We revisit laser intensity noise in the context of stimulated Raman scattering (SRS), which has recently proved to be a key technique to provide label free images of chemical bonds in biological and ...medical samples. Contrary to most microscopy techniques, which detect a weak photon flux resulting from light matter interactions, SRS is a pump-probe scheme that works in the high flux regime and happens as a weak modulation (10−4–10−6) in a strong laser field. As a result, laser noise is a key issue in SRS detection. This practical tutorial provides the experimentalists with the tools required to assess the amount of noise and the ultimate SRS detection limit in a conventional lock-in-based SRS system. We first define the quantities that are relevant when discussing intensity noise and illustrate them through a conventional model of light detection by a photodiode. SRS is then introduced in its lock-in-based implementation, and the model presented is adapted in this particular case. The power spectral density, relative intensity noise (RIN), signal to noise ratio, and sensitivity of the system are derived and discussed. Two complementary methods are presented that allow measurement of the RIN and assessment of the performance of a SRS system. Such measurements are illustrated on two commercial laser systems. Finally, the consequences of noise in SRS are discussed, and future developments are suggested. The presentation is made simple enough for undergraduate students, graduate students, and newcomers in the field of stimulated Raman and more generally in pump-probe based schemes.
It has been suggested that contextual factors may be related to obesity; however, they have not yet been widely investigated. The main objective of this ecological time-series study was to analyse ...factors associated with the increase in obesity in the adult and elderly population in Brazil from 2006 to 2020.
This is an ecological time-series study. Data were collected by the Surveillance System for Risk and Protection Factors for Chronic Diseases by Telephone Survey (VIGITEL), the main health survey in Brazil.
The outcome was the annual obesity growth rate (in percentage points). Independent variables were behavioural and contextual factors. Data analysis was performed using Prais-Winsten regression for temporal analyses, and Spearman correlation and crude and adjusted linear regression (beta and 95% confidence intervals CIs).
The annual obesity growth rate was 0.58 percentage points (p.p.) (95% CI: 0.54; 0.63) per year. Demographic density and the percentage of the population employed showed an inverse association with the growth of obesity. Variables such as Gross Domestic Product (GDP) per capita, Gini coefficient, urbanisation rate, percentage of the population with low level of education and percentage of the population without an income were directly associated with the increase in obesity rates. The variables maintained in the final model explained 81% of the growth in obesity in Brazil over the last 15 years (2006–2020).
The growth of obesity in Brazil was mostly explained by contextual factors, especially those of a socio-economic nature. Therefore, interventions to mitigate the increase in obesity must go beyond behavioural factors.
Dual-fluorescence pH probe for bio-labelling Richter, C; Schneider, C; Quick, M T ...
Physical chemistry chemical physics : PCCP,
2015-Nov-11, Letnik:
17, Številka:
45
Journal Article
Recenzirano
Odprti dostop
Although seminaphtorhodafluor (SNARF) dyes are already widely used to measure pH in cells and at biofilms, their synthesis has low yield and results in an unspecific position of a carboxy-group. The ...separation of 5'- and 6'-carboxy-SNARF reveals a pKa difference of 0.15, calling into question pH measurements with the (commercially available) mixture. Here we replace the bulky external dicarboxyphenyl ring with a propionate group and evaluate the spectral properties of the new derivative. Proceeding to the ethyl-iodoacetamide, covalent linkage to cysteine protein sites is achieved efficiently as shown with a cyanobacterial phytochrome, extending the scarce application of SNARF in bio-labelling in the current literature. Application in fluorescence lifetime imaging is demonstrated both with the lifetime-based and ratiometric-yield method.
In detached Bridgman growth, the crystal radius is less than the crucible radius and a meniscus bridges the gap between the crystal and crucible wall. Existence of detached growth depends upon the ...contact angle of the melt with the crucible wall, the growth angle of the solidifying crystal, the pressure differential across the meniscus, and the Bond number. The Young–Laplace capillary equation is used to calculate the crystal radii of detached states as a function of the pressure differential across the meniscus. Both terrestrial and microgravity conditions are considered. A variety of solution states is found, and multiple solutions with different crystal radii can exist for a given value of the pressure differential. The meniscus shapes for the detached states vary from simply convex or concave to shapes with numerous inflections. An approximate solution to the Young–Laplace equation for small Bond numbers is derived.
Schmerzsyndrome und Schlafstörungen verstärken sich gegenseitig: Schmerzen rauben den Schlaf, Schlafmangel wiederum erhöht die Schmerzempfindung. Wie Sie Schmerzpatienten aus diesem Teufelskreis ...befreien können, lesen Sie im folgenden Beitrag
Fluorescence correlation spectroscopy (FCS) is a single molecule based technique to temporally resolve rate-dependent processes by correlating the fluorescence fluctuations of individual molecules ...traversing through a confocal volume. In addition, chemical processes like protonation or intersystem crossing can be monitored in the sub-microsecond range. FCS thereby provides an excellent tool for investigations of protonation dynamics in proton pumps like cytochrome c oxidase (CcO). To achieve this, the pH-dependent fluorescent dye fluorescein was attached as a protonation probe to the CcO surface via site-specific labeling of single reactive cysteines that are located close to the entry point of a proton input channel (K-pathway). The analysis of protonation dynamics is complicated by overlapping triplet and protonation rates of the fluorophore. A Monte Carlo simulation based algorithm was developed to facilitate discrimination of these temporally overlapping processes thus allowing for improved protonation reaction rate determination. Using this simulation-guided approach we determined precise local proton association and dissociation rates and provide information about protein surface effects, such as proton collecting antennae, on the transport properties of proton transfer channels.
•NbC and (Zr0.4Nb0.4W0.2)C were consolidated by direct current sintering,•Samples were exposed to hydrogen flow for up to 3 h and 2500 K.•The mass loss rate for NbC in flowing hydrogen was about ...1 mg/m2.•Mass loss rates were compared between hydrogen and argon exposures.•Residual oxygen was preferentially removed upon hydrogen exposure.
Refractory carbides are promising materials for use in nuclear thermal propulsion, either as the primary material in nuclear fuel elements or as protective coatings. In particular, NbC and ZrC have high melting points, relatively low vapor pressures at elevated temperatures, and low thermal neutron cross sections. In this study, NbC and (Zr0.4Nb0.4W0.2)C were fully consolidated by direct current sintering, and relative densities of 98% were achieved. The samples were characterized by scanning electron microscopy and X-ray diffraction before and after hydrogen testing. The samples were exposed to hot flowing hydrogen gas at a pressure of 1 atm and a flow rate of 8 SLPM, at temperatures up to 2500 K, and for durations up to 3 h. The mass loss rate (MLR) of NbC decreased with increasing exposure, before reaching a steady state value of about 1 mg/m2s. For (ZrNbW)C, a comparison was made by exposing samples to either hot flowing hydrogen or argon gas. The mass loss rates decreased with increasing exposure to either gas, but the final steady-state MLR was one to two orders of magnitude greater for those samples exposed to hydrogen. As evidenced by X-ray data, small amounts of residual oxygen in the (ZrNbW)C samples were preferentially removed upon hydrogen exposure.
In Germany, hypericum extracts are among the most widely prescribed antidepressants. Additionally, many preparations of St. John's wort are sold on the free market and one extract is even the best ...selling antidepressant in the country. In contrast to synthetic antidepressants, the approval procedures are not so strict, which implies that the pharmaceutical industry is not forced to conduct clinical trials suitable for licensing. Nevertheless, numerous studies on hypericum extracts including depressed patients have been published in the last 20 years. The purpose of this paper is to review these investigations in respect of methodological considerations and to draw conclusions pertaining to the proof of antidepressant efficacy. To this effect, a computer-assisted literature research was performed and manufacturers were asked to supply the author with study results. A total of 12 placebo-controlled trials with hypericum extracts were performed, mostly with positive results. Also in comparison with synthetic antidepressants (3 studies published), a similar reduction of depressive symptomatology was seen, although the comparators were not adequately dosed. No trials in severely depressed patients have been published yet. Since most studies on hypericum have methodological flaws, further studies are warranted.
101 outpatients suffering from anxiety of non-psychotic origin (DSM-III-R criteria: agoraphobia, specific phobia, generalized anxiety disorder, and adjustment disorder with anxiety) were included in ...a 25-week multicenter randomized placebo-controlled double-blind trial with WS 1490, a special extract of kava-kava. In the main outcome criterion, the Hamilton Anxiety Scale (HAMA), there was a significant superiority of the test drug starting from week 8 on. WS 1490 was also found to be superior with respect to the secondary outcome variables. HAMA subscores somatic and psychic anxiety, Clinical Global Impression, Self-Report Symptom Inventory-90 Items revised, and Adjective Mood Scale. Adverse events were rare and distributed evenly in both groups. These results support WS 1490 as a treatment alternative to tricyclic antidepressants and benzodiazepines in anxiety disorders, with proven long-term efficacy and none of the tolerance problems associated with tricyclics and benzodiazepines.
Numerical calculations were performed to assess the effect of localized radial heating on the melt–crystal interface shape during vertical Bridgman growth. System parameters examined include the ...ampoule, melt and crystal thermal conductivities, the magnitude and width of localized heating, and the latent heat of crystallization. Concave interface shapes, typical of semiconductor systems, could be flattened or made convex with localized heating. Although localized heating caused shallower thermal gradients ahead of the interface, the magnitude of the localized heating required for convexity was less than that which resulted in a thermal inversion ahead of the interface. A convex interface shape was most readily achieved with ampoules of lower thermal conductivity. Increasing melt convection tended to flatten the interface, but the amount of radial heating required to achieve a convex interface was essentially independent of the convection intensity.
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