Instanton contribution to the Sivers function

We study the Sivers function for valence u and d quarks in the proton within the instanton model for QCD vacuum, adopting the MIT bag model wave functions for quarks. Within approaches based on perturbative one-gluon final state interactions a non-zero value of the Sivers function is related to the presence of both S and P wave components in quark wave functions. We show that the instanton-induced chromomagnetic, nonperturbative interaction leads to very specific spin-spin correlations between the struck and spectator quarks, resulting in a non-trivial flavour dependence of the Sivers function. Comparison of the obtained Sivers functions with phenomenological parameterizations is discussed.Comment: 1+12 pages, 4 ps figures; v2: few references and one sentence added in the introduction; final version published in Phys. Lett.

A shrinking Compact Symmetric Object: J11584+2450?

We present multi-frequency multi-epoch Very Long Baseline Array (VLBA) observations of J11584+2450. These observations clearly show this source, previously classified as a core-jet, to be a compact symmetric object (CSO). Comparisons between these new data and data taken over the last 9 years shows the edge brightened hot spots retreating towards the core (and slightly to the west) at approximately 0.3c. Whether this motion is strictly apparent or actually physical in nature is discussed, as well as possible explanations, and what implications a physical contraction of J11584+2450 would have for current CSO models.Comment: 16 pages, 6 figures, 5 tables. Accepted for publication in Ap

Single muscle fiber proteomics reveals unexpected mitochondrial specialization

Mammalian skeletal muscles are composed of multinucleated cells termed slow or fast fibers according to their contractile and metabolic properties. Here, we developed a high-sensitivity workflow to characterize the proteome of single fibers. Analysis of segments of the same fiber by traditional and unbiased proteomics methods yielded the same subtype assignment. We discovered novel subtype-specific features, most prominently mitochondrial specialization of fiber types in substrate utilization. The fiber type-resolved proteomes can be applied to a variety of physiological and pathological conditions and illustrate the utility of single cell type analysis for dissecting proteomic heterogeneity

Iron deficiency prolongs seed dormancy in Arabidopsis plants

The understanding of seed dormancy, germination and longevity are important goals in plant biology, with relevant applications for agriculture, food industry and also human nutrition. Reactive Oxygen Species (ROS) are key molecules involved in the release of dormancy, when their concentrations fall within the so called 'oxidative window'. The mechanisms of ROS distribution and sensing in seeds, from dormant to germinating ones, still need elucidation. Also, the impact of iron (Fe) deficiency on seed dormancy is still unexplored; this is surprising, given the known pro-oxidant role of Fe when in a free form. We provide evidence of a link between plant Fe nutrition and dormancy of progeny seeds by using different Arabidopsis ecotypes and mutants with different dormancy strengths grown in control soil or under severe Fe deficiency. The latter condition extends the dormancy in several genotypes. The focus on the mechanisms involved in the Fe deficiency-dependent alteration of dormancy and longevity promises to be a key issue in seed (redox) biology

Antisense reduction of thylakoidal ascorbate peroxidase in Arabidopsis enhances Paraquat-induced photooxidative stress and Nitric Oxide-induced cell death

The production and characterization of Arabidopsis plants containing a transgene in which the Arabidopsis tAPX is inserted in antisense orientation, is described. tAPX activity in these transgenic tAPX plants is around 50% of control level. The tAPX antisense plants are phenotypically indistinguishable from control plants under normal growth conditions; they show, however, enhanced sensitivity to the O 2- -generating herbicide, Paraquat. Interestingly, the tAPX antisense plants show enhanced symptoms of damage when cell death is triggered through treatment with the nitric oxide-donor, SNP. These results are in accordance with the ones recently obtained with transgenic plants overexpressing tAPX; altogether, they suggest that tAPX, besides the known ROS scavenging role, is also involved in the fine changes of H 2O2 concentration during signaling events

Spatial Descriptions Eliminate the Serial Position Effect

Aims: The present study aims to investigate the occurrence of the serial position effect in the recall of items verbally presented in three different contexts. Background: The serial position effect has been studied with both verbal (e.g., words) and visuospatial (e.g., locations) stimuli but not with verbal-spatial stimuli (i.e., spatial description of an environment). In particular, a spatial description of an environment has both spatial information and a meaningful context. Objective: The objective of the present study is to determine whether the use of different contexts (namely, a classic word list, a spatial description of a room, and a narrative without spatial information) can alter the serial position effect. Methods: Depending on the condition, participants were exposed to a) a list of objects, b) a spatial description of a room containing the same objects; c) a narrative presenting the same objects in lack of spatial information. After this learning phase, participants performed a recognition task. Results: The recognition task revealed different accuracy distributions in the three conditions. In particular, in the spatial description condition, the accuracy distribution did not change across the item position. Conclusion: This result is in line with previous studies with visuospatial stimuli. Thus, it seems that spatial descriptions are a particular kind of verbal stimuli, which are encoded similarly to visuospatial stimuli. Overall, these outcomes support the idea that spatial descriptions elicit a spatial representation, which enhances item retention and eliminates the serial position effect

Efficient second harmonic generation from thin films of V-shaped benzo[b]thiophene based molecules

We have designed an original approach for efficient Second Harmonic Generation of tailored V-shape benzo[b]thiophene molecular systems enabling versatile and flexible one-step, dry and technologically friendly thin film processing. The designed moieties show χ(2) values at least as high as the reference LiNbO3 single crystal, without poling processing and matching the constrains of integrated optical configuration for nonlinear optical devices. This may open the way to a new class of organic materials exploitable for photonic applications

SNARC-like compatibility effects for physical and phenomenal magnitudes: A study on visual illusions

Both numerical and non-numerical magnitudes elicit similar Spatial-Numerical Association of Response Codes (SNARC) effects, with small magnitudes associated with left hand responses and large magnitudes associated with right hand responses (Dehaene, Bossini, Giraux, 1993). In the present study, we investigated whether the phenomenal size of visual illusions elicits the same SNARC-like effect revealed for the physical size of pictorial surfaces. Four experiments were conducted by using the Delboeuf illusion (Experiment 1) and the Kanizsa triangle illusion (Experiments 2, 3 & 4). Experiment 1 suggests the presence of a SNARC-like compatibility effect for the physical size of the inducers, while this effect was not revealed for the phenomenal size of the induced elements, possibly masked by a stronger effect of the inducers. A SNARC-like effect for the phenomenal size of the Kanizsa triangle was revealed when participants directly compared the size of the triangles (Experiment 4). Conversely, when participants performed an indirect task (orientation judgment), the SNARC-like effect was present neither for the illusory nor for the physical displays (Experiments 2 & 3). The effect revealed for the size of illusory triangles was comparable to that of real triangles with physical contours, suggesting that both phenomenal and physical magnitudes similarly elicit SNARC-like effects

Dating COINS: Kinematic Ages for Compact Symmetric Objects

We present multi-epoch VLBA observations of Compact Symmetric Objects (CSOs) from the COINS sample (CSOs Observed In the Northern Sky). These observations allow us to make estimates of, or place limits on, the kinematic ages for those sources with well-identified hot spots. This study significantly increases the number of CSOs with well-determined ages or limits. The age distribution is found to be sharply peaked under 500 years, suggesting that many CSOs die young, or are episodic in nature, and very few survive to evolve into FR II sources like Cygnus A. Jet components are found to have higher velocities than hot spots which is consistent with their movement down cleared channels. We also report on the first detections of significant polarization in two CSOs, J0000+4054 (2.1%) and J1826+1831 (8.8%). In both cases the polarized emission is found in jet components on the stronger side of the center of activity.Comment: 34 pages including 7 figures, Accepted to ApJ on Dec 7, 200