bluuebunny/crossref_metadata_2025_split huggingface dataset:
Investigating the relative permeability behavior of microporosity‐rich carbonates and tight sandstones with multiscale pore network models
Authors: Bultreys Tom , Stappen Jeroen Van , Kock Tim De , Boever Wesley De , Boone Marijn A. , Hoorebeke Luc Van , Cnudde Veerle 
Published: October 2016

AbstractThe relative permeability behavior of rocks with wide ranges of pore sizes is in many cases still poorly understood and is difficult to model at the pore scale. In this work, we investigate the capillary pressure and relative permeability behavior of three outcrop carbonates and two tight reservoir sandstones with wide, multimodal pore size distributions. To examine how the drainage and imbibition properties of these complex rock types are influenced by the connectivity of macropores to each other and to zones with unresolved small‐scale porosity, we apply a previously presented microcomputed‐tomography‐based multiscale pore network model to these samples. The sensitivity to the properties of the small‐scale porosity is studied by performing simulations with different artificial sphere‐packing‐based networks as a proxy for these pores. Finally, the mixed‐wet water‐flooding behavior of the samples is investigated, assuming different wettability distributions for the microporosity and macroporosity. While this work is not an attempt to perform predictive modeling, it seeks to qualitatively explain the behavior of the investigated samples and illustrates some of the most recent developments in multiscale pore network modeling.
Diacetyl (Butandion) [Air Monitoring Methods in German language, 2016a]
Authors: Schuh C. , Kirchner M. , Hebisch R. , Hartwig A. ,   MAK Commission
Published: October 2016

Diacetyl (Butanedione) – Determination of diacetyl in workplace air using liquid chromatography (HPLC‐UV or HPLC‐MS)This analytical method is a validated measurement procedure for the determination of 2,3‐butanedione (diacetyl) in workplace air in a concentration range of a tenth up to twice the currently valid Occupational Exposure Limit (OEL) or MAK value. Sampling is performed by drawing a defined volume of air through a cartridge filled with silica gel impregnated with 2,4‐dinitrophenylhydrazine (DNPH) using a suitable flow‐regulated pump with a volumetric flow rate of 1 mL/min. For sampling 1 hour or 15 min (checking the short‐term value) can be used. The formed diacetyl‐2,4‐DNPH derivatives are desorbed with acetonitrile containing a defined amount of DNPH and analysed by means of liquid chromatography (HPLC‐UV or HPLC‐MS). Quantitative evaluation is based on a 10‐point calibration using methacrolein‐2,4‐DNPH as internal standard. The limit of quantification for diacetyl is 0.002 mg/m3based on an air sample volume of approx. 60 L or 0.006 mg/m3based on an air sample volume of approx. 15 L (for short‐term value).
Xylol (alle Isomere), Addendum [BAT Value Documentation in German language, 2016]
Authors: Jäger T. , Drexler H. , Hartwig A. ,   MAK‐Kommission
Published: October 2016

Addendum to Xylene (all isomers)
The German Commission for the Investigation of Health Hazards of Chemical Compounds in the Work Area has re‐evaluated the biological tolerance value at the work place (BAT value) for xylene and its isomers, considering xylene in blood and methylhippuric (toluric) acid (all isomers) to characterize the internal exposure. Xylene can easily pass through the skin, so biological monitoring is necessary for a valid individual risk assessment.
Xylene shows a fast elimination in the blood compartment. Thus, the concentration of xylene in blood is halved 30 minutes after the end of exposure. Therefore, sampling should be performed directly at the end of exposure. This is, however, difficult to realize in practice. Therefore, the BAT value for xylene (all isomers) in blood was withdrawn. Methylhippuric (toluric) acid in urine is available as a diagnostically specific parameter. The BAT value for methylhippuric acid is confirmed.
Dichlormethan, Addendum [BAT Value Documentation in German language, 2016]
Authors: Bolt H. M. , Weistenhöfer W. , Drexler H. , Hartwig A. ,   MAK‐Kommission
Published: October 2016

Addendum to Dichloromethane
The German Commission for the Investigation of Health Hazards of Chemical Compounds in the Work Area has re‐evaluated dichloromethane, considering dichloromethane in blood to characterize the internal exposure.

In a chamber study, 14 non‐smokers were exposed to different concentrations of dichloromethane. After exposure to the present MAK‐value of 50 ml dichloromethane/m
3
without physical activity, a concentration of 0.3 mg dichloromethane/l blood was measured. Considering an increased intake due to elevated breathing volume during work, the exposure to 50 ml dichloromethane/m
3
results in a blood concentration of 0.5 mg/l. Taking into account this study and the EKA correlation of 2001, a BAT‐value of 500 µg dichloromethane/l blood was evaluated. Sampling time is straight after exposure.
Naphthalin [BAT Value Documentation in German language, 2016]
Authors: Klotz K. , Drexler H. , Hartwig A. ,   MAK‐Kommission
Published: October 2016

NaphthaleneThe German Commission for the Investigation of Health Hazards of Chemical Compounds in the Work Area has evaluated a BAR (“Biologischer Arbeitsstoff Referenzwert”) for naphthalene, considering 1‐ and 2‐naphthol in urine to characterize the internal exposure. Naphthalene is classified in category 2 for carcinogenic substances and designated with an “H” because of its contribution to the toxicological hazards due to penetration through the skin in vitro and dermal absorption in vivo.In a number of biomonitoring studies, the excretion of 1‐ and 2‐naphthol in urine of persons occupationally not exposed to naphthalene was examined. Tobacco smoking affects the naphthol excretion significantly, thus non‐smokers and smokers have to be considered separately. Up to now, no data of representative collectives of the German general population are available. Therefore, the largest German study was considered for the evaluation, where urine samples of 95 non‐smokers were analysed and a 95th percentile for the sum of 1‐ and 2‐naphthol (after hydrolysis) of 33.6 µg/l (30.6 µg/g creatinine) was found. These results are in good accordance with other national and international studies. Therefore, a BAR of 35 µg 1‐ plus 2‐naphthol (after hydrolysis)/l urine was evaluated for non‐smokers. Sampling time is at the end of exposure or the end of the working shift and after long term exposure at the end of the working shift after several shifts. For the interpretation of the result, the smoking status of the persons has to be considered. In case of an occupational co‐exposure to other polycyclic aromatic hydrocarbons (PAH), the analysis of additional PAH‐metabolites is recommended (see MAK Documentation “Polycyclic Aromatic Hydrocarbons”).
β‐Hydroxyethoxyessigsäure (HEAA) in Urin [Biomonitoring Methods in German Language, 2015]
Authors: Leng G. , Gries W. , Göen T. , Bader M. , Eckert E. , Hartwig A. ,   MAK Commission
Published: October 2016

β‐Hydroxyethoxyacetic acid (HEAA) in urineThe documentation presents the selective detection of β‐hydroxyethoxyacetic acid (HEAA), which is considered to be the main metabolite of 1,4‐dioxane and diethylene glycol, respectively.The urine sample to be analyzed is diluted with purified water and, after addition of the deuterated internal standard (D4‐HEAA), acidified with concentrated hydrochloric acid and then extracted with ethyl acetate. An aliquot of the ethyl acetate phase is evaporated to dryness under a stream of nitrogen. The residue is derivatized by addition of N‐methyl‐N‐(trimethylsilyl)trifluoroacetamide (MSTFA) and the bis‐silylated β‐hydroxyethoxyacetic acid is analyzed after electron impact ionization using GC–MS in the Selected Ion Monitoring (SIM) mode.
Ziram [MAK Value Documentation, 2015]
Authors: Hartwig A. ,   MAK Commission
Published: October 2016

The German Commission for the Investigation of Health Hazards of Chemical Compounds in the Work Area has evaluated ziram to derive a maximum concentration at the workplace (MAK value), considering all toxicological endpoints. Available publications and unpublished study reports are described in detail. The critical effect is inflammation, squamous metaplasia, hyperplasia, and necrosis of cartilage in the larynx of rats after 28‐day inhalation exposure to 0.3 mg/m
3
. From the NOAEC of 0.1 mg/m
3
a MAK value of 0.01 mg/m
3
for the inhalable fraction has been established. With the critical effect being local, ziram has been classified in Peak Limitation Category I. An excursion factor of 2 has been established as acute irritation is not expected if twice the MAK value is exceeded.

In one of three oral carcinogenicity studies in mice a significantly increased incidence of lung tumours was observed but coincided with a Sendai virus infection, therefore, this finding cannot unequivocally be regarded as substance‐induced. In one of three oral carcinogenicity studies in rats a significantly increased incidence of thyroid C‐cell carcinomas in male F344 rats was observed. As these tumours were not reproduced in other studies using higher doses and higher‐purity ziram and may have an incidence of up to 33% in untreated F344 rats, C‐cell carcinomas in male F344 rats are regarded as an isolated finding and have not resulted in the classification of ziram in one of the categories for carcinogenic substances.
Ziram did not demonstrate any mutagenicity in rats or mice or clastogenicity in mice.

The NOAEL for developmental toxicity accompanied by maternal toxicity was 16 mg/kg body weight and day in rats and 7.5 mg/kg body weight and day in rabbits, corresponding to ziram concentrations of 24 or 19 mg/m
3
. The NOAEL for developmental neurotoxicity was 12 mg/kg body weight and day, corresponding to 18 mg/m
3
. Thus, there is a sufficiently large margin between levels that cause developmental toxicity or developmental neurotoxicity and the MAK value of 0.01 mg ziram/m
3
I has been classified in Pregnancy Risk Group C.

Ziram shows a skin sensitizing potential in animals, which is also supported by the clinical and experimental findings obtained with the structurally closely‐related zinc diethyldithiocarbamate. Ziram has been labelled with “Sh” (for substances which cause sensitization of the skin), but not with “Sa” (for substances which cause sensitization of the airways).
Dermal absorption of ziram is low and does not contribute significantly to systemic toxicity.
Diacetyl [MAK Value Documentation, 2015]
Authors: Hartwig A. ,   MAK Commission
Published: October 2016

The German Commission for the Investigation of Health Hazards of Chemical Compounds in the Work Area has evaluated diacetyl to derive a maximum concentration at the workplace (MAK value), considering all toxicological endpoints. The critical effects in popcorn workers exposed to diacetyl are subclinical changes in lung function, airway obstruction and bronchiolitis obliterans. That means diacetyl produces irreversible cumulative effects in the lungs. No effects on the forced expiratory volume in one second (FEV1) and the forced vital capacity (FVC) of the workers were recorded at a cumulative exposure of 0.65 ml/m3 × year. Extrapolation of this value with Haber's Rule to occupational exposure for 40 years results in a value of 0.016 ml/m3. Effects on the nasal and respiratory epithel found in mice exposed for 12 weeks to diacetyl concentrations of 25 ml/m3do not contradict the effects on the lungs in workers exposed to diacetyl. The MAK value for diacetyl is derived on the basis of human data only, because humans have a higher sensitivity to diacetyl. A MAK value of 0.02 ml/m3is set. As the critical effect is a cumulative long‐term effect in the lungs, Peak Limitation Category II is assigned. To avoid triggering bronchiolitis obliterans by short‐term peak inhalation exposure an excursion factor of 1 is set. Skin contact may contribute significantly to systemic toxicity and diacetyl is designated with an “H” notation. Positive results from local lymph node assays in the mouse indicate that diacetyl has a low skin‐sensitizing potency. Because there is no developmental toxicity in hamsters, mice and rats, damage to the embryo or foetus is unlikely when the MAK value is observed and thus, diacetyl is classified in Pregnancy Risk Group C. In view of the genotoxicity of diacetyl in vitro and the local genotoxicity in vivo, local genotoxicity in the lungs is suspected; diacetyl is therefore classified in Carcinogen Category 3B.
Cyclo‐P4‐Bausteine – Verwirklichung nichtklassischer Fulleren‐Analogie und weiterer Topologien
Authors: Dielmann Fabian , Peresypkina Eugenia V. , Krämer Barbara , Hastreiter Florian , Johnson Brian P. , Zabel Manfred , Heindl Claudia , Scheer Manfred 
Published: October 2016

AbstractDie cyclo‐P4‐Komplexe [CpRTa(CO)2(η4‐P4)] (CpR: Cp′′=1,3‐C5H3tBu2, Cp′′′=1,2,4‐C5H2tBu3) erweisen sich als prädestiniert zur Bildung von hohlen sphärischen Supramolekülen mit nichtklassischer Fulleren‐artiger Topologie. Die resultierenden Aggregate, die mittels CuX (X=Cl, Br) aufgebaut werden, zeigen ein hochsymmetrisches 32er‐Gerüst, das ausschließlich aus vier‐ und sechsgliedrigen Ringen aufgebaut ist. In einigen Supramolekülen ist der innere Hohlraum durch zusätzliche CuX‐Einheiten besetzt. Bei Verwendung von CuI werden zwei unterschiedliche Supramoleküle mit Erdnuss‐ oder Birnen‐förmigen Gerüsten und 2–2.5 nm Außendurchmesser isoliert. Weiterhin sind die sphärischen Supramoleküle mit Cp′′′‐substituierten Tantalkomplexen in CH2Cl2 löslich. NMR‐spektroskopische Untersuchungen in Lösung zeigen die Bildung von isomeren Supramolekülen infolge der sterischen Hinderung durch die dritte tBu‐Gruppe des Cp′′′‐Liganden. Zusätzlich wird ein 2D‐Koordinationspolymer erhalten und strukturell charakterisiert.
Slow Molecular Motions in Ionic Liquids Probed by Cross‐Relaxation of Nuclear Spins During Overhauser Dynamic Nuclear Polarization
Authors: Banerjee Abhishek , Dey Arnab , Chandrakumar Narayanan 
Published: October 2016

AbstractSolution‐state Overhauser dynamic nuclear polarization (ODNP) at moderate fields, performed by saturating the electron spin resonance (ESR) of a free radical added to the sample of interest, is well known to lead to significant NMR signal enhancements in the steady state, owing to electron–nuclear cross‐relaxation. Here it is shown that under conditions which limit radical access to the molecules of interest, the time course of establishment of ODNP can provide a unique window into internuclear cross‐relaxation, and reflects relatively slow molecular motions. This behavior, modeled mathematically by a three‐spin version of the Solomon equations (one unpaired electron and two nuclear spins), is demonstrated experimentally on the 19F/1H system in ionic liquids. Bulky radicals in these viscous environments turn out to be just the right setting to exploit these effects. Compared to standard nuclear Overhauser effect (NOE) work, the present experiment offers significant improvement in dynamic range and sensitivity, retains usable chemical shift information, and reports on molecular motions in the sub‐megahertz (MHz) to tens of MHz range—motions which are not accessed at high fields.
Substratmodulierte reduktive Graphenfunktionalisierung
Authors: Schäfer Ricarda A. , Weber Konstantin , Koleśnik‐Gray Maria , Hauke Frank , Krstić Vojislav , Meyer Bernd , Hirsch Andreas 
Published: October 2016

AbstractDie kovalente Funktionalisierung von mechanisch exfoliertem Graphenid‐Monolagen und ‐Bilagen auf SiO2‐Wafern mit λ‐Iodanen und anschließende Raman‐spektroskopische/‐mikroskopische Charakterisierung haben gezeigt, dass Graphen‐Monolagen bedeutend reaktiver sind als entsprechende Bilagen. Mittels unterstützender Dichtefunktionalrechnungen konnten wir zeigen, dass die ditope Addendenbindung zu sehr viel stabileren Produkten führt als die entsprechende monotope Reaktion. Dies kann durch die geringere Gitterspannung der Reaktionsprodukte erklärt werden. Die chemische Beschaffenheit des Substrats (Graphen oder SiO2) spielt dabei eine entscheidende Rolle.
Structural Snapshots for Mechanism‐Based Inactivation of a Glycoside Hydrolase by Cyclopropyl Carbasugars
Authors: Adamson Christopher , Pengelly Robert J. , Shamsi Kazem Abadi Saeideh , Chakladar Saswati , Draper Jason , Britton Robert , Gloster Tracey M. , Bennet Andrew J. 
Published: October 2016

AbstractGlycoside hydrolases (GHs) have attracted considerable attention as targets for therapeutic agents, and thus mechanism‐based inhibitors are of great interest. We report the first structural analysis of a carbocyclic mechanism‐based GH inactivator, the results of which show that the two Michaelis complexes are in 2H3 conformations. We also report the synthesis and reactivity of a fluorinated analogue and the structure of its covalently linked intermediate (flattened 2H3 half‐chair). We conclude that these inactivator reactions mainly involve motion of the pseudo‐anomeric carbon atom, knowledge that should stimulate the design of new transition‐state analogues for use as chemical biology tools.
Hydrogen‐Abstraction/Acetylene‐Addition Exposed
Authors: Yang Tao , Troy Tyler P. , Xu Bo , Kostko Oleg , Ahmed Musahid , Mebel Alexander M. , Kaiser Ralf I. 
Published: October 2016

AbstractPolycyclic aromatic hydrocarbons (PAHs) are omnipresent in the interstellar medium (ISM) and also in carbonaceous meteorites (CM) such as Murchison. However, the basic reaction routes leading to the formation of even the simplest PAH—naphthalene (C10H8)—via the hydrogen‐abstraction/acetylene‐addition (HACA) mechanism still remain ambiguous. Here, by revealing the uncharted fundamental chemistry of the styrenyl (C8H7) and the ortho‐vinylphenyl radicals (C8H7)—key transient species of the HACA mechanism—with acetylene (C2H2), we provide the first solid experimental evidence on the facile formation of naphthalene in a simulated combustion environment validating the previously postulated HACA mechanism for these two radicals. This study highlights, at the molecular level spanning combustion and astrochemistry, the importance of the HACA mechanism to the formation of the prototype PAH naphthalene.
Rich Athermal Ground‐State Chemistry Triggered by Dynamics through a Conical Intersection
Authors: Mignolet Benoit , Curchod Basile F. E. , Martínez Todd J. 
Published: October 2016

AbstractA fundamental tenet of statistical rate theories (such as transition state theory and RRKM) is the rapidity of vibrational relaxation. Excited‐state reactions happen quite quickly (sub‐picosecond) and thus can exhibit nonstatistical behavior. However, it is often thought that any diversity of photoproducts results from different conical intersections connecting the excited and ground electronic states. It is also conceivable that the large energy of the photon, which is converted to vibrational energy after electronic transitions could lead to athermal hot ground state reactions and that these might be responsible for the diversity of photoproducts. Here we show that this is the case for sulfines, where a single conical intersection is implicated in the electronic transition but the excited state reaction leads to nine different products within less than a picosecond.
Terminal‐Selective Functionalization of Alkyl Chains by Regioconvergent Cross‐Coupling
Authors: Dupuy Stéphanie , Zhang Ke‐Feng , Goutierre Anne‐Sophie , Baudoin Olivier 
Published: October 2016

AbstractHydrocarbons are still the most important precursors of functionalized organic molecules, which has stirred interest in the discovery of new C−H bond functionalization methods. We describe herein a new step‐economical approach that enables C−C bonds to be constructed at the terminal position of linear alkanes. First, we show that secondary alkyl bromides can undergo in situ conversion into alkyl zinc bromides and regioconvergent Negishi coupling with aryl or alkenyl triflates. The use of a suitable phosphine ligand favoring Pd migration enabled the selective formation of the linear cross‐coupling product. Subsequently, mixtures of secondary alkyl bromides were prepared from linear alkanes by standard bromination, and regioconvergent cross‐coupling then provided access to the corresponding linear arylation product in only two steps.
Pseudo‐Contact NMR Shifts over the Paramagnetic Metalloprotein CoMMP‐12 from First Principles
Authors: Benda Ladislav , Mareš Jiří , Ravera Enrico , Parigi Giacomo , Luchinat Claudio , Kaupp Martin , Vaara Juha 
Published: October 2016

AbstractLong‐range pseudo‐contact NMR shifts (PCSs) provide important restraints for the structure refinement of proteins when a paramagnetic metal center is present, either naturally or introduced artificially. Here we show that ab initio quantum‐chemical methods and a modern version of the Kurland–McGarvey approach for paramagnetic NMR (pNMR) shifts in the presence of zero‐field splitting (ZFS) together provide accurate predictions of all PCSs in a metalloprotein (high‐spin cobalt‐substituted MMP‐12 as a test case). Computations of 314 13C PCSs using g‐ and ZFS tensors based on multi‐reference methods provide a reliable bridge between EPR‐parameter‐ and susceptibility‐based pNMR formalisms. Due to the high sensitivity of PCSs to even small structural differences, local structures based either on X‐ray diffraction or on various DFT optimizations could be evaluated critically by comparing computed and experimental PCSs. Many DFT functionals provide insufficiently accurate structures. We also found the available 1RMZ PDB X‐ray structure to exhibit deficiencies related to binding of a hydroxamate inhibitor. This has led to a newly refined PDB structure for MMP‐12 (5LAB) that provides a more accurate coordination arrangement and PCSs.
cyclo‐P4 Building Blocks: Achieving Non‐Classical Fullerene Topology and Beyond
Authors: Dielmann Fabian , Peresypkina Eugenia V. , Krämer Barbara , Hastreiter Florian , Johnson Brian P. , Zabel Manfred , Heindl Claudia , Scheer Manfred 
Published: October 2016

AbstractThe cyclo‐P4 complexes [CpRTa(CO)2(η4‐P4)] (CpR: Cp′′=1,3‐C5H3tBu2, Cp′′′=1,2,4‐C5H2tBu3) turned out to be predestined for the formation of hollow spherical supramolecules with non‐classical fullerene‐like topology. The resulting assemblies constructed with CuX (X=Cl, Br) showed a highly symmetric 32‐vertex core of solely four‐ and six‐membered rings. In some supramolecules, the inner cavity was occupied by an additional CuX unit. On the other hand, using CuI, two different supramolecules with either peanut‐ or pear‐like shapes and outer diameters in the range of 2–2.5 nm were isolated. Furthermore, the spherical supramolecules containing Cp′′′ ligands at tantalum are soluble in CH2Cl2. NMR spectroscopic investigations in solution revealed the formation of isomeric supramolecules owing to the steric hindrance caused by the third tBu group on the Cp′′′ ligand. In addition, a 2D coordination polymer was obtained and structurally characterized.
Natural‐Product‐Inspired Aminoepoxybenzoquinones Kill Members of the Gram‐Negative Pathogen Salmonella by Attenuating Cellular Stress Response
Authors: Mandl Franziska A. , Kirsch Volker C. , Ugur Ilke , Kunold Elena , Vomacka Jan , Fetzer Christian , Schneider Sabine , Richter Klaus , Fuchs Thilo M. , Antes Iris , Sieber Stephan A. 
Published: October 2016

AbstractGram‐negative bacteria represent a challenging task for antibacterial drug discovery owing to their impermeable cell membrane and restricted uptake of small molecules. We herein describe the synthesis of natural‐product‐derived epoxycyclohexenones and explore their antibiotic activity against several pathogenic bacteria. A compound with activity against Salmonella Typhimurium was identified, and the target enzymes were unraveled by quantitative chemical proteomics. Importantly, two protein hits were linked to bacterial stress response, and corresponding assays revealed an elevated susceptibility to reactive oxygen species upon compound treatment. The consolidated inhibition of these targets provides a rationale for antibacterial activity and highlights epoxycyclohexenones as natural product scaffolds with suitable properties for killing Gram‐negative Salmonella.