Silica Nanoparticles in Xanthan Gum Solutions: Oil Recovery Efficiency in Core Flooding Tests.

Polymer flooding is one of the enhanced oil recovery (EOR) methods that increase the macroscopic efficiency of the flooding process and enhanced crude oil recovery. In this study, the effect of silica nanoparticles (NP-SiO2) in xanthan gum (XG) solutions was investigated through the analysis of efficiency in core flooding tests. First, the viscosity profiles of two polymer solutions, XG biopolymer and synthetic hydrolyzed polyacrylamide (HPAM) polymer, were characterized individually through rheological measurements, with and without salt (NaCl). Both polymer solutions were found suitable for oil recovery at limited temperatures and salinities. Then, nanofluids composed of XG and dispersed NP-SiO2 were studied through rheological tests. The addition of nanoparticles was shown to produce a slight effect on the viscosity of the fluids, which was more remarkable over time. Interfacial tension tests were measured in water-mineral oil systems, without finding an effect on the interfacial properties with the addition of polymer or nanoparticles in the aqueous phase. Finally, three core flooding experiments were conducted using sandstone core plugs and mineral oil. The polymers solutions (XG and HPAM) with 3% NaCl recovered 6.6% and 7.5% of the residual oil from the core, respectively. In contrast, the nanofluid formulation recovered about 13% of the residual oil, which was almost double that of the original XG solution. The nanofluid was therefore more effective at boosting oil recovery in the sandstone core.

Effect of Silica Nanoparticles in Xanthan Gum Solutions: Evolution of Viscosity over Time.

The effect of silica nanoparticles (NP-SiO2) in xanthan gum (XG) solutions was investigated through the analysis of viscosity profiles. First, hydrocolloid XG solutions and hydrophilic NP-SiO2 suspensions were characterized individually through rheological measurements, with and without salt (NaCl). Then, nanofluids composed of XG and NP-SiO2 dispersed in water and brine were studied through two different aging tests. The addition of nanoparticles was shown to produce a slight effect on the viscosity of the fresh fluids (initial time), while a more remarkable effect was observed over time. In particular, it appears that the presence of NP-SiO2 stabilizes the polymer solution by maintaining its viscosity level in time, due to a delay in the movement of the molecule. Finally, characterization techniques such as confocal microscopy, capillary rheometry, and Zeta potential were implemented to analyze the XG/NP-SiO2 interaction. Intrinsic viscosity and relative viscosity were calculated to understand the molecular interactions. The presence of NP-SiO2 increases the hydrodynamic radius of the polymer, indicating attractive forces between these two components. Furthermore, dispersion of the nanoparticles in the polymeric solutions leads to aggregates of an average size smaller than 300 nm with a good colloidal stability due to the electrostatic attraction between XG and NP-SIO2. This study proves the existence of interactions between XG and NP-SiO2 in solution.

Chlamydia detection and management.

BACKGROUND: Chlamydia trachomatis is a common, often asymptomatic sexually acquired infection with serious sequelae if left untreated. OBJECTIVE: To describe the prevalence, clinical features, investigations, indications for screening, contact tracing and treatment of complicated and uncomplicated infection with C trachomatis. DISCUSSION: The availability of DNA amplification tests with improved sensitivity and the introduction of single dose therapy for the treatment of uncomplicated infection has simplified the management of C trachomatis infection. The general practitioner (GP) is ideally placed to reduce the burden of disease in the population with implementation of a targeted screening program for C trachomatis. However, the GP will need to continue to remain vigilant to the subtle symptoms and signs of unrecognised or asymptomatic infection and ensure contact tracing of sexual partners is actively pursued.

[The radiolesions of the small bowel (author's transl)]. / Les radiolésions du grêle.

The irradiation of the pelvic abdominal cancers extends beyond the centre of the tumour and may induce actinic digestive lesions. The bowel and more rarely the small bowel--which is the subject-matter of our study--are concerned by those radiolesions that are favoured by therapeutic overdose, post-operative adhesions fastening the bows, radio-surgical or chemicostatic associations, and lastly by vascular or nutritive deficiencies. One may distinguish between two kinds of lesions, depending on the lapse of time before their coming out and on the symptoms. The early or acute types are characterized by a radio-mucitis and give an exsudative enteropathy with anorexia, vomiting, diarrhoea and loss of weight, of which the diagnosis is easy because it occurs during the irradiation and lessens at the end of the treatment. The late radiolesions of the small bowel are characterized by sclerosis and chronic endarteritis and, after a longlasting period of latency, give varied symptoms: disordered intestinal transit which sometimes is irreversible, perforation, fistula, syndrome of malabsorption, giving often rise to be mistaken for a recurrence of the cancer. The treatment varies whether the lesion is segmental or diffuse. In the first case, the failure of the medical means accounts for the surgical cutting away or the internal derivation; in the second case, the digestive mutilation which would result from an enlargement of the lesion commands to be more cautions and to call for the methods of parenteral feeding and digestive setting to rest.

[Recurrent familial thromboembolic disease due to congenital deficiency in anti-thrombin III. Preliminary study of 3 cases (author's transl)]. / Maladie thrombo-embolique familiale récidivante par déficit congénital en anti-thrombine III. Etude préliminaire de 3 observations.

The three cases reported, two mesenteric venous infarctions and one asymptomatic carrier, prove the responsibility of the anti-thrombin III deficiency in the development of apparently primary entero-mesenteric venous infarctions. Thus such a deficiency should be sought routibs. Furthermore, these 3 cases confirm the usual characteristics of the 10 familial cases collected since the princeps description of Egeberg: recurrent thromboembolic disease in the young subject involving essentially the lower limbs, relative resistance to heparin, family history of thromboembolic disease confirming the hereditary nature of the disease with dominant transmission, laboratory confirmation of the quantitative deficiency in antithrombin III, the levels and activity of which are reduced by half, and decrease in laboratory sensitivity to heparin contrasting with normal clotting studies. The family history reveals associated conditions within the syndrome: asthma and Biermer's anemia as well as similarities in leucocyte HLA groups.

[Surgical management of left colon and rectal radiation injuries (author's transl)]. / Traitement chirurgical des radiolésions du colon gauche et du rectum.

A. First of all, we can affirm after the analysis of 132 records: the predominance of gynecologic cancers and the frequent responsibility of medical associations in the determinism of advanced radiation injuries of colon and rectum; the typically variable appearence of these injuries with an usual delay going from 6 months to a year and limits from 2 months to 35 years; the difficulty of diagnosis between radiation injurie and recurrence of cancer especially in case of fistula and the severe forecost in case of cancer radiation injurie association. B. The surgical management exist only for non-indications and failures of medical treatment; the one stage resection with end to end anastomosis will be made exclusively on advanced, therefore non evolving and limited injuries; in most cases, the multiple stage resection must be preferred: first derivation in selected part (sigmoid or transverse colon) and secondary resection in healthy area; as regards the closure of colostomy, it must never occur before a 6 months delay and anastomosis radiologic check.

[Diagnostic traps and procedure to follow in radio-invisible biliary calculi]. / Pièges diagnostiques et conduite à tenir dans la lithiase biliaire radio-invisible

Instead of the term biliary microlithiasis, the authors prefer the general concept of radio-invisible biliary lithiasis. The size, the homogeneity, the site and chemical composition of the gall stones, which are the usual criteria of biliary microlithiasis, also are valid for radio-invisibility; thus the diagnostic traps are the only original characteristics of a pathology with hazy outlines, defined as one which escapes well conducted a radiological exploration. Biliary micro-lithiasis therefore raises a triple problem. The indications for biliary surgical exploration, in spite of normal cholangiography, seem to us undoubted in acute relapsing pancreatitis, once the usual medical causes have been eliminated. It should be more relative in pure biliary pain which first requires, not only repeated cholangiography, but also constant clinical and laboratory signs which suggest that the symptoms are organic and that gall stones are in formation. After laparotomy, cholecystectomy is required, not only in perceptible lithiasis, but also when the gall bladder bile contains mud, débris, sand or cholesterol spheroids. In the other cases, the choice between abstention or cholecystectomy depends on the clinical and laboratory context. The surgical attitude with regard to the common bile duct is discussed in three possibilities depending on the case, e.g. routine exploration, abstention or exploration in certain cases.