Large Ring Research Articles

ROSEN, BULGARIA: A NEWLY RECOGNIZED IRON OXIDE-COPPER-GOLD DISTRICT

AbstractThe Rosen copper veins in southeastern Bulgaria are recognized for the first time as an iron oxide-copper-gold (IOCG) district. The veins are located in the East Srednogorie segment of the Carpathian-Balkan calc-alkaline volcano-plutonic arc and were formed during an end-stage interval of extreme slab rollback and intra-arc rifting, which gave rise farther east to seafloor spreading in the Western Black Sea basin. The resulting submarine volcano-sedimentary rift basin is dominated by intermediate to mafic shoshonitic to ultrapotassic volcanism and subsidiary gabbro to syenite intrusion. The E- to NE-striking veins define a NW-striking alignment along the western contact of the syenite-dominated Rosen pluton, inferred to be part of a large ring dike. More than 40 veins, the most important formerly mined to depths as great as 1,000 m, contain an early, pegmatoidal, calcic-potassic assemblage followed by predominant magnetite (including the mushketovite variety), chlorite, and carbonates but also quartz, chalcopyrite, pyrite, and numerous other metallic minerals, which combine to give an unusual Fe-Cu-Au-Mo-Co-Ni-U-light rare earth element (LREE)-W-Bi-Zn-Pb geochemical signature. The close correlation between Fe, Cu, U, and LREEs is evident even in the flotation tailings. Vein molybdenite was dated during this study at 80.6 ± 0.4 Ma, which is similar to a U-Pb zircon age for monzosyenite from the Rosen pluton. The mineralogic and compositional features of the Rosen district are comparable to those of well-known IOCG deposits worldwide and geometrically similar to the vertically extensive IOCG veins in the Coastal Cordillera province of northern Chile. The subsidiary granitophile signature that accompanies the characteristic siderophile IOCG suite was also recognized recently at the giant Olympic Dam deposit in South Australia and elsewhere. Although no exposed intrusion is definitively implicated in the genesis of the Rosen veins, coexisting gabbro and syenite fluid sources may be hypothesized at depth in or beneath the coeval ring dike.

Thermal expansion of silicate glass‐forming systems at high temperatures from topological pruning of ring structures

AbstractThe thermal expansion of a silicate glass system containing four types of modifiers at temperatures above the glass transition can be correlated with changes in medium range order (viz., the ring size distribution) without significant modifications in short range order such as Si coordination and Q‐speciation. An empirical linear relation between the network densities of the two groups of silicate glass‐forming systems and their characteristic ring size has been found using the topological pruning picture proposed by Stixrude and Bukowinski (Am Mineral, 1990, 75:1159‐69). Although variation in thermal expansion among different samples exists, for individual composition of the glass‐forming liquids, a strong linear correlation exists between the ring size distribution and the thermal expansion contributed by both configurational change and thermal vibration. The ring evolution of the glass‐forming liquid driven by temperature has been modeled by assuming an Arrhenius‐like activation picture for small member rings and treated as constant numbers for large rings. The compositional dependence of the ring structure can be reflected in the mixed‐alkali or alkaline‐earth effect on the small ring activation energy.

Size and shape of cycloamylose estimated using column chromatography coupled with small-angle X-ray scattering

We built a measurement system combining column chromatography and small angle X-ray scattering (SAXS) to efficiently investigate the dilute solution properties of a series of different molecules, and applied it to cycloamylose (CA), a large ring cyclodextrin. Two different column separation modes were used, size exclusion chromatography (SEC) and reverse phase chromatography with an octadecylsilane bonded silica (ODS) column. Both SEC- and ODS-SAXS worked well and the resulting data agreed with data obtained by batch SAXS experiments. Dilute solution properties of CA were studied for molecular weights ranging from 1621 (degree of polymerization DP = 10) to 9000 (DP > 55) using this flow cell-based SAXS system, and the radius of gyration increased monotonically with increasing DP. This means that individual CA molecules in water are flexible enough and do not adopt any characteristic folding structure at specific DPs, which is what the simulation literature suggested, which will be the basis of physicochemical properties of food polysaccharides as food modifiers.

Co-gasification of digestate and lignite in a downdraft fixed bed gasifier: Effect of temperature

To improve energy efficiency and biomass utilization in the process of anaerobic digestion, co-gasification is considered as an effective method to post-treat anaerobic digestion residues. In this work, the effect of temperature (650 °C, 750 °C, 850 °C and 950 °C) on the co-gasification of digestate and lignite was thoroughly investigated in a downdraft fixed bed gasifier. The results showed that the increase of gasification temperature increased the gas yield and the lower heating value (LHV) of product gas. Physicochemical properties of biochar were characterized by physical adsorption analyzer, Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy and thermogravimetric analyzer (TG). It was shown that the average pore diameter increased in the range of 650 °C to 950 °C, while specific surface area and pore volume first increased from 650 °C to 850 °C and then decreased at 950 °C. The Raman analysis of biochar indicated that small aromatic rings condensed to large aromatic ring and increased the content of Caromatic-Calkyl and the crosslinking density at higher temperature. The variation of biochar properties at the higher temperature caused a decrease in the gasification reactivity. With the increase of temperature, the content of carbolic oil in the tar increased, but the contents of light oil, naphthalene oil and washing oil decreased. This study comprehensively analyzed the products properties and demonstrated the feasibility of co-gasification of digestate and lignite.

Integrating hands‐on model building with graded online discussions to learn DNA structure‐function relationships in an upper level General Biochemistry course for majors

An active‐learning DNA structure/function exercise was undertaken in a 4000‐level majors biochemistry course. During the fourth in‐person class period of the spring 2020 semester majors enrolled in a three‐credit General Biochemistry course were asked to build a physical model of DNA consisting of one turn of the helix including 10 base‐pairs. Students were told to self‐associate into groups of six and each group was then instructed to build a specific base‐pair: 5 groups were assigned GC, 5 were assigned AT. Students were further instructed to divide the labor by partnerships, one to build a purine base, another to build the complementary pyrimidine, and the third to build the sugar‐phosphate. The class was provided with large bundles of six different brightly colored pipe‐cleaners, a bamboo skewer to use as an in‐plane scaffold for the base‐pairs, a large ring stand, and 10 perpendicular rod clamps. They were then given 10 minutes to build their respective base‐pairs then the last five minutes to work together as a class to assemble a single model. The instructor and many students photographed the model and uploaded image files to the online learning platform accompanied by the following prompt.“How much information can we obtain from the admittedly incomplete model we built in class today? Examine the photograph and see if you can decipher the sequence on the two strands. We know adenine is yellow, thymine is purple, guanine is orange, and cytosine is blue. If this sequence were part of a gene which amino acids might they encode? What information would help us answer these questions more precisely? Feel free to share any photos you took during class in replies to this post. You may opt‐out of any one of the next three weekly graded discussions by building your own improved, more beautiful model using the same starting materials for equal credit.”This exercise incorporates multiple active‐learning techniques simultaneously including elements of “think‐pair‐share” during the initial partnership phase, small group work during the assembly of the mononucleotides, and large group cooperation during final assembly of the model. The online follow‐up discussion and optional model‐refinement assignment allow individualized student‐driven engagement with the structure of DNA and how it works to store genetic information.Support or Funding InformationDepartment of Biochemistry College of Agriculture and Life Sciences at Virginia Polytechnic and State University (Virginia Tech)A single turn of the DNA double‐helix: a physical model cooperatively created by students in a 4000 level General Biochemistry course as part of an active‐learning exercise. Model built with large ring stand, 10 perpendicular rod clamps, brighlty‐colored pipe‐cleaners, bamboo skewers, and small plastic beads.Figure 1

Nonstationary coherence-incoherence patterns in nonlocally coupled heterogeneous phase oscillators.

We consider a large ring of nonlocally coupled phase oscillators and show that apart from stationary chimera states, this system also supports nonstationary coherence-incoherence patterns (CIPs). For identical oscillators, these CIPs behave as breathing chimera states and are found in a relatively small parameter region only. It turns out that the stability region of these states enlarges dramatically if a certain amount of spatially uniform heterogeneity (e.g., Lorentzian distribution of natural frequencies) is introduced in the system. In this case, nonstationary CIPs can be studied as stable quasiperiodic solutions of a corresponding mean-field equation, formally describing the infinite system limit. Carrying out direct numerical simulations of the mean-field equation, we find different types of nonstationary CIPs with pulsing and/or alternating chimera-like behavior. Moreover, we reveal a complex bifurcation scenario underlying the transformation of these CIPs into each other. These theoretical predictions are confirmed by numerical simulations of the original coupled oscillator system.

Second phase particles and mechanical properties of 2219 aluminum alloys processed by an improved ring manufacturing process

2219 Al alloy has been used to manufacture the launch vehicle storage tank transition ring, but the large ring obtained in conventional manufacturing processes still suffers from severely agglomerated coarse second phase particles and poor mechanical properties. An improved process (forging at 510 °C with 20% deformation and at 240 °C with 50% deformation, then rolling at 240 °C with 30% deformation, followed by solid solution at 538 °C for 4 h and T8 treatment) for 2219 Al alloy large ring manufacturing was proposed, and the corresponding simulation tests were carried out. The evolution of Al2Cu second phase particles and the mechanical properties of the produced workpieces were investigated. The results showed that the degree of crushing, dissolution, and precipitation of Al2Cu particles were significantly improved in the improved process, and the area fractions of Al2Cu coarse second phase particles after saddle forging and rolling were significantly reduced, leading to 2.4 times increase in area fraction of the θ′ phase after T8 treatment. More homogeneous slip occurred during the tensile testing process and intergranular fracture was the main fracture mechanism. The tensile strength σb, yield strength σs, and elongation δ in the radial direction of the 2219 workpieces were increased to 491 MPa, 388 MPa, and 13.1%, where were increases of 11%, 14%, and 68%, respectively. The uniformity in σb, σs, and δ of the 2219 workpieces increased by 57%, 38%, and 64%, respectively.

Selective Ag+ Adsorption of Ureido Polymer Prepared by Cyclopolymerization Giving Large Ring Repeating Units

We report the synthesis of an ureido polymer containing 19-membered rings, prepared by the cyclopolymerization of a bifunctional monomer trans-1,2-bis(acryloyloxyethylureido)cyclohexane (TBAUCH) an...

What Is Special about Aromatic-Aromatic Interactions? Significant Attraction at Large Horizontal Displacement.

High-level ab initio calculations show that the most stable stacking for benzene–cyclohexane is 17% stronger than that for benzene–benzene. However, as these systems are displaced horizontally the benzene–benzene attraction retains its strength. At a displacement of 5.0 Å, the benzene–benzene attraction is still ∼70% of its maximum strength, while benzene–cyclohexane attraction has fallen to ∼40% of its maximum strength. Alternatively, the radius of attraction (>2.0 kcal/mol) for benzene–benzene is 250% larger than that for benzene–cyclohexane. Thus, at relatively large distances aromatic rings can recognize each other, a phenomenon that helps explain their importance in protein folding and supramolecular structures.

Performance test and application of the large diameter multi-point ring initiator for a shaped charge

A series of experiments were conducted to investigate the synchronicity of the large diameter multi-point ring initiator applied to a shape charge(SC). With the multi-point ring initiator applied to SC, the penetration capability of the SC to penetrate in the reinforced concrete targets were studied. The output Synchronicity of all points of the multi-point ring initiator with diameter of 366mm was measured by the DL-32.II time interval tester. It shows that the output synchronicity of all points is good and the maximum time difference is less than 105ns. The SCs with two different initiation diameters were initiated to penetrate into the reinforced concrete targets. Experimental results show that the dimension of crater and inlet increase with initiation diameter of SCs.

Next generation control rods for fast neutron nuclear reactors

Boron carbide with different boron-10 isotope content is used in the control rods of liquid sodium-cooled fast neutron nuclear reactors as absorbing material. “Trap” type control rods with heterogeneous placement of absorbing (B4C or EU2O3) and moderating (ZrH2) materials were developed. These products did not become widely used due to the high activity of europium radioisotopes and the high damageability of boron carbide. This article examines the design of next-generation control rods with boron carbide in the form of large diameter rings, hafnium hydride (HfHx, where x = 1.0-1.5) and made from a mixture of europium oxide and cobalt (Eu2O3 + Co) for fast neutron reactors . The use of a closed cycle using boron-10 isotopes, as well as spent absorbing kernels from Eu2O3+Co as gamma-ray sources is examined. It also deals with the prospects for the use of control rods with dysprosium hafnate (nDy2O3mHfO2) for lead-cooled fast reactors type BREST-OD-300.

The Effect of the Ring on the Buckling of Stiffened Cylindrical Shells

An analysis on the stringer-stiffened cylindrical shell with a large interval ring is described. The buckling of the shell under axial compression is forecasted by the method of the Ultimate Load Method, to simplify the interconnection on steadiness between shell and stringers. Although the shell between stringers is semi-empirical modeled, the buckling of the stringers which are bolstered with the other stiffened component ring is analytically solved. It is show that support effect of the ring on the stiffened cylindrical shell is quantized by a ring coefficient. The buckling load of the stringer-stiffened cylindrical shell is calculated on the different length. Finally, the ring coefficient is used to explants the so-called shielding panel effect ring. The present results could be an important reference for the design of stiffened shell under axial compression.

Differentiation between Clinically Noninflammatory Granulomatous Lobular Mastitis and Noncalcified Ductal Carcinoma in situ Using Dynamic Contrast-Enhanced Magnetic Resonance Imaging

Introduction: Challenges in differentiation between clinically noninflammatory granulomatous lobular mastitis (GLM) and noncalcified ductal carcinoma in situ (DCIS) remain. Objective: To identify the dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) characteristics contributing to their differential diagnosis. Methods: A total of 33 clinically noninflammatory GLM and 36 noncalcified DCIS were retrospectively analyzed in the study. Internal enhancement of a nonmass enhancement (NME) lesion was divided into clustered enhanced ring (absence/presence), and clustered enhanced ring (presence) was further classified as small and large ring based on the optimal cutoff value. The 5th Breast Imaging and Data System MRI descriptors were used for assessing the other DCE-MRI characteristics. Multivariate analysis including variables with significant differences in univariate analyses was conducted to identify the independent predictors. The discriminative abilities of different predictors and their combination were compared by area under the receiver-operating characteristic curves (AUCs). Results: An NME lesion was seen more commonly in clinically noninflammatory GLM than in noncalcified DCIS (p = 0.003). DCE-MRI characteristics with significant differences in univariate analyses included NME size, clustered enhanced ring (absence/presence), ring size, initial increase and kinetic characteristics for the differentiation between these two entities presenting as NME lesion. Clustered enhanced ring (presence) was further classified as small (≤7 mm) or large ring (>7 mm). Multivariate analysis revealed that internal enhancement and initial increase were identified as significant independent predictors, and the AUC of their combination achieved the highest value of 0.867 (95% CI, 0.748–0.943). Conclusions: An NME lesion with a large ring is more highly suggestive of clinically noninflammatory GLM.

Plasmonic Manipulation of DNA using a Combination of Optical and Thermophoretic Forces: Separation of Different-Sized DNA from Mixture Solution

We demonstrate the size-dependent separation and permanent immobilization of DNA on plasmonic substrates by means of plasmonic optical tweezers. We found that a gold nanopyramidal dimer array enhanced the optical force exerted on the DNA, leading to permanent immobilization of the DNA on the plasmonic substrate. The immobilization was realized by a combination of the plasmon-enhanced optical force and the thermophoretic force induced by a photothermal effect of the plasmons. In this study, we applied this phenomenon to the separation and fixation of size-different DNA. During plasmon excitation, DNA strands of different sizes became permanently immobilized on the plasmonic substrate forming micro-rings of DNA. The diameter of the ring was larger for longer DNA (in base pairs). When we used plasmonic optical tweezers to trap DNA of two different lengths dissolved in solution (φx DNA (5.4 kbp) and λ-DNA (48.5 kbp), or φx DNA and T4 DNA (166 kbp)), the DNA were immobilized, creating a double micro-ring pattern. The DNA were optically separated and immobilized in the double ring, with the shorter sized DNA and the larger one forming the smaller and larger rings, respectively. This phenomenon can be quantitatively explained as being due to a combination of the plasmon-enhanced optical force and the thermophoretic force. Our plasmonic optical tweezers open up a new avenue for the separation and immobilization of DNA, foreshadowing the emergence of optical separation and fixation of biomolecules such as proteins and other ncuelic acids.

Length measurement and stabilization of the diagonals of a square area laser gyroscope

Large frame ring laser gyroscopes are top sensitivity inertial sensors able to measure absolute angular rotation rate below prad s−1 in few seconds. The GINGER project is aiming at directly measuring the Lense–Thirring effect with an 1% precision on an Earth based experiment. GINGER is based on an array of large frame ring laser gyroscopes. The mechanical design of this apparatus requires a micrometric precision in the construction and the geometry must be stabilized in order to keep constant the scale factor of the instrument. The proposed control is based on square cavities, and relies on the length stabilization of the two diagonals, which must be equal at micrometric level. GP2 is the prototype devoted to the scale factor control test. As a first step, the lengths of the diagonals of the ring cavity have been measured through an interferometric technique with a statistical accuracy of some tens of nanometers, and they have been locked to the wavelength of a reference optical standard. Continuous operation has been obtained over more than 12 h, without loss of sensitivity. GP2 is located in a laboratory with standard temperature stabilization, with residual fluctuations of the order of 1 °C. Besides the demonstration of the control effectiveness, the analysis of the Sagnac frequency demonstrates that relative small and low-cost ring lasers (around one meter of side) can also achieve a sensitivity of the order of nrad s−1 in the range 0.01–10 Hz in a standard environment, which is the target sensitivity in many different applications, such as rotational seismology and next generation gravitational waves detectors.

Biocatalytic synthesis of planar chiral macrocycles.

Macrocycles can restrict the rotation of substituents through steric repulsions, locking in conformations that provide or enhance the activities of pharmaceuticals, agrochemicals, aroma chemicals, and materials. In many cases, the arrangement of substituents in the macrocycle imparts an element of planar chirality. The difficulty in predicting when planar chirality will arise, as well as the limited number of synthetic methods to impart selectivity, have led to planar chirality being regarded as an irritant. We report a strategy for enantio- and atroposelective biocatalytic synthesis of planar chiral macrocycles. The macrocycles can be formed with high enantioselectivity from simple building blocks and are decorated with functionality that allows one to further modify the macrocycles with diverse structural features.

Primary Anion–π Catalysis of Epoxide‐Opening Ether Cyclization into Rings of Different Sizes: Access to New Reactivity

The concept of anion-π catalysis focuses on the stabilization of anionic transition states on aromatic π surfaces. Recently, we demonstrated the occurrence of epoxide-opening ether cyclizations on aromatic π surfaces. Although the reaction proceeded through unconventional mechanisms, the obtained products are the same as those from conventional Brønsted acid catalysis, and in agreement with the Baldwin selectivity rules. Different mechanisms, however, should ultimately lead to new products, a promise anion-π catalysis has been reluctant to live up to. Herein, we report non-trivial reactions that work with anion-π catalysis, but not with Brønsted acids, under comparable conditions. Namely, we show that the anion-π templated autocatalysis and epoxide opening with alcoholate-π interactions can provide access to unconventional ring chemistry. For smaller rings, anion-π catalysis affords anti-Baldwin oxolanes, 2-oxabicyclo[3.3.0]octanes, and the expansion of Baldwin oxetanes by methyl migration. For larger rings, anion-π templated autocatalysis is thought to alleviate the entropic penalty of folding to enable disfavored anti-Baldwin cyclizations into oxepanes and oxocanes.

Enzymes lock in planar chirality

Biocatalysis Molecules with very large rings—macrocycles—are often conformationally constrained, and some exhibit planar chirality when substituents of the ring cannot rotate freely. Restricted rotation is generally valued in macrocycles because it can hold the molecule in functional conformations. Using a well-established lipase enzyme, Gagnon et al. developed a synthesis of planar chiral macrocycles with handles that can be easily functionalized. Computational docking suggests how using an enzyme as the catalyst for sequential acylation reactions can impart the observed stereochemistry. Science , this issue p. [917][1] [1]: /lookup/doi/10.1126/science.aaz7381

Closing rings with porous templates

Organic Synthesis The closure of large rings from linear substrates (macrocyclization) must avoid the competing coupling between molecules and the entropic penalty for folding long chains. Hydrophobic nanoscale cavities can assist in both folding of chains and avoiding intermolecular reactions. Liu et al. used a self-assembling molecule bearing bent chains of aromatic groups to create two-dimensional sheets with ∼2-nanometer pores. A palladium(0) catalyst performed Suzuki couplings on linear substrates bound in the pores to create >30-mer macrocycles. On formation, the macrocycles released spontaneously to enable subsequent rounds of reaction. J. Am. Chem. Soc. 142 , 1904 (2020).

Sagnac gyroscopes, GINGERINO, and GINGER

GINGER (Gyroscopes IN GEneral Relativity), based on an array of large dimension ring laser gyroscopes, is aiming at testing on Earth General Relativity effects, like the gravito-electric and gravito-magnetic effects (also known as De Sitter and Lense-Thirring effects) and the Lorentz violation. The sensitivity is a function of the size and of the losses of the ring laser optical cavity. In this kind of measurement long term stability is matter of concern, and underground location is desirable for its natural thermal stability and for being isolated from atmospheric disturbances. Considering the present sensitivity of the RLG prototype GINGERINO, and assuming total losses of 6 ppm, a 40 m perimeter and 1 day of integration time, a sensitivity of the order of frad/s could be achieved. The construction of GINGER is at present under discussion.