Global Diffusion in a Realistic Three-Dimensional Time-Dependent Nonturbulent Fluid Flow

We introduce and study the first model of an experimentally realizable three-dimensional time-dependent nonturbulent fluid flow to display the phenomenon of global diffusion of passive-scalar particles at arbitrarily small values of the nonintegrable perturbation. This type of chaotic advection, termed {\it resonance-induced diffusion\/}, is generic for a large class of flows.Comment: 4 pages, uuencoded compressed postscript file, to appear in Phys. Rev. Lett. Also available on the WWW from http://formentor.uib.es/~julyan/, or on paper by reques

To the Continuum and Beyond: Structure of U Nuclei

An experiment was performed at the 88-inch cyclotron at LBNL to investigate the structure of uranium isotopes and concurrently test the so-called surrogate ratio method. A 28 MeV proton beam was used to bombard 236U and 238U targets and the outgoing light ions were detected using the STARS silicon telescope allowing isotopic assignments and the excitation energy of the compound nucleus to be measured. A fission detector was placed at backward angles to give particle-fission coincidences, while the six clover germanium detectors of the LIBERACE array were used for particle-γ coincidences. The (p,d) reaction channels on 236U and 238U targets were used as a surrogate to measure the σ(234U(n,f))/σ(236U(n,f)) cross section ratio. The results give reasonable agreement with literature values over an equivalent neutron energy range between 0 MeV and 6 MeV. Structure results in 235U include a new (3/2−) level at 1035 keV, that is tentatively assigned as the 3/2−[501] Nilsson state. The analogue 3/2−[501] state in 237U may be associated with a previously observed level at 1201 keV, whose spin/parity is restricted to Jπ = 3/2− on the basis of newly observed decays to the ground band

Utilizing (\u3cem\u3ep,d\u3c/em\u3e) and (\u3cem\u3ep,t\u3c/em\u3e) Reactions to Obtain (\u3cem\u3en,f\u3c/em\u3e) Cross Sections in Uranium Nuclei Via the Surrogate-Ratio Method

The surrogate ratio method has been tested for (p,d) and (p,t) reactions on uranium nuclei. 236U and 238U targets were bombarded with 28-MeV protons and the light ion recoils and fission fragments were detected using the Silicon Telescope Array for Reaction Studies detector array at the 88-Inch Cyclotron at Lawrence Berkeley National Laboratory. The (p,df) reaction channels on 236U and 238U targets were used as a surrogate to determine the σ[236U(n,f)]/σ[234U(n,f)] cross-section ratio. The (p,tf) reaction channels were also measured with the same targets as a surrogate for the σ[235U(n,f)]/σ[(233U(n,f)] ratio. For the (p,df) and (p,tf) surrogate measurements, there is good agreement with accepted (n,f) values over equivalent neutron energy ranges of En=0–7 MeV and En=0–5.5 MeV, respectively. An internal surrogate ratio method comparing the (p,d) and (p,t) reaction channels on a single target is also discussed. The σ[234U(n,f)]/σ[233U(n,f)] and σ[236U(n,f)]/σ[235U(n,f)] cross-section ratios are extracted using this method for the 236U and 238U targets, respectively. The resulting fission cross-section ratios show relatively good agreement with accepted values up to En∼5 MeV

Novel endosomolytic compounds enable highly potent delivery of antisense oligonucleotides

The therapeutic and research potentials of oligonucleotides (ONs) have been hampered in part by their inability to effectively escape endosomal compartments to reach their cytosolic and nuclear targets. Splice-switching ONs (SSOs) can be used with endosomolytic small molecule compounds to increase functional delivery. So far, development of these compounds has been hindered by a lack of high-resolution methods that can correlate SSO trafficking with SSO activity. Here we present in-depth characterization of two novel endosomolytic compounds by using a combination of microscopic and functional assays with high spatiotemporal resolution. This system allows the visualization of SSO trafficking, evaluation of endosomal membrane rupture, and quantitates SSO functional activity on a protein level in the presence of endosomolytic compounds. We confirm that the leakage of SSO into the cytosol occurs in parallel with the physical engorgement of LAMP1-positive late endosomes and lysosomes. We conclude that the new compounds interfere with SSO trafficking to the LAMP1-positive endosomal compartments while inducing endosomal membrane rupture and concurrent ON escape into the cytosol. The efficacy of these compounds advocates their use as novel, potent, and quick-acting transfection reagents for antisense ONs

Integromic analysis of genetic variation and gene expression identifies networks for cardiovascular disease phenotypes

BACKGROUND - : Cardiovascular disease (CVD) reflects a highly coordinated complex of traits. Although genome-wide association studies have reported numerous single nucleotide polymorphisms (SNPs) to be associated with CVD, the role of most of these variants in disease processes remains unknown. METHODS AND RESULTS - : We built a CVD network using 1512 SNPs associated with 21 CVD traits in genome-wide association studies (at P≤5×10) and cross-linked different traits by virtue of their shared SNP associations. We then explored whole blood gene expression in relation to these SNPs in 5257 participants in the Framingham Heart Study. At a false discovery rate <0.05, we identified 370 cis-expression quantitative trait loci (eQTLs; SNPs associated with altered expression of nearby genes) and 44 trans-eQTLs (SNPs associated with altered expression of remote genes). The eQTL network revealed 13 CVD-related modules. Searching for association of eQTL genes with CVD risk factors (lipids, blood pressure, fasting blood glucose, and body mass index) in the same individuals, we found examples in which the expression of eQTL genes was significantly associated with these CVD phenotypes. In addition, mediation tests suggested that a subset of SNPs previously associated with CVD phenotypes in genome-wide association studies may exert their function by altering expression of eQTL genes (eg, LDLR and PCSK7), which in turn may promote interindividual variation in phenotypes. CONCLUSIONS - : Using a network approach to analyze CVD traits, we identified complex networks of SNP-phenotype and SNP-transcript connections. Integrating the CVD network with phenotypic data, we identified biological pathways that may provide insights into potential drug targets for treatment or prevention of CVD

Remnants of Spherical Shell Structures in Deformed Nuclei: The Impact of an \u3cem\u3eN\u3c/em\u3e = 64 Neutron Subshell Closure on the Structure of \u3cem\u3eN\u3c/em\u3e ≈ 90 Gadolinium Nuclei

Odd-mass gadolinium isotopes around N = 90 were populated by the (p,d) reaction, utilizing 25-MeV protons, resulting in population of low-spin quasineutron states at energies near and below the Fermi surface. Systematics of the single quasineutron levels populated are presented. A large excitation energy gap is observed between levels originating from the 2d3/2, 1h11/2, and 3s1/2 spherical parents (above the N = 64 gap), and the 2d5/2 (below the gap), indicating that the spherical shell model level spacing is maintained at least to moderate deformations

Spectroscopy of \u3csup\u3e88\u3c/sup\u3eY by the (\u3cem\u3ep,dγ\u3c/em\u3e) Reaction

Low-spin, high-excitation energy states in 88Y have been studied using the 89Y(p,dγ) reaction. For this experiment a 25 MeV proton beam was incident upon a monoisotopic 89Y target. A silicon telescope array was used to detect deuterons, and coincident γ rays were detected using a germanium clover array. Most of the known low-excitation-energy low-spin states populated strongly via the (p,d) reaction mechanism are confirmed. Two states are seen for the first time and seven new transitions, including one which bypasses the two low-lying isomeric states, are observed

Measurement of the Entry-Spin Distribution Imparted to the High Excitation Continuum Region of Gadolinium Nuclei Via (\u3cem\u3ep,d\u3c/em\u3e) and (\u3cem\u3ep,t\u3c/em\u3e) Reactions

Over the last several years, the surrogate reaction technique has been successfully employed to extract (n,f) and (n,γ) cross sections in the actinide region to a precision of ∼5% and ∼20%, respectively. However, attempts to apply the technique in the rare earth region have shown large (factors of 2–3) discrepancies between the directly measured (n,γ) and extracted surrogate cross sections. One possible origin of this discrepancy lies in differences between the initial spin-parity population distribution in the neutron induced and surrogate reactions. To address this issue, the angular momentum transfer to the high excitation energy quasicontinuum region in Gd nuclei has been investigated. The (p,d) and (p,t) reactions on 154,158Gd at a beam energy of 25 MeV were utilized. Assuming a single dominant angular momentum transfer component, the measured angular distribution for the (p,d) reactions is well reproduced by distorted-wave Born approximation (DWBA) calculations for ΔL=4 ℏ transfer, whereas the (p,t) reactions are better characterized by ΔL=5 ℏ. A linear combination of DWBA calculations, weighted according to a distribution of L transfers (peaking around ΔL=4–5 ℏ), is in excellent agreement with the experimental angular distributions

Surrogate Measurement of the \u3csup\u3e238\u3c/sup\u3ePu(\u3cem\u3en,f\u3c/em\u3e\u3c/em\u3e) Cross Section

The neutron-induced fission cross section of 238Pu was determined using the surrogate ratio method. The (n,f) cross section over an equivalent neutron energy range 5–20 MeV was deduced from inelastic α-induced fission reactions on 239Pu, with 235U(α,α′f) and 236U(α,α′f) used as references. These reference reactions reflect 234U(n,f) and 235U(n,f) yields, respectively. The deduced 238Pu(n,f) cross section agrees well with standard data libraries up to ~10 MeV, although larger values are seen at higher energies. The difference at higher energies is less than 20%