Pan-genome analysis sheds light on structural variation-based dissection of agronomic traits in melon crops.

Sweetness and appearance of fresh fruits are key palatable and preference attributes for consumers and are often controlled by multiple genes. However, fine-mapping the key loci or genes of interest by single genome-based genetic analysis is challenging. Herein, we present the chromosome-level genome assembly of 1 landrace melon accession (Cucumis melo ssp. agrestis) with wild morphologic features and thus construct a melon pan-genome atlas via integrating sequenced melon genome datasets. Our comparative genomic analysis reveals a total of 3.4 million genetic variations, of which the presence/absence variations (PAVs) are mainly involved in regulating the function of genes for sucrose metabolism during melon domestication and improvement. We further resolved several loci that are accountable for sucrose contents, flesh color, rind stripe, and suture using a structural variation (SV)-based genome-wide association study. Furthermore, via bulked segregation analysis (BSA)-seq and map-based cloning, we uncovered that a single gene, (CmPIRL6), determines the edible or inedible characteristics of melon fruit exocarp. These findings provide important melon pan-genome information and provide a powerful toolkit for future pan-genome-informed cultivar breeding of melon.

Exceptional Nexus in Bose-Einstein Condensates with Collective Dissipation.

In multistate non-Hermitian systems, higher-order exceptional points and exotic phenomena with no analogues in two-level systems arise. A paradigm is the exceptional nexus (EX), a third-order EP as the cusp singularity of exceptional arcs (EAs), that has a hybrid topological nature. Using atomic Bose-Einstein condensates to implement a dissipative three-state system, we experimentally realize an EX within a two-parameter space, despite the absence of symmetry. The engineered dissipation exhibits density dependence due to the collective atomic response to resonant light. Based on extensive analysis of the system's decay dynamics, we demonstrate the formation of an EX from the coalescence of two EAs with distinct geometries. These structures arise from the different roles played by dissipation in the strong coupling limit and quantum Zeno regime. Our Letter paves the way for exploring higher-order exceptional physics in the many-body setting of ultracold atoms.

Joint estimation model for FSO channel parameters and performance evaluation based on CNNs.

Free space optical (FSO) communication systems experience turbulence-induced fading. As a possible solution, adaptive transmission, which adjusts transmitter parameters based on instantaneous channel state information (CSI), can be used. Most of the existing channel estimation methods ignore the impact of detection noise at the receiver, which will lead to additional estimation errors. In this paper, a joint estimation model based on convolutional neural networks (CNNs) is proposed to estimate detection noise and turbulence fading parameters. We obtained turbulence channel simulation data sets considering the background of detection noise based on the edge probability distribution function of the receive signal. The training of the CNN estimator is carried out through maximum pooling, adaptive learning rate, and regularization, ultimately accurately estimating channel characteristics based on the optimal output results of the network. The simulation results show that the proposed CNN joint estimator performs better in high-detection-noise environments compared with traditional maximum likelihood estimators, and it has better generalization ability in different real atmospheric environments.

Electric-Field-Enhanced Electroluminescence Color Tuning of Colloidal Type-II Tetrapods.

Color-tunable electroluminescence (EL) from a single emitting material can be used to develop single-pixel multicolor displays. However, finding materials capable of broad EL color tuning remains challenging. Herein, we report the observation of broad voltage-tunable EL in colloidal type-II InP/ZnS quantum-dot-seeded CdS tetrapod (TP) LEDs. The EL color can be tuned from red to bluish white by varying the red and blue emission intensities from type-II interfaces and arms, respectively. The capacitor device proves that an external electric field can enhance the color tuning in type-II TPs. COMSOL simulations, numerical calculations, and transient absorption measurements are performed to understand the underlying photophysical mechanism. Our results indicate that the reduced hole relaxation rate from the arm to the quantum dot core can enhance the emission from the CdS arms, which is favorable for EL color tuning. This study provides a novel method to realize voltage-tunable EL colors with potential in display and micro-optoelectronic applications.

On the mechanism of intermolecular nitrogen-atom transfer from a lattice-isolated diruthenium nitride intermediate.

Catalyst confinement within microporous media provides the opportunity to site isolate reactive intermediates, enforce intermolecular functionalization chemistry by co-localizing reactive intermediates and substrates in molecular-scale interstices, and harness non-covalent host-guest interactions to achieve selectivities that are complementary to those accessible in solution. As part of an ongoing program to develop synthetically useful nitrogen-atom transfer (NAT) catalysts, we have demonstrated intermolecular benzylic amination of toluene at a Ru2 nitride intermediate confined within the interstices of a Ru2-based metal-organic framework (MOF), Ru3(btc)2X3 (btc = 1,3,5-benzenetricarboxylate, i.e., Ru-HKUST-1 for X = Cl). Nitride confinement within the extended MOF lattice enabled intermolecular C-H functionalization of benzylic C-H bonds in preference to nitride dimerization, which was encountered with soluble molecular analogues. Detailed study of the kinetic isotope effects (KIEs, i.e., kH/kD) of C-H amination, assayed both as intramolecular effects using partially labeled toluene and as intermolecular effects using a mixture of per-labeled and unlabeled toluene, provided evidence for restricted substrate mobility on the time scale of interstitial NAT. Analysis of these KIEs as a function of material mesoporosity provided approximate experimental values for functionalization in the absence of mass transport barriers. Here, we disclose a combined experimental and computational investigation of the mechanism of NAT from a Ru2 nitride to the C-H bond of toluene. Computed kinetic isotope effects for a H-atom abstraction (HAA)/radical rebound (RR) mechanism are in good agreement with experimental data obtained for C-H amination at the rapid diffusion limit. These results provide the first detailed analysis of the mechanism of intermolecular NAT to a C-H bond, bolster the use of KIEs as a probe of confinement effects on NAT within MOF lattices, and provide mechanistic insights unavailable by experiment because rate-determining mass transport obscured the underlying chemical kinetics.

Structure, reactivity, and spectroscopy of nitrogenase-related synthetic and biological clusters.

The reduction of dinitrogen (N2) is essential for its incorporation into nucleic acids and amino acids, which are vital to life on earth. Nitrogenases convert atmospheric dinitrogen to two ammonia molecules (NH3) under ambient conditions. The catalytic active sites of these enzymes (known as FeM-cofactor clusters, where M = Mo, V, Fe) are the sites of N2 binding and activation and have been a source of great interest for chemists for decades. In this review, recent studies on nitrogenase-related synthetic molecular complexes and biological clusters are discussed, with a focus on their reactivity and spectroscopic characterization. The molecular models that are discussed span from simple mononuclear iron complexes to multinuclear iron complexes and heterometallic iron complexes. In addition, recent work on the extracted biological cofactors is discussed. An emphasis is placed on how these studies have contributed towards our understanding of the electronic structure and mechanism of nitrogenases.

Ozone Attenuated H9c2 Cell Injury Induced by Doxorubicin.

ABSTRACT: Doxorubicin (DOX) is a commonly used drug in the treatment of cancers, whereas its application in the clinical stage is restricted because of side effects such as cardiomyocyte injury. Increasing studies indicated that ozone may protect cardiomyocytes from injuries. This study aimed to explore the effects of ozone on cardiotoxicity induced by DOX treatment. Rat heart myoblasts (H9c2) were treated with increasing concentrations of DOX (0.5, 1, 1.5, and 2 µM) to induce cell injury. 3-(4,5)-dimethylthiahiazo(-2)-3,5-diphenytetrazoliumromide assay and flow cytometry analysis were used to measure the viability and apoptosis of H9c2 cells. The mRNA and protein levels of proinflammatory cytokines [tumor necrosis factor-α (TNF-α), interleukin-(IL)1ß, and IL-6, matrix metalloproteinases (MMP-2 and MMP-9), and the key factors on the TLR4/NF-kB signaling (TLR4, p-p65, and p65) were measured by reverse transcription quantitative polymerase chain reaction, enzyme-linked immunosorbent assay, and western blot. The result showed that DOX promoted apoptosis and increased the expression of TNF-α (by 3.65-fold changes), IL-1ß (by 4.98-fold changes), IL-6 (by 3.44-fold changes), MMP-2 (by 1.98-fold changes), and MMP-9 (by 1.98-fold changes) levels in H9c2 cells. Moreover, the introduction of ozone reversed these changes in gene expression and suppressed the activation of the TLR4/NF-kB signaling, which indicated that ozone may exert protective effects on H9c2 heart myoblasts by relieving the cardiotoxicity induced by DOX. Our study provides theoretical basis for the significance of ozone in managing doxorubicin-induced H9c2 heart myoblast injury.

Mechanochemistry of Group 4 Element-Based Metal-Organic Frameworks.

Mechanochemical synthesis is emerging as an environmentally friendly yet efficient approach to preparing metal-organic frameworks (MOFs). Herein, we report our systematic investigation on the mechanochemical syntheses of Group 4 element-based MOFs. The developed mechanochemistry allows us to synthesize a family of Hf4O4(OH)4(OOC)12-based MOFs. Integrating [Zr6O4(OH)4(OAc)12]2 and [Hf6O4(OH)4(OAc)12]2 under the mechanochemical conditions leads to a unique family of cluster-precise multimetallic MOFs that cannot be accessed by the conventional solvothermal synthesis. Extensive efforts have not yielded an effective pathway for preparing TiIV-derived MOFs, tentatively because of the relatively low Ti-O bond dissociation energy.

Solar to hydrocarbon production using metal-free water-soluble bulk heterojunction of conducting polymer nanoparticle and graphene oxide.

This work demonstrates the first example of interfacial manipulation in a hybrid photocatalyst based on poly(3-hexylthiophene-2,5-diyl) (P3HT) nanoparticle and graphene oxide (GO) bulk heterojunctions to efficiently reduce CO2 into selective industrial hydrocarbons under gas-phase reaction and visible-light illumination. High selectivity of chemical products (methanol and acetaldehyde) was observed. Moreover, the hybrid photocatalyst's solar-to-fuel conversion efficiency was 13.5 times higher than that of pure GO. The increased production yield stems from the co-catalytic and sensitizing role of P3HT in the hybrid system due to its ability to extend light absorption to the visible range and improve interfacial charge transfer to GO. The hybrid P3HT-GO formed a type II heterojunction, and its static and dynamic exciton behaviors were examined using fluorescence spectroscopy and exciton lifetime mapping. A reduced fluorescence decay time was observed by interfacial manipulation for improved dispersion, indicating a more efficient charge transfer from the excited P3HT to GO. Thus, the conducting polymer nanoparticles, 2D nanocarbon, have demonstrated superior performance as a metal-free, non-toxic, low-cost, and scalable heterogeneous photocatalyst for CO2 reduction to solar fuel, a solid-gas system.

Radiative lifetime measurement of ultracold cesium Rydberg states by a simplified optical pumping method.

We demonstrate one simplified all-optical method to measure the radiative lifetime of ultracold cesium (Cs) Rydberg atoms. This method is based on photodetection of one ground state atomic absorption in a ladder-type electromagnetic induced transparency (EIT), which contains one ground state, one intermediate state, and one Rydberg state. In the presence and absence of optical pumping between the Rydberg state and the intermediate state, the absorption difference with varying delay time can reconstruct the population evolution of target Rydberg atoms. By using this method, the radiative lifetimes of 50S1/2 and 50D5/2 of Cs atoms are measured to be 53(9)µs and 42(9)µs, respectively, which are consistent with theoretical calculations. The agreements show the reliability of our presented method, which can provide a route for researching light-matter interaction behavior without the need to quantify absorption characteristic.

Concurrent Validity and Reliability of a Handheld Dynamometer in Measuring Isometric Shoulder Rotational Strength.

CONTEXT: Measuring isometric shoulder rotational strength is clinically important for evaluating motor disability in athletes with shoulder injuries. Recent evidence suggests that handheld dynamometry may provide a low-cost and portable method for the clinical assessment of isometric shoulder strength. OBJECTIVE: To investigate the concurrent validity and the intrarater and interrater reliability of handheld dynamometry for measuring isometric shoulder rotational strength. DESIGN: Cross-sectional study. SETTING: Biomechanics laboratory. PARTICIPANTS: Thirty-nine young, healthy participants. MAIN OUTCOME MEASURES: The peak isometric strength of the internal rotators and external rotators, measured by handheld dynamometry (in newton) and isokinetic dynamometry (in newton meter). INTERVENTIONS: Maximal isometric shoulder rotational strength was measured as participants lay supine with 90° shoulder abduction, neutral rotation, 90° elbow flexion, and forearm pronation. Measurements were performed independently by 2 different physiotherapists and in 3 different sessions to evaluate interrater and intrarater reliability. The data obtained by handheld dynamometry were compared with those obtained by isokinetic testing to evaluate concurrent validity. RESULTS: The intraclass correlation coefficients for interrater reliability in measuring maximum isometric shoulder external and internal rotation strength were .914 (95% confidence interval [CI], .842-.954) and .842 (95% CI, .720-.914), respectively. The intrarater reliability values of the method for measuring maximal shoulder external and internal rotation strength were 0.865 (95% CI, 0.757-0.927) and 0.901 (95% CI, 0.820-0.947), respectively. The Pearson correlation coefficients between the handheld and isokinetic dynamometer measurements were .792 (95% CI, .575-.905) for external rotation strength and .664 (95% CI, .419-.839) for internal rotation strength. CONCLUSIONS: The handheld dynamometer showed good to excellent reliability and moderate to good validity in measuring maximum isometric shoulder rotational strength. Therefore, handheld dynamometry could be acceptable for health and sports professionals in field situations to evaluate maximum isometric shoulder rotational strength.

Effect of Zinc-Doping on the Reduction of the Hot-Carrier Cooling Rate in Halide Perovskites.

The fast hot-carrier cooling process in the solar-absorbers fundamentally limits their photon-conversion efficiencies. It is highly desirable to develop a solar absorber with long-lived hot-carriers at sun-illumination intensity, which can be used to develop the hot-carrier solar cells with enhanced efficiency. Herein, we reveal that zinc-doped (0.34 %) halide perovskites have the slower hot-carrier cooling compared with the pristine sample through the transient absorption spectroscopy measurements and theoretical calculations. The hot-carrier energy loss rate at the low photoexcitation level of 1017  cm-3 is found to be ≈3 times smaller than that of un-doped perovskites for T=500 K hot carriers, and up to ten times when the hot-carrier temperature approaches the lattice temperature. The incorporation of zinc-dopant into perovskites can reduce the nonadiabatic couplings between conduction bands, which retards the photogenerated hot-carriers relaxation processes. Our findings present a practical strategy to slow down the hot-carrier cooling in perovskites at low carrier densities, which would be invaluable for the further development of practical hot-carrier photovoltaics based on perovskites.

Longitudinal Changes in the Cerebral Cortex Functional Organization of Healthy Elderly.

Healthy aging is accompanied by disruptions in the functional modular organization of the human brain. Cross-sectional studies have shown age-related reductions in the functional segregation and distinctiveness of brain networks. However, less is known about the longitudinal changes in brain functional modular organization and their associations with aging-related cognitive decline. We examined age- and aging-related changes in functional architecture of the cerebral cortex using a dataset comprising a cross-sectional healthy young cohort of 57 individuals (mean ± SD age, 23.71 ± 3.61 years, 22 males) and a longitudinal healthy elderly cohort of 72 individuals (mean ± baseline age, 68.22 ± 5.80 years, 39 males) with 2-3 time points (18-24 months apart) of task-free fMRI data. We found both cross-sectional (elderly vs young) and longitudinal (in elderly) global decreases in network segregation (decreased local efficiency), integration (decreased global efficiency), and module distinctiveness (increased participation coefficient and decreased system segregation). At the modular level, whereas cross-sectional analyses revealed higher participation coefficient across all modules in the elderly compared with young participants, longitudinal analyses revealed focal longitudinal participation coefficient increases in three higher-order cognitive modules: control network, default mode network, and salience/ventral attention network. Cross-sectionally, elderly participants also showed worse attention performance with lower local efficiency and higher mean participation coefficient, and worse global cognitive performance with higher participation coefficient in the dorsal attention/control network. These findings suggest that healthy aging is associated with whole-brain connectome-wide changes in the functional modular organization of the brain, accompanied by loss of functional segregation, particularly in higher-order cognitive networks.SIGNIFICANCE STATEMENT Cross-sectional studies have demonstrated age-related reductions in the functional segregation and distinctiveness of brain networks. However, longitudinal aging-related changes in brain functional modular architecture and their links to cognitive decline remain relatively understudied. Using graph theoretical and community detection approaches to study task-free functional network changes in a cross-sectional young and longitudinal healthy elderly cohort, we showed that aging was associated with global declines in network segregation, integration, and module distinctiveness, and specific declines in distinctiveness of higher-order cognitive networks. Further, such functional network deterioration was associated with poorer cognitive performance cross-sectionally. Our findings suggest that healthy aging is associated with system-level changes in brain functional modular organization, accompanied by functional segregation loss particularly in higher-order networks specialized for cognition.

In Crystallo Snapshots of Rh2-Catalyzed C-H Amination.

While X-ray crystallography routinely provides structural characterization of kinetically stable pre-catalysts and intermediates, elucidation of the structures of transient reactive intermediates, which are intimately engaged in bond-breaking and -making during catalysis, is generally not possible. Here, we demonstrate in crystallo synthesis of Rh2 nitrenoids that participate in catalytic C-H amination, and we characterize these transient intermediates as triplet adducts of Rh2. Further, we observe the impact of coordinating substrate, which is present in excess during catalysis, on the structure of transient Rh2 nitrenoids. By providing structural characterization of authentic C-H functionalization intermediates, and not kinetically stabilized model complexes, these experiments provide the opportunity to define critical structure-activity relationships.

Redox Communication between Two Diarylamido/Bis(phosphine) (PNP)M Moieties Bridged by Ynediyl Linkers (M = Ni, Pd, Pt).

A series of binuclear homo- and heterobimetallic complexes of the general type (PNP)M-[linker]-M(PNP) have been prepared (M = Ni, Pd, Pt; PNP = a diarylamido/bis(phosphine) pincer ligand; -[linker]- = -C≡C-, -C≡CC≡C-, -C≡CC6H4C≡C-). Each (PNP)M site can be oxidized by one electron, and this work reports the investigation of the mixed-valence behavior in terms of the communication between the two redox sites and the degree of the delocalization in the monooxidized cation. The compounds were evaluated using cyclic voltammetry, UV-vis-NIR and EPR spectroscopy, X-ray crystallography, and DFT calculations. The complex with the longest examined linker, (PNP)Ni-C≡CC6H4C≡C-Ni(PNP) (9Ni), exhibited no discernible communication between the redox sites. The homobimetallic complexes (PNP)M-C≡CC≡C-M(PNP) (6M) displayed a lower degree of communication in comparison to the -C≡C- linker analogues (PNP)M-C≡C-M(PNP) (3M). Within each of these two subsets, the relative degree of communication and delocalization was determined to be Pd < Ni ≤ Pt. On the Robin-Day scale, compounds 6M can be assigned class I for M = Pd and class II for M = Ni, Pt. Complex 3Pd also falls into class II, while 3Ni and 3Pt may be viewed as borderline class II/III cases. It is likely that the communication in the Ni systems has the advantage of the smaller size of Ni, resulting in a greater physical proximity of the redox sites, while the 5d metal Pt possesses the greatest ability for orbital interaction with the -C≡C- linker.

ZnO nanoflowers modified with RuO2 for enhancing acetone sensing performance.

Surface modification is a simple and effective means to promote the sensing performance of metal oxide semiconductor-based gas sensors. Marigold-shaped ZnO nanoflowers are fabricated via a simple precipitation reaction and subsequently catalytically modified with RuO2 on the surface through an ethylene glycol solvothermal treatment. The experimental results have proven that a very low content of Ru on the surface of ZnO exists in an oxidized state. However, the gas response of the sensor based on RuO2-modified ZnO is remarkably improved by 17 times to 100 ppm acetone with the decrease of optimal operating temperature from 219 °C-172 °C and reduction in recovery time from 79-52 s. The sensing enhancement mechanism of surface modification can be attributed to the formation of massive small heterostructure between p-type RuO2 ultrasmall nanoparticles and n-type ZnO as well as the catalytic effect of Ru4+ and a rougher surface.

Atomically Precise Crystalline Materials Based on Kinetically Inert Metal Ions via Reticular Mechanopolymerization.

Atomistic control of the coordination environment of lattice ions and the distribution of metal sites within crystalline mixed-metal coordination polymers remain significant synthetic challenges. Herein is reported the mechanochemical synthesis of a reticular family of crystalline heterobimetallic metal-organic frameworks (MOFs) is now achieved by polymerization of molecular Ru2 [II,III] complexes, featuring unprotected carboxylic acid substituents, with Cu(OAc)2 . The resulting crystalline heterobimetallic MOFs are solid solutions of Ru2 and Cu2 sites housed within [M3 L2 ] phases. The developed mechanochemical strategy is modular and allows for systematic control of the primary coordination sphere of the Ru2 sites within an isoreticular family of materials. This strategy is anticipated to provide a rational approach to atomically precise mixed-metal materials.

Measuring and Modulating Substrate Confinement during Nitrogen-Atom Transfer in a Ru2-Based Metal-Organic Framework.

The porosity and synthetic tunability of metal-organic frameworks (MOFs) has motivated interest in application of these materials as designer heterogeneous catalysts. While understanding substrate mobility in these materials is critical to the rational development of highly active catalyst platforms, experimental data are rarely available. Here we demonstrate kinetic isotope effect (KIE) analysis enables direct evaluation of the extent of substrate confinement as a function of material mesoporosity. Further, we provide evidence that suggests substrate confinement within a microporous Ru2-based MOF gives rise to quantum tunneling during interstitial C-H amination. The reported data provide the first evidence for tunneling during interstitial MOF chemistry and illustrate an experimental strategy to evaluate the impact of material structure on substrate mobility in porous catalysts.

Repression of adipose vascular endothelial growth factor reduces obesity through adipose browning.

Obesity is the result of excessive energy accumulation and is associated with many diseases. We previously reported that universal repression of vascular endothelial growth factor (VEGF) leads to brown-like adipocyte development in white adipose tissues, and that these mice are resistant to obesity (Lu X et al. Endocrinology 153: 3123-3132, 2012). Using an adipose-specific VEGF repression mouse model (aP2-rtTR-krabtg/+/VEGFtetO/tetO), we show that adipose-specific VEGF repression can repeat the previous phenotypes, including adipose browning, increased energy consumption, and reduction in body weight. Expression of brown adipose-associated genes is increased, and white adipose-associated genes are downregulated under VEGF repression. Our study demonstrates that adipose-specific VEGF repression can lead to antiobesity activity through adipose browning and has potential clinical value.

In Operando Analysis of Diffusion in Porous Metal-Organic Framework Catalysts.

The potential to exert atomistic control over the structure of site-isolated catalyst sites, as well as the topology and chemical environment of interstitial pore spaces, has inspired efforts to apply porous metal-organic frameworks (MOFs) as catalysts for fine chemical synthesis. In analogy to enzyme-catalyzed reactions, MOF catalysts have been proposed as platforms in which substrate confinement could be used to achieve chemo- and stereoselectivities that are orthogonal to solution-phase catalysts. In order to leverage the tunable pore topology of MOFs to impact catalyst selectivity, catalysis must proceed at interstitial catalyst sites, rather than at solvent-exposed interfacial sites. This Minireview addresses challenges inherent to interstitial MOF catalysis by 1) describing the diffusional processes available to sorbates in porous materials, 2) discussing critical factors that impact the diffusion rate of substrates in porous materials, and 3) presenting in operando experimental strategies to assess the relative rates of substrate diffusion and catalyst turnover in MOF catalysis. It is anticipated that the continued development of in operando tools to evaluate substrate diffusion in porous catalysts will advance the application of these materials in fine chemical synthesis.