X-ray reflectivity of chemically vapor-deposited diamond single crystals in the Laue geometry.

The absolute X-ray reflectivity of chemically vapor-deposited (CVD) single-crystal diamond plates was measured in the Laue geometry in the double-crystal non-dispersive setting with an asymmetric Si beam-conditioner crystal. The measurements were supplemented by rocking-curve topography. The measured reflectivity curves are examined in the framework of the Darwin-Hamilton approach using a set of two independent parameters: the characteristic thickness of mosaic blocks and their average angular misorientation. Owing to strong extinction effects, the width of the reflectivity curves does not directly represent the average misorientation of the blocks. Two different sets of parameters were found for the 111 asymmetric reflection in the two different scattering configurations (beam compression and beam expansion). Analysis of the rocking-curve topographs shows that this discrepancy can be attributed to inhomogeneity of the diamond crystal microstructure.

Spatial displacement of forward-diffracted X-ray beams by perfect crystals.

Time-delayed, narrow-band echoes generated by forward Bragg diffraction of an X-ray pulse by a perfect thin crystal are exploited for self-seeding at hard X-ray free-electron lasers. Theoretical predictions indicate that the retardation is strictly correlated to a transverse displacement of the echo pulses. This article reports the first experimental observation of the displaced echoes. The displacements are in good agreement with simulations relying on the dynamical diffraction theory. The echo signals are characteristic for a given Bragg reflection, the structure factor and the probed interplane distance. The reported results pave the way to exploiting the signals as an online diagnostic tool for hard X-ray free-electron laser seeding and for dynamical diffraction investigations of strain at the femtosecond timescale.

Observation of a Charge Density Wave Incommensuration Near the Superconducting Dome in Cu_{x}TiSe_{2}.

X-ray diffraction was employed to study the evolution of the charge density wave (CDW) in Cu_{x}TiSe_{2} as a function of copper intercalation in order to clarify the relationship between the CDW and superconductivity. The results show a CDW incommensuration arising at an intercalation value coincident with the onset of superconductivity at around x=0.055(5). Additionally, it was found that the charge density wave persists to higher intercalant concentrations than previously assumed, demonstrating that the CDW does not terminate inside the superconducting dome. A charge density wave peak was observed in samples up to x=0.091(6), the highest copper concentration examined in this study. The phase diagram established in this work suggests that charge density wave incommensuration may play a role in the formation of the superconducting state.

Structural origin of the anomalous temperature dependence of the local magnetic moments in the CaFe2As2 family of materials.

We report a combination of Fe Kß x-ray emission spectroscopy and density functional reduced Stoner theory calculations to investigate the correlation between structural and magnetic degrees of freedom in CaFe2(As1-xPx)2. The puzzling temperature behavior of the local moment found in rare earth-doped CaFe2As2 [H. Gretarsson et al., Phys. Rev. Lett. 110, 047003 (2013)] is also observed in CaFe2(As1-xPx)2. We explain this phenomenon based on first-principles calculations with scaled magnetic interaction. One scaling parameter is sufficient to describe quantitatively the magnetic moments in both CaFe2(As1-xPx)2 (x=0.055) and Ca0.78La0.22Fe2As2 at all temperatures. The anomalous growth of the local moments with increasing temperature can be understood from the observed large thermal expansion of the c-axis lattice parameter combined with strong magnetoelastic coupling. These effects originate from the strong tendency to form As-As dimers across the Ca layer in the CaFe2As2 family of materials. Our results emphasize the dual local-itinerant character of magnetism in Fe pnictides.

A galaxy rapidly forming stars 700 million years after the Big Bang at redshift 7.51.

Of several dozen galaxies observed spectroscopically that are candidates for having a redshift (z) in excess of seven, only five have had their redshifts confirmed via Lyman α emission, at z = 7.008, 7.045, 7.109, 7.213 and 7.215 (refs 1-4). The small fraction of confirmed galaxies may indicate that the neutral fraction in the intergalactic medium rises quickly at z > 6.5, given that Lyman α is resonantly scattered by neutral gas. The small samples and limited depth of previous observations, however, makes these conclusions tentative. Here we report a deep near-infrared spectroscopic survey of 43 photometrically-selected galaxies with z > 6.5. We detect a near-infrared emission line from only a single galaxy, confirming that some process is making Lyman α difficult to detect. The detected emission line at a wavelength of 1.0343 micrometres is likely to be Lyman α emission, placing this galaxy at a redshift z = 7.51, an epoch 700 million years after the Big Bang. This galaxy's colours are consistent with significant metal content, implying that galaxies become enriched rapidly. We calculate a surprisingly high star-formation rate of about 330 solar masses per year, which is more than a factor of 100 greater than that seen in the Milky Way. Such a galaxy is unexpected in a survey of our size, suggesting that the early Universe may harbour a larger number of intense sites of star formation than expected.

Rol de la rinometría acústica en la evaluación de los pacientes candidatos a rinoseptoplastía / Role of acoustic rhinometry in assessing rhinoseptoplasty candidates

Introducción: La obstrucción nasal es un síntoma de difícil evaluación particularmente en pacientes candidatos a rinoseptoplastía. Existen diferentes métodos para valorarla, dentro de los cuales se encuentra la rinometría acústica, la cual entrega las áreas transversales y volúmenes nasales en función de la distancia desde las narinas. Objetivos: El objetivo del presente trabajo fue compararlos resultados de la rinometría acústica con los obtenidos por otros métodos de evaluación de la obstrucción nasal. Material y método: Se diseñó un estudio prospectivo, descriptivo. Se evaluaron 26 fosas nasales correspondientes a 13 pacientes candidatos a rinoseptoplastía, mediante rinoscopía anterior, endoscopía nasal, rinomanometría y sensación subjetiva de obstrucción nasal referida por el paciente. Luego se comparó dicha evaluación con los datos obtenidos mediante la rinometría acústica. Resultados: Se obtuvo una buena asociación entre los valores entregados por la rinometría acústica y tanto la sensación subjetiva de obstrucción nasal referida por el paciente como la rinomanometría. Por otra parte, no hubo buena asociación entre la rinometría acústica y tanto la rinoscopía anterior como la endoscopía. Conclusiones: La rinometría acústica es una herramienta útil para la evaluación de la obstrucción nasal de pacientes candidatos a rinoseptoplatía, sin embargo no reemplaza la correcta valoración clínica.

Introduction: Nasal obstruction is difficult to evaluate, particularly in candidates to rhinoseptoplasty. One of the methods available to assess nasal obstruction is acoustic rhinometry, which yields an estimate of nasal cross-sectional area and nasal volume as a function of distance from the nostrils. Aim: The aim of this study was to compare results from acoustic rhinometry to those obtained using other nasal obstruction evaluation methods. Alternative methods used were: Anterior rhinoscopy nasal endoscopy rhinomanometry, and subjective sensation of nasal obstruction as reported by the patient. Material and method: A prospective, descriptive study design was used, evaluating a total of 26 patients. Results: A good association was found between the values produced by acoustic rhinometry and those obtained by rhinomanometry and the subjective sensation of nasal obstruction reported by patients. On the other hand, the association between acoustic rhinometry and both anterior rhinoscopy and nasal endoscopy was weak. Conclusion: Acoustic rhinometry is an useful tool for assessing nasal obstruction in rhinoseptoplasty patients. However, it does not surpass a good clinical evaluation.

Tratamiento médico de la rinosinusitis crónica / Medical treatment of chronic rhinosinusitis: literature review

La rinosinusitis crónica (RSC) es actualmente una de las patologías crónicas de mayor prevalencia en nuestra sociedad. Se distinguen dos formas clínicas: la RSC con pólipos (RSCCP) y la RSC sin pólipos (RSCSP). Es considerada, en términos generales, como una inflamación de la cavidad nasal y senos paranasales de una duración superior a 12 semanas. En la actualidad, los posibles mecanismos fisiopatológicos involucrados ubican al componente inflamatorio como entidad central en su etiología. La relación entre inflamación y poliposis nasal es aún objeto de gran debate. Existen distintos tratamientos médicos con evidencia científica de diferentes niveles de calidad, dentro de los cuales se encuentran antibióticos, corticoides, lavados nasales y antileucotrienos. El uso de macrólidos en bajas dosis y por períodos prolongados de tiempo surge como una eficaz alternativa tanto en el control de síntomas como de parßmetros objetivos, principalmente en pacientes con RSCSP. Este artículo efectúa una exposición respecto al tratamiento médico actualmente disponible, su eficacia y evidencia científica, tanto para la RSCP como para la RSCSP.

Chronic rhinosinusitis (CRS) is currently one of the most prevalent chronic pathologies in Chile. Two forms are distinguishable: Polyp CRS and non-polyp CRS. CRS is condidered, generally speaking, an inflammation of the nasal cavities and paranasal sinuses lasting longer than 12 weeks. Current possible physiopathological mechanisms involved establish inflammation as a central entity in CRS etiology. The relationship between inflammation and nasal polyposis is still a matter of great debate. Several treatment options are available, supported by heterogeneous scientific evidence; among these are antibiotics, corticoids, nasal rinses and antileucotriens. Prolonged treatment with low-dose macrolides treatment has become a good alternative, effectively controlling both symptoms and objective parameters, mainly in non-polyp CRS. This article reviews the CRS medical treatment currently available, its efficacy and the scientific evidence supporting it, both for the polyp and non-polyp types.

Actualización en disfunción tubaria: rol de la endoscopía nasal en su evaluación y tratamiento / Auditory tube dysfunction update: role of nasal endoscopy in its evaluation and treatment

La disfunción tubaria es uno de las patologías más estudiadas como responsable de diversas afecciones del oído medio. Dentro de sus factores causales se ha postulado un potencial rol de la rinitis alérgica, el reflujo gastrolaríngeo y la exposición a humo de tabaco, lo cual no ha podido ser comprobado consistentemente en estudios clínicos. En los últimos años, la endoscopía del extremo nasofaríngeo de la trompa de Eustaquio ha surgido como una nueva herramienta para evaluar el funcionamiento de esta estructura. Es así como el uso de cámara lenta ha podido mostrar que la mayoría de sus alteraciones parecen ser funcionales más que anatómicas u obstructivas. Por otra parte, esta evaluación endoscópica ha fomentado el desarrollo de nuevas técnicas quirúrgicas, basadas en la resección del colchón posterior del torus tubario mediante el uso del láser o microdebridador De este modo, en un futuro la endoscopía nasal pudiera tener un rol importante en la evaluación y manejo de la disfunción tubaria. Sin embargo, todavía no se establecen los candidatos ideales para dichos procedimientos.

Auditory tube dysfunction is one of the most studied middie ear diseases. Among its proposed risk factors, the etiologic role of allergic rhinitis, gastrolaryngeal reflux and tobacco smoke has not been demonstrated yet in clinical trials. In the last few years, endoscopic visualization of the nasopharyngeal end of the auditory tube became a new tool to evaluate this structure, particularly in association to slow motion video recordings. These techniques have shown that in most cases, the alterations seem to be functional rather than anatomic or obstructive. In addition, endoscopic evaluation has encouraged the development of new surgical techniques based on the resection of the posterior cushion of the torus tubarius, with the use of a laser or a microdebrider In the future, nasal endoscopy could have an important role in the evaluation and management of auditory tube dysfunction. However, the ideal candidates for these procedures are yet to be established.

Factores predictores de conducta en la evaluación inicial de pacientes pediátricos con megauréter primario / Management predicting factors in the evaluation of pediatric patients with primary megaureter

El Megauréter Primario no Refluyente (MPNR) es una patología con alta resolución espontánea. El presente trabajo pretende estudiar como diferentes factores clínicos e imagenológicos objetivados en la evaluación inicial predicen aquellos pacientes que van a requerir conducta quirúrgica. Materiales y Métodos: Se realizó un análisis retrospectivo de pacientes con diagnóstico de MPNR diagnosticados entre el año 1995 y 2005. Se utilizó estadística descriptiva y test de chi-cuadrado. Resultados: Se reclutaron 44 pacientes, incluyendo 8 casos bilaterales (52 megauréteres). El tiempo promedio de seguimiento fue de 23,2 +/- 20,1 meses. La edad mediana de diagnóstico fue de 7,5 meses (rango 1-155 meses), con un 77 por ciento de pacientes masculinos. Un 32 por ciento de los pacientes recibieron tratamiento quirúrgico. No hubo asociación entre la conducta y el género o la forma de presentación. Los pacientes con megauréter izquierdo tuvieron mayor tendencia a ser manejados quirúrgicamente (0,01< p< 0,05), mientras que los bilaterales resolvieron todos médicamente (0,05< p< 0,1). La presencia de ITU durante el seguimiento fue un fenómeno infrecuente (9 por ciento), teniendo una asociación intermedia con la necesidad de tratamiento quirúrgico (0,01< p< 0,05). Una Función Renal Relativa Cintigráfica (FRR) inicial menor a 40 por ciento presentó un VPP=0,67 y un VPN=0,81 para predecir cirugía, con una probabilidad de asociación intermedia (0,01 < p < 0,05). Una Curva de Excreción Cintigráfica Obstructiva (CECO) inicial presentó un VVP=0,82 y un VPN=0,89 para predecircirugía, con una alta probabilidad de asociación (p < 0,01). Una Dilatación Pieloureteral Ecográfica Severa (DPUES) inicial presentó un VVP=0,67 y un VPN=0,89 para predecir cirugía, con una alta probabilidad de asociación (p < 0,01). Al presentarse estas condiciones en conjunto, se obtuvo una mejora importante de los VPP para predecir cirugía, con altas probabilidades de asociación...

Introduction: Primary non refluxing megaureter (PNM) has a high index of spontaneous resolution. The present study evaluates different clinical and imaging factors that may predict the need for surgical management. Material and methods: A retrospective analysis of PNM patients diagnosed between 1995 and 2005was performed. Data was described and analyzed with chi-square test. Results: A total of 44 patients, 8 bilateral cases (52 megaureters total), were analyzed. Mean follow up time was 23,2 +/- 20,1 months. Mean age was 7,5 months (range 1-155 months) with 77 percent of patients being male. A total of 32 percent patients underwent surgical treatment. There was no relation between medical conduct and form of presentation. Left megaureters were mostly treated surgically(0,01< p < 0,05) while bilateral ones were managed expectantly (0,05 < p < 0,1). Urinary infection during follow-up was infrequent (only 9 percent) having an intermediate association with surgical treatment (0,01< p < 0,05). Relative Renal Cintigram Function (RRCF) under 40 percent presented a PPV=0,67 and NPV=0,81 for surgery with and intermediate association probability (0,01< p< 0,05).Obstructive Renal Cintigram Curve (ORCC) presented a PPV=0,82 and a NPV=0,89 for surgery with a high association probability (p < 0,01). Initial Severe Pelvic Hydronefrosis (ISPH) presented PPV=0,67and NPV=0,89 for surgery with a high association probability (p < 0,01). All these conditions put together presented an increased in the PPV for predicting surgery with high association probabilities. Conclusions: Surgical management of PNM is infrequent. Gender and form of presentation were not significantly associated with management. Side and the presence of UTI during follow-up could be used to prognosticate the need for surgery. Prognostic value of RRCF, ORCC and ISPH is defined by their NPV. Renal ultrasound and cintigram are useful in predicting future therapeutic conduct.

Nonresonant inelastic x-ray scattering and energy-resolved Wannier function investigation of d-d excitations in NiO and CoO.

Nonresonant inelastic x-ray scattering measurements on NiO and CoO show that strong dipole-forbidden d-d excitations appear within the Mott gap at large wave vectors. These dominant excitations are highly anisotropic, and have [001] nodal directions for NiO. Theoretical analyses based on a novel, energy-resolved Wannier function (within the local density approximation+Hubbard U) show that the anisotropy reflects the local exciton wave functions and local point-group symmetry. The sensitivity to weak symmetry breaking in particle-hole wave functions suggests a wide application to strongly correlated systems.

Actualización en otitis media con efusión: revisión bibliográfica / Update on otitis media with effusion: bibliographic review

La Otitis Media con Efusión (OME) es una patología muy frecuente en la población pediátrica, siendo la mayor causa de hipoacusia de conducción en este grupo etario. El screening a población sana no ha mostrado beneficios clínicamente relevantes por lo que su aplicación no se recomienda. Dada la alta tasa de resolución espontánea, la mayoría de las OME sólo van a requerir conducta expectante mediante controles periódicos, sin necesidad de medicamentos o cirugía. Existe un grupo minoritario de pacientes que van a requerir cirugía, lo cual va a depender del tiempo de evolución, pertenencia al grupo de alto riesgo, presencia de hipoacusia, presencia de alteraciones de lenguaje o cognitivas, o sospecha de alteraciones estructurales, entre otras. En este grupo de pacientes, la punción timpánica con colocación de tubos de ventilación es la cirugía de primera elección. La adenoidectomía debe ser realizada en pacientes con OME a los que ya se les había sometido a colocación de tubos de ventilación timpánica.

Determination of the mechanism for resonant scattering in LaMnO3.

The resonant multiple Bragg x-ray diffraction is used to study the forbidden (104) reflection in LaMnO3. Using the interference between the three-beam scattering and resonant scattering we can determine the phase of the resonant scattering. This phase is shown to be consistent with a model in which the resonant scattering is caused by the influence of the Mn-O bond length distortion rather than directly by the orbital ordering on the Mn 4p band structure.

Disección espontánea de arteria vertebral en la consulta otorrinolaringológica: reporte de caso / Spontaneous dissection of the vertebral artery in otorhinolaryngologic consultation: case report

La disección espontánea de arteria vertebral es una causa frecuente de accidente vascular encefálico en población joven. A continuación informamos el caso de un paciente masculino de 42 años, quien se presenta en la consulta otorrinolaringológica con un cuadro de instalación aguda de cefalea asociada a déficit de pares craneanos e inestabilidad de la marcha, el cual fue interpretado en un servicio de urgencia como un síndrome vertiginoso periférico, luego de una tomografía computada de cerebro sin contraste normal. Se procede a solicitar angiorresonancia, diagnosticándose disección espontánea de arteria vertebral derecha, motivo por el cual es hospitalizado y manejado con anticoagulación sistémica con buena evolución.

Enfrentamiento a un turmor de peñazco: estudio y posibilidad diagnóstica / Facing a petrous tumor: study and diagnostic possibility

Los tumores de punta de peñasco se pueden presentar con hipoacusia sensorioneural y un síndrome vertiginoso secundario a hidrops endolinfático. Dentro del diagnóstico diferencial se encuentran los tumores de saco endolinfático, los cuales han sido reportados cada vez con mayor frecuencia en la literatura. A continuación informamos el caso de un paciente de 50 años que se presenta a la consulta con hipoacusia sensorioneural fluctuante de oído derecho y síndrome vertiginoso. Las neuraimágenes muestran tumor de punta de peñasco que ha tenido un crecimiento progresivo en el tiempo erosionando secundariamente estructuras del oído interno. Se realizó biopsia que no fue concluyente, la cual no ha podido ser repetida por decisión personal de la paciente, por lo que se ha mantenido en manejo expectante. Dada la evolución y las imágenes se plantea diagnóstico de tumor de saco endolinfático, a la espera de una biopsia confirmatoria.

Imaging density disturbances in water with a 41.3-attosecond time resolution.

We show that the momentum flexibility of inelastic x-ray scattering may be exploited to invert its loss function, allowing real time imaging of density disturbances in a medium. We show the disturbance arising from a point source in liquid water, with a resolution of 41.3 attoseconds (4.13 x 10(-17) s) and 1.27 A (1.27 x 10(-8) cm). This result is used to determine the structure of the electron cloud around a photoexcited chromophore in solution, as well as the wake generated in water by a 9 MeV gold ion. We draw an analogy with pump-probe techniques and suggest that energy-loss scattering may be applied more generally to the study of attosecond phenomena.

Spatial distribution of competing ions around DNA in solution.

The competition of monovalent and divalent cations for proximity to negatively charged DNA is of biological importance and can provide strong constraints for theoretical treatments of polyelectrolytes. Resonant x-ray scattering experiments have allowed us to monitor the number and distribution of each cation in a mixed ion cloud around DNA. These measurements provide experimental evidence to support a general theoretical prediction: the normalized distribution of each ion around polyelectrolytes remains constant when ions are mixed at different ratios. In addition, the amplitudes of the scattering signals throughout the competition provide a measurement of the surface concentration parameter that predicts the competition behavior of these cations. The data suggest that ion size needs to be taken into account in applying Poisson-Boltzmann treatments to polyelectrolytes such as DNA.

Energy-recovery linac project at Cornell University.

There is considerable interest in using superconducting electron linacs with energy recovery as synchrotron radiation sources. Such energy recovery linacs (ERLs) would open new regimes of X-ray science because they are capable of producing ultra-brilliant X-ray beams [>5 x 10(22) photons s(-1) (0.1% bandwidth)(-1) mm(-2) mrad(-2) at 10 keV], maintaining a very small source size ( approximately 3 micro m r.m.s.) suitable for micro X-ray beams, and making very intense fast ( approximately 100 fs) X-ray pulses. Each of these characteristics would permit the execution of experiments that are not feasible with existing synchrotron sources. Many technical issues must be satisfactorily resolved before the potential of a full-scale ERL can be realised, including the generation of high average current (10 to 100 mA), high-brightness electron beams (0.015 to 0.15 nm rad emittances, respectively); acceleration of these beams to energies of 5-7 GeV without unacceptable emittance degradation; stable and efficient operation of superconducting linear accelerators at very high gradients etc. Cornell University, in collaboration with Jefferson Laboratory, has proposed to resolve these issues by the construction of a 100 MeV, 100 mA prototype ERL. The intention is to then utilize the information that is learned from the prototype to propose the construction of a full-scale ERL light source.

Counterion distribution around DNA probed by solution X-ray scattering.

Counterion atmospheres condensed onto charged biopolymers strongly affect their physical properties and biological functions, but have been difficult to quantify experimentally. Here, monovalent and divalent counterion atmospheres around DNA double helices in solution are probed using small-angle x-ray scattering techniques. Modulation of the ion scattering factors by anomalous (resonant) x-ray scattering and by interchanging ion identities yields direct measurements of the scattering signal due to the spatial correlation of surrounding ions to the DNA. The quality of the data permit, for the first time, quantitative tests of extended counterion distributions calculated from atomic-scale models of biologically relevant molecules.

Flash-cooling and annealing of protein crystals.

Flash-cooling and annealing of macromolecular crystals have been investigated using in situ X-ray imaging, diffraction-peak lineshape measurements and conventional crystallographic diffraction. The dominant mechanisms by which flash-cooling creates disorder are suggested and a fixed-temperature annealing protocol for reducing this disorder is demonstrated that should be more reliable and flexible than existing protocols. Flash-cooling tetragonal lysozyme crystals degrades diffraction resolution and broadens the distributions of lattice orientations (mosaicity) and lattice spacings. The diffraction resolution strongly correlates with the width of the lattice-spacing distribution. Annealing at fixed temperatures of 253 and 233 K consistently reduces the lattice-spacing spread and improves the resolution for annealing times up to approximately 30s. X-ray images show that this improvement arises from the formation of well ordered domains with characteristic sizes >10 microm and narrower mosaicities than the crystal as a whole. Flash-cooled triclinic crystals of lysozyme, which have a smaller water content than the tetragonal form, diffract to higher resolution with smaller mosaicities and exhibit pronounced ordered domain structure even before annealing. It is suggested that differential thermal expansion of the protein lattice and solvent may be the primary cause of flash-cooling-induced disorder. Mechanisms by which annealing at T << 273 K reduce this disorder are discussed.

Dynamic response of tetragonal lysozyme crystals to changes in relative humidity: implications for post-growth crystal treatments.

The dynamic response of tetragonal lysozyme crystals to dehydration has been characterized in situ using a combination of X-ray topography, high-resolution diffraction line-shape measurements and conventional crystallographic diffraction. For dehydration from 98% relative humidity (r.h.) to above 89%, mosaicity and diffraction resolution show little change and X-ray topographs remain featureless. Lattice constants decrease rapidly but the lattice-constant distribution within the crystal remains very narrow, indicating that water concentration gradients remain very small. Near 88% r.h., the c-axis lattice parameter decreases abruptly, the steady-state mosaicity and diffraction resolution degrade sharply and topographs develop extensive contrast. This transformation exhibits metastability and hysteresis. At fixed r.h. < 88% it is irreversible, but the original order can be almost completely restored by rehydration. These results suggest that this transformation is a first-order structural transition involving an abrupt loss of crystal water. The front between transformed and untransformed regions may propagate inward from the crystal surface and the resulting stresses along the front may degrade mosaicity. Differences in crystal size, shape and initial perfection may produce the observed variations in degradation timescale. Consequently, the success of more general post-growth treatments may often involve identifying procedures that either avoid lattice transitions, minimize disorder created during such transitions or maintain the lattice in an ordered metastable state.