String Chopping and Time-ordered Products of Linear String-localized Quantum Fields

For a renormalizability proof of perturbative models in the Epstein–Glaser scheme with string-localized quantum fields, one needs to know what freedom one has in the definition of time-ordered products of the interaction Lagrangian. This paper provides a first step in that direction. The basic issue is the presence of an open set of n-tuples of strings which cannot be chronologically ordered. We resolve it by showing that almost all such string configurations can be dissected into finitely many pieces which can indeed be chronologically ordered. This fixes the time-ordered products of linear field factors outside a nullset of string configurations. (The extension across the nullset, as well as the definition of time-ordered products of Wick monomials, will be discussed elsewhere).     

Quantitative determination of furocoumarins in samples of “Carapiá” by capillary gas chromatography

Summary The occurrence of furocoumarins in the Moraceae has already been demostrated. We present here the results concerning the chemical composition and quantification of furocoumarins from “carapiá” (Dorstenia species, Moraceae) employed in Brazil because of its medicinal properties against skin diseases. A capillary gas chromatographic procedure is described for the simultaneous determination of the furocoumarins (psoralen, bergapten, pimpinellin, and isopimpinellin) in rhizomes and aerial parts ofDorstenia tubicina, Dorstenia asaroides andDorstenia vitifolia and in commercial samples. The method is shown to be sensitive and reproducible, and may have application in the analysis of “carapia” crude drugs.     

High Temperature Gas Chromatography with a Glass Capillary Column for the Analysis of High Molecular Weight Tracers in Smoke Samples from Biomass Burning

A custom-made glass capillary column coated with OV-1701-OH (88% methyl, 7% cyanopropyl, 5% phenylpolysiloxane) was used to analyze smoke samples from biomass combustion of different species of plants collected in the Amazon forest. CS₂ was used as solvent in order to enhance the dissolution and analysis of the heavier molecular weight components. The performance of the column was monitored during the experiments and a moderate increase in activity was observed after taking the column to high analytical temperatures (390°C). Trennzahl values typically dropped 20–30% from 1.7/m to the average of 1.35/m. In general, the performance of the custom-made column was satisfactory and comparable to the commercial high temperature columns. The high temperature high resolution GC and GC-MS analyses revealed the presence of a number of high molecular weight components reported to occur in smoke aerosols for the first time. These components consisted of series of wax esters (long chain alcohols esterified with long chain fatty acids) with up to 58 carbon numbers, aliphatic hydrocarbons, triglycerides, triterpenyl esters (e.g. α- and β-amyryl stearate). Although other types of compounds were also detected, their complete structure elucidation solely by electron impact MS was not adequate and other techniques will be required.     

Application of High Temperature High Resolution Gas Chromatography to Crude Extracts of Propolis

The underivatized acetone and hexane fractions from propolis samples (predominant flora Citrus spp. and Vernonia polyanthes) were analyzed by HT-HRGC (high temperature high resolution gas chromatography) and HT-HRGC coupled to mass spectrometry (HT-HRGC-MS). Several compounds, including flavonoid aglycones, phenolic acids, and high molecular weight compounds were characterized in crude extracts by HT-HRGC-MS. HT-HRGC and HT-HRGC-MS were shown to be quick and informative tools for rapid analysis of crude extracts without need for prior derivatization and purification.     

Protease Produced by Endophytic Fungi: A Systematic Review

The purpose of this systematic review was to identify the available literature of production, purification, and characterization of proteases by endophytic fungi. There are few complete studies that entirely exhibit the production, characterization, and purification of proteases from endophytic fungi. This study followed the PRISMA, and the search was conducted on five databases: PubMed, PMC, Science Direct, Scopus Articles, and Web of Science up until 18 May 2021, with no time or language restrictions. The methodology of the selected studies was evaluated using GRADE. Protease production, optimization, purification, and characterization were the main evaluated outcomes. Of the 5540 initially gathered studies, 15 met the inclusion criteria after a two-step selection process. Only two studies optimized the protease production using statistical design and two reported enzyme purification and characterization. The genus Penicillium and Aspergillus were the most cited among the eleven different genera of endophytic fungi evaluated in the selected articles. Six studies proved the ability of some endophytic fungi to produce fibrinolytic proteases, demonstrating that endophytic fungi can be exploited for the further production of agents used in thrombolytic therapy. However, further characterization and physicochemical studies are required to evaluate the real potential of endophytic fungi as sources of industrial enzymes.     

Artificial neural networks applied to the classification of hair samples according to pigment and sex using non-invasive analytical techniques

In this study, we investigated the possibility of using an artificial neural network (ANN) to classify human hair samples according to pigment (original or bleached hair) and sex (female or male) from numerical data obtained by wavelength dispersive X-ray fluorescence (WDXRF) and by laser-induced breakdown spectroscopy (LIBS). The results were promising, showing that the developed ANNs are able to classify the pigment and donor sex of hair samples with 100% and 89.5% accuracy, respectively, in the test set using WDXRF data. For the LIBS data in the test set, 100% of the pigment classifications were correct, and 78.9% of the donor sex classifications were correct.     

Open tubular liquid chromatography: Recent advances and future trends

Nano-liquid chromatography (nanoLC) is gaining significant attention as a primary analytical technique across various scientific domains. Unlike conventional high-performance LC, nanoLC utilizes columns with inner diameters (i.ds.) usually ranging from 10 to 150 μm and operates at mobile phase flow rates between 10 and 1000 nl/min, offering improved chromatographic performance and detectability. Currently, most exploration of nanoLC has focused on particle-packed columns. Although open tubular LC (OTLC) can provide superior performance, optimized OTLC columns require very narrow i.ds. (< 10 μm) and demand challenging instrumentation. At the moment, these challenges have limited the success of OTLC. Nevertheless, remarkable progress has been made in developing and utilizing OTLC systems featuring narrow columns (< 2 μm). Additionally, significant efforts have been made to explore larger columns (10–75 μm i.d), demonstrating practical applicability in many situations. Due to their perceived advantages, interest in OTLC has resurged in the last two decades. This review provides an updated outlook on the latest developments in OTLC, focusing on instrumental challenges, achievements, and advancements in column technology. Moreover, it outlines selected applications that illustrate the potential of OTLC for performing targeted and untargeted studies.