Coordination Shifts Research Articles

Origin of the c-axis ultraincompressibility of Mo2GaC above about 15 GPa from first principles

The mechanical properties and structural evolution of Mo2GaC are calculated by first-principles under pressure. Our results unexpectedly found that the c axis is always stiffer than a axis within 0–100 GPa. An ultraincompressibility of c axis within 15–60 GPa is observed, with a contraction of about 0.2 Å, slightly larger than that of a axis (0.14 Å). The abnormal expansion of c axis and the fast decrease in a axis above about 15 GPa and 70 GPa failed to induce the structural instability, whereas such behavior caused the elastic softening in many mechanical quantities. The shrinkage anomaly of c axis is closely reflected by the internal coordinate (u) shift of Mo atom as it shows three different slopes within 0–15 GPa, 20–60 GPa, and 70–100 GPa, respectively. The longest Mo-Mo bond is responsible for the unusual shrinkage of c-axis under pressure as they experience nearly identical pressure dependences, whereas the a axis presents certain response with the variation of C-Mo bond particularly at 70 GPa. The electronic properties are investigated, including the energy band and density of states, and so on. At G point of K-M line, the energy decreases at 10 GPa first and increases at 30 GPa subsequently, the critical point is at about 15 GPa, with respective values of −0.17 of 0 GPa, −0.18 of 10 GPa, −0.16 of 15 GPa, and −0.13 of 30 GPa, respectively. This alternative energy change of G point, which is the symmetry center of the rhombic parallelogram of Ga atoms and the midpoint of the two bonded Mo atoms, convincingly reveal the origin of the anomalous ultraincompressibility of c axis as the Mo-Mo bond length shrinkage has to overcome the increasing energy barrier height. The Mo-Mo bond population and the electronegativity investigations of the Mo atom further reveal the most likely origin of the ultraincompressibility of c axis. This interesting result expects further experimental confirmation as this is the first nanolaminate ceramics compound presenting quite low-pressure axial ultraincompressibility.

Luminescent coordination polymers for the VIS and NIR range constituting LnCl₃ and 1,2-bis(4-pyridyl)ethane.

A series of 14 lanthanide containing coordination polymers LnCl3 with 1,2-bis(4-pyridyl)ethane (bpe) was synthesized from either thiazole or pyridine. Depending on the ligand content, a structural diversity from 3D-frameworks [LnCl3(bpe)2]·thz, Ln = Ce-Lu, to 1D-strands [La2Cl6(bpe)2(thz)6] and [LnCl3(bpe)(py)2]·(bpe/py), Ln = Gd, Er, was obtained and characterized by X-ray single crystal diffraction, powder diffraction, differential thermal analysis and thermogravimetry (DTA/TG), IR-spectroscopy and photoluminescence spectroscopy. The compounds exhibit a variety of luminescence properties and different phenomena. This includes ligand centred fluorescence, metal-centred 5d-4f/4f-4f emission in the visible and the NIR range, antenna effects via Dexter and Förster energy transfer mechanisms, excitation dependent emission with a correlating shift of the chromaticity coordinates and inner filter effects by combined re-absorption/emission.

Riemann curvature of a boosted spacetime geometry

The ultrarelativistic boosting procedure had been applied in the literature to map the metric of Schwarzschild–de Sitter spacetime into a metric describing de Sitter spacetime plus a shock-wave singularity located on a null hypersurface. This paper evaluates the Riemann curvature tensor of the boosted Schwarzschild–de Sitter metric by means of numerical calculations, which make it possible to reach the ultrarelativistic regime gradually by letting the boost velocity approach the speed of light. Thus, for the first time in the literature, the singular limit of curvature, through Dirac’s [Formula: see text] distribution and its derivatives, is numerically evaluated for this class of spacetimes. Moreover, the analysis of the Kretschmann invariant and the geodesic equation shows that the spacetime possesses a “scalar curvature singularity” within a 3-sphere and it is possible to define what we here call “boosted horizon”, a sort of elastic wall where all particles are surprisingly pushed away, as numerical analysis demonstrates. This seems to suggest that such “boosted geometries” are ruled by a sort of “antigravity effect” since all geodesics seem to refuse to enter the “boosted horizon” and are “reflected” by it, even though their initial conditions are aimed at driving the particles toward the “boosted horizon” itself. Eventually, the equivalence with the coordinate shift method is invoked in order to demonstrate that all [Formula: see text] terms appearing in the Riemann curvature tensor give vanishing contribution in distributional sense.

Raman Spectra of Luminescent Graphene Oxide (GO)-Phosphor Hybrid Nanoscrolls.

Graphene oxide (GO)-phosphor hybrid nanoscrolls were synthesized using a simple chemical method. The GO-phosphor ratio was varied to find the optimum ratio for enhanced optical characteristics of the hybrid. A scanning electron microscope analysis revealed that synthesized GO scrolls achieved a length of over 20 μm with interior cavities. The GO-phosphor hybrid is extensively analyzed using Raman spectroscopy, suggesting that various Raman combination modes are activated with the appearance of a low-frequency radial breathing-like mode (RBLM) of the type observed in carbon nanotubes. All of the synthesized GO-phosphor hybrids exhibit an intense luminescent emission around 540 nm along with a broad emission at approximately 400 nm, with the intensity ratio varying with the GO-phosphor ratio. The photoluminescence emissions were gauged using Commission Internationale d'Eclairage (CIE) coordinates and at an optimum ratio. The coordinates shift to the white region of the color spectra. Our study suggests that the GO-phosphor hybrid nanoscrolls are suitable candidates for light-emitting applications.

Daily patient setup error in prostate image guided radiation therapy with fiducial-based kilovoltage onboard imaging and conebeam computed tomography.

This study examined the interfraction setup error in patients undergoing prostate radiotherapy using fiducial markers and on-board imaging. Patients (n=53) were aligned to the treatment isocenter by laser followed by orthogonal kilovoltage (kV) radiographs to visualize bony anatomy and implanted fiducial markers. The magnitude and direction of couch shifts for isocenter correction required was determined by image registration for bony anatomy and fiducial markers. Twice weekly, 25 of the 53 patients also underwent conebeam computed tomography (CBCT) to measure any residual error in patient positioning. Based on individual coordinate shifts from CBCT, a net three-dimensional (3D) residual shift magnitude vector R was calculated. The average couch shifts were 0.26 and 0.40 cm in inferior direction and 0.25 and 0.33 cm in superior direction for alignments made with bony anatomy and fiducial markers, respectively (P<0.0001). There were no significant differences noted in the vertical or lateral planes between the two image registration methods. In subset of 25 patients, no residual shift from fiducial plain film set up was required with CBCT matching in 66.5%, 52.4% and 57.9% of fractions for longitudinal, vertical and lateral planes, respectively, with majority (79%) of patients having a net residual 3D shifts of <0.3 cm. The use of CBCT increased average treatment time by approximately 6 min compared to kV radiographs alone. The residual setup errors following daily kV image guided localization, as determined by CBCT, were small, which demonstrates high accuracy of kV localization when fiducial markers are present.

Structure of binuclear platinum(III) acetamidate complexes in solutions as probed by 195Pt, 13C, and 1H NMR spectroscopy

195Pt, 1H, and 13C NMR spectroscopy was used to study the structure of binuclear platinum(III) acetamidate complexes with 1,10-phenanthroline and 2,2′-bipyridine ligands [Pt2(phen)2(acam)4](NO3)2 (1) and [Pt2(bipy)2(acam)4](NO3)2 (2) in aqueous solutions. The 195Pt NMR spectra of solutions of complexes 1 and 2 in D2O exhibit two signals with satellites due to the 195Pt–195Pt spin-spin coupling (1J(Pt–Pt) ≈ 6345 Hz), whereas their 1H and 13C NMR spectra contain four sets of signals for the protons and the carbon atoms of the heterocyclic and acetamidate ligands. The signals were assigned using the COSY, NOESY, and HSQC/ HMBC experiments and comparing the coordination shifts of the signals for the protons of heterocycles. These data allowed us to draw a conclusion that binuclear complexes 1 and 2 in solution have a head-to-head structure with nonequivalent platinum(III) atoms (coordination cores PtN5 and PtN3O2), the axial-equatorial coordination of the bidentate heterocyclic molecules, and two bridging and two terminal acetamidate ligands.

A solid-state17O NMR study of platinum-carboxylate complexes: carboplatin and oxaliplatin

We report synthesis and solid-state NMR characterization of two17O-labeled platinum anticancer drugs: cis-diammine(1,1-cyclobutane-[17O4]dicarboxylato)platinum(II) (carboplatin) and ([17O4]oxalato)[(1R, 2R)-(−)-1,2-cyclohexanediamine)]platinum(II) (oxaliplatin). Both17O chemical shift (CS) and quadrupolar coupling (QC) tensors were measured for the carboxylate groups in these two compounds. With the aid of plane wave DFT computations, the17O CS and QC tensor orientations were determined in the molecular frame of reference. Significant changes in the17O CS and QC tensors were observed for the carboxylate oxygen atom upon its coordination to Pt(II). In particular, the17O isotropic chemical shifts for the oxygen atoms directly bonded to Pt(II) are found to be smaller (more shielded) by 200 ppm than those for the non-Pt-coordinated oxygen atoms within the same carboxylate group. Examination of the17O CS tensor components reveals that such a large17O coordination shift is primarily due to the shielding increase along the direction that is within the O=C–O–Pt plane and perpendicular to the O–Pt bond. This result is interpreted as due to the σ donation from the oxygen nonbonding orbital (electron lone pair) to the Pt(II) empty dyzorbital, which results in large energy gaps between σ(Pt–O) and unoccupied molecular orbitals, thus reducing the paramagnetic shielding contribution along the direction perpendicular to the O–Pt bond. We found that the17O QC tensor of the carboxylate oxygen is also sensitive to Pt(II) coordination, and that17O CS and QC tensors provide complementary information about the O–Pt bonding.

Use of prism adaptation in children with unilateral brain lesion: Is it feasible?

IntroductionUnilateral visuospatial deficits have been observed in children with brain damage. While the effectiveness of prism adaptation for treating unilateral neglect in adult stroke patients has been demonstrated previously, the usefulness of prism adaptation in a pediatric population is still unknown. The present study aims at evaluating the feasibility of prism adaptation in children with unilateral brain lesion and comparing the validity of a game procedure designed for child-friendly paediatric intervention, with the ecological task used for prism adaptation in adult patients. MethodsTwenty-one children with unilateral brain lesion randomly were assigned to a prism group wearing prismatic glasses, or a control group wearing neutral glasses during a bimanual task intervention. All children performed two different bimanual tasks on randomly assigned consecutive days: ecological tasks or game tasks. The efficacy of prism adaptation was measured by assessing its after-effects with visual open loop pointing (visuoproprioceptive test) and subjective straight-ahead pointing (proprioceptive test). ResultsGame tasks and ecological tasks produced similar after-effects. Prismatic glasses elicited a significant shift of visuospatial coordinates which was not observed in the control group. ConclusionPrism adaptation performed with game tasks seems an effective procedure to obtain after-effects in children with unilateral brain lesion. The usefulness of repetitive prism adaptation sessions as a therapeutic intervention in children with visuospatial deficits and/or neglect, should be investigated in future studies.

Electrical and optical characteristics of phosphorescent organic light-emitting device with thin-codoped layer insertion

In this paper, we demonstrated the changes of electrical and optical characteristics of a phosphorescent organic light-emitting device (OLED) with tris(phenylpyridine)iridium Ir(ppy)3 thin layer (4nm) slightly codoped (1%) inside the emitting layer (EML) close to the cathode side. Such a thin layer helped for electron injection and transport from the electron transporting layer into the EML, which reduced the driving voltage (0.40V at 100mA/cm2). Electroluminescence (EL) spectral shift at different driving voltage was observed in our blue OLED with [(4,6-di-fluoropheny)-pyridinato-N,C2′]picolinate (FIrpic) emitter, which came from the recombination zone shift. With the incorporation of thin-codoped Ir(ppy)3, such EL spectral shift was almost undetectable (color coordinate shift (0.000, 0.001) from 100 to 10,000cd/m2), due to the compensation of Ir(ppy)3 emission at low driving voltage. Such a methodology can be applied to a white OLED which stabilized the EL spectrum and the color coordinates ((0.012, 0.002) from 100 to 10,000cd/m2).

Glucose-Based Regulation of miR-451/AMPK Signaling Depends on the OCT1 Transcription Factor

In aggressive, rapidly growing solid tumors such as glioblastoma multiforme (GBM), cancer cells face frequent dynamic changes in their microenvironment, including the availability of glucose and other nutrients. These challenges require that tumor cells have the ability to adapt in order to survive periods of nutrient/energy starvation. We have identified a reciprocal negative feedback loop mechanism in which the levels of microRNA-451 (miR-451) are negatively regulated through the phosphorylation and inactivation of its direct transcriptional activator OCT1 by 5' AMP-activated protein kinase (AMPK), which is activated by glucose depletion-induced metabolic stress. Conversely, in a glucose-rich environment, unrestrained expression of miR-451 suppresses AMPK pathway activity. These findings uncover miR-451 as a major effector of glucose-regulated AMPK signaling, allowing tumor cell adaptation to variations in nutrient availability in the tumor microenvironment.

Electronic Fine‐Tuning of Oxygen Atom Transfer Reactivity of cis‐Dioxomolybdenum(VI) Complexes with Thiosemicarbazone Ligands

AbstractA series of six cis‐dioxomolybdenum(VI) complexes with thiosemicarbazone ligands was synthesized and characterized. The ligands were obtained by reacting ethyl thiosemicarbazide with salicylaldehydes substituted with a selection of electron‐withdrawing and electron‐donating groups. The crystal structures, IR, NMR spectroscopic data and oxygen atom transfer activities of the complexes revealed that the electronic effects of the substituents located in the para‐position of the phenolate donor are transmitted through to the molybdenum center, as reflected by linear relationships between Hammett constants and key properties of the complexes, including the molybdenum–phenolate bond lengths and the coordination shift of the imine proton resonance. Compared with the unsubstituted catalyst, electron‐withdrawing substituents increase the rate of oxygen atom transfer from dimethyl sulfoxide to triphenylphosphine, whereas electron‐donating groups have the opposite effect. The highest rate enhancement was achieved through the introduction of a strongly electron‐withdrawing NO2 substituent in the p‐position of the phenolate donor.

Structural and 1H, 13C, 15N NMR spectroscopic studies of Pd(II) chloride organometallics with 2-phenylpyridine and ammonia, pyridine or its methyl derivatives

Pd(II) chloride organometallics with 2-phenylpyridine and pyridines of general formula [Pd(2ppy∗)LCl] (2ppy∗=C(2′)-deprotonated form of 2-phenylpyridine (2ppy), acting as N(1),C(2′)-chelating ligand; L=NH3, pyridine, 2-, 3-, 4-methylpyridine, 2,3-, 2,4-, 2,6-, 3,5-dimethylpyridine, 2,4,6-trimethylpyridine) were studied by 1H, 13C and 15N NMR. 1H, 13C and 15N NMR coordination shifts (i.e. differences of chemical shifts for the same atom in the complex and ligand molecules) were discussed in relation to the molecular structures. Single crystal X-ray structure of trans(N,N)-[Pd(2ppy∗)(2,4,6col)Cl] was solved. The analysis of 15N NMR coordination shifts for the whole series of the studied organometallics exhibited that all of them had an analogous trans(N,N) geometry.

Type IIB supergravity solutions with AdS5 from Abelian and non-Abelian T dualities

We present a large class of new backgrounds that are solutions of type IIB supergravity with a warped AdS5 factor, non-trivial axion-dilaton, B-field and three-form Ramond-Ramond flux but yet have no five-form flux. We obtain these solutions and many of their variations by judiciously applying non-Abelian and Abelian T-dualities, as well as coordinate shifts to AdS5 × X 5 IIB supergravity solutions with X 5 = S 5 , T 1,1 , Y p,q . We address a number of issues pertaining to charge quantization in the context of non-Abelian T-duality. We comment on some properties of the expected dual super conformal field theories by studying their CFT central charge holographically. We also use the structure of the supergravity Page charges, central charges and some probe branes to infer aspects of the dual super conformal field theories.

Copy-Rotate-Move Forged Region Detection Using Compensation of Coordinate Shift by Rotation

본 논문에서는 회전에 의한 좌표 이동의 보상을 이용하여 복사-회전-이동 조작된 영상의 영역을 검출하는 방법을 제안하고자 한다. 본 논문의 방법은 아핀 변환을 사용하여 회전에 의해 야기된 좌표 이동값을 분석하고, 이동이 보상된 영상을 구성한다. 구성된 회전 보상 영상에 대하여 양자화를 수행하고, 이에 대한 자카드 유사도를 구하여 조작 영역을 찾기 위한 매칭을 수행한다. 본 논문의 방법은 회전에 의한 좌표 이동을 보상하기 때문에 거의 모든 복사-회전-이동 조작 영역을 검출할 수 있으며, 작은 블록으로 매칭을 수행하여 작은 영역의 검출이 가능한 장점을 가지고 있다. 실험 결과에서 제안 방법은 모든 각도의 복사-회전-이동 조작에서 기존 방법과 비교하여 우수한 검출 결과를 나타낸다.

Assessment of registration accuracy during computer-aided oncologic limb-salvage surgery.

Computer-aided surgery is used in musculoskeletal tumor procedures to improve the surgeon's orientation to local anatomy during tumor resection. For the navigation system to function correctly, preoperative imaging (e.g., CT, MR) must be registered to the patient in the operating room. The goals of this study were (1) to directly quantify registration accuracy in computer-aided tumor surgery and (2) to validate the "system reported error" (SRE) of the navigation system. Registration accuracy was evaluated in eight bone sarcoma cases by determining the location of the anatomical paired-points used for registration following surface matching. Coordinates of specific intraoperative post-registration points were compared with the corresponding coordinates in preoperative CT scans to determine the measurement error (ME). The mean difference between post-registration points and planned registration points was 12.21±6.52 mm significantly higher than the mean SRE (0.68 ± 0.15 mm; p = 0.002; 95 % CI 6.11-16.96 mm). The SRE poorly correlated with the calculated ME (R(2) = 0.040). Anatomical paired-point registration with surface matching results in a substantial shift in the post-registration coordinates of the same paired-points used for registration, and this shift is not represented by the SRE. The SRE of a surgical navigation system was poorly correlated with direct measurements obtained in musculoskeletal tumor surgery. Improvement in registration accuracy is needed to better navigate tumor boundaries and ensure clear margins while maximally preserving the unaffected tissues and reducing operative morbidity.

Using a predictive model of clinician intention to improve continuing health professional education on cancer survivorship.

Cancer survivorship is a chronic disease that places patients in limbo between oncologists and primary care clinicians. Strategies have been proposed to ease the shift in coordination of care, including broad-based educational outreach to primary care providers. Guided by the theory of planned behavior (TPB), predictors of intention to provide survivorship care, including credentials, experience, perception of barriers, and personal survivorship status, were evaluated using logistic regression with a cohort of physicians, nurse practitioners, and registered nurses participating in an unprecedented online continuing medical education/continuing education survivorship care course. Results showed that physicians were significantly less likely to express intent to provide survivorship care (odds ratio [OR] = .237, p = .0001) compared to the other groups. Overall, clinicians with 6-10 years of experience were 3 times more likely to express intent to provide survivorship care (OR = 2.86, p = .045) than those with less or more experience. When clinicians perceived the presence of a barrier, they were nearly twice as likely to have diminished intent (OR = 1.89, p = .035). Most participants (66%; n = 1185) selected two barriers: lack of survivorship care plans and treatment summaries (45.4%; n = 821) and lack of education (20.1%; n = 364). Barriers to the delivery of survivorship care can influence clinicians' intention to provide survivorship care, which varied by years of experience in this study. Interdisciplinary educational strategies featuring midcareer provider champions who have successfully incorporated survivorship care and can offer specific solutions to these barriers are recommended for future interventions.

Asymmetrical Bessel modes of the first and second type and their superpositions

We considered nonparaxial asymmetric Bessel modes of the first and second type, which differ from a conventional symmetric Bessel mode by a real-valued shift along one Cartesian coordinate and imaginary shift along the other (both shifts are equal in modulus). Bessel modes of the first and second type differ only in the shift sign and, therefore, have different orbital angular momentum (OAM) (integer or fractional). Addition and subtraction of two identical asymmetric Bessel modes of the first and second type leads to light beams with the same integer OAM equal to the topological charge of the generating mode, but with different transverse intensity distributions, which depend on the shift magnitude.

Kinematic analysis of stellar radial velocities by the spherical harmonics

A method for a kinematic analysis of stellar radial velocities using spherical harmonics is proposed. This approach does not depend on the specific kinematic model and allows both low-frequency and high-frequency kinematic radial velocity components to be analyzed. The possible systematic variations of distances with coordinates on the celestial sphere that, in turn, are modeled by a linear combination of spherical harmonics are taken into account. Theoretical relations showing how the coefficients of the decomposition of distances affect the coefficients of the decomposition of the radial velocities themselves have been derived. It is shown that the larger the mean distance to the sample of stars being analyzed, the greater the shift in the solar apex coordinates, while the shifts in the Oort parameter A are determined mainly by the ratio of the second zonal harmonic coefficient to the mean distance to the stars, i.e., by the degree of flattening of the spatial distribution of stars toward the Galactic plane. The distances to the stars for which radial velocity estimates are available in the CRVAD-2 catalog have been decomposed into spherical harmonics, and the existing variations of distances with coordinates are shown to exert no noticeable influence on both the solar motion components and the estimates of the Oort parameter A, because the stars from this catalog are comparatively close to the Sun (no farther than 500 pc). In addition, a kinematic component that has no explanation in terms of the three-dimensional Ogorodnikov-Milne model is shown to be detected in the stellar radial velocities, as in the case of stellar proper motions.

Which way is down? Positional distortion in the tilt illusion.

Contextual information can have a huge impact on our sensory experience. The tilt illusion is a classic example of contextual influence exerted by an oriented surround on a target's perceived orientation. Traditionally, the tilt illusion has been described as the outcome of inhibition between cortical neurons with adjacent receptive fields and a similar preference for orientation. An alternative explanation is that tilted contexts could produce a re-calibration of the subjective frame of reference. Although the distinction is subtle, only the latter model makes clear predictions for unoriented stimuli. In the present study, we tested one such prediction by asking four naive subjects to estimate three positions (4, 6, and 8 o'clock) on an imaginary clock face within a tilted surround. To indicate their estimates, they used either an unoriented dot or a line segment, with one endpoint at fixation in the middle of the surround. The surround's tilt was randomly chosen from a set of orientations (±75°, ±65°, ±55°, ±45°, ±35°, ±25°, ±15°, ±5° with respect to vertical) across trials. Our results showed systematic biases consistent with the tilt illusion in both conditions. Biases were largest when observers attempted to estimate the 4 and 8 o'clock positions, but there was no significant difference between data gathered with the dot and data gathered with the line segment. A control experiment confirmed that biases were better accounted for by a local coordinate shift than to torsional eye movements induced by the tilted context. This finding supports the idea that tilted contexts distort perceived positions as well as perceived orientations and cannot be readily explained by lateral interactions between orientation selective cells in V1.

Integrated geometric and thermal error modeling and compensation for vertical machining centers

The accuracy of machine tools is significantly affected by the geometric defect and thermal deformation of the mechanical components. This paper intends to provide a comprehensive compensation method for the integrated geometric and thermal errors of machine tools. Firstly, a synthesized volumetric model is established with homogeneous transformation matrix method, considering both the geometric and thermal effects. Then, in order to improve the modeling accuracy and efficiency of the geometric error components, an automatic modeling algorithm is proposed with the Chebyshev polynomial-based orthogonal least squares regression. Also, to improve the robustness of the thermal error models for the feed axes and the spindle system, the thermal effects caused by external ambient variation and internal heat sources are identified and modeled separately. Finally, an intelligent virtual compensation system is developed for machine tools based on the function of external machine original coordinate shift and fast Ethernet data interaction technique, and compensation tests on a vertical machining center showed that the position accuracy of the machine tool could be significantly improved after compensation.