Towards a Mg Lattice Clock: Observation of the

We optically excite the electronic state 3s3p ^{3}P_{0} in ^{24}Mg atoms, laser cooled and trapped in a magic-wavelength lattice. An applied magnetic field enhances the coupling of the light to the otherwise strictly forbidden transition. We determine the magic wavelength, the quadratic magnetic Zeeman shift, and the transition frequency to be 468.46(21) nm, -206.6(2.0) MHz/T^{2}, and 655 058 646 691(101) kHz, respectively. These are compared with theoretical predictions and results from complementary experiments. We also develop a high-precision relativistic structure model for magnesium, give an improved theoretical value for the blackbody radiation shift, and discuss a clock based on bosonic magnesium.

The X(1)Σg(+) ground state of Mg2 studied by Fourier-transform spectroscopy.

The A(1)Σu(+) - X(1)Σg(+) UV spectrum of Mg2 has been investigated with high resolution Fourier-transform spectroscopy. Mg2 vapor was created in a heat pipe. Various spectroscopic methods have been employed, such as conventional absorption spectroscopy with light from a broad band lamp and laser-induced fluorescence. The high resolution of the Fourier-transform spectrometer, together with computer aided evaluation methods of the spectra, yields precise transition frequencies. The new data and data available from earlier investigations are applied in direct potential fits of lower and upper electronic states. Various representations of potential energy curves for the ground state X(1)Σg(+) have been employed and their benefits in terms of smallest number of parameters are discussed. Scattering lengths are derived for the homonuclear isotopologues and compared with previous results.

Nondestructive application of laser-induced fluorescence spectroscopy for quantitative analyses of phenolic compounds in strawberry fruits (Fragaria x ananassa).

Laser-induced fluorescence spectroscopy (LIFS) was nondestructively applied on strawberries (EX = 337 nm, EM = 400-820 nm) to test the feasibility of quantitatively determining native phenolic compounds in strawberries. Eighteen phenolic compounds were identified in fruit skin by UV and MS spectroscopy and quantitatively determined by use of rp-HPLC for separation and diode-array or chemical reaction detection. Partial least-squares calibration models were built for single phenolic compounds by means of nondestructively recorded fluorescence spectra in the blue-green wavelength range using different data preprocessing methods. The direct orthogonal signal correction resulted in r (2) = 0.99 and rmsep < 8% for p-coumaroyl-glucose, and r (2) = 0.99 and rmsep < 24% for cinnamoyl-glucose. In comparison, the correction of the fluorescence spectral data with simultaneously recorded reflectance spectra did not further improve the calibration models. Results show the potential of LIFS for a rapid and nondestructive assessment of contents of p-coumaroyl-glucose and cinnamoyl-glucose in strawberry fruits.

The mechanical properties of cancellous bone in the proximal tibia of ovariectomized rats.

The "mature rat model" is an effective and often-used surrogate for studying mechanisms and characteristics of estrogen-deficient osteopenia. The purpose of this study was to extend our understanding of this animal model to include the mechanical properties of cancellous bone in the proximal tibia. Female Sprague-Dawley rats were divided into two groups (n=13 each) at 14 weeks of age: an ovariectomized group (OVX) and a sham-operated control group (sham). The study terminated after a duration of 5 weeks. Specimens 2 mm long were cut from the proximal tibial metaphysis just below the growth plate and tested using two methods: (1) "whole-slice" compression, in which the entire specimen is loaded between two larger flat platens and (2) "reduced-platen" compression (RPC), which uses platens sized and aligned to load only the cancellous bone in the center of the sample. Three-point bending tests also were conducted on the femur. The short duration of estrogen deficiency yielded only minimal differences (< 10%) in femoral cortical bone but dramatic reductions (approximately 60%) in cancellous bone properties as determined by the RPC method. Ultimate stress was 7.23 MPa +/- 1.97 MPa for OVX versus 18.1 MPa +/- 5.21 MPa for sham; and elastic modulus was 252 MPa +/- 104 MPa for OVX versus 603 MPa +/- 180 MPa for sham. These changes in mechanical properties are similar in many respects to the dramatic effects reported in histomorphometric studies. For the whole-slice method, differences in mechanical properties between the two groups were not as large because the test directly loads both cancellous and cortical bone, and the latter is not affected as severely by estrogen deficiency. In this case, ultimate stress and elastic modulus were only 30% (or less) lower for the OVX group.