Previous Assignments Research Articles

The backbone NMR resonance assignments of the stabilized E. coli β clamp.

The 81 kDa E. coli β clamp is a ring-shaped head-to-tail homodimer that encircles DNA and plays a central role in bacterial DNA replication by serving as a processivity factor for DNA polymerases and a binding platform for other DNA replication and repair proteins. Here we report the backbone 1H, 15N, and 13C NMR resonance assignments of the stabilized T45R/S107R β clamp variant obtained using standard TROSY-based triple-resonance experiments (BMRB 52548). The backbone assignments were aided by 13C and 15N edited NOESY experiments, allowing us to utilize our previously reported assignments of the β clamp ILV side-chain methyl groups (BMRB 51430, 51431). The backbone assignments of the T45R/S107R β clamp variant were transferred to the wild-type β clamp using a minimal set of TROSY-based 15N edited NOESY, NHCO and NHCA experiments (BMRB 52549). The reported backbone and previous ILV side-chain resonance assignments will enable NMR studies of the β clamp interactions and dynamics using amide and methyl groups as probes.

Observed kinetics for the production of diethyl carbonate from CO2 and ethanol catalyzed by CuNi nanoparticles supported on activated carbon

Monometallic and bimetallic Cu:Ni catalysts with different Cu:Ni molar ratios (3:1, 2:1, 1:1, 1:2, 1:3) were synthesized by wetness impregnation on activated carbon and characterized by TPR (temperature programmed reduction), XRD (X-ray diffraction) and XPS (X-ray photoelectron spectroscopy). The synthesized catalysts were evaluated in the gas phase production of diethyl carbonate from ethanol and carbon dioxide. The largest catalytic activity was obtained over the bimetallic catalyst with a Cu:Ni molar ratio of 3:1. Its improved activity was attributed to the formation of a Cu–Ni alloy on the surface of the catalyst, evidenced by XPS and in agreement with a previous assignment based on Vegard law and TPR analysis. During the reaction rate experiments, it observed the presence of a maximum of the reaction rate as a function of temperature, a tendency also reported for other carbon dioxide–alcohol reactions. It showed that the reaction rate-temperature data can be adjusted with a reversible rate equation. The initial rate as a function of reactant partial pressure data was satisfactorily adjusted using the forward power law rate equation and it was found that the reaction rate is first order in CO2 and second order in ethanol.

Elastic and Electronically Inelastic Cross Sections for the Scattering of Electrons by Pyrrole.

Integral and differential cross sections for elastic and electronically inelastic electron scattering from the pyrrole molecule are reported. The cross section calculations employed the Schwinger multichannel method with norm-conserving pseudopotentials. The collision dynamics was described according to a model in which up to 209 energetically accessible channels were treated as open. In the elastic channel, calculations carried out in the interval of energies from 0 to 50 eV revealed the presence of four resonances with peaks located at 2.56 eV (π1*), 3.82 eV (π2*), 4.70 eV (σNH*), and between 8.30 and 9.50 eV (σ*) positions which are in good agreement with previous assignments. Moreover, the role of the multichannel coupling effects in obtaining accurate cross sections was evaluated by comparing the present results with theoretical results recently reported in the literature and early measurements performed for elastic electron collisions with furan. Electronic excitation cross sections involving the transitions from ground state to the 13B2, 13A1, 11A2, and 11A1 excited states of pyrrole driven by electron impact are presented for energies from thresholds up to 50 eV and, whenever possible, critically compared with the data available in the literature.

Leveraging liminality: how the interim manager’s liminal position facilitates knowledge transfer to client organizations

Purpose With the rise of the gig economy, management positions are increasingly staffed with flexible labor, so-called interim managers. They plunge into organizations for a limited period, operating in a liminal position as partly insider, partly outsider. Although several contributions to their client organizations are acknowledged, it is unknown how the interim manager’s knowledge from previous assignments is made useful in the new context under these particular working conditions. Therefore, the purpose of this paper is to increase the understanding of how the interim manager’s knowledge is transferred to the client organization while operating from a liminal position. Design/methodology/approach This paper presents an interview-based multiple case study of six interim assignments where knowledge transfer is considered a social and context-dependent process. Findings The findings unveil the multifaceted nature of the liminal position, which consists of task orientation, time limitation, political detachment and cultural distance. These facets contribute to knowledge transfer in terms of new shared understandings and joint interests, which in turn might create new practices that augment continuous knowledge-sharing patterns. Originality/value The results contribute to the research on flexible work arrangements by shedding light on how the liminal position, predominantly depicted as an obstacle for the individual, might facilitate knowledge transfer. Through the process of knowledge generation, it is shown how a short-term engagement might enable the organization to increase its knowledge over time.

Morphometric analysis of the Late CretaceousPlacenticerasof Alabama, USA: sexual dimorphism, allometry, and implications for taxonomy

AbstractA traditional typological approach to taxonomy often does not adequately account for intraspecific variation and can result in taxonomic oversplitting. For many groups, including ammonoids of thePlacenticerasgenus, intraspecific variation documented in recent studies (e.g., ontogenetic changes, sexual dimorphism, polymorphism) challenges the historic proliferation of species names. Here, we used a population approach to taxonomy and quantitatively evaluated morphometric variation in a sample of Late Cretaceous (Santonian–Campanian)Placenticerasfrom Alabama and adjacent counties.We used linear mixed models (LMMs) to characterize how morphological variables scale with conch size across the sample, exploiting mixed longitudinal data to evaluate individual variation in growth and inform interpretations of multivariate analyses. Extended LMMs incorporating geological formation evaluated morphological changes through time. Principal component analysis and clustering analysis were then used to evaluate the number of distinct clusters that emerged in multivariate morphospace independent of previous taxon name assignments.Discontinuous scaling relationships and distinct clusters in multivariate space suggest sexual dimorphism characterized by differences in adult size and, secondarily, shape. PreviousStantonocerasandPlacenticerasassignments broadly overlap in our morphospace, failing to justify this historic distinction (as sexual dimorphs or as genera or subgenera).Placenticerasconch morphology and ornament placement changed through time, suggesting a potential utility for coarse (stage-level) biostratigraphy. However, temporal changes were not associated with distinct clusters in morphospace, and our data fail to support the plethora of reported species names. As few as one or two (successive) species may be present in our sample (representing 130 years of collection effort). In addition to highlighting the need for a significant taxonomic revision of thePlacenticerasgenus, this study demonstrates the utility of LMMs for distinguishing between different sources of morphological variation, improving interpretations of morphospace under a population approach to taxonomy, and maximizing the amount of ontogenetic information that can be obtained nondestructively.

Investigations on the defect structures for Mn2+ in CdSe nanocrystals and bulk materials and the criterion of occupation for Mn2+ in CdX (X = S, Se, Te) nanocrystals.

The spin Hamiltonian parameters and defect structures are theoretically studied for the substitutional Mn2+ at the core of CdSe nanocrystals and in the bulk materials from the perturbation calculations of spin Hamiltonian parameters for trigonal tetrahedral 3d5 clusters. Both the crystal-field and charge transfer contributions are taken into account in the calculations from the cluster approach. The impurity-ligand bond angles are found to be about 1.84° larger and 0.10° smaller in the CdSe:Mn2+ nanocrystals and bulk materials, respectively, than those (≈109.37°) of the host Cd2+ sites. The quantitative criterion of occupation (at the core or surface) for Mn2+ in CdX (X = S, Se, Te) nanocrystals is presented for the first time based on the inequations of hyperfine structure constants (HSCs). This criterion is well supported by the experimental HSCs data of Mn2+ in CdX nanocrystals. The previous assignments of signals SI as Mn2+ at the core of CdS nanocrystals are renewed as Mn2+ at the surface based on the above criterion. The present studies would be helpful to achieve convenient determination of occupation for Mn2+ impurities in CdX semiconductor nanocrystals by means of spectral (e.g., HSCs) analysis.

Computational Protocol for the Spectral Assignment of NMR Resonances in Covalent Organic Frameworks.

Solid-state nuclear magnetic resonance spectroscopy is routinely used in the field of covalent organic frameworks to elucidate or confirm the structure of the synthesized samples and to understand dynamic phenomena. Typically this involves the interpretation and simulation of the spectra through the assumption of symmetry elements of the building units, hinging on the correct assignment of each line shape. To avoid misinterpretation resulting from library-based assignment without a theoretical basis incorporating the impact of the framework, this work proposes a first-principles computational protocol for the assignment of experimental spectra, which exploits the symmetry of the underlying building blocks for computational feasibility. In this way, this protocol accommodates the validation of previous experimental assignments and can serve to complement new NMR measurements.

Conformational Mapping, Interactions, and Fluorine Impact by Combined Spectroscopic Approaches and Quantum Chemical Calculations.

Noncovalent interactions and their careful variation can be crucial in understanding molecular structures, conformational topographies, and properties. Here, we examine the fluorination impact on the structure and conformational behavior of 2-(2-fluorophenyl)ethyl alcohol (2-FPEAL) by monitoring the first individual ionization-loss-stimulated Raman spectra of the jet-cooled molecule. The comparison of two different broad-range spectra and predicted equivalents discloses two distinct structures. One possesses a folded side chain (gauche) and the other an extended chain (anti) with the terminal hydrogen atom pointing opposite or toward the fluorine side, indicating the improper previous tentative assignment of the latter. These conformers resemble and differ from the nonfluorinated analogue structures. Theoretical analyses reveal interconversion pathways of 2-FPEAL conformers during expansion and the delicate balance between attractive (C-H···F and O-H···π) and repulsive interactions. These findings show the achievements of our integrated approach, suggesting its potential for overcoming future structural challenges.

The geology of Sierra Calderona (SE Iberian Cordillera, Spain), a review. Results of a new 1:25.000 scale geological mapping

ABSTRACT A new geological mapping of Sierra Calderona (SE Iberian Cordillera) has confirmed the widespread presence of the Muschelkalk M2 unit overlying a ubiquitous Muschelkalk M1 carbonate unit. Thus, the allocation of this range in the Levantine-Balearic Triassic Domain is not justified and a previous assignment of the entire Muschelkalk carbonate succession of this region to the M3 unit is untenable. Evidence of Permo-Triassic extensional tectonics by local unconformities separating Permian and Triassic units and a more widespread unconformity at the base of the Jurassic succession is recorded. Paleogene-Early Neogene compression-related structures associated with the formation of the NW-SE trending Sierra Calderona anticlinorium are scarce, but numerous detachment surfaces within the stratigraphic pile suggest a complex thick-skinned tectonics. The dominant tectonic grain in Sierra Calderona is a Neogene extensional structure with a preferential pattern of blocks stepping down to the coast, which is related to the opening of the Valencia Trough.

The trilobite assemblage of the Declivolithus Fauna (lower Katian, Ordovician) of Morocco: a review with new data

Abstract Intense commercial exploitation of fossils in the famous El Qaid Errami area in the last 20 years has led to the discovery of the interesting Declivolithus Fauna in the Moroccan Anti-Atlas. This unusually large trinucleid trilobite, described originally from the Czech Republic, is the most conspicuous element of an assemblage mainly occurring in the Bofloss locality, a local biofacies development of pelagic mudstones and sandstones cropping out in a structurally isolated place in the Tizi n'Ounfite area. Here we revise this Declivolithus Fauna trilobite assemblage from Morocco, increasing the known trilobite diversity from four to 11 species: Ulugtella? biformis n. sp., Selenopeltis cf. S. vultuosa, Phacopidina quadrata, Eudolatites cf. E. bondoni, Prionocheilus cf. P. verneuili, Nobiliasaphus cf. N. kumatox, Cyclopyge cf. C. rediviva, Symphysops stevaninae, Heterocyclopyge sp., Dionide sp., and Declivolithus alfredi. The new data and the very good preservation of specimens in sandstones, clarify the specific identity of previously reported taxa. Although the stratigraphical correlation of the fossiliferous levels remains problematic, it probably corresponds to the upper part of the Lower Ktaoua Formation or to the lower half of the Upper Tiouririne Formation. Most taxa support previous assignment of the Moroccan assemblage to the late Berounian (ca. early Katian, Ka2), although a middle Berounian (ca. Sa2–Ka1) age cannot be excluded. Most of the identified species are known from the Czech Republic (eight out of 11), showing that the strong faunal link between Morocco and the Czech Republic still existed during the Late Ordovician, being stronger than the link with the coeval Ibero-Armorican domain faunas. UUID: http://zoobank.org/3e6e55c7-168d-4008-98ba-38a795581ca3

Dual nomenclature in organic-walled dinoflagellate cysts II: Spiniferites elongatus and S. membranaceus, and their equivalent non-fossil species Gonyaulax ovum comb. nov. and G. lewisiae sp. nov.

The cyst-defined extant Spiniferites elongatus Reid 1974 and Spiniferites membranaceus (Rossignol 1964) Sarjeant 1970 are environmentally significant fossil-species of the Quaternary, the former often dominating polar and subpolar assemblages. Following cyst incubation experiments and the establishment of cultures, these species were emended to incorporate information on their motile stages, and transferred to the non-fossil genus Gonyaulax Diesing 1866, as Gonyaulax elongata (Reid 1974) Ellegaard et al. 2003 and Gonyaulax membranacea (Rossignol 1964) Ellegaard et al. 2003. This unified approach to dinoflagellate nomenclature severs an important link with the fossil-genus Spiniferites Mantell 1850. We have applied dual nomenclature, as sanctioned by the International Code of Nomenclature for algae, fungi and plants, in returning these species to their previous assignments as Spiniferites elongatus and Spiniferites membranaceus, and we propose Gonyaulax ovum (Gaarder 1954) comb. nov., emend. and Gonyaulax lewisiae sp. nov., respectively, as their equivalent non-fossil species. A distinctive morphotype initially described as Rottnestia amphicavata var. amphicavata Dobell & Norris in Harland et al. 1980 is proposed as Spiniferites elongatus forma amphicavata stat. nov.

Access to long-lived room temperature phosphorescence through auration of 2,1,3-benzothiadiazole.

A series of 2,1,3-benzothiadiazole-Au(I)-L complexes have been synthesised, structurally characterised and investigated for their photophysical properties. These are the first organometallic Au(I) complexes containing a C-Au bond on the highly electron-deficient benzothiadiazole unit. The complexes exhibit solution-phase phosphorescence at room temperature, assigned to the intrinsic triplet state of the benzothiadiazole unit that is efficently populated through its attachment to gold. Comparison with routinely reported Au(I) complexes, which include intervening alkenyl linkers, suggests that previous assignments of their phosphorescence as 1π → π*(CCR) might be incomplete. Our observations affirm that, in addition to the heavy atom effect, breaking symmetry in the involved aryl motif may be of importance in controlling the luminescence properties.

Chilotherium schlosseri (Weber, 1905) (Rhinocerotidae, Mammalia) from the late Miocene of the foreland of the Eastern Carpathians in Romania

The paper provides an overview of the Chilotherium Ringström, 1924 fossils from Romania, which are recorded so far in three different Upper Miocene localities of the Eastern Carpathians Foreland: mammal localities of Reghiu, Bacău and Pogana. The fossils include a partial skull, several maxillary and mandible fragments and isolated teeth. They have been partially illustrated, but never described excepting the isolated teeth of Pogana. The previous assignments were confusing, ranging from Chilotherium schlosseri (Weber, 1905) and C. cf. sarmaticum for Reghiu specimens to an indeterminate species close to C. sarmaticum Korotkevich, 1958, C. kiliasi (Geraads & Koufos, 1990), and C. kowalevskii (Pavlow, 1913) for Pogana teeth. Based on descriptions and comparisons with other Chilotherium remains, all specimens from Romania can be referred to C. schlosseri. Chilotherium schlosseri is the most widespread species of the genus, ranging from Eastern Europe to Central Asia. The presence of this genus in Romania, and more globally in Eastern Europe, attests to a transition area between the more closed and wooded environments of Western Europe (where Chilotherium is absent) to the more open ones in Asia.

Reassigning CI chondrite parent bodies based on reflectance spectroscopy of samples from carbonaceous asteroid Ryugu and meteorites.

The carbonaceous asteroid Ryugu has been explored by the Hayabusa2 spacecraft to elucidate the actual nature of hydrous asteroids. Laboratory analyses revealed that the samples from Ryugu are comparable to unheated CI carbonaceous chondrites; however, reflectance spectra of Ryugu samples and CIs do not coincide. Here, we demonstrate that Ryugu sample spectra are reproduced by heating Orgueil CI chondrite at 300°C under reducing conditions, which caused dehydration of terrestrial weathering products and reduction of iron in phyllosilicates. Terrestrial weathering of CIs accounts for the spectral differences between Ryugu sample and CIs, which is more severe than space weathering that likely explains those between asteroid Ryugu and the collected samples. Previous assignments of CI chondrite parent bodies, i.e., chemically most primitive objects in the solar system, are based on the spectra of CI chondrites. This study indicates that actual spectra of CI parent bodies are much darker and flatter at ultraviolet to visible wavelengths than the spectra of CI chondrites.

Exploring Personalized Learning and Open Education Pedagogy in Multilingual Learner Teacher Preparation

Preparation to serve multilingual learners is often required for P-12 teacher certification. Teachers come to this preparation with varied experiences and urgent needs to better serve their students. When teacher preparation courses use a one-size-fits-all approach to satisfy certification requirements, teachers may not find learning meaningful to their current context. Further, without common mechanisms for sharing resources produced through teacher preparation, each novice teacher starts assignments from the beginning rather than learning from, and building upon, previous assignments of peers. Reusable teacher preparation assignments through open education pedagogy (OEP) may address the challenges of providing collaborative, relevant, and optimally challenging state-mandated teacher preparation. However, personalized learning may not be aligned with university course evaluations. Thus, faculty members may be concerned about the impact of personalization on student course evaluations. This exploratory study examined personalization and OEP in a required, graduate-level teacher preparation course by analyzing assignment completion data to explore teacher personalized learning paths and comparing standard university course evaluation items from four course runs pre- and post-personalization (N=230). Descriptive analyses illustrate negative changes in teacher evaluation of course organization, feedback timeliness, and time spent outside of class. Teacher satisfaction increased in the areas of diversity, use of technology, access, and online discussions. Results from examining personalized paths and course satisfaction provide recommendations for designing personalized teacher preparation.

Taxonomy, biostratigraphy and paleobiogeography of Strenuaeva (Trilobita) from the Marianian (Cambrian Series 2) of Iberia

Problems surrounding the identification and systematics of taxa belonging to the trilobite family Ellipsocephalidae have been discussed for several decades. The ellipsocephalid genus Strenuaeva is revised herein on the basis of material from Spain, including the type material of the identified species together with newly collected specimens from the Ossa-Morena Zone and the Iberian Chains. Two species are recognized as valid for these regions: S. sampelayoi and S. incondita. The species ‘S. melendezi’ and ‘Ellipsostrenua alanisiana’ from Spain, as well as ‘S. marocana’ from Morocco, are considered junior synonyms of S. sampelayoi. Previous assignment of the Spanish species to Issafeniella is rejected. The abundant available material of S. sampelayoi made it possible to evaluate the taphonomical role in the preservation of some characters and to recognize intraspecific variability similar to that described in S. inflata from Baltica, reinforcing its assignment to Strenuaeva. Biostratigraphically, Strenuaeva ranges from uppermost Cambrian Stage 3 to uppermost Cambrian Stage 4. In Iberia, it is restricted to the middle Marianian in the Ossa-Morena Zone, whereas it is known from the lowermost middle Marianian to the lowermost upper Marianian in the Iberian Chains. Strenuaeva is known from Baltica (Scandinavia and Holy Cross Mountains, Poland), Iberia (Spain), Morocco and, possibly, western Avalonia (Newfoundland), hence being a characteristic genus of the Acadobaltic faunal Province.

Gaussian process-based storage location assignments with risk assessments for progressive zone picking systems

E-commerce warehouses are under constant pressure to adapt their order picking systems and reassign product storage locations to meet fluctuating customer demands. Most existing approaches optimize storage location reassignments based on customer orders and operational configurations to maintain high order picking performance. This paper presents a Gaussian process surrogate model (GPSM) approach to predict the performance metrics for storage location reassignments. The GPSM estimates the expected flow time of orders from the historical data on previous storage location assignments and aids in identifying the new assignments that yield the minimum estimated average flow times. Management can also take advantage of the GPSM’s uncertainty quantification capability to assess the probability of improvement for a given storage reassignment and its implementation. The proposed model and assignment policy are validated using discrete-event simulations and industrial data. Experimental results demonstrate that the GPSM can improve expected flow time by 7.51% and reduce unnecessary reassignment operations by 43.25%.

Vibrational Properties of the Potassium Titanyl Phosphate Crystal Family

The crystal family of potassium titanyl phosphate (KTiOPO4) is a promising material group for applications in quantum and nonlinear optics. The fabrication of low-loss optical waveguides, as well as high-grade periodically poled ferroelectric domain structures, requires a profound understanding of the material properties and crystal structure. In this regard, Raman spectroscopy offers the possibility to study and visualize domain structures, strain, defects, and the local stoichiometry, which are all factors impacting device performance. However, the accurate interpretation of Raman spectra and their changes with respect to extrinsic and intrinsic defects requires a thorough assignment of the Raman modes to their respective crystal features, which to date is only partly conducted based on phenomenological modelling. To address this issue, we calculated the phonon spectra of potassium titanyl phosphate and the related compounds rubidium titanyl phosphate (RbTiOPO4) and potassium titanyl arsenate (KTiOAsO4) based on density functional theory and compared them with experimental data. Overall, this allows us to assign various spectral features to eigenmodes of lattice substructures with improved detail compared to previous assignments. Nevertheless, the analysis also shows that not all features of the spectra can unambigiously be explained yet. A possible explanation might be that defects or long range fields not included in the modeling play a crucial rule for the resulting Raman spectrum. In conclusion, this work provides an improved foundation into the vibrational properties in the KTiOPO4 material family.

Investigations of the structures of the Ru isotopes: 98Ru

As part of a systematic study of the nuclear structure of the Ru isotopes, 98Ru was investigated via the β-decay of 98Rh at iThemba LABS, and the 100Ru(p, t) reaction at the Maier-Leibnitz Laboratory. The combined data results in significant revision of the previous spin assignments and clarification of the nature of levels in 98Ru, as well as providing insights into the evolution of the structures across the Ru isotopic chain.

Anharmonic Assignment of the Water Octamer Spectrum in the OH Stretch Region.

We interface the quasi-classical trajectory approach with an ab initio potential energy surface for water to assign the vibrational spectroscopical features of the OH stretch region of the water octamer cluster, which is considered to be a precursor of ice. An attempt by Li et al. to assign their recent reference experiment involved lower-level calculations based on an ad hoc scaled harmonic approach. Differently from the conclusions of this previous assignment, which invoked the contribution of 5 conformers and a solvated form of the water heptamer in the spectrum, we find out that the spectroscopic features can be related to the 4 conformers of the octamer lying lower in energy.