4,141 research outputs found
The Structure of Graphene on Graphene/C60/Cu Interfaces: A Molecular Dynamics Study
Two experimental studies reported the spontaneous formation of amorphous and
crystalline structures of C60 intercalated between graphene and a substrate.
They observed interesting phenomena ranging from reaction between C60 molecules
under graphene to graphene sagging between the molecules and control of strain
in graphene. Motivated by these works, we performed fully atomistic reactive
molecular dynamics simulations to study the formation and thermal stability of
graphene wrinkles as well as graphene attachment to and detachment from the
substrate when graphene is laid over a previously distributed array of C60
molecules on a copper substrate at different values of temperature. As graphene
compresses the C60 molecules against the substrate, and graphene attachment to
the substrate between C60s ("C60s" stands for plural of C60) depends on the
height of graphene wrinkles, configurations with both frozen and non-frozen
C60s structures were investigated in order to verify the experimental result of
stable sagged graphene when the distance between C60s is about 4 nm and height
of graphene wrinkles is about 0.8 nm. Below the distance of 4 nm between C60s,
graphene becomes locally suspended and less strained. We show that this happens
when C60s are allowed to deform under the compressive action of graphene. If we
keep the C60s frozen, spontaneous "blanketing" of graphene happens only when
the distance between them are equal or above 7 nm. Both above results for the
existence of stable sagged graphene for C60 distances of 4 or 7 nm are shown to
agree with a mechanical model relating the rigidity of graphene to the energy
of graphene-substrate adhesion. In particular, this study might help the
development of 2D confined nanoreactors that are considered in literature to be
the next advanced step on chemical reactions.Comment: 7 pages, 4 figure
Health System Performance for the High-Need Patient: A Look at Access to Care and Patient Care Experiences
Achieving a high-performing health system will require improving outcomes and reducing costs for high-need, high-cost patients—those who use the most health care services and account for a disproportionately large share of health care spending. Goal: To compare the health care experiences of adults with high needs—those with three or more chronic diseases and a functional limitation in the ability to care for themselves or perform routine daily tasks—to all adults and to those with multiple chronic diseases but no functional limitations. Methods: Analysis of data from the 2009–2011 Medical Expenditure Panel Survey. Key findings: High-need adults were more likely to report having an unmet medical need and less likely to report having good patient–provider communication. High-need adults reported roughly similar ease of obtaining specialist referrals as other adults and greater likelihood of having a medical home. While adults with private health insurance reported the fewest unmet needs overall, privately insured highneed adults reported the greatest difficulties having their needs met. Conclusion: The health care system needs to work better for the highest-need, most-complex patients. This study's findings highlight the importance of tailoring interventions to address their need
σ,π Interaction in Halogen-Substituted Biadamantylidene Radical Cations
The order of E°‘ and vIP for 4-eq-halogenated-biadamantylidene is F > Cl Br, and the 5-F-substituted compound is harder to ozidize than the 4-eq-F-substituted one. The former result is most consistent with a detectable resonance contribution through the σ-framework, and the latter with σ-hyperconjugative destablilization proceeding through two pathways being more than double the same effect through one pathway (the Whiffen effect). AM1 calculations predict these results. The facial selectivity for epoxidation and diazetidine formation from 4-eq-halogenated 3 (4(X)) is in the order Cl > F > Br, and the 5-fluoro compound (8) is less selective than 4(F) for both reactions. Steric as well as electronic factors might well contribute to these results, neither of which was expected from consideration of σ,π interaction. Cation radical catalyzed chain dioxetane formation from 4(F) and 3(Cl) is significantly more face selective than epoxidation or diazetidine formation, as expected on electronic grounds; σ,π interaction should be larger in the radical cation
Characterizing the gut microbiome in trauma: significant changes in microbial diversity occur early after severe injury.
Background:Recent studies have demonstrated the vital influence of commensal microbial communities on human health. The central role of the gut in the response to injury is well described; however, no prior studies have used culture-independent profiling techniques to characterize the gut microbiome after severe trauma. We hypothesized that in critically injured patients, the gut microbiome would undergo significant compositional changes in the first 72 hours after injury. Methods:Trauma stool samples were prospectively collected via digital rectal examination at the time of presentation (0 hour). Patients admitted to the intensive care unit (n=12) had additional stool samples collected at 24 hours and/or 72 hours. Uninjured patients served as controls (n=10). DNA was extracted from stool samples and 16S rRNA-targeted PCR amplification was performed; amplicons were sequenced and binned into operational taxonomic units (OTUs; 97% sequence similarity). Diversity was analyzed using principle coordinates analyses, and negative binomial regression was used to determine significantly enriched OTUs. Results:Critically injured patients had a median Injury Severity Score of 27 and suffered polytrauma. At baseline (0 hour), there were no detectable differences in gut microbial community diversity between injured and uninjured patients. Injured patients developed changes in gut microbiome composition within 72 hours, characterized by significant alterations in phylogenetic composition and taxon relative abundance. Members of the bacterial orders Bacteroidales, Fusobacteriales and Verrucomicrobiales were depleted during 72 hours, whereas Clostridiales and Enterococcus members enriched significantly. Discussion:In this initial study of the gut microbiome after trauma, we demonstrate that significant changes in phylogenetic composition and relative abundance occur in the first 72 hours after injury. This rapid change in intestinal microbiota represents a critical phenomenon that may influence outcomes after severe trauma. A better understanding of the nature of these postinjury changes may lead to the ability to intervene in otherwise pathological clinical trajectories. Level of evidence:III. Study type:Prognostic/epidemiological
Oxidative stress-induced apoptosis in neurons correlates with mitochondrial DNA base excision repair pathway imbalance
Neurodegeneration can occur as a result of endogenous oxidative stress. Primary cerebellar granule cells were used in this study to determine if mitochondrial DNA (mtDNA) repair deficiencies correlate with oxidative stress-induced apoptosis in neuronal cells. Granule cells exhibited a significantly higher intracellular oxidative state compared with primary astrocytes as well as increases in reductants, such as glutathione, and redox sensitive signaling molecules, such as AP endonuclease/redox effector factor-1. Cerebellar granule cultures also exhibited an increased susceptibility to exogenous oxidative stress. Menadione (50 μM) produced twice as many lesions in granule cell mtDNA compared with astrocytes, and granule cell mtDNA repair was significantly less efficient. A decreased capacity to repair oxidative mtDNA damage correlates strongly with mitochondrial initiated apoptosis in these neuronal cultures. Interestingly, the mitochondrial activities of initiators for base excision repair (BER), the bifunctional glycosylase/AP lyases as well as AP endonuclease, were significantly higher in cerebellar granule cells compared with astrocytes. The increased mitochondrial AP endonuclease activity in combination with decreased polymerase γ activity may cause an imbalance in oxidative BER leading to an increased production and persistence of mtDNA damage in neurons when treated with menadione. This study provides evidence linking neuronal mtDNA repair capacity with oxidative stress-related neurodegeneration
The Society for Immunotherapy of Cancer consensus statement on immunotherapy for the treatment of prostate carcinoma.
Prostate cancer is the most commonly diagnosed malignancy and second leading cause of cancer death among men in the United States. In recent years, several new agents, including cancer immunotherapies, have been approved or are currently being investigated in late-stage clinical trials for the management of advanced prostate cancer. Therefore, the Society for Immunotherapy of Cancer (SITC) convened a multidisciplinary panel, including physicians, nurses, and patient advocates, to develop consensus recommendations for the clinical application of immunotherapy for prostate cancer patients. To do so, a systematic literature search was performed to identify high-impact papers from 2006 until 2014 and was further supplemented with literature provided by the panel. Results from the consensus panel voting and discussion as well as the literature review were used to rate supporting evidence and generate recommendations for the use of immunotherapy in prostate cancer patients. Sipuleucel-T, an autologous dendritic cell vaccine, is the first and currently only immunotherapeutic agent approved for the clinical management of metastatic castrate resistant prostate cancer (mCRPC). The consensus panel utilized this model to discuss immunotherapy in the treatment of prostate cancer, issues related to patient selection, monitoring of patients during and post treatment, and sequence/combination with other anti-cancer treatments. Potential immunotherapies emerging from late-stage clinical trials are also discussed. As immunotherapy evolves as a therapeutic option for the treatment of prostate cancer, these recommendations will be updated accordingly
p16INK4a Expression and Immunologic Aging in Chronic HIV Infection
Chronic HIV infection is characterized by increased immune activation and immunosenescence. p16 INK4a (p16) is a member of the cyclin-dependent kinase antagonist family that inhibits cellular proliferation, and its protein expression increases during normal chronological aging. However, some infectious diseases can increase the expression of this anti-proliferative protein, potentially accelerating immunological aging and dysfunction. In order to investigate the immunological aging in HIV patients, p16 protein expression was evaluated by flow cytometry, in T cell subsets in a cohort of chronically HIV-infected patients on and off ART as well as age-matched healthy controls. Results showed that untreated HIV-infected subjects exhibited increased per-cell p16 protein expression that was discordant with chronological aging. ART restored p16 protein expression to levels comparable with HIV-negative subjects in the CD4 compartment, but not in CD8 T cells, which can be an indicative of an irreversible activation/exhaustion status on these cells. Additionally, the frequency of activated CD4+ and CD8+ T cells was positively correlated with p16 expression in CD4+ and CD8+ T cells in untreated subjects. In contrast to healthy controls, untreated HIV-infected individuals had increased p16 levels within the effector memory (TEM) subset, indicating a possible role for this marker in impaired clonal expansion during antiviral effector function. Taken together, these data demonstrate that chronic HIV infection is associated with elevated expression of the cellular aging marker p16 in T cells. ART restored normal p16 levels in the CD4+ T cell compartment, indicating that use of therapy can be of fundamental importance to normal cell cycling and maintaining immune homeostasis
Terrestrial Planet Occurrence Rates for the Kepler GK Dwarf Sample
We measure planet occurrence rates using the planet candidates discovered by
the Q1-Q16 Kepler pipeline search. This study examines planet occurrence rates
for the Kepler GK dwarf target sample for planet radii, 0.75<Rp<2.5 Rearth, and
orbital periods, 50<Porb<300 days, with an emphasis on a thorough exploration
and identification of the most important sources of systematic uncertainties.
Integrating over this parameter space, we measure an occurrence rate of F=0.77
planets per star, with an allowed range of 0.3<F<1.9. The allowed range takes
into account both statistical and systematic uncertainties, and values of F
beyond the allowed range are significantly in disagreement with our analysis.
We generally find higher planet occurrence rates and a steeper increase in
planet occurrence rates towards small planets than previous studies of the
Kepler GK dwarf sample. Through extrapolation, we find that the one year
orbital period terrestrial planet occurrence rate, zeta_1=0.1, with an allowed
range of 0.01<zeta_1<2, where zeta_1 is defined as the number of planets per
star within 20% of the Rp and Porb of Earth. For G dwarf hosts, the zeta_1
parameter space is a subset of the larger eta_earth parameter space, thus
zeta_1 places a lower limit on eta_earth for G dwarf hosts. From our analysis,
we identify the leading sources of systematics impacting Kepler occurrence rate
determinations as: reliability of the planet candidate sample, planet radii,
pipeline completeness, and stellar parameters.Comment: 19 Pages, 17 Figures, Submitted ApJ. Python source to support Kepler
pipeline completeness estimates available at
http://github.com/christopherburke/KeplerPORTs
Hectospec, the MMT's 300 Optical Fiber-Fed Spectrograph
The Hectospec is a 300 optical fiber fed spectrograph commissioned at the MMT
in the spring of 2004. A pair of high-speed six-axis robots move the 300 fiber
buttons between observing configurations within ~300 s and to an accuracy ~25
microns. The optical fibers run for 26 m between the MMT's focal surface and
the bench spectrograph operating at R~1000-2000. Another high dispersion bench
spectrograph offering R~5,000, Hectochelle, is also available. The system
throughput, including all losses in the telescope optics, fibers, and
spectrograph peaks at ~10% at the grating blaze in 1" FWHM seeing. Correcting
for aperture losses at the 1.5" diameter fiber entrance aperture, the system
throughput peaks at 17%. Hectospec has proven to be a workhorse
instrument at the MMT. Hectospec and Hectochelle together were scheduled for
1/3 of the available nights since its commissioning. Hectospec has returned
\~60,000 reduced spectra for 16 scientific programs during its first year of
operation.Comment: 68 pages, 28 figures, to appear in December 2005 PAS
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