205 research outputs found
Double helical conformation and extreme rigidity in a rodlike polyelectrolyte
The ubiquitous biomacromolecule DNA has an axial rigidity persistence length
of ~50 nm, driven by its elegant double helical structure. While double and
multiple helix structures appear widely in nature, only rarely are these found
in synthetic non-chiral macromolecules. Here we describe a double helical
conformation in the densely charged aromatic polyamide
poly(2,2'-disulfonyl-4,4'-benzidine terephthalamide) or PBDT. This double helix
macromolecule represents one of the most rigid simple molecular structures
known, exhibiting an extremely high axial persistence length (~1 micrometer).
We present X-ray diffraction, NMR spectroscopy, and molecular dynamics (MD)
simulations that reveal and confirm the double helical conformation. The
discovery of this extreme rigidity in combination with high charge density
gives insight into the self-assembly of molecular ionic composites with high
mechanical modulus (~1 GPa) yet with liquid-like ion motions inside, and
provides fodder for formation of new 1D-reinforced composites.Comment: Accepted for publication by Nature Communication
A global method for coupling transport with chemistry in heterogeneous porous media
Modeling reactive transport in porous media, using a local chemical
equilibrium assumption, leads to a system of advection-diffusion PDE's coupled
with algebraic equations. When solving this coupled system, the algebraic
equations have to be solved at each grid point for each chemical species and at
each time step. This leads to a coupled non-linear system. In this paper a
global solution approach that enables to keep the software codes for transport
and chemistry distinct is proposed. The method applies the Newton-Krylov
framework to the formulation for reactive transport used in operator splitting.
The method is formulated in terms of total mobile and total fixed
concentrations and uses the chemical solver as a black box, as it only requires
that on be able to solve chemical equilibrium problems (and compute
derivatives), without having to know the solution method. An additional
advantage of the Newton-Krylov method is that the Jacobian is only needed as an
operator in a Jacobian matrix times vector product. The proposed method is
tested on the MoMaS reactive transport benchmark.Comment: Computational Geosciences (2009)
http://www.springerlink.com/content/933p55085742m203/?p=db14bb8c399b49979ba8389a3cae1b0f&pi=1
Rebooting an Old Script by New Means: TeledildonicsâThe Technological Return to the âCoital Imperativeâ
Teledildonics, a form of digital-mediated sexual interaction, opens new possibilities for the understanding of sexual activity. At first glance, it disrupts conventional preconditions and assumptions about sexual interaction, by allowing the dimension of touch despite the physical distance between partners and, ultimately, promoting a sexual dimension definitely disconnected from the reproductive model of sexuality. However, by scrutinizing the design and functionality of the devices, as well as the discourses presented by three commercial companiesâLovePalz, Lovense and KiirooâI suggest that this technology reinforces the âcoital imperativeâ, by equating sexual interaction with penetration of the vagina by the penis. Although permitting other formulations, specifically for non-heterosexual couples, the penetrative act remains a presupposition. In spite of structurally disrupting the reproductive model of sex, teledildonics promotes its strongest corollary.info:eu-repo/semantics/publishedVersio
The Problematization of Sexuality among Women Living with HIV and a New Feminist Approach for Understanding and Enhancing Womenâs Sexual Lives
In the context of HIV, womenâs sexual rights and sexual autonomy are important but frequently overlooked and violated. Guided by community voices, feminist theories, and qualitative empirical research, we reviewed two decades of global quantitative research on sexuality among women living with HIV. In the 32 studies we found, conducted in 25 countries and composed mostly of cis-gender heterosexual women, sexuality was narrowly constructed as sexual behaviours involving risk (namely, penetration) and physiological dysfunctions relating to HIV illness, with far less attention given to the fullness of sexual lives in context, including more positive and rewarding experiences such as satisfaction and pleasure. Findings suggest that women experience declines in sexual activity, function, satisfaction, and pleasure following HIV diagnosis, at least for some period. The extent of such declines, however, is varied, with numerous contextual forces shaping womenâs sexual well-being. Clinical markers of HIV (e.g., viral load, CD4 cell count) poorly predicted sexual outcomes, interrupting widely held assumptions about sexuality for women with HIV. Instead, the effects of HIV-related stigma intersecting with inequities related to trauma, violence, intimate relations, substance use, poverty, aging, and other social and cultural conditions primarily influenced the ways in which women experienced and enacted their sexuality. However, studies framed through a medical lens tended to pathologize outcomes as individual âproblems,â whereas others driven by a public health agenda remained primarily preoccupied with protecting the public from HIV. In light of these findings, we present a new feminist approach for research, policy, and practice toward understanding and enhancing womenâs sexual livesâone that affirms sexual diversity; engages deeply with society, politics, and history; and is grounded in womenâs sexual rights
Resisting the mantle of the monstrous feminine : women's construction and experience of premenstrual embodiment
The female reproductive body is positioned as abject, as other, as site of defciency and disease, the epitome of the âmonstrous feminine.â Premenstrual change in emotion, behavior or embodied sensation is positioned as a sign of madness within, necessitating restraint and control on the part of the women experiencing it (Ussher 2006). Breakdown in this control through manifestation of âsymptomsâ is diagnosed as PMS (Premenstrual Syndrome) or PMDD (Premenstrual Dysphoric Disorder), a pathology deserving of âtreatment.â In this chapter, we adopt a feminist material-discursive theoretical framework to examine the role of premenstrual embodiment in relation to womenâs adoption of the subject position of monstrous feminine, drawing on interviews we have conducted with women who self-diagnose as âPMS sufferers.â We theorize womenâs self-positioning as subjectifcation, wherein women take up cultural discourse associated with idealized femininity and the reproductive body, resulting in self-objectifcation, distress, and self-condemnation. However, women can resist negative cultural constructions of premenstrual embodiment and the subsequent self-policing. We describe the impact of women-centered psychological therapy which increases awareness of embodied change, and leads to greater acceptance of the premenstrual body and greater self-care, which serves to reduce premenstrual distress
A Compact Dication Source for Ba Tagging and Heavy Metal Ion Sensor Development
We present a tunable metal ion beam that delivers controllable ion currents
in the picoamp range for testing of dry-phase ion sensors. Ion beams are formed
by sequential atomic evaporation and single or multiple electron impact
ionization, followed by acceleration into a sensing region. Controllability of
the ionic charge state is achieved through tuning of electrode potentials that
influence the retention time in the ionization region. Barium, lead, and cobalt
samples have been used to test the system, with ion currents identified and
quantified using a quadrupole mass analyzer. Realization of a clean
ion beam within a bench-top system represents an important
technical advance toward the development and characterization of barium tagging
systems for neutrinoless double beta decay searches in xenon gas. This system
also provides a testbed for investigation of novel ion sensing methodologies
for environmental assay applications, with dication beams of Pb and
Cd also demonstrated for this purpose
NEXT-CRAB-0: A High Pressure Gaseous Xenon Time Projection Chamber with a Direct VUV Camera Based Readout
The search for neutrinoless double beta decay () remains one
of the most compelling experimental avenues for the discovery in the neutrino
sector. Electroluminescent gas-phase time projection chambers are well suited
to searches due to their intrinsically precise energy
resolution and topological event identification capabilities. Scalability to
ton- and multi-ton masses requires readout of large-area electroluminescent
regions with fine spatial resolution, low radiogenic backgrounds, and a
scalable data acquisition system. This paper presents a detector prototype that
records event topology in an electroluminescent xenon gas TPC via VUV
image-intensified cameras. This enables an extendable readout of large tracking
planes with commercial devices that reside almost entirely outside of the
active medium.Following further development in intermediate scale
demonstrators, this technique may represent a novel and enlargeable method for
topological event imaging in .Comment: 32 Pages, 22 figure
Ba+2 ion trapping using organic submonolayer for ultra-low background neutrinoless double beta detector
If neutrinos are their own antiparticles the otherwise-forbidden nuclear reaction known as neutrinoless double beta decay can occur. The very long lifetime expected for these exceptional events makes its detection a daunting task. In order to conduct an almost background-free experiment, the NEXT collaboration is investigating novel synthetic molecular sensors that may capture the Ba dication produced in the decay of certain Xe isotopes in a high-pressure gas experiment. The use of such molecular detectors immobilized on surfaces must be explored in the ultra-dry environment of a xenon gas chamber. Here, using a combination of highly sensitive surface science techniques in ultra-high vacuum, we demonstrate the possibility of employing the so-called Fluorescent Bicolor Indicator as the molecular component of the sensor. We unravel the ion capture process for these molecular indicators immobilized on a surface and explain the origin of the emission fluorescence shift associated to the ion trapping
Gene therapy for monogenic liver diseases: clinical successes, current challenges and future prospects
Over the last decade, pioneering liver-directed gene therapy trials for haemophilia B have achieved sustained clinical improvement after a single systemic injection of adeno-associated virus (AAV) derived vectors encoding the human factor IX cDNA. These trials demonstrate the potential of AAV technology to provide long-lasting clinical benefit in the treatment of monogenic liver disorders. Indeed, with more than ten ongoing or planned clinical trials for haemophilia A and B and dozens of trials planned for other inherited genetic/metabolic liver diseases, clinical translation is expanding rapidly. Gene therapy is likely to become an option for routine care of a subset of severe inherited genetic/metabolic liver diseases in the relatively near term. In this review, we aim to summarise the milestones in the development of gene therapy, present the different vector tools and their clinical applications for liver-directed gene therapy. AAV-derived vectors are emerging as the leading candidates for clinical translation of gene delivery to the liver. Therefore, we focus on clinical applications of AAV vectors in providing the most recent update on clinical outcomes of completed and ongoing gene therapy trials and comment on the current challenges that the field is facing for large-scale clinical translation. There is clearly an urgent need for more efficient therapies in many severe monogenic liver disorders, which will require careful risk-benefit analysis for each indication, especially in paediatrics
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