bluuebunny/crossref_metadata_2025 huggingface dataset:
A single exposure to altered auditory feedback causes observable sensorimotor adaptation in speech
Authors: Hantzsch Lana , Parrell Benjamin , Niziolek Caroline A.
Published: July 2021

Sensory errors caused by perturbations to movement-related feedback induce two types of behavioral changes that oppose the perturbation: rapid compensation within a movement, as well as longer-term adaptation of subsequent movements. Although adaptation is hypothesized to occur whenever a sensory error is perceived (including after a single exposure to altered feedback), adaptation of articulatory movements in speech has only been observed after repetitive exposure to auditory perturbations, questioning both current theories of speech sensorimotor adaptation as well as the universality of more general theories of adaptation. Thus, positive evidence for the hypothesized single-exposure or “one-shot” learning would provide critical support for current theories of speech sensorimotor learning and control and align adaptation in speech more closely with other motor domains. We measured one-shot learning in a large dataset in which participants were exposed to intermittent, unpredictable auditory perturbations to their vowel formants (the resonant frequencies of the vocal tract that distinguish between different vowels). On each trial, participants spoke a word out loud while their first formant was shifted up, shifted down, or remained unshifted. We examined whether the perturbation on a given trial affected speech on the subsequent, unperturbed trial. We found that participants adjusted their first formant in the opposite direction of the preceding shift, demonstrating that learning occurs even after a single auditory perturbation as predicted by current theories of sensorimotor adaptation. While adaptation and the preceding compensation responses were correlated, this was largely due to differences across individuals rather than within-participant variation from trial to trial. These findings are more consistent with theories that hypothesize adaptation is driven directly by updates to internal control models than those that suggest adaptation results from incorporation of feedback responses from previous productions.
TCF12 controls oligodendroglial cell proliferation and regulates signaling pathways conserved in gliomas
Authors: Archontidi Sofia , Marie Corentine , Gyorgy Beata , Guegan Justine , Sanson Marc , Parras Carlos , Huillard Emmanuelle
Published: July 2021

Diffuse gliomas are primary brain tumors originating from the transformation of glial cells. In particular, oligodendrocyte precursor cells constitute the major tumor-amplifying population in the gliomagenic process. We previously identified the TCF12 gene, encoding a transcription factor of the E protein family, as being recurrently mutated in oligodendrogliomas. In this study, we sought to understand the function of TCF12 in oligodendroglial cells, the glioma lineage of origin. We first describe TCF12 mRNA and protein expression pattern in oligodendroglial development in the mouse brain. Second, by TCF12 genome wide chromatin profiling in oligodendroglial cells, we show that TCF12 binds active promoters of genes involved in proliferation, translation/ribosomes, and pathways involved in oligodendrocyte development and cancer. Finally, we perform OPC-specific Tcf12 inactivation in vivo and demonstrate by immunofluorescence and transcriptomic analyses that TCF12 is transiently required for OPC proliferation but dispensable for oligodendrocyte differentiation. We further show that Tcf12 inactivation results in deregulation of biological processes that are also altered in oligodendrogliomas. Together, our data suggest that TCF12 directly regulates transcriptional programs in oligodendroglia development that are relevant in a glioma context.
Longitudinal single-cell chemical imaging of engineered strains reveals heterogeneity in fatty acid production
Authors: Tague Nathan , Lin Haonan , Lugagne Jean-Baptiste , O’Connor Owen M. , Burman Deeya , Wong Wilson W. , Cheng Ji-Xin , Dunlop Mary J.
Published: July 2021

Understanding metabolic heterogeneity is critical for optimizing microbial production of valuable chemicals, but requires tools that can quantify metabolites at the single-cell level over time. Here, we develop longitudinal hyperspectral stimulated Raman scattering (SRS) chemical imaging to directly visualize free fatty acids in engineered Escherichia coli over many cell cycles. We also develop compositional analysis to determine the chain length and unsaturation of the fatty acids in living cells. Our method reveals substantial heterogeneity in fatty acid production among and within colonies that emerges over the course of many generations. Interestingly, the strains display distinct types of production heterogeneity in an enzyme-dependent manner. By pairing time-lapse and SRS imaging, we examine the relationship between growth and production at the single-cell level. Single-cell quantification does not show a significant growth-production tradeoff in a strain that exhibits high production heterogeneity. Our results demonstrate that cell-to-cell production heterogeneity is pervasive and provide a means to link single-cell and population-level production.
Cognitive process modeling addresses context independence violations in the ABCD Study stop-signal task
Authors: Weigard Alexander , Matzke Dora , Tanis Charlotte , Heathcote Andrew
Published: July 2021

The Adolescent Brain Cognitive Development (ABCD) Study is a longitudinal neuroimaging study of unprecedented scale that is in the process of following over 11,000 youth from middle childhood though age 20. However, a design feature of the study’s stop-signal task violates “context independence”, an assumption critical to current non-parametric methods for estimating stop-signal reaction time (SSRT), a key measure of inhibitory ability in the study. This has led some experts to call for the task to be changed and for previously collected data to be used with caution. We present a formal cognitive process model, the BEESTS-ABCD model, that provides a mechanistic explanation for the impact of this design feature, describes key behavioral trends in the ABCD data, and allows biases in SSRT estimates resulting from context independence violations to be quantified. We use the model to demonstrate that, although non-parametric SSRT estimates generally preserve the rank ordering of participants’ SSRT values, failing to account for context independence violations can lead to erroneous inferences in several realistic scenarios. Nonetheless, as the BEESTS-ABCD model can be used to accurately recover estimates of SSRT and other mechanistic parameters of interest from ABCD data, the impact of such violations can be effectively mitigated.
Elucidation of SARS-Cov-2 Budding Mechanisms Through Molecular Dynamics Simulations of M and E Protein Complexes
Authors: Collins Logan Thrasher , Elkholy Tamer , Mubin Shafat , Hill David , Williams Ricky , Ezike Kayode , Singhal Ankush
Published: July 2021

SARS-CoV-2 and other coronaviruses pose major threats to global health, yet computational efforts to understand them have largely overlooked the process of budding, a key part of the coronavirus life cycle. When expressed together, coronavirus M and E proteins are sufficient to facilitate budding into the ER-Golgi intermediate compartment (ERGIC). To help elucidate budding, we ran atomistic molecular dynamics (MD) simulations using the Feig laboratory’s refined structural models of the SARS-CoV-2 M protein dimer and E protein pentamer. Our MD simulations consisted of M protein dimers and E protein pentamers in patches of membrane. By examining where these proteins induced membrane curvature in silico, we obtained insights around how the budding process may occur. Multiple M protein dimers acted together to induce global membrane curvature through protein-lipid interactions while E protein pentamers kept the membrane planar. These results could eventually help guide development of antiviral therapeutics which inhibit coronavirus budding.
Molecular mechanism of the anti-lung cancer effect of Jin Ning Fang based on network pharmacology and experimental verification
Authors: Wu Chunxiao , Yu Qiquan , Shou Weizhen , Zhang Kun , Li Yang , Guo Wentao , Bao Qi
Published: July 2021

Background

Jin Ning Fang (JNF) is widely used as an adjuvant therapy for lung cancer. However, its molecular mechanism against lung cancer is still unclear.

Methods

The chemical compounds JNF were screened from the TCMSP database and its target proteins were then predicted. The genes related to lung cancer were collected from the CTD and DisGeNET databases. Next, targets were integrated with disease-related genes to obtain candidate genes. Functional enrichment and protein-protein interaction (PPI) analysis were also performed, followed by construction of pharmacological network. Meanwhile, Autodock was used to assess the affinity between targets and compound. Finally, the anti-cancer effect of JNF on lung cancer cells was detected and some predicted key genes was validated by using real-time PCR.

Results

Twenty-five overlapping targets were obtained, and pathway analysis showed that JNF might exert its anti-cancer function by regulating some biological pathways, such as apoptosis pathway. PPI and pharmacological network revealed several core targets (such as AKT1, AR, and ESR1) and three compounds (quercetin, calcium carbonate, and beta-sitosterol). Then, beta-sitosterol had a high affinity with AKT1, AR, and ESR1. Further in vitro experiments confirmed that JNF could inhibit proliferation and promote apoptosis of A549 cells. The expression of FDPS, PIM1, VCAM1, SLC29A1, NQO1, and ESR1 were significantly decreased, while mRNA level of AR and ANPEP were markedly increased after JNF treatment.

Conclusion

JNF may exert anti-lung cancer effect through multiple targets and pathways, and identified genes may be used as potential biomarkers for diagnosis and treatment of lung cancer.
Deep Learning Image Classification of Red Blood Cell Deformability
Authors: Lamoureux Erik S. , Islamzada Emel , Wiens Matthew V. J. , Matthews Kerryn , Duffy Simon P. , Ma Hongshen
Published: July 2021

Red blood cells (RBCs) must be highly deformable to transit through the microvasculature to deliver oxygen to tissues. The loss of RBC deformability resulting from pathology, natural aging, or storage in blood bags can impede the proper function of these cells. A variety of methods have been developed to measure RBC deformability, but these methods require specialized equipment, long measurement time, and highly skilled personnel. To address this challenge, we investigated whether a machine learning approach could be applied to determine donor RBC deformability using single cell microscope images. We used the microfluidic ratchet device to sort RBCs based on deformability. Sorted cells are then imaged and used to train a deep learning model to classify RBCs based on deformability. This model correctly predicted deformability of individual RBCs with 84 ± 11% accuracy averaged across ten donors. Using this model to score the deformability of RBC samples were accurate to within 4.4 ± 2.5% of the value obtained using the microfluidic ratchet device. While machine learning methods are frequently developed to automate human image analysis, our study is remarkable in showing that deep learning of single cell microscopy images could be used to measure RBC deformability, a property not normally measurable by imaging. Measuring RBC deformability by imaging is also desirable because it can be performed rapidly using a standard microscopy system, potentially enabling RBC deformability studies to be performed as part of routine clinical assessments.
Genetic loci of theR. anatipestiferserotype discovered by Pan-GWAS and its application for the development of a multiplex PCR serotyping method
Authors: Yang Zhishuang , Yang Xueqin , Wang Mingshu , Jia Renyong , Chen Shun , Liu Mafeng , Zhao Xinxin , Yang Qiao , Wu Ying , Zhang Shaqiu , Huang Juan , Ou Xumin , Mao Sai , Gao Qun , Sun Di , Tian Bin , Zhu Dekang , Cheng Anchun
Published: July 2021

The disease caused byRiemerella anatipestifer(R. anatipestifer) causes large economic losses to the global duck industry every year. Serotype-related genomic variation (such as in O-antigen and capsular polysaccharide gene clusters) has been widely used for the serotyping in many gram-negative bacteria. To date, there have been few studies focused on genetic basis of serotypes inR. anatipestifer. Here, we used pan-genome-wide association studies (Pan-GWAS) to identify the serotype-specific genetic loci of 38R. anatipestifersstrain. Analyses of the loci of 11 serotypes showed that the loci could be well mapped with the serotypes of the corresponding strains. We constructed the knockout strain for thewzygene at the locus, and the results showed that the mutant lost the agglutination characteristics to positive antisera. Based on the of Pan-GWAS results, we developed a multiple PCR method to identify serotypes 1, 2, and 11 ofR. anatipestifer. Our study provides a precedent for systematically analysing the genetic basis of theR anatipestiferserotypes and establishing a complete serotyping system in the future.

Highlights

R. anatipestiferserotype-specific locus was identified by Pan-GWAS for the first time.

Molecular serotyping multiplex PCR was developed based on O-antigen biosynthesis gene clusters
Engineering Viral Vectors for Acoustically Targeted Gene Delivery
Authors: Li Hongyi , Heath John E. , Trippett James S. , Shapiro Mikhail G. , Szablowski Jerzy O.
Published: July 2021

Targeted gene delivery to the brain is a critical tool for neuroscience research and has significant potential to treat human disease. However, the site-specific delivery of common gene vectors such as adeno-associated viruses (AAVs) is typically performed via invasive injections, limiting their scope of research and clinical applications. Alternatively, focused ultrasound blood-brain-barrier opening (FUS-BBBO), performed noninvasively, enables the site-specific entry of AAVs into the brain from systemic circulation. However, when used in conjunction with natural AAV serotypes, this approach has limited transduction efficiency, requires ultrasound parameters close to tissue damage limits, and results in undesirable transduction of peripheral organs. Here, we use high throughput in vivo selection to engineer new AAV vectors specifically designed for local neuronal transduction at the site of FUS-BBBO. The resulting vectors substantially enhance ultrasound-targeted gene delivery and neuronal tropism while reducing peripheral transduction, providing a more than ten-fold improvement in targeting specificity. In addition to enhancing the only known approach to noninvasively target gene delivery to specific brain regions, these results establish the ability of AAV vectors to be evolved for specific physical delivery mechanisms.
Nociceptor subtypes are born continuously over DRG development peaking at E10.5—E11.5
Authors: Landy Mark A. , Goyal Megan , Lai Helen C.
Published: July 2021

Sensory neurogenesis in the dorsal root ganglion (DRG) occurs in two waves of differentiation with larger, myelinated proprioceptive and low-threshold mechanoreceptor (LTMR) neurons differentiating before smaller, unmyelinated (C) nociceptive neurons. This temporal difference was established from early birthdating studies based on DRG soma cell size. However, distinctions in birthdates between molecular subtypes of sensory neurons, particularly nociceptors, is unknown. Here, we assess the birthdate of lumbar DRG neurons in mice using a thymidine analog, EdU, to label developing neurons exiting mitosis combined with co-labeling of known sensory neuron markers. We find that different nociceptor subtypes are born on similar timescales, with continuous births between E9.5 to E13.5, and peak births from E10.5 to E11.5. Notably, we find that thinly myelinated Aδ-fiber nociceptors and peptidergic C-fibers are born more broadly between E10.5 and E11.5 than previously thought and that non-peptidergic C-fibers and C-LTMRs are born with a peak birth date of E11.5. Moreover, we find that the percentages of nociceptor subtypes born at a particular timepoint are the same for any given nociceptor cell type marker, indicating that intrinsic or extrinsic influences on cell type diversity are occurring similarly across developmental time. Overall, the patterns of birth still fit within the classical “two wave” description, as touch and proprioceptive fibers are born primarily at E10.5, but suggest that nociceptors have a slightly broader wave of birthdates with different nociceptor subtypes continually differentiating throughout sensory neurogenesis irrespective of myelination.
A mutation in the promoter of the pmrD gene of Shigella flexneri abrogates functional PhoPQ-PmrD-PmrAB signaling and polymyxin B resistance
Authors: Huynh Raymond , McPhee Joseph B.
Published: July 2021

Shigella spp. are the causative agent of bacillary dysentery, a major cause of food-borne morbidity and mortality worldwide. These organisms are recently evolved, polyphyletic pathovar of E. coli, and since their divergence they have undergone multiple cases of gene gain and gene loss and understanding how gene inactivation events alter bacterial behaviour represents an important objective to be better able to understand how virulence and other phenotypes are affected. Here, we identify a frameshift mutation in the pmrD gene of S. flexneri that although it would be predicted to make a functional, full-length protein, no such production occurs, likely due to the non-optimal spacing between the translational initiation site and the Shine-Dalgarno sequence. We show that this loss severs the normal connection between the PhoPQ two-component regulatory system and the PmrAB two-component regulatory system, abrogating low Mg2+ mediated cationic antimicrobial peptide and polymyxin B resistance, while maintaining normal PmrAB-mediated polymyxin B resistance. In contrast, S. sonnei maintains a functional PmrD protein and canonical signaling through this regulatory network. This species specific gene loss suggests that S. flexneri and S. sonnei have evolved different regulatory responses to changing environmental conditions.
Individual repeatability, species differences, and the influence of socio-ecological factors on neophobia in 10 corvid species
Authors: Miller Rachael , Lambert Megan L. , Frohnwieser Anna , Brecht Katharina F. , Bugnyar Thomas , Crampton Isabelle , Garcia-Pelegrin Elias , Gould Kristy , Greggor Alison L. , Izawa Ei-Ichi , Kelly Debbie M. , Li Zhongqiu , Luo Yunchao , Luong Linh B. , Massen Jorg J.M. , Nieder Andreas , Reber Stephan A. , Schiestl Martina , Seguchi Akiko , Sepehri Parisa , Stevens Jeffrey R. , Taylor Alexander H. , Wang Lin , Wolff London M. , Zhang Yigui , Clayton Nicola S.
Published: July 2021

Behavioural responses to novelty, including fear and subsequent avoidance of novel stimuli, behaviours referred to as neophobia, determine how animals interact with their environment. Neophobia aids in navigating risk and impacts on adaptability and survival. There is variation within and between individuals and species, however, lack of large-scale, comparative studies critically limits investigation of the socio-ecological drivers of neophobia. In this study, we tested responses to novel objects and food (alongside familiar food) versus a baseline (familiar food alone) in 10 corvid species (241 subjects) across 10 labs worldwide. There were species differences in the latency to touch familiar food in the novel object and food conditions relative to the baseline. Three of seven socio-ecological factors influenced object neophobia: 1) use of urban habitat (vs not), 2) territorial pair vs family group sociality and 3) large vs small flock size (whereas range, caching, hunting live animals, and genus did not); while only flock size influenced food neophobia. We found that, overall, individuals were temporally and contextually repeatable (i.e. consistent) in their novelty responses in all conditions, indicating neophobia is a stable behavioural trait. With this study, we have established a network of corvid researchers, demonstrating potential for further collaboration to explore the evolution of cognition in corvids and other bird species. These novel findings enable us, for the first time in corvids, to identify the socio-ecological correlates of neophobia and grant insight into specific elements that drive higher neophobic responses in this avian family group.
Parental origin of Gsα inactivation differentially affects bone remodeling in a mouse model of Albright hereditary osteodystrophy
Authors: McMullan Patrick , Maye Peter , Yang Qingfen , Rowe David W. , Germain-Lee Emily L.
Published: July 2021

Albright hereditary osteodystrophy (AHO) is caused by heterozygous inactivation of GNAS, a complex locus that encodes the alpha-stimulatory subunit of GPCRs (Gsα) in addition to NESP55 and XLαs due to alternative first exons. AHO skeletal manifestations include brachydactyly, brachymetacarpia, compromised adult stature, and subcutaneous ossifications. AHO patients with maternally-inherited GNAS mutations develop pseudohypoparathyroidism type 1A (PHP1A) with resistance to multiple hormones that mediate their actions through GPCRs requiring Gsα (eg., PTH, TSH, GHRH, calcitonin) and severe obesity. Paternally-inherited GNAS mutations cause pseudopseudohypoparathyroidism (PPHP), in which patients have AHO skeletal features but do not develop hormonal resistance or marked obesity. These differences between PHP1A and PPHP are caused by tissue-specific reduction of paternal Gsα expression. Previous reports in mice have shown loss of Gsα causes osteopenia due to impaired osteoblast number and function and suggest AHO patients could display evidence of reduced bone mineral density (BMD). However, we previously demonstrated PHP1A patients display normal-increased BMD measurements without any correlation to body mass index or serum PTH. Due to these observed differences between PHP1A and PPHP, we utilized our laboratory’s AHO mouse model to address whether Gsα heterozygous inactivation by the targeted disruption of exon 1 of Gnas differentially affects bone remodeling based on the parental inheritance of the mutation. Mice with paternally-inherited (GnasE1+/−p) and maternally-inherited (GnasE1+/−m) mutations displayed reductions in osteoblasts along the bone surface compared to wildtype. GnasE1+/−p mice displayed reduced cortical and trabecular bone parameters due to impaired bone formation and excessive bone resorption. GnasE1+/−m mice however displayed enhanced bone parameters due to increased osteoblast activity and normal bone resorption. These distinctions in bone remodeling between GnasE1+/−p and GnasE1+/−m mice appear to be secondary to changes in the bone microenvironment driven by calcitonin-resistance within GnasE1+/−m osteoclasts and therefore warrant further studies into understanding how Gsα influences osteoblast-osteoclast coupling interactions.
To bin or not to bin: analyzing single-cell growth data
Authors: Kar Prathitha , Tiruvadi-Krishnan Sriram , Männik Jaana , Männik Jaan , Amir Ariel
Published: July 2021

Collection of high-throughput data has become prevalent in biology. Large datasets allow the use of statistical constructs such as binning and linear regression to quantify relationships between variables and hypothesize underlying biological mechanisms based on it. We discuss several such examples in relation to single-cell data and cellular growth. In particular, we show instances where what appears to be ordinary use of these statistical methods leads to incorrect conclusions such as growth being non-exponential as opposed to exponential and vice versa. We propose that the data analysis and its interpretation should be done in the context of a generative model, if possible. In this way, the statistical methods can be validated either analytically or against synthetic data generated via the use of the model, leading to a consistent method for inferring biological mechanisms from data. On applying the validated methods of data analysis to infer cellular growth on our experimental data, we find the growth of length inE. colito be non-exponential. Our analysis shows that in the later stages of the cell cycle the growth rate is faster than exponential.
Disordered climate threatens short-distance migrants
Authors: Yang Haile , Yu Luxian , Qi Hongfang , Fu Shengyun , Wang Yang , Yang Jianxin , Du Hao
Published: July 2021

Global climate change has led to a warmer world, changing the migratory and breeding behaviors of many species, and short-distance migrants may benefit from climate change. With climate change leading to an increasingly disordered climate, we show here that a disordered spring climate disturbs the migration and breeding of a short-distance anadromous fish. In 2020, on the Qinghai-Tibetan Plateau, an abnormally low temperature in April delayed the migration rhythm of Gymnocypris przewalskii by nearly 10 days, while the gonadal development rhythm of the breeding population was almost normal. The phenology mismatch decreased the migrating populations by 30–70%, reducing the larval flux by nearly 80%. This case reveals that for short-distance migrants, different phenologies within the same species respond to disordered climates differently, which leads to phenology mismatches and then threatens the species. Along with increasing local extreme weather and climate events, short-distance migrants need more attention and conservation actions.
Quantification of within-patientStaphylococcus aureusphenotypic heterogeneity as a proxy for presence of persisters across clinical presentations
Authors: Bär Julian , Boumasmoud Mathilde , Shambat Srikanth Mairpady , Vulin Clément , Huemer Markus , Schweizer Tiziano A. , Gómez-Mejia Alejandro , Eberhard Nadia , Achermann Yvonne , Zingg Patrick O. , Mestres Carlos–A. , Brugger Silvio D. , Schüpbach Reto A. , Kouyos Roger D. , Hasse Barbara , Zinkernagel Annelies S.
Published: July 2021

Background

Difficult-to-treat infections caused by antibiotic susceptible strains have been linked with the occurrence of persisters. Persisters are a subpopulation of dormant bacteria that tolerate antibiotic exposure despite lacking genetic resistance. They can be identified phenotypically upon plating on nutrient agar because of their altered growth dynamics, resulting in colony size heterogeneity. The occurrence of within-patient bacterial phenotypic heterogeneity in various infections and clinical determinants of persister formation remain unknown.

Methods

We plated bacteria derived from 132 patient-samples of difficult-to-treat infections directly on nutrient-rich agar and monitored colony growth by time-lapse imaging. Of these, we retained 36Staphylococcus aureusmono-cultures for further analysis. We investigated clinical factors potentially associated with increased colony growth-delay with regression analyses. Additionally, we corroborated the clinical findings usingin vitrogrown static biofilms, exposed to distinct antibiotics.

Results

The extent of phenotypic heterogeneity of patient-derivedS. aureusvaried substantially between patients. Increased heterogeneity coincided with increased median growth-delay. Multivariable regression showed that rifampicin treatment was significantly associated with increased median growth-delay.S. aureusgrown in biofilms and exposed to high concentrations of rifampicin or a combination of rifampicin with either clindamycin or levofloxacin exhibited prolonged growth-delay, correlating with a strain-dependent increase in antibiotic tolerance.

Conclusions

Upon direct cultivation on nutrient-rich agar,S. aureusfrom difficult-to-treat infections commonly exhibited colony size heterogeneity. This was due to heterogeneous delays in growth resumption, with delays larger than two days in the most extreme cases. Since bacteria in a dormant state are tolerant to antibiotics, the observation of large growth-delays might have direct clinical implications. Future studies are needed to assess the potential of bacterial phenotypic heterogeneity quantification for staphylococcal infections prognosis.
Microsecond hydrodynamic interactions in dense colloidal dispersions probed at the European XFEL
Authors: Dallari Francesco , Jain Avni , Sikorski Marcin , Möller Johannes , Bean Richard , Boesenberg Ulrike , Frenzel Lara , Goy Claudia , Hallmann Jörg , Kim Yoonhee , Lokteva Irina , Markmann Verena , Mills Grant , Rodriguez-Fernandez Angel , Roseker Wojciech , Scholz Markus , Shayduk Roman , Vagovic Patrik , Walther Michael , Westermeier Fabian , Madsen Anders , Mancuso Adrian P. , Grübel Gerhard , Lehmkühler Felix
Published: July 2021

Many soft-matter systems are composed of macromolecules or nanoparticles suspended in water. The characteristic times at intrinsic length scales of a few nanometres fall therefore in the microsecond and sub-microsecond time regimes. With the development of free-electron lasers (FELs) and fourth-generation synchrotron light-sources, time-resolved experiments in such time and length ranges will become routinely accessible in the near future. In the present work we report our findings on prototypical soft-matter systems, composed of charge-stabilized silica nanoparticles dispersed in water, with radii between 12 and 15 nm and volume fractions between 0.005 and 0.2. The sample dynamics were probed by means of X-ray photon correlation spectroscopy, employing the megahertz pulse repetition rate of the European XFEL and the Adaptive Gain Integrating Pixel Detector. We show that it is possible to correctly identify the dynamical properties that determine the diffusion constant, both for stationary samples and for systems driven by XFEL pulses. Remarkably, despite the high photon density the only observable induced effect is the heating of the scattering volume, meaning that all other X-ray induced effects do not influence the structure and the dynamics on the probed timescales. This work also illustrates the potential to control such induced heating and it can be predicted with thermodynamic models.
Crystal growth and physical properties of an antiferromagnetic molecule: trans-dibromidotetrakis(acetonitrile)chromium(III) tribromide, [CrBr2(NCCH3)4](Br3)
Authors: Dissanayaka Mudiyanselage Ranuri S. , Kong Tai , Xie Weiwei
Published: July 2021

The synthesis, crystal structure determination, magnetic properties and bonding interaction analysis of a novel 3d transition-metal complex, [CrBr2(NCCH3)4](Br3), are reported. Single-crystal X-ray diffraction results show that [CrBr2(NCCH3)4](Br3) crystallizes in space group C2/m (No. 12) with a symmetric tribromide anion and the powder X-ray diffraction results show the high purity of the material specimen. X-ray photoelectron studies with a combination of magnetic measurements demonstrate that Cr adopts the 3+ oxidation state. Based on the Curie–Weiss analysis of magnetic susceptibility data, the Néel temperature is found to be around 2.2 K and the effective moment (μeff) of Cr3+ in [CrBr2(NCCH3)4](Br3) is ∼3.8 µB, which agrees with the theoretical value for Cr3+. The direct current magnetic susceptibility of the molecule shows a broad maximum at ∼2.3 K, which is consistent with the theoretical Néel temperature. The maximum temperature, however, shows no clear frequency dependence. Combined with the observed upturn in heat capacity below 2.3 K and the corresponding field dependence, it is speculated that the low-temperature magnetic feature of a broad transition in [CrBr2(NCCH3)4](Br3) could originate from a crossover from high spin to low spin for the split d orbital level low-lying states rather than a short-range ordering solely; this is also supported by the molecular orbital diagram obtained from theoretical calculations.
Pressure-induced structural phase transitions in bismuth tungstate Bi2WO6
Authors: Lis Olga N. , Kichanov Sergey E. , Kozlenko Denis P. , Belozerova Nadezhda M. , Lukin Evgeniy V. , Balakumar Subramanian , Savenko Boris N.
Published: July 2021

The pressure-induced structural phase transitions in bismuth tungstate Bi2WO6 have been studied using neutron diffraction and Raman spectroscopy at high pressures up to 7 and 30 GPa, respectively. A rich structural polymorphism was revealed. At P ≃ 3.5 GPa a phase transition from the initial orthorhombic phase of P21
ab symmetry to an orthorhombic phase of B2cb symmetry was observed. This transition is caused by the complex spatial rotation of the WO6 octahedra. A subsequent isostructural phase transition to another orthorhombic phase of B2cb symmetry was detected at P ≃ 5.9 GPa, accompanied by changes in both the mutual rotation and tilting of the oxygen octahedra with respect to the crystal b axis. Two more pressure-induced phase transitions in Bi2WO6 at high pressures of 11.5 and 20 GPa were observed in the Raman spectra. These pressure-driven phase transitions in bismuth tungstate are accompanied by anomalies in the pressure dependences of the unit-cell parameters, bond lengths and angles, and in the vibrational modes.
Comparison of the temperature- and pressure-dependent behavior of the crystal structure of CrAs
Authors: Eich Andreas , Grzechnik Andrzej , Paulmann Carsten , Müller Thomas , Su Yixi , Wolf Thomas , Friese Karen
Published: July 2021

The crystal structure of CrAs was investigated using synchrotron X-ray single-crystal diffraction for separate dependences on temperature (30–400 K) and on pressure (0–9.46 GPa). The isosymmetrical magnetostructural phase transition at T
N = 267 K can induce a change in the microstructure by twinning due to a crossing of the orthohexagonal setting of the unit-cell parameter ratio c/b. Within the crystal structure, one particular Cr–Cr distance exhibits anomalous behavior in that it is nearly unaffected by temperature and pressure in the paramagnetic phase, which is stable above 267 K and at high pressures. The distinction of this shortest Cr–Cr distance might be of importance for the superconducting properties of CrAs.
Low-temperature phase transition and magnetic properties of K3YbSi2O7
Authors: Dabić Predrag , Kahlenberg Volker , Krüger Biljana , Rodić Marko , Kovač Sabina , Blanuša Jovan , Jagličić Zvonko , Karanović Ljiljana , Petříček Václav , Kremenović Aleksandar
Published: July 2021

The new ambient-temperature hexagonal (space group P63
/mmc) polymorph of tripotassium ytterbium(III) disilicate (β-K3YbSi2O7) has been synthesized by the high-temperature flux method and subsequently structurally characterized. In the course of the temperature-dependent single-crystal diffraction experiments, a phase transformation of β-K3YbSi2O7 to a novel low-temperature orthorhombic phase (β′-K3YbSi2O7, space group Cmcm) has been observed at about 210 K. β-K3YbSi2O7 is isostructural with K3ErSi2O7, whereas β′-K3YbSi2O7 adopts a new type of structure. Both compounds can be built up from a regular alternation of layers of two types, which are parallel to the (001) plane. In the octahedral layer, YbO6 octahedra are isolated and linked by K1O6+3 polyhedra. The second, slightly thicker sorosilicate layer is formed by a combination of Si2O7 dimers and K2O6+3 polyhedra. The boundary between the layers is a pseudo-kagome oxide sheet based on 3.6.3.6 meshes. The phase transition is due to a tilt of the two SiO4 tetrahedra forming a single dimer which induces a decrease of the Si—O—Si angle between bridging Si—O bonds from 180° (dictated by symmetry in space group P63/mmc) to ≃164°. Magnetic characterization indicates that K3YbSi2O7 remains paramagnetic down to 2 K, showing no apparent influence of the phase transformation on its magnetic properties. Analysis of the magnetization data revealed the positions of the three lowest crystal field levels of the Yb3+ cations, as well as the corresponding projections of their angular momentum on the direction of the magnetic field.
2/1 and 1/1 cubic approximants in the ternary R-Cd-Mg (R = Y, Er) systems
Authors: Yamada Tsunetomo , Fujita Nobuhisa , Labib Farid
Published: July 2021

The atomic structures of three cubic approximants (cAPs), Y12.7Cd61.8Mg25.5 [2/1 cAP with space group Pa
3, a = 25.0654 (1) Å] and Er12.5Cd72.0Mg15.5 [2/1 cAP with Pa
3, a = 24.9658 (1) Å], and Y14.5Cd66.1Mg19.4 [1/1 cAP with Im
3, a = 15.4577 (1) Å], were investigated using X-ray structure analysis. The two 2/1  cAPs were found to be isostructural to the binary 2/1 cAP, YbCd5.8, which is composed of two building units, namely Tsai-type rhombic triacontahedron (RTH) cluster and double-Friauf polyhedron (DFP). The 1/1 cAP, in contrast, was found to be isostructural to the binary 1/1 cAP, YbCd6, which is composed solely of the RTH cluster. The refined structure models of the three cAPs exhibit substitutional disorders due to the Mg content that enters into Cd sites of the parent binary cAPs. In addition, in the 2/1 cAPs, the Y3(Er3) site on the third icosahedron shell of the RTH cluster and two positions inside DFP, Y5(Er5) sites, are partially mixed with Mg. Moreover, characteristic positional disorders owing to orientational disorder in the first shell of the RTH cluster is observed in all the three cAPs. A close relationship between the occupational disorder of the Y3(Er3) and Y5(Er5) sites in 2/1 cAPs and the elemental distribution in their first coordination shells is revealed.
Isopropyl 3-deoxy-α-D-ribo-hexopyranoside (isopropyl 3-deoxy-α-D-glucopyranoside): evaluating trends in structural parameters
Authors: Lin Jieye , Oliver Allen G. , Meredith Reagan J. , Carmichael Ian , Serianni Anthony S.
Published: July 2021

Isopropyl 3-deoxy-α-D-ribo-hexopyranoside (isopropyl 3-deoxy-α-D-glucopyranoside), C9H18O5, (I), crystallizes from a methanol–ethyl acetate solvent mixture at room temperature in a 4
C
1 chair conformation that is slightly distorted towards the C5
S
C1 twist-boat form. A comparison of the structural parameters in (I), methyl α-D-glucopyranoside, (II), α-D-glucopyranosyl-(1→4)-D-glucitol (maltitol), (III), and 3-deoxy-α-D-ribo-hexopyranose (3-deoxy-α-D-glucopyranose), (IV), shows that most endocyclic and exocyclic bond lengths, valence bond angles and torsion angles in the aldohexopyranosyl rings are more affected by anomeric configuration, aglycone structure and/or the conformation of exocyclic substituents, such as hydroxymethyl groups, than by monodeoxygenation at C3. The structural effects observed in the crystal structures of (I)–(IV) were confirmed though density functional theory (DFT) calculations in computed structures (I)c–(IV)c. Exocyclic hydroxymethyl groups adopt the gauche–gauche (gg) conformation (H5 anti to O6) in (I) and (III), and the gauche–trans (gt) conformation (C4 anti to O6) in (II) and (IV). The O-glycoside linkage conformations in (I) and (III) resemble those observed in disaccharides containing β-(1→4) linkages.
Bis{N′-[3-(4-nitrophenyl)-1-phenylprop-2-en-1-ylidene]-N-phenylcarbamimidothioato}zinc(II): crystal structure, Hirshfeld surface analysis and computational study
Authors: Tan Ming Yueh , Kwong Huey Chong , Crouse Karen A. , Ravoof Thahira B. S. A. , Tiekink Edward R. T.
Published: July 2021

The title zinc bis(thiosemicarbazone) complex, [Zn(C22H17N4O2S)2], comprises two N,S-donor anions, leading to a distorted tetrahedral N2S2 donor set. The resultant five-membered chelate rings are nearly planar and form a dihedral angle of 73.28 (3)°. The configurations about the endocyclic- and exocyclic-imine bonds are Z and E, respectively, and that about the ethylene bond is E. The major differences in the conformations of the ligands are seen in the dihedral angles between the chelate ring and nitrobenzene rings [40.48 (6) cf. 13.18 (4)°] and the N-bound phenyl and nitrobenzene ring [43.23 (8) and 22.64 (4)°]. In the crystal, a linear supramolecular chain along the b-axis direction features amine-N—H...O(nitro) hydrogen bonding. The chains assemble along the 21-screw axis through a combination of phenyl-C—H...O(nitro) and π(chelate ring)–π(phenyl) contacts. The double chains are linked into a three-dimensional architecture through phenyl-C—H...O(nitro) and nitro-O...π(phenyl) interactions.
Two polymorphs of [Rh(μ-I)(COD)]2
Authors: Ullery David R. , Moore Curtis E. , Thomas Christine M.
Published: July 2021

The solid-state structure of di-μ-iodido-bis{[(1,2,5,6-η)-cycloocta-1,4-diene]rhodium(I)}, [Rh2I2(C8H12)2] or [Rh(μ-I)(COD)]2, was determined from two crystals with different morphologies, which were found to correspond to two polymorphs containing Rh dimers with significantly different molecular structures. Both polymorphs are monoclinic and the [Rh(μ-I)(COD)]2 molecules in each case possess C2
v symmetry. However, the core geometry of the butterfly-shaped Rh2I2 core differs substantially. In the C2/c polymorph, the core geometry of [Rh(μ-I)(COD)]2
B is bent, with a hinge angle of 96.13 (8)° and a Rh...Rh distance of 2.9612 (11) Å. The P21/c polymorph features a more planar [Rh(μ-I)(COD)]2
P core geometry, with a hinge angle of 145.69 (9)° and a Rh...Rh distance of 3.7646 (5) Å.
Crystal structure, Hirshfeld surface analysis and interaction energy calculation of 4-(furan-2-yl)-2-(6-methyl-2,4-dioxopyran-3-ylidene)-2,3,4,5-tetrahydro-1H-1,5-benzodiazepine
Authors: El Hafi Mohamed , Lahmidi Sanae , El Ghayati Lhoussaine , Hökelek Tuncer , Mague Joel T. , Amer Bushra , Sebbar Nada Kheira , Essassi El Mokhtar
Published: July 2021

The title compound {systematic name: (S,E)-3-[4-(furan-2-yl)-2,3,4,5-tetrahydro-1H-benzo[b][1,4]diazepin-2-ylidene]-6-methyl-2H-pyran-2,4(3H)-dione}, C19H16N2O4, is constructed from a benzodiazepine ring system linked to furan and pendant dihydropyran rings, where the benzene and furan rings are oriented at a dihedral angle of 48.7 (2)°. The pyran ring is modestly non-planar [largest deviation of 0.029 (4) Å from the least-squares plane] while the tetrahydrodiazepine ring adopts a boat conformation. The rotational orientation of the pendant dihydropyran ring is partially determined by an intramolecular N—HDiazp...ODhydp (Diazp = diazepine and Dhydp = dihydropyran) hydrogen bond. In the crystal, layers of molecules parallel to the bc plane are formed by N—HDiazp...ODhydp hydrogen bonds and slipped π–π stacking interactions. The layers are connected by additional slipped π–π stacking interactions. A Hirshfeld surface analysis of the crystal structure indicates that the most important contributions for the crystal packing are from H...H (46.8%), H...O/O...H (23.5%) and H...C/C...H (15.8%) interactions, indicating that van der Waals interactions are the dominant forces in the crystal packing. Computational chemistry indicates that in the crystal the N—H...O hydrogen-bond energy is 57.5 kJ mol−1.
Omnichannel retailing: a bibliometric and network visualization analysis
Authors: Mahadevan Kala , Joshi Sujata
Published: July 2021

Purpose

The purpose of this paper is to review the extant research literature on omnichannel retailing and map the research trends in this field through a bibliometric analysis and network visualization exercise.

Design/methodology/approach

This paper employs bibliometric analysis techniques on research literature retrieved from the Scopus and Web of Science databases over the period 2013–2020 and assesses indicators such as research production and citation trends, top contributing authors, countries, journals and organizations through tools offered by the Scopus/Web of Science databases as well as Biblioshiny. A network visualization analysis of patterns such as keyword co-occurrences and co-authorship linkages between contributing countries has been investigated through the use of VOSviewer.

Findings

The bibliometric analysis indicates that research in this field is currently dominated by USA and China with Germany and UK also being key contributors. The analysis has indicated that the field of omnichannel retailing straddles multiple domains such as logistics, distribution, operations and consumer behavior, thereby offering significant future scope for research linking omnichannel retailing with these subject areas.

Originality/value

This study maps the structure of research done in the field of omnichannel retailing and outlines the key contributors in terms of authors, journals and organizations that can serve as an input for future research. The study also identifies possible avenues for future research in the knowledge domain of omnichannel retailing.
Institutional motivations for hiring international academics in Poland
Authors: Luczaj Kamil , Kurek-Ochmanska Olga
Published: July 2021

Purpose

The purpose of this paper is to uncover the basic motivations of the administrators (referred to also as “managers”) to hire foreign-born employees in the academic system, which is relatively ethnically homogenous and where the proficiency in Polish is still a strong asset. By doing this, the authors make an attempt to theorise the value of internationalisation of higher education in the academic peripheries.

Design/methodology/approach

This study reports the finding of 20 qualitative interviews with the deans and other senior academic officials serving managerial functions at Polish public and private universities.

Findings

The four basic motivations expressed directly by the mangers were (1) the crave for cultural diversity, (2) willingness to “Westernize” the academe, (3) a need for academic achievement and (4) staff shortages. In the discussion, the authors show, however, that the discursive order of these institutional motivations to hire international faculty is incompatible with motivations of international faculty to seek employment in Poland and statistical data regarding their concentration in different academic centres.

Originality/value

The paper tackles crucial issues regarding staffing (including recruitment and retention) and diversity hiring in a country with an “emigration culture”, similar to other East European states, namely a place from which highly skilled workers emigrate. A relocation to Poland is a rather unusual reverse migration, or “stepping down”, to a periphery to use it as a possible stepping stone for career progression.