Kinematic Cusps: Determining the Missing Particle Mass at Colliders

In many extensions of the SM, neutral massive stable particles (dark matter candidates) are produced at colliders in pairs due to an exact symmetry called a "parity". These particles escape detection, rendering their mass measurement difficult. In the pair production of such particles via a specific ("antler") decay topology, kinematic cusp structures are present in the invariant mass and angular distributions of the observable particles. Together with the end-points, such cusps can be used to measure the missing particle mass and the intermediate particle mass in the decay chain. Our simulation of a benchmark scenario in a Z' supersymmetric model shows that the cusp feature survives under the consideration of detector simulation and the standard model backgrounds. This technique for determining missing particle masses should be invaluable in the search for new physics at the LHC and future lepton colliders.Comment: final version in Phys. Lett.

Principal factors that determine the extension of detection range in molecular beacon aptamer/conjugated polyelectrolyte bioassays.

A strategy to extend the detection range of weakly-binding targets is reported that takes advantage of fluorescence resonance energy transfer (FRET)-based bioassays based on molecular beacon aptamers (MBAs) and cationic conjugated polyelectrolytes (CPEs). In comparison to other aptamer-target pairs, the aptamer-based adenosine triphosphate (ATP) detection assays are limited by the relatively weak binding between the two partners. In response, a series of MBAs were designed that have different stem stabilities while keeping the constant ATP-specific aptamer sequence in the loop part. The MBAs are labeled with a fluorophore and a quencher at both termini. In the absence of ATP, the hairpin MBAs can be opened by CPEs via a combination of electrostatic and hydrophobic interactions, showing a FRET-sensitized fluorophore signal. In the presence of ATP, the aptamer forms a G-quadruplex and the FRET signal decreases due to tighter contact between the fluorophore and quencher in the ATP/MBA/CPE triplex structure. The FRET-sensitized signal is inversely proportional to [ATP]. The extension of the detection range is determined by the competition between opening of the ATP/MBA G-quadruplex by CPEs and the composite influence by ATP/aptamer binding and the stem interactions. With increasing stem stability, the weak binding of ATP and its aptamer is successfully compensated to show the resistance to disruption by CPEs, resulting in a substantially broadened detection range (from millimolar up to nanomolar concentrations) and a remarkably improved limit of detection. From a general perspective, this strategy has the potential to be extended to other chemical- and biological-assays with low target binding affinity

Extraction of higher-order nonlinear electronic response to strong field excitation in solids using high harmonic generation

State-of-the-art experiments employ strong ultrafast optical fields to study the nonlinear response of electrons in solids on an attosecond time-scale. Notably, a recent experiment retrieved a 3rd order nonlinear susceptibility by comparing the nonlinear response induced by a strong laser field to a linear response induced by the otherwise identical weak field. In parallel, experiments have demonstrated high harmonic generation (HHG) in solids, a highly nonlinear process that until recently had only been observed in gases. The highly nonlinear nature of HHG has the potential to extract even higher order nonlinear susceptibility terms, and thereby characterize the entire response of the electronic system to strong field excitation. However, up till now, such characterization has been elusive due to a lack of direct correspondence between high harmonics and nonlinear susceptibilities. Here, we demonstrate a regime where such correspondence can be clearly made, extracting nonlinear susceptibilities (7th, 9th, and 11th) from sapphire of the same order as the measured high harmonics. The extracted high order susceptibilities show angular-resolved periodicities arising from variation in the band structure with crystal orientation. Nonlinear susceptibilities are key to ultrafast lightwave driven optoelectronics, allowing petahertz scaling manipulation of the signal. Our results open a door to multi-channel signal processing, controlled by laser polarization

Atomic resolution of the crystal structure of the hyperthermophilic family 12 endocellulase and stabilizing role of the DxDxDG calcium-binding motif in Pyrococcus furiosus

AbstractHyperthermophilic glycoside hydrolase family 12 endocellulase (EGPf) from the archaeon Pyrococcus furiosus catalyzes the hydrolytic cleavage of β-1,4-glucosidic linkage in β-glucan cellulose. A truncated EGPf (EGPfΔN30) mutant lacking the proline and hydroxyl-residue rich region at the N terminus was constructed, and its crystal structure was resolved at an atomic resolution of 1.07Å. Our results indicate that the structure of EGPf, which consists of a β-jelly roll, exhibits structural similarity with the endocellulase of Thermotoga maritima. Additionally, we further determined that the thermostability of EGPf is maintained in part by the binding of Ca2+ in a DxDxDG Ca2+-binding motif, atypical of most archaeal proteins

Work and Family Pathways and Their Associations with Health for Young Women in Korea

The aim of this study is two-fold: to discern patterns in pathways of work and family transitions among young women (aged 24–39 years) whose decisions and behaviors toward labor force participation, marriage, and parenthood are considerably shaped by social constraints and gender norms; and to examine whether and to what extent work and family pathways are associated with later health. Using data from a longitudinal survey based on a large sample of adult women in Korea (N = 2418), we identified eight dominant pathways of employment, marriage, and parenthood among young women and found that educational attainment and family values are strong predictors of these work–family pathways. We also found that the timing and sequencing of work–family pathways appears to be associated with later health outcomes. In particular, unemployed women who are not married and do not have children seem to be vulnerable to health problems, compared to those with other pathways. We discuss the implications of our findings regarding the occurrence of work and/or family transitions, as well as their timing and sequencing for women’s health in later life