Positive variation of the MRI signal via intramolecular inclusion complexation of a C-2 functionalized β-cyclodextrin

The synthesis of a contrast agent based on a β-cyclodextrin is reported. An enhancement of relaxivity in the presence of an intramolecular inclusion complex is observed.

Improved dispersion of transition metals in mesoporous materials through a polymer-assisted melt infiltration method

Dispersed metal particles smaller than 2 nm, thermally stable and exhibiting improved catalytic performances are produced by melt infiltration into mesoporous supports.

Role of Excited States In High-order Harmonic Generation

We investigate the role of excited states in high-order harmonic generation by studying the spectral, spatial, and temporal characteristics of the radiation produced near the ionization threshold of argon by few-cycle laser pulses. We show that the population of excited states can lead either to direct extreme ultraviolet emission through free induction decay or to the generation of high-order harmonics through ionization from these states and recombination to the ground state. By using the attosecond lighthouse technique, we demonstrate that the high-harmonic emission from excited states is temporally delayed by a few femtoseconds compared to the usual harmonics, leading to a strong nonadiabatic spectral redshift.

A single enhanced phase is sufficient for the initial computed tomography evaluation of retroperitoneal tumors in children

PURPOSE

The goal of this study was to evaluate the incremental value of unenhanced phase in the initial evaluation of retroperitoneal tumors in children by comparison with an enhanced phase alone using computed tomography (CT).

MATERIALS AND METHODS

A total of 53 patients (26 girls, 27 boys) with a total of 53 tumors who had CT examination of the abdomen and pelvis for the initial assessment of retroperitoneal tumor were retrospectively included. All CT examinations were obtained with an unenhanced set of CT images and a set of CT images obtained after intravenous administration of iodinated contrast material. One junior and one senior radiologist independently evaluated the two sets in two separate reading sessions. CT images were analyzed for tumor calcifications, tumor location, vascular encasement, local invasion and tumor content.

RESULTS

Calcifications were present in 24/53 tumors (45%). On the enhanced set, the senior radiologist was able to detect calcifications in 22/24 tumors (92%) and the junior radiologist in 20/24 tumors (83%), yielding sensitivities of 92% and 83%, and specificities of 96.5% and 100%, respectively. Inter-observer agreement was excellent (Kappa=0.89). Tumor location was correctly determined by the senior radiologist in 53/53 tumors (100%) and 37/53 tumors (70%) by the junior radiologist. Using the unenhanced set, the senior radiologist was able to assess vascular encasement in 26/53 tumors (49%) against 21/53 (39%) for the junior radiologist. For tumor content, agreement between the enhanced and combined unenhanced and enhanced CT was 77% for both radiologists.

CONCLUSION

Enhanced CT performs as well as unenhanced CT for evidencing calcifications and is therefore sufficient for the initial assessment of retroperitoneal tumor in children.

Effective parameters for film-free femtosecond laser assisted bioprinting

Optimal conditions for femtosecond laser bioprinting setup are reported on in terms of numerical aperture and accuracy of focal spot location for different bioinks to deposit without using a metallic absorbing layer.

Abstract P3-14-06: Evaluation of the therapeutic efficacy of a Rad6 small molecule inhibitor in triple negative breast cancer cells

Triple negative breast cancers (TNBCs) lack estrogen and progesterone receptors and Her2/neu amplification, and are hence not treatable with therapies targeting these molecules. TNBCs have upregulated DNA damage response mechanisms, including the Rad6 postreplication repair (PRR) pathway, that potentially contribute to chemoresistance. Rad6 is a major component of the PRR pathway and its ubiquitin conjugating (UBC) activity is critical for its function. Rad6 expression is low in normal breast cells and tissues but the Rad6 homolog Rad6B is overexpressed in invasive, metastatic and chemoresistant BrCas. Constitutive overexpression of Rad6B in MCF10A cells induces resistance to cisplatin and doxorubicin. TCGA analysis of TNBC patient data showed an association between high Rad6B expression (but not Rad6A) and decreased overall survival. We recently reported the development of a novel Rad6-selective small molecule inhibitor (SMI#9) that inhibits Rad6 UBC activity, migration, and induces apoptosis in TNBC cells but has no effect on MCF10A cells. Since SMI#9 has limited aqueous solubility, in this study we synthesized a modified analog of SMI#9 to enable conjugation via a hydrolyzable ester bond to gold nanoparticle (GNP) and to improve delivery. GNP tethered SMI#9 (SMI#9-GNP) was characterized for purity, ligand conjugation and size by thermogravimetric analysis, atomic force microscopy, transmission electron microscopy, UV-Vis spectroscopy and zeta sizer, and for cellular uptake and drug release by FTIR and mass spectrometry. We compared the activities of SMI#9-GNP and free SMI#9 for cytotoxicity and intracellular localization in mesenchymal (MDA-MB-231 and SUM1315) and basal (MDA-MB-468 and HCC1937) subtypes of TNBC, and in MCF10A cells. Whereas free SMI#9 was cytotoxic to all TNBC cells, SMI#9-GNP demonstrated as good or better cytotoxicity than free SMI#9 only in mesenchymal TNBC cells. MCF10A cells were unaffected by both free and SMI#9-GNP. Consistent with cellular sensitivities, SMI#9-GNP is efficiently endocytosed and processed in lysosomes in mesenchymal TNBC cells, while uptake into basal TNBC cells is compromised by cell microenvironment induced SMI#9-GNP aggregation. SMI#9-GNP treatment induces mitochondrial dysfunction, and stabilization and hyperactivation of PARP-1 that was commensurate with autophagy (indicated by LC3-I to LC3-II conversion). Rad6 loss and PARP-1 hyperactivation are associated with mitochondrial dysfunction, and since inhibition of Rad6 induces both mitochondrial dysfunction and PARP-1 activation this implicates a potential novel role for Rad6 in linking these processes. In summary, our data show that SMI#9-GNP is a suitable delivery vehicle and that the SMI#9 released from GNP conjugate functions similarly as free SMI#9. Our data also illustrate how cell microenvironment induced changes in the physical properties of GNP-drug conjugates can have important implications in the application of nanoparticles in cancer therapy. Supported by NIH R21 CA178117.

Citation Format: Haynes B, Zhang Y, Li J, Petit S, Westwell A, Mao G, Shekhar M. Evaluation of the therapeutic efficacy of a Rad6 small molecule inhibitor in triple negative breast cancer cells. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P3-14-06.

Two-Dimensional Frequency Resolved Optomolecular Gating of High-Order Harmonic Generation

Probing electronic wave functions of polyatomic molecules is one of the major challenges in high-harmonic spectroscopy. The extremely nonlinear nature of the laser-molecule interaction couples the multiple degrees of freedom of the probed system. We combine two-dimensional control of the electron trajectories and vibrational control of the molecules to disentangle the two main steps in high-harmonic generation-ionization and recombination. We introduce a new measurement scheme, frequency-resolved optomolecular gating, which resolves the temporal amplitude and phase of the harmonic emission from excited molecules. Focusing on the study of vibrational motion in N_{2}O_{4}, we show that such advanced schemes provide a unique insight into the structural and dynamical properties of the underlying mechanism.

Fluctuations and All-In-All-Out Ordering in Dipole-Octupole Nd(2)Zr(2)O(7)

By means of neutron scattering and magnetization measurements down to 90 mK, we determine the magnetic ground state of the spin-ice candidate Nd(2)Zr(2)O(7). We show that, despite ferromagnetic interactions, Nd(2)Zr(2)O(7) undergoes a transition around 285 mK towards an all-in-all-out antiferromagnetic state, with a strongly reduced ordered magnetic moment. We establish the (H,T) phase diagram in the three directions of the applied field and reveal a metamagnetic transition around 0.1 T, associated with an unexpected shape of the magnetization curves. We propose that this behavior results from the peculiar nature of the Nd^{3+} doublet, a dipolar-octupolar doublet, different from the standard Kramers doublet studied to date, thus revealing the importance of multipolar correlations in the properties of pyrochlore oxides.

Multi-channel electronic and vibrational dynamics in polyatomic resonant high-order harmonic generation

High-order harmonic generation in polyatomic molecules generally involves multiple channels of ionization. Their relative contribution can be strongly influenced by the presence of resonances, whose assignment remains a major challenge for high-harmonic spectroscopy. Here we present a multi-modal approach for the investigation of unaligned polyatomic molecules, using SF6 as an example. We combine methods from extreme-ultraviolet spectroscopy, above-threshold ionization and attosecond metrology. Fragment-resolved above-threshold ionization measurements reveal that strong-field ionization opens at least three channels. A shape resonance in one of them is found to dominate the signal in the 20-26 eV range. This resonance induces a phase jump in the harmonic emission, a switch in the polarization state and different dynamical responses to molecular vibrations. This study demonstrates a method for extending high-harmonic spectroscopy to polyatomic molecules, where complex attosecond dynamics are expected.

Longitudinal and transverse Zeeman ladders in the Ising-like chain antiferromagnet BaCo(2)V(2)O(8)

We explore the spin dynamics emerging from the Néel phase of the chain compound antiferromagnet BaCo(2)V(2)O(8). Our inelastic neutron scattering study reveals unconventional discrete spin excitations, so-called Zeeman ladders, understood in terms of spinon confinement, due to the interchain attractive linear potential. These excitations consist of two interlaced series of modes, respectively, with transverse and longitudinal polarization. The latter, which correspond to a longitudinal fluctuation of the ordered moment, have no classical counterpart and are related to the zero-point fluctuations that weaken the ordered moment in weakly coupled quantum chains. Our analysis reveals that BaCo(2)V(2)O(8), with moderate Ising anisotropy and sizable interchain interactions, remarkably fulfills the conditions necessary for the observation of discrete long-lived longitudinal excitations.

Temperature-dependent interplay of Dzyaloshinskii-Moriya interaction and single-ion anisotropy in multiferroic BiFeO3

Low-energy magnon excitations in multiferroic BiFeO3 were measured in detail as a function of temperature around several Brillouin zone centers by inelastic neutron scattering experiments on single crystals. Unique features around 1 meV are directly associated with the interplay of the Dzyaloshinskii-Moriya interaction and a small single-ion anisotropy. The temperature dependence of these and the exchange interactions were determined by fitting the measured magnon dispersion with spin-wave calculations. The spectra best fit an easy-axis type magnetic anisotropy and the deduced exchange and anisotropy parameters enable us to determine the anharmonicity of the magnetic cycloid. We then draw a direct connection between the changes in the parameters of spin Hamiltonian with temperature and the physical properties and structural deformations of BiFeO3.

Asymptomatic pelvic metastasis from thymic carcinoma: a case report

Thymic epithelial tumors are rare and often occur somewhere local. Metastatic sites of thymic carcinomas (Masaoka-Koga stage IVb) are mostly seen in the lung, liver and brain. We report a 64-year-old female with an initial diagnosis of thymoma B3 who first showed thoracic recurrences and then an asymptomatic isolated pelvic metastasis from her thymic carcinoma.

Magneto- to electroactive transmutation of spin waves in ErMnO3

The low-energy dynamical properties of the multiferroic hexagonal perovskite ErMnO3 have been studied by inelastic neutron scattering as well as terahertz and far infrared spectroscopies on a synchrotron source. From these complementary techniques, we have determined the magnon and crystal field spectra and identified a zone center magnon excitable only by the electric field of an electromagnetic wave. Using a comparison with the isostructural YMnO3 compound and crystal field calculations, we propose that this dynamical magnetoelectric process is due to the hybridization of a magnon with an electroactive crystal field transition.

Control of ferroelectricity and magnetism in multi-ferroic BiFeO3 by epitaxial strain

Recently, strain engineering has been shown to be a powerful and flexible means of tailoring the properties of ABO3 perovskite thin films. The effect of epitaxial strain on the structure of the perovskite unit cell can induce a host of interesting effects, these arising from either polar cation shifts or rotation of the oxygen octahedra, or both. In the multi-ferroic perovskite bismuth ferrite (BiFeO3-BFO), both degrees of freedom exist, and thus a complex behaviour may be expected as one plays with epitaxial strain. In this paper, we review our results on the role of strain on the ferroic transition temperatures and ferroic order parameters. We find that, while the Néel temperature is almost unchanged by strain, the ferroelectric Curie temperature strongly decreases as strain increases in both the tensile and compressive ranges. Also unexpected is the very weak influence of strain on the ferroelectric polarization value. Using effective Hamiltonian calculations, we show that these peculiar behaviours arise from the competition between antiferrodistortive and polar instabilities. Finally, we present results on the magnetic order: while the cycloidal spin modulation present in the bulk survives in weakly strained films, it is destroyed at large strain and replaced by pseudo-collinear antiferromagnetic ordering. We discuss the origin of this effect and give perspectives for devices based on strain-engineered BiFeO3.

Ultrafast short-range disordering of femtosecond-laser-heated warm dense aluminum

We have probed, with time-resolved x-ray absorption near-edge spectroscopy (XANES), a femtosecond-laser-heated aluminum foil with fluences up to 1  J/cm2. The spectra reveal a loss of the short-range order in a few picoseconds. This time scale is compared with the electron-ion equilibration time, calculated with a two-temperature model. Hydrodynamic simulations shed light on complex features that affect the foil dynamics, including progressive density change from solid to liquid (∼10  ps). In this density range, quantum molecular dynamics simulations indicate that XANES is a relevant probe of the ionic temperature.

An ab initio study of magneto-electric coupling of YMnO3

This paper proposes the direct calculation of the microscopic contributions to the magneto-electric coupling, using ab initio methods. The electrostrictive and the Dzyaloshinskii-Moriya contributions were evaluated individually. For this purpose a specific method was designed, combining density functional theory calculations and embedded fragment, explicitly correlated, quantum chemical calculations. This method allowed us to calculate the evolution of the magnetic couplings as a function of an applied electric field. We found that in YMnO3 the Dzyaloshinskii-Moriya contribution to the magneto-electric effect is three orders of magnitude weaker than the electrostrictive contribution. Strictive effects are thus dominant in the magnetic exchange evolution under an applied electric field, and by extension in the magneto-electric effect. These effects however, remain quite small, and the modifications of the magnetic excitations under an applied electric field will be difficult to observe experimentally. Another important conclusion is that it can be shown that the linear magneto-electric tensor is null due to the inter-layer symmetry operations.

Magnetization process in Er2Ti2O7 at very low temperature

We present a model which accounts for the high-field magnetization at very low temperature in the frustrated pyrochlore compound Er2Ti2O7. In Er2Ti2O7, the Er(3+) ion has a planar crystal field anisotropy and the material undergoes a transition to antiferromagnetism at TN = 1.2 K. Our model is a mean-field self-consistent calculation involving the four rare earth sites of a tetrahedron, the building unit of the pyrochlore lattice. It includes the full crystal field Hamiltonian, the infinite range dipolar interaction and anisotropic nearest neighbour exchange described by a 4-component tensor. We discuss the equivalence of our treatment of the exchange tensor, taken to be diagonal in a frame linked to a rare earth-rare earth bond, with the pseudo-spin Hamiltonian recently developed for Kramers doublets in a pyrochlore lattice.