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Resonant optical excitation of certain molecular vibrations in κ-(BEDT-TTF)_{2}Cu[N(CN)_{2}]Br has been shown to induce transient superconductinglike optical properties at temperatures far above equilibrium T_{c}. Here, we report experiments across the bandwidth-tuned phase diagram of this class of materials, and study the Mott insulator κ-(BEDT-TTF)_{2}Cu[N(CN)_{2}]Cl and the metallic compound κ-(BEDT-TTF)_{2}Cu(NCS)_{2}. We find nonequilibrium photoinduced superconductivity only in κ-(BEDT-TTF)_{2}Cu[N(CN)_{2}]Br, indicating that the proximity to the Mott insulating phase and possibly the presence of preexisting superconducting fluctuations are prerequisites for this effect.
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BACKGROUND: The use of traction during hip arthroscopy is commonly used to provide safe joint access and to improve visualization. However, traction during hip arthroscopy has been associated with complications ranging from transient neuropraxias to devastating soft-tissue necrosis. Trendelenburg positioning may be helpful, but the degree to which this is true is not well understood. QUESTIONS/PURPOSES: To determine whether there would be a reduction in perineal pressure at 5°, 10°, and 15° of Trendelenburg compared with baseline (0° of Trendelenburg) while in the modified supine position during hip arthroscopy. METHODS: A consecutive cohort of 50 patients treated with hip arthroscopy by a single, high-volume orthopaedic surgeon was analyzed. There were 30 females and 20 males in this study, with a mean age of 36 ± 16 years (range, 14 to 66 years); mean BMI was 26 kg/m. In the operating room, patients were placed in the modified supine position on a traction extension table with a well-padded perineal post. A standard blood pressure cuff was secured to the post to measure pressure exerted on the perineum as traction was applied to distract the hip. For each patient, pressure against the perineum was measured at four different positions using a digital level: 0°, 5°, 10°, and 15° of Trendelenburg. These positions were tested in a random order for each patient. Mean pressure was compared within patients under the four-period crossover design using a repeated-measure (mixed) ANOVA model. Examination of the residual error quantile plot showed that the pressure data followed a normal distribution, making the use of a parametric model appropriate. Tests were made for period and order effects. RESULTS: Compared with baseline (0° or no Trendelenburg) there was a reduction in pressure of 4.4 (15.5%) at 5° of Trendelenburg (p = 0.203), 8 (28%) at 10° of Trendelenburg (p = 0.022) and 13.1 (46%) at 15° (p = 0.006). These results were maintained regardless of the sequence of positions used in each patient (0°, 5°, 10°, 15°). CONCLUSIONS: Trendelenburg positioning of 10° and 15° during hip arthroscopy resulted in decreased perineal pressure compared with the neutral (0°) position. This technique is intended to harness gravity to exert the majority of countertraction while retaining the perineal post as a backup patient stabilizer. Routine introduction of Trendelenburg during hip arthroscopy reduces perineal pressure against the post, which may decrease complications related to traction and perineal pressure. Future studies should assess whether the observed differences in perineal pressure will reduce the frequency of post-related complications after hip arthroscopy. LEVEL OF EVIDENCE: Level II, therapeutic study.
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Artroplastia de Reemplazo de Cadera , Inclinación de Cabeza , Articulación de la Cadera/cirugía , Posicionamiento del Paciente , Posición Supina , Tracción , Adolescente , Adulto , Anciano , Artroplastia de Reemplazo de Cadera/efectos adversos , Fenómenos Biomecánicos , Estudios Cruzados , Femenino , Inclinación de Cabeza/efectos adversos , Articulación de la Cadera/diagnóstico por imagen , Articulación de la Cadera/fisiopatología , Humanos , Illinois , Masculino , Persona de Mediana Edad , Posicionamiento del Paciente/efectos adversos , Traumatismos de los Nervios Periféricos/etiología , Traumatismos de los Nervios Periféricos/prevención & control , Presión , Estudios Prospectivos , Nervio Pudendo/lesiones , Tracción/efectos adversos , Resultado del Tratamiento , Adulto JovenRESUMEN
We investigate the low-temperature magnetic properties of the molecule-based chiral spin chain [Cu(pym)(H_{2}O)_{4}]SiF_{6}·H_{2}O (pym=pyrimidine). Electron-spin resonance, magnetometry and heat capacity measurements reveal the presence of staggered g tensors, a rich low-temperature excitation spectrum, a staggered susceptibility, and a spin gap that opens on the application of a magnetic field. These phenomena are reminiscent of those previously observed in nonchiral staggered chains, which are explicable within the sine-Gordon quantum-field theory. In the present case, however, although the sine-Gordon model accounts well for the form of the temperature dependence of the heat capacity, the size of the gap and its measured linear field dependence do not fit with the sine-Gordon theory as it stands. We propose that the differences arise due to additional terms in the Hamiltonian resulting from the chiral structure of [Cu(pym)(H_{2}O)_{4}]SiF_{6}·H_{2}O, particularly a uniform Dzyaloshinskii-Moriya coupling and a fourfold periodic staggered field.
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BACKGROUND: Recent studies identified microinstability in the hip as a pathoetiology of painful hip conditions, and it was proposed that generalized ligamentous laxity conditions may predispose patients to such microinstability. PURPOSE: To study the relationship of generalized ligamentous laxity with patient characteristics, clinical presentation, intraoperative findings, and surgical treatments in a cohort of patients undergoing hip arthroscopy. STUDY DESIGN: Cross-sectional study; Level of evidence, 3. METHODS: Registry data were prospectively collected and retrospectively reviewed between February 2014 and November 2017 for patients who underwent primary hip arthroscopy and had a documented Beighton score to assess generalized ligamentous laxity. Patients with a history of an ipsilateral hip condition or ipsilateral hip surgery, those with Tönnis grade >1, and those who had simultaneous arthroscopic and open procedures were excluded from the study. Two comparisons were made between patients with low and high Beighton scores: Beighton 0 vs ≥1 (B 0 vs B ≥1) and Beighton 0-3 vs ≥4 (B 0-3 vs B ≥4). Patient demographics, symptomatology, physical examination, and intraoperative findings were compared between these low and high Beighton groups. RESULTS: A total of 1381 patients met our inclusion and exclusion criteria. Within this patient population, there were 882 with B 0, 499 with B ≥1, 1120 with B 0-3, and 261 with B ≥4. B 0 was 54.1% female, compared with 84.2% of B ≥1. Similarly, B 0-3 was 58.5% female, while B ≥4 was 92.7% female. The difference in sex makeup was significant between both sets of groups ( P < .0001). The relative risk of having B ≥1 for women versus men was 2.869, and the relative risk of having B ≥4 for women versus men was 6.873. The patients with higher Beighton scores in B ≥1 and B ≥4 had a younger mean age at onset of symptoms ( P < .0001) and lower mean body mass index ( P < .0001) than those in B 0 and B 0-3, respectively. The B ≥1 group had higher preoperative range of motion with internal rotation ( P = .05), external rotation ( P = .017), and flexion ( P < .0001) than B 0 patients, as well as a lower frequency of Trendelenburg gait pattern ( P = .0268). Similarly, the B ≥4 group had higher range of motion than the B 0-3 group with internal rotation ( P = .030), external rotation ( P = .003), flexion ( P < .0001), and abduction ( P = .002). As compared with the lower-score groups, the higher-score groups also had smaller labral size and tear dimension ( P < .0001), and a higher proportion of these patients underwent labral repair, capsular repair, and iliopsoas fractional lengthening. CONCLUSION: Patients undergoing hip arthroscopy who have generalized ligamentous laxity are overall younger, have a lower body mass index, and are more often female, as compared with patients who have lesser laxity. Patients with higher preoperative Beighton scores had greater hip range of motion and smaller intraoperative labral size and tear dimensions. Additionally, these patients were more likely to undergo labral repair, capsular plication, and iliopsoas fractional lengthening.
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Artroscopía , Articulación de la Cadera/fisiopatología , Articulación de la Cadera/cirugía , Inestabilidad de la Articulación/epidemiología , Ligamentos Articulares/fisiopatología , Complicaciones Posoperatorias/epidemiología , Adulto , Artroscopía/efectos adversos , Estudios Transversales , Femenino , Humanos , Masculino , Persona de Mediana Edad , Examen Físico , Prevalencia , Rango del Movimiento Articular , Estudios Retrospectivos , Rotación , Adulto JovenRESUMEN
The endohedral fullerene ^{15}N@C_{60} has narrow electron paramagnetic resonance lines which have been proposed as the basis for a condensed-matter portable atomic clock. We measure the low-frequency spectrum of this molecule, identifying and characterizing a clock transition at which the frequency becomes insensitive to magnetic field. We infer a linewidth at the clock field of 100 kHz. Using experimental data, we are able to place a bound on the clock's projected frequency stability. We discuss ways to improve the frequency stability to be competitive with existing miniature clocks.
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We show that the electron spin phase memory time, the most important property of a molecular nanomagnet from the perspective of quantum information processing, can be improved dramatically by chemically engineering the molecular structure to optimize the environment of the spin. We vary systematically each structural component of the class of antiferromagnetic Cr(7)Ni rings to identify the sources of decoherence. The optimal structure exhibits a phase memory time exceeding 15 µs.
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Imanes/química , Nanopartículas/química , Teoría Cuántica , Ácidos Carboxílicos/química , Compuestos de Cromo/química , Complejos de Coordinación/química , Electrones , Ligandos , Modelos Moleculares , Níquel/químicaRESUMEN
In this study, a red pigment of Serratia marcescens PTCC 1111 was purified and identified for antiproliferative activities in HT-29 and T47D cancer cell lines. (1)H-NMR spectroscopy and LC/MS analysis confirmed prodigiosin structure. The antiproliferative effects of prodigiosin were determined by employing the MTT assay. The changes in cell cycle pattern were studied with 4',6-diamidino-2-phenylindole (DAPI) reagent using flow cytometry assay, and Annexin V-PI method was used for apoptotic analysis. Results of MTT assay showed that HT-29 cells were more sensitive to prodigiosin than T47D cells. Prodigiosin-treated HT-29 cells showed increase in S phase and decrease in G2/M, but treated T47D cells showed cell cycle pattern relatively similar to Roswell Park Memorial Institute medium (RPMI). Apoptotic effect of prodigiosin was higher than doxorubicin in HT-29 cells. The data reported here indicate that prodigiosin is a promising antineoplastic agent that triggers apoptosis in different cancer cell lines.
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Apoptosis/efectos de los fármacos , Prodigiosina/farmacología , Serratia marcescens/química , Línea Celular Tumoral , Células HT29 , Humanos , Espectroscopía de Resonancia Magnética , Espectrometría de Masas , Prodigiosina/químicaRESUMEN
Superposition and entanglement are uniquely quantum phenomena. Superposition incorporates a phase that contains information surpassing any classical mixture. Entanglement offers correlations between measurements in quantum systems that are stronger than any that would be possible classically. These give quantum computing its spectacular potential, but the implications extend far beyond quantum information processing. Early applications may be found in entanglement-enhanced sensing and metrology. Quantum spins in condensed matter offer promising candidates for investigating and exploiting superposition and entanglement, and enormous progress is being made in quantum control of such systems. In gallium arsenide (GaAs), individual electron spins can be manipulated and measured, and singlet-triplet states can be controlled in double-dot structures. In silicon, individual electron spins can be detected by ionization of phosphorus donors, and information can be transferred from electron spins to nuclear spins to provide long memory times. Electron and nuclear spins can be manipulated in nitrogen atoms incarcerated in fullerene molecules, which in turn can be assembled in ordered arrays. Spin states of charged nitrogen vacancy centres in diamond can be manipulated and read optically. Collective spin states in a range of materials systems offer scope for holographic storage of information. Conditions are now excellent for implementing superposition and entanglement in spintronic devices, thereby opening up a new era of quantum technologies.
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We describe a low-temperature sample probe for the electrical detection of magnetic resonance in a resonant W-band (94 GHz) microwave cavity. The advantages of this approach are demonstrated by experiments on silicon field-effect transistors. A comparison with conventional low-frequency measurements at X-band (9.7 GHz) on the same devices reveals an up to 100-fold enhancement of the signal intensity. In addition, resonance lines that are unresolved at X-band are clearly separated in the W-band measurements. Electrically detected magnetic resonance at high magnetic fields and high microwave frequencies is therefore a very sensitive technique for studying electron spins with an enhanced spectral resolution and sensitivity.
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Molecular nanostructures may constitute the fabric of future quantum technologies, if their degrees of freedom can be fully harnessed. Ideally one might use nuclear spins as low-decoherence qubits and optical excitations for fast controllable interactions. Here, we present a method for entangling two nuclear spins through their mutual coupling to a transient optically excited electron spin, and investigate its feasibility through density-functional theory and experiments on a test molecule. From our calculations we identify the specific molecular properties that permit high entangling power gates under simple optical and microwave pulses; synthesis of such molecules is possible with established techniques.
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We propose to encode a register of quantum bits in different collective electron spin wave excitations in a solid medium. Coupling to spins is enabled by locating them in the vicinity of a superconducting transmission line cavity, and making use of their strong collective coupling to the quantized radiation field. The transformation between different spin waves is achieved by applying gradient magnetic fields across the sample, while a Cooper pair box, resonant with the cavity field, may be used to carry out one- and two-qubit gate operations.
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The interlayer magnetoresistance rho(zz) of the organic metal kappa-(BEDT-TTF)(2)Cu(NCS)(2) is studied in fields of up to 45 T and at temperatures T from 0.5 to 30 K. The peak in rho(zz) seen in in-plane fields, a definitive signature of interlayer coherence, remains to Ts exceeding the Anderson criterion for incoherent transport by a factor approximately 30. Angle-dependent magnetoresistance oscillations are modeled using an approach based on field-induced quasiparticle paths on a 3D Fermi surface, to yield the T dependence of the scattering rate tau(-1). The results suggest that tau(-1) does not vary strongly over the Fermi surface, and that it has a T(2) dependence due to electron-electron scattering.
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Most experts agree that it is too early to say how quantum computers will eventually be built, and several nanoscale solid-state schemes are being implemented in a range of materials. Nanofabricated quantum dots can be made in designer configurations, with established technology for controlling interactions and for reading out results. Epitaxial quantum dots can be grown in vertical arrays in semiconductors, and ultrafast optical techniques are available for controlling and measuring their excitations. Single-walled carbon nanotubes can be used for molecular self-assembly of endohedral fullerenes, which can embody quantum information in the electron spin. The challenges of individual addressing in such tiny structures could rapidly become intractable with increasing numbers of qubits, but these schemes are amenable to global addressing methods for computation.
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Peaks in the magnetoresistivity of the layered superconductor kappa - (BEDT-TTF)2Cu(NCS)(2), measured in fields < or =45 T applied within the layers, show that the Fermi surface is extended in the interlayer direction and enable the interlayer transfer integral (t( perpendicular) approximately 0.04 meV) to be deduced. However, the quasiparticle scattering rate tau(-1) is such that Planck's over 2pi/tau approximately 6t( perpendicular), implying that kappa - (BEDT-TTF)2Cu(NCS)(2) meets the criterion used to identify interlayer incoherence. The applicability of this criterion to anisotropic materials is thus shown to be questionable.
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We show that Shubnikov-de Haas oscillations in the interlayer resistivity of the organic superconductor beta(")-(BEDT-TTF)2SF5CH2CF2SO3 become very pronounced in magnetic fields approximately 60 T. The conductivity minima exhibit thermally activated behavior that can be explained simply by the presence of a Landau gap, with the quasi-one-dimensional Fermi surface sheets contributing negligibly to the conductivity. This observation, together with complete suppression of chemical potential oscillations, is consistent with an incommensurate nesting instability of the quasi-one-dimensional sheets.