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1.
Phys Chem Chem Phys ; 25(9): 6684-6692, 2023 Mar 01.
Artículo en Inglés | MEDLINE | ID: mdl-36806473

RESUMEN

We have combined the extended X-ray absorption fine structure (EXAFS) and X-ray emission spectroscopy (XES) to investigate the local structure and the local iron magnetic moments of (Li1-xFex)OHFeSe (x∼0.2) superconductors. The local structure, studied by Fe K-edge EXAFS measurements, is found to be inhomogeneous that is characterized by different Fe-Se bond lengths. The inhomogeneous phase exhibits a peculiar temperature dependence with lattice anomalies in the local structural parameters at the critical temperature Tc (36 K) and at the spin density wave (SDW) transition temperature TN (130 K). Fe Kß XES shows iron to be in a low spin state with the local Fe magnetic moment evolving anomalously as a function of temperature. Apart from a quantitative measurement of the local structure of (Li1-xFex)OHFeSe, providing direct evidence of nanoscale inhomogeneity, the results provide further evidence of the vital role that the coupled electronic, lattice and magnetic degrees of freedom play in the iron-based superconductors.

2.
Clin Radiol ; 75(5): 397.e15-397.e21, 2020 05.
Artículo en Inglés | MEDLINE | ID: mdl-31987487

RESUMEN

AIM: To evaluate and compare diffusion-weighted imaging (DWI) parameters derived from a non-Gaussian fitting model and positron-emission tomography (PET) parameters derived from 18F-fluoromisonidazole-PET (FMISO-PET) in patients with oral squamous cell carcinoma (OSCC). MATERIALS AND METHODS: Primary sites were evaluated prospectively in 18 patients. DWI was performed using six b-values (0-2,500). Diffusion-related parameters of kurtosis value (K), the kurtosis-corrected diffusion coefficient (DK), diffusion heterogeneity (α), distributed diffusion coefficient (DDC), the slow diffusion coefficient (Dslow), and the apparent diffusion coefficient (ADC) were calculated from four diffusion-fitting models. Maximal standardised uptake values (SUVmax), mean standardised uptake values (SUVmean), and the tumour-to-muscle ration (TMR) of the SUV value were calculated for FMISO-PET. Spearman's correlation coefficient was used to evaluate the correlation between each non-Gaussian diffusion model parameters and PET parameter. RESULTS: There was moderate correlation between FMISO-PET SUVmax and Dslow (ρ=-0.45, p=0.06). In addition, there was good correlation between TMRmax and five non-Gaussian diffusion model parameters (K: ρ=0.65, p=0.004, DK: ρ=-0.72, p=0.0008, DDC: ρ=-0.75, p=0.0003, ADC: ρ=-0.74, p=0.0005, and Dslow: ρ= -0.65, p=0.003), and between TMRmean and five non-Gaussian model parameters (K: ρ=0.64, p=0.005, DK: ρ=-0.61, p=0.007, DDC: ρ=-0.63, p=0.005, ADC: ρ=-0.61, p=0.007, and Dslow: ρ=-0.56, p=0.015). CONCLUSION: Non-Gaussian diffusion model parameters can be related to tumour hypoxia.


Asunto(s)
Carcinoma de Células Escamosas/diagnóstico por imagen , Imagen de Difusión por Resonancia Magnética/métodos , Neoplasias de la Boca/diagnóstico por imagen , Tomografía de Emisión de Positrones/métodos , Anciano , Anciano de 80 o más Años , Femenino , Humanos , Masculino , Persona de Mediana Edad , Misonidazol/análogos & derivados , Estudios Prospectivos , Radiofármacos
4.
Clin Radiol ; 73(12): 1059.e1-1059.e8, 2018 12.
Artículo en Inglés | MEDLINE | ID: mdl-30245069

RESUMEN

AIM: To assess potential prognostic factors in pharynx squamous cell carcinoma (SCC) patients by quantitative morphological and intratumoural characteristics obtained by 2-[18F]-fluoro-2-deoxy-d-glucose positron-emission tomography/computed tomography (FDG-PET/CT). MATERIALS AND METHODS: The cases of 54 patients with pharynx SCC who underwent chemoradiation therapy were analysed retrospectively. Using their FDG-PET data, the quantitative morphological and intratumoural characteristics of 14 parameters were calculated. The progression-free survival (PFS) and overall survival (OS) information was obtained from patient medical records. Univariate and multivariate analyses were performed to assess the 14 quantitative parameters as well as the T-stage, N-stage, and tumour location data for their relation to PFS and OS. When an independent predictor was suggested in the multivariate analysis, the parameter was further assessed using the Kaplan-Meier method. RESULTS: In the assessment of PFS, the univariate and multivariate analyses indicated the following as independent predictors: the texture parameter of homogeneity and the morphological parameter of sphericity. In the Kaplan-Meier analysis, the PFS rate was significantly improved in the patients who had both a higher value of homogeneity (p=0.01) and a higher value of sphericity (p=0.002). With the combined use of homogeneity and sphericity, the patients with different PFS rates could be divided more clearly. CONCLUSION: The quantitative parameters of homogeneity and sphericity obtained by FDG-PET can be useful for the prediction of the PFS of pharynx SCC patients, especially when used in combination.


Asunto(s)
Neoplasias Laríngeas/diagnóstico por imagen , Recurrencia Local de Neoplasia/diagnóstico por imagen , Tomografía Computarizada por Tomografía de Emisión de Positrones , Carcinoma de Células Escamosas de Cabeza y Cuello/diagnóstico por imagen , Tomografía Computarizada por Rayos X , Adulto , Anciano , Quimioradioterapia , Femenino , Humanos , Neoplasias Laríngeas/patología , Masculino , Persona de Mediana Edad , Recurrencia Local de Neoplasia/patología , Pronóstico , Radiofármacos , Estudios Retrospectivos , Carcinoma de Células Escamosas de Cabeza y Cuello/patología , Tasa de Supervivencia , Carga Tumoral
5.
Folia Morphol (Warsz) ; 77(2): 286-292, 2018.
Artículo en Inglés | MEDLINE | ID: mdl-29064554

RESUMEN

BACKGROUND: Anatomical knowledge of the duodenojejunal flexure is necessary for abdominal surgeries, and also important for physiologic studies about the duodenum. But little is known about the anatomy of this region in mammals. Here, we examined comparative anatomy to understand the anatomical formation of the duodenojejunal flexure in mammals. MATERIALS AND METHODS: The areas around the duonenojejunal flexure were ob-served in mouse, rat, dog, pig, and human, and the anatomical structures around the duodenojejunal junction in the animals were compared with those in human. RESULTS: The superior and inferior duodenal folds, and the superior and inferior duodenal fossae were identified in all examined humans. In pig, the structures were not clearly identified because the duodenum strongly adhered to the retroperitoneum and to the mesocolon. In mouse, rat, and dog, only the plica duodenocolica, which is regarded as the animal counterpart of the superior duo-denal fold in human, was identified, and other folds or fossae were not observed, probably because the duodenum was not fixed to the parietal peritoneum in those animals. Transection of the plica duodenocolica could return the normally rotated intestine back to the state of non-rotation in rat. CONCLUSIONS: This study showed the anatomical similarities and dissimilarities of the duodenojejunal flexure among the mammals. Anatomical knowledge of the area is useful for duodenal and pancreatic surgeries, and for animal studies about the duodenum. (Folia Morphol 2018; 77, 2: 286-292).


Asunto(s)
Duodeno/anatomía & histología , Yeyuno/anatomía & histología , Anatomía Comparada , Animales , Perros , Humanos , Ratas , Especificidad de la Especie , Porcinos
6.
Br Poult Sci ; 58(4): 348-357, 2017 Aug.
Artículo en Inglés | MEDLINE | ID: mdl-28418277

RESUMEN

1. The skulls and postcranial skeletons of the red jungle fowl (Gallus gallus) were compared osteometrically between the populations from North and South Vietnam, North and Central Laos and Southeast Bangladesh. The populations include the three subspecies of G. g. spadiceus, G. g. gallus and G. g. murghi and were sampled to reveal the geographical morphological variations among populations in G. gallus. 2. The morphometric characteristics of subspecies murghi could be clearly distinguished from those of the other subspecies using a canonical discriminant analysis. However, the size and shape of the skull of the gallus population from South Vietnam were not statistically different from that of the subspecies spadiceus from North Laos. The canonical discriminant scores also clearly indicated that there were morphological similarities in the skulls of the populations from North Laos and South Vietnam. 3. From the results, therefore, it is concluded that red jungle fowls do not exhibit high levels of osteometric variation between geographical localities at least within the Indochinese Peninsula. 4. This contrasts with previous studies which have described these subspecies as having various external morphological differences and have argued that zoogeographical barriers exist between the north and south areas of the Indochinese Peninsula.


Asunto(s)
Huesos/anatomía & histología , Pollos/anatomía & histología , Animales , Bangladesh , Femenino , Laos , Masculino , Cráneo/anatomía & histología , Vietnam
7.
Ann Oncol ; 26(12): 2477-82, 2015 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-26420428

RESUMEN

BACKGROUND: The clinical implementation of genomic profiling for lung cancer with high-throughput, multiplex tests is warranted to allow prioritization of appropriate therapies for individual patients. We have now applied such testing to detect actionable mutations that may inform treatment recommendations in lung cancer. PATIENTS AND METHODS: We prospectively applied amplicon sequencing panels that cover both mutational hotspots in 22 genes related to lung and colon tumorigenesis as well as 72 major variants of ALK, RET, ROS1, and NTRK1 fusion transcripts. We then determined the proportion of patients who received genotype-directed therapy and their overall survival (OS). RESULTS: Tumor specimens from 110 patients with lung cancer recruited between July 2013 and March 2015 were analyzed. The most common genetic alterations were TP53 mutations in 42 patients, followed by EGFR mutations in 25, STK11 mutations in 12, and KRAS mutations in 10. Potentially actionable mutations were identified in 44 patients including 50% of those with adenocarcinoma and 14% of those with squamous cell carcinoma. The OS of patients with advanced or recurrent cancer who had an actionable mutation and received targeted therapy (median OS not achieved) was significantly longer than that of those with no mutation (18.1 months, P = 0.041) or of those with a mutation not so treated (6.1 months, P = 0.0027). CONCLUSIONS: Multiplex genomic testing was performed on formalin-fixed, paraffin-embedded tumor specimens with a success rate of ≥95%. Such testing can assist physicians in matching patients with approved or experimental targeted treatments. CLINICAL TRIAL REGISTRATION: The University Medical Hospital Information Network (UMIN) Clinical Trials Registry under the identifier UMIN000014782.


Asunto(s)
Toma de Decisiones Clínicas/métodos , Secuenciación de Nucleótidos de Alto Rendimiento/métodos , Neoplasias Pulmonares/diagnóstico , Neoplasias Pulmonares/genética , Análisis de Secuencia de ARN/métodos , Adulto , Anciano , Anciano de 80 o más Años , Femenino , Humanos , Masculino , Persona de Mediana Edad , Estudios Prospectivos , Sistema de Registros
8.
Phys Rev Lett ; 114(5): 056402, 2015 Feb 06.
Artículo en Inglés | MEDLINE | ID: mdl-25699459

RESUMEN

We report on the real space profile of spin polarons in the quasi-two-dimensional frustrated dimer spin system SrCu(2)(BO(3))(2) doped with 0.16% of Zn. The (11)B nuclear magnetic resonance spectrum exhibits 15 additional boron sites near nonmagnetic Zn impurities. With the help of exact diagonalizations of finite clusters, we have deduced from the boron spectrum, the distribution of local magnetizations at the Cu sites with fine spatial resolution, providing direct evidence for an extended spin polaron. The results are confronted with those of other experiments performed on doped and undoped samples of SrCu(2)(BO(3))(2).

9.
Transpl Infect Dis ; 17(5): 728-31, 2015 Oct.
Artículo en Inglés | MEDLINE | ID: mdl-26176562

RESUMEN

We analyzed 3 hematopoietic stem cell transplant (HSCT) recipients with inherited chromosomally integrated human herpesvirus-6 (inherited CIHHV-6). Cases 1 (inherited CIHHV-6A) and 2 (inherited CIHHV-6B) were inherited CIHHV-6 recipients. Case 3 received bone marrow from a donor with inherited CIHHV-6B. Following HSCT, HHV-6B was isolated from Case 1. HHV-6A and -6B messenger RNAs were detected in Cases 1 and 3.


Asunto(s)
ADN Viral/aislamiento & purificación , Trasplante de Células Madre Hematopoyéticas , Herpesvirus Humano 6/genética , Integración Viral , Niño , Preescolar , Femenino , Herpesvirus Humano 6/aislamiento & purificación , Humanos , Masculino , Adulto Joven
11.
Phys Rev Lett ; 110(26): 265502, 2013 Jun 28.
Artículo en Inglés | MEDLINE | ID: mdl-23848894

RESUMEN

High resolution resonant inelastic x-ray scattering has been performed to reveal the role of lattice coupling in a family of quasi-1D insulating cuprates, Ca2+5xY2-5xCu5O10. Site-dependent low-energy excitations arising from progressive emissions of a 70 meV lattice vibrational mode are resolved for the first time, providing a direct measurement of electron-lattice coupling strength. We show that such electron-lattice coupling causes doping-dependent distortions of the Cu-O-Cu bond angle, which sets the intrachain spin exchange interactions. Our results indicate that the lattice degrees of freedom are fully integrated into the electronic behavior in low-dimensional systems.

12.
Clin Exp Immunol ; 167(2): 269-74, 2012 Feb.
Artículo en Inglés | MEDLINE | ID: mdl-22236003

RESUMEN

The activation of nuclear factor-kappa B (NF-κB) in vascular endothelial cells may be involved in vascular pathogeneses such as vasculitis or atherosclerosis. Recently, it has been reported that some amino acids exhibit anti-inflammatory effects. We investigated the inhibitory effects of a panel of amino acids on cytokine production or expression of adhesion molecules that are involved in inflammatory diseases in various cell types. The activation of NF-κB was determined in human coronary arterial endothelial cells (HCAECs) because NF-κB modulates the production of many cytokines and the expression of adhesion molecules. We examined the inhibitory effects of the amino acids cysteine, histidine and glycine on the induction of NF-κB activation, expression of CD62E (E-selectin) and the production of interleukin (IL)-6 in HCAECs stimulated with tumour necrosis factor (TNF)-α. Cysteine, histidine and glycine significantly reduced NF-κB activation and inhibitor κBα (IκBα) degradation in HCAECs stimulated with TNF-α. Additionally, all the amino acids inhibited the expression of E-selectin and the production of IL-6 in HCAECs, and the effects of cysteine were the most significant. Our results show that glycine, histidine and cysteine can inhibit NF-κB activation, IκBα degradation, CD62E expression and IL-6 production in HCAECs, suggesting that these amino acids may exhibit anti-inflammatory effects during endothelial inflammation.


Asunto(s)
Antiinflamatorios/farmacología , Arteritis/prevención & control , Vasos Coronarios/citología , Cisteína/farmacología , Células Endoteliales/efectos de los fármacos , Glicina/farmacología , Histidina/farmacología , Células Cultivadas/efectos de los fármacos , Células Cultivadas/metabolismo , Evaluación Preclínica de Medicamentos , Selectina E/biosíntesis , Selectina E/genética , Células Endoteliales/metabolismo , Endotelio Vascular/citología , Regulación de la Expresión Génica/efectos de los fármacos , Humanos , Proteínas I-kappa B/metabolismo , Interleucina-6/biosíntesis , Interleucina-6/genética , Inhibidor NF-kappaB alfa , FN-kappa B/metabolismo , Factor de Necrosis Tumoral alfa/farmacología
13.
Phys Rev Lett ; 109(9): 097002, 2012 Aug 31.
Artículo en Inglés | MEDLINE | ID: mdl-23002873

RESUMEN

The effects of phosphorus doping on the structural and superconducting phase transitions of BaNi2(As(1-x)P(x))2 were studied. The specific heat, resistivity, and magnetic susceptibility were measured. The results revealed an abrupt increase in the superconducting transition temperature (T(c)) from 0.6 K in the triclinic phase (space group P1¯) with less phosphorus (x≤0.067) to 3.3 K in the tetragonal phase (space group I4/mmm) with more phosphorus (x≥0.067). Our data analysis suggests that a doping-induced softening related to an in-plane Ni and As(P) phonon mode is responsible for the enhanced superconductivity in the tetragonal phase.

14.
Br J Cancer ; 105(8): 1131-6, 2011 Oct 11.
Artículo en Inglés | MEDLINE | ID: mdl-21915126

RESUMEN

BACKGROUND: Currently, no effective treatments exist for non-small cell lung cancer (NSCLC) after failure of gefitinib therapy. Pre-clinical studies have demonstrated that gefitinib-resistant NSCLC cells are more sensitive to irinotecan than parental cells, and that combined administration of irinotecan and gefitinib has a synergistic additive effect. We conducted a phase I study to evaluate the combination of irinotecan and gefitinib as a therapeutic option for NSCLC patients with progressive disease (PD) after initial gefitinib treatment. METHODS: Eligibility criteria included histologically confirmed NSCLC, age range of 20-74 years, refractory to or relapsed after gefitinib treatment, one or more previous chemotherapy regimens, Eastern Cooperative Oncology Group performance status 0-2, adequate organ function, and informed consent. Patients were treated with irinotecan on days 1 and 15, and treated daily with gefitinib from day 2 every 4 weeks. The treatment was continued until disease progression. The gefitinib dose was fixed at 250 mg. Irinotecan dosing started at 50 mg m(-2) and was escalated in patients by 25 mg m(-2) increments up to a maximum dose of 150 mg m(-2). RESULTS: Twenty-seven patients were enrolled: male/female=14/13; median age=60 (45-75); histology, adenocarcinoma/non-adenocarcinoma=25/2; performance status 0-1/2=19/8; previous response to gefitinib, partial response/stable disease/PD=21/2/4. Dose-limiting toxicities were observed in 2 patients at level 3. Maximum tolerated dose was not determined, and the full dose of irinotecan could be combined with the full dose of gefitinib. The disease control rate (DCR) and response rate (RR) were 69.2 and 26.9%, respectively. For 12 patients at level 5 (the recommended phase II dose), the DCR and RR were 75.0% and 41.7%, respectively. The median treatment cycles were 4; median time to treatment failure, 57 days (95% confidence interval (CI), 32-82 days); median overall survival, 244 days (95% CI, 185-303 days); and 1-year survival rate, 32.6%. CONCLUSION: The combination of irinotecan and gefitinib was well tolerated and potentially beneficial for NSCLC patients failing initial gefitinib monotherapy.


Asunto(s)
Protocolos de Quimioterapia Combinada Antineoplásica/uso terapéutico , Carcinoma de Pulmón de Células no Pequeñas/tratamiento farmacológico , Neoplasias Pulmonares/tratamiento farmacológico , Anciano , Protocolos de Quimioterapia Combinada Antineoplásica/efectos adversos , Camptotecina/administración & dosificación , Camptotecina/análogos & derivados , Receptores ErbB/genética , Femenino , Gefitinib , Humanos , Irinotecán , Masculino , Dosis Máxima Tolerada , Persona de Mediana Edad , Mutación , Quinazolinas/administración & dosificación , Resultado del Tratamiento
15.
Br J Cancer ; 105(8): 1210-7, 2011 Oct 11.
Artículo en Inglés | MEDLINE | ID: mdl-21897392

RESUMEN

BACKGROUND: Activin A is a multi-functional cytokine belonging to the transforming growth factor-ß (TGF-ß) superfamily; however, the effect of activin A on angiogenesis remains largely unclear. We found that inhibin ß A subunit (INHBA) mRNA is overexpressed in gastric cancer (GC) specimens and investigated the effect of activin A, a homodimer of INHBA, on angiogenesis in GC. METHODS: Anti-angiogenic effects of activin A via p21 induction were evaluated using human umbilical vein endothelial cells (HUVECs) in vitro and a stable INHBA-introduced GC cell line in vivo. RESULTS: Compared with TGF-ß, activin A potently inhibited the cellular proliferation and tube formation of HUVECs with induction of p21. A promoter assay and a chromatin immunoprecipitation assay revealed that activin A directly regulates p21 transcriptional activity through Smads. Stable p21-knockdown significantly enhanced the cellular proliferation of HUVECs. Notably, stable p21-knockdown exhibited a resistance to activin-mediated growth inhibition in HUVECs, indicating that p21 induction has a key role on activin A-mediated growth inhibition in vascular endothelial cells. Finally, a stable INHBA-introduced GC cell line exhibited a decrease in tumour growth and angiogenesis in vivo. CONCLUSION: Our findings highlight the suppressive role of activin A, unlike TGF-ß, on tumour growth and angiogenesis in GC.


Asunto(s)
Activinas/fisiología , Neovascularización Patológica/prevención & control , Neoplasias Gástricas/irrigación sanguínea , Factor A de Crecimiento Endotelial Vascular/antagonistas & inhibidores , Animales , Secuencia de Bases , Proliferación Celular , Células Cultivadas , Inmunoprecipitación de Cromatina , Inhibidor p21 de las Quinasas Dependientes de la Ciclina/metabolismo , Cartilla de ADN , Ensayo de Inmunoadsorción Enzimática , Femenino , Humanos , Ratones , Ratones Endogámicos BALB C , Ratones Desnudos , Fosforilación , Proteína Smad2/metabolismo , Neoplasias Gástricas/patología
17.
Neotrop Entomol ; 48(3): 368-372, 2019 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-30488360

RESUMEN

Social insects face strong selection from parasites because the conditions of group living often favor the transmission of infection among nestmates. However, there is little detailed information on the effects of parasite infection in the host species. Workers of Polybia species, neotropical swarm-founding wasps, are commonly infected by gregarines, protozoans that are exclusively parasitic on invertebrates. Previous studies showed that high rates of gregarine infection in workers of Polybia occidentalis (Olivier) have negative effects on their colony performance. However, the effect of seasonality on infection rates throughout the year or between wet and dry seasons has not been examined. Host-parasite interactions cannot be understood without consideration of the overall population dynamic. We compared rates of gregarine infection in workers of Polybia paulista (Ihering) between wet and dry seasons and among months. The 35% rate was by far the highest of the four wet seasons sampled, but the rates declined in the mid-wet season and were very low during the dry season. Strong seasonal differences in infection rates were also observed between the dry and wet seasons. Several potential factors affecting the seasonal differences are discussed.


Asunto(s)
Apicomplexa/aislamiento & purificación , Estaciones del Año , Avispas/parasitología , Animales , Apicomplexa/patogenicidad , Brasil , Interacciones Huésped-Parásitos
18.
Transplant Proc ; 51(2): 579-584, 2019 Mar.
Artículo en Inglés | MEDLINE | ID: mdl-30879594

RESUMEN

Cholangitis is a major complication following transplantation. We report a living donor liver transplant (LDLT) patient with cholangitis due to multiple stones in the intrahepatic bile duct during hepaticojejunostomy anastomosis, who was successfully treated with the rendezvous technique using double balloon endoscope. A 64-year-old woman underwent LDLT with right lobe graft and hepaticojejunostomy for Wilson disease. There was bile leakage with biliary peritonitis, which was treated conservatively after transplant. Two years after surgery, she developed reiterated cholangitis due to stenosis of hepaticojejunostomy anastomosis and multiple stones in the intrahepatic bile ducts. Percutaneous transhepatic biliary drainage was performed. The size of the drainage tube was increased, and the anastomotic area was dilated in a stepwise manner using a balloon catheter. The stones were crushed and lithotomy was performed using electronic hydraulic lithotripsy through cholangioscopy. Finally, lithotomy was performed for the remaining stones through endoscopic retrograde cholangiography with the rendezvous technique using the double balloon endoscope. Rendezvous approach with percutaneous transhepatic biliary drainage and double balloon endoscopic retrograde cholangiography was an effective treatment for the multiple intrahepatic stones in hepaticojejunostomy following LDLT with right lobe graft.


Asunto(s)
Enteroscopia de Balón/métodos , Procedimientos Quirúrgicos del Sistema Biliar/métodos , Cálculos Biliares/cirugía , Trasplante de Hígado/efectos adversos , Complicaciones Posoperatorias/cirugía , Anastomosis Quirúrgica , Conductos Biliares Intrahepáticos/patología , Conductos Biliares Intrahepáticos/cirugía , Colangitis/etiología , Colangitis/cirugía , Femenino , Cálculos Biliares/etiología , Humanos , Donadores Vivos , Persona de Mediana Edad
19.
Phys Rev E Stat Nonlin Soft Matter Phys ; 77(5 Pt 2): 055203, 2008 May.
Artículo en Inglés | MEDLINE | ID: mdl-18643121

RESUMEN

We investigate quantum dynamics in phase-space regions containing "shearless tori." We show that the properties of these peculiar classical phase-space structures-important to the dynamics of tokamaks-may be exploited for quantum information applications. In particular we show that shearless tori permit the nondispersive transmission of localized wave packets. The quantum many-body Hamiltonian of a Heisenberg ferromagnetic spin chain, subjected to an oscillating magnetic field, can be reduced to a classical one-body "image" dynamical system which is the well-studied Harper map. The Harper map belongs to a class of Hamiltonian systems (nontwist maps) which contain shearless tori. We show that a variant with sinusoidal time driving "driven Harper model" produces shearless tori which are especially suitable for quantum state transfer. The behavior of the concurrence is investigated as an example.

20.
J Magn Reson ; 296: 1-4, 2018 Nov.
Artículo en Inglés | MEDLINE | ID: mdl-30165264

RESUMEN

We have developed a high-pressure electron spin resonance probe and successfully installed into the world's highest-field cryogen-free superconducting magnet having a maximum central field of 24.6 T. The high pressure of 2.5 GPa is achieved by the specially designed piston-cylinder pressure cell using THz-wave-transparent components. In the first application of this high-pressure high-field ESR system, we observed that the orthogonal dimer spin system SrCu2(BO3)2 undergoes a quantum phase transition from the dimer singlet ground to the plaquette singlet ground states.

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