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Luigi Pasqua Antonio Procopio Manuela Oliverio Rosina Paonessa Roberta Prete Monica Nardi Maria Francesca Casula Flaviano Testa Janos B. Nagy 《Journal of Porous Materials》2013,20(4):865-873
Hybrid materials obtained through a Microwave-assisted grafting of organic functional groups on mesoporous silica (MCM-41 type) have been characterized by X-ray powder diffraction, TG-DSC, N2 adsorption, solid state 13C- and 29Si-NMR, TEM and SEM. The studied grafting procedure is effective in the preparation of hybrid organosilicas under solvent-free conditions. Microwaves allows an ultra-fast and clean functionalization of the mesoporous materials and the method has been applied to produce a wide series of functional materials. The hybrid materials maintain the original mesoporous structure when the loading of linked organic groups does not exceed 10 %. In this cases, the slight pore volume reduction is linearly correlated to the organic amount in the product. If functional groups able to interact among them through hydrogen bond are used, hybrid materials exhibit high Organic/SiO2 ratios and low pore volumes due to the formation of a network occluding the pores, where functional groups of free organosilane molecules interacts with the functional groups of molecules linked to the matrix. NMR data confirm that the network is composed by organosilane molecules linked or not to the framework. Acid washing is able to labilize hydrogen bond and open the network. In the case of bulky but chemically inert functionalising agents the network is not produced. 相似文献
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Acute appendicitis caused by Ascaris lumbricoides is an uncommon variant of a common disease. We describe a case in which sonography was used for preoperative diagnosis of ascaris appendicitis. 相似文献
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BACKGROUND: Abdominal tuberculosis (TB) is common. But the diagnosis of abdominal TB is fraught with difficulties as it is often not possible to get a microbiological confirmation of the infection. We therefore undertook this study to highlight those pertinent clinical and laboratory features which would enable one to make a provisional diagnosis of abdominal TB early, to pave way for a trial of anti-tuberculosis chemotherapy. METHOD: This is a retrospective study of 12 patients treated for abdominal TB in our department over a period of 2 years. FINDINGS: Seven of the patients suffered from chronic diarrhoea for periods ranging from 4 weeks to 12 months. Four patients had progressive abdominal distension (ascites). The last patient came in with multiple abdominal swellings. Seven patients had clinical and biochemical features of malabsorption. Another 9 patients also had persistent pyrexia. The ascitic fluid was exudative in the 4 patients mentioned earlier. A definitive diagnosis could not be established in any of these patients. The diagnosis of abdominal TB was thus one of exclusion in these patients who showed prompt response to anti-tuberculosis therapy. CONCLUSION: Our study justifies a trial of anti-TB chemotherapy in TB endemic areas in the following clinical situations: (a) patients with chronic diarrhoea of unknown aetiology and (b) patients with exudative ascitic fluid, after all other possible causes, have been excluded. A prompt response to anti-TB therapy should be accepted as sufficient ground for the diagnosis of abdominal TB even when histopathological or microbiological confirmation of the disease is not possible. Our study reflects the experience of other workers from Third World countries. 相似文献
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Until quite recently, the cardiodepressant actions of adenosine were widely accepted. A nucleoside that produces negative chronotropic and ionotropic effects, adenosine, has been used clinically as the drug of choice for terminating supraventricular (atrioventricular node) tachycardia and is likely to play an important part in regulating arrhythmogenic activity as an endogenous antiarrhythmic metabolite. Despite this, recent experimental data, particularly resulting from in vitro studies using animal models, have shown a paradoxical excitable action of adenosine in the heart. In this article, Amir Pelleg and Steven Kutalek present the reasons why they continue to believe that any excitatory actions of adenosine in the heart are clinically irrelevant. 相似文献
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Distinct stability of recombinant L and H subunits of human ferritin: calorimetric and ANS binding studies 总被引:1,自引:0,他引:1
Thermodynamic and pH stability of recombinant human L- and H-ferritins were
probed by differential scanning calorimetry and 8-anilino-1-
naphthalenesulfonate (ANS) binding in the pH range 2-7. At pH 2.0-2.8 they
were dissociated into subunit monomers and in this pH interval the
H-subunit displayed a single calorimetrically-revealed domain with
properties of a molten globule-like state: low enthalpy (6.3-8.0 J/g or
169-172 kJ/mol) and Tm of thermal unfolding (approximately 50 degrees C), a
wide transition range (approximately 20 degrees C) and high ANS binding. In
contrast, at pH 2 the L-ferritin subunit showed two calorimetric domains
with Tm of 35 and 40 degrees C with similar unfolding enthalpies and with
moderate extent of interactions, as indicated by the ratio of calorimetric
enthalpy (293.9 kJ/mol) and van't Hoff enthalpy (174.2 kJ/mol) for the
thermal transition. A pH increase from 2.0 to 2.8 determined the coupling
of the two domains into a single cooperative folding unit and drastic
increase of the transition temperature (from 37 to 80 degrees C). The
contacts between the two domains in the L-subunit appeared to contribute to
about 30% of the total stabilization free energy. The unfolding enthalpies,
heat capacity changes and pronounced ANS binding of the L-subunit at pH
2.0- 2.8 indicated that part of the structure lacked 'meltable' tertiary
interactions. The results indicate that H- and L-subunits are stabilized by
largely different intra-chain interactions with a critical contribution to
L-subunit stability of embedded salt bridge(s) absent in the H-subunit.
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