Quantifying local and cooperative components in the ferroelectric distortion of BaTiO(3): learning from the off-center motion in the MnCl(6)(5-) complex formed in KCl:Mn(+).

The delicate balance between cooperative and local contributions in the ferroelectric distortions of BaTiO3 is explored by means of ab initio calculations. As a salient feature, it is found that a single Ti(4+) ion in BaTiO3 is not allowed to move off-center at ambient pressure, while this is no longer true if the lattice is expanded by only ∼5%, stressing the high sensitivity of the local contribution to chemical and hydrostatic pressures. In order to further understand the effect of local contributions on the phase transition mechanism of ferroelectrics, we have investigated the surprising C3v → C4v → Oh local transformations occurring in the 10-50 K temperature range for the MnCl6(5-) complex formed in KCl:Mn(+) that mimic the behavior of BaTiO3. From Boltzmann analysis of the vibronic levels derived from ab initio calculations and considering decoherence introduced by random strains, the present calculations reproduce the experimental phase sequence and transition temperatures. Furthermore, our calculations show that the off-center instability in KCl:Mn(+) would be suppressed by reducing by only 1% the lattice parameter, a situation that then becomes comparable to that found for BaTiO3 at ambient pressure. The present results thus stress the deep link between the structural phase transitions of ferroelectric materials and local phase transitions displayed by transition-metal impurities in insulators.

Cr3+-doped fluorides and oxides: role of internal fields and limitations of the Tanabe-Sugano approach.

This work is aimed at clarifying the changes on optical spectra of Cr(3+) impurities due to either a host lattice variation or a hydrostatic pressure, which can hardly be understood by means of the usual Tanabe-Sugano (TS) approach assuming that the Racah parameter, B, grows when covalency decreases. For achieving this goal, the optical properties of Cr(3+)-doped LiBaF(3) and KMgF(3) model systems have been explored by means of high level ab initio calculations on CrF(6)(3-) units subject to the electric field, E(R)(r), created by the rest of the lattice ions. These calculations, which reproduce available experimental data, indicate that the energy, E((2)E), of the (2)E(t(2g)(3)) → (4)A(2)(t(2g)(3)) emission transition is nearly independent of the host lattice. By contrast, the energy difference corresponding to (4)A(2)(t(2g)(3)) → (4)T(1)(t(2g)(2)e(g)(1)) and (4)A(2)(t(2g)(3)) → (4)T(2)(t(2g)(2)e(g)(1)) excitations, Δ((4)T(1); (4)T(2)), is shown to increase on passing from the normal to the inverted perovskite host lattice despite the increase in covalency, a fact which cannot be accounted for through the usual TS model. Similarly, when the Cr(3+)-F(-) distance, R, is reduced both Δ((4)T(1); (4)T(2)) and the covalency are found to increase. By analyzing the limitations of the usual model, we found surprising results that are shown to arise from the deformation of both 3d(Cr) and ligand orbitals in the antibonding e(g) orbital, which has a σ character and is more extended than the π t(2g) orbital. By contrast, because of the higher stiffness of the t(2g) orbital, the dependence of E((2)E) with R basically follows the corresponding variation of covalency in that level. Bearing in mind the similarities of the optical properties displayed by Cr(3+) impurities in oxides and fluorides, the present results can be useful for understanding experimental data on Cr(3+)-based gemstones where the local symmetry is lower than cubic.

Spectrochemical series and the dependence of Racah and 10 Dq parameters on the metal-ligand distance: microscopic origin.

The origin of the spectrochemical series and the different dependence of crystal-field splitting (10Dq) and Racah parameters on the metal-ligand distance, R, is explored through ab initio calculations on Cr(3+)-doped K2NaScF6, Cs2NaYCl6, Cs2NaYBr6, and Cs2NaYI6 lattices. For this purpose both periodic and cluster calculations have been performed. An analysis of ab initio results proves that 10Dq values mostly come from the small admixture of deep nLs ligand orbitals present in the antibonding eg(∼ x(2)-y(2),3z(2)-r(2)) level and not from the dominant covalency with valence nLp ligand orbitals, which is actually responsible for the reduction of Racah parameters. This study thus reveals the microscopic origin of the stronger dependence upon R of 10Dq when compared to that observed for Racah parameters, thus explaining why electronic transitions which are 10Dq-independent give rise to sharp optical bands. As a salient feature, while the covalency with nLp levels increases significantly on passing from CrF6(3-) to CrI6(3-), the nLs admixture in eg is found to be practically unmodified. This fact helps to understand the progressive decrease of 10Dq through the series of CrF6(3-), CrCl6(3-), CrBr6(3-), and CrI6(3-) complexes embedded in the corresponding host lattices when compared at the corresponding equilibrium distance at zero pressure. The growing importance of the nLs admixture is well-depicted using deformation density diagrams on passing from the ground state (4)A2(t2g(3)) to the (4)T2(t2g(2)eg) excited state depicted at several R values.

Tunneling splitting of Jahn-Teller ions in oxides.

The magnitude of tunneling splitting, 3Gamma, that governs decoherence in quantum systems under symmetric potentials, is frequently unknown. Using first-principles calculations, we have obtained 3Gamma for a number of E[symbol:see text]e Jahn-Teller impurities in solids. Calculated values span 6 orders of magnitude on passing from KCl:Ag{2+} to MgO:Cu{2+}. Values associated with Cu2+- and Ag2+-doped MgO are 2 orders of magnitude larger than those previously assumed and consistent with the existence of a dynamic Jahn-Teller effect. The origin and enhancement with pressure of these high 3Gamma values is discussed in detail.

Manifestaciones oftalmológicas del síndrome de Carney / Ocular findings in Carney complex

Caso clínico: El Complejo de Carney (CNC) es un raro síndrome multineoplásico, autosómico dominante; caracterizado por presentar mixomas, lesiones pigmentadas en la piel, tumores endocrinos y manifestaciones oculares. Discusión: Analizamos los signos oftalmológicos de este síndrome, los cuales suelen preceder al componente más serio del mismo, el mixoma cardíaco

Case report: Carney complex (CNC) is a multiple neoplasia syndrome, inherited in an autosomal dominant manner, characterized by myxomas, spotty skin pigmentation, endocrine tumors and ophthalmic abnormalities. Discussion: We report the ocular findings which usually precede the most serious component of the complex, the cardiac myxoma

Plasmocitoma solitario de esternón. Presentación de un caso y revisión de la literatura / Isolated plasmacytoma of the sternum: presentation of a case and review

La localización del plasmocitoma a nivel esternales excepcional. Se presenta el caso de un pacientecon una tumoración en la región del manubrio esternal,sin diagnóstico de certeza a pesar de la PAAF yde la biopsia incisional efectuadas. Se realizó unaresección con amplios márgenes de la lesión, reconstruyendoel defecto con una malla de polipropileno.Los resultados postoperatorios fueron satisfactorios.Se efectúa una revisión de la literatura

The localization of plasmacytoma in the sternumis exceptional. A patient suspected of having a sternalmanubrium tumor, without a clear diagnosisdespite a fine needle aspiration biopsy and an incisionbiopsy is presented. A wide margin resectionof the lesion and reconstruction with a polypropylenemesh were undertaken. The results were satisfactory.A review of the literature is made

[Ocular findings in Carney complex]. / Manifestaciones oftalmológicas del síndrome de Carney.

CASE REPORT: Carney complex (CNC) is a multiple neoplasia syndrome, inherited in an autosomal dominant manner, characterized by myxomas, spotty skin pigmentation, endocrine tumors and ophthalmic abnormalities. DISCUSSION: We report the ocular findings which usually precede the most serious component of the complex, the cardiac myxoma.

[Pneumocephalus and cerebrospinal fluid fistula following removal of a superior sulcus tumor (pancoast tumor)]. / Neumoencéfalo y fístula de líquido cefalorraquídeo tras resección de tumor del sulcus superior (tumor de Pancoast).

Pneumocephalus resulting from a subarachnoid-pleural fistula following resection of a pulmonary neoplasm is a very rare postoperative complication: we have found only 17 cases in the literature. We report the case of a 65-year-old man diagnosed with a superior sulcus tumor who underwent a left upper lobectomy and costal resection following neoadjuvant radiation therapy. Soon after surgery, the patient developed a subarachnoid-pleural fistula and pneumocephalus that required reoperation and drainage. Recurrence was suspected when chronic aseptic meningitis developed. Another thoracotomy was required to resolve the complication.

Neumoencéfalo y fístula de líquido cefalorraquídeo tras resección de tumor del sulcus superior (tumor de Pancoast) / Pneumocephalus and cerebrospinal fluid fistula following removal of a superior sulcus tumor (Pancoast tumor)

El neumoencéfalo, como consecuencia de una fístula subaracnoideo-pleural, es una complicación muy poco frecuente tras la resección de una neoplasia pulmonar (hemos encontrado únicamente 17 casos descritos en la bibliografía). Se presenta el caso de un paciente de 65 años, intervenido con el diagnóstico de tumor del sulcus superior tras recibir radioterapia neoadyuvante, al que se le practicaron lobectomía superior izquierda y resección costal. Como complicación postoperatoria temprana, desarrolló una fístula subaracnoideo-pleural y neumoencéfalo, que requirió reintervención y drenaje. Una meningitis abacteriana cronificada llevó a sospechar su recidiva, y fue necesaria una nueva toracotomía para su resolución definitiva (AU)

Un nódulo pulmonar solitario

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Tumor desmoide de la pared torácica / Desmoid tumor of the chest wall

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[Systemic mastocytosis and secondary acute myeloid leukemia]. / Mastocitosis sistémica y leucemia mieloide aguda secundaria.

Systemic mast cell disease (SMCD) is an idiopathic disorder in which mast cells proliferate and accumulate in various organs including the skin, bone marrow, liver, spleen and lymph nodes. SMCD is regarded as a myeloproliferative disorder for any authors. Associated hematologic disorders can be found in up to one third of patients with SMCD. It may be due to the apparent close relationship between the mast cell and the myeloid cell.

[Solitary fibrous tumors of the pleura]. / Tumores fibrosos solitarios de la pleura.

Seven cases of solitary fibrous tumours of the pleura are here reported, formerly named benign fibrous mesotheliomas. Histologically, these tumours are formed by fusiform cells with a minimal cellular pleomorphism and absence of mitosis. These tumours cause scarce symptoms which are usually diagnosed as a casual finding when a chest X-ray is performed on account of other cause. Treatment should be surgical, with removal of all tumoral mass, thus avoiding its growth and the possibility of the reported degeneration towards malignancy.

Mastocitosis sistémica y leucemia mieloide aguda secundaria / Acute myeloid leukemia secondary a systemic mastocitosis

La mastocitosis sistémica es una enfermedad en la cual los mastocitos proliferan y se acumulan en distintos tejidos como la piel, médula ósea, hígado, bazo y ganglios linfáticos. Algunos autores la consideran como un síndrome mieloproliferativo. Una tercera parte de los pacientes desarrollan otras neoplasias hematológicas, apoyando el origen mieloide del mastocito (AU)

[The effect of a program of care for the diabetic on control of the disease]. / Influencia de un programa de atención al diabético sobre su control.

OBJECTIVE: To study the association between the application of a diabetic care programme and modifications in glycated haemoglobin and the Body Mass Index. DESIGN: Descriptive study. SETTING: Two health centres. PATIENTS: 199 patients were studied, the total number of type II diabetics found in three general medicine practices. INTERVENTION: Patients followed, at different levels, a programme of diabetic care. Variation of glycated haemoglobin and the Body Mass Index were measured in each patient during the 1991-1992 period. These were then related to their continuation in the programme and whether they were included in this programme at the moment of the examination. RESULTS: The average drop in glycated haemoglobin was -15.3% (12.2 +/- 18.4) (p < 0.001). Average variation of the Body Mass Index was 0.2% (-0.6 +/- 1.00), not significant. Average drop in glycated haemoglobin in those included was -16% (12.5 +/- 19.5) (p < 0.001) and in those not included, -12.6% (5.3 +/- 19.9) (p < 0.001), no significant difference. The correlation between the degree of continuation in the programme and the variation of glycated haemoglobin had a r = -0.04 (p = 0.7) and between the degree of continuation and variation in the Body Mass Index, a r of 0.15 (p = 0.06). When the initial value of glycated haemoglobin was equal to or above 7.5, its average drop was -22.3% (17.8 +/- 26.9) (p < 0.001). CONCLUSIONS: The drop in glycated haemoglobin is significant and more important, the greater the initial value. But it has not been possible to link it with the level of continuance in the programme nor with whether patients were included in the programme. The Body Mass Index does not vary.

[Mediastinal fibrosis]. / Fibrosis mediastínica.

Even tough the ultimate etiologic and pathogenic mechanisms of mediastinal fibrosis are not quite established, several causes have been mentioned as the more frequent inducers, such as histoplasmosis, tuberculosis and other granulomatous diseases. Generally the diagnosis is suggested by a hilar or mediastinal mass, which is seen in thorax radiography, because 40% of patients are asymptomatic. Exeresis of fibrotic Magma is difficult because usually there is no separation with trachea neither with superior cava vein. That is why many times we have to restricted ourselves to the surgical approach on the complications. The present work discusses three new cases of mediastinal fibrosis.