Sample plug induced peak splitting in capillary electrophoresis studied using dual backscattered interferometry and fluorescence detection

The appearance of unexpected peaks in capillary electrophoresis (CE) is common and can lengthen the time of method development as assay conditions and experimental parameters are varied to understand and mitigate the effects of the additional peaks. Additional peaks can arise when a single-analyte zone is split into multiple zones. Understanding the underlying mechanism of these phenomena, recognizing conditions that favor its presence, and knowing how to confirm and eliminate the effect are important for efficient method optimization. In this study, we examine how the overlap of analyte zones with the sample plug can lead to peak splitting. This is explored experimentally using dual detection CE, which enables both the sample plug and analyte zones to be independently and simultaneously measured from the same detection volume. Simulations performed via COMSOL Multiphysics confirm the origin of the splitting and help guide experiments to reduce and eliminate the effect. Our findings show that this peak splitting mechanism can arise in separations of both small and large molecules but is, especially, prevalent in separations of slowly migrating macromolecules. This effect is also more prevalent when using a short length-to-detector, as is commonly found in microfluidic applications. A simple diffusion-less model is introduced to develop strategies for reducing peak splitting that avoids modifying the apparatus, such as by lengthening the separation length, which can be difficult. Decreasing the sample plug length and slowing the electroosmotic flow can both reduce this effect, which is confirmed experimentally.     

Separating Vibrational Coherences in Ground/Excited Electronic States of Solvent/Solute Following Non-Resonant/Resonant Impulsive Excitation

In a quest to track down the origin of coherent vibrational motions observed in femtosecond pump-probe transients, whether they arise from ground/excited electronic state of solute or are contributed by the solvent, we demonstrate a method for extricating vibrations under resonant and non-resonant impulsive excitations using a diatomic solute in condensed phase (iodine in carbon tetrachloride) with aid of spectral dispersion of the chirped broadband probe. Most importantly, we show how a sum over intensities for a select region of detection wavelengths and Fourier transform of data over select temporal window untwine contributions from vibrational modes of different origins. Thus, in a single pump-probe experiment, vibrational features specific to solute as well as solvent are disentangled that are otherwise spectrally overlapping and are non-separable in conventional (spontaneous/stimulated) Raman spectroscopy employing narrowband excitation. We envision wide-ranging applications of this method to unveil vibrational features in complex molecular systems.     

Two New Triterpene Saponins from the Seed Residue of Hippophae rhamnoides L.

Two new triterpene saponins, named hippophosides E and F ( 1 and 2 , resp.), together with two known compounds, were isolated from the seed residue of Hippophae rhamnoides L. Their structures were elucidated on the basis of chemical and spectral analysis, including 1D‐ and 2D‐NMR and HR‐MS experiments, and by comparison with literature data.     

Effects of pH and Carbon Source on <Emphasis Type="Italic">Synechococcus</Emphasis> PCC 7002 Cultivation: Biomass and Carbohydrate Production with Different Strategies for pH Control

Synechococcus PCC 7002 is an interesting species in view of industrial production of carbohydrates. The cultivation performances of this species are strongly affected by the pH of the medium, which also influences the carbohydrate accumulation. In this work, different methods of pH control were analyzed, in order to obtain a higher production of both Synechococcus biomass and carbohydrates. To better understand the influence of pH on growth and carbohydrate productivity, manual and automatic pH regulation in CO₂ and bicarbonate system were applied. The pH value of 8.5 resulted the best to achieve both of these goals. From an industrial point of view, an alternative way to maintain the pH practically constant during the entire period of cultivation is the exploitation of the bicarbonate-CO₂ buffer system, with the double aim to maintain the pH in the viability range and also to provide the amount of carbon required by growth. In this condition, a high concentration of biomass (6 g L^?1) and carbohydrate content (around 60 %) were obtained, which are promising in view of a potential use for bioethanol production. The chemical equilibrium of C-N-P species was also evaluated by applying the ionic balance equations, and a relation between the sodium bicarbonate added in the medium and the equilibrium value of pH was discussed.     

On the power of rewinding simulators in functional encryption

In a seminal work, Boneh, Sahai and Waters (BSW) [TCC’11] showed that for functional encryption the indistinguishability notion of security (IND-Security) is weaker than simulation-based security (SIM-Security), and that SIM-Security is in general impossible to achieve. This has opened up the door to a plethora of papers showing feasibility and new impossibility results. Nevertheless, the quest for better definitions that (1) overcome the limitations of IND-Security and (2) the known impossibility results, is still open. In this work, we explore the benefits and the limits of using efficient rewinding black-box simulators to argue security. To do so, we introduce a new simulation-based security definition, that we call rewinding simulation-based security (RSIM-Security), that is weaker than the previous ones but it is still sufficiently strong to not meet pathological schemes as it is the case for IND-Security (that is implied by the RSIM). This is achieved by retaining a strong simulation-based flavour but adding more rewinding power to the simulator having care to guarantee that it can not learn more than what the adversary would learn in any run of the experiment. What we found is that for RSIM  the BSW impossibility result does not hold and that IND-Security is equivalent to RSIM-Security for attribute-based encryption in the standard model. Nevertheless, we prove that there is a setting where rewinding simulators are of no help. The adversary can put in place a strategy that forces the simulator to rewind continuously.     

Classification of partial difference sets in Abelian groups of order $$4p^2$$

In this article we provide a complete classification of regular partial difference sets in Abelian groups of order \(4p^2\), p an odd prime. It turns out that the known examples are the only examples. These are, up to complements, the trivial examples, the PCP examples, and a sporadic example in \(\mathbb {Z}_2^2\times \mathbb {Z}_3^2\).     

Enantioselective addition of Et2Zn to seven‐membered cyclic imines catalyzed by a (R)-VAPOL-Zn(II) complex

Various substituted dibenzo[b,f][1,4]oxazepines underwent an enantioselective alkylation with Et₂Zn catalyzed by a (R)-VAPOL-Zn(II) complex. The corresponding chiral 11-ethyl-10,11-dihydrodibenzo[b,f][1,4]oxazepine derivatives were obtained with good yields and moderate enantioselectivities. This represents the first example of enantioselective addition of Et₂Zn to cyclic aldimines.     

Elastic modulus and yield stress of suspensions

A recent technique, developed to measure yield stress has here also been used to determine the elastic modulus of a suspension. Temperature effects have been measured.     

Fracture data and stress-strain behavior of rocks in triaxial compression

Test results are reported for a recently completed experimental research program on rocks subjected to triaxial compression. Sandstone, marble, granite and shale specimens were tested at confining pressures as high as 90,000 psi corresponding to mean stresses of up to 143,000 psi. Recognizing that the largest potential experimental error in such tests results from making strain and load measurements external to the vessel, special load and strain-measuring devices were designed and fabricated for use inside the pressure vessel. The specimens were carefully machined cylinders with length-to-diameter ratios of two and with diameters ranging from 4/16 in. to 1 in. The confining pressure was held constant during each run, but varied from 0 to 90,000 psi over the tests. Results are reported in the form of:

1. Stress-strain curves for individual specimens
2. Maximum shear stress at fracture vs. mean-stress curves for each rock type tested
3. Tabulation of results for 59 specimens

A number of tests were run on granite specimens which had been previously fractured. Results from these tests showed good agreement with tests on intact granite, providing the confining pressure was above 30,000 psi.