Crystal structure and optical and magnetic properties of Pr(2)(MoO(4))(3).

Praseodymium molybdate Pr(2)(MoO(4))(3) was synthesized using the standard ceramic route. The crystal structure of the material has been successfully solved in superspace group I2/b(alphabeta0)00 with lattice constants a = 5.30284(4), b = 5.32699(3), c = 11.7935(1) A, gamma = 90.163(1) degrees , and the modulation vector q = 2/3a* + 0.88810(2)b*. The deviation of the q vector from a rational value allows a description of the structure in terms of nanosize domains with the La(2)(MoO(4))(3)-like structure separated by stacking faults. Under 450 nm excitation, ((3)P(0) level) Pr(2)(MoO(4))(3) exhibits the characteristic red emission, with the most intense band at 649 nm corresponding to a (3)P(0) --> (3)F(2) transition. Magnetic susceptibility measurements reveal Curie-Weiss paramagnetism with predominating antiferromagnetic interactions between Pr(3+)-magnetic moments and no evidence of magnetic transitions down to T = 5 K.

Contactless ultrasonic device to measure surface acoustic wave velocities versus temperature.

A complete optical experimental setup for generating and detecting surface acoustic waves [Rayleigh waves (RWs)] in metals versus temperature up to the melting point is described. The RWs were excited by a pulsed Nd:YAG laser and detected by a high sensitivity subangstrom heterodyne interferometer. A special furnace was used to heat the sample using infrared radiation with a regulation of the sample temperature less than 0.1 K. First measurements on an aluminum alloy sample are presented to validate the setup.

Barrett's esophagus: participation of the esophageal wall.

The modern inhibitors of gastric acid secretion reduce very efficiently the aggressiveness of gastroesophageal reflux but they appear to modify the pathophysiological situation in a way that favours the development of Barrett's esophagus (BE). During the last two decades, the prevalence of BE in the population submitted to endoscopy has clearly increased while the peptic stricture of the esophagus is fast disappearing. With a reduced tendency to stricture and fibrosis, the esophagus seems more prone to the columnar metaplasia. This suggests that the factor that promotes the columnar metaplasia reaches the areas of esophagitis through the esophageal wall. In the conditions of an advanced reflux disease, the veins crossing the gastroesophageal junction would be well suited to the transport of this factor, provided they have not been obliterated by thrombosis or fibrosis. The veins do not normally participate in the metabolic activity but their permeability may be altered in a pathological environment. In the esophageal wall submitted to an important reflux, the environment cannot be normal, as evidenced by the alterations of the esophageal motricity. Furthermore, these veins are submitted to the peristaltic activity of the esophagus.

Five-dimensional structure refinement of natural melilite, (Ca(1.89)Sr(0.01)Na(0.08)K(0.02))(Mg(0.92)Al(0.08)-(Si(1.98)Al(0.02))O(7).

The structure of a crystal of natural melilite from San Venanzo, Umbria (Italy) of the general formula X(2)T1(T2)(2)O(7), where X = Ca(0.945)Sr(0.005)Na(0.04)K(0.01), T1 = Mg(0.92)Al(0.08) and T2 = Si(0.99)Al(0.01), has been solved and refined as an incommensurate structure in five-dimensional superspace. The structure is tetragonal, superspace group P(-)42(1)m:p4mg, cell parameters a = 7.860 (1), c = 5.024 (1) A, modulation vectors q(1) = 0.2815 (3)(a* + b*), q(2) = 0.2815 (3)(-a* + b*). The data collection was performed on a KumaCCD diffractometer. The structure was refined from 7606 reflections to final R = 0.0481. A special modification of the refinement program Jana2000 was necessary to take into account overlapping of satellite reflections m x n = +/-1, which could not be properly separated in the integration procedure. The final model includes modulations of the atomic positions as well as modulations of the thermal parameters. The latter are induced by strong differences in the neighbourhood of the actual modulated positions. The occupational modulation was neither significant for X nor for T1 sites and the sites were supposed to be occupied only by Ca and Mg, respectively. As a consequence of the Ca and O positional modulations six-, seven- and eightfold Ca coordination occur throughout the structure and the thermal ellipsoid changes its shape correspondingly. The positional modulation of the atoms causes variations in the interatomic distances which, however, do not affect bond-valence sums considerably, but induce flattening and rotation in T1 and T2 tetrahedra, respectively.

The lock-in phase in the urotropine-sebacic acid system.

The 1,10-decanedioic acid-1,3,5,7-tetraazatricyclo[3.3.1.1(3,7)]decane (1/1) system, C(10)H(18)O(4).C(6)H(12)N(4), was studied at 215 (2) K. Its analysis provides important information with regard to the long-standing acid-carboxylate controversy in the urotropine-alkanedioic acid system. In the present structure, all the chain end-groups display a clear acid character. The asymmetric unit of this commensurate modulated phase contains two molecules of diacid as well as two molecules of urotropine. Furthermore, the chain packing suggests a possible order parameter for the lock-in transition.

A novel perovskite-like Ta-bronze KTa1+zO3: preparation, stoichiometry, conductivity and crystal structure studies.

A new cubic Ta-bronze (1) KTa(1+z)(+(5-delta))O(3) [z approximately 0.107 (3)] was obtained on a cathode by molten salt electrolysis of the system K(2)TaOF(5)-K(3)TaO(2)F(4)-(KF + NaF + LiF)(eutectic). Black, metallic cubic crystals of (1) are formed together with tetragonal beta-Ta. The perovskite-like crystal structure of (1) [a = 4.005 (1) A, space group Pm3m] was refined with anharmonic displacement parameters for Ta and K atoms and anisotropic displacement parameters for a split O-atom position [KM4CCD diffractometer; lambda(Mo Kalpha); 3320 measured reflections with I > 3sigma(I); R = 0.0095, wR = 0.0065, Deltarho(min) = -0.91 e A(-3), Deltarho(max) = 0.65 e A(-3)]. Defects in the O and K atomic positions were found. (1) is a semiconductor in the temperature range 4-300 K, whereas the well studied and closely related colourless transparent crystals KTa(+5)O(3) (2) are dielectric. Differences in the properties of (1) and (2) are assumed to be connected with the existence of Ta dumb-bells statistically distributed into the KTaO(3) matrix.

Modulated structure of La2Co1.7 from neutron and X-ray diffraction data

An La(2)Co(1.7) crystal was investigated by single-crystal neutron and X-ray diffraction. The neutron measurement was performed with a Laue white-beam technique at 15 K and room temperature, using a large position-sensitive detector. The X-ray measurements were obtained at room temperature from a CCD detector. The average structure of La(2)Co(1.7) is hexagonal with cell parameters a = 4. 885 (1), c = 4.273 (2) A and space group P6(3)/mmc. The satellites are located at the vertices of small hexagons perpendicular to the c axis. The modulated crystal was indexed assuming a sixfold twinned 3 + 1 dimensional structure with q = (alpha, 0, gamma). The structure was solved in the pseudoorthorhombic cell, with a = 8.461 (1), b = 4. 885 (1), c = 4.273 (2) A, in the superspace group C2/m(alpha, 0, gamma). Owing to space requirements, the Co atoms cannot fit precisely into the octahedral sites of the La h.c.p. (hexagonal close packing). Instead, the Co atoms adopt a different periodicity, which is not commensurate with the periodicity of the La atoms. Two structure models have been refined in order to describe this behaviour, one using the sawtooth function for the positional modulation of cobalt and the other describing the structure as a composite system. The chemical composition calculated from the composite model is La(2)Co(1.8 (1)) with the estimated standard deviation arising from the variation of q for different samples. In both models lanthanum is incommensurately modulated, while the position of cobalt seems not to be affected by any relative periodic displacement.

Analysis of LiKSO4 crystals in the temperature range from 573 to 943 K.

The structural phases observed in LiKSO4 crystals due to thermotropic transitions have been studied for more than a century. Nowadays many different phases are referenced, but some of the results are still controversial. Structural studies by single-crystal X-ray diffraction from room temperature to 803 K are presented here. Phase II (708 < T < 943 K) is extensively discussed on the basis of ordered and disordered models, using harmonic and anharmonic atomic displacements, and considering a twinned crystal composed of three orthorhombic domains. Analyses of the same phase at different temperatures determine the best structure model.

Fluconazole prophylaxis prevents intra-abdominal candidiasis in high-risk surgical patients.

OBJECTIVE: To evaluate the efficacy and safety of intravenous fluconazole for the prevention of intra-abdominal Candida infections in high-risk surgical patients. DESIGN: Randomized, prospective, double-blind, placebo-controlled study. SETTING: Two university-affiliated hospitals in Switzerland. PATIENTS: Forty-nine surgical patients with recurrent gastrointestinal perforations or anastomotic leakages. INTERVENTIONS: Prophylaxis with intravenous fluconazole (400 mg per day) or placebo continued until resolution of the underlying surgical condition. MEASUREMENTS AND MAIN RESULTS: Patients were evaluated daily, and specimens for culture were obtained three times per week during prophylaxis. The primary study end points were the frequency of and the time to intra-abdominal Candida infections. Secondary end points were the frequency of candidiasis (intra-abdominal and extra-abdominal) and the emergence or persistence of Candida colonization. Among patients who were not colonized at study entry, Candida was isolated from surveillance cultures during prophylaxis in 15% of the patients in the fluconazole group and in 62% of the patients in the placebo group (relative risk, 0.25; 95% confidence interval, 0.07 to 0.96; p = .04). Candida peritonitis occurred in one of 23 patients (4%) who received fluconazole and in seven of 20 patients (35%) who received placebo (relative risk, 0.12; 95% confidence interval, 0.02 to 0.93; p = .02). In addition, one catheter-related Candida albicans sepsis occurred in a fluconazole-treated patient. Thus, overall, candidiasis developed in two fluconazole patients and seven placebo patients (relative risk, 0.25; 95% confidence interval, 0.06 to 1.06; p = .06). C. albicans accounted for 87% of the Candida species isolated before or during prophylaxis, and all C. albicans strains were susceptible to fluconazole. Fluconazole was well tolerated, and adverse events occurred at similar frequencies in both treatment groups. CONCLUSIONS: Fluconazole prophylaxis prevents colonization and invasive intra-abdominal Candida infections in high-risk surgical patients.

Flavonoid-related modulators of multidrug resistance: synthesis, pharmacological activity, and structure-activity relationships.

A series of 28 flavonoid derivatives containing a N-benzylpiperazine chain have been synthesized and tested for their ability to modulate multidrug resistance (MDR) in vitro. At 5 microM, most compounds potentiated doxorubicin cytotoxicity on resistant K562/DOX cells. They were also able to increase the intracellular accumulation of JC-1, a fluorescent molecule recently described as a probe of P-glycoprotein-mediated MDR. This suggests that these compounds act, at least in part, by inhibiting P-glycoprotein activity. As in other studies, lipophilicity was shown to influence MDR-modulating activity but was not the only determinant. Diverse di- and trimethoxy substitutions on N-benzyl were examined and found to affect the activity differently. The most active compounds had a 2,3, 4-trimethoxybenzylpiperazine chain attached to either a flavone or a flavanone moiety (13, 19, 33, and 37) and were found to be more potent than verapamil.

On the geometry of a modern imaging diffractometer.

The geometry of a modern imaging diffractometer is discussed in detail. A method to find all relevant instrument parameters from the control single-crystal measurement data is proposed and the limitations of such a procedure are indicated. Optimization of the instrument parameters by the least-squares method is presented.

Phase-transition-induced twinning in the 1:1 adduct of hexamethylenetetramine and azelaic acid.

The title compound, C(6)H(12)N(4).C(9)H(16)O(4), undergoes several thermotropic phase transitions. The crystalline structure is layered, with sheets of azelaic acid linked to sheets of hexamethylenetetramine by hydrogen bonds. In the room-temperature phase, the azelaic acid molecules are disordered. By lowering the temperature, this disorder partially disappears. The ordering is clearly observed in reciprocal space where on the rods of diffuse scattering, present in the room-temperature phase, a series of superstructure reflections emerges. This phase transition leads to twin-lattice quasi-symmetry (TLQS) twinning. The structure of this twinned phase is explored in this paper. There are two orientational domains linked by a mirror plane which relates disordered orientations of the acid molecules above the phase transition. A single domain has space group P2_1/c. The structure has been solved and refined on the complete set of data to R(1) = 0.0469. The chains remain partially disordered, showing two acid groups with unequal population: the major form corresponding to a carboxylic acid and the minor to a carboxylate. The ordering of the structure, when going through the phase transition, is interpreted in terms of stabilization by C-H.O hydrogen bonding. A least-squares estimator of the twinning volume ratio is developed that gives an expression for the twinning ratio in terms of the intensities of nonoverlapping reflections. The twinning ratio obtained in the structure refinement compares very well with that obtained from this estimator.

Effects of intravenously infused fish oil on platelet fatty acid phospholipid composition and on platelet function in postoperative trauma.

BACKGROUND: The aim of this study was to assess the short-term effect of IV infusion of fish oil emulsion on the fatty acid profiles of platelet phosphatidylcholine and phosphatidylethanolamine and on platelet function in postoperative patients. METHODS: Over a 7-day period, 10 patients received a 20% soybean fat emulsion with an added 10% marine fish oil emulsion, whereas 9 controls received only 20% soybean fat emulsion. RESULTS: By comparison with controls, in patients receiving fish oil, (1) a large increase in eicosapentaenoic acid (20:5n-3) was observed in both platelet phosphatidylcholine (1.55% +/- 0.17% vs 0.38% +/- 0.06% by weight, p < .01) and phosphatidylethanolamine 2.21% +/- 0.18% vs 0.66% +/- 0.08% by weight, p < .01); (2) eicosapentaenoic acid (20:5n-3)/arachidonic acid (20:4n-6) ratios doubled in both platelet phosphatidylcholine (p < .01) and phosphatidylethanolamine (p < .05); (3) with collagen as aggregating factor, maximal reaction speed decreased (p < .02) and latency increased (p < .002); and (4) no toxic effect, in particular no increase of postoperative bleeding and no perturbation of hepatic and renal function, was observed during the fish oil infusion. CONCLUSIONS: A short-term IV infusion of fish oil clearly modifies the platelet composition and changes some parameters of platelet function.

In vivo and in vitro effects of somatostatin and insulin on glucagon release in a human glucagonoma.

Inhibition of pancreatic glucagon secretion has been reported to be mediated by glucose, insulin and somatostatin. As no human pancreatic alpha-cell lines are available to study in vitro the relative importance of insulin and glucose in the control of pancreatic glucagon release, we investigated a patient presenting with a malignant glucagonoma who underwent surgical resection of the tumour. Functional somatostatin receptors were present as octreotide administration decreased basal glucagon and insulin secretion by 52 and 74%, respectively. The removed tumour was immunohistochemically positive for glucagon, chromogranin A and pancreatic polypeptide but negative for insulin, gastrin and somatostatin. The glucagonoma cells were also isolated and cultured in vitro. Incubation experiments revealed that change from high (10 mM) to low (1 mM) glucose concentration was unable to stimulate glucagon secretion. A dose-dependent inhibition of glucagon release by insulin was however, observed at low glucose concentration. These findings demonstrate that insulin could inhibit glucagon secretion in vitro in the absence of elevated glucose concentrations. These data suggest, as observed in vivo and in vitro in several animal studies, that glucopenia-induced glucagon secretion in humans is not mediated by a direct effect of low glucose on alpha-cells but possibly by a reduction of insulin-mediated alpha-cell suppression and/or an indirect neuronal stimulation of glucagon release.

Role of integrins and evidence for two distinct mechanisms mediating human colorectal carcinoma cell interaction with peritoneal mesothelial cells and extracellular matrix.

Peritoneal carcinomatosis involves a series of events including tumor cell interactions with mesothelial cells and the extracellular matrix (ECM). We have studied the adhesive and invasive properties of four human colorectal carcinoma cell lines (Co115, HT29, SW480, SW620) confronted in vitro with a human mesothelial cell monolayer or with the ECM proteins collagen IV, laminin-1, fibronectin, tenascin-C and vitronectin. Quantitation was achieved following staining of tumor cells with the calcein-AM fluorescent dye. We found that all four cell lines rapidly adhered to a mesothelial cell monolayer. This adhesion event was not inhibitable by anti-integrin and anti-CD44 antibodies. Following initial attachment, the SW480 and SW620 cells invaded the mesothelial cell monolayer more aggressively than HT29 and Co115 cells. All cell lines adhered to ECM proteins with each one exhibiting an individual adhesion pattern. Adhesion to matrix was completely integrin-dependent. When tested in an invasion assay, HT29 and Co115 cells crossed Matrigel-coated filters while SW480 and SW620 cells did not. This invasion was inhibited by anti-beta 1 integrin antibodies. Taken together, our results demonstrate that the initial colorectal tumor cell-mesothelial cell interaction occurs through an integrin-independent mechanism while adhesion to matrix proteins and invasion through Matrigel are integrin-dependent events. Furthermore, the different invasive capacity of SW480 and SW620 versus HT29 and Co115 cells upon interaction with a mesothelial cell monolayer or Matrigel suggests that these two invasion events may be mediated by distinct mechanisms.

[Role of lymphadenectomy in the surgical treatment of tumors]. / Place de la lymphadénectomie dans le traitement chirurgical des tumeurs.

In addition to the excision of the tumor itself, the surgical management of carcinomas includes the removal of regional lymph nodes or lymphadenectomy. The lymphatic system is not the only path of metastatic spread but it is often the main one. The percentage of tumors with lymph node metastases varies with the location and above all with the extent of the tumor at the time of surgery. For example, axillary metastases are much less frequent in cancers discovered by screening mammography than in those with clinical signs. Lymphadenectomy is important for loco-regional control and to determine the prognosis which may dictate adjuvant therapy. In some patients, it also contributes to the cure of their disease by removing lymph nodes metastases that sometimes can only be detected by immunohistochemistry. Lymphadenectomy should be very extensive when done with curative intent and very selective when performed only for prognostic information.

Haemorrhage into the pancreatic duct (Hemosuccus pancreaticus): recognition and management.

OBJECTIVE: To highlight the clinical presentation, investigation and treatment of haemorrhage into the pancreatic duct. DESIGN: Retrospective study and review of publications. SETTING: University hospital, Switzerland. SUBJECTS: All 4 cases from 1972 to 1993. INTERVENTIONS: 2 Whipple procedures, 1 resection of the pancreatic head, 1 exploratory laparotomy. Radiological embolisation in one case. MAIN OUTCOME MEASURES: Cessation of haemorrhage and survival. RESULTS: The diagnosis was made preoperatively in three cases by gastroduodenoscopy and arteriography. Operation was the primary treatment in all patients and was effective with low morbidity and no mortality in three of them. Embolisation stopped the haemorrhage in the fourth patient, who was alcoholic and died of progressive liver insufficiency and variceal haemorrhage. CONCLUSIONS: There is no specific indication for haemorrhage into the pancreatic duct. The diagnosis is suggested by endoscopy (absence of a more common cause, or blood in the second part of the duodenum). Arteriography is essential to confirm the site of the bleeding and to attempt embolization. Operation is usually the definitive treatment.

Cricotracheal resection for pediatric subglottic stenosis: update of the Lausanne experience.

Controversy still exists concerning the best treatment modality for severe (Cotton's grade III and IV) subglottic stenosis in infants and children. Although laryngotracheoplasty procedures remain the operation of choice in most centres, this series of 26 partial cricoid resections with primary thyrotracheal anastomoses show a decannulation rate of 96% (25/26 cases) after a single open procedure. Twenty-three patients practice sport freely without dyspnea, 2 show a slight exertional stridor and one teenager experienced a complete restenosis. The postoperative voice is normal in 18 (70%) and a slight residual dysphonia is present in 7 (27%). We encountered no lesion to the recurrent laryngeal nerves and no fatalities. In 10 cases, the tracheostoma site was resected during the same operative session. In the future, cricotracheal resection should be considered as an important, if not the best, treatment option for severe subglottic stenosis in infants and children.

[Value of duplex ultrasound in diagnosis of ergotism of the legs]. / Apport du duplex dans le diagnostic de l'ergotisme des membres inférieurs.

Ergot's derivatives are widely used in the treatment of migraine and in the prophylaxy of deep venous thrombosis in association with heparin. Clinical ergotism is rarely observed and can affect all the arteries, especially of the inferior limbs. Vasospasm of the peripheral arteries and collateral formation are specific findings on angiography. We report the illustrative case of a 38 years old woman hospitalized for a small bowel occlusion. She suffers from chronic migraine treated by ergotamine tartrate. During her hospitalization, she develops an acute ischemia of the lower limbs. An ergotism was clinically suspected and confirmed by Duplex sonography which demonstrate multiple vasospasm. Under iv sodium nitroprusside and peridural analgesia the spasm resolved in 24 hours. The control Duplex sonography confirm the normality of the lower limb arteries. This examination modality allow a non-invasive diagnosis and evolution control of arteriospasm.