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Biomedical subjects

A Apostol

Publications and source records attributed to A Apostol.

13 recordsLinked to original sources
PubMed2005

Non-Gaussian statistics of optical near-fields.

Optical fields in the proximity of random media can be modeled as a superposition of waves with random phases. We demonstrate that, depending on the experimental geometry, both Gaussian and non-Gaussian regimes can be established for the statistics of scattered intensity. In a reflection-emission configuration, the first-order statistics of the scattered light is non-Gaussian and it can be used to retrieve information about the physical interface.

Journal Article↗
PubMed2004

Light spectra in the near field of random media.

The spectrum of light in close proximity to a highly scattering, randomly inhomogeneous medium is investigated. We find differences between the far- and near-field spectra that are due to evanescent wave contributions. We show that these spectral modifications depend on the coherence properties of an equivalent planar source, which, in turn, relates to the statistical characteristics of the interface.

Journal Article↗
PubMed2003

Spatial correlations in the near field of random media.

The conventional coherence theory suggests that the fields radiated by statistically homogeneous sources correlate over spatial regions of the order of the wavelength irrespective of the distance from the surface of the source. Contrary to these predictions, we show that the spatial correlations of optical fields in close proximity of highly scattering, randomly inhomogeneous media depend on this distance and, moreover, their extent can be significantly smaller than the wavelength. The contribution of evanescent fields is experimentally demonstrated and the coherence length in the near field is shown to relate to the coherence properties at the surface which are, in turn, determined by the structural characteristics of the random media.

Journal Article↗
PubMed2003

Coherence properties near interfaces of random media.

The spatial coherence theory of optical fields radiated by statistically homogeneous, infinite, planar sources does not account for detailed surface characteristics. However, coherence properties change with the angular distribution of the intensity radiated from such a source, which, in turn, depends on the physical properties of the sample. We show that second-order correlations of the optical field measured at several wavelengths away from the surface of a highly inhomogeneous medium relate to the statistical characteristics of the interface.

Journal Article↗
PubMed1999

Detection of low dose radiation induced DNA damage using temperature differential fluorescence assay.

A rapid and sensitive fluorescence assay for radiation-induced DNA damage is reported. Changes in temperature-induced strand separation in both calf thymus DNA and plasmid DNA (puc 19 plasmid from Escherichia coli) were measured after exposure to low doses of radiation. Exposures of between 0.004 and 1 Gy were measured with doses as low as 0.008 Gy yielding significant responses. The double-strand, sensitive dye PicoGreen was used as an indicator of DNA denaturation. Calibration plots indicate that fluorescence changes corresponding to amounts as low as 1 ng of double stranded DNA (10(6) copies for plasmid puc 19) are detected by this method.

Animals↗
PubMed1999

Mercury contamination associated with artisanal gold mining on the island of Mindanao, the Philippines.

The Agusan River basin of eastern Mindanao, the Philippines, hosts several centres of artisanal gold mining, the most important of which, Diwalwal, is a significant gold producer in global terms. An investigation of the environmental impacts of artisanal mining in the Agusan system, with particular reference to mercury contamination, was initiated in 1995 following reports of several incidents of human Hg poisoning in the province of Davao del Norte. Results show drainage downstream of Diwalwal is characterised by extremely high levels of Hg both in solution (maximum 2906 micrograms/l) and in bottom sediments (> 20 mg/kg). Filtered surface water Hg levels exceed the WHO Drinking Water guideline and the US-EPA Water Quality Criteria for the Protection of Aquatic Life for a downstream distance of more than 14 km, including channel sections utilised for fishing and potable water supply. The Environment Canada sediment quality Hg Toxic Effect Threshold for the Protection of Aquatic Life is exceeded for a downstream distance of 20 km. Hair Hg data indicate that ballmill and CIP plant operators processing Hg contaminated tailings at eastern Mindanao's principal gold beneficiation centre, Apokon, may be subject to enhanced occupational Hg exposure. It appears that the wider population of this area has not been affected.

Geologic Sediments↗
PubMed1987

Density of TEPC-15 plasmacytoma cells as function of size.

TEPC-15 plasmacytoma cells were observed under the microscope, as they sedimented at 1 G in Dulbecco's modified Eagle's medium. A mean density of 1.0422 g/cm3 (30 degrees C) was found. The density difference of smaller cells (15 micron diameter) was significantly higher than the density difference of larger cells (25 micron diameter). The ratio in density difference was close to 3.

Animals↗
PubMed1976

An assay for selecting high risk population for gastric cancer by studying environmental factors.

Gastric cancer mortality incidence data registered in two different areas of Eastern Transylvania (Roumania) were reported related to 325,000 inhabitants from the period of 1951-1972. The findings were compared to some geographical environmental factors deriving from an area of 13,300 km with 905,700 inhabitants. A 2-3.5 times larger incidence of gastric cancer (75-140 per 100,000/year) was found in some selected geographical areas of the intermontane depressions of Gheorgheni and Ciuc in comparison to hilly area of Transylvanian Tableland. The difference might be explained by some unknown environmental gastric cancer risk factors. Of the natural factors, the presence of magmatic substrata shows a significant degree of correlation. The main pedological factor seems to be badly drained pseudoglyied podzolic and peaty soils of low pH and high content of organic matter. Sofs drinking waters also may be involved as risk factor. High altitude, cold climate determining a restricted assortiment of cultivated plants, the successive production of vegetal and animal food on the same soil for livelong periods and several generations, especially in isolated rural areas, seem to represent gastric cancer risk factors. According to authors' opinion a survey of the high-risk population selected on the basis of the environmental factors, especially of the persons suffering from gastric disorders considered today possible precursors of gastric cancer, may offer some progress in detecting early gastric malignancy in the future.

Climate↗
PubMedDate not supplied

[Cefepime (maxipime), large spectrum 4th generation cephalosporin, resistant to beta-lactamases].

As a result of the appearance of bacterial strains resistant to 3rd generation cephlosporin, since 1993 cephalosporins of 4th generation have been developed and introduced in therapy; among them are: cefepime and cefpirome. Cefepime is the most active 4th generation cephalosporin possessing the following advantages over the 3rd generation cephalosporins: high intrinsic potency due to rapid penetration into the periplasmic space; an extended spectrum of activity that includes many Gram-positive and Gram-negative organisms; Activity against multi-resistant Gram-negative bacteria, including Enterobacter and Klebsiella species; Low potential for beta-lactamase induction, especially Bush group 1 beta-lactamases, even ar low periplasmic concentrations; Minimal selection of resistant mutant strains. Its spectrum is very large being very active against Gram-negative bacilii: Enterobacter, Pseudomonas aeruginosa, Klebsiella pneumoniae, Serratia, Citrobacter, Proteus mirabilis and less active against Bacillus fragillis. Cefepime is also very active against Gram-positive cocci: Staphylococcus aureus (methicillin-susceptible strains only), Streptococcus pneumoniae, Streptococcus pyogenes. Some of the methicillin-resistant strains of staphylococcus are susceptible to cefepime; Enterococcus is resistant. Due to its high resistance against beta-lactamases Cefepime (Maxipime) is the best choice in life threatening nosocomial infections occuring in patients in the intensive care units. Cefepime can be synergically associated with aminoglycosides and fluoroquinolones.

Anti-Bacterial Agents↗