42 research outputs found
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Polyamide Nanocomposites for Selective Laser Sintering
Current polyamide 11 and 12 are lacking in fire retardancy and high strength/high
heat resistance characteristics for a plethora of finished parts that are desired and required
for performance driven applications. It is anticipated that nanomodification of polyamide
11 and 12 will result in enhanced polymer performance, i.e., fire retardancy, high strength
and high heat resistance for polyamide 11 and 12. It is expected that these findings will
expand the market opportunities for polyamide 11 and 12 resin manufacturers.
The objective of this research is to develop improved polyamide 11 and 12 polymers
with enhanced flame retardancy, thermal, and mechanical properties for selective laser
sintering (SLS) rapid manufacturing (RM). A nanophase was introduced into the
polyamide 11 and 12 via twin screw extrusion to provide improved material properties of
the polymer blends. Arkema RILSAN® polyamide 11 molding polymer pellets and
Degussa VESTAMID® L1670 polyamide 12 were examined with three types of
nanoparticles: chemically modified montmorillonite (MMT) organoclays, surface
modified nanosilica, and carbon nanofibers (CNFs) to create polyamide 11 and 12
nanocomposites.
Wide angle X-ray diffraction (WAXD) and transmission electron microscopy (TEM)
were used to determine the degree of dispersion. Injection molded test specimens were
fabricated for physical, thermal, mechanical properties, and flammability tests. Thermal
stability of these polyamide 11 and 12 nanocomposites was examined by TGA.
Mechanical properties such as tensile, flexural, and elongation at break were measured.
Flammability properties were also obtained using the Cone Calorimeter at an external
heat flux of 50 kW/m2. TEM micrographs, physical, mechanical, and flammability
properties are included in the paper. Polyamide 11 and 12 nanocomposites properties are
compared with polyamide 11 and 12 baseline polymers. Based on flammability and
mechanical material performance, selective polymers including polyamide 11
nanocomposites and control polyamide 11 were cryogenically ground into fine powders
and fabricated into SLS parts.Mechanical Engineerin
A 2-pyridone-amide inhibitor targets the glucose metabolism pathway of Chlamydia trachomatis.
UnlabelledIn a screen for compounds that inhibit infectivity of the obligate intracellular pathogen Chlamydia trachomatis, we identified the 2-pyridone amide KSK120. A fluorescent KSK120 analogue was synthesized and observed to be associated with the C. trachomatis surface, suggesting that its target is bacterial. We isolated KSK120-resistant strains and determined that several resistance mutations are in genes that affect the uptake and use of glucose-6-phosphate (G-6P). Consistent with an effect on G-6P metabolism, treatment with KSK120 blocked glycogen accumulation. Interestingly, KSK120 did not affect Escherichia coli or the host cell. Thus, 2-pyridone amides may represent a class of drugs that can specifically inhibit C. trachomatis infection.ImportanceChlamydia trachomatis is a bacterial pathogen of humans that causes a common sexually transmitted disease as well as eye infections. It grows only inside cells of its host organism, within a parasitophorous vacuole termed the inclusion. Little is known, however, about what bacterial components and processes are important for C. trachomatis cellular infectivity. Here, by using a visual screen for compounds that affect bacterial distribution within the chlamydial inclusion, we identified the inhibitor KSK120. As hypothesized, the altered bacterial distribution induced by KSK120 correlated with a block in C. trachomatis infectivity. Our data suggest that the compound targets the glucose-6-phosphate (G-6P) metabolism pathway of C. trachomatis, supporting previous indications that G-6P metabolism is critical for C. trachomatis infectivity. Thus, KSK120 may be a useful tool to study chlamydial glucose metabolism and has the potential to be used in the treatment of C. trachomatis infections
Highlights from PHENIX - II
This contribution highlights recent results from the PHENIX Collaboration at
RHIC with emphasis on those obtained through lepton and photon measurements in
PHENIX.Comment: 9 pages, 13 figures, presented at the 20th International Conference
on Ultra-Relativistic Nucleus-Nucleus Collisions - "Quark Matter 2008",
Jaipur, India, February 4-10, 200
Elliptic Flow in Au+Au Collisions at RHIC
Elliptic flow is an interesting probe of the dynamical evolution of the dense
system formed in the ultrarelativistic heavy ion collisions at the Relativistic
Heavy Ion Collider (RHIC). The elliptic flow dependences on transverse
momentum, centrality, and pseudorapidity were measured using data collected by
the PHOBOS detector, which offers a unique opportunity to study the azimuthal
anisotropies of charged particles over a wide range of pseudorapidity. These
measurements are presented, together with an overview of the analysis methods
and a discussion of the results.Comment: Presented at Hot Quarks 2004; 7 pages, 6 figure
Experimental plug&play quantum coin flipping
Performing complex cryptographic tasks will be an essential element in future
quantum communication networks. These tasks are based on a handful of
fundamental primitives, such as coin flipping, where two distrustful parties
wish to agree on a randomly generated bit. Although it is known that quantum
versions of these primitives can offer information-theoretic security
advantages with respect to classical protocols, a demonstration of such an
advantage in a practical communication scenario has remained elusive. Here, we
experimentally implement a quantum coin flipping protocol that performs
strictly better than classically possible over a distance suitable for
communication over metropolitan area optical networks. The implementation is
based on a practical plug&play system, designed for quantum key distribution.
We also show how to combine our protocol with coin flipping protocols that are
almost perfectly secure against bounded adversaries, hence enhancing them with
a level of information-theoretic security. Our results offer a powerful toolbox
for future secure quantum communications.Comment: Version 2, 19 pages including detailed security analysi
Combinatorial polymeric conjugated micelles with dual cytotoxic and antiangiogenic effects for the treatment of ovarian cancer
Emerging treatment paradigms like
targeting the tumor microenvironment
and/or dosing as part of a metronomic regimen are anticipated to produce
better outcomes in ovarian cancer, but current drug delivery systems
are lacking. We have designed and evaluated paclitaxel (PTX) and rapamycin
(RAP) micellar systems that can be tailored for various dosing regimens
and target tumor microenvironment. Individual and mixed PTX/RAP (MIX-M)
micelles are prepared by conjugating drugs to a poly(ethylene glycol)-<i>block</i>-poly(β-benzyl l-aspartate) using a
pH-sensitive linker. The micelles release the drug(s) at pH 5.5 indicating
preferential release in the acidic endosomal/lysosomal environment.
Micelles exhibit antiproliferative effects in ovarian cell cancer
lines (SKOV-3 (human caucasian ovarian adenocarcinoma) and ES2 (human
ovarian clear cell carcinoma)) and an endothelial cell line (HUVEC;
human umbilical vein endothelial cells) with the MIX-M being synergistic.
The micelles also inhibited endothelial migration and tube formation.
In healthy mice, micelles at 60 mg/kg/drug demonstrated no acute toxicity
over 21 days. ES2 xenograft model efficacy studies at 20 mg/kg/drug
dosed every 4 days and evaluated at 21 days indicate that the individual
micelles exhibit antiangiogenic effects, while the MIX-M exhibited
both antiangiogenic and apoptotic induction that results in significant
tumor volume reduction. On the basis of our results, MIX-M micelles
can be utilized to achieve synergistic apoptotic and antiangiogenic
effects when treated at frequent low doses
A global experiment on motivating social distancing during the COVID-19 pandemic
Finding communication strategies that effectively motivate social distancing continues to be a global public health priority during the COVID-19 pandemic. This cross-country, preregistered experiment (n = 25,718 from 89 countries) tested hypotheses concerning generalizable positive and negative outcomes of social distancing messages that promoted personal agency and reflective choices (i.e., an autonomy-supportive message) or were restrictive and shaming (i.e., a controlling message) compared with no message at all. Results partially supported experimental hypotheses in that the controlling message increased controlled motivation (a poorly internalized form of motivation relying on shame, guilt, and fear of social consequences) relative to no message. On the other hand, the autonomy-supportive message lowered feelings of defiance compared with the controlling message, but the controlling message did not differ from receiving no message at all. Unexpectedly, messages did not influence autonomous motivation (a highly internalized form of motivation relying on one’s core values) or behavioral intentions. Results supported hypothesized associations between people’s existing autonomous and controlled motivations and self-reported behavioral intentions to engage in social distancing. Controlled motivation was associated with more defiance and less long-term behavioral intention to engage in social distancing, whereas autonomous motivation was associated with less defiance and more short- and long-term intentions to social distance. Overall, this work highlights the potential harm of using shaming and pressuring language in public health communication, with implications for the current and future global health challenges
A global experiment on motivating social distancing during the COVID-19 pandemic
Significance
Communicating in ways that motivate engagement in social distancing remains a critical global public health priority during the COVID-19 pandemic. This study tested motivational qualities of messages about social distancing (those that promoted choice and agency vs. those that were forceful and shaming) in 25,718 people in 89 countries. The autonomy-supportive message decreased feelings of defying social distancing recommendations relative to the controlling message, and the controlling message increased controlled motivation, a less effective form of motivation, relative to no message. Message type did not impact intentions to socially distance, but people’s existing motivations were related to intentions. Findings were generalizable across a geographically diverse sample and may inform public health communication strategies in this and future global health emergencies.
Abstract
Finding communication strategies that effectively motivate social distancing continues to be a global public health priority during the COVID-19 pandemic. This cross-country, preregistered experiment (n = 25,718 from 89 countries) tested hypotheses concerning generalizable positive and negative outcomes of social distancing messages that promoted personal agency and reflective choices (i.e., an autonomy-supportive message) or were restrictive and shaming (i.e., a controlling message) compared with no message at all. Results partially supported experimental hypotheses in that the controlling message increased controlled motivation (a poorly internalized form of motivation relying on shame, guilt, and fear of social consequences) relative to no message. On the other hand, the autonomy-supportive message lowered feelings of defiance compared with the controlling message, but the controlling message did not differ from receiving no message at all. Unexpectedly, messages did not influence autonomous motivation (a highly internalized form of motivation relying on one’s core values) or behavioral intentions. Results supported hypothesized associations between people’s existing autonomous and controlled motivations and self-reported behavioral intentions to engage in social distancing. Controlled motivation was associated with more defiance and less long-term behavioral intention to engage in social distancing, whereas autonomous motivation was associated with less defiance and more short- and long-term intentions to social distance. Overall, this work highlights the potential harm of using shaming and pressuring language in public health communication, with implications for the current and future global health challenges