Branched-polymer separations using comprehensive two-dimensional molecular-topology fractionation x size-exclusion chromatography.

Branching has a strong influence on the processability and properties of polymers. However, the accurate characterization of branched polymers is genuinely difficult. Branched molecules of a certain molecular weight exhibit the same hydrodynamic volumes as linear molecules of substantially lower weights. Therefore, separation by size-exclusion chromatography (SEC), will result in the co-elution of molecules with different molecular weights and branching characteristics. Chromatographic separation of the polymer molecules in sub-microm channels, known as molecular-topology fractionation (MTF), may provide a better separation based on topological differences among sample molecules. MTF elution volumes depend on both the topology and molar mass. Therefore co-elution of branched molecules with linear molecules of lower molar mass may also occur in this separation. Because SEC and MTF exhibit significantly different selectivity, the best and clearest separations can be achieved by combining the two techniques in a comprehensive two-dimensional (MTFxSEC) separation system. In this work such a system has been used to demonstrate branching-selective separations of star branched polymers and of randomly long-chain-branched polymers. Star-shaped polymers were separated from linear polymers above a column-dependent molecular weight or size.

Diarrheal morbidity and mortality in children in the Central African Republic.

Diarrheal morbidity and mortality in children less than 5 years old were studied in Bangui, Central African Republic, by a cluster survey. We found a high prevalence of diarrheal disease with an estimated annual incidence of 7 episodes of diarrhea per child per year. The estimated annual mortality rate for children less than 5 years old was 28.6 per 1,000 and 85.8 per 1,000 for infants; 51.6% of deaths were reported to be associated with diarrhea. During the survey, stool specimens were collected from 133 children with current diarrhea and 117 control children to study the etiologic agents of diarrheal disease in the community. An enteric pathogen was identified in 58% of diarrheal children's stools and 48% of stools of well children. A statistically significant association between diarrhea and rotavirus was found, with it being isolated from 8 of 33 (24%) of stools of infants with diarrhea compared to 0 of 25 (0%) of control infants. Isolation rates for Campylobacter jejuni, Entamoeba histolytica, pathogenic Escherichia coli, and other bacterial enteropathogens did not differ significantly between children with diarrhea and control children.

PIP: Using a cluster sample survey, researchers studied diarrheal morbidity and mortality in children 5 years old in Bangui, Central African Republic in November 1983. They collected fecal samples from all children who had diarrhea the day of the investigation. They also took stools from children not ill with diarrhea at the time and who had 3 stools/day for the past week. Researchers looked for an age matched control in the same cluster, but not in the same home, for each child with diarrhea. They were unable to explain at least 42% of the diarrhea cases and much more when they considered the high isolation rates among the nondiarrheic children. This highlights the need for further research to better understand the carrier state. 57.8% of the diarrheic children's stools had 1 or more enteric pathogens, while 47.8% of the nondiarrheic children's tools did. In children 1 year old, rotavirus was the most frequent enteropathogen associated with diarrhea (p.05). Parasitic organisms were found more frequently as the age of the child increased. A high carrier state of different enteric pathogens existed, including Campylobacter jejuni, Entamoeba histolytica, Giardia intestinalis, and enteropathogenic Escherichia coli. The annual child and infant mortality rates were very high (28.6/1000 and 85.8/1000 respectively). Death was related to diarrhea in 19.1% of the cases and associated with diarrhea in 50% of the cases. The annual attack rate stood at 7 episodes/child which is greater than is usually reported.

Antibodies to Lassa and Lassa-like viruses in man and mammals in the Central African Republic.

715 human sera from different locations in the Central African Republic were tested by indirect immunofluorescence against the three African arenaviruses, Lassa, Mobala and Mopeia. Four were positive for Lassa, seven for Mobala, and one for both Lassa and Mopeia. The epidemiology of African arenaviruses is discussed.

Number-average molecular mass determination of polymeric material by pyrolysis-gas chromatography.

The number-average molecular mass of a polymeric material has been determined by pyrolysis-gas chromatography (Py-GC) via end-group analysis. The major advantage of this technique is that no sample preparation is required. The sample is not required to be in the dilute solution form, and the amount of sample needed is approximately 0.5 mg. Phenyl group-terminated polybutadiene systems have been studied as an example. The application of Py-GC to obtain the end-group concentration, the number-average molecular mass and the limitations of this method are discussed in detail. The success of this development elevates the role of Py-GC as an important technique for end-group analysis for the determination of number-average molecular mass.

[Toxoplasmosis in the Central African Republic. Complementary study in a rural area]. / La toxoplasmose en République centrafricaine (RCA). Etude complémentaire en zone rurale.

The epidemiological survey on the incidence of toxoplasmosis in rural areas of Central African Republic was carried out on a healthy population. The 814 samples came from 5 regions with 4 different climates. About 40% of the adults had IgG antibodies against Toxoplasma gondii except in pre-desert area where only 25% were positive. Girls became positive earlier than boys, but there was no difference between adult men and women except in pre-desert zone where men were more positive.

[Mycoses in AIDS in the Central African Republic]. / Les mycoses au cours du S.I.D.A. en République Centrafricaine.

Among the 155 cases of A.I.D.S. observed by the authors in Bangui (C.A.R.) from April 1985 to February 1986, 49 patients (31.6%) were carriers of mycosis. 42 candidosis, 5 cryptococcosis, 2 aspergillosis were found; the authors describe the clinical aspects, the localizations and the methods of diagnosis.

[Kaposi's sarcoma in Burundi and the Central African Republic in the framework of acquired immunodeficiency syndrome (AIDS)]. / Le sarcome de Kaposi au Burundi et en République centrafricaine dans le cadre du syndrome d'immunodépression acquise (S.I.D.A.).

The authors carried out in 1985 a survey in two French speaking States in Central Africa, namely Burundi and Central African Republic (C.A.R.), in order to study the links between Kaposi sarcoma (K.S.) and A.I.D.S. In Burundi the prospective study conducted in Bujumbura, lead to collect in one year 25 cases of K.S. out of them 24 linked to A.I.D.S. No group at risk has been identified. The 24 K.S. linked to A.I.D.S. present a stage IV (cutaneous and visceral form) in 21 cases. 20 of them got an associated affection, 5 being tuberculosis bacteriologically confirmed. All of them present a cellular immunity deficiency. Evolution was fatal in 22 cases out of 24, average presumption of survival was 10 months. In C.A.R., retrospective survey conducted in Bangui made possible to find out 24 cases in 4 years, of which 20 having had a L.A.V. antibodies research, were considered. 9 of them were linked to A.I.D.S. No group at risk. 7 patients presented a sporadic form, 6 an African endemic form, 7 an epidemic form with associated infection. Out of 9 LAV positive patients, 5 deceased. Out of 11 LAV negative patients, 3 deceased with a A.I.D.S. clinical aspect. This survey carried out in Burundi and in C.A.R. demonstrates that K.S. is significantly in increase in these two countries. In Burundi it is significantly linked to A.I.D.S. In C.A.R., classical African K.S. do exist (sporadic, endemic), as well as K.S. linked to A.I.D.S., as underlined recently in Bayley's publications in Zambia. Since A.I.D.S. has been detected, it does exist an outbreak and a new clinical form of K.S. in Central Africa.

[Clinical aspects of AIDS in the Central African Republic]. / Aspects cliniques du SIDA en République Centrafricaine.

AIDS is known in Central African Republic since 1983: 64 recognized cases have been registered. AIDS is of endemic aspect presenting the main following signs: lost of weight (100%), degeneration of the health status (80%), lymphadenopathy (46%), pneumopathy (44%), diarrhea (40%), candidiasis (21%), Kaposi's disease (16%), purpura (8%), pruritus (8%), Cutaneous anergy to tuberculin or to the 7 antigens (Merieux test) is constant. LAV serology was positive in 61 cases. The number of helper T. cells is less than 400/mm3, and OKT4/OKT8 ratio is less than 0.50. The concerned population is heterosexual with a sexual hyperactivity.

Development of high temperature comprehensive two-dimensional liquid chromatography hyphenated with infrared and light scattering detectors for characterization of chemical composition and molecular weight heterogeneities in polyolefin copolymers.

The application of high temperature comprehensive two-dimensional (2D) liquid chromatography for quantitative characterization of chemical composition and molecular weight (MW) heterogeneities in polyolefins is demonstrated in this study by separating a physical blend of isotactic-polypropylene, ethylene-random-propylene copolymer, and high density polyethylene. The first dimension separation is based on adsorption liquid chromatography that fractionates the blend from low to high ethylene content. The second dimension is size-exclusion chromatography connected with light scattering (LS) and infrared (IR) detectors. The IR detector shows desired sensitivity and linearity for monitoring analyte concentrations in the eluent after 2D separations. In addition, the compositions of the analytes are also determined from the ratio of two IR absorbances at the specified wavelength regions, an absorbance for measuring the level of methyl groups in polyolefins and another absorbance for measuring concentration. The LS detector is used to determine absolute molecular weight of the analytes from the ratio of the light scattering signal to the IR concentration signal. The ability to obtain concentration, chemical composition, and MW of polyolefins after 2D separation provides new opportunities to discover structure-property relationships for polyolefins with complex structures/architectures.

[Report on intestinal parasitosis in adults in an urban population of the Central African Republic]. / Bilan des parasitoses intestinales de l'adulte dans un milieu urbain de la République Centrafricaine.

The authors point out the frequency of intestinal parasitism in Bangui, biggest town and capital of the CAR. Out of 3,352 samples, 1,570 were found positive. The main parasites found were: Ankylostoma duodenale, 26,7%; Schistosoma mansoni, 20,8%; Entamoeba histolytica, 18,2%. The authors underline the polyparasitism. They also emphazide the differences with another study carried out in Algiers and surrounding areas.

[Toxoplasmosis in the Central African Republic: first survey]. / La toxoplasmose en République Centrafricaine (R. C. A.): premiers sondages.

For this purpose, toxoplasma antibodies were determined by latex agglutination test. Two kinds of human sera were examined: people in "good health" from North of Centrafrican Republic and patients from Bangui. In North, 40% of sera gave positive results and young girls from 1 to 14 years old seem to become positive earlier than young boys. At Bangui, 81% of sera from pregnant women coming from Medical Service was positive; all from 8 patients with ocular affections was positive and only 5 on 10 with adenopathy.

[Rift Valley Fever and phleboviroses in the Central African Republic]. / La fièvre de la Vallée du Rift et les phléboviroses en République centrafricaine.

During 1984 and 1985, six Rift Valley Fever virus strains (RVF) were isolated in Central African Republic, among them five from human samples. Three strains were isolated in 1985 at the end of the rainy season, from sera of patients dead with severe jaundice with haemorrhagic syndrome, what could evoke a little outbreak. At this occasion, these RVF strains and the other strains of phleboviruses previously isolated in CAR, were antigenically compared by Immuno-fluorescent assay (IFA) and Complement Fixation Test (CF), using mice immuno ascitic fluids prepared against each strain. A lot of cross reactions were noted between the different strains, but all the RVF strains seem to have the same antigenic outline.

[Bacteriological and clinical aspects of Salmonella typhi infections in the Central African Republic. Evaluation of a 3-year study in Bangui]. / Aspects bactériologiques et cliniques des infections à Salmonella typhi en République Centrafricaine. Bilan d'une étude de 3 années à Bangui.

Authors have isolated and identified 229 strains from patients with typhoid syndrome . The bacteriology of each strain was studied. We have observed the extension of A (subtype Dakar) lysotype to Central Africa from West Africa. All the strains are resistant for G penicillin. Clinical features are quite the same as in mild countries, with a high incidence in children. The typhoid fever is frequent and precocious in CAR, where prophylaxis by vaccination is not usual.

[Prevalence of bilharzia antibodies in the pediatric population of the village of Pointe-Noire (Republic of the Congo)]. / Prévalence des anticorps antibilharziens dans la population infantile de la ville de Pointe-Noire (R. P. Congo).

Thirty clusters of children have been tested for schistosomiasis serology in the town of Pointe-Noire (Popular Republic of Congo). Out of 360 patients, 3 presented antibodies against schistosomiasis. The antibodies prevalence of this parasitosis is 0.83% +/- 0.008% which is very low as compared to other areas of the country.

Distribution and serotypes of Campylobacter jejuni and Campylobacter coli in enteric Campylobacter strains isolated from children in the Central African Republic.

One hundred eighty-five enteric Campylobacter strains isolated from diarrheic or healthy children in Bangui (Central African Republic) were studied to determine their species and serotypes. C. coli was identified in 38.9% of all strains and in 43.9% of strains from diarrheic children. By the hemagglutination technique for heat-stable antigens, 73.5% of the strains could be serotyped. Of the typeable strains, 75% were distributed among 13 more frequent serotypes. C. coli serotype Pen 37,56 was the most common serotype from diarrheic children.

[Current serologic data on viral hemorrhagic fevers in the Central African Republic]. / Données sérologiques actuelles sur les fièvres hémorragiques virales en République centrafricaine.

During the years 1984-1985, 1,528 serum samples were taken through out the CAR. Of these sera, 319 (20.8%) contained anti-Filoviridae antibodies (Ebola, Marburg). This figure is higher than those found in Cameroon, Sudan, Gabon and Zaïre. Three zones of the country are particularly exposed, the North-East where the population is in the contact with Sudan Ebola, the South-East where it is in contact with Zaïre Ebola, and the South-West where it is in contact with Sudan Ebola. The authors believe that there could exist either a Central African Ebola strain or an Ebola-Like less pathogenic virus which is responsible for cross reactions. Results concerning Rift Valley Fever virus, Congo virus and Lassa virus seem less interesting. However RVF and Congo strains were isolated.

[Role of delta viruses in fulminating hepatitis in Central Africa]. / Le rôle du virus delta dans les hépatites fulminantes en Afrique Centrale.

The delta virus (DV) was shown to be the predominant but not exclusive aetiology in 124 cases of fulminating hepatitis (FH) in the Central African Republic. The condition occurs in an endemo-epidemic form in young adults with no apparent risk factors. The mortality is high (88 p. 100) and the clinical features well established. After a short prodromic period, the patients develop severe jaundice, hepatic encephalopathy, and, in over 1/3 of cases, severe haemorrhage. Biologically, the main changes are related to hepatic cytolysis and insufficiency. Histology shows appearances of spongiocytic (steatosic) hepatitis in 81 p. 100 of cases. HBS antigen is found in 90 p. 100 of cases and DV markers are present in 53 p. 100 of these. The HBS Ag also occurs in 60 to 90 p. 100 of the close relatives of the patients and anti-DV antibodies occur in 40 to 90 p. 100 of these subjects. To the authors' knowledge, this is the first published series to demonstrate FH associated with DV in the African continent.

[Prevalence of hepatitis B surface antigen and determination of its subtypes in the Central African Republic]. / Fréquence de l'antigène HBs et détermination de ses sous-types en République centrafricaine.

To contribute to the epidemiology of hepatitis B, the authors report the results of a survey made in Bangui. This survey was performed on patients hospitalized in the department of medicine of the University Hospital. Some of the patients had a clinically typical hepatitis. HBsAg prevalence was 15.4%. The subtypes detected were: ay (8%), ayw2 (4%), ayw4 (88%). Those data are compared with other data obtained through medical publications in Central Africa.

Parasitic, bacterial, and viral enteric pathogens associated with diarrhea in the Central African Republic.

A total of 1,197 diarrheic children less than 15 years old were investigated for parasitic, bacterial, and viral enteropathogens from March 1981 through February 1982 in the Central African Republic. One or more pathogens were identified from 49.4% of the patients. Rotavirus was the most frequently identified pathogen among children less than 18 months old. Enteropathogenic Escherichia coli was the second most frequently isolated pathogen (12.1%) in children less than 2 years of age. Campylobacter jejuni was also isolated frequently from diarrheic children less than 5 years of age (10.9%). Entamoeba histolytica was identified in very young children and was found to be the most frequent enteropathogen associated with diarrhea in children over the age of 2 years. Enterotoxigenic Escherichia coli was rarely isolated (ca. 2%). There was a peak in the incidence of rotavirus during the dry season and in the incidence of Campylobacter jejuni during the rainy season.