Protonation of γ-Butyrolactone and γ-Butyrolactam.

Invited for this month's cover is the group of Andreas Kornath at the Ludwig-Maximilian University of Munich (Germany). The cover picture shows the crystal structures of protonated γ-butyrolactone ([(CH2 )3 OCOH][AsF6 ]) and γ-butyrolactam ([(CH2 )3 NHCOH][AsF6 ]). Both salts were synthesized by reacting the neutral compounds in the superacidic system HF/AsF5 at low temperature. Interestingly, the X-ray structure analyses revealed not only structural parameters of the salts, but also the existent of C⋅⋅⋅F contacts in both species. Quantum chemical calculations were performed to investigate the nature of these contacts. Read the full text of their Full Paper at 10.1002/open.202000220.

Protonation of γ-Butyrolactone and γ-Butyrolactam.

γ-Butyrolactone and γ-butyrolactam were reacted in the superacidic systems XF/MF5 (X=H, D; M=As, Sb). Salts of the monoprotonated species of γ-butyrolactone were obtained in terms of [(CH2 )3 OCOH]+ [AsF6 ]- , [(CH2 )3 OCOH]+ [SbF6 ]- and [(CH2 )3 OCOD]+ [AsF6 ]- and the analogous lactam salts in terms of [(CH2 )3 NHCOH]+ [AsF6 ]- , [(CH2 )3 NHCOH]+ [SbF6 ]- and [(CH2 )3 NDCOD]+ [AsF6 ]- . The salts were characterized by low temperature Raman and infrared spectroscopy and for both protonated hexafluoridoarsenates, [(CH2 )3 OCOH]+ [AsF6 ]- and [(CH2 )3 NHCOH]+ [AsF6 ]- , single-crystal X-ray structure analyses were conducted. In addition to the experimental results, quantum chemical calculations were performed on the B3LYP/aug-cc-pVTZ level of theory. As in both crystal structures C⋅⋅⋅F contacts were observed, the nature of these contacts is discussed with Mapped Electrostatic Potential as a rate of strength.

Portable high-resolution automated 3D imaging for footwear and tire impression capture.

The forensic science community raised the need for improved evidence recognition, collection, and visualization analytical instrumentation for field and laboratory use. While the 3D optical techniques for imaging static objects have been extensively studied, there is still a major gap between current knowledge and collecting high-quality footwear and tire impression evidence. Among optical means for 3D imaging, digital fringe projection (DFP) techniques reconstruct 3D shape from phase information, achieving camera-pixel spatial resolution. This paper presents a high-resolution 3D imaging technology using DFP techniques dedicated to footwear and tire impression capture. We developed fully automated software algorithms and a graphical user interface (GUI) that allow anyone without training to operate for high-quality 3D data capture. We performed accuracy evaluations and comparisons comparing with the commercial high-end 3D scanner and carried out qualitative tests for various impressions comparing with the current practices. Overall, our technology achieves similar levels of accuracy and resolution with a high-end commercially available 3D scanner, while having the merits of being (1) more affordable; (2) much easier to operate; and (3) more robust. Compared with the current practice of casting, our technology demonstrates its superiority because it (1) is non-destructive; (2) collects more evidence detail than casts, especially when an impression is fragile; (3) requires less time and money to collect each piece of evidence; and (4) results in a digital file that can easily be shared with other examiners.

Twenty years of ecosystem response after clearcutting and slashburning in conifer forests of central British Columbia, Canada.

Forests are being clearcut over extensive areas of western North America, but plant community response to harvesting and slashburning under varying climatic conditions in central British Columbia, Canada is still largely unknown. Evaluation of resilience is hampered by the short history of logging, lack of long-term experiments and methodological limitations. To test the effect of clearcut logging, prescribed burning and reforestation on forest resilience, we recorded vascular plant cover repeatedly after treatment between 1981 and 2008 in 16 permanent research installations in three biogeoclimatic zones: Engelmann Spruce-Subalpine Fir, Interior Cedar-Hemlock and Sub-Boreal Spruce. We created a plant-trait dataset for the 181 recorded species to define plant functional types representing groups of plants that behave in similar ways and/or produce similar ecological outcomes. These plant functional types, along with taxonomic analysis of diagnostic and indicator species, were then used to evaluate plant community response to disturbance. Twenty years post-treatment, species diversity increased in all zones and plant abundance was greatest in the Interior Cedar-Hemlock. Cover of understory plant functional types associated with mature conifer forests increased in all zones, constituting a significant proportion (> 40%) of the vegetation community by year 20. Response patterns varied by zone and with time. Understory species diagnostic of mature forests were present in all zones by year 20, but we identified indicator species sensitive to slashburning or requiring more time for recovery, including white-flowered rhododendron (Rhododendron albiflorum) and devil's club (Oplopanax horridus). Overall, loss of compositional or functional diversity following harvest and site remediation was not detected, suggesting that montane and subalpine forests in British Columbia are resilient to this treatment. However, because these forests can be slow to recover from disturbance, the post-disturbance assessment window of this study may not have been long enough to detect diminishment of ecosystem resilience.