Search results for "Photon"
showing 10 items of 3171 documents
Study of Bs->PhiGamma decays at LHCb
2021
This thesis describes two different analyses performed at LHCb using the B0s→φγ and B0→K∗0γ decay channels. First, the measurement of the ratio of branching fractions B(B0→K∗0γ)/B(B0s→φγ) is presented, giving the most precise value for B(B0s→φγ) to date. Secondly, the CP-violating observables S and C, as well as the mixing-induced A∆ parameter are measured through a time-dependent analysis of the B0s→φγ decay channel, this being the first time the S and C observables are probed in the Bs system. These studies are performed using data collected in 2011 and 2012 by the LHCb experiment at CERN, corresponding to an integrated luminosity of 3.0 fb−1 of pp collisions at a center-of-mass energy of…
Purcell Enhancement and Wavelength Shift of Emitted Light by CsPbI3 Perovskite Nanocrystals Coupled to Hyperbolic Metamaterials
2020
Manipulation of the exciton emission rate in nanocrystals of lead halide perovskites (LHPs) was demonstrated by means of coupling of excitons with a hyperbolic metamaterial (HMM) consisting of alternating thin metal (Ag) and dielectric (LiF) layers. Such a coupling is found to induce an increase of the exciton radiative recombination rate by more than a factor of three due to the Purcell effect when the distance between the quantum emitter and HMM is nominally as small as 10 nm, which coincides well with the results of our theoretical analysis. Besides, an effect of the coupling-induced long wavelength shift of the exciton emission spectrum is detected and modeled. These results can be of i…
Rosenbluth separation of the $\pi^0$ Electroproduction Cross Section off the Neutron
2017
We report the first longitudinal/transverse separation of the deeply virtual exclusive $\pi^0$ electroproduction cross section off the neutron and coherent deuteron. The corresponding four structure functions $d\sigma_L/dt$, $d\sigma_T/dt$, $d\sigma_{LT}/dt$ and $d\sigma_{TT}/dt$ are extracted as a function of the momentum transfer to the recoil system at $Q^2$=1.75 GeV$^2$ and $x_B$=0.36. The $ed \to ed\pi^0$ cross sections are found compatible with the small values expected from theoretical models. The $en \to en\pi^0$ cross sections show a dominance from the response to transversely polarized photons, and are in good agreement with calculations based on the transversity GPDs of the nucle…
The charm-quark contribution to light-by-light scattering in the muon (−2) from lattice QCD
2022
We compute the hadronic light-by-light scattering contribution to the muon $g-2$ from the charm quark using lattice QCD. The calculation is performed on ensembles generated with dynamical $(u,d,s)$ quarks at the SU(3)$_{\rm f}$ symmetric point with degenerate pion and kaon masses of around 415 MeV. It includes the connected charm contribution, as well as the leading disconnected Wick contraction, involving the correlation between a charm and a light-quark loop. Cutoff effects turn out to be sizeable, which leads us to use lighter-than-physical charm masses, to employ a broad range of lattice spacings reaching down to 0.039 fm and to perform a combined charm-mass and continuum extrapolation.…
Projection and Pinhole-Based Data Acquisition for Small-Animal SPECT Using Storage Phosphor Technology
2007
Three-dimensional Single Photon Emission Computed Tomography (SPECT) can provide high-resolution insight into biomolecular distribution and pharmacokinetics. However, instrument availability and distribution is limited at present,and imaging times can be considerable. To evaluate the large array of novel agents which are becoming available,we find that storage phosphor-based in vivo imaging can provide an important,rapid-throughput transition from the traditional ex vivo sacrifice/gamma counting and autoradiography to full-time course SPECT.
Association between low-frequency ultrasound and hip fractures - comparison with DXA-based BMD
2013
Background New methods for diagnosing osteoporosis and evaluating fracture risk are being developed. We aim to study the association between low-frequency (LF) axial transmission ultrasound and hip fracture risk in a population-based sample of older women. Methods The study population consisted of 490 community-dwelling women (78–82 years). Ultrasound velocity (VLF) at mid-tibia was measured in 2006 using a low-frequency scanning axial transmission device. Bone mineral density (BMD) at proximal femur measured using dual-energy x-ray absorptiometry (DXA) was used as the reference method. The fracture history of the participants was collected from December 1997 until the end of 2010. Lifestyl…
Relationship of sex hormones to bone geometric properties and mineral density in early pubertal girls.
2004
This study aimed to evaluate the associations among serum 17beta-estradiol (E2), testosterone (T), sex hormone-binding globulin (SHBG), bone geometric properties, and mineral density in 248 healthy girls between the ages of 10 and 13 yr old. The left tibial shaft was measured by peripheral quantitative computed tomography (Stratec XCT-2000; Stratec Medizintechnik, GmbH, Pforzheim, Germany). The cortical bone and marrow cavity areas were expressed as proportions of the total tibial cross-sectional area (CSA). Cortical thickness and total volumetric bone mineral density (vBMD) were also determined. These tibial geometric and densitometric measures were correlated against the serum sex hormone…
Radiodensitometric study for evaluation of bone mineral density around dental implants after zoledronic acid treatment in ovariectomized rats
2017
Background The purpose of this study was to evaluate the effects of intravenous zoledronic acid applied systemically on osseointegration of dental implants and the surrounding bone mineral density (BMD) in the ovariectomized rats. Material and Methods 36 rats were divided into three groups: control (CTRL), ovariectomy (OVX), and ovariectomy-zoledronic acid (OVX/ZOL). The rats in the CTRL group underwent sham surgery, while rats in OVX and OVX / ZOL group underwent ovariectomy. After 12 weeks, rats from OVX / ZOL were injected with 0.04 mg/kg ZOL intravenously once a week for 6 weeks. The rats from CTRL and OVX groups were injected with 0.9% NaCl. Implants were placed in the left tibia. Afte…
The COMT val158met Polymorphism Is Associated with Early Pubertal Development, Height and Cortical Bone Mass in Girls
2005
Estrogens are involved in accretion of bone mass during puberty. Catechol-O-Methyltransferase (COMT) is involved in the degradation of estrogens. In this cross-sectional study we investigated associations between the COMT val158met polymorphism, which results in a 60-75% difference in enzyme activity between the val (high activity = H) and the met (low activity = L) variant, and skeletal phenotypes in 246 healthy pre/early pubertal girls. Girls with COMT(LL) were 5.4 cm taller than COMT(HH) girls. Dual x-ray absorptiometry showed higher values of bone mineral content (BMC), and larger areas of total body, femur and spine in COMT(LL). Cortical BMC, measured by peripheral quantitative compute…
Estrogen receptor alpha polymorphism modifies the association between childhood exercise and bone mass: follow-up study.
2007
This follow-up study confirms our previous findings that the ER-α PvuII polymorphism (Pp) modulates the association between exercise and bone mass. The differences in bone properties of girls with consistently low physical activity (LLPA) and consistently high physical activity (HHPA) were evident only in those bearing the heterozygote ER-α genotype (Pp). In particular, areal bone mineral density of the total femur, bone mineral content and areal bone mineral density of the femoral neck, and bone mineral content and cortical thickness of the tibia shaft were significantly (p < .05) lower in the Pp girls with LLPA than in their HHPA counterparts. These findings might partly explain the ge…