Regioselective Derivatization of Silylated [20]Silafulleranes.

Silafulleranes with endohedral Cl- ions are a unique, scarcely explored class of structurally well-defined silicon clusters and host-guest complexes. Herein, we report regioselective derivatization reactions on the siladodecahedrane [nBu4N][Cl@Si20(SiCl3)12Cl8] ([nBu4N][1]), which has its cluster surface decorated with 12 SiCl3 and 8 Cl substituents in perfect Th symmetry. The room-temperature reaction of [nBu4N][1] with excess iBu2AlH in ortho-difluorobenzene (oDFB) furnishes perhydrogenated [nBu4N][Cl@Si20(SiH3)12H8] ([nBu4N][2]) in 50% yield; the non-pyrophoric [2]- is the largest structurally authenticated (by X-ray diffraction) hydridosilane known to date. A simple switch from pure oDFB to an oDFB/Et2O solvent mixture suppresses core hydrogenation and results in the formation of [nBu4N][Cl@Si20(SiH3)12Cl8] ([nBu4N][3]). In addition to the exhaustive Cl/H exchange at all 44 Si-Cl bonds of [1]- and the regioselective 36-fold silyl group hydrogenation, we achieved the simultaneous introduction of Me substituents at all 8 SiCl vertices along with the conversion of all 12 SiCl3 to SiH3 groups by treating [nBu4N][1] with Me2AlH/Me3Al in oDFB ([nBu4N][Cl@Si20(SiH3)12Me8], [nBu4N][4]; 73%). Quantum-chemical free-energy calculations find an SN2-Si-type hydrogenation of the exohedral SiCl3 moieties in [1]- (trigonal-bipyramidal intermediate) slightly preferred over metathesis-like SNi-Si substitutions (four-membered transition state). Cage hydrogenation likely occurs via SNi-Si processes. The experimentally demonstrated influence of an Et2O co-solvent, which drastically increases the respective reaction barriers, is attributed to the increased stability of the resulting iBu2AlH-OEt2 adduct and its higher steric bulk compared to free iBu2AlH.

Can You Tell Who Scores? An Assessment of the Recognition of Affective States Based on the Nonverbal Behavior of Amateur Tennis Players in Competitive Matches.

The purpose of the present study was to assess whether the recognition of tennis players' affective state associated with their nonverbal behavior would be influenced by (a) the importance of the situation, (b) the point outcome, and (c) the tennis expertise of the observer. Two hundred sixty-nine participants (Mage = 30.51 years; 116 female; 79 tennis club members) watched video excerpts showing the nonverbal behavior of amateur tennis players during competitive matches immediately after the end of a rally and were asked to estimate whether the player had just won or lost the point. Results indicate that the recognition rates were higher for situations closer to the end of a game, closer to the end of a set, and with a tighter score during a game. Moreover, recognition rates were higher for lost than for won points, while the tennis expertise of participants had no influence on the recognition rates.

Synthesis, bridgehead functionalization, and photoisomerization of 9,10-diboratatriptycene dianions.

9,10-Diboratatriptycene salts M2[RB(µ-C6H4)3BR] (R = H, Me; M+ = Li+, K+, [n-Bu4N]+) have been synthesized via [4 + 2] cycloaddition between doubly reduced 9,10-dihydro-9,10-diboraanthracenes M2[DBA] and benzyne, generated in situ from C6H5F and C6H5Li or LiN(i-Pr)2. [HB(µ-C6H4)3BH]2- reacts with CH2Cl2 to form quantitatively the bridgehead-derivatized [ClB(µ-C6H4)3BCl]2-, while twofold H- abstraction with B(C6F5)3 in the presence of SMe2 leads cleanly to the diadduct (Me2S)B(µ-C6H4)3B(SMe2). Photoisomerization of K2[HB(µ-C6H4)3BH] (THF, medium-pressure Hg lamp) provides facile access to diborabenzo[a]fluoranthenes, a little explored form of boron-doped polycyclic aromatic hydrocarbons. According to DFT calculations, the underlying reaction mechanism consists of three main steps: (i) photoinduced di-π-borate rearrangement, (ii) "walk reaction" of a BH unit, and (iii) boryl anion-like C-H activation.

Catalyst-free diboration and silaboration of alkenes and alkynes using bis(9-heterofluorenyl)s.

Diboration and silaboration reactions are prominent tools to introduce valuable functional groups into organic substrates. To date, most diboranes(4) and silylboranes used for this purpose are electronically and/or kinetically stabilized and require activation by a catalyst. We show here that the tetraaryl (µ-hydrido)diborane(4) anion [3]- and the silyl (hydrido)borate ([4]-)/Me3SiBr system react spontaneously with the archetypal olefin ethylene in the absence of a catalyst. The actual active species in both cases are the valence isoelectronic intermediates [FluB-B(H)Flu]- ([1]-) and FluB-Si(H)Flu (2), which consist of two 9-heterofluorenyl halves that get attached to the 1 and 2 positions of ethylene. At room temperature, [1]- is present in a dynamic equilibrium with its isolable isomer [3]-, while 2 has to be released in situ at low temperatures by H- abstraction from [4]-. Quantum-chemical calculations show qualitatively identical reaction mechanisms for [1]- and 2. Since the reactions start with π coordination of the ethylene molecule to a vacant B(pz) orbital, the high Lewis acidity and low steric hindrance of the 9-borafluorenyl fragments are the keys to success. As the reaction proceeds, back-donation from the B-E bond into the ethylene π* orbital becomes increasingly important (E = B, Si). The scope of the reactions has been extended to tBu(H)C[double bond, length as m-dash]CH2 and tBuC[triple bond, length as m-dash]CH on the one hand and FluB-Si(Cl)Flu as well as FluB-Si(Cl)Ph2 on the other.

Accuracy of Information and References Using ChatGPT-3 for Retrieval of Clinical Radiological Information.

Purpose: To assess the accuracy of answers provided by ChatGPT-3 when prompted with questions from the daily routine of radiologists and to evaluate the text response when ChatGPT-3 was prompted to provide references for a given answer. Methods: ChatGPT-3 (San Francisco, OpenAI) is an artificial intelligence chatbot based on a large language model (LLM) that has been designed to generate human-like text. A total of 88 questions were submitted to ChatGPT-3 using textual prompt. These 88 questions were equally dispersed across 8 subspecialty areas of radiology. The responses provided by ChatGPT-3 were assessed for correctness by cross-checking them with peer-reviewed, PubMed-listed references. In addition, the references provided by ChatGPT-3 were evaluated for authenticity. Results: A total of 59 of 88 responses (67%) to radiological questions were correct, while 29 responses (33%) had errors. Out of 343 references provided, only 124 references (36.2%) were available through internet search, while 219 references (63.8%) appeared to be generated by ChatGPT-3. When examining the 124 identified references, only 47 references (37.9%) were considered to provide enough background to correctly answer 24 questions (37.5%). Conclusion: In this pilot study, ChatGPT-3 provided correct responses to questions from the daily clinical routine of radiologists in only about two thirds, while the remainder of responses contained errors. The majority of provided references were not found and only a minority of the provided references contained the correct information to answer the question. Caution is advised when using ChatGPT-3 to retrieve radiological information.

Crystal structure of [tBuMgCl]2[MgCl2(Et2O)2]2.

The title compound, di-µ3-chlorido-tetra-µ2-chlorido-tetra-kis-(diethyl ether-κO)bis-(1,1-di-methyl-eth-yl)tetra-magnesium, [Mg4(C4H9)2Cl6(C4H10O)4], features an Mg4Cl6 open-cube cluster. The two four-coordinate Mg2+ ions show an almost tetra-hedral coordination, whereas the two six-coordinate Mg2+ ions have their ligands in an octa-hedral environment. The Mg-Cl bond lengths differ depending on the coordination number (2 or 3) of the bridging µ-Cl- ligands. There are few comparable structures deposited in the Cambridge Structural Database.

Volumetric differences of thalamic nuclei in children with trisomy 21.

OBJECTIVES: Histological studies have shown alterations of thalamic nuclei in patients with Down syndrome (DS). The correlation of these changes on MRI (magnetic resonance imaging) is unclear. Therefore, this study investigates volumetric differences of thalamic nuclei in children with DS compared to controls. METHODS: Patients were retrospectively identified between 01/2000 and 10/2021. Patient inclusion criteria were: (1) 0-18 years of age, (2) diagnosis of DS, and (3) availability of a brain MRI without parenchymal injury and a non-motion-degraded volumetric T1-weighted sequence. Whole thalamus and thalamic nuclei (n = 25) volumes were analyzed bilaterally relative to the total brain volume (TBV). Two-sided t-tests were used to evaluate differences between groups. Differences were considered significant if the adjusted p-value was <0.05 after correction for multiple hypothesis testing using the Holm-Bonferroni method. RESULTS: 21 children with DS (11 females, 52.4%, mean age: 8.6 ± 4.3 years) and 63 age- and sex-matched controls (32 females, 50.8%, 8.6 ± 4.3 years) were studied using automated volumetric segmentation. Significantly smaller ratios were found for nine thalamic nuclei and the whole thalamus on the right and five thalamic nuclei on the left. TBV was significantly smaller in patients with DS (p < 0.001). No significant differences were found between the groups for age and sex. CONCLUSIONS: In this exploratory volumetric analysis of the thalamus and thalamic nuclei, we observed statistically significant volumetric changes in children with DS. Our findings confirm prior neuroimaging and histological studies and extend the range of involved thalamic nuclei in pediatric DS.

Pulmonary perfusion defect volume on dual-energy CT: prognostic marker of adverse events in patients with suspected pulmonary embolism.

To assess whether quantification of pulmonary perfusion defects on dual-energy computed tomography (DECT) relates to adverse events beyond clinical parameters and traditional embolus detection in patients with suspected pulmonary embolism (PE). We included consecutive patients who underwent DECT to rule out acute PE in 2018-2020 and recorded incident adverse events, defined as a composite of short-term (< 30 days) in-hospital all-cause mortality or admission to intensive care unit. Relative perfusion defect volume (PDV) was measured on DECT and indexed by total lung volume. PDV was then related to adverse events using logistic regressions adjusting for clinical parameters, clinical PE pre-test probability (Wells score), and visual PE burden on pulmonary angiography (Qanadli score). Among 136 included patients (63 [46%] females; age: 70 ± 14 years), 19/136 (14%) experienced adverse events during a median hospitalization of 7.5 (4-14) days. Overall, 7/19 (37%) events occurred in those without visible emboli but with measurable perfusion defects. An increase of PDV by one standard deviation was associated with over two times higher odds of adverse events (OR = 2.24; 95%CI:1.37-3.65; p = 0.001). This association remained significant after adjusting for the Wells and Qanadli scores (OR = 2.34; 95%CI:1.20-4.60; p = 0.013). PDV significantly increased the combined discriminatory capacity of Wells and Qanadli scores (AUC 0.76 vs. 0.80; p = 0.011 for difference). DECT-derived PDV may represent a prognostic imaging marker with incremental value beyond clinical and traditional imaging findings, improving risk stratification and aiding clinical management in patients with suspected PE.

MRI Volumetric Analysis of the Hypothalamus and Limbic System across the Pediatric Age Span.

PURPOSE: Literature is scarce regarding volumetric measures of limbic system components across the pediatric age range. The purpose of this study is to remedy this scarcity by reporting continuous volumetric measurements of limbic system components, and to provide consistent stratification data including age-related trajectories and sex-related differences in the pediatric age range in order to improve the recognition of structural variations that might reflect pathology. METHODS: In this retrospective study, MRI sequences of children with normal clinical MRI examinations of the brain acquired between January 2010 and December 2019 were included. Isotropic 3D T1-weighted were processed using FreeSurfer version 7.3. Total brain volume and volumes of the limbic system including the hippocampus, parahippocampal gyrus, amygdala, hypothalamus, cingulate gyrus, entorhinal cortex, anteroventral thalamic nucleus, and whole thalamus were assessed. Parcellated output was displayed with the respective label map overlay and images were visually inspected for accuracy of regional segmentation results. Continuous data are provided as mean and standard deviation with quadratic trendlines and as mean and 95% confidence intervals. Categorical data are presented as integers and percentages (%). RESULTS: A total of 724 children (401 female, 55.4%), with a mean age at time of MRI of 10.9 ± 4.2 years (range: 1.9-18.2 years), were included in the study. For females, the total brain volume increased from 955 ± 70 mL at the age of 2-3 years to 1140 ± 110 mL at the age of 17-18 years. Similarly, the total brain volume increased for males from 1004 ± 83 mL to 1263 ± 96 mL. The maximum volume was noted at 11-12 years for females (1188 ± 90 mL) and at 14-15 years for males (1310 ± 159 mL). Limbic system structures reached their peak volume more commonly between the 13-14 years to 17-18 years age groups. The male cingulate gyrus, entorhinal cortex, and anteroventral thalamic nucleus reached peak volume before or at 9-10 years. CONCLUSION: This study provides unique age- and sex-specific volumes of the components of the limbic system throughout the pediatric age range to serve as normal values in comparative studies. Quantification of volumetric abnormalities of the limbic system on brain MRI may offer insights into phenotypical variations of diseases and may help elucidate new pathological phenotypes.

Electrical and Structural Properties of Si1-xGex Nanowires Prepared from a Single-Source Precursor.

Si1-xGex nanowires (NWs) were prepared by gold-supported chemical vapor deposition (CVD) using a single-source precursor with preformed Si-Ge bonds. Besides the tamed reactivity of the precursor, the approach reduces the process parameters associated with the control of decomposition characteristics and the dosing of individual precursors. The group IV alloy NWs are single crystalline with a constant diameter along their axis. During the wire growth by low pressure CVD, an Au-containing surface layer on the NWs forms by surface diffusion from the substrate, which can be removed by a combination of oxidation and etching. The electrical properties of the Si1-xGex/Au core-shell NWs are compared to the Si1-xGex NWs after Au removal. Core-shell NWs show signatures of metal-like behavior, while the purely semiconducting NWs reveal typical signatures of intrinsic Si1-xGex. The synthesized materials should be of high interest for applications in nano- and quantum-electronics.

Fet-Net Algorithm for Automatic Detection of Fetal Orientation in Fetal MRI.

Identifying fetal orientation is essential for determining the mode of delivery and for sequence planning in fetal magnetic resonance imaging (MRI). This manuscript describes a deep learning algorithm named Fet-Net, composed of convolutional neural networks (CNNs), which allows for the automatic detection of fetal orientation from a two-dimensional (2D) MRI slice. The architecture consists of four convolutional layers, which feed into a simple artificial neural network. Compared with eleven other prominent CNNs (different versions of ResNet, VGG, Xception, and Inception), Fet-Net has fewer architectural layers and parameters. From 144 3D MRI datasets indicative of vertex, breech, oblique and transverse fetal orientations, 6120 2D MRI slices were extracted to train, validate and test Fet-Net. Despite its simpler architecture, Fet-Net demonstrated an average accuracy and F1 score of 97.68% and a loss of 0.06828 on the 6120 2D MRI slices during a 5-fold cross-validation experiment. This architecture outperformed all eleven prominent architectures (p < 0.05). An ablation study proved each component's statistical significance and contribution to Fet-Net's performance. Fet-Net demonstrated robustness in classification accuracy even when noise was introduced to the images, outperforming eight of the 11 prominent architectures. Fet-Net's ability to automatically detect fetal orientation can profoundly decrease the time required for fetal MRI acquisition.

Group IV heteroadamantanes: synthesis of Si6Sn4 and site-selective derivatization of Si6Ge4.

The mixed heteroadamantanes Si6Ge4 and Si6Sn4 are readily accessible from Me2ECl2/Si2Cl6/cat. Cl- (4 × EMe2, 2 × SiCl2, 4 × Si-SiCl3 vertices; E = Ge, Sn). Different from Si6Ge4, two skeletal isomers are formed in the case of Si6Sn4. Site-selective SiCl3-methylation of Si6Ge4 was achieved, leaving the SiCl2 groups untouched.

Multifaceted behavior of a doubly reduced arylborane in B-H-bond activation and hydroboration catalysis.

Alkali-metal salts of 9,10-dimethyl-9,10-dihydro-9,10-diboraanthrancene (M2[DBA-Me2]; M+ = Li+, Na+, K+) activate the H-B bond of pinacolborane (HBpin) in THF already at room temperature. For M+ = Na+, K+, the addition products M2[4] are formed, which contain one new H-B and one new B-Bpin bond; for M+ = Li+, the H- ion is instantaneously transferred from the DBA-Me2 unit to another equivalent of HBpin to afford Li[5]. Although Li[5] might commonly be considered a [Bpin]- adduct of neutral DBA-Me2, it donates a [Bpin]+ cation to Li[SiPh3], generating the silyl borane Ph3Si-Bpin; Li2[DBA-Me2] with an aromatic central B2C4 ring acts as the leaving group. Furthermore, Li2[DBA-Me2] catalyzes the hydroboration of various unsaturated substrates with HBpin in THF. Quantum-chemical calculations complemented by in situ NMR spectroscopy revealed two different mechanistic scenarios that are governed by the steric demand of the substrate used: in the case of the bulky Ph(H)C[double bond, length as m-dash]NtBu, the reaction requires elevated temperatures of 100 °C, starts with H-Bpin activation which subsequently generates Li[BH4], so that the mechanism eventually turns into "hidden borohydride catalysis". Ph(H)C[double bond, length as m-dash]NPh, Ph2C[double bond, length as m-dash]O, Ph2C[double bond, length as m-dash]CH2, and iPrN[double bond, length as m-dash]C[double bond, length as m-dash]NiPr undergo hydroboration already at room temperature. Here, the active hydroboration catalyst is the [4 + 2] cycloadduct between the respective substrate and Li2[DBA-Me2]: in the key step, attack of HBpin on the bridging unit opens the bicyclo[2.2.2]octadiene scaffold and gives the activated HBpin adduct of the Lewis-basic moiety that was previously coordinated to the DBA-B atom.

Lipid peroxidation and its repair in malaria parasites.

During its life cycle, the human malaria parasite Plasmodium falciparum is subjected to elevated levels of oxidative stress that cause damage to membrane lipids, a process referred to as lipid peroxidation. Control and repair of lipid peroxidation is critical for survival of P. falciparum. Here, we present an introduction into lipid peroxidation and review the current knowledge about the control and repair of the damage caused by lipid peroxidation in P. falciparum blood stages. We also review the recent identification of host peroxiredoxin 6 (PRDX6), as a key lipid-peroxidation-repair enzyme in P. falciparum blood stages. Such critical host factors provide novel targets for development of drugs against malaria.

Dope it with germanium: selective access to functionalized Si5Ge heterocycles.

The Cl- diadduct [nBu4N]2[A·2Cl] of the mixed cyclohexatetrelane (SiCl2)5(GeMe2), A, is accessible from Me2GeCl2, 6 eq. Si2Cl6, and 2 eq. [nBu4N]Cl in one step (96%). Free, tenfold functionalized A can be released from the primary product by decomplexation with AlCl3 (78%). Insight into the assembly mechanism of [nBu4N]2[A·2Cl] and the reactivity of A is provided.

An Educational Graphical User Interface to Construct Convolutional Neural Networks for Teaching Artificial Intelligence in Radiology.

Deep learning techniques using convolutional neural networks (CNNs) have been successfully developed for various medical image analysis tasks. However, the skills to understand and develop deep learning models are not usually taught during radiology training, which constitutes a barrier for radiologists looking to integrate machine learning (ML) into their research or clinical practice. In this work, we developed and evaluated an educational graphical user interface (GUI) to construct CNNs for teaching deep learning concepts to radiology trainees. The GUI was developed in Python using the PyQt and PyTorch frameworks. The functionality of the GUI was demonstrated through a binary classification task on a dataset of MR images of the brain. The usability of the GUI was assessed through 45-min user testing sessions with 5 neuroradiologists and neuroradiology fellows, assessing mean task completion times, the System Usability Scale (SUS), and a qualitative questionnaire as metrics. Task completion times were compared against a ML expert who performed the same tasks. After a 20-min introduction to CNNs and a walkthrough of the GUI, users were able to perform all assigned tasks successfully. There was no significant difference in task completion time compared to a ML expert. The educational GUI achieved a score of 82.5 on the SUS, suggesting that the system is highly usable. Users indicated that the GUI seems useful as an educational tool to teach ML topics to radiology trainees. An educational GUI allows interactive teaching in ML that can be incorporated into radiology training.

Diboraanthracene-Doped Polymer Systems for Colour-Tuneable Room-Temperature Organic Afterglow.

Organic ultralong room temperature phosphorescence (RTP), or organic afterglow, is a unique phenomenon, gaining widespread attention due to its far-reaching application potential and fundamental interest. Here, two laterally expanded 9,10-dimesityl-dihydro-9,10-diboraanthracene (DBA) derivatives are demonstrated as excellent afterglow materials for red and blue-green light emission, which is traced back to persistent thermally activated delayed fluorescence and RTP. The lateral substitution of polycyclic DBA scaffold, together with weak transversal electron-donating mesityl groups, ensures the optimal molecular properties for (reverse) intersystem crossing and long-lived triplet states in a rigid poly(methyl methacrylate) matrix. The achieved afterglow emission quantum yields of up to 3 % and 15 %, afterglow lifetimes up to 0.8 s and 3.2 s and afterglow durations up to 5 s and 25 s (for red and blue-green emitters, respectively) are attributed to the properties of single molecules.

(BO)2-Doped Tetrathia[7]helicene: A Configurationally Stable Blue Emitter.

Helicenes combine two central themes in chemistry: extended π-conjugation and chirality. Heteroatom doping preserves both characteristics and allows to modulate the electronic structure of a helicene. Herein, we report the (BO)2-doped tetrathia[7]helicene 1, which was prepared from 2-methoxy-3,3'-bithiophene via four steps. 1 is formally derived by substituting two (Mes)B-O moieties in place of (H)C=C(H) fragments in two benzene rings of parent tetrathia[7]helicene. X-ray crystallography revealed a dihedral angle of 50.26(9)° between the two terminal thiophene rings. (P)-/(M)-1 enantiomers were separated by chiral-HPLC and are configurationally stable at room temperature. The experimentally determined enantiomerization barrier of 27.4 ± 0.1 kcal mol-1 is lower than that of tetrathia[7]helicene (39.4 ± 0.1 kcal mol-1). Circular dichroism spectra of (P)- and (M)-1 show a perfect mirror-image relationship. 1 is a blue emitter (λem = 411 nm) with a photoluminescence quantum efficiency of ΦPL = 6% (cf. tetrathia[7]helicene: λem ≈ 405 nm, ΦPL = 5%).

A Hydride-Substituted Homoleptic Silylborate: How Similar is it to its Diborane(6)-Dianion Isostere?

The B-nucleophilic 9H-9-borafluorene dianion reacts with 9-chloro-9-silafluorene to afford air- and moisture-stable silylborate salts M[Ar2 (H)B-Si(H)Ar2 ] (M[HBSiH], M=Li, Na). Li[HBSiH] and Me3 SiCl give the B-pyridine adduct Ar2 (py)B-Si(H)Ar2 ((py)BSiH) or the chlorosilane Li[Ar2 (H)B-Si(Cl)Ar2 ] (Li[HBSiCl]) in C6 H6 -pyridine or THF. In both cases, the first step is H- abstraction at the B center. The resulting free borane subsequently binds a py or thf ligand. While the py adduct is stable at room temperature, the thf adduct undergoes a 1,2-H shift via the cyclic B(µ-H)Si intermediate BHSi, which is afterwards attacked at the Si atom by a Cl- ion to give Li[HBSiCl]. DFT calculations were employed to support the proposed reaction mechanism and to characterize the electronic structure of BHSi. Treatment of Li[HBSiCl] with the N-heterocyclic carbene IMe introduces the neutral donor at the Si atom and leads to Ar2 (H)B-Si(IMe)Ar2 (HBSi(IMe)), a donor-acceptor-stabilized silylene.