Prefrontal High Gamma in ECoG Tags Periodicity of Musical Rhythms in Perception and Imagination.

Rhythmic auditory stimuli are known to elicit matching activity patterns in neural populations. Furthermore, recent research has established the particular importance of high-gamma brain activity in auditory processing by showing its involvement in auditory phrase segmentation and envelope tracking. Here, we use electrocorticographic (ECoG) recordings from eight human listeners to see whether periodicities in high-gamma activity track the periodicities in the envelope of musical rhythms during rhythm perception and imagination. Rhythm imagination was elicited by instructing participants to imagine the rhythm to continue during pauses of several repetitions. To identify electrodes whose periodicities in high-gamma activity track the periodicities in the musical rhythms, we compute the correlation between the autocorrelations (ACCs) of both the musical rhythms and the neural signals. A condition in which participants listened to white noise was used to establish a baseline. High-gamma autocorrelations in auditory areas in the superior temporal gyrus and in frontal areas on both hemispheres significantly matched the autocorrelations of the musical rhythms. Overall, numerous significant electrodes are observed on the right hemisphere. Of particular interest is a large cluster of electrodes in the right prefrontal cortex that is active during both rhythm perception and imagination. This indicates conscious processing of the rhythms' structure as opposed to mere auditory phenomena. The autocorrelation approach clearly highlights that high-gamma activity measured from cortical electrodes tracks both attended and imagined rhythms.

Contact angles of surfactant solutions on heterogeneous surfaces.

Using Gibbs' adsorption equation and a literature isotherm, a new general model to predict the contact angle of surfactant solutions on (smooth or rough) chemically heterogeneous surfaces is constructed based on the Cassie equation. The model allows for adsorption at the liquid-vapor, solid-liquid, and solid-vapor interfaces. Solid-vapor adsorption is allowed in order to model the autophobic effect on hydrophilic surfaces. Using representative values for the coefficients which describe adsorption at each interface, model predictions for contact angles as a function of f parameters (area fractions) and surfactant concentration are made for heterogeneous surfaces made up of different materials. On smooth surfaces, the f parameters serve as weighting factors determining how to combine the effects of surfactant adsorption on each material to predict the behavior on the heterogeneous surface. Due to the non-linear nature of the model, the inclusion of a small amount of hydrophobic material has a greater effect on a predominantly hydrophilic material than vice versa, explaining the result seen in literature that a small amount of hydrophobic contamination (such as oil) significantly increases contact angle on a hydrophilic surface. The fact that even a small amount of heterogeneity can greatly change experimental results could lead to incorrect experimental conclusions about surfactant adsorption if a surface were wrongly assumed to be homogeneous. Model predictions rapidly become more complex as the number of differently wettable materials present on the surface increases. Also, an approximately equal weighting of different materials generally leads to more complex behaviors compared to heterogeneous surfaces composed largely of a single material. Rough heterogeneous surfaces follow previous results for surfactant wetting of rough homogeneous surfaces, leading to an amplification/attenuation of surfactant effects for penetrated/unpenetrated wetting, and further increasing the complexity of predictions. These potential complexities point to the importance of characterizing the heterogeneities of any surface under consideration. With proper characterization, the model described in this paper will allow for prediction of contact angles on all types of heterogeneous surfaces, and design of surfaces for specific interactions with surfactant solutions.

Understanding (sessile/constrained) bubble and drop oscillations.

The diffuse literature on drop oscillation is reviewed, with an emphasis on capillary wave oscillations of constrained drops. Based on the review, a unifying conceptual framework is presented for drop and bubble oscillations, which considers free and constrained drops/bubbles, oscillation of the surface or the bulk (i.e. center of mass) of the drop/bubble, as well as different types of restoring forces (surface tension, gravity, electromagnetic, etc). Experimental results (both from literature and from a new set of experiments studying sessile drops in cross flowing air) are used to test mathematical models from literature, using a novel whole profile analysis technique for the new experiments. The cause of oscillation (cross flowing air, vibrated surface, etc.) is seen not to affect oscillation frequency. In terms of models, simplified models are seen to poorly predict oscillation frequencies. The most advanced literature models are found to be relatively accurate at predicting frequency. However it is seen that no existing models are reliably accurate across a wide range of contact angles, indicating the need for advanced models/empirical relations especially for drops undergoing the lowest frequency mode of oscillation (the order 1 degree 1 non-axisymmetric 'bending' mode that corresponds to a lateral 'rocking' motion of the drop).

The Cassie equation: how it is meant to be used.

A review of literature shows that the majority of papers cite a potentially incorrect form of the Cassie and Cassie-Baxter equations to interpret or predict contact angle data. We show that for surfaces wet with a composite interface, the commonly used form of the Cassie-Baxter equation, cosθ(c)=f(1)cosθ-(1-f), is only correct for the case of flat topped pillar geometry without any penetration of the liquid. In general, the original form of the Cassie-Baxter equation, cosθ(c)=f(1)cosθ(1)-f(2), with f(1)+f(2)≥1, should be used. The differences between the two equations are discussed and the errors involved in using the incorrect equation are estimated to be between ~3° and 13° for superhydrophobic surfaces. The discrepancies between the two equations are also discussed for the case of a liquid undergoing partial, but increasing, levels of penetration. Finally, a general equation is presented for the transition/stability criterion between the Cassie-Baxter and Wenzel modes of wetting.

Model and experimental studies for contact angles of surfactant solutions on rough and smooth hydrophobic surfaces.

Despite the practical need, no models exist to predict contact angles or wetting mode of surfactant solutions on rough hydrophobic or superhydrophobic surfaces. Using Gibbs' adsorption equation and a literature isotherm, a new model is constructed based on the Wenzel and Cassie equations. Experimental data for aqueous solutions of sodium dodecyl sulfate (SDS) contact angles on smooth Teflon surfaces are fit to estimate values for the adsorption coefficients in the model. Using these coefficients, model predictions for contact angles as a function of topological f (Cassie) and r (Wenzel) factors and SDS concentration are made for different intrinsic contact angles. The model is also used to design/tune surface responses. It is found that: (1) predictions compare favorably to data for SDS solutions on five superhydrophobic surfaces. Further, the model predictions can determine which wetting mode (Wenzel or Cassie) occurred in each experiment. The unpenetrated or partially penetrated Cassie mode was the most common, suggesting that surfactants inhibit the penetration of liquids into rough hydrophobic surfaces. (2) The Wenzel roughness factor, r, amplifies the effect of surfactant adsorption, leading to larger changes in contact angles and promoting total wetting. (3) The Cassie solid area fraction, f, attenuates the lowering of contact angles on rough surfaces. (4) The amplification/attenuation is understood to be due to increased/decreased solid-liquid contact-area.

Drop shedding by shear flow for hydrophilic to superhydrophobic surfaces.

A balance of surface science and aerodynamic knowledge is brought to bear to elucidate the fundamental parameters determining the incipient motion (runback) for a drop exposed to shearing airflow. It was found that wetting parameters such as contact angle are very influential in determining the minimum required air velocity for drop shedding. On the basis of experimental results for drops of water and hexadecane (0.5-100 microL) on PMMA, Teflon, and a superhydrophobic aluminum surface, an exponential function is proposed that relates the critical air velocity for shedding to the ratio of drop base length to projected area. The results for all of the water systems can be collapsed to self-similar curves by normalization. Results from other researchers also conform to the exponential self-similar functional form proposed. It was shown that the data for hexadecane drops can be matched relatively well to those for water drops by means of a corrective factor based on fluid properties and contact angles. Also, the critical air velocity for shedding from the superhydrophobic surface is seen to be more constant over a range of volumes than for the other surfaces. Finally, contact angle measurements from airflow shedding experiments are compared to measurements made by tilted plate and quasi-static advancing and receding tests. The observed differences between contact angles from different measurement methods show that the transfer of contact angle data among various applications must be done with care.

Sharing a diagnosis of dementia--learning from the patient perspective.

Sharing a diagnosis of dementia is a key focus of debate and research in the field of dementia care. The pivotal role of the GP in the early identification and subsequent management of dementia has long been recognized and whilst diagnostic practice is improving, the knowledge gained from research exploring the patient perspective is insufficiently absorbed. This paper presents the evidence from the two perspectives of the diagnostic relationship: the views of GPs around giving a diagnosis and the views of patients on receiving one. The authors draw upon their own projects-as well as wider research-in suggesting ways that diagnostic practice can be improved by taking account of the patient perspective. The learning can be distilled around the dimensions of the process, approach and nature of disclosure with evidence particularly challenging the 'myths' held by many GPs around the value of early diagnosis. Whilst much work still needs to be done to incorporate the patient perspective in dementia care, there is clear evidence that patient oriented research has much to offer the development of disclosure practice in primary care to the benefit of patients, their families and GPs.

Evaluation of a combined laser Doppler flowmetry and iontophoresis technique for the assessment of equine cutaneous microvascular function.

A combined laser Doppler flowmetry and iontophoresis (LDFI) technique, used routinely to assess human microvascular function, was evaluated as a noninvasive technique for assessment of equine microvascular function, to facilitate the study of diseases such as laminitis. Baseline and vasoactive agonist-induced (acetylcholine and nitroprusside) microvascular flux was quantified at 2 sites (on the dorsal pastern adjacent to the coronary band and over the gluteals) in 6 clinically normal horses on 5 or 6 separate occasions under standardised conditions. Both agonists significantly increased microvascular flux. Skin pigmentation significantly attenuated the baseline flux, but not the magnitude of the agonist-mediated vasodilatory response. While LDFI was simple to perform, its value as a clinical and research tool for assessing the equine cutaneous microcirculation is limited by its poor reliability, as indicated by the marked intra- and intersubject variability in baseline and agonist-mediated microvascular flux.

Evaluation of the CytoRich technique for cervical smears.

The aim of the study was to assess the ability of the CytoRich System to prepare optimal gynaecological smears for diagnosis. The diagnostic results obtained from evaluating 1,325 matched slide-pairs, prepared using conventional methods and thin-layer technology, were compared. Cytological material for study was obtained using the combined spatula-cytobrush sampling technique. An assessment of the pitfalls associated with the interpretation of these smears was also undertaken. Diagnostic agreement was achieved in 1,272 of the 1,325 matched slide-pairs (96.0%), and these included 1,172 negative, 50 atypical, 24 low-grade squamous intraepithelial lesion (LSIL), 24 high-grade SIL (HSIL), and two malignancies. A total of 1,309 cases showed the same diagnosis within one diagnostic grade for an agreement of 98.8%. Evaluation of the 53 discordant diagnoses revealed that the conventional smear identified a significantly greater number of abnormal smears than the CytoRich technique (P < .001). It is suspected that the use of the combined spatula-cytobrush sampling technique did not provide adequate residual specimen for CytoRich after conventional smear preparation. This limitation is evidenced by the fact that the CytoRich preparations showed a lower yield of endocervical cells (P < .001) and infectious organisms (P < .001) than was demonstrated on conventional smears. Despite a number of diagnostic pitfalls associated with the interpretation of thin-layer smears, these preparations were easier and faster to screen and showed well-preserved and evenly distributed cells. Thin-layer smears were also characterised by a marked reduction in thick cell groups, air drying artifact, and obscuring inflammation and blood. The results confirm the limitation of the combined spatula-cytobrush technique in these types of comparative studies.

Effectiveness of automated cervical cytology rescreening using the AutoPap 300 QC System.

This study assesses the performance of the AutoPap 300 QC System in identifying false-negative (FN) smears in a slide population previously screened as normal and compares the detection rate to that achieved with a random rescreen of the same slide population. A total of 1,840 "normal" smears were rescreened both manually and by the AutoPap 300 QC System. Overall, a total of 7 FN slides were detected. At QC selection rates of 30% and 20% the device achieved sensitivities for detection of FN smears of 57.19% (4/7) and 42.8% (3/7), respectively. This represents a three- to fourfold enrichment in the number of FN smears over that obtained by a random rescreen of a similar proportion of cases. None of the FN slides were identified by either method at a 10% rescreening rate. The ability of the device to detect slides previously classified as abnormal (n = 139) and FN (n = 40) was also studied. The overall sensitivity to abnormal smears at QC selection rates of 10%, 20%, and 50% was 61.9%, 77.0%, and 94.2%, respectively. Improved sensitivity to smears classified as LSIL or worse (n = 112) was obtained for corresponding selection rates (61.6%, 75.9%, and 93.8%). Sensitivity to FN slides classified as LSIL or worse (n = 17) for QC selection rates of 10%, 20%, and 50% was 29.4%, 70.6%, and 88.2%, respectively. The sensitivity and specificity of the device to an adequate squamous and endocervical cell component was also determined. At predetermined thresholds, the overall sensitivity to slides with an inadequate squamous cell component (n = 55) and to those smears with an endocervical cell component (n = 1.587) was 81.8%, and 82.7% respectively. The study demonstrated that the AutoPap 300 QC System is superior to human random rescreen for the identification of FN smears although only a marginal improvement was noted due to the small sample. Further studies are required using a larger number of smears to fully assess the value of the device in quality control mode. The device also has the potential to improve the accuracy of specimen adequacy determinations and to serve as a useful adjunct to existing quality control measures designed to monitor individual performance and reporting accuracy.