Chain Distortion Research Articles

Organization of Carotenoid Aggregates in Membranes Studied Selectively using Resonance Raman Optical Activity.

In living organisms, carotenoids are incorporated in biomembranes, remarkably modulating their mechanical characteristics, fluidity, and permeability. Significant resonance enhancement of Raman optical activity (ROA) signals of carotenoid chiral aggregates makes resonance ROA (RROA), a highly selective tool to study exclusively carotenoid assemblies in model membranes. Hence, RROA is combined with electronic circular dichroism (ECD), dynamic light scattering (DLS), molecular dynamics, and quantum-chemical calculations to shed new light on the carotenoid aggregation in dipalmitoylphosphatidylcholine (DPPC) liposomes. Using representative members of the carotenoid family: apolar α-carotene and more polar fucoxanthin and zeaxanthin, the authors demonstrate that the stability of carotenoid aggregates is directly linked with their orientation in membranes and the monomer structures inside the assemblies. In particular, polyene chain distortion of α-carotene molecules is an important feature of J-aggregates that show increased orientational freedom and stability inside liposomes compared to H-assemblies of more polar xanthophylls. In light of these results, RROA emerges as a new tool to study active compounds and drugs embedded in membranes.

Morphological and molecular control of chemical vapor deposition (CVD) polymerized polythiophene thin films.

Oxidative chemical vapor deposition (oCVD) has emerged as one of the most promising techniques for conjugated polymer deposition, especially for unsubstituted polythiophene thin films. oCVD overcomes the insolubility challenge that unsubstituted polythiophene (PT) presents and adds the ability to control morphological and molecular structure. This control is important for enhancing the performance of devices which incorporate organic conductors. In this work, Raman spectroscopy, UV-vis spectroscopy, and AFM reveal that the relative amount of distortion in the polymer chains, the conjugation length and the film roughness are all affected by the CVD deposition conditions, in particular the reactor pressure. PT films deposited at 150 mT and 300 mT are found to have lower chain distortion, longer conjugation lengths and lower surface roughness compared to other deposition pressures. The oCVD PT film is also directly grafted to the trichloro(phenylethyl)silane (PTS) treated substrates, where the effect of PTS grafting is observed to significantly affect film roughness. In addition, we report the first study of the effect of oCVD PT films on the performance of lithium-ion battery electrodes. These oCVD PT films are used to engineer a LiCoO2 cathode in lithium-ion batteries. The observed improvements are a 52% increase in the discharge capacity (67 mA h g-1 to 102 mA h g-1) at 10C and a 500% improvement in cycling stability tested at 5C within the voltage range of 3.0-4.5 V (capacity fading rate is reduced from 1.92%/cycle to 0.32%/cycle).

Fluctuating Ru trimer precursor to a two-stage electronic transition in RuP

Superconductivity in binary ruthenium pnictides occurs proximal to and upon suppression of a nonmagnetic ground state, preceded by a pseudogap phase associated with Fermi surface instability, and its critical temperature, ${T}_{c}$, is maximized around the pseudogap quantum critical point. By analogy with isoelectronic iron-based counterparts, antiferromagnetic fluctuations became ``usual suspects'' as putative mediators of superconducting pairing. Here we report on a high-temperature local symmetry breaking in RuP, the nonsuperconducting parent of the maximum-${T}_{c}$ branch of these novel superconductors, revealed by combined nanostructure-sensitive powder and single-crystal x-ray total scattering analyses. Large local distortions of Ru chains associated with orbital-charge trimerization, further assembled into hexamers, exist above the two-stage electronic transition in RuP. In the pseudogap regime the precursors order with distortions retaining their strength, whereas they acquire spin-singlet characteristics which dramatically enhances the distortion as the nonmagnetic ground state establishes. The precursors enable the nonmagnetic ground state and presumed complex oligomerization, and the relevance of pseudogap fluctuations for superconductivity emerges as a distinct prospect. As a transition metal system in which partial d-manifold filling combined with high crystal symmetry promotes electronic instabilities, this represents a further example of local electronic precursors underpinning the macroscopic collective behavior of quantum materials.

Luminescence and Dielectric Switchable Properties of a 1D (1,1,1-Trimethylhydrazinium)PbI3 Hybrid Perovskitoid.

The synthesis and investigation of the physicochemical properties of a novel one-dimensional (1D) hybrid organic-inorganic perovskitoid templated by the 1,1,1-trimethylhydrazinium (Me3Hy+) cation are reported. (Me3Hy)[PbI3] crystallizes in the hexagonal P63/m symmetry and undergoes two phase transitions (PTs) during heating (cooling) at 322 (320) and 207 (202) K. X-ray diffraction data and temperature-dependent vibrational studies show that the second-order PT to the high-temperature hexagonal P63/mmc phase is associated with a weak change in entropy and is related to weak structural changes and different confinement of cations in the available space. The second PT to the low-temperature orthorhombic Pbca phase that corresponds to the high change in entropy and dielectric switching is associated with an ordering of the trimethylhydrazinium cations, re-arrangement and strengthening of hydrogen bonds, and slightly shifted lead-iodide octahedral chains. The high-pressure Raman data revealed two additional PTs, one between 2.8 and 3.2 GPa, related to the symmetry decrease, ordering of the cations, and inorganic chain distortion, and the other in the 6.4-6.8 GPa range related to the partial and reversible amorphization. Optical studies revealed that (Me3Hy)[PbI3] has a wide band gap (3.20 eV) and emits reddish-orange excitonic emission at low temperatures with an activation energy of 65 meV.

Patients Access to Medicines - A Critical Review of the Healthcare System in Kenya.

Access to affordable, safe, effective, and quality-assured medicines by a patient is important for good health outcomes. Unfortunately, there is sparse literature published on the pharmaceutical enablers that may increase the sale of a substandard and falsified (SF) medicine to a patient in Kenya. The review highlights some of the factors that may facilitate the entry of SF medicines into the legitimate pharmaceutical supply chain and discusses their impact on patient access to medicines. Lack of essential medicines in public health facilities is an important factor that may contribute to increased demand for medicine-related out-of-pocket expenses from private health facilities, thus a likelihood for a patient purchasing SF medicine from unlicensed and illegal medicine outlets or unregulated websites. The need to increase medicine availability in the public sector by the Ministry of Health (MOH) is emphasized in addition to the strengthening of public procurement to cushion it from corruption and mismanagement. In addition, the MOH should promote local pharmaceutical manufacturing and implement a medicine pricing containment policy to avoid abuse and prevent overexploitation of patients, increase medicine price transparency, and reduce pharmaceutical supply chain distortion. Recommended regulatory reviews include accreditation of unlicensed illegal medicine outlets to facilitate accountability, regulatory oversight, and active surveillance. The national post-market surveillance regulatory capacity should be strengthened to improve rational medicine use. A 3-year diploma course should be replaced with a shorter 1- or 2-year pharmaceutical support staff training not eligible to superintend a pharmacy. The recommended legislative review includes a mandatory clause to enforce generic prescribing and the implementation of generic substitution by health workers. Unethical manipulative pharmaceutical marketing practices should carry stiffer penalties to deter malpractice. Future research areas include investigation of medicine prescribing and dispensing practices, medicine consumption studies, medicine price differences within different health sub-sectors, and between licensed pharmacies and unlicensed illegal medicine outlets.

Effect of Bulky Atom Substitution on Backbone Coplanarity and Electrical Properties of Cyclopentadithiophene‐Based Semiconducting Polymers

Front Cover: In article number 2100709 by Byoung Hoon Lee and co-workers, the effect of chlorine atom substitution on the optoelectronic properties of cyclopentadithiophene-based donor–acceptor π-conjugated polymers is investigated. The chlorine atom substitution leads to deteriorated optical and electrical properties of the polymer due to chain distortion as a consequence of steric hindrance adjacent to the chlorine atoms.

Self-assembly of 1D FeSe2 chains and Fe(dien)2 complexes for ferrimagnetic inorganic-organic hybrid cuboids

Challenges still remain in producing room-temperature ferromagnetism/ferrimagnetism in inorganic–organic hybrid compounds. Here, we report the Fe vacancy-doped inorganic–organic (FexSe2)2Fe(dien)2 (dien = diethylenetriamine, x = 0.86) hybrid cuboids by self-assemble of finite one-dimensional (1D) FeSe2 chains and Fe(dien)2 complexes. A growth model is proposed by kinetically controllable syntheses of novel Fe2x+1Se4(dien)2 hybrids. The Rietveld refinement reveals that Fe vacancies in the Fe2.71Se4(dien)2 hybrid cuboids induce large distortions of the FeSe2 chains and the room-temperature lattice parameters are a = 9.225(4) Å, b = 18.021(8) Å and c = 11.609(6) Å. Magnetic measurements and electron spin resonance spectra of the Fe2.71Se4(dien)2 hybrid cuboids show the ferrimagnetism with the Curie temperature (TC) of 600 K and the spin glass state with the freezing temperature (Tf) of 108 K. Impressive room-temperature ferrimagnetic properties of the Fe2.71Se4(dien)2 hybrid cuboids were ascribed to the high concentration of Fe3+ vacancies (0.29 per cell) in the hybrid cuboids, which is supported by the 57Fe Mössbauer spectrum fitting based on the ferrimagnetic model.

Confined Crystallization and Melting Behaviors of 3-Pentadecylphenol in Anodic Alumina Oxide Nanopores.

To explore the effects of end groups on the confined crystallization of an alkyl chain, 3-pentadecylphenol (PDP) was infiltrated into the anodic aluminum oxide template (AAO) to investigate the melting and crystallization behaviors of PDP in a nanoconfined environment. Wide-angle X-ray diffraction (WAXD) found that the solid–solid phase transition of PDP occurred under confined conditions, and the absence of the (00L) reflections indicated that the stacking of the end groups of the alkyl chain layered structure was seriously disturbed. Thermal analysis (TG) showed that the thermal stability of the confined samples decreased due to the confinement effect, and the introduction of end groups made the confinement effect more obvious. Differential scanning calorimeter (DSC) results well reflected the space–time equivalence in the PDP crystallization processes, i.e., the solid–solid phase transition can be achieved by reducing the cooling rate or confining PDP in the nanometer space. Compared with C15, the introduction of the end groups with a phenol ring led to the disappearance of the solid–solid phase transition of an alkyl chain at high cooling rates. In the confined environment, the introduction of the end groups with a phenol ring caused the melting double peaks of the alkyl chain to become a single melting peak, and it also caused the disappearance of the surface freezing monolayer for alkyl chains. Through the analysis of crystallinity, it was found that AAO-PDP was more sensitive to AAO pore size changes than AAO-C15, the Xc of AAO-PDP had a good linear relationship with the pore size d, but the Xc of the AAO-C15 had a nonlinear relationship with the pore size d. Attenuated total reflection (ATR)-IR proved that in the confined environment, the order of the alkyl chain decreased and the degree of chain distortion increased.

Influences of Vibrio cholerae Lipid A Types on LPS Bilayer Properties

Lipopolysaccharides (LPS) present in the outer leaflet of Gram-negative bacterial outer membranes protect the bacteria from external threats and influence antibiotic permeability as well as immune system recognition. The structure of lipid A, the anchor of an LPS molecule to the outer membrane, can make direct influences on membrane properties. Particularly, in Vibrio cholerae, a Gram-negative bacterium responsible for cholera, a severe diarrheal disease, modifications of lipid A structures grant antibiotic resistance and are a primary factor that led to the current cholera pandemic. However, the difference in structural properties incurred by such modifications has not been fully explored. In this work, five symmetric bilayer systems comprised of distinct lipid A structures of Vibrio cholerae LPS with O1 O-antigen were modeled and simulated to explore influences of different lipid A types on membrane properties. All-atom molecular dynamics simulations reveal that membrane properties such as hydrophobic thickness, acyl chain order parameter, and area per lipid are largely impacted by lipid A modifications due to differences in composition and acyl chain distortions. The modified lipid A is also less negatively charged, which possibly reveals a resistance mechanism to cationic antimicrobial peptide evasion. These findings present a possible explanation for Vibrio cholerae's immune system evasion properties and establish the differences between the lipid A types, which should be of use for any future study of the Gram-negative bacteria.

Multiuser Full-Duplex Relaying: Enabling Dual Connectivity via Impairments-Aware Successive Interference Cancellation

In this article, we consider the downlink of a cellular communication network, where dual-connectivity at the end-users is enabled with the assistance of a full-duplex (FD) massive-multiple-input-multiple-output (mMIMO) relay. In particular, the base station transmits separate data streams through the cochannel direct link as well as the FD relay channel, utilizing the successive-interference-cancellation (SuIC) capability at the receiver. As a result, the downlink communication data can be interchangeably loaded to separate subcarriers, employing an orthogonal multicarrier strategy, or to different available links, i.e., direct or FD relay link, employing the nonorthogonal SuIC at the receiver. In order to reliably model the SuIC operation at the receiver, the collective sources of impairments, including the nonlinear transmit and receiver chain distortions as well as the channel state information inaccuracy are incorporated. An optimization problem for joint subcarrier and power allocation is then devised in order to maximize system sum-rate, which belongs to the class of smooth difference-of-convex problems. An iterative optimization solution is then proposed, utilizing successive inner approximation framework, which converges to the point that satisfies Karush–Kuhn–Tucker optimality conditions. Numerical results show performance and robustness gain of proposed SuIC scheme in terms of sum-rate compared to previously proposed single-connectivity and half-duplex relaying schemes.

Conformational disorder of organic cations tunes the charge carrier mobility in two-dimensional organic-inorganic perovskites

The chemical nature of the organic cations governs the optoelectronic properties of two-dimensional organic-inorganic perovskites. But its mechanism is not fully understood. Here, we apply femtosecond broadband sum frequency generation vibrational spectroscopy to investigate the molecular conformation of spacer organic cations in two-dimensional organic-inorganic perovskite films and establish a correlation among the conformation of the organic cations, the charge carrier mobility, and broadband emission. Our study indicates that both the mobility and broadband emission show strong dependence on the molecular conformational order of organic cations. The gauche defect and local chain distortion of organic cations are the structural origin of the in-plane mobility reduction and broad emission in two-dimensional organic-inorganic perovskites. Both of the interlayer distance and the conformational order of the organic cations affect the out-of-plane mobility. This work provides molecular-level understanding of the conformation of organic cations in optimizing the optoelectronic properties of two-dimensional organic-inorganic perovskites.

The Effect of Covid-19 on SMEs and Entrepreneurial Resilience in Ethiopia. A Case of Nekemte Town

The effect of COVID-19 crisis on economy is due to public health measures to flatten the epi-curve. Even though, the crisis affects all economic sectors, the economic fallout from COVID-19 pandemics is particularly is acute in specific sectors such as SMEs. Studies indicate that SMEs may experience supply chain distortions due to irregular supply of raw materials and intermediate goods, revenue loss and shortage of liquidity to continue business operations. And also enterprises experienced a reduction in production / work activity/ contracts due to corona virus outbreak. DOI: 10.7176/RHSS/10-11-01 Publication date: June 30th 2020

System dynamics analysis of supply chain financial management during capacity expansion

Purpose This study aims to describe in detail, a system dynamics-based study that was used to show how a large vertically integrated aquaculture company should approach its stepwise capacity expansion program, without undermining its financial performance or affecting the performance of the value chain. Design/methodology/approach The company and its aquaculture value chain are used as case study. A system dynamics model is developed on the basis of generic end-to-end agribusiness and aquaculture supply chain models. The model includes the unique dynamics relating to an aquaculture supply chain. Also modelled is the working capital management rules of the company, with the effects of the capacity expansion program on its working capital, market share and its supply chain obligations. The model is used to determine the long-term impact of the company’s working capital management under different modes of financing and rate of expanding the capacity. Findings For a large vertically integrated company that wants to increase its capacity, there is a systematic approach to working capital management that can be used to avoid financial distress or value chain distortion. Research limitations/implications Extended the scope of system dynamics modelling within multiple disciplines, namely, agribusiness supply chain finance, supply chain capacity investment, financial management in large companies, supply chain working capital management and aquaculture value chain. Practical implications The developed model can be used to manage supply chain working capital in large vertically integrated agribusinesses, and also to assess supply chain financial risk. Originality/value To enhance the model build, discrete event simulation was used to model aspects of the system. The eventual system dynamics-discrete event simulation model is a form of hybrid simulation modelling that was used to provide a deeper understanding of how supply chain financial decisions affect an entire value chain system.

Intrinsic high thermal conductive co-polyester based on offset π-π stacking

It has been known that phonon mean free path along polymer chains is much larger than in transverse directions because weak interaction between polymer chains leads to chain distortion and entanglement. In order to improve intensity of intermolecular interaction, a series of co-polyesters (CPE) containing different content of offset π-π stacking structure in side chains were synthesized by means of polycondensation and transesterification in this work. WAXD patterns unfolded diffraction peak at 2θ of 27.6°, standing for structure of offset π-π stacking. On enlarging intensity of offset π-π stacking interaction, specific heat capacity of CPE increased from 1.140 Jg−1K−1 to 1.410 Jg−1K−1 and thermal diffusivity rose from 0.194mm2s−1 to 0.245mm2s−1. As a result, CPE sample exhibited excellent thermal conductivity (TC) of 0.381 Wm−1K−1, which is around twice that of traditional thermoplastics. Hence offset π-π stacking interaction could strengthen capacity of heat absorption and thermal conduction at the same time, which might be a good candidate for enhancing thermal conductivity of intrinsic polymers. Furthermore, strong π-π interaction in side chains could maintain modulus when temperature is over glass temperature. And the Young modulus grew from 0.14 GPa to 0.44 GPa with the augment of offset π-π stacking structure.

Synthesis and properties of hyperbranched polymers for polymer light emitting devices with sunlight-style white emission.

A new series of hyperbranched polymers consisting of fluorene-alt-carbazole as the branches and the three-dimensional-structured spiro[3.3]heptane-2,6-dispirofluorene (SDF) as the core were designed and synthesized by one-pot Suzuki coupling polycondensation. A phosphor group with broad full width at half maximum (FWHM) bis(1-phenyl-isoquinoline)(acetylacetonato)iridium(iii) (Ir(Brpiq)2acac, 0.08 mol%) as the red-light emitting unit and bis(2-(4-bromophenyl)-1-[6-(9-carbazolyl)hexyl]-imidazole)(2-(5-(4-fluorinated phenyl)-1,3,4-triazole)pyridine)iridium(iii) ((CzhBrPI)2Ir(fpptz)) as the green-light emitting unit were introduced into the backbones to obtain sunlight-style white-light emission by adjusting the feeding ratios of (CzhBrPI)2Ir(fpptz) (0.08 to 0.32 mol%). The results indicate the synthesized polymers show high thermal stabilities and good amorphous film morphology because of the hyperbranched structures. Besides, the lowest unoccupied molecular orbital (LUMO) levels of polymers were reduced and the electron injection was improved because of excellent electron-transporting ability of the triazole unit in the green group. The hyperbranched structures can effectively suppress the polymers' chain distortion and aggregation, and promote the incomplete Förster resonance energy transfer (FRET) efficiency from fluorene-alt-carbazole segments to Ir complex units. As a result, the devices with hyperbranched polymer light-emitting layers realize white light emission, and the optimized device also exhibits good electroluminescent (EL) performance with Commission Internationale de l'Eclairage (CIE) coordinates at (0.32, 0.31), a maximum luminance of 9054 cd m−2, a maximum current efficiency of 3.59 cd A−1 and a maximum Color Rendering Index (CRI) of 91. The hyperbranched polymers based on fluorene-alt-carbazole branches and a SDF core and high-efficiency phosphor groups with broad full width at half maximum are attractive candidates for sunlight-style white polymer light-emitting device.

Wide Magnetic Thermal Memory Effect (∼55 K) Above Room Temperature Coupled to a Structure Phase Transition of Lattice Symmetry Reduction in High-Temperature Phase in an S = 1/2 Spin Chain Molecule Crystal.

One-dimensional (1D) S = 1/2 Heisenberg antiferromagnetic (AFM) chain system shows frequently a spin-Peierls-type transition owing to strong spin-lattice coupling. From high-temperature phase (HTP) to low-temperature phase (LTP), the spin chain distortion leads to the reduction in lattice symmetry in LTP, called the symmetry breaking (SB) phase transition. Herein, we report the first example of 1D S = 1/2 AFM molecular crystal, [Et3( n-Pr)N][Ni(dmit)2] (Et3( n-Pr)N+ = triethylpropylammonium, dmit2- = 2-thioxo-1,3-dithiole-4,5-dithiolate), which shows a structural phase transition with lattice symmetry increase in LTP, which is contrary to the SB phase transition. Particularly, the structure phase transition leads to magnetically bistable state with TC↑ ≈ 375 K, TC↓ ≈ 320 K, and surprisingly large thermal hysteresis (∼55 K). Additionally, LTP and HTP coexist in a temperature region near TC but not at TC in this 1D spin system. The large hysteresis is related to the huge deformation of anion stack, which needs high activation energy for the structure transformation and magnetic transition between LTP and HTP. This study would not only provide new insight into the relationship of spin-Peierls-type transition and structure phase transition but also offer a roadmap for searching molecular-scale magnetic bistable materials, which are in huge demand in future electronic, magnetic, and photonic technologies.

Inclusive Innovation: Product Innovation in Technology Supply Chains

Problem definition: Managers introducing new innovative technological products frequently face the dual task of managing both revenues and profits. This task is made challenging in part because of the tendency of new technologies to traverse a sequentially downward path of gradually lowering costs and prices, which limits their initial availability and affordability, crimping market coverage and revenues. Academic/practical relevance: We focus on the product management challenge of juggling revenues and profits, show how it is amplified in a supply chain, and propose a new degree of freedom in a supply chain, namely innovation investment anchoring, that offers product managers and their firms the ability to expand market coverage and improve both revenues and profits. Methodology: We adopt a sequential game theory approach to analyze the investment anchor decision for various objectives from investments in innovation to market coverage to profit. Results: We find that the investment anchoring approach can lead to greater investments in innovation, revenues, and profits. We also compare the investment anchoring for two types of innovation, product quality improvement and cost reduction, and show that the investment anchoring is more effective for product quality improvement. Managerial implications: Our findings have subtle but important implications for firms launching innovative products and aspiring to expand product sales and profits. Specifically, innovating firms in a supply chain by broadening the quest for an investment anchor and offering them incentives to invest as well as fine tuning the level of innovation investment with the market context can make innovation more inclusive, alleviate supply chain distortions, and streamline revenues and profits. The online appendix is available at https://doi.org/10.1287/msom.2018.0746 . This paper has been accepted for the Manufacturing & Service Operations Management Special Issue on Value Chain Innovations in Developing Economies.

Structural Evolution of a Retinal Chromophore in the Photocycle of Halorhodopsin from Natronobacterium pharaonis.

We revealed the chloride ion pumping mechanism in halorhodopsin from Natronobacterium pharaonis ( pHR) by exploring sequential structural changes in the retinal chromophore during its photocycle using time-resolved resonance Raman (RR) spectroscopy on the nanosecond to millisecond time scales. A series of RR spectra of the retinal chromophore in the unphotolyzed state and of the three intermediates of pHR were obtained. Using singular value decomposition analysis of the C═C and C-C stretch bands in the time-resolved RR spectra, we identified the spectra of the K, L, and N intermediates. We focused on structural markers of the RR bands to explore the structure of the retinal chromophore. In the unphotolyzed state, the retinal chromophore is in the planar all- trans, 15- anti geometry. The bound ion affects the polyene chain but does not interact with the protonated Schiff base. In the observed intermediates, the chromophore is in the 13- cis configuration. The chromophore in the K intermediate is distorted due to the photoisomerization of retinal. The hydrogen bond is weak in the unphotolyzed state and in the K intermediate, resulting in exchange of the hydrogen-bond acceptor to a water molecule in the K-to-L transition, relaxation of the polyene chain distortion, and generation of an alternative distortion near the Schiff base. The bound halide ion interacts with the protonated Schiff base through the water molecule bound to the protonated Schiff base. In the L-to-N transition, the hydrogen acceptor of the protonated Schiff base switches from the water molecule to another species, although the strong hydrogen bond of the protonated Schiff base remains. This paper reports the first observation of sequential changes in the RR spectra in the pHR photocycle, provides information on the structural evolution of the retinal chromophore, and proposes a model for chloride ion translocation in pHR.

Structure and mechanical properties of boron-rich boron carbides

A series of boron-rich boron carbides are investigated to explore the effect of boron/carbon ratios on the microstructure and mechanical properties of the complex material. It has been found that excess boron substitution gives rise to expanded lattice constants, orientational asymmetry of the chain structure and distortion of the icosahedra of rhombohedra B4C units in comparison with conventional carbon-rich boron carbides. Microstructure characterization reveals a high density of stacking faults and growth twins in boron-rich boron carbides. Nanoindentation measurements demonstrate that the hardness and modulus of boron-rich boron carbides decrease with the increase of boron content while the B10.2C sample with the highest boron substitution shows relatively high hardness and modulus. This study suggests that the structure of single-phase covalent materials could be tailored by self-alloying for improved mechanical properties.

Charge Density Wave in the New Polymorphs of RE2Ru3Ge5 (RE = Pr, Sm, Dy).

A new polymorph of the RE2Ru3Ge5 (RE = Pr, Sm, Dy) compounds has been grown as single crystals via an indium flux. These compounds crystallize in tetragonal space group P4/mnc with the Sc2Fe3Si5-type structure, having lattice parameters a = 11.020(2) Å and c = 5.853(1) Å for RE = Pr, a = 10.982(2) Å and c = 5.777(1) Å for RE = Sm, and a = 10.927(2) Å and c = 5.697(1) Å for RE = Dy. These materials exhibit a structural transition at low temperature, which is attributed to an apparent charge density wave (CDW). Both the high-temperature average crystal structure and the low-temperature incommensurately modulated crystal structure (for Sm2Ru3Ge5 as a representative) have been solved. The charge density wave order is manifested by periodic distortions of the one-dimensional zigzag Ge chains. From X-ray diffraction, charge transport (electrical resistivity, Hall effect, magnetoresistance), magnetic measurements, and heat capacity, the ordering temperatures (TCDW) observed in the Pr and Sm analogues are ∼200 and ∼175 K, respectively. The charge transport measurement results indicate an electronic state transition happening simultaneously with the CDW transition. X-ray absorption near-edge spectroscopy (XANES) and electronic band structure results are also reported.