7,683 research outputs found
Strings at future singularities
We discuss the behaviour of strings propagating in spacetimes which allow
future singularities of either a sudden future or a Big-Rip type. We show that
in general the invariant string size remains finite at sudden future
singularities while it grows to infinity at a Big-Rip. This claim is based on
the discussion of both the tensile and null strings. In conclusion, strings may
survive a sudden future singularity, but not a Big-Rip where they are
infinitely stretched.Comment: REVTEX 4.0, 4 pages, no figures, references adde
All-optical hyperpolarization of electron and nuclear spins in diamond
Low thermal polarization of nuclear spins is a primary sensitivity limitation
for nuclear magnetic resonance. Here we demonstrate optically pumped
(microwave-free) nuclear spin polarization of and
in -doped diamond.
polarization enhancements up to above thermal equilibrium are observed
in the paramagnetic system . Nuclear spin polarization is
shown to diffuse to bulk with NMR enhancements of at
room temperature and at , enabling a route to
microwave-free high-sensitivity NMR study of biological samples in ambient
conditions.Comment: 5 pages, 5 figure
A Non-Relativistic Weyl Anomaly
We examine the Weyl anomaly for a four-dimensional z=3 Lifshitz scalar
coupled to Horava's theory of anisotropic gravity. We find a one-loop
break-down of scale-invariance at second order in the gravitational background.Comment: LaTeX, 23 pages, no figures, JHEP style; v2: typos fixed to match the
published versio
Prion protein gene sequence and chronic wasting disease susceptibility in white-tailed deer (Odocoileus virginianus)
The sequence of the prion protein gene (PRNP) affects susceptibility to spongiform encephalopathies, or prion diseases in many species. In white-tailed deer, both coding and non-coding single nucleotide polymorphisms have been identified in this gene that correlate to chronic wasting disease (CWD) susceptibility. Previous studies examined individual nucleotide or amino acid mutations; here we examine all nucleotide polymorphisms and their combined effects on CWD. A 626 bp region of PRNP was examined from 703 free-ranging white-tailed deer. Deer were sampled between 2002 and 2010 by hunter harvest or government culling in Illinois and Wisconsin. Fourteen variable nucleotide positions were identified (4 new and 10 previously reported). We identified 68 diplotypes comprised of 24 predicted haplotypes, with the most common diplotype occurring in 123 individuals. Diplotypes that were found exclusively among positive or negative animals were rare, each occurring in less than 1% of the deer studied. Only one haplotype (C, odds ratio 0.240) and 2 diplotypes (AC and BC, odds ratios of 0.161 and 0.108 respectively) has significant associations with CWD resistance. Each contains mutations (one synonymous nucleotide 555C/T and one nonsynonymous nucleotide 286G/A) at positions reported to be significantly associated with reduced CWD susceptibility. Results suggest that deer populations with higher frequencies of haplotype C or diplotypes AC and BC might have a reduced risk for CWD infection – while populations with lower frequencies may have higher risk for infection. Understanding the genetic basis of CWD has improved our ability to assess herd susceptibility and direct management efforts within CWD infected areas.https://digitalcommons.snc.edu/faculty_staff_works/1029/thumbnail.jp
Fast non-negative deconvolution for spike train inference from population calcium imaging
Calcium imaging for observing spiking activity from large populations of
neurons are quickly gaining popularity. While the raw data are fluorescence
movies, the underlying spike trains are of interest. This work presents a fast
non-negative deconvolution filter to infer the approximately most likely spike
train for each neuron, given the fluorescence observations. This algorithm
outperforms optimal linear deconvolution (Wiener filtering) on both simulated
and biological data. The performance gains come from restricting the inferred
spike trains to be positive (using an interior-point method), unlike the Wiener
filter. The algorithm is fast enough that even when imaging over 100 neurons,
inference can be performed on the set of all observed traces faster than
real-time. Performing optimal spatial filtering on the images further refines
the estimates. Importantly, all the parameters required to perform the
inference can be estimated using only the fluorescence data, obviating the need
to perform joint electrophysiological and imaging calibration experiments.Comment: 22 pages, 10 figure
Research-to-Practice Brief: Promising Evidence that Early Head Start Can Prevent Child Maltreatment
This brief addresses two main questions in a sample of Early Head Start eligible children: 1) the number and type of maltreatment episodes and 2) the impact of Early Head Start on child and family involvement in the child welfare system. These findings are especially important given the lack of scalable and effective preventive interventions. In addition, they are also timely given the recent interest in fostering collaborations between early care and education programs and child welfare agencies, agencies responsible for overseeing child protection from maltreatment (OHS & ACYF, 2010; ACYF & OHS, 2011; ACYF & OCC, 2011). The current study represents a first look at the impact of Early Head Start on child maltreatment. We are continuing to collect data and will have more information in the upcoming years
Tapping Environmental History to Recreate America’s Colonial Hydrology
To properly remediate, improve, or predict how hydrological systems behave, it is vital to establish their histories. However, modern-style records, assembled from instrumental data and remote sensing platforms, hardly exist back more than a few decades. As centuries of data is preferable given multidecadal fluxes of both meteorology/climatology and demographics, building such a history requires resources traditionally considered only useful in the social sciences and humanities. In this Feature, Pastore et al. discuss how they have undertaken the synthesis of historical records and modern techniques to understand the hydrology of the Northeastern U.S. from Colonial times to modern day. Such approaches could aid studies in other regions that may require heavier reliance on qualitative narratives. Further, a better insight as to how historical changes unfolded could provide a “past is prologue” methodology to increase the accuracy of predictive environmental models
(C^Npz^C)AuIII complexes of acyclic carbene ligands: synthesis and anticancer properties
A series of cyclometallated gold(III) complexes supported by pyrazine-based (C^Npz^C)-type pincer ligands were synthesized via two different pathways. Nucleophilic attack on the isocyanide complex [(C^Npz^C)Au(C≡NC6H3Me2-2,6)]SbF6 (2) gave [(C^Npz^C)Au(ACC)]SbF6 complexes with aniline (4·SbF6), adamantylamine (5), glycine ethyl ester (6), alanine methyl ester (7), valine methyl ester (8), phenylglycine methyl ester (9) and methionine methyl ester (10) substituents (ACC = acyclic carbene). The pathway via isocyanide insertion into gold-amide bonds was also investigated; e.g. the reaction of xylyl isocyanide with (C^Npz^C)AuNHPh followed by protonation with HBF4·OEt2 gave the acyclic carbene complex 4·BF4. To the best of our knowledge compounds 6 - 10 represent the first examples of gold(III) acyclic carbene complexes bearing amino acid functions. The compounds provide a versatile platform for the study of anti-proliferative properties of gold(III) complexes. Tests against human adenoma-type lung cancer cells identified 5, 6, 7 and 10 as particularly promising and demonstrate the synthetic flexibility of acyclic carbene complexes and the potential of that class of compounds for anticancer applications. Compared to cisplatin, amino ester-containing ACC complexes showed significantly improved selectivity for MCF-7 breast cancer cells over healthy fibroblasts
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