Blown-extruded low density polyethylene (LDPE) and polypropylene (PP) films were submitted to accelerated weathering in water in order to identify their fragmentation mechanism and to compare the ...fragments number, size and shapes generated for long irradiation time. The study of the chemical modification during weathering was performed by following the progressive oxidation (FTIR, contact angle), increase of crystallinity (DSC) and surface rigidity (AFM) for the two polymers. It was demonstrated that although the kinetics of degradation is faster for PP than for LDPE films, the same fracture mechanism namely slow crack propagation is observed for both polymers. The analysis of the cracks structures on the surface of the films by AFM indicates that the crack initiation and propagation strongly depends on the crystalline morphology of the polymer. Indeed, for both material cracks propagation mainly occurs in the direction perpendicular to the extrusion direction explaining the elongated shape observed for the LDPE fragments. However, for PP film, the presence of spherulite structures induced the initiation of cracks in other directions (between the lamellae) leading to the formation of an increased number of fragments significantly smaller and with non-elongated shape compared to LDPE. To our knowledge this study is the first to directly link the size, shape distributions of plastics fragments to the crystalline morphology of the weathered polymers. These results point out the importance of taking into account the crystalline morphology to predict plastic fate in the environment.
•Fragment number, size and shape crated during the fragmentation of polyolefin films strongly depends on the crystalline structure of the polymer.•As demonstrated by AFM force spectroscopy, by limiting the increase of surface rigidity water favors the crack propagation in semi-crystalline polymer.•For PP and LDPE films, as detected by water contact measurement, oxidation begin in the first days of accelerated weathering but cannot be detected by FTIR spectroscopy because of its limited sensitivity.•PP oxidizes faster than PE. No difference in term of recrystallization kinetic is observed between the two materials.
Abstract Objective To determine the risk of lung cancer associated with exposure at home to the radioactive disintegration products of naturally occurring radon gas Design Collaborative analysis of ...individual data from 13 case-control studies of residential radon and lung cancer. Setting Nine European countries. Subjects 7148 cases of lung cancer and 14 208 controls. Main outcome measures Relative risks of lung cancer and radon gas concentrations in homes inhabited during the previous 5-34 years measured in becquerels (radon disintegrations per second) per cubic metre (Bq/m3) of household air. Results The mean measured radon concentration in homes of people in the control group was 97 Bq/m3, with 11% measuring > 200 and 4% measuring > 400 Bq/m3. For cases of lung cancer the mean concentration was 104 Bq/m3. The risk of lung cancer increased by 8.4% (95% confidence interval 3.0% to 15.8%) per 100 Bq/m3 increase in measured radon (P = 0.0007). This corresponds to an increase of 16% (5% to 31%) per 100 Bq/m3 increase in usual radon—that is, after correction for the dilution caused by random uncertainties in measuring radon concentrations. The dose-response relation seemed to be linear with no threshold and remained significant (P = 0.04) in analyses limited to individuals from homes with measured radon < 200 Bq/m3. The proportionate excess risk did not differ significantly with study, age, sex, or smoking. In the absence of other causes of death, the absolute risks of lung cancer by age 75 years at usual radon concentrations of 0, 100, and 400 Bq/m3 would be about 0.4%, 0.5%, and 0.7%, respectively, for lifelong non-smokers, and about 25 times greater (10%, 12%, and 16%) for cigarette smokers. Conclusions Collectively, though not separately, these studies show appreciable hazards from residential radon, particularly for smokers and recent ex-smokers, and indicate that it is responsible for about 2% of all deaths from cancer in Europe.
The paper presents a simple and inexpensive reusable biosensor for determination of the concentration of adenosine-5′-triphosphate (ATP) in aqueous samples. The biosensor is based on a conductometric ...transducer which contains two pairs of gold interdigitated electrodes. An enzyme hexokinase was immobilized onto one pair of electrodes, and bovine serum albumin-onto another pair (thus, a differential mode of measurement was used). Conditions of hexokinase immobilization on the transducer by cross-linking via glutaraldehyde were optimized. Influence of experimental conditions (concentration of magnesium ions, ionic strength and concentration of the working buffer) on the biosensor work was studied. The reproducibility of biosensor responses and operational stability of the biosensor were checked during one week. Dry storage at −18°C was shown to be the best conditions to store the biosensor. The biosensor was successfully applied for measurements of ATP concentration in pharmaceutical samples. The proposed biosensor may be used in future for determination of ATP and/or glucose in water samples.
Display omitted
•A conductometric biosensor for determination of adenosine triphosphate was created.•It is based on enzyme hexokinase immobilized on interdigitated planar electrodes.•Quick response, simplicity, and low cost are advantages of the biosensor.•The biosensor can be used in for determination of ATP in water samples.
This study aimed at the development and optimization of a potentiometric biosensor based on pH-sensitive field-effect transistors and acetylcholinesterase for aflatoxin B1 determination in real ...samples. Optimal conditions for bioselective elements operation were defined and analytical characteristics of the proposed biosensor were studied. The proposed biosensor characterized high operational stability and reproducibility of signal. Selectivity of acetylcholinesterase-biosensor to aflatoxins in relation to other groups of toxic substances was analyzed. The developed biosensor was applied to the determination of aflatoxin B1 in real samples (sesame, walnut and pea).
Display omitted
•The new potentiometric biosensor for aflatoxin B1 analysis was created.•The main analytical characteristics of the developed biosensor were studied.•The optimal conditions of biosensor work with real samples were defined.•The developed biosensor was applied for aflatoxin B1 analysis in real samples.
•Novel biosensor was proposed for determination of patulin inhibitory potency.•Biosensor principle was based on urease inhibition by patulin.•The proposed biosensor was optimized for analysis of ...patulin inhibitory potency.•The developed biosensor was characterized by a high sensitivity to patulin.•Selectivity of the developed biosensor to different groups of toxins was analyzed.
The research is aimed at the development and optimization of conductometric biosensor for determination of the inhibitory potency of patulin and verification of its feasibility after reactivation. A differential pair of gold interdigitated electrodes deposited on the sital substrate was used as the conductometric transducer of a signal. Urease, co-immobilized with bovine serum albumin by cross-linking with glutaraldehyde on the transducer surface, served as a bioselective membrane. The proposed biosensor was optimized for determination of the inhibitory potency of patulin. It was characterized by quite high sensitivity to patulin, good selectivity and signal reproducibility. A multiple restoration of the biosensor activity after use was rendered possible by a cysteine treatment. It was also tested the sensitivity of the biosensor developed to other groups of toxic substances. In the future, the proposed biosensor can be successfully used for the patulin analysis in real samples.
Creatine kinase (CK: adenosine-5-triphosphate–creatine phosphotransferase) is an important enzyme of muscle cells; the presence of a large amount of the enzyme in blood serum is a biomarker of ...muscular injuries, such as acute myocardial infarction. This work describes a bi-enzyme (glucose oxidase and hexokinase based) biosensor for rapid and convenient determination of CK activity by measuring the rate of ATP production by this enzyme. Simultaneously the biosensor determines glucose concentration in the sample. Platinum disk electrodes were used as amperometric transducers. Glucose oxidase and hexokinase were co-immobilized via cross-linking with BSA by glutaraldehyde and served as a biorecognition element of the biosensor. The biosensor work at different concentrations of CK substrates (ADP and creatine phosphate) was investigated; optimal concentration of ADP was 1mM, and creatine phosphate – 10mM. The reproducibility of the biosensor responses to glucose, ATP and CK during a day was tested (relative standard deviation of 15 responses to glucose was 2%, to ATP – 6%, to CK – 7–18% depending on concentration of the CK). Total time of CK analysis was 10min. The measurements of creatine kinase in blood serum samples were carried out (at 20-fold sample dilution). Twentyfold dilution of serum samples was chosen as optimal for CK determination. The biosensor could distinguish healthy and ill people and evaluate the level of CK increase. Thus, the biosensor can be used as a test-system for CK analysis in blood serum or serve as a component of multibiosensors for determination of important blood substances. Determination of activity of other kinases by the developed biosensor is also possible for research purposes.
Display omitted
•Reusable amperometric enzyme biosensor for creatine kinase detection was developed.•Optimal concentrations of creatine phosphate and ADP were studied.•Conditions for measurements of real samples were determined.•Different concentrations of creatine kinase in blood serum were measured.
Role of sialendoscopy in juvenile recurrent parotitis (JRP) Berta, E.; Angel, G.; Lagarde, F. ...
European annals of otorhinolaryngology, head and neck diseases,
December 2017, 2017-Dec, 2017-12-00, 20171201, Letnik:
134, Številka:
6
Journal Article
Recenzirano
Odprti dostop
Juvenile recurrent parotitis (JRP) is a rare disease of childhood occurring between the ages of 3 and 5 years, characterized by recurrent non-suppurative parotitis, spontaneously evolving towards ...parotid gland dysfunction. Clinically, JRP presents in the form of unilateral or bilateral, usually asynchronous, swelling of the parotid gland. The diagnosis is based on ultrasound characteristics. Widespread use of sialendoscopy has opened up new prospects for the management of this disease. This review of the literature evaluates the role of sialendoscopy in the management of JRP. A Medline search retrieved 68 articles, 18 of which concerned JRP. Standard treatment consists of antibiotics for at least 10 days at the acute phase of the disease. All studies demonstrated the diagnostic value of sialendoscopy by visualizing strictures, hypovascularization and whitish intraductal debris. Sialendoscopy is also useful for treatment, by allowing intraductal lavage and, when possible, dilatation of strictures. Lavage is performed with saline solution, hydrocortisone, antibiotics or a combination of these solutions, with no significant differences in terms of efficacy. The mode of administration with or without sialendoscopy also appears to provide similar results. Sialendoscopy appears to be a diagnostic and therapeutic option, although it has not been shown to be more effective than simple lavage. All lavage solutions appear to be effective.
► We propose an impedimetric microbial biosensor for trichloroethylene detection. ► A new transducer modified with carbon nanotubes and
Pseudomonas putida is evaluated. ► Functionalization steps are ...controlled by impedance spectroscopy and AFM. ► The biosensor offers good sensitivity, selectivity, linear range and stability. ► The biosensor is successfully applied to spiked natural water samples.
Contamination of soils and groundwaters with persistent organic pollutants is a matter of increasing concern. The most common organic pollutants are chlorinated hydrocarbons such as perchloroethylene and trichloroethylene (TCE). In this study, we developed a bacterial impedimetric biosensor for TCE detection, based on the immobilization of
Pseudomonas putida F1 strain on gold microelectrodes functionalized with single wall carbon nanotubes covalently linked to anti-
Pseudomonas antibodies. The different steps of microelectrodes functionalization were characterized by electrochemical impedance and atomic force spectroscopies, and analytical performances of the developed microbial biosensor were determined. The impedimetric biosensor response was linear with TCE concentration up to 150
μg
L
−1 and a low limit of detection (20
μg
L
−1) was achieved. No significant loss of signal was observed after 4 weeks of storage at 4
°C in phosphate buffer saline pH 7 (three to four measurements a week). After 5 weeks, 90% of the initial value still remained.
cis-1,2-Dichloroethylene and vinylchloride, the main TCE degradation products, did not significantly interfere with TCE. The microbial sensor was finally applied to the determination of TCE in natural water samples spiked at the 30, 50 and 75
μg
L
−1 levels. Recoveries were very good, ranging from 100 to 103%.
A new conductometric biosensor has been developed for the determination of short chain primary aliphatic alcohols. The biosensor assembly was prepared through immobilization of alcohol oxidase from
...Hansenula sp. and bovine liver catalase in a photoreticulated poly(vinyl alcohol) membrane at the surface of interdigitated microelectrodes. The local conductivity increased rapidly after alcohol addition, reaching steady-state within 10
min. The sensitivity was maximal for methanol (0.394
±
0.004
μS
μM
−1,
n
=
5) and decreased by increasing the alcohol chain length. The response was linear up to 75
μM for methanol, 70
μM for ethanol and 65
μM for 1-propanol and limits of detection were 0.5
μM, 1
μM and 3
μM, respectively (S/N
=
3). No significant loss of the enzyme activities was observed after 3 months of storage at 4
°C in a 20
mM phosphate buffer solution pH 7.2 (two or three measurements per week). After 4 months, 95% of the initial signal still remained. The biosensor response to ethanol was not significantly affected by acetic, lactic, ascorbic, malic, oxalic, citric, tartaric acids or glucose. The bi-enzymatic sensor was successfully applied to the determination of ethanol in different alcoholic beverages.
PDF
