Tetra‐Face‐Capped Octahedra in a Tetrahedra Network

Tetrahedra-based nitridophosphates show a rich structural chemistry, which can be further extended by incorporating cations in higher coordinated positions, for example, in octahedral voids or by substituting the nitrogen atoms in the network with other anions. Following this approach, SrAl5P4N10O2F3 was synthesized at high-temperature and high-pressure conditions using a multianvil press (1400 °C, 5 GPa) starting from Sr(N3)2, c-PON, P3N5, AlN, and NH4F. SrAl5P4N10O2F3 crystallizes in space group urn:x-wiley:09476539:media:chem202301960:chem202301960-math-0001 with a=11.1685(2) and c=7.84850(10) Å. Atomic-resolution EDX mapping with scanning transmission electron microscopy (STEM) indicates atom assignments, which are further corroborated by bond-valence sum (BVS) calculations. Ten Al3+-centered octahedra form a highly condensed tetra-face-capped octahedra-based unit that is a novel structure motif in network compounds. A network of vertex-sharing PN4 tetrahedra and chains of face-sharing Sr2+-centered cuboctahedra complement the structure. Eu2+-doped SrAl5P4N10O2F3 shows blue emission (λem=469 nm, fwhm=98 nm; 4504 cm−1) when irradiated with UV light

Order and Disorder in Mixed (Si, P)–N Networks Sr2SiP2N6:Eu2+ and Sr5Si2P6N16:Eu2+

In the field of nitride phosphors, which are crucial for phosphor-converted light-emitting diodes, mixed tetrahedral networks hold a significant position. With respect to the wide range of compositions, the largely unexplored (Si, P)–N networks are investigated as potential host structures. In this work, two highly condensed structures, namely Sr2SiP2N6 and Sr5Si2P6N16 are reported to address the challenges that arise from the similarities of the network-forming cations Si4+ and P5+ in terms of charge, ionic radius, and atomic scattering factor, a multistep workflow is employed to elucidate their structure. Using single-crystal X-ray diffraction, energy-dispersive X-ray spectroscopy (EDX), atomic-resolution scanning transmission electron microscopy (STEM)-EDX maps, and straightforward crystallographic calculations, it is found that Sr2SiP2N6 is the first ordered, and Sr5Si2P6N16 the first disordered, anionic tetrahedral (Si, P)–N network. After doping with Eu2+, Sr2SiP2N6:Eu2+ shows narrow cyan emission (λmax = 506 nm, fwhm = 60 nm/2311 cm−1), while for Sr5Si2P6N16:Eu2+ a broad emission with three maxima at 534, 662, and 745 nm upon irradiation with ultraviolet light is observed. An assignment of Sr sites as probable positions for Eu2+ and their relation to the emission bands of Sr5Si2P6N16:Eu2+ is discussed

Towards long-term records of rain-on-snow events across the Arctic from satellite data

Rain-on-snow (ROS) events occur across many regions of the terrestrial Arctic in mid-winter. Snowpack properties are changing, and in extreme cases ice layers form which affect wildlife, vegetation and soils beyond the duration of the event. Specifically, satellite microwave observations have been shown to provide insight into known events. Only Ku-band radar (scatterometer) has been applied so far across the entire Arctic. Data availability at this frequency is limited, however. The utility of other frequencies from passive and active systems needs to be explored to develop a concept for long-term monitoring. The latter are of specific interest as they can be potentially provided at higher spatial resolution. Radar records have been shown to capture the associated snow structure change based on time-series analyses. This approach is also applicable when data gaps exist and has capabilities to evaluate the impact severity of events. Active as well as passive microwave sensors can also detect wet snow at the timing of an ROS event if an acquisition is available. The wet snow retrieval methodology is, however, rather mature compared to the identification of snow structure change since ambiguous scattering behaviour needs consideration. C-band radar is of special interest due to good data availability including a range of nominal spatial resolutions (10 m–12.5 km). Scatterometer and SAR (synthetic aperture radar) data have therefore been investigated. The temperature dependence of C-band backscatter at VV (V – vertical) polarization observable down to −40 ◦C is identified as a major issue for ROS retrieval but can be addressed by a combination with a passive microwave wet snow indicator (demonstrated for Metop ASCAT – Advanced Scatterometer – and SMOS – Soil Moisture and Ocean Salinity). Results were compared to in situ observations (snowpit records, caribou migration data) and Ku-band products. Ice crusts were found in the snowpack after detected events (overall accuracy 82 %). The more crusts (events) there are, the higher the winter season backscatter increase at C-band will be. ROS events captured on the Yamal and Seward peninsulas have had severe impacts on reindeer and caribou, respectively, due to ice crust formation. SAR specifically from Sentinel-1 is promising regarding ice layer identification at better spatial details for all available polarizations. The fusion of multiple types of microwave satellite observations is suggested for the creation of a climate data record, but the consideration of performance differences due to spatial and temporal cover, as well as microwave frequency, is crucial. Retrieval is most robust in the tundra biome, where results are comparable between sensors. Records can be used to identify extremes and to apply the results for impact studies at regional scale

Cr5.7Si2.3P8N24 - a Chromium(+IV) Nitridosilicate Phosphate with Amphibole‐type structure

The first nitridic analog of an amphibole mineral, the quaternary nitridosilicate phosphate Cr5.7Si2.3P8N24 was synthesized under high‐pressure high‐temperature conditions at 1400 °C and 12 GPa from the binary nitrides Cr2N, Si3N4 and P3N5, using NH4N3 and NH4F as additional nitrogen source and mineralizing agent, respectively. The crystal structure was elucidated by single‐crystal X‑ray diffraction with microfocused synchrotron radiation (C2/m, a = 9.6002(19), b = 17.107(3), c = 4.8530(10) Å, β = 109.65(3)°). The elemental composition was analyzed by energy dispersive X‐ray spectroscopy. The structure consists of vertex‐sharing PN4‐tetrahedra forming zweier double chains and edge‐sharing (Si,Cr)‐centered octahedra forming separated ribbons. Atomic resolution scanning transmission electron microscopy shows ordered Si and Cr sites next to a disordered Si/Cr site. Optical spectroscopy indicates a band gap of 2.1 eV. Susceptibility measurements show paramagnetic behavior and support the oxidation state Cr+IV, which is confirmed by EPR. The comprehensive analysis expands the field of Cr‐N chemistry and provides access to a nitride analog of one of the most prevalent silicate structures

Glucose Recovery from Different Corn Stover Fractions Using Dilute Acid and Alkaline Pretreatment Techniques

Background: Limited availability of corn stover due to the competing uses (organic manure, animal feed, bio-materials, and bioenergy) presents a major concern for its future in the bio-economy. Furthermore, biomass research has exhibited different results due to the differences in the supply of enzymes and dissimilar analytical methods. The effect of the two leading pretreatment techniques (dilute acid and alkaline) on glucose yield from three corn stover fractions (cob, stalk, and leaf) sourced from a single harvest in Uganda were studied at temperatures 100, 120, 140, and 160 °C over reaction times of 5, 10, 30, and 60 min. Results: From this study, the highest glucose concentrations obtained from the dilute acid (DA) pretreated cobs, stalks, and leaves were 18.4 g/L (66.8% glucose yield), 16.2 g/L (64.1% glucose yield), and 11.0 g/L (49.5% glucose yield), respectively. The optimal pretreatment settings needed to obtain these yields from the DA pretreated samples were at a temperature of 160 °C over an incubation time of 30 min. The highest glucose concentrations obtained from the alkaline (AL) pretreated cobs, stalks, and leaves were 24.7 g/L (81.73% glucose yield), 21.3 g/L (81.23% glucose yield), and 15.0 g/L (51.92% glucose yield), respectively. To be able to achieve these yields, the optimal pretreatment settings for the cobs and stalks were 140 °C and for a retention time of 30 min, while the leaves require optimal conditions of 140 °C and for a retention time of 60 min. Conclusions: The study recommends that the leaves could be left on the field during harvesting since the recovery of glucose from the pretreated cobs and stalks is higher

Changes in Human Fecal Microbiota Due to Chemotherapy Analyzed by TaqMan-PCR, 454 Sequencing and PCR-DGGE Fingerprinting

BACKGROUND: We investigated whether chemotherapy with the presence or absence of antibiotics against different kinds of cancer changed the gastrointestinal microbiota. METHODOLOGY/PRINCIPAL FINDINGS: Feces of 17 ambulant patients receiving chemotherapy with or without concomitant antibiotics were analyzed before and after the chemotherapy cycle at four time points in comparison to 17 gender-, age- and lifestyle-matched healthy controls. We targeted 16S rRNA genes of all bacteria, Bacteroides, bifidobacteria, Clostridium cluster IV and XIVa as well as C. difficile with TaqMan qPCR, denaturing gradient gel electrophoresis (DGGE) fingerprinting and high-throughput sequencing. After a significant drop in the abundance of microbiota (p = 0.037) following a single treatment the microbiota recovered within a few days. The chemotherapeutical treatment marginally affected the Bacteroides while the Clostridium cluster IV and XIVa were significantly more sensitive to chemotherapy and antibiotic treatment. DGGE fingerprinting showed decreased diversity of Clostridium cluster IV and XIVa in response to chemotherapy with cluster IV diversity being particularly affected by antibiotics. The occurrence of C. difficile in three out of seventeen subjects was accompanied by a decrease in the genera Bifidobacterium, Lactobacillus, Veillonella and Faecalibacterium prausnitzii. Enterococcus faecium increased following chemotherapy. CONCLUSIONS/SIGNIFICANCE: Despite high individual variations, these results suggest that the observed changes in the human gut microbiota may favor colonization with C. difficile and Enterococcus faecium. Perturbed microbiota may be a target for specific mitigation with safe pre- and probiotics

The Application of DNA Barcodes for the Identification of Marine Crustaceans from the North Sea and Adjacent Regions

During the last years DNA barcoding has become a popular method of choice for molecular specimen identification. Here we present a comprehensive DNA barcode library of various crustacean taxa found in the North Sea, one of the most extensively studied marine regions of the world. Our data set includes 1,332 barcodes covering 205 species, including taxa of the Amphipoda, Copepoda, Decapoda, Isopoda, Thecostraca, and others. This dataset represents the most extensive DNA barcode library of the Crustacea in terms of species number to date. By using the Barcode of Life Data Systems (BOLD), unique BINs were identified for 198 (96.6%) of the analyzed species. Six species were characterized by two BINs (2.9%), and three BINs were found for the amphipod species Gammarus salinus Spooner, 1947 (0.4%). Intraspecific distances with values higher than 2.2% were revealed for 13 species (6.3%). Exceptionally high distances of up to 14.87% between two distinct but monophyletic clusters were found for the parasitic copepod Caligus elongatus Nordmann, 1832, supporting the results of previous studies that indicated the existence of an overlooked sea louse species. In contrast to these high distances, haplotype-sharing was observed for two decapod spider crab species, Macropodia parva Van Noort & Adema, 1985 and Macropodia rostrata (Linnaeus, 1761), underlining the need for a taxonomic revision of both species. Summarizing the results, our study confirms the application of DNA barcodes as highly effective identification system for the analyzed marine crustaceans of the North Sea and represents an important milestone for modern biodiversity assessment studies using barcode sequence