Phase stability and dense polymorph of the BaCa(CO3)2 barytocalcite carbonate.

The double carbonate BaCa(CO3)2 holds potential as host compound for carbon in the Earth's crust and mantle. Here, we report the crystal structure determination of a high-pressure BaCa(CO3)2 phase characterized by single-crystal X-ray diffraction. This phase, named post-barytocalcite, was obtained at 5.7 GPa and can be described by a monoclinic Pm space group. The barytocalcite to post-baritocalcite phase transition involves a significant discontinuous 1.4% decrease of the unit-cell volume, and the increase of the coordination number of 1/4 and 1/2 of the Ba and Ca atoms, respectively. High-pressure powder X-ray diffraction measurements at room- and high-temperatures using synchrotron radiation and DFT calculations yield the thermal expansion of barytocalcite and, together with single-crystal data, the compressibility and anisotropy of both the low- and high-pressure phases. The calculated enthalpy differences between different BaCa(CO3)2 polymorphs confirm that barytocalcite is the thermodynamically stable phase at ambient conditions and that it undergoes the phase transition to the experimentally observed post-barytocalcite phase. The double carbonate is significantly less stable than a mixture of the CaCO3 and BaCO3 end-members above 10 GPa. The experimental observation of the high-pressure phase up to 15 GPa and 300 ºC suggests that the decomposition into its single carbonate components is kinetically hindered.

Gold(i) sulfide: unusual bonding and an unexpected computational challenge in a simple solid.

We report the experimental high-pressure crystal structure and equation of state of gold(i) sulfide (Au2S) determined using diamond-anvil cell synchrotron X-ray diffraction. Our data shows that Au2S has a simple cubic structure with six atoms in the unit cell (four Au in linear, and two S in tetrahedral, coordination), no internal degrees of freedom, and relatively low bulk modulus. Despite its structural simplicity, Au2S displays very unusual chemical bonding. The very similar and relatively high electronegativities of Au and S rule out any significant metallic or ionic character. Using a simple valence bond (Lewis) model, we argue that the Au2S crystal possesses two different types of covalent bonds: dative and shared. These bonds are distributed in such a way that each Au atom engages in one bond of each kind. The multiple arrangements in space of dative and shared bonds are degenerate, and the multiplicity of configurations imparts the system with multireference character, which is highly unusual for an extended solid. The other striking feature of this system is that common computational (DFT) methods fail quite spectacularly to describe it, with 20% and 400% errors in the equilibrium volume and bulk modulus, respectively. We explain this by the poor treatment of static correlation in common density-functional approximations. The fact that the solid is structurally very simple, yet presents unique chemical bonding and is unmodelable using current DFT methods, makes it an interesting case study and a computational challenge.

High-pressure/high-temperature phase diagram of zinc.

The phase diagram of zinc (Zn) has been explored up to 140 GPa and 6000 K, by combining optical observations, x-ray diffraction, and ab initio calculations. In the pressure range covered by this study, Zn is found to retain a hexagonal close-packed (hcp) crystal symmetry up to the melting temperature. The known decrease of the axial ratio (c/a) of the hcp phase of Zn under compression is observed in x-ray diffraction experiments from 300 K up to the melting temperature. The pressure at which c/a reaches [Formula: see text] (≈10 GPa) is slightly affected by temperature. When this axial ratio is reached, we observed that single crystals of Zn, formed at high temperature, break into multiple poly-crystals. In addition, a noticeable change in the pressure dependence of c/a takes place at the same pressure. Both phenomena could be caused by an isomorphic second-order phase transition induced by pressure in Zn. The reported melt curve extends previous results from 24 to 135 GPa. The pressure dependence obtained for the melting temperature is accurately described up to 135 GPa by using a Simon-Glatzel equation: [Formula: see text], where P is the pressure in GPa. The determined melt curve agrees with previous low-pressure studies and with shock-wave experiments, with a melting temperature of 5060(30) K at 135 GPa. Finally, a thermal equation of state is reported, which at room-temperature agrees with the literature.

High-pressure structural and vibrational properties of monazite-type BiPO4, LaPO4, CePO4, and PrPO4.

Monazite-type BiPO4, LaPO4, CePO4, and PrPO4 have been studied under high pressure by ab initio simulations and Raman spectroscopy measurements in the pressure range of stability of the monazite structure. A good agreement between experimental and theoretical Raman-active mode frequencies and pressure coefficients has been found which has allowed us to discuss the nature of the Raman-active modes. Besides, calculations have provided us with information on how the crystal structure is modified by pressure. This information has allowed us to determine the equation of state and the isothermal compressibility tensor of the four studied compounds. In addition, the information obtained on the polyhedral compressibility has been used to explain the anisotropic axial compressibility and the bulk compressibility of monazite phosphates. Finally, we have carried out a systematic discussion on the high-pressure behavior of the four studied phosphates in comparison to results of previous studies.

The plastic crystalline A15 phase of dimethylaminoalane, [N(CH3)2-AlH2]3.

A plastic crystalline phase of dimethylaminoalane has been discovered at T > 332 K. The phase transitions solid - plastic phase - liquid are fully reversible. The plastic crystalline phase exhibits a cubic unit cell, space group Pm3[combining macron]n, in which the dimethylaminoalane molecules rotate and adopt a structural arrangement reminiscent of the A15 phase.

Pressure-induced amorphization of YVO4:Eu³âº nanoboxes.

A structural transformation from the zircon-type structure to an amorphous phase has been found in YVO4:Eu(3+) nanoboxes at high pressures above 12.7 GPa by means of x-ray diffraction measurements. However, the pair distribution function of the high-pressure phase shows that the local structure of the amorphous phase is similar to the scheelite-type YVO4. These results are confirmed both by Raman spectroscopy and Eu(3+) photoluminescence which detect the phase transition to a scheelite-type structure at 10.1 and 9.1 GPa, respectively. The irreversibility of the phase transition is observed with the three techniques after a maximum pressure in the upstroke of around 20 GPa. The existence of two (5)D0-->(7)F0 photoluminescence peaks confirms the existence of two local environments for Eu(3+), at least for the low-pressure phase. One environment is the expected for substituting Y(3+) and the other is likely a disordered environment possibly found at the surface of the nanoboxes.

Needle track recurrence after transrectal prostate biopsy detected by 18F-Choline PET–CT / Siembra tumoral secundaria a una biopsia transrectal de próstata detectada por 18F-Colina PET-TC

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Design and validation of an augmented reality system for laparoscopic surgery in a real environment.

PURPOSE: This work presents the protocol carried out in the development and validation of an augmented reality system which was installed in an operating theatre to help surgeons with trocar placement during laparoscopic surgery. The purpose of this validation is to demonstrate the improvements that this system can provide to the field of medicine, particularly surgery. METHOD: Two experiments that were noninvasive for both the patient and the surgeon were designed. In one of these experiments the augmented reality system was used, the other one was the control experiment, and the system was not used. The type of operation selected for all cases was a cholecystectomy due to the low degree of complexity and complications before, during, and after the surgery. The technique used in the placement of trocars was the French technique, but the results can be extrapolated to any other technique and operation. RESULTS AND CONCLUSION: Four clinicians and ninety-six measurements obtained of twenty-four patients (randomly assigned in each experiment) were involved in these experiments. The final results show an improvement in accuracy and variability of 33% and 63%, respectively, in comparison to traditional methods, demonstrating that the use of an augmented reality system offers advantages for trocar placement in laparoscopic surgery.

Anomalous high-pressure Jahn-Teller behavior in CuWO4.

High-pressure optical-absorption measurements performed in CuWO(4) up to 20 GPa provide experimental evidence of the persistence of the Jahn-Teller (JT) distortion in the whole pressure range both in the low-pressure triclinic and in the high-pressure monoclinic phase. The electron-lattice couplings associated with the e(g)(E⊗e) and t(2g)(T⊗e) orbitals of Cu(2+) in CuWO(4) are obtained from correlations between the JT distortion of the CuO(6) octahedron and the associated structure of Cu(2+) d-electronic levels. This distortion and its associated JT energy (E(JT)) decrease upon compression in both phases. However, both the distortion and associated E(JT) increase sharply at the phase-transition pressure (P(PT)=9.9 GPa), and we estimate that the JT distortion persists for a wide pressure range not being suppressed up to 37 GPa. These results shed light on the transition mechanism of multiferroic CuWO(4), suggesting that the pressure-induced structural phase transition is a way to minimize the distortive effects associated with the toughness of the JT distortion.

Concordancia interobservador en el análisis visual y semicuantitativo de las imágenes SPECT 123I-FP-CIT en el diagnóstico del síndrome parkinsoniano / Interobserver agreement in the visual and semi-quantitative analysis of the 123I-FP-CIT SPECT images in the diagnosis of Parkinsonian syndrome

Objetivos. El SPECT 123I-FP-CIT permiten identificar el deterioro presináptico de la vía dopaminérgica mediante el estudio de los transportadores de la dopamina (DAT). Un análisis correcto de las imágenes SPECT contribuye una adecuada interpretación y diagnóstico de los trastornos del movimiento. Objetivos: 1. Comparar el análisis visual y semicuantitativo del SPECT 123I-FP-CIT. 2. Evaluar el acuerdo interobservador en ambos análisis. 3. Buscar un punto de corte del análisis semicuantitativo que permita discriminar SP primarios de no SP primarios. Métodos. Se realizó un 123I-FP-CIT SPECT a 32 pacientes con sospecha clínica de SP primario de no SP primario. El análisis visual y semicuantitativo fueron realizados de forma independiente por dos médicos nucleares. El análisis visual se basó en la interpretación visual de las imágenes. El análisis semicuantitativo se determinó como la relación entre la actividad específica y la no específica. Se calcularon S, E, VPP y VPN. La comparación de los datos se realizó usando el test ANOVA seguido de la corrección de Bonferroni. El coeficiente de correlación intraclase y la Kappa estadística midieron el grado de acuerdo interobservador de ambos análisis respectivamente. Se generó una curva ROC del análisis semicuantitativo. Resultados. El análisis visual mostró una S de 86% y una E de 100-88% en el diagnóstico diferencial del SP primario del no SP primario. El análisis semicuantitativo mostró una hipocaptación gradual proporcional al grado de severidad objetivado en el análisis visual. El análisis semicuantitativo no mostró ninguna información adicional al visual. El coeficiente de correlación intraclase y la Kappa estadística mostraron unos valores de 0,92 y 0,80 respectivamente. El dintel para diferenciar SP primarios de no SP primarios fue de 1,9 como índice putaminal(AU)

Aims. Using 123I-FP-CIT SPECT images makes it possible to identify presynaptic deterioration of the dopaminergic pathway by studying the dopamine transporter (DAT). A correct analysis of the SPECT images contributes to an adequate interpretation and diagnosis of movement disorders. Aims: 1. To compare visual and semiquantitative analysis of 123I-FP-CIT SPECT images in patients with movement disorders. 2. To evaluate interobserver agreement in visual and semiquantitative analysis. 3. To obtain a cut-off in the semiquantitative analysis to discriminate primary Parkinsonism Syndrome (PS) from non-primary PS. Methods. A 123I-FP-CIT SPECT was performed in 32 patients with movement disorders suggestive of primary PS. Visual and semiquantitative images analyses were performed independently by two nuclear medicine physicians. Visual analysis was based on the visual interpretation. Semiquantitative analysis was calculated as specific uptake (caudate, putamen and striatum) versus non-specific uptake (occipital). Sensitivity, specificity, PPV, and NPV were calculated. Data were compared using ANOVA test followed by Bonferroni post-hoc test. Interobserver agreement of the visual and semiquantitative analysis was assessed by intraclass correlation coefficient and Kappa statistics, respectively. ROC curve was generated with semiquantitative data. Results. Visual analysis showed 86% sensitivity and 100-88% specificity for the differential diagnosis of primary PS from non-primary PS. Semiquantitative analysis showed a gradual hypouptake proportional to the disease severity obtained in the visual analysis. Semiquantitative analysis did not provide any additional information to the visual analysis. Intraclass correlation coefficient and Kappa statistics showed 0.92 and 0.80 values, respectively. The Cut-off value to differentiate primary PS from non-primary PS was 1.9 on the putamen index(AU)

[Interobserver agreement in the visual and semi-quantitative analysis of the 123I-FP-CIT SPECT images in the diagnosis of Parkinsonian syndrome]. / Concordancia interobservador en el análisis visual y semicuantitativo de las imágenes SPECT (123)I-FP-CIT en el diagnóstico del síndrome parkinsoniano.

AIMS: Using (123)I-FP-CIT SPECT images makes it possible to identify presynaptic deterioration of the dopaminergic pathway by studying the dopamine transporter (DAT). A correct analysis of the SPECT images contributes to an adequate interpretation and diagnosis of movement disorders. Aims: 1. To compare visual and semiquantitative analysis of (123)I-FP-CIT SPECT images in patients with movement disorders. 2. To evaluate interobserver agreement in visual and semiquantitative analysis. 3. To obtain a cut-off in the semiquantitative analysis to discriminate primary Parkinsonism Syndrome (PS) from non-primary PS. METHODS: A (123)I-FP-CIT SPECT was performed in 32 patients with movement disorders suggestive of primary PS. Visual and semiquantitative images analyses were performed independently by two nuclear medicine physicians. Visual analysis was based on the visual interpretation. Semiquantitative analysis was calculated as specific uptake (caudate, putamen and striatum) versus non-specific uptake (occipital). Sensitivity, specificity, PPV, and NPV were calculated. Data were compared using ANOVA test followed by Bonferroni post-hoc test. Interobserver agreement of the visual and semiquantitative analysis was assessed by intraclass correlation coefficient and Kappa statistics, respectively. ROC curve was generated with semiquantitative data. RESULTS: Visual analysis showed 86% sensitivity and 100-88% specificity for the differential diagnosis of primary PS from non-primary PS. Semiquantitative analysis showed a gradual hypo-uptake proportional to the disease severity obtained in the visual analysis. Semiquantitative analysis did not provide any additional information to the visual analysis. Intraclass correlation coefficient and Kappa statistics showed 0.92 and 0.80 values, respectively. The Cut-off value to differentiate primary PS from non-primary PS was 1.9 on the putamen index.

Randomised study of single dose (8 Gy vs. 6 Gy) of analgesic radiotherapy plus zoledronic acid in patients with bone metastases.

OBJECTIVE: To assess the effectiveness of a single dose of radio therapy (8 Gy vs. 6 Gy) plus zoledronic acid in cancer patients with bone metastases in treating pain; quality of life, time to onset of skeletal events and functional status. MATERIAL AND METHODS: A total of 139 patients from 22 Spanish hospitals were randomly assigned to: Group A, administered a single dose of 8 Gy+zoledronic acid (4 mg iv, in 15-min infusions), and Group B, administered a single dose of 6 Gy+zoledronic acid (4 mg iv, in 15-min infusions). The main variable was pain, which was assessed with the Visual Analogue Pain Scale (VAS) in supine, seated and standing positions. RESULTS: There was a total of 118 patients for intention to treat (n=67 in Group A and n=51 in Group B). The most frequent primary neoplasms were the lung (29.66%), prostate (22.03%) and breast (21.19%). Sixty patients were analysed per protocol, n=34 in group A and n=26 in group B. Improvements were observed in the VAS scores for pain in all three positions. The mean time to onset of the event was greater (p=0.0211) in Group A than in Group B (122 vs. 81.62 days). Functional status improved in Group A, and quality of life improved in both groups. CONCLUSION: The two groups achieved similar levels of pain control in supine, seated and standing positions. Quality of life also improved in both groups. However, the higher dose (8 Gy dose) in combination with zoledronic acid is associated with a longer period without skeletal events.

Randomised study of single dose (8 Gy vs. 6 Gy) of analgesic radiotherapy plus zoledronic acid in patients with bone metastases

OBJECTIVE: To assess the effectiveness of a single dose of radio therapy (8 Gy vs. 6 Gy) plus zoledronic acid in cancer patients with bone metastases in treating pain; quality of life, time to onset of skeletal events and functional status. MATERIAL AND METHODS: A total of 139 patients from 22 Spanish hospitals were randomly assigned to: Group A, administered a single dose of 8 Gy+zoledronic acid (4 mg iv, in 15-min infusions), and Group B, administered a single dose of 6 Gy+zoledronic acid (4 mg iv, in 15-min infusions). The main variable was pain, which was assessed with the Visual Analogue Pain Scale (VAS) in supine, seated and standing positions. RESULTS: There was a total of 118 patients for intention to treat (n=67 in Group A and n=51 in Group B). The most frequent primary neoplasms were the lung (29.66%), prostate (22.03%) and breast (21.19%). Sixty patients were analysed per protocol, n=34 in group A and n=26 in group B. Improvements were observed in the VAS scores for pain in all three positions. The mean time to onset of the event was greater (p=0.0211) in Group A than in Group B (122 vs. 81.62 days). Functional status improved in Group A, and quality of life improved in both groups. CONCLUSION: The two groups achieved similar levels of pain control in supine, seated and standing positions. Quality of life also improved in both groups. However, the higher dose (8 Gy dose) in combination with zoledronic acid is associated with a longer period without skeletal events (AU)

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Fisiopatología de la degeneración y del dolor de la columna lumbar / Physiopathology of lumbar spine degeneration and pain

La lumbalgia es una patología muy frecuente en nuestro medio, con una enorme repercusión sanitaria y sociolaboral. Con la edad, se inicia una cascada degenerativa en la columna lumbar, que comienza en el disco intervertebral, continuando por las facetas articulares y demás elementos vertebrales. Esta degeneración del raquis forma parte del envejecimiento normal del individuo, aunque en ocasiones puede causar dolor y/o alteraciones neurológicas. Para comprender la fisiopatología del dolor lumbar, será preciso conocer que la inervación de la columna lumbar se hace fundamentalmente por tres ramos nerviosos: ramo dorsal de los nervios espinales lumbares (o rami dorsal), nervio sinuvertebral de Luschka y ramos ventrales de la cadena simpática. Existen dos tipos de patrones de dolor en la columna lumbar: el dolor irradiado y el dolor referido. La cascada de la degeneración consta en tres estadios. El primer estadio sería la disfunción. El anillo fibroso se fisura y pierde la capacidad de contener al núcleo pulposo. Esto ocasiona primero el síndrome de disrupción discal y, si el núcleo supera el contorno del annulus, las hernias discales. El segundo estadio de Kirkaldy-Willis es el de inestabilidad. En este estadio la movilidad en el segmento móvil aumenta de forma patológica. En esta revisión describiremos los signos radiológicos asociados a esta inestabilidad. La tercera fase es la de estabilización, caracterizada por la estenosis, asociada o no a inestabilidad

Low back pain is a very frequent condition in our country and has great social and occupational repercussions. With advancing age, a degenerative cascade occurs in the lumbar spine, which starts at the intervertebral disc and subsequently involves the facet joints and other vertebral elements. This spinal degeneration is part of the normal ageing process, although it can sometimes cause pain and/or neurological alterations. To understand the physiopathology of lumbar pain, it is necessary to know that the innervation of the lumbar spine occurs mainly through three nerve rami: dorsal ramus of the lumbar spine nerves (or «dorsal rami»), Luschka's sinuvertebral nerve and the ventral rami of the sympathetic chain. There are two types of pain pattern in the lumbar spine: irradiated pain and referred pain. The degeneration cascade is divided up into three stages. The first is that of dysfunction, whereby the annulus fibrosus is fissured and can no longer contain the nucleus pulposus. This leads, first to the so-called disc disruption syndrome and, if the nucleus exceeds the contour of the annulus, to disc herniations. The second stage, also called the Kirkaldy-Willis stage, is that of instability. At this stage, the mobility of the mobile segment increases pathologically. We describe the radiological signs associated to this instability. The third phase is that of stabilization and is characterized by stenosis, which may or may not be associated to instability