Quantitative assessment of linear noise-reduction filters for spectroscopy.

Linear noise-reduction filters used in spectroscopy must strike a balance between reducing noise and preserving lineshapes, the two conflicting requirements of interest. Here, we quantify this tradeoff by capitalizing on Parseval's Theorem to cast two measures of performance, mean-square error (MSE) and noise, into reciprocal- (Fourier-) space (RS). The resulting expressions are simpler and more informative than those based in direct- (spectral-) space (DS). These results provide quantitative insight not only into the effectiveness of different linear filters, but also information as to how they can be improved. Surprisingly, the rectangular ("ideal" or "brick wall") filter is found to be nearly optimal, a consequence of eliminating distortion in low-order Fourier coefficients where the major fraction of spectral information is contained. Using the information provided by the RS version of MSE, we develop a version that is demonstrably superior to the brick-wall and also the Gauss-Hermite filter, its former nearest competitor.

Temperature and magnetic field effects on electron transport through DNA molecules in a two-dimensional four-channel system.

We utilize a two-dimensional four-channel DNA model, with a tight-binding (TB) Hamiltonian, and investigate the temperature and the magnetic field dependence of the transport behavior of a short DNA molecule. Random variation of the hopping integrals due to the thermal structural disorder, which partially destroy phase coherence of electrons and reduce quantum interference, leads to a reduction of the localization length and causes suppressed overall transmission. We also incorporate a variation of magnetic field flux density into the hopping integrals as a phase factor and observe Aharonov-Bohm (AB) oscillations in the transmission. It is shown that for non-zero magnetic flux, the transmission zero leaves the real-energy axis and moves up into the complex-energy plane. We also point out that the hydrogen bonds between the base pair with flux variations play a role to determine the periodicity of AB oscillations in the transmission.

Metal-insulator transition-induced adsorption-resistant behavior of small Au nanoparticles.

Smaller nonmetallic nanoparticles are more inert: Metal-insulator transition of Au nanoparticles on silica is closely related to the metal-support charge transfer, which has a strong influence on chemisorption reactivity of Au. Smaller nonmetallic Au nanoparticles are more resistant towards butanethiol chemisorption [picture and graph: see text].The size-dependent variation of the electronic and chemical properties of Au nanoparticles formed on native Si oxide surfaces is investigated using synchrotron radiation photoemission spectroscopy and ultraviolet photoelectron spectroscopy. The adsorption reactivity toward butanethiol adsorption initially increases with decreasing particle size; however, the reactivity of Au nanoparticles becomes gradually lower below a size of approximately 0.8 nm. The photoemission spectral changes suggest a metal-insulator transition, accompanied by negative charge transfer from the nanoparticles to the support, which may be the source of the chemical inertness of small Au nanoparticles.

Measurement of serum 3-epi-25-hydroxyvitamin D3, 25-hydroxyvitamin D3 and 25-hydroxyvitamin D2 in infant, paediatric and adolescent populations of Korea using ultra-performance liquid chromatography-tandem mass spectrometry.

Background We evaluated the performance of ultra-performance liquid chromatography-tandem mass spectrometry to measure serum 3-epi-25-hydroxyvitamin D3, 25-hydroxyvitamin D3 and 25-hydroxyvitamin D2 concentrations in 519 infant, paediatric and adolescent serum samples in Korea. Methods We used a Kinetex XB-C18 column and isocratic methanol/water (77.5/22.5, v/v) with 0.025% (v/v) high-performance liquid chromatography solvent additive flowing at 0.25 mL/min, yielding an 11 min/sample run time. A TQD triple quadrupole mass spectrometer in electrospray ionization positive ion mode with multiple reaction monitoring transition via an MSMS vitamin D kit was used to evaluate precision, carryover, ion suppression and linearity. Samples were prepared using the 4-phenyl-1,2,4-triazoline-3,5-dione derivatization method. Results Intra- and inter-run precisions were 1.23-13.28% and 1.02-10.08%, respectively. Group carryovers were -0.27% and 0.10%, respectively. There was no ion suppression. The calibration curve showed good linearity from calibrator Level 1 (11.75 nmol/L) to 6 (375 nmol/L) with R2 > 0.9999. The 3-epi-25-hydroxyvitamin D3 and 25-hydroxyvitamin D3 peaks were clearly separated in the extracted ion chromatogram. Infant serum samples 3-epi-25-hydroxyvitamin D3 concentrations were significantly higher than paediatric and adolescent concentrations. Conclusions The ultra-performance liquid chromatography-tandem mass spectrometry assay performed acceptably, clearly separating 3-epi-25-hydroxyvitamin D3 from 25-hydroxyvitamin D3. High 3-epi-25-hydroxyvitamin D3 concentrations were observed in infant but not in paediatric and adolescent serum samples.

Estrogen and homocysteine.

Cardiovascular diseases are the major causes of illness and death in women. Premenopausal women are relatively protected from coronary artery disease and atherosclerosis as compared to postmenopausal women, and this protection is attributed to the effects of the female sex hormone (estrogen). The vasculature, like the reproductive tissues, bone, liver, and brain, is now recognized as an important site of estrogen's action. Although estrogen's beneficial effects on the cardiovascular system are well described in many studies, the molecular basis of estrogen protective mechanisms are still quite vague. Both genomic mechanisms, mediated primarily through estrogen receptor alpha (ER alpha) and estrogen receptor beta (ER beta), and non-genomic mechanisms, through nitric oxide (NO), of estrogen action are controversial and do not entirely explain the effects of estrogen on vascular preservation during conditions of oxidative stress. Until recently, the atheroprotective effects of estrogen were attributed principally to its effects on serum lipid concentrations and cholesterol levels. However, two recent reports that estrogen therapy has no effect on the progression of coronary atherosclerosis in women with established disease, despite the favorable changes in LDL and cholesterol levels, leads to questions about the lipid/cholesterol mechanism of estrogen-mediated effects on atherosclerosis. Alternatively, the high level of homocysteine, found to correlate with accelerated cardiovascular disease and identified as an independent risk factor for atherosclerosis, was recently described to be diminished by estrogen. Protection against disturbed sulfhydryl metabolism and higher homocysteine level could be the missing link in understanding how exactly estrogen affects vascular cells metabolism and responses to oxidative stress. This review focuses on estrogen/homocysteine interactions and their relevance to the cardiovascular system.

Estradiol prevents homocysteine-induced endothelial injury in male rats.

OBJECTIVE: We investigated whether estradiol may prevent accelerated atherosclerosis due to hyperhomocysteinemia by enhancing the antioxidant system. METHODS: Male Wistar rats were treated with placebo (P) or 1 mg (1E2) and 2 mg (2E2) 17 beta estradiol. Half of the animals (n=6) from each group received homocysteine (Hcy, 100 mg/kg/day) administered in the drinking water for 60 days (P/Hcy, 1E2/Hcy and 2E2/Hcy). Glutathione (GSH) content and glucose-6-phosphate dehydrogenase (G6PDH) activity were determined in myocardial tissues, as well as the serum Hcy concentrations and blood levels of hydrogen peroxide (H(2)O(2)). The relaxation response of aortic ring segments to acetylcholine (ACh) was used for the assessment of endothelial function, and hematoxylin-eosin stained thin sections of rat aorta were used for detection of the histological changes (namely endothelial damage and wall thickening). RESULTS: Depression of relaxation to ACh occurred in P/Hcy compared to P (15.7 +/- 4% vs. 96.3 +/- 7%, P<0.0001), but estrogen significantly restored endothelium dependent relaxation in hyperhomocysteinemic rats (86.8 +/- 9.3%, P<0.001). Histological examination revealed aortic endothelial denudation in P/Hcy while the endothelial structures of the aorta from the 1E2/Hcy and 2E2/Hcy appeared normal. Significant reductions in GSH and G6PDH levels were detected in P/Hcy (1.5 +/- 0.01 micromol/g and 3.21 +/- 1.2 U/mg, respectively) compared to 1E2/Hcy (2.5 +/- 0.3 micromol/g and 12.81 +/- 1.5 U/mg, P<0.001) and 2E2/Hcy (3.11 +/- 1.1 micromol/g and 15.66 +/- 4 U/mg, P<0.001). In addition, blood H(2)O(2) level in 1E2/Hcy and 2E2/Hcy remained low while it was raised significantly in P/Hcy compared to P (P<0.001). CONCLUSIONS: These data suggest that the observed reduction of GSH levels and suppression of G6PDH activity induced by Hcy coupled, with endothelial ultrastructural changes and impaired function, all reversed by estradiol, may have relevance to the mechanisms of atherogenesis and the beneficial effects of estrogen replacement therapy.

Benefits of prophylactic continuous infusion of furosemide after the maze procedure for atrial fibrillation.

OBJECTIVES: One of the most significant complications seen after the maze procedure for atrial fibrillation is excessive fluid retention, with subsequent pulmonary complications. To address this problem we recently started treating all patients prophylactically with a continuous infusion of furosemide starting immediately after the operation. METHODS: Seventy-five consecutive patients with statistically similar demographic characteristics were divided into two groups. In the continuous infusion group (n = 36) furosemide was given intravenously as a continuous infusion at a dose of 2 to 15 mg/h for the first 48 hours after the operation, and in the bolus dose group (n = 39) furosemide was administered in bolus doses (50-100 mg) to maintain a targeted daily urinary output of 25 to 50 mL/kg. Hemodynamic data, urinary output, fluid balance, daily weights, and pulmonary complications were recorded during the first 48 hours after the operation. RESULTS: The mean postoperative urinary output was higher, the total furosemide dose was lower, and the pulmonary complications were fewer in the continuous infusion group than in the bolus dose group. Three patients in the bolus dose group were reintubated after the operation, whereas none in the continuous infusion group were reintubated. Supplemental oxygen requirements were greater in the bolus dose group (7 vs 4 patients, P <.05). In the bolus dose group, 4 patients (10%) required thoracentesis and 3 patients (8%) required chest tube insertions for postoperative pleural effusions, in contrast with 1 patient (3%) each in the continuous infusion group (P <.05). CONCLUSION: Despite a smaller total dose relative to bolus infusion, prophylactic continuous furosemide infusion decreased the adverse pulmonary complications associated with excessive fluid retention in patients undergoing the maze procedure for atrial fibrillation.

17-beta estradiol preserves endothelial cell viability in an in vitro model of homocysteine-induced oxidative stress.

High levels of homocysteine (Hcy) accelerate endothelial cell damage by producing hydrogen peroxide (H(2)O(2)). We investigated whether 17-beta estradiol may prevent the accelerated rate of endothelial cell detachment and reduced cell viability in cultured endothelial cells challenged with Hcy. Cultured bovine aortic endothelial cells (BAEC) were incubated for 72-h with either vehicle (alcohol) or different concentrations of 17-beta estradiol (1 nM [1E2] and 10 nM [10E2]) before being challenged with 0.5 mM of Hcy. Cell viability and H(2)O(2) levels were evaluated at 30 min, 1-, 2-, 4-, 8-, and 24-h after adding Hcy. Cell suspensions were frozen in liquid nitrogen and used later for spectrophotometric measurement of intracellular glutathione (GSH) levels. Cell viability 24 h after Hcy administration was significantly lower in vehicle versus 1 nM and 10 nM 17-beta estradiol (44 +/- 5% vs. 70.66 +/- 4%, [p < 0.001] and 79 +/- 5% respectively, [p < 0.001]). H(2)O(2) levels were higher in vehicle (1 +/- 0.05 microM) compared with 1E2 and 10E2 (0.8 +/- 0.1 microM, p = 0.02 and 0.1 +/- 0.05 microM, respectively, p < 0.001), whereas GSH content was increased in 1E1 and 10E2 versus control (27.69 +/- 4.6 nM/10(6) cells and 43.49 +/- 5.5 nM/10(6) cells vs. 13.33 +/- 1.5 nM/10(6) cells, p < 0.001). Bovine aortic endothelial cells treatment with 17-beta estradiol (0, 1, and 10 nM) and 0.1 mmol buthionine sulfoximine, an inhibitor of gamma-glutamylcysteine synthase, abolished the beneficial effects of estradiol alone on cell viability, GSH content, and H2O2 generation. Estradiol prevents Hcy-induced endothelial cell injury by increasing the intracellular content of GSH.