The Cottingham formula expresses the leading contribution of the electromagnetic interaction to the proton-neutron mass difference as an integral over the forward Compton amplitude. Since quarks and ...gluons reggeize, the dispersive representation of this amplitude requires a subtraction. We assume that the asymptotic behaviour is dominated by Reggeon exchange. This leads to a sum rule that expresses the subtraction function in terms of measurable quantities. The evaluation of this sum rule leads to
m
QED
p
-
n
=
0.58
±
0.16
MeV
.
The Cottingham formula expresses the electromagnetic part of the mass of a particle in terms of the virtual Compton scattering amplitude. At large photon momenta, this amplitude is dominated by short ...distance singularities associated with operators of spin 0 and spin 2. In the difference between proton and neutron, chiral symmetry suppresses the spin 0 term. Although the angular integration removes the spin 2 singularities altogether, the various pieces occurring in the standard decomposition of the Cottingham formula do pick up such contributions. These approach asymptotics extremely slowly because the relevant Wilson coefficients only fall off logarithmically. We rewrite the formula in such a way that the leading spin 2 contributions are avoided ab initio. Using a sum rule that follows from Reggeon dominance, the numerical evaluation of the e.m. part of the mass difference between proton and neutron yields mQED=0.58±0.16MeV. The result indicates that the inelastic contributions are small compared to the elastic ones.
A wide range of complementary research technique - XRD, SEM, TEM, MFM, HV, and low temperature heat capacity, in situ neutron diffraction, resistivity, vibrating sample magnetometry, internal ...friction, dilatometry, and differential scanning calorimetry - is applied to study structure and phase transitions at heating and cooling of two Fe–Ga functional alloys with 25 and 27 at.% Ga. Using high resolution neutron diffraction, it is unambiguously proven that the initial state of both as-cast samples at room temperature is the D03 phase which results from ordering of the high temperature A2 phase during cooling. Heating of as-cast samples and their subsequent cooling leads to a cascade of phase transitions which change the samples’ structural, mechanical and physical properties. These transitions and properties are discussed in the paper. Transition from metastable D03 to stable L12 phase at heating or isothermal annealing leads to significant changes in macro (grain size) and micro (ordering) structure, hardness and magnetic properties (magnetostriction, magnetization). According to our structural studies (ND, XRD), composition Fe-25.5 at.%Ga below ∼600 °C belongs to a single phase (L12) range of the equilibrium phase diagram, while in the Fe-26.9Ga alloy some amount of the D019 phase is also present.
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•Phase transition for two galfenol alloys were studied during heating and cooling.•A complementary research technique is applied to the study.•Electrical-resistivity is used for the first time to characterize phase transitions.•The initial state of the two alloys consists of D03 and B2 ordered clusters.•Phase transition from metastable D03 to stable L12 changes magnetic properties.
Contribution to Special Issue on Fast effects of steroids.
Corticosteroid hormones act at intracellular glucocorticoid receptors (GR) and mineralocorticoid receptors (MR) to alter gene expression, ...leading to diverse physiological and behavioral responses. In addition to these classical genomic effects, corticosteroid hormones also exert rapid actions on physiology and behavior through a variety of non-genomic mechanisms, some of which involve GR or MR, and others of which are independent of these receptors. One such GR-independent mechanism involves corticosteroid-induced inhibition of monoamine transport mediated by “uptake2” transporters, including organic cation transporter 3 (OCT3), a low-affinity, high-capacity transporter for norepinephrine, epinephrine, dopamine, serotonin and histamine. Corticosterone directly and acutely inhibits OCT3-mediated transport. This review describes the studies that initially characterized uptake2 processes in peripheral tissues, and outlines studies that demonstrated OCT3 expression and corticosterone-sensitive monoamine transport in the brain. Evidence is presented supporting the hypothesis that corticosterone can exert rapid, GR-independent actions on neuronal physiology and behavior by inhibiting OCT3-mediated monoamine clearance. Implications of this mechanism for glucocorticoid-monoamine interactions in the context-dependent regulation of behavior are discussed.
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•Organic cation transporter 3 (OCT3) is a corticosterone-sensitive transport protein.•OCT3 substrates include norepinephrine, epinephrine, dopamine, and serotonin.•OCT3 is expressed in brain glial and neuronal cells and in peripheral organs.•OCT3 may play an important role in context-dependent effects of glucocorticoids.•OCT3 impact on stress-related psychiatric disorders is an important area for future study.
Cottingham formula and nucleon polarisabilities Gasser, J.; Hoferichter, M.; Leutwyler, H. ...
The European physical journal. C, Particles and fields,
08/2015, Volume:
75, Issue:
8
Journal Article
Peer reviewed
Open access
The difference between the electromagnetic self-energies of proton and neutron can be calculated with the Cottingham formula, which expresses the self-energies as an integral over the ...electroproduction cross sections – provided the nucleon matrix elements of the current commutator do not contain a fixed pole. We show that, under the same proviso, the subtraction function occurring in the dispersive representation of the virtual Compton forward scattering amplitude is determined by the cross sections. The representation in particular leads to a parameter-free sum rule for the nucleon polarisabilities. We evaluate the sum rule for the difference between the electric polarisabilities of proton and neutron by means of the available parameterisations of the data and compare the result with experiment.
Regional alterations in kinetics of catecholamine uptake are due in part to variations in clearance mechanisms. The rate of clearance is a critical determinant of the strength of catecholamine ...signaling. Catecholamine transmission in the nucleus accumbens core (NAcc) and basolateral amygdala (BLA) is of particular interest due to involvement of these regions in cognition and motivation. Previous work has shown that catecholamine clearance in the NAcc is largely mediated by the dopamine transporter (DAT), but clearance in the BLA is less DAT‐dependent. A growing body of literature suggests that organic cation transporter 3 (OCT3) also contributes to catecholamine clearance in both regions. Consistent with different clearance mechanisms between regions, catecholamine clearance is more rapid in the NAcc than in the BLA, though mechanisms underlying this have not been resolved. We compared the expression of DAT and OCT3 and their contributions to catecholamine clearance in the NAcc and BLA. We found DAT protein levels were ~ 4‐fold higher in the NAcc than in the BLA, while OCT3 protein expression was similar between the two regions. Immunofluorescent labeling of the two transporters in brain sections confirmed these findings. Ex vivo voltammetry demonstrated that the magnitude of catecholamine release was greater, and the clearance rate was faster in the NAcc than in the BLA. Additionally, catecholamine clearance in the BLA was more sensitive to the OCT3 inhibitor corticosterone, while clearance in the NAcc was more cocaine sensitive. These distinctions in catecholamine clearance may underlie differential effects of catecholamines on behavioral outputs mediated by these regions.
OCT3 has a greater role in catecholamine uptake in the BLA than in the NAcc. The DAT is more highly expressed in the NAcc than the BLA, whereas OCT3 is expressed similarly between the regions. In the BLA, uptake is far more inhibited by corticosterone (an OCT3 blocker) than it is within the NAcc.Abs.
In the conventional model of serotonin neurotransmission, serotonin released by neurons in the midbrain raphe nuclei exerts its actions on forebrain neurons by interacting with a large family of ...post-synaptic receptors. The actions of serotonin are terminated by active transport of serotonin back into the releasing neuron, which is mediated by the serotonin reuptake transporter (SERT). Because SERT is expressed pre-synaptically and is widely thought to be the only serotonin transporter in the forebrain, the conventional model does not include serotonin transport into post-synaptic neurons. However, a large body of evidence accumulating since the 1970s has shown that serotonin, despite having a positive charge, can cross cell membranes through a diffusion-like process. Multiple low-affinity, high-capacity, sodium-independent transporters, widely expressed in the brain, allow the carrier-mediated diffusion of serotonin into forebrain neurons. The amount of serotonin crossing cell membranes through this mechanism under physiological conditions is considerable. Most prominent textbooks fail to include this alternative method of serotonin uptake in the brain, and even most neuroscientists are unaware of it. This failure has limited our understanding of a key regulator of serotonergic neurotransmission, impeded research on the potential intracellular actions of serotonin in post-synaptic neurons and glial cells, and may have impeded our understanding of the mechanism by which antidepressant medications reduce depressive symptoms.
The temperature and time dependent structure of molten NiP alloy of eutectic composition has been studied by neutron diffraction. Ni particles were found to exist in the melt at temperatures at least ...up to about 150 degrees above liquidus. The amount varies reversibly as temperature increases but decays slowly with time. Remarkably, particles still exist even after that the melt has been kept more than 30 h at different temperatures in the molten state. The static structure factor and the pair distribution function obtained at 1050 °C are presented.
•Ni particles exist in Ni81P19 melt at temperatures at least up to about 150 degrees above liquidus.•Particles still exist in NiP melt even after it was kept >30 h in the molten state.•The amount of particles in NiP melt increases reversibly with temperature but decays with time.
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