• Environmental Analysis Health and Toxicology
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• v.23 no.2
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• pp.67-77
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• 2008

It has been observed that the linear relationship between the logarithm of bioconcentration factor (log BCF) of highly hydrophobic chemicals and their log $K_{ow}$ breaks when log $K_{ow}$ becomes greater than 6.0. Consequently, super hydrophobic chemicals were not thought to cause baseline toxicity as a single compound. Researchers often call this phenomenon as "hydrophobicity cutoff" meaning that bioconcentration or corresponding baseline toxicity has a certain cutoff at high log $K_{ow}$ value of hydrophobic organic pollutants. The underlying assumption is that the increased molecular size with increasing hydrophobicity prohibits highly hydrophobic compounds from crossing biological membranes. However, there are debates among scientists about mechanisms and at which log $K_{ow}$ this phenomenon occurs. This paper reviews three hypotheses to explain observed "cutoff": steric effects, kinetic or physiological limitations, and chemical activity cutoff. Although the critical molecular size that makes biological membranes not permeable to hydrophobic organic chemicals is uncertain, size effects in combination with kinetic limitation would explain observed non-linearity between log BCF and log $K_{ow}$. Chemical activity of hydrophobic chemicals generally decreases with increasing melting point at their aqueous solubility. Thus, there may be a chemical activity cutoff of baseline toxicity if there is a critical chemical activity over which baseline effects can be observed.

• The Korean Journal of Pesticide Science
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• v.5 no.2
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• pp.33-36
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• 2001

New series of sulfonylureas containing substituted thiophene with 2-chloromethyl-1,3-dioxolane group were prepared, and their herbicidal effects were tested(in vivo) in the upland conditions and in the paddy submerged conditions. The sulfonylureas in which 4,6-dimethoxy- or 4-methyl-6-methoxy group in pyrimidine or triazine ring showed good herbicidal effects at a rate of 0.1 kg/ha. However, they showed weaker herbicidal effects than that of sulfonylureas containing substituted thiophene with 2-fluoromethyl-1,3-dioxolane group in general.

• Journal of the Semiconductor & Display Technology
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• v.6 no.2 s.19
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• pp.35-40
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• 2007

An integrated material removal model considering thermal, chemical and contact mechanical effects in CMP process is proposed. These effects are highly coupled together in the current modeling effort. The contact mechanics is employed in the model incorporated with the heat transfer and chemical reaction mechanisms. The mechanical abrasion actions happening due to the mechanical contacts between the wafer and abrasive particles in the slurry and between the wafer and pad asperities cause friction and consequently generate heats, which mainly acts as the heat source accelerating chemical reaction(s) between the wafer and slurry chemical(s). The proposed model may be a help in understanding multi-physical interactions in CMP process occurring among the wafer, pad and various consumables such as slurry.

• Korean Chemical Engineering Research
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• v.55 no.2
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• pp.275-278
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• 2017

Heterogeneous semiconductor composites have been widely used to establish high-performance microelectronic or optoelectronic devices. During a deposition of silicon atoms on silicon/germanium compound surfaces, germanium (Ge) atoms are segregated from the substrate to the surface and are mixed in incoming a silicon layer. To suppress Ge segregation to obtain the interface sharpness between silicon layers and silicon/germanium composite layers, approaches have used silicon hydride gas species. The hydrogen atoms can play a role of inhibitors of silicon/germanium exchange. However, there are few kinetic models to explain the hydrogen effects. We propose using segregation probability which is affected by hydrogen atoms covering substrate surfaces. We derived the model to predict the segregation probability as well as the profile of Ge fraction through layers by using chemical reactions during silicon deposition.

• Korean Chemical Engineering Research
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• v.53 no.4
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• pp.440-444
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• 2015

Effects of operating variables on the solid circulation rate were investigated in a three-phase circulating fluidized bed, of which inside diameter was 0.102m and height was 3.5m, respectively. Gas velocity, primary and secondary liquid velocities, particle size and height of solid particles piled up in the solid recycle device were chosen as operating variables. The solid circulation rate increased with increasing primary and secondary liquid velocities and height of solid particles piled up in the solid recycle device, but decreased with increasing particle size. The value of solid circulation rate decreased only slightly with increasing gas velocity in the riser. The values of solid circulation rate were well correlated in terms of dimensionless groups within the experimental conditions.

• Safety and Health at Work
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• v.14 no.1
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• pp.17-30
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• 2023

The human reproductive system can be affected by occupational exposure to many physical and chemical risk factors. This study was carried out to review the studies conducted on the issue of the pathophysiological effects of occupational physical and chemical risk factors on the reproductive system of females and males. In this systematic review, the databases such as "Google Scholar," "Pub-Med," "Scopus," and "Web of Science" were used. Following the Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA 2020), the studies included in our study were published between 2000 and 2021. In order to extract the required data, all sections of the articles were reviewed. Out of 57 articles we reviewed, 34 articles were related to field studies and 23 articles to clinical studies. Among them, 43 studies dealt with the pathophysiological effects of chemical agents, six studies dealt with the pathophysiological effects of physical factors, and 8 studies dealt with the pathophysiological effects of physicochemical factors on the human reproductive system. Physical (noise, heat, and radiofrequency radiation) and chemical (such as carbamate and organophosphate pesticides, benzene, toluene, xylene, formaldehyde, NO2, CS2, manganese, lead, nickel, and n-hexane) risk factors had pathophysiological effects on the human reproductive system. The presence of these risk factors in the workplace caused damage to the human reproductive system. The rate of these negative pathophysiological effects can be reduced by performing appropriate managerial, technical, and engineering measures in work environments.

• Carbon letters
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• v.12 no.2
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• pp.107-111
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• 2011

Polyacrylonitrile (PAN) fibers were pre-oxidized in a temperature range of 180-275$^{\circ}C$. The effects of positive and negative stretching on the structure and morphology of PAN fiber in the pre-oxidation process were studied by FTIR spectroscopy, XRD, and SEM. Mechanical property changes were also investigated. No changes in the movement and intensity of functional groups of PAN fibers were caused by positive stretching of up to 10% and negative stretching down to -8%. The crystal structure can be affected by the positive stretching and negative stretching. The maximum strength is 479.81 MPa when the stretching is positive, and the maximum strength is 420.55 MPa when the stretching is negative.

• Bulletin of the Korean Chemical Society
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• v.11 no.6
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• pp.494-496
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• 1990

Catalytic effects of tertiary amines on N-sulfinylation of p-toluenesulfonamide, p-toluidine, and p-toluamide have been investigated by proton NMR studies. Though the catalytic effects were dependent on the substrates, 4-dimethylaminopyridine, pyridine and triethylamine exerted stronger catalytic effects than imidazole and N,N-dimethylaniline. Among the substrates employed, p-toluenesulfonamide turned out to be catalyzed greater than p-toluidine and p-toluamide.

• Archives of Pharmacal Research
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• v.16 no.1
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• pp.6-12
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• 1993

To evaluate KR-10876, a new fluoroquinolone antibacterial agent, its effects on the central nervous system(CNS) were investigated in mmice as part of phamacological study, and the results were compared with those for ciprofloxacin and ofloxacin, two prototypes of quinolone antiabctrial agents. All the parameters indicative of CNS function and acute toxicity were measured by close observation of the animals at regular time intervals after oral treatment of test compounds. KR-10876 did not have any effect on the parameters measured at lower does (100, 300 mg/kg, p.o.), it caused ptosis, suppressed spontaneous locomotor activity, hypothemia, and prolonged hexobarbital-induced sleeping time. KR-10876 also had a slight effect on motor coordination only at high dose. Simialr to ciprofloxacin, KR-10876 did not protect mice from pentylenetetrazol-strychnine-, and electroshock-inducedl convulsions at doses tested. These findings demonstrate that KR-10876 affects CNS functions only at high doses. The rank order for effects is ofloxacin$\le$KR-10876>ciprofloxacin.

• The Journal of Natural Sciences
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• v.4
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• pp.161-177
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• 1991

This experiment was carrid out to investigate the effect of organic fertilizer and plant growth regulators application on the growth and quality of tomato. The results are summarized as follows. 1. Plant height of tomato was recorded highest when chemical fertilizer plus organic fertilizer was applied, and did not have significant effects in number of leaf. But stem diameter was positively effected by chemical plus organic fertilizer application than chemical fertilizer alone. 2. Flower formation, flower weight, anther weight and ovary weight were generally increased by organic fertilizer application. 3. Fruit-set and number of flower were significantly increased by organic fertilizer application. 4. Deformity fruit was the lowest rate at chemical plus organic fertilizer application when it was 14.7 percent, and it was increased by chemical fertilizer application. 5. Days of ripening was slightly delayed by organic fertilizer application and also flowering date shortened by chemical fertilizer application. 6. Plant growth regulators had positive effects on number of flower, flower weight, anther weight, and ovary weight, and variations of their effect by cluster were apparent. 7. Fruit-set was increased by 2,4-D 10ppm and BA 20ppm treatments but was decreased by treatments of Ethephon 10ppm and control. 8. By the BA 20ppm and 2,4-D 10ppm treatments, the rate of deformity fruit was decreased and fruit ripening date was also shortened.