introduction: osteoporosis is a bone disease in which there is a reduction in the amount of bone mineral content leading to an increase in the risk of bone fractures. the affected individuals not only have to go through lots of pain and suffering but this disease also results in high economic costs to the society due to a large number of fractures.  a timely and accurate diagnosis of this disea...

Introduction: Osteoporosis is a bone disease in which there is a reduction in the amount of bone mineral content leading to an increase in the risk of bone fractures. The affected individuals not only have to go through lots of pain and suffering but this disease also results in high economic costs to the society due to a large number of fractures.  A timely and accurate diagnosis of this disea...

Efficient upconversion of photoluminescence (PL) from donor bound excitons is revealed in bulk and nanorod ZnO. Based on excitation power dependent PL measurements performed with different energies of excitation photons, two-photon-absorption (TPA) and two-step TPA (TS-TPA) processes are concluded to be responsible for the upconversion. The TS-TPA process is found to occur via a defect/impurity...

We study the porphyrin S1 ! S0 fluorescence and the photosensitized singlet oxygen Dg ! Rg phosphorescence, both originating from absorption of photons with energy less than the porphyrin S0 ! S1 transition energy. By measuring the excitation intensity dependence of fluorescence at lowered sample temperatures, we are able to discriminate between two parallel processes of one-photon hot-band abs...

Electronic spectroscopy of nine benzannelated enediynes and a related fulvene was studied under one-photon and two-photon excitation conditions. We utilize measured absorbance and emission spectra and time-resolved fluorescence decays of these molecules to calculate their radiative lifetimes and fluorescence quantum yields. The fluorescence quantum yields for the other compounds were referenced...

Two-photon absorption (TPA) allows accessing “dark” states of matter that are otherwise inaccessible to light, which serve as important building blocks for quantum information processing. In a semiconductor microcavity, TPA-driven condensation strongly coupled light-matter exciton–polaritons can enable new solid-state simulations state-condensate interactions and was predicted stimulate THz emi...

We report the observation of interband two-photon absorption (TPA) saturation in cadmium sulfide nanocrystals (CdS NCs) under intense femtosecond laser excitation with 1.6 eV photon energy. The observation has been compared to interband TPA saturation in bulk CdS under the same experimental conditions. By using both Z-scan techniques and transient absorption measurements, the saturation intensi...

The usual fluorescence behavior follows Stokes law, where exciting photons are of higher energy than emitted photons. Anti-Stokes processes usually concern emitted energies in excess of excited energies by only a few kT. These processes include anti-Stokes emission by the thermal bands or by the Raman effect. There are processes, however, in which emission photon energy exceeds excited photon e...

the objective of this study was to validate the use of bone mineral measurements of the calcaneus bone by dual x-ray and laser (dxl) in a cross-sectional study carried out in an osteoporosis clinic. measurements of bone mineral density (bmd) at proximal femur and spine were obtained by dual-energy photon x-ray absorptiometry (dexa). osteoporosis was defined by a dexa t-score <-2.5 at the femora...

We investigate theoretically the two-photon absorption (TPA) for circular graphene quantum dots (GQDs) with the edge of armchair and zigzag on the basis of electronic energy states obtained by solving the Dirac-Weyl equation numerically under finite difference method. The expressions for TPA cross section are derived and the transition selection rules are obtained. Results reveal that the TPA i...