common belief, surface friction may be reduced by surface roughness. They also open the possibility of a controlled realization of the 'nanobubbles' that have long been suspected to play a role in interfacial slippag

All-sky search for continuous gravitational waves from isolated neutron stars in the early O3 LIGO data

We report on an all-sky search for continuous gravitational waves in the frequency band 20-2000 Hz and with a frequency time derivative in the range of [-1.0,+0.1]×10-8 Hz/s. Such a signal could be produced by a nearby, spinning and slightly nonaxisymmetric isolated neutron star in our Galaxy. This search uses the LIGO data from the first six months of Advanced LIGO's and Advanced Virgo's third observational run, O3. No periodic gravitational wave signals are observed, and 95% confidence-level (C.L.) frequentist upper limits are placed on their strengths. The lowest upper limits on worst-case (linearly polarized) strain amplitude h0 are ∼1.7×10-25 near 200 Hz. For a circularly polarized source (most favorable orientation), the lowest upper limits are ∼6.3×10-26. These strict frequentist upper limits refer to all sky locations and the entire range of frequency derivative values. For a population-averaged ensemble of sky locations and stellar orientations, the lowest 95% C.L. upper limits on the strain amplitude are ∼1.4×10-25. These upper limits improve upon our previously published all-sky results, with the greatest improvement (factor of ∼2) seen at higher frequencies, in part because quantum squeezing has dramatically improved the detector noise level relative to the second observational run, O2. These limits are the most constraining to date over most of the parameter space searched

All-sky, all-frequency directional search for persistent gravitational waves from Advanced LIGO’s and Advanced Virgo’s first three observing runs

We present the first results from an all-sky all-frequency (ASAF) search for an anisotropic stochastic gravitational-wave background using the data from the first three observing runs of the Advanced LIGO and Advanced Virgo detectors. Upper limit maps on broadband anisotropies of a persistent stochastic background were published for all observing runs of the LIGO-Virgo detectors. However, a broadband analysis is likely to miss narrowband signals as the signal-to-noise ratio of a narrowband signal can be significantly reduced when combined with detector output from other frequencies. Data folding and the computationally efficient analysis pipeline, {\tt PyStoch}, enable us to perform the radiometer map-making at every frequency bin. We perform the search at 3072 {\tt{HEALPix}} equal area pixels uniformly tiling the sky and in every frequency bin of width $1/32$~Hz in the range $20-1726$~Hz, except for bins that are likely to contain instrumental artefacts and hence are notched. We do not find any statistically significant evidence for the existence of narrowband gravitational-wave signals in the analyzed frequency bins. Therefore, we place $95\%$ confidence upper limits on the gravitational-wave strain for each pixel-frequency pair, the limits are in the range $(0.030 - 9.6) \times10^{-24}$. In addition, we outline a method to identify candidate pixel-frequency pairs that could be followed up by a more sensitive (and potentially computationally expensive) search, e.g., a matched-filtering-based analysis, to look for fainter nearly monochromatic coherent signals. The ASAF analysis is inherently independent of models describing any spectral or spatial distribution of power. We demonstrate that the ASAF results can be appropriately combined over frequencies and sky directions to successfully recover the broadband directional and isotropic results

Search for gravitational waves associated with gamma-ray bursts detected by Fermi and Swift during the LIGO–Virgo run O3b

We search for gravitational-wave signals associated with gamma-ray bursts (GRBs) detected by the Fermi and Swift satellites during the second half of the third observing run of Advanced LIGO and Advanced Virgo (2019 November 1 15:00 UTC–2020 March 27 17:00 UTC). We conduct two independent searches: a generic gravitational-wave transients search to analyze 86 GRBs and an analysis to target binary mergers with at least one neutron star as short GRB progenitors for 17 events. We find no significant evidence for gravitational-wave signals associated with any of these GRBs. A weighted binomial test of the combined results finds no evidence for subthreshold gravitational-wave signals associated with this GRB ensemble either. We use several source types and signal morphologies during the searches, resulting in lower bounds on the estimated distance to each GRB. Finally, we constrain the population of low-luminosity short GRBs using results from the first to the third observing runs of Advanced LIGO and Advanced Virgo. The resulting population is in accordance with the local binary neutron star merger rate

A questionnaire survey of endodontic practice profile among dentists in Hong Kong

Objectives. The present study aimed to gather information on the prevailing endodontic practice of general dental practitioners in Hong Kong. Methods. A cross-sectional postal survey was conducted on 1167 members of the Hong Kong Dental Association in 2001. Information about the materials and techniques used in endodontic treatment was collected. Results. A total of 369 replies were received, of which 343 with valid responses were analyzed, which accounted for 29% of the population surveyed. About half of the respondents (56%) performed one to five endodontic treatments weekly. Over one quarter (28%) routinely used a rubber dam in endodontic treatment. A wide variety of instruments were used for root canal preparation; stainless steel hand files being the most popular (89%). Rotary nickel-titanium instrumentation was practiced by 21% of respondents. Sodium hypochlorite irrigation and calcium hydroxide dressings were used by 63% and 43% of respondents, respectively. Most general dental practitioners (87%) obturated root canals with lateral compaction of gutta-percha. Single-visit treatment was not common; less than 20% of respondents practiced it to a limited extent. Conclusion. Within the limits and the low response rate to the present survey, the results suggest that Hong Kong general dental practitioners treat root canals using techniques and materials commonly taught in dental schools, often as multiple-visit treatments. The utilization of rubber dams in root canal treatment remains low

Reliability and validity of the euthanasia attitude scale (EAS) for Hong Kong medical doctors

This study aimed to examine the reliability and validity of the Euthanasia Attitude Scale (EAS) in Hong Kong medical doctors. A total of 107 medical doctors (61.7% men) participated in a survey at clinical settings in 2008. The 21-item EAS was used to assess their attitudes toward euthanasia. The mean (standard deviation) and median of the EAS were 63.60 (60.31) and 63.00. Total EAS scores correlated well with "Ethical Considerations," "Practical Considerations," and "Treasuring Life" (Spearman ρ =.37-.96, P <.001) but not "Naturalistic Beliefs." The construct validity of the 3-factor model was appropriate (Kaiser-Meyer-Olkin [KMO] value = 0.90) and showed high internal consistency (Cronbach α =.79-.92). Euthanasia Attitude Scale may be a reliable and valid measure for assessing the attitudes toward euthanasia in medical professionals. © The Author(s) 2010.link_to_subscribed_fulltex