Modeling Acoustic Microfluidic Phenomena in Unconventional Geometries

In this work, the performance of a piezoelectrically-actuated ultrasonic droplet generator is analyzed by modeling the harmonic response of a two-dimensional representation of the device cross-section. Observed vibrational and acoustic resonances provide insight into optimal design conditions to achieve efficient, robust droplet ejection. Numerical simulations highlight the importance of the coupled electrical and mechanical behavior of the resonator assembly and show that elastic modes can effectively amplify or dampen acoustic modes within the fluid chamber. Experimentally-validated modeling results guide development of an optimization strategy to further improve device performance. In addition, the standing acoustic field that is the focus of the harmonic response model is incorporated into a custom simulation of the acoustophoretic migration of microparticles. Particles achieve terminal distributions at pressure nodes in the quiescent fluid, exhibiting remarkable agreement with experimental observations. The migratory speed of microparticles in a simple rectangular fluid chamber geometry has been shown to be inversely proportional to the square of the particle radius. Here, this relationship is confirmed for particle migration in more complex acoustic microfluidic geometries

Modeling Acoustic Microfluidic Phenomena in Unconventional Geometries

In this work, the performance of a piezoelectrically-actuated ultrasonic droplet generator is analyzed by modeling the harmonic response of a two-dimensional representation of the device cross-section. Observed vibrational and acoustic resonances provide insight into optimal design conditions to achieve efficient, robust droplet ejection. Numerical simulations highlight the importance of the coupled electrical and mechanical behavior of the resonator assembly and show that elastic modes can effectively amplify or dampen acoustic modes within the fluid chamber. Experimentally-validated modeling results guide development of an optimization strategy to further improve device performance. In addition, the standing acoustic field that is the focus of the harmonic response model is incorporated into a custom simulation of the acoustophoretic migration of microparticles. Particles achieve terminal distributions at pressure nodes in the quiescent fluid, exhibiting remarkable agreement with experimental observations. The migratory speed of microparticles in a simple rectangular fluid chamber geometry has been shown to be inversely proportional to the square of the particle radius. Here, this relationship is confirmed for particle migration in more complex acoustic microfluidic geometries

CD40-CD40 ligand interactions in experimental allergic encephalomyelitis and multiple sclerosis

We investigated the role of CD40-CD40 ligand (CD40L) interactions in multiple sclerosis (MS) and experimental allergic encephalomyelitis (EAE). Activated helper T cells expressing CD40L (gp39) surface protein were found in MS patient brain sections, but not in brain tissue sections of normal controls or patients with other neurological diseases. CD40L-positive cells were co-localized with CD40-bearing cells in active lesions (perivascular infiltrates). Most of these CD40 bearing cells proved to be of the monocytic lineage (macrophages or microglial cells), and relatively few were B cells. To functionally evaluate CD40-CD40L interactions, EAE was elicited in mice by means of proteolipid-peptide immunization. Treatment with anti-CD40L monoclonal antibody completely prevented the development of disease. Furthermore, administration of anti-CD40L monoclonal antibody, even after disease onset, shortly before maximum disability score was reached led to dramatic disease reduction. The presence of helper T cells expressing CD40L in brain tissue of MS patients and EAE animals, together with the functional evidence provided by successful experimental prevention and therapy in an animal model, indicates that blockade of CD40-CD40L-mediated cellular interactions may be a method for interference in active MS

Site 502: Colombia Basin, Western Caribbean

Our specific objective at Site 502 was to recover an undisturbed, complete section that could be used as a Neogene and Quaternary reference section. A complete record such as this would allow intercorrelations between (1) paleomagnetic stratigraphy, (2) calcareous biostratigraphy, (3) cyclic accumulation of sediment, (4) paleoceanographic changes, (5) oxygen and carbon isotope stratigraphies, (6) the chronology of Central American volcanism, (7) the timing and effects of the emergence of the Isthmus of Panama, and (8) the timing and effects of the initiation of Northern Hemisphere glaciation

Channel choice complications:Exploring the multiplex nature of citizens' channel choices

Part 2: E-Government Services and Open GovernmentInternational audienceIn spite of massive investment and increased adoption of digital services, citizens continue to use traditional channels to interact with public organizations. The channel choice (CC) field of research tries to understand citizens’ interactions with public authorities to make the interaction more efficient and increase citizen satisfaction. However, most studies have been conducted either as surveys of hypothetical services or in experimental settings, leading to a lack of empirical data from actual use contexts. Therefore, we present the results of a sequential mixed methods study which combines observations of citizen-caseworker interaction in a call center, contextual interviews with callers, and a survey classifying topics from 10,000 telephone calls. We contribute to the CC field and practice with rich empirical data from studies of actual channel choices. Specifically, the study explores the multiplex nature of real-life CC and demonstrate how telephone calls can be part of a process, which occurs across both traditional and digital channels. Moreover, we identify problems, which cause telephone calls related to digital services, and classify these in two groups: information related problems and action related problems

Site 503: Eastern Equatorial Pacific

Our primary objective at Site 503 (Fig. 1) was to re- cover a complete, undisturbed Neogene and Quaternary section in the eastern equatorial Pacific. Site 503 is located near Site 83 in an area that contains an almost continuous pelagic record of the past 10 m.y. (Hays et al., 1972). Unfortunately, Site 83 was only spot-cored, and the recovered sediment is so badly disturbed by rotary drilling that most of the detailed record is lost. The section has an average sedimentation rate of 2.0 to 2.5 cm/k.y. with good-to-moderate preservation of all the major microfossil groups. We returned to Site 83 to core the same section, using the Hydraulic Piston Corer (HPC) to obtain an undisturbed, continuous section for high-resolution stratigraphic studies

Quantifying the Varying Predictive Value of Physical Activity Measures Obtained from Wearable Accelerometers on All-Cause Mortality Over Short to Medium Time Horizons in NHANES 2003-2006

Physical activity measures derived from wearable accelerometers have been shown to be highly predictive of all-cause mortality. Prediction models based on traditional risk factors and accelerometry-derived physical activity measures are developed for five time horizons. The data set contains 2978 study participants between 50 and 85 years old with an average of 13.08 years of follow-up in the NHANES 2003–2004 and 2005–2006. Univariate and multivariate logistic regression models were fit separately for five datasets for one- to five-year all-cause mortality as outcome (number of events 46, 94, 155, 218, and 297, respectively). In univariate models the total activity count (TAC) was ranked first in all five horizons (AUC between 0.831 and 0.774) while the active to sedentary transition probability (ASTP) was ranked second for one- to four-year mortality models and fourth for the five-year all-cause mortality model (AUC between 0.825 and 0.735). In multivariate models age and ASTP were significant in all one- to five-year all-cause mortality prediction models. Physical activity measures are consistently among the top predictors, even after adjusting for demographic and lifestyle variables. Physical activity measures are strong stand-alone predictors and substantially improve the prediction performance of models based on traditional risk factors

Tunes that Bind?: Predicting Friendship Strength in a Music-Based Social Network

This is the author's accepted manuscript. The final publication is available from Taylor & Francis at http://dx.doi.org/10.1080/13691180802635430.Despite the popularity of social network sites based on common interests, the association between these shared interests and relational development is not well understood. This manuscript reports results of an empirical investigation of interpersonal relationships on Last.fm, a music-based social network site with a multinational user base. In addition to baseline descriptors of relational behavior, the chief goals of this study were to examine the degree to which Last.fm relationships are characterized by homophily (and particularly by shared musical taste), the extent to which communication via Last.fm is associated with other forms of communication (both offline and online), how such communication behavior is associated with demographic and relational characteristics, and whether these variables predict strength of relational development. Results indicate that although Last.fm relational partners exhibit shared musical taste, this shared taste is not associated with relational development. Rather, following media multiplexity theory, relational development is strongly and uniquely associated with communication behavior across almost all forms of communication (including Last.fm). These results suggest that shared interests may foster the creation of weak ties, but conversion of these connections to strong ties is relatively rare

The Effects of Ambient Temperature and Lighting Intensity on Wheel-running Behavior in a Diurnal Rodent, the Nile Grass Rat (Arvicanthis niloticus)

Environmental conditions, such as the light-dark cycle and temperature, affect the display of circadian rhythmicity and locomotor activity patterns in mammals. Here, we tested the hypothesis that manipulating these environmental conditions would affect wheel-running activity patterns in a diurnal rodent, the Nile grass rat (Arvicanthis niloticus). Grass rats are diurnal in the field, however, a subset switch from a day-active pattern to a night-active pattern of activity after the introduction of a running wheel. The mechanism of this chronotype switch remains largely unknown. In the present study, grass rats were presented with running wheels in 12:12 light-dark conditions. First, subjects were exposed to 25 °C during the day and 21 °C at night, which resulted in 100% of grass rats expressing diurnal behavior. Subjects were then exposed to manipulations of elevated ambient temperature, which resulted in a significant reduction in wheel-running activity. Reducing ambient temperature below 21 °C, however, did not disrupt the expression of diurnality or overall activity. Next, lighting intensity was reduced, which resulted in a switch from a diurnal to a nocturnal chronotype in a subset of animals and reduced overall wheel-running activity. Upon return to baseline lighting intensity, patterns of diurnal activity were restored. Altogether, increases in ambient temperature and decreases in lighting intensity significantly reduced overall wheel-running activity. Importantly, dim light resulted in a temporal niche switch in a subset of grass rats, suggesting a critical role for lighting intensity on the expression of wheel-running activity patterns

Normal Behavioral Responses to Light and Darkness and the Pupillary Light Reflex are Dependent Upon the Olivary Pretectal Nucleus in the Diurnal Nile Grass Rat

The olivary pretectal nucleus (OPT) is a midbrain structure that receives reciprocal bilateral retinal projections, is involved in the pupillary light reflex, and connects reciprocally with the intergeniculate leaflet (IGL), a retinorecipient brain region that mediates behavioral responses to light pulses (i.e., masking) in diurnal Nile grass rats. Here, we lesioned the OPT and evaluated behavioral responses in grass rats to various lighting conditions, as well as their anxiety-like responses to light exposure. While control grass rats remained diurnal, grass rats with OPT lesions exhibited a more night-active pattern under 12h:12h light-dark (LD) conditions. However, when placed in constant darkness, OPT-lesioned grass rats became more active during their subjective day, suggesting that an exaggerated masking response to light may be responsible for the effect of OPT lesions on locomotor activity in LD. To test this hypothesis, we presented dark and light pulses to controls and grass rats with OPT lesions; controls increased their activity in response to light, whereas those with OPT lesions significantly increased activity in response to darkness. Further, when placed in a 7-h ultradian LD cycle, animals with OPT lesions were more active during darkness than controls. OPT lesions also abolished the pupillary light reflex, but did not affect anxiety-like behaviors. Finally, in animals with OPT lesions, light did not induce Fos expression in the ventrolateral geniculate nucleus, as it did in controls. Altogether, these results suggest that masking responses to light and darkness are dependent upon nuclei within the subcortical visual shell in grass rats