Search

The clumped isotope composition (Δ47, the anomaly of the mass 47 isotopologue relative to the abundance expected from a random isotope distribution) of CO2 has been suggested as an additional tracer for gross CO2 fluxes. However, the effect of photosynthetic gas exchange on Δ47 has not been directly determined and two indirect/conceptual studies reported contradicting results. In this study, we quantify the effect of photosynthetic gas exchange on Δ47 of CO2 using leaf cuvette experiments with one C4 and two C3 plants. The experimental results are supported by calculations with a leaf cuvette model. Our results demonstrate the important roles of the Δ47 value of CO2 entering the leaf, kinetic fractionation as CO2 diffuses into, and out of the leaf and CO2–H2O isotope exchange with leaf water. We experimentally confirm the previously suggested dependence of Δ47 of CO2 in the air surrounding a leaf on the stomatal conductance and back-diffusion flux. Gas exchange can enrich or deplete the Δ47 of CO2 depending on the Δ47 of CO2 entering the leaf and the fraction of CO2 exchanged with leaf water and diffused back to the atmosphere, but under typical ambient conditions, it will lead to a decrease in Δ47. [ABSTRACT FROM AUTHOR]

Optimizing upconversion (UC) composites is challenging as numerous effects influence their unique emission mechanism. Low scattering mediums increase the number of dopants excited, however, high scattering mediums increase the UC efficiency due to its non-linear power dependency. Scattering also leads to greater thermal effects and emission saturation at lower excitation power density (PD). In this work, a photoluminescence quantum yield (PLQY) increase of 270% was observed when hexagonal NaYF4:(18%)Yb3+,(2%)Er3+ phosphor is in air compared to a refractive index-matched medium. Furthermore, the primary inner-filter effect causes a 94% PLQY decrease when the excitation focal point is moved from the front of the phosphor to 8.4 mm deep. Increasing this effect limits the maximum excitation PD, reduces thermal effects, and leads to emission saturation at higher excitation PDs. Additionally, self-absorption decreases the PLQY as the phosphor's thickness increases from 1 to 9 mm. Finally, in comparison to a cuboid cuvette, a 27% PLQY increase occurs when characterizing the phosphor in a cylindrical cuvette due to a lensing effect of the curved glass, as supported by simulations. Overall, addressing the effects presented in this work is necessary to both maximize UC composite performance as well as report their PLQY more reliably. [ABSTRACT FROM AUTHOR]

Abstract Background The use of phase contrast in urinalysis has been highly recommended. A new system, sediMAX conTRUST PRO, is now available providing simultaneous automated phase contrast and bright field microscopy. This study aimed to evaluate both analytical and diagnostic performance of this new analyzer. Methods Results from 504 samples evaluated with the sediMAX conTRUST PRO were compared to those obtained from the same samples by manual microscopy (MM). Analytical and diagnostic performance were assessed according to established guidelines. Results The concentration of red blood cells (RBCs)and white blood cells (WBCs) at which the LoQ satisfied a CV< 25% was 12 particles per μL (p/μL) and 8 p/μL, respectively. Within one grade of agreement concordance was quite high, 97.8% for RBCs and 98.0% for WBCs, and above 90% for all other particles. Overall, diagnostic sensitivity and specificity were good (>80%) for the particles considered, although lower sensitivities, 70.6% and 61.8%, were respectively found for hyaline and pathological casts. Conclusions The sediMAX conTRUST PRO provides very good performance in terms of RBC and WBC recognition and enumeration, and quite good performance for all other particles. Hyaline cast and pathological cast identification is fine and comparable to other automated systems, but could use further improvement. Highlights • Best urine sediment evaluation is by phase contrast and bright field microscopy. • sediMAX conTRUST PRO provides good precision for quantitative particles. • High concordance of results between sediMAX conTRUST PRO and manual microscopy • Diagnostic sensitivity and specificity was >80% for all particles with the analyzer [ABSTRACT FROM AUTHOR]

Abstract It is proposed a new approach to evaluate the performance of ultraviolet photoreactions by integrating UV-LED and a UV–Vis cuvette as a mini-reactor for kinetic monitoring in a spectrophotometer not influenced by external light. This system uses only 3.0 mL of solutions in a rectangular quartz cuvette with a mini-bar magnetic stirrer in a cell holder and a UV-LED of 5 W with λ max at 370 nm was positioned on the top of the cuvette and maintained at 25.0 oC. The effectiveness of this photoreactor was demonstrated by measuring the real-time degradation of two model compounds, salicylic acid and methylene blue, in homogeneous and heterogenous systems. Photolysis of MB with H 2 O 2 results in increasing of rate constants as [H 2 O 2 ] increased. Heterogeneous photocatalysis of MB and SA was fastest achieved in ZnO dosage of 0,20 g.L–1. This mini-photoreactor allows monitoring the real-time kinetic performance collecting almost a thousand points in each experiment, leading to accurate rate constants. Moreover, this system presented positive environmental aspects such as: lower reactants and catalyst amounts, lower cost and waste amounts, use of the UV-LED radiation and labor time saving. This is a novel approach to determine the photoreaction effectiveness and it can be applied to systematic studies especially for the kinetic parameter determinations. Graphical Abstract Unlabelled Image Highlights • This mini-photoreactor system allows monitoring photoreactions in real time. • Homogeneous photolysis of MB was monitored in presence of H 2 O 2. • Heterogeneous photocatalytic degradation of both SA and MB was faster with ZnO at 0.20 g.L−1. • Photodegradation of MB and SA was described by a first order kinetic model. • Kinetic data of photochemical reactions were obtained with practicality, accuracy, and safety. [ABSTRACT FROM AUTHOR]

The paper presents experimental results of the interaction of a focused optical beam with a suspension of CdSe/ZnS quantum dots in toluene. Two autographs characteristic only of the behavior of a superfluid quantum liquid were experimentally observed. The first was the fountain effect from the region of local heating of the suspension with an optical beam; the second was the complete "creeping out" of the QDs suspension in the form of a thin film along the walls of the cuvette in which the suspension was located. The results of the work suggest that superfluid quantum liquid may arise at room temperature as a result of the functioning of many-particle quantum superposition. Bose-Einstein condensation of entangled quantum states is proposed as a physical mechanism for producing a superfluid liquid, regardless of temperature. [ABSTRACT FROM AUTHOR]

A Fourier transform infrared (FTIR) spectroscopy with infrared quartz cuvette (IQC) as spectral accessory method was developed to determine acid value (AV) of edible oils. The absorption peak at 5680 cm-1/5487 cm-1 ascribed to the C-H stretching band was a substitute for the peak of an internal standard. Partial least square (PLS) regression was used for AV calibration, and samples were validated by titrated method. Results showed dilution calibration was feasible for randomly dilution among 6-13:1 (CCl4: oils, v/ v). PLS calibration was optimal by a spectral wavenumber (3603 cm-1-3250 cm-1) as the first derivative treatment. Correlation coefficient and root mean square error of calibration were 0.9967 and 0.135, respectively. Calibrated validation, blind sample validation and precision analysis presented a good correlation between IQC-FTIR and titrated methods. Based on the dilution calibration, randomly diluted oil samples can be employed by IQC-FTIR. [ABSTRACT FROM AUTHOR]

Abstract Rapid Prototyping technologies expand the availability of fabrication of plastic objects to non-skilled users that need sophisticated equipment for their research. In this communication, for the very first time, the universal design of photometric-fluorometric, UV–Vis compatible, 3D-printed flow-through cuvette with two optical paths (2 and 10 mm) is introduced. The cuvette insert was made with the use of the most economically viable Fused Material Deposition technology which enables truly one-step manufacturing and easy replicating of the device. A utility of the cuvette was presented in the example of the basic flow injection analysis experiments on the model photometric (bromothymol blue) and fluorometric (fluorescein) dyes and proven by investigation of solubility constant of calcium hydrophosphate dihydrate by determination of phosphate using fluorescence quenching of molybdenum blue-Rhodamine B ion pair formation and calcium reaction with calcein in basic environment. Graphical abstract fx1 Highlights • Ordinary, disposable cuvette can be quickly turned in to reliable flow vessel. • The 3D printed flow cuvette enables use in spectrophoto- and fluorometric detection. • High spectral transparency of the used cuvette allows detection in UV–Vis range. • The presented design can be used as disposable due to its negligible cost. [ABSTRACT FROM AUTHOR]

A spectrophotometer that uses a localized surface plasmon resonance phenomenon is a powerful measurement tool in the biotechnology and bioanalysis fields. We propose a novel cuvette design type that can be used for universal spectrophotometers. The novel cuvette design needs a few μl reagent for measuring, and also two chips for measurement can be loaded and measured at the same time. A new cuvette can easily be used several times because of sample chips to be loaded and unloaded since they are mechanically mounted by screws. Therefore, it can offer advantages to users in terms of cost and time. We verify its possibility for use in the biotechnology and bioanalysis fields by a signal enhancement and dual signal detection. [ABSTRACT FROM AUTHOR]

Abstract Both coherent Third Harmonic Generation (THG) at the interfaces of a cuvette filled with a nanocrystal suspension and incoherent Second and Third Harmonic Scattering (THS) from the suspension volume have been studied to quantitatively assess the orientation-averaged third-order susceptibility 〈 χ N P s (3) 〉 of ZnO. These two complementary experimental approaches are based on different calibration routes with a nanocomposite model and fused-silica as a reference material for THG, and pNa molecules for THS. Similar and consistent absolute values of 〈 χ N P s (3) 〉 (above 10 − 18 m2/V2) are derived and discussed according to the particular orientation averaging procedure that holds for each experimental configuration for a 1064 nm excitation wavelength. Highlights • Coherent THG and incoherent THS from ZnO nanocrystal suspensions. • Averaged third-order susceptibility derived at 1064 nm for each experimental configuration. • Orientation averaging procedure, experimental benefits/caveats and calibration routes detailed. [ABSTRACT FROM AUTHOR]

The fluorescence technique is very popular and has been used in many fields of research. It is simple in its assumptions but not very easy to use. One of the main problems is the inner filter effect (IF) I and II which takes place in the cuvette. IF type I is permanently present, but IF type II occurs only when absorption and fluorescence spectra overlap. To avoid IF type I, absorbencies in the cuvette should be smaller than 0.05, which is however very difficult to obtain in many experiments. In this work we propose a new method to solve these problems in the case of a Cary Eclipse fluorimeter, having horizontally-oriented slits, based on old equations developed in the middle of the last century. This method can be applied for other instruments, even these with vertically-oriented beams, because we share scripts written in MATLAB and GRAMS/AI environment. Calculations in our method enable specifying beam geometry parameters in the cuvette, which is necessary to obtain the correct shape and fluorescence intensity of emission and excitation spectra. Such a specific fluorescence intensity dependence on absorbance can, in many cases, afford possibilities to determine the quantum yield (QY) using slopes of the straight-lines, which was demonstrated with the use of Tryptophan (Trp), Tyrosine (Tyr), and Rhodamine B (RhB) solutions. For example, assuming that QY = 0.14 for Tyr, the QY determined for RhB reached QY = 0.71 ± 0.05, although the measurement for Tyr and RhB was performed at a completely different spectral range. [ABSTRACT FROM AUTHOR]

Polydopamine decorated in-situ with Localized Surface Plasmon Resonance (LSPR)-active gold nanoparticles (AuNPs) may extend the applicability of nanoplasmonic materials to original and innovative applications in several fields. Here we report the modification of disposable UV–Vis polystyrene cuvettes with AuNPs@PDA for refractive index LSPR-based measurements. An original layer-by-layer deposition method of PDA followed by AuNPs growth is here developed, showing linear correlation between PDA thickness and optical properties. In particular, the modulation from wavelength sensitivity toward absorbance sensitivity is obtained, allowing measurements at fixed wavelength (578 nm). As applicative example of the photonic cuvettes, the measurement of fermentable sugars in beer wort is here reported. The analytical performance of our approach has been directly compared to portable refractometer of reference, displaying excellent results in terms of the precise estimation of sugars in beer wort (expressed in degrees Brix), reproducibility and sensitivity. The approach may be extended to other materials of interest in LSPR based optical sensors, e.g . optical fibers. [ABSTRACT FROM AUTHOR]

Background For the determination of total bilirubin in serum the candidate reference method developed by Doumas et al. has international recognition. The primary standard SRM 916a (NIST) was recommended for use as the primary reference material for calibration. Nowadays, no primary standard is anymore commercially available. Further, a description of uncertainty components was missing. Methods Two reference laboratories have re-investigated the candidate reference measurement procedure. Beside minor modifications, mainly the use of a molar absorption coefficient instead of calibration by use of bilirubin standard solutions has facilitated the operating, and improved the analytical performance. All relevant sources of measurement uncertainty were investigated. Results A measurement range of 5–525 μmol/L and a CV of 0.5% to 1.4% (long term imprecision) were determined. Excellent agreement was obtained comparing to Doumas procedure ( r  = 0.9999) and during a two laboratory comparison participating at IFCC RELA ring trials (mean deviation: 0.6%). The combined expanded measurement uncertainty (probability 95%) for bilirubin concentrations >30 μmol/L was estimated as 2.2%. Conclusion A reference system for total bilirubin based on the described reference procedure shall enable metrological traceability and optimized standardization of the values obtained in clinical routine laboratories. [ABSTRACT FROM AUTHOR]

The paper presents results of experimental research into the transmission of infrared radiation through water film. Experiments substantiate a hypothesis about the considerable role of radiative heat transfer when heating heterogeneous water drops containing opaque solid particles in high-temperature gases. We measure the temperatures of water film surface, the bottom of a cylindrical plastic cuvette and a graphite substrate. During the experiments, the typical thickness of the water film, the bottom of the plastic cuvette and the graphite substrate is 1 mm. The temperature measurements are implemented for carbonated, distilled and tap water. Results of a comparative analysis of these measurements are presented as well. The hypothesis is formulated about a significant variation in the optical properties of water under temperature fluctuations. This assumption is based on the hydrophobic properties of amphiphilic molecules. Importantly, the experimental data enable the study of rapid evaporation of a liquid at internal and external interfaces of water drops containing solid opaque particles with a further explosive fragmentation of water film. This mechanism relies on heating of the particle surface above the boiling point of water. [ABSTRACT FROM AUTHOR]

We explore methods for utilizing electrochemical redox contacts both at the front and back of illuminated semiconductors. A dual cuvette cell utilizes a cuvette/gasket/semiconductor/gasket/cuvette sandwich with rapid stirring and the capability for fourelectrode measurements. Results from the dual-cuvette cell include current density--potential (J-E) scans with a cobaltocene+/0 back contact to n--Si(111) and a ferrocene+/0 front contact facing the illumination source, and a logarithmic plot of short-circuit current density vs open-circuit photovoltage for several illumination intensities to quantify the diode ideality factor for this cell. An ITO/liquid/semiconductor/liquid/ITO sandwich in a two-electrode configuration comprises a thin-layer cell. Thin-layer cell results include J--E scans as well as electrochemical impedance/Mott-Schottky analysis of flatband potentials. Results on n--Si(111) electrodes with two liquid junction contacts resemble results from traditional photoelectrochemical cells with a rectifying liquidjunction front contact and a rear metal contact. [ABSTRACT FROM AUTHOR]

Semiconducting quantum dots (QDs) are finding a wide range of biomedical applications due to their intense fluorescence brightness and long-term photostability. Here, we report precise quantification of the fluorescence intensity of single QDs on a laboratory-built high-sensitivity flow cytometer (HSFCM). The nearly uniform illumination of the particles at the intense portions of the radiation field resulted in narrowly distributed signals with high signal-to-noise ratios. By analysis of thousands of QDs individually in as little time as 1 min, intrinsic polydispersity was quickly revealed in a statistically robust manner. Applications of this technique in QD quality assessment, study of metal ion influence, and evaluation of aggregation upon biomolecule coupling are presented. Moreover, an accurate measurement of the QD particle concentration was achieved via single-particle enumeration. HSFCM is believed to provide a powerful characterization tool for QD synthesis and application development. [ABSTRACT FROM AUTHOR]

For the design of bioconversion processes parallel experimentation in microtiter plates is commonly applied to reduce the experimental load, although data accuracy and reproducibility are often reduced. In an effort to quantify the impact of different microscale experimental systems on the estimation of enzyme kinetic parameters from progress curves, we comprehensively evaluated the enzymatic reduction of acetophenone in both open and closed polystyrene and quartz microtiter plates as well as quartz cuvettes. Differences in conversion of up to 50% over time were observed increasing from polystyrene MTPs to quartz MTPs to quartz cuvettes. Initial reaction velocities increased systematically from polystyrene to quartz MTPs and cuvettes. The experimental errors decreased in the same order showing highest experimental error of about 20% in polystyrene. We further evaluated reasons causing the deviations within one system as well as between the systems. The choice of reaction vessel material, temperature effects and substrate cross contaminations in MTPs were shown to be of importance in the experimental results. Although the experimental data differed between the reaction vessels, no distinct trends in estimated kinetic parameters were found. While the microkinetic parameters vary up to an order of magnitude between different systems, the corresponding macrokinetic parameters lie in the same range for all systems varying by 29-118%. © 2016 American Institute of Chemical Engineers Biotechnol. Prog., 33:87-95, 2017 [ABSTRACT FROM AUTHOR]

It is often challenging to follow fast surface adsorption processes with sufficient time resolution. Here we report a convenient UV–Vis spectrophotometry based method to study the fast kinetics of an archetypical surface process: the adsorption of MB on quartz. The test object was a commercial quartz cuvette. About 3.3% of the dye was adsorbed from a 34 μM solution at pH 7 in 10 min. Biphasic kinetics was observed for the depletion of MB under continuous stirring at 1000 rpm. A kinetic model was postulated for the interpretation of time resolved spectral changes. This model assumes the reversible adsorption of MB on the surface which is followed by the isomerization of the binding mode. The overall process is kinetically first order with respect to MB, thus dimer formation, which was previously proposed to be favored on quartz, can be ruled out. The experimental adsorption isotherm is consistent with the formation of an adsorption monolayer from single molecules. The UV–vis absorbance spectrum of adsorbed MB does not show any blue shift. With the simplest experimental setup, it is shown that the dimerization of MB is not exceptionally favored on quartz surface. [ABSTRACT FROM AUTHOR]

Random lasing in dye-doped nematic liquid crystals (NLCs) contained in a quartz cuvette was studied. With the pumping energy rising, random lasing with nonresonant feedback and resonant feedback emerge successively with the lasing threshold of 20 and 40 μJ, respectively. The lasing properties including fluctuation of the emission spectrum, divergence angle of emission, independence of the emission on the polarisation of the pump beam and the depolarisation of emission are distinct from those of dye-doped nematics confined in the sandwich structure cell or the capillary tube. The distinctions are associated with the thermal fluctuation of dielectric tensor since there is negligible surface anchoring for the nematics in the pump volume. This indicates that the anchoring state of NLCs is an important factor determining the random lasing properties. [ABSTRACT FROM AUTHOR]

Microscopy is the reference method for intestinal parasite identification. The cuvette-based automated microscopy analyser, sediMAX 1, provides 15 digital images of each sediment sample. In this study, we have evaluated this fully automated instrument for detection of enteric parasites, helminths and protozoa. A total of 700 consecutively preserved samples consisting of 60 positive samples (50 protozoa, ten helminths) and 640 negative samples were analysed. Operators were blinded to each others' results. Samples were randomized and were tested both by manual microscopy and sediMAX 1 for parasite recognition. The sediMAX 1 analysis was conducted using a dilution of faecal samples, allowing determination of morphology. The data obtained using sediMAX 1 showed a specificity of 100% and a sensitivity of 100%. Some species of helminths, such as Enterobius vermicularis , Strongyloides stercolaris , the Ancylostoma duodenale / Necator americanus complex, and schistosomes were not considered in this work, because they are rare in stool specimens, are not easily detectable with microscopy analysis, and require specific recovery techniques. This study demonstrated for the first time that sediMAX 1 can be an aid in enteric parasite identification. [ABSTRACT FROM AUTHOR]

Initial steps to apply a ceramic multi-layer technique to build a new sensor for a Tian-Calvet calorimeter are presented in this contribution. The new sensor has a stacked design of ceramic sensor discs and insulating rings. The development was finite-element method (FEM) supported to design the sensor disc. In the next step, the function of the sensor disc was proven up to a temperature of 600 °C. Finally, the entire stack was tested at room temperature, delivering a resolution of 5μW and a maximum sensitivity of 8.5 μV mW-1. The time constant is strongly dependent on the mass of the cuvette. We show that the time constant of the sensor can be more exactly characterized when using a novel low temperature co-fired ceramic (LTCC) cuvette with a low mass and an integrated heater. Then, the time constant can be reduced to T1/e = 118 s. The new sensor shows similar specifications as commercial devices and presents a good starting point for future high temperature applications. [ABSTRACT FROM AUTHOR]

A non-dispersive infrared (NDIR) sensor system has been designed to monitor the state of contamination and degradation of aviation hydraulic fluids. Core part of this system is a MOEMS subsystem consisting of a micro cuvette, a MEMS thermal IR emitter and a four-channel thermopile array. For ruggedness, this MOEMS subsystem is integrated into a high-pressure resistant metal package. The MOEMS subsystem measures the transparency of the fluid under test at four specifically chosen spectral channels. Three of these channels allow the water content, the total acidity number and the remaining acid scavenger reserve to be monitored. The forth channel serves for calibration and self-test purposes. Fluid monitoring systems of this kind will form key components in an innovative AIRBUS aircraft maintenance system. [ABSTRACT FROM AUTHOR]

We show in our work that very narrow (FSR ~0.09 nm) lasing modes can be formed from Rhodamine 6G solution confined within quartz (SiO 2 ) cuvette with suitable pumping scheme by Q switched Nd:YAG laser. With introduction of silver nanoparticles of different concentrations in Rhodamine 6G we show that such lasing modes can be modulated as well as tuned in intensity, band spacing and emission wavelength. We also show that this system maintains a very high Q value >6.4*10 3 irrespective to change in other parameters. [ABSTRACT FROM AUTHOR]

We present a dynamic twin-cuvette system for quantifying the trace gas exchange fluxes between plants and the atmosphere under controlled temperature, light and humidity conditions. Compared with a single cuvette system, the twin-cuvette system is insensitive for disturbing background effects such as wall deposition. In combination with a climate chamber we can perform flux measurements under constant and controllable environmental conditions. With an Automatic Temperature Regulated Air Humidification System (ATRAHS) we are able to regulate the relative humidity inside both cuvettes between 40 to 90% with a high precision of 0.3%. Thus, we could demonstrate that for a cuvette system operated with a high flow rate (> 20 L min-1) such a temperature regulated humidification system as ATRAHS is an accurate method for air humidification of the flushing air. Furthermore, the fully automatic progressive fill-up of ATRAHS based on a floating valve improved the performance of the entire measurement system and prevented data gaps. Two reactive gas species, ozone (O3) and peroxyacetyl nitrate (PAN), were used to demonstrate the quality and performance of the twin-cuvette system. O3 and PAN exchange with Quercus ilex was investigated over a 14 day measurement period under controlled climate chamber conditions. By using O3 mixing ratios between 32-105ppb and PAN mixing ratios between 100-350 ppt a linear dependency of the O3 flux as well as the PAN flux in relation to its ambient mixing ratio could be observed. At relative humidity (RH) of 40 %, the deposition velocity ratio of O3 and PAN was determined to be 0.45. At that humidity, the deposition of O3 to the plant leaves was found to be only controlled by the leaf stomata. For PAN an additional resistance inhibited the uptake of PAN by the leaves. Furthermore, the formation of water films on the leaf surface of plants inside the chamber could be continuously tracked with our custom built leaf wetness sensors. Using this modified leaf wetness sensor measuring the electrical surface conductance on the leaves, an exponential relationship between the ambient humidity and the electrical surface conductance could be determined. [ABSTRACT FROM AUTHOR]

Leaks and isotopic disequilibria represent potential errors and artefacts during combined measurements of gas exchange and carbon isotope discrimination (Δ). This paper presents new protocols to quantify, minimize, and correct such phenomena. We performed experiments with gradients of CO2 concentration (up to ±250 μmol mol−1) and δ13CCO2 (34‰), between a clamp-on leaf cuvette ( LI-6400) and surrounding air, to assess (1) leak coefficients for CO2, 12CO2, and 13CO2 with the empty cuvette and with intact leaves of H olcus lanatus ( C3) or S orghum bicolor ( C4) in the cuvette; and (2) isotopic disequilibria between net photosynthesis and dark respiration in light. Leak coefficients were virtually identical for 12CO2 and 13CO2, but ∼8 times higher with leaves in the cuvette. Leaks generated errors on Δ up to 6‰ for H . lanatus and 2‰ for S . bicolor in full light; isotopic disequilibria produced similar variation of Δ. Leak errors in Δ in darkness were much larger due to small biological : leak flux ratios. Leak artefacts were fully corrected with leak coefficients determined on the same leaves as Δ measurements. Analysis of isotopic disequilibria enabled partitioning of net photosynthesis and dark respiration, and indicated inhibitions of dark respiration in full light ( H . lanatus: 14%, S . bicolor: 58%). [ABSTRACT FROM AUTHOR]

We discuss the details of ambipolar relaxation of the electric field in liquid asymmetric electrolytes to its stationary value. It is demonstrated that the account for finite boundary conditions modifies the existing concepts of this diffusion process. In particular, we succeeded to suggest a qualitatively correct explanation of the observed distribution of the electric fields over the bulk of the cuvette and its nonmonotonic behavior in measurements on the finite-size cuvette. We analyze the conditions of such an anomaly at the intermediate stages of the relaxation process. [ABSTRACT FROM AUTHOR]

A new method for zinc pre-concentration/separation and determination by molecular fluorescence is proposed. The metal was complexed with o-phenanthroline and eosin at pH 7.5 in Tris; a piece of filter paper was used as a solid support and solid fluorescent emission measured using a conventional quartz cuvette. Under optimal conditions, the limits of detection and quantification were 0.36 × 10 −3 and 1.29 × 10 −3 μg L −1 , respectively, and the linear range from 1.29 × 10 −3 to 4.50 μg L −1 . This method showed good sensitivity and selectivity, and it was applied to the determination of zinc in foods and tap water. The absence of filtration reduced the consumption of water and electricity. Additionally, the use of common filter papers makes it a simpler and more rapid alternative to conventional methods, with sensitivity and accuracy similar to atomic spectroscopies using a typical laboratory instrument. [ABSTRACT FROM AUTHOR]

Background Free light chains (FLC) are useful biomarkers for diagnosis and follow-up of plasma cell disorders. FLC quantification is encumbered by non-linearity and antigen excess (> 4-fold difference between results obtained at the 2000- and 100-fold dilution). Methods FLC concentration was measured with Freelite® reagents on the BNII, using 100- and 2000-fold dilutions in 3645 samples. Samples displaying antigen excess were re-measured at the 2000- and/or 400-fold dilution. Carryover was evaluated by tracing samples to cuvettes and by measuring a normal sample in cuvettes that previously contained samples with a high FLC concentration. Results Antigen excess occurred in 0.93% of samples for κ and in 0.55% of samples for λ . In 81.5% of the cases, it could not be confirmed by a re-analysis of a 2000-fold and/or a 400-fold diluted sample. Real antigen excess was documented in 0.25% and 0.03% of the samples for κ and λ FLC, respectively. In the low concentration range (2000-fold dilution), imprecision was high. False antigen excess was reduced by batch analysis, introducing cleaning and rinsing procedures and using the 400-fold dilution. No antigen excess was detected in samples with normal FLC concentrations. Conclusion Falsely high results occur by imprecision in the low concentration range and/or by carryover in cuvettes. [ABSTRACT FROM AUTHOR]

An exchange system is presented, which allows ultrafast experiments with high excitation rates (1 kHz) on samples with reaction cycles in the range of a few seconds and small sample volumes of about 0.3 ml. The exchange is accomplished using a commercially available cuvette by the combination of a special type of magnetic stirring with transverse translational motion of the sample cuvette. [ABSTRACT FROM AUTHOR]

Highlights: [•] Cavity ring-down method was used for sensitive optical sensor readout. [•] Plasmonic nanoparticles immobilized within a microfluidic cuvette act as sensors. [•] Physical effect: plasmonic resonance shift of metallic nanoparticles in dependence on changes in refraction index. [•] Enables in situ sensitive optical readout in real-time. [•] DNA-sensing demonstrated as proof-of-principle. [Copyright &y& Elsevier]

The first near-infrared fluorescent turn-on sensor for the detection of nitroxyl (HNO), the one-electron reduced form of nitric oxide (NO), is reported. The new copper-based probe, CuDHX1, contains a dihydroxanthene (DHX) fluorophore and a cyclam derivative as a Cu(II) binding site. Upon reaction with HNO, CuDHX1 displays a five-fold fluorescence turn-on in cuvettes and is selective for HNO over thiols and reactive nitrogen and oxygen species. CuDHX1 can detect exogenously applied HNO in live mammalian cells and in conjunction with the zinc-specific, green-fluorescent sensor ZP1 can perform multicolor/multianalyte microscopic imaging. These studies reveal that HNO treatment elicits an increase in the concentration of intracellular mobile zinc. [ABSTRACT FROM AUTHOR]

This paper presents a new air-bubble free microfluidic blood cuvette for the measurement of hemoglobin concentration. The microfluidic blood cuvette was filled with blood samples by capillary force, and hemoglobin levels in the blood were determined by measuring absorbance at the wavelength of 530 nm. Two different microfluidic blood cuvettes with dual and single sidewall microchannels were investigated. The microfluidic blood cuvette was fabricated using a polymethyl methacrylate substrate and a dry film photoresist. During the blood-filling process, air was trapped in the dual-sided wall-type cuvettes, while no air trapping occurred in the single sidewall-type cuvettes. The sensitivity of the hemoglobin measurements was more linear in a 105 μm deep microchannel than in a 35 μm deep microchannel. [ABSTRACT FROM AUTHOR]

Background: Despite striking similarities among colorimetric lipase assay recipes, marked intervendor differences are noted in the reported lipase values. In the present study, the effect of physical properties of the cuvette surface on measurement of serum lipase was investigated. Methods: Lipase activity was measured concomitantly in cuvettes from three different analyzers: Vista (Siemens), Modular (Roche), and Synchron (Beckman Coulter). The surface/volume ratio of the cuvettes and the contact angle of the cuvette polymers were determined. The effects of various characteristics of serum (biochemical parameters, surface tension) were also examined. Results: Serum lipase activities based on the colorimetric methylresorufin assay differed markedly according to the cuvettes used. More specifically, in the lower activity rate, marked differences were reported. The physical properties of the various cuvettes showed remarkable differences, especially in the contact angles. Other biochemical parameters (bilirubin, alkaline phosphatase, total cholesterol, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, and triglycerides) and serum surface tension did not affect the results. Conclusions: Serum lipase activity is affected by the physical properties of the cuvette surface. [ABSTRACT FROM AUTHOR]

Procedures for the determination of photoluminescence quantum yields with optical methods are addressed, and challenges associated with these measurements are discussed. Special emphasis is dedicated to relative measurements of fluorescent (i.e., short excitedstate lifetime), transparent, dilute dye solutions in conventional cuvettes in a 0°/90° measurement geometry. Recommendations on the selection of suitable quantum yield standards are presented, and requirements for the documentation of photoluminescence quantum yields are derived. [ABSTRACT FROM AUTHOR]

Abstract: Details are provided of a spectroelectrochemical cell that consists of a UV/vis cuvette. We report the UV/vis spectroelectrochemical measurements of cytochrome c, myoglobin, horseradish peroxidase, and cytochrome bc 1 at pH7.0. The application on cytochrome c was performed by direct electron exchange between the protein and the working electrode. On the other hand, the measurements on myoglobin, horseradish peroxidase, and cytochrome bc 1 were carried out in the presence of redox mediators. All the proteins display one-electron redox changes, as expected and measured midpoint potentials (E m) that agree with previously reported values. [Copyright &y& Elsevier]

Abstract: This paper explores the evolution of land use and natural resource management strategies over the past twenty to fifty years in a remote Sahelian region. The empirical example is Karagou village in SE Niger. Building on an in-depth survey from 1992 and a targeted, follow-up analysis of contemporary land use strategies in 2011, the change process is scrutinized. The analysis uses the conceptual lenses of land systems science, human–environmental timelines, and the notion of multiple exposures. Enabling and constraining conditions for local livelihoods in terms of the resource base (landscape, water, and population) are described. Results characterize how land use strategies have developed and how local people opportunistically use different landscape elements such as dune landscapes, valley bottoms (bas-fonds) and oases (cuvettes). Major concerns are rainfall variability, saturation of cropland, and perceived dwindling groundwater resources. It is concluded that the land use and livelihood strategies have remained remarkably stable in the face of the changing socio-ecological fringe conditions, but that this situation may hamper a sustainable transformation. [Copyright &y& Elsevier]

There is an ongoing debate on how to correct leaf gas exchange measurements for the unavoidable diffusion leakage that occurs when measurements are done in non-ambient CO2 concentrations. In this study, we present a theory on how the CO2 diffusion gradient over the gasket is affected by leaf-mediated pores ( LMP) and how LMP reduce diffusive exchange across the gaskets. Recent discussions have so far neglected the processes in the quasi-laminar boundary layer around the gasket. Counter intuitively, LMP reduce the leakage through gaskets, which can be explained by assuming that the boundary layer at the exterior of the cuvette is enriched with air from the inside of the cuvette. The effect can thus be reduced by reducing the boundary layer thickness. The theory clarifies conflicting results from earlier studies. We developed leaf adaptor frames that eliminate LMP during measurements on delicate plant material such as grass leaves with circular cross section, and the effectiveness is shown with respiration measurements on a harp of Deschampsia flexuosa leaves. We conclude that the best solution for measurements with portable photosynthesis systems is to avoid LMP rather than trying to correct for the effects. [ABSTRACT FROM AUTHOR]

We describe a novel method to detect very low concentrations of bacteria in water. Our device consists of a portable horizontal geometry small confocal microscope with large pinhole and a holder for cylindrical cuvettes containing the sample. Two motors provide fast rotational and slow vertical motion of the cuvette so the device looks like a simplified flow cytometer without flow. To achieve high sensitivity, the design has two detection channels. Bacteria are stained by two different nucleic acid dyes and excited with two different lasers. Data are analyzed with a correlation filter based on particle passage pattern recognition. The passage of a particle through the illumination volume is compared with a Gaussian pattern in both channels. The width of the Gaussian correlates with the time of passage of the particle so one particle is counted when the algorithm finds a match with a Gaussian in both channels. The concentration of particles in the sample is deduced from the total number of coincident hits and the total volume scanned. This portable setup provides higher sensitivity, low-cost advantage, and it can have a wide use ranging from clinical applications to pollution monitors and water and air quality control. [ABSTRACT FROM AUTHOR]

A new approach to simple solid sample digestion, subsequent vaporization, and introduction into an inductively coupled plasma was developed for the direct determination of chlorine in fine ceramic materials by atomic emission spectrometry. To each small sample cuvette made of tungsten, a powder sample was placed and weighed accurately. Following an addition of modifier solution, the cuvette was positioned on the tungsten boat furnace incorporated an electrothermal vaporizer. Then, the analyte in the sample cuvette was vaporized and introduced into the plasma; the major components of ceramic being retained. The solid ceramic samples were analyzed by using an external calibration curve prepared with the aqueous standard solutions. The detection limit of chlorine was estimated to be 0.71 ng, which corresponds to 59 ng g−1of the chlorine concentration in solid ceramic materials. The relative standard deviation was calculated to be 3.2%. The analytical results in various ceramic materials are described. [ABSTRACT FROM AUTHOR]

The key points of test condition for CD have been studied in this article, such as absorption of light, concentration, salt and buffer selection, cuvette selection, dynode voltage, baseline correction etc. These key steps are the basis for the accuracy and reliability of the test. [ABSTRACT FROM AUTHOR]

An inexpensive photoreactor using LED light sources and a fibre-optic CCD spectrophotometer as a detector was built by designing a special cell holder for standard 1.000 cm cuvettes. The use of this device was demonstrated by studying the aqueous photochemical reaction of 2,5-dichloro-1,4-benzoquinone. The developed method combines the highly quantitative data collection of CCD spectrophotometers with the possibility of illuminating the sample independently of the detecting light beam, which is a substantial improvement of the method using diode array spectrophotometers as photoreactors. [ABSTRACT FROM AUTHOR]

Abstract: In the present research we discuss a novel way to set up a predictive method for determining the water content of oil based on the Partial Least Squares (PLS) regression analysis of reflectometric signals. Ten different extra virgin olive oils with a water content ranging from 714 to 2008mg of water/kg of oil were submitted to reflectometric measurement by means of a hand made probe connected to a digital sample oscilloscope with TDR functions interfaced with a PC. Limits of the classical approach based on the TDR electromagnetic theory in the prediction of these small water content differences were also discussed. The results show that the suggested novel approach is able to predict the water content of very small quantities of oil (1.8g) in a 3ml translucent disposable PE cuvette by means of PLS regressions characterized by R 2 value up to 0.984 and a root mean square error of prediction of about 55mg of water/kg of oil. The temporal region showing the best information content corresponded with the rise of the reflection of the probe end, but information highly correlated with the water content can be extracted from other temporal regions of the entire TDR signal. [Copyright &y& Elsevier]

In this communication we present an approach for reconstruction of suspension absorption spectra of microalgae as measured in standard 1-cm spectrophotometric cuvettes from reciprocal reflectance, R(λ)-1, spectra of cells deposited on glass-fiber filters. Reciprocal reflectance exhibited the highest dynamic range (eight times wider in comparison with the functions -log(T) and -log(R)) and showed almost linear relationships with suspension absorbance and chlorophyll content from 0.7 to 9.9 μg/ml. The relationships between suspension absorbance and the -log(T) and log[(1-R)/T] functions were non-linear and were fitted by second-order polynomials with high contribution of the quadratic term. The use of R(λ)-1 allowed the reconstruction of suspension absorbance of six species from key groups of planktonic microalgae in the range from 0.001 to 0.250, with RMSE < 0.02. The advantages of the suggested approach over traditional techniques employing -logT(λ) of the filters are discussed, including the suitability for plankton studies in the field and for the monitoring of cultivated microalgae. [ABSTRACT FROM AUTHOR]

A modernized device intended for diagnosing the temperature-dependent activity of cells is described. The activity of cells was determined by finding the correlation coefficient of optical signals in speckle patterns recorded at different moments of time. It is shown that, as the temperature increases from 26 to 36°C, variations in the optical paths in cells increase from 16 to 26 nm. This is probably associated with the physiological activity of cells-trapping of large molecules or their conglomerates. In contrast to the previous variant of the device design, instead of a lipid membrane, a cell monolayer was used, which was cultivated on a plane-parallel glass plate. In order to reduce variations in the optical path lengths in a nutrient solution, a 1.7-mm-thick plane-parallel glass plate was additionally inserted into the cuvette. The modernization of the device also includes heating of the cuvette with hot air flows. [ABSTRACT FROM AUTHOR]

Abstract: Dynamic rheology, UV/VIS spectrometry with temperature programming cuvette and reaction calorimetry were conducted on cellulose pulp/FeTNa (NaOH solution containing ferric tartaric acid complex) solutions to investigate their thermostability and spinnability. Color of cellulose/FeTNa solutions changed above 90°C due to the decomposition of the complex. Thermal activity of cellulose/FeTNa solution started above 130°C induced by water vapor evolution and complex decomposition. Regeneration of cellulose/FeTNa solutions in a non-solvent (acetic acid and Na-gluconate mixture) resulted in transition from cellulose I into cellulose II structure as revealed by WAXS measurements. Wet-spinning attempts of cellulose/FeTNa solutions yielded fiber-like shaped bodies with a brittle structure. [Copyright &y& Elsevier]

Enzyme kinetics studies normally focus on the initial rate of enzymatic reaction. However, the manual operation of steps of the conventional enzyme kinetics method has some drawbacks. Errors can result from the imprecise time control and time necessary for manual changing the reaction cuvettes into and out of the detector. By using the automatic flow-based analytical systems, enzyme kinetics studies can be carried out at real-time initial rate avoiding the potential errors inherent in manual operation. Flow-based systems have been developed to provide rapid, low-volume, and high-precision analyses that effectively replace the many tedious and high volume requirements of conventional wet chemistry analyses. This article presents various arrangements of flow-based techniques and their potential use in future enzyme kinetics applications. [ABSTRACT FROM AUTHOR]

The most commonly used technique for water content determination is Karl-Fischer titration with electrometric detection, requiring specialized equipment. When appropriate equipment is not available, the method can be performed through visual detection of a titration endpoint, which does not enable an analysis of colored samples. Here, we developed a method with spectrophotometric detection of a titration endpoint, appropriate for moisture determination of colored samples. The reaction takes place in a sealed 4ml cuvette. Detection is performed at 520 nm. Titration endpoint is determined from the graph of absorbance plotted against titration volume. The method has appropriate reproducibility (RSD = 4.3%), accuracy, and linearity (R² = 0.997). [ABSTRACT FROM AUTHOR]