In recent years, up-conversion luminescence nanoparticles have attracted significant attention from researchers in fields such as analytical chemistry (for example qualitative and quantitative ...analysis of metal and non-metal ions) and biomedicine (cancer imaging, drug delivery, treatment, etc.) due to their high rate of emission efficiency, easy surface functionalization, great chemical and thermal and photostability and other favorable properties. NaYF
in particular has attracted interest of researchers as a host material due to its low phonon energy, thus increasing the efficiency of emission. In this study, the synthesis of NaYF
:Yb
,Tm
nanocrystals using the hydrothermal method was successfully carried out. Refined sunflower oil containing oleic acid was used as a solvent instead of analytical grade oleic acid and octadecene-1, reducing the cost of the synthesis. Using semi-quantitative XRD measurement analysis, it was determined that 25.3 % hexagonal β-NaYF
:Yb
,Tm
as well as 23.8 % cubic α-NaYF
nanocrystal crystalline phases were found in the synthesized sample. The sample showed mainly luminescent characteristics typical of hexagonal NaYF
:Yb
,Tm
lattice nanoparticles.
Attention deficit hyperactivity disorder (ADHD) is a common neuropsychiatric condition that has been strongly associated with changes in sleep and circadian rhythms. Circadian rhythms are near 24-h ...cycles that are primarily generated by an endogenous circadian timekeeping system, encoded at the molecular level by a panel of clock genes. Stimulant and non-stimulant medication used in the management of ADHD has been shown to potentially impact on circadian processes and their behavioral outputs. In the current study, we have analyzed circadian rhythms in daily activity and sleep, and the circadian gene expression in a cohort of healthy controls (N = 22), ADHD participants not using ADHD-medication (N = 17), and participants with ADHD and current use of ADHD medication (N = 17). Rhythms of sleep/wake behavior were assessed via wrist-worn actigraphy, whilst rhythms of circadian gene expression were assessed ex-vivo in primary human-derived dermal fibroblast cultures. Behavioral data indicate that patients with ADHD using ADHD-medication have lower relative amplitudes of diurnal activity rhythms, lower sleep efficiency, more nocturnal activity but not more nocturnal wakenings than both controls and ADHD participants without medication. At the molecular level, there were alterations in the expression of PER2 and CRY1 between ADHD individuals with no medication compared to medicated ADHD patients or controls, whilst CLOCK expression was altered in patients with ADHD and current medication. Analysis of fibroblasts transfected with a BMAL1:luc reporter showed changes in the timing of the peak expression across the three groups. Taken together, these data support the contention that both ADHD and medication status impact on circadian processes.
We report the spectral dependence of the nonlinear refractive index (
γ
) of carbon disulfide (CS
2
) in the range of 400–1100 nm in the case of the femtosecond laser pulses. The positive sign of
γ
...dominated in the region between 600 and 1100 nm. At a shorter wavelength (500 nm), we observed the intensity-dependent competition between the fifth-order related self-defocusing and third-order related self-focusing. Further decrease of the wavelength of the probe pulses (400 nm) resulted in domination of the negative nonlinear refraction. The fifth-order nonlinear refractive index of CS
2
at
λ
= 400 nm (
η
= −4×10
−22
cm
4
W
−2
) is determined.
•Evaluation of mitochondrial function in PBMC at different time points.•Sex differences in mitochondrial function and serum melatonin concentrations.•Mitochondrial parameters and melatonin blood ...levels were lower in males.•Endogenous melatonin concentration may influence mitochondrial function.•Studies on mitochondrial function should consider endogenous melatonin levels.
Melatonin blood levels vary depending on the circadian rhythm. It also stimulates antioxidant enzymes and has positive effects on mitochondrial function. The current study investigated the effects of endogenously released melatonin on adenosine triphosphate (ATP) levels and mitochondrial respiration in peripheral blood mononuclear cells (PBMC).
The current study included 20 healthy adults (mean age 25,7 ± 3.4 years). Blood was collected at 8 a.m. and 2 p.m. The activity of mitochondrial respiratory complexes and ATP levels were determined in isolated PBMC. Melatonin concentrations were determined in serum samples. Sleep behavior was assessed.
In PBMCs isolated from blood samples of males, respiration of mitochondrial complex IV and ATP levels as well as serum melatonin concentration were significantly lower at 2 a.m. compared to the samples collected at 8 p.m. Mitochondrial parameters and melatonin blood levels were equal at both time points in the samples isolated from females.
Although our results show that the amount of melatonin secreted may have had an influence, further investigation is needed to determine the importance of melatonin and other factors in measuring the mitochondrial function of PBMC.
We demonstrate high conversion efficiency towards the third harmonic (TH) of the 900–1700 nm, 150 fs laser in the thin (40–120 nm) films containing quantum dots (HgTe, HgSe, and PbS) and exfoliated ...nanoparticles (Bi
2
Te
3
) deposited on the glass substrates. The ratio of TH conversion efficiencies in the films and glasses of the same thickness was estimated to be > 10
4
. The intensity, polarization, and spectral dependencies of this process in thin films are reported. We discuss the relation between the TH process and the low-order nonlinear optical properties of these quantum dots and nanoparticles.
Native defect-induced photoluminescence around 400nm (blue luminescence - BL) was studied in hBN materials with different size and various origins. The following spectral characterizations were used: ...spectra of luminescence and its excitation, luminescence dependence on temperature, luminescence kinetics, optically stimulated luminescence and infrared absorption. It was found, that the BL is characteristic for all these materials, which were studied. The BL forms a wide, asymmetric and phonon-assisted emission band at 380nm. This luminescence can be excited either through the exciton processes, or with light from two defect-induced excitation bands at 340nm and 265nm. It was found that the BL is caused by two luminescence mechanisms. One of them is intra-center luminescence mechanism (340nm excitation), but the other one is recombination mechanism (265nm excitation). It was considered that the most probable candidates for the defects, which cause the BL in hBN can be related to the nitrogen vacancy type-centers. It was certainly confirmed, that presence of oxygen gas is partly quenching the BL intensity, thus ranking the hBN material among the materials prospective for development of oxygen gas optical sensors.
•Defect-induced luminescence at 380nm is observed for hBN powders.•A phonon-assisted structure is characteristic for 380nm luminescence.•The defect-related excitation of 380nm luminescence is at 340nm and 265nm.•The 380nm luminescence is caused by a recombination or an intra-center mechanism.•The 380nm luminescence is sensitive to oxygen gas environment.
We present a detailed analysis of week-long simultaneous observations of the blazar Mrk 421 at 2-60 keV X-rays (RXTE) and TeV -rays (Whipple and HEGRA) in 2001. Accompanying optical monitoring was ...performed with the Mt. Hopkins 48 inch telescope. The unprecedented quality of this data set enables us to establish the existence of the correlation between the TeV and X-ray luminosities, and also to start unveiling some of its characteristics, in particular its energy dependence and time variability. The source shows strong variations in both X-ray and -ray bands, which are highly correlated. No evidence of an X-ray/-ray interband lag tau is found on the full week data set, with tau image 3 ks. A detailed analysis of the March 19 flare, however, reveals that data are not consistent with the peak of the outburst in the 2-4 keV X-ray and TeV band being simultaneous. We estimate a image ks TeV lag. The amplitudes of the X-ray and -ray variations are also highly correlated, and the TeV luminosity increases more than linearly with respect to the X-ray one. The high degree of correlation lends further support to the standard model in which a unique electron population produces the X-rays by synchrotron radiation and the -ray component by inverse Compton scattering. However, the finding that for the individual best observed flares the -ray flux scales approximately quadratically with respect to the X-ray flux poses a serious challenge to emission models for TeV blazars, as it requires rather special conditions and/or fine tuning of the temporal evolution of the physical parameters of the emission region. We briefly discuss the astrophysical consequences of these new findings in the context of the competing models for the jet emission in blazars.
Laser-induced breakdown spectroscopy (LIBS) provides a rapid, cost-effective, and extra-sensitive analysis of geological samples to make preliminary conclusions about the presence of valuable ...elements up to the trace levels in the ore. We present the first results of a highly sensitive qualitative analysis of the core samples of geological ore from two boreholes in Latvia (Staicele 1, from a depth range of 794–802 m, and Garsene (Subate) 2A, from a depth range of 1102–1103 m) using LIBS. Our measurements using this technique confirmed the high iron content and indicated traces of rare and high in-demand metals (such as Ti, V, Co, Sm, etc.) in the sample from Staicele, renewing interest in studying boreholes across Latvia. The presented pilot studies demonstrated effectiveness and unique possibility in performing a very sensitive and time-saving qualitative analysis of the composition of samples of ores from the old but still valuable borehole cores by using the LIBS method. We compare these measurements with other methods of sample analysis.
Estrogen is a major factor in the development of breast cancer. In situ estrogen production by aromatase/estrogen synthetase in breast cancer plays a dominant role in tumor proliferation. Because ...natural compounds such as flavones and isoflavones have been shown to be inhibitors of aromatase, it is thought that vegetables that contain these phytochemicals can inhibit aromatase activity and suppress breast cancer cell proliferation. Heat-stable extracts were prepared from vegetables and screened for their ability to inhibit aromatase activity in a human placental microsome assay. The white button mushroom (species Agaricus bisporus) suppressed aromatase activity dose dependently. Enzyme kinetics demonstrated mixed inhibition, suggesting the presence of multiple inhibitors or more than one inhibitory mechanism. “In cell” aromatase activity and cell proliferation were measured using MCF-7aro, an aromatase-transfected breast cancer cell line. Phytochemicals in the mushroom aqueous extract inhibited aromatase activity and proliferation of MCF-7aro cells. These results suggest that diets high in mushrooms may modulate the aromatase activity and function in chemoprevention in postmenopausal women by reducing the in situ production of estrogen.
PDF
