Rapid phytochemical analysis of birch (Betula) and poplar (Populus) foliage by near-infrared reflectance spectroscopy

Poplar (Populus) and birch (Betula) species are widely distributed throughout the northern hemisphere, where they are foundation species in forest ecosystems and serve as important sources of pulpwood. The ecology of these species is strongly linked to their foliar chemistry, creating demand for a rapid, inexpensive method to analyze phytochemistry. Our study demonstrates the feasibility of using near-infrared reflectance spectroscopy (NIRS) as an inexpensive, high-throughput tool for determining primary (e.g., nitrogen, sugars, starch) and secondary (e.g., tannins, phenolic glycosides) foliar chemistry of Populus and Betula species, and identifies conditions necessary for obtaining reliable quantitative data. We developed calibrations with high predictive power (residual predictive deviations?≤?7.4) by relating phytochemical concentrations determined with classical analytical methods (e.g., spectrophotometric assays, liquid chromatography) to NIR spectra, using modified partial least squares regression. We determine that NIRS, although less sensitive and precise than classical methods for some compounds, provides useful predictions in a much faster, less expensive manner than do classical methods.

DIC Challenge 2.0: Developing Images and Guidelines for Evaluating Accuracy and Resolution of 2D Analyses

Experimental Mechanics - The DIC Challenge 2.0 follows on from the work accomplished in the first Digital Image Correlation (DIC) Challenge Reu et al. (Experimental Mechanics 58(7):1067, 1). The...     

First total synthesis of cichorine and zinnimidine

The first total synthesis of the phytotoxins cichorine and zinnimidine is described. The synthetic tactics involve the sequential connection of the dense and diverse functionalities on the aromatic nucleus followed by a Parham cyclization process, giving rise to the lactam unit embedded in the title compound framework.     

A new route to aristocularine alkaloids: total synthesis of aristoyagonine

A short and efficient synthesis of aristocularines, involving the sequential construction of phosphorylated 4-alkoxyisoindolinones, Horner-type reaction, and ultimate cyclization by diaryl ether coupling, is disclosed. The success of this new conceptual approach is demonstrated by the total synthesis of the aristocularine alkaloid aristoyagonine.     

The Piracicaba River basin: isotope hydrology of a tropical river basin under anthropogenic stress

The stable isotope content of samples of precipitation and of the river water throughout the Piracicaba basin in Brazil was measured over a two-year period. The isotope values of precipitation follow a consistent pattern of relatively depleted values of both deuterium and oxygen 18 during the rainy summers and enriched ones during the dry winters, with all values aligned slightly above the Global Meteoric Water Line. The isotopic composition of the river water throughout the basin shows a remarkable spatial coherence and much smaller scatter of data than those of the precipitation. The isotope composition of river water is close to that of the precipitation in the rainy season, however, with a consistent lower d-excess value by 1/1000-2/1000. This is attributed to evaporative water loss in the basin, in part an expression of the recycling of water due to the anthropogenic activity in the region. The more divergent values are recorded during high-water stages in the rivers. In many cases, the floods during the beginning of the rainy season are characterized by an enrichment of the heavy isotopes and lower d-excess values when compared to the precipitation, with the opposite situation later in the rainy season. This is interpreted as resulting from the watershed/riverflow interaction pattern, and it thus suggests that the isotope composition can monitor the hydrologic situation in the basin and its changes.     

A concise total synthesis of the azaphenanthrene alkaloid eupolauramine.

A six-step total synthesis of the azaphenanthrene alkaloid eupolauramine 1 has been achieved using combinational metalation-cyclization tactics. The synthetic route involved first the construction of the azaisoindolinone 9 by aryne-mediated cyclization of he phosphorylated pyridocarboxamide 7 and subsequent dephosphorylation. Metalation of 9 followed by connection of the hydroxybenzyl appendage and E(1)CB anti-elimination allowed the formation of the halogenoarylmethylene azaisoindolinone 4 in the exclusive E-form. Oxidative radical cyclization gave rise to the azaphenanthrene skeleton and regioselective bromination of 3 induced the incorporation of the bromine atom at the 6-position of the azaphenanthrene lactam. Ultimate replacement of the bromine atom of 2 by the methoxy functionality by sequential transmetalation, in situ oxidation, and O-methylation of the phenolic derivative 14 completed the synthesis of the target natural product eupolauramine.     

Stereoselective photoinduced electrocyclic ring closure of aromatic enehydrazides. Asymmetric synthesis of 3-aryl dihydroisoquinolones and tetrahydroisoquinolines

A flexible route for the stereoselective synthesis of a variety of 3-aryl dihydroisoquinolones and tetrahydroisoquinolines has been developed. The key step is a diastereoselective photoinduced 6π-electrocyclic ring closure of enantiopure aromatic enehydrazides via a 1,4-remote asymmetric induction. N–N bond cleavage to release the chiral appendage from the preliminary annulated compounds and/or concomitant reduction of the lactam carbonyl group completed the synthesis of the title compounds.     

On longitudinal mode spacing of laser cavities with pairs of gratings

It has recently been suggested that a laser cavity formed by a pair of gratings would show anomalously large longitudinal mode spacing which should favor single-longitudinal-mode emission. An experimental verification of that prediction with a TEA-CO₂ laser is presented. The repeatedly negative results obtained under various conditions are given a tentative explanation, based on the well-known analysis of a closely related problem: the grating-pair pulse compression scheme.