382 research outputs found
Effects of counterion fluctuations in a polyelectrolyte brush
We investigate the effect of counterion fluctuations in a single
polyelectrolyte brush in the absence of added salt by systematically expanding
the counterion free energy about Poisson-Boltzmann mean field theory. We find
that for strongly charged brushes, there is a collapse regime in which the
brush height decreases with increasing charge on the polyelectrolyte chains.
The transition to this collapsed regime is similar to the liquid-gas
transition, which has a first-order line terminating at a critical point. We
find that for monovalent counterions the transition is discontinuous in theta
solvent, while for multivalent counterions the transition is generally
continuous. For collapsed brushes, the brush height is not independent of
grafting density as it is for osmotic brushes, but scales linear with it.Comment: 9 pages, 9 figure
Costly encounters of the empathic kind: a typology
While considerable attention is being accorded to emotions in International Relations, this article seeks to integrate empathy into these interdisciplinary debates. It counters the dominant assumption that empathy tends to be largely benign and beneficial by conceptualizing a typology of the costs of empathy. The dimensions of costs addressed are epistemological, cognitive, emotional, material, and embodied. I argue that these costs are frequently tangible for those who make the ethical-political choice to engage in empathy in situations of conflict and political violence. Drawing on social psychology approaches, empathy is located within a framework of collective narratives, emotions, and social structures shaped by both micro- and macro-political processes. A model of empathy, which acknowledges social influences and the psychological mechanisms through which these influences may be mediated, contributes to a deeper understanding of how politics, psychology, and culture shape empathy and, crucially, helps understand the conditions which may affect the successes, limitations, and failures of empathy in the (international) political sphere. The article offers empirical illustrations of the costs of empathy drawing on examples from Israel and Palestine
Broken-Symmetry States in Quantum Hall Superlattices
We argue that broken-symmetry states with either spatially diagonal or
spatially off-diagonal order are likely in the quantum Hall regime, for clean
multiple quantum well (MQW) systems with small layer separations. We find that
for MQW systems, unlike bilayers, charge order tends to be favored over
spontaneous interlayer coherence. We estimate the size of the interlayer
tunneling amplitude needed to stabilize superlattice Bloch minibands by
comparing the variational energies of interlayer-coherent superlattice miniband
states with those of states with charge order and states with no broken
symmetries. We predict that when coherent miniband ground states are stable,
strong interlayer electronic correlations will strongly enhance the
growth-direction tunneling conductance and promote the possibility of Bloch
oscillations.Comment: 9 pages LaTeX, 4 figures EPS, to be published in PR
Neutral and Charged Polymers at Interfaces
Chain-like macromolecules (polymers) show characteristic adsorption
properties due to their flexibility and internal degrees of freedom, when
attracted to surfaces and interfaces. In this review we discuss concepts and
features that are relevant to the adsorption of neutral and charged polymers at
equilibrium, including the type of polymer/surface interaction, the solvent
quality, the characteristics of the surface, and the polymer structure. We pay
special attention to the case of charged polymers (polyelectrolytes) that have
a special importance due to their water solubility. We present a summary of
recent progress in this rapidly evolving field. Because many experimental
studies are performed with rather stiff biopolymers, we discuss in detail the
case of semi-flexible polymers in addition to flexible ones. We first review
the behavior of neutral and charged chains in solution. Then, the adsorption of
a single polymer chain is considered. Next, the adsorption and depletion
processes in the many-chain case are reviewed. Profiles, changes in the surface
tension and polymer surface excess are presented. Mean-field and corrections
due to fluctuations and lateral correlations are discussed. The force of
interaction between two adsorbed layers, which is important in understanding
colloidal stability, is characterized. The behavior of grafted polymers is also
reviewed, both for neutral and charged polymer brushes.Comment: a review: 130 pages, 30 ps figures; final form, added reference
Meta-analysis of genome-wide association studies from the CHARGE consortium identifies common variants associated with carotid intima media thickness and plaque
Carotid intima media thickness (cIMT) and plaque determined by ultrasonography are established measures of subclinical atherosclerosis that each predicts future cardiovascular disease events. We conducted a meta-analysis of genome-wide association data in 31,211 participants of European ancestry from nine large studies in the setting of the Cohorts for Heart and Aging Research in Genomic Epidemiology (CHARGE) Consortium. We then sought additional evidence to support our findings among 11,273 individuals using data from seven additional studies. In the combined meta-analysis, we identified three genomic regions associated with common carotid intima media thickness and two different regions associated with the presence of carotid plaque (P < 5 × 10 -8). The associated SNPs mapped in or near genes related to cellular signaling, lipid metabolism and blood pressure homeostasis, and two of the regions were associated with coronary artery disease (P < 0.006) in the Coronary Artery Disease Genome-Wide Replication and Meta-Analysis (CARDIoGRAM) consortium. Our findings may provide new insight into pathways leading to subclinical atherosclerosis and subsequent cardiovascular events
Two-Body B Meson Decays to and -- Observation of {'}K$
In a sample of 6.6 million produced B mesons we have observed decays B ->
eta' K, with branching fractions BR(B+ -> eta' K+ = 6.5 +1.5 -1.4 +- 0.9) x
and BR(B0 -> eta' K0 = 4.7 +2.7 -2.0 +- 0.9) x . We have
searched with comparable sensitivity for 17 related decays to final states
containing an eta or eta' meson accompanied by a single particle or low-lying
resonance. Our upper limits for these constrain theoretical interpretations of
the B -> eta' K signal.Comment: 12 page postscript file, postscript file also available through
http://w4.lns.cornell.edu/public/CLN
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The Impact of Postpartum Posttraumatic Stress and Depression Symptoms on Couples' Relationship Satisfaction: A Population-Based Prospective Study
The couple relationship is of particular importance in the transition to parenthood and in the early childhood years because it is related to the well-being and mental health of partners, children, and the family. One factor that may substantially influence relationship quality and couple satisfaction after childbirth is the woman’s experience of birth. Approximately 2–4% of women develop posttraumatic stress disorder (PTSD) after childbirth, with potentially wide-ranging negative consequences for the women themselves and their families. To date, some qualitative studies have explored the influence of postpartum PTSD on couple relationship satisfaction. However, quantitative studies are sparse, with mixed results and methodological limitations. We hypothesized that postpartum PTSD will be prospectively associated with low couple relationship satisfaction, even when taking into account a variety of potential confounding variables, and that the effect of postpartum PTSD symptoms on couple relationship satisfaction will be mediated by postpartum depression symptoms. This study is based on data from the Akershus Birth Cohort study, a prospective cohort study. Information from hospital records and questionnaires completed at 17 weeks gestational age, as well as at 8 weeks and 2 years postpartum were used (n = 1480). PTSD symptoms were measured by the Impact of Event Scale and couple relationship satisfaction was assessed using a modified version of the Mehrabians Marital Satisfaction Scale. Depressive symptoms were assessed by the Edinburgh Postnatal Depression Scale. Data were analyzed using bivariate correlations, multivariate regression analyses, and mediation analyses. Postpartum PTSD symptoms were prospectively related to low couple relationship satisfaction at 2 years postpartum, even when controlling for a considerable number of background factors. When including postpartum depression symptoms as predictor in the analyses, the effect of postpartum PTSD was no longer significant. Moreover, more detailed analyses showed that postpartum depression symptoms acted as a significant mediator, fully explaining the association of postpartum PTSD with couples’ relationship satisfaction. Early detection of couples’ relationship problems and the provision of professional help, particularly in high-risk couples may not only improve the quality of the couple relationship but also improve parenting and promote positive child outcomes
A program evaluation report of a rapid scale-up of a high-volume medical male circumcision site, KwaZulu-Natal, South Africa, 2010–2013
Impact of Immunization Technology and Assay Application on Antibody Performance – A Systematic Comparative Evaluation
Antibodies are quintessential affinity reagents for the investigation and determination of a protein's expression patterns, localization, quantitation, modifications, purification, and functional understanding. Antibodies are typically used in techniques such as Western blot, immunohistochemistry (IHC), and enzyme-linked immunosorbent assays (ELISA), among others. The methods employed to generate antibodies can have a profound impact on their success in any of these applications. We raised antibodies against 10 serum proteins using 3 immunization methods: peptide antigens (3 per protein), DNA prime/protein fragment-boost (“DNA immunization”; 3 per protein), and full length protein. Antibodies thus generated were systematically evaluated using several different assay technologies (ELISA, IHC, and Western blot). Antibodies raised against peptides worked predominantly in applications where the target protein was denatured (57% success in Western blot, 66% success in immunohistochemistry), although 37% of the antibodies thus generated did not work in any of these applications. In contrast, antibodies produced by DNA immunization performed well against both denatured and native targets with a high level of success: 93% success in Western blots, 100% success in immunohistochemistry, and 79% success in ELISA. Importantly, success in one assay method was not predictive of success in another. Immunization with full length protein consistently yielded the best results; however, this method is not typically available for new targets, due to the difficulty of generating full length protein. We conclude that DNA immunization strategies which are not encumbered by the limitations of efficacy (peptides) or requirements for full length proteins can be quite successful, particularly when multiple constructs for each protein are used
Moving out of the shadows: accomplishing bisexual motherhood
Our qualitative study explored the ways in which bisexual mothers came to identify as such and how they structured their relationships and
parenting within hetero-patriarchal society. The experiences of seven self-identified White bisexual women (aged from 28 to 56-years-old) from
across England and the Republic of Ireland were investigated through semi-structured interviews. Participants’ children were aged 8 months to
28 years old at the time of their interviews. A thematic narrative analysis highlighted the following issues that participants had encountered in
constructing their self-identity: prioritizing children; connecting and disconnecting with others and finessing self-definition; questioning societal
relationship expectations. Nevertheless, participants varied considerably in how each of the themes identified were reflected in their lives, in
particular depending upon each participant’s interpretation of her local social context. Both motherhood and self-identifying as bisexual gave a
sense of meaning and purpose to participants’ life stories, although participants sometimes foregrounded their commitment to their children
even at a personal cost to their bisexual identity. Using three different theoretical perspectives from feminist theory, queer theory and life course
theory, the narratives analysed revealed ways in which bisexual motherhood not only had been influenced both intentionally and unintentionally
by heteronormative expectations but also had directly and indirectly challenged these expectations
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