The aim of this study is to control the residual vibrations of a clamped-free beam subjected to a moving load. The dynamic response of the beam is calculated by using the finite element method in order to design a suitable control technique and the numerical results are verified by vibration measurements. All the numerical calculations are performed by a commercial finite element package. Two laser displacement sensors are used to measure the dynamic response of the beam. The moving load is obtained by pressured air directed to the beam via a nozzle, and the movement of the load is achieved by an industrial robot manipulator having 6 degrees of freedom. In this study, the suppression of the residual vibrations that occur after the moving load has left the beam is considered as the main subject. Piezoelectric actuators are used for active vibration control study and displacement feedback is employed. The numerical results agree well with the experimental results. The results show that the finite element method can be used effectively for designing a suitable vibration control strategy.

Toluene, an organic solvent used widely in the industry, is highly lipophilic and accumulates in the cell membrane impeding transport through it. Its metabolites cause oxygen radical formation that react with unsaturated fatty acids and proteins in erythrocytes leading to lipid peroxidation and protein breakdown. In this study, we aimed to investigate the membrane stabilizing and the oxidative stress-inducing effects of toluene in human erythrocytes. Measurements of osmotic fragility, mean corpuscular volume (MCV), oxidative stress parameters and antioxidant enzyme activities were performed simultaneously both in individuals exposed to toluene professionally (in vivo) and human erythrocytes treated with toluene (in vitro). To measure osmotic fragility, erythrocytes were placed in NaCl solutions at various concentrations (0.1% [blank], 0.38%, 0.40%, 0.42%, 0.44%, 0.46%, 0.48% and 1% [stock]). Percentage of haemolysis in each solution was calculated with respect to the 100% haemolysis in the blank solution. The erythrocyte packs prepared at the day of the above-mentioned measurements were kept at -80 degrees C until the time for determination of malonyldialdehyde and protein carbonyl levels, and catalase (CAT) and glutathione peroxidase activities as indicators of oxidative stress. Toluene increased oxidative stress parameters significantly both in vivo and in vitro; it also caused a significant decrease in the activities of antioxidant enzymes. Osmotic fragility was altered only in the case of in vitro exposure. In conclusion, toluene exposure resulted in increased lipid peroxidation and protein damage both in vivo and in vitro. Although, it is natural to expect increased osmotic fragility due to oxidative properties of toluene, its membrane-stabilizing effect overcame the oxidative properties leading to decreased osmotic fragility or preventing its deterioration in vitro and in vivo toluene exposures, respectively, in the present study.

Isotretinoin is widely used in the treatment of extensive and nodulocystic acne. The objective of this prospective study was to investigate whether oral isotretinoin could affect the hearing system. Thirty-eight patients with acne vulgaris (76 ears) who were diagnosed and treated at the Department of Dermatology were included in the current study. Study evaluation visits were performed at baseline and at Weeks 1, 2 and 3. Pure-tone averages (PTAs) of air conduction thresholds at 250 Hz (PTA1); 500, 1000, and 2000 Hz (PTA2); 4000, 8000, and 10,000 Hz (PTA3); and 12,500, 16,000, 18,000 and 20,000 Hz (PTA4) for each ear were calculated separately. Assessment of the efficacy was based on the audiometric findings. Compared with pre-treatment evaluation, the PTAs of patients were found to be significantly different at the first week for PTA2 (P = 0.033) and PTA3 (P = 0.001), at the second week for PTA1 (P = 0.036), and at the third week for PTA4 (P = 0.002). Our results suggest that the oral isotretinoin (13-cis retinoic acid), which is a derivative of retinol (vitamin A), improved the hearing level of the patients in all audiometric frequencies in a short-period follow-up.

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Reactive oxygen and nitrogen species have been implicated in the pathogenesis of noise-induced hearing loss. In this case-control study, we investigated the oxidative and antioxidative status of erythrocytes from workers in noisy workplace. Blood samples of 127 workers in noisy workplace (WNW) and 117 workers in non-noisy workplace (WNNW) from the same company were taken into tubes with potassium EDTA as anticoagulant in order to obtain hemolysate. Total superoxide dismutase (SOD) and catalase (CAT) activities as the enzymes of antioxidative defense mechanism in the erythrocytes together with malondialdehyde (MDA) as the lipid peroxidation index and total nitric oxide (NO) as an index for nitrogen species analyses were performed by spectrophotometric methods. SOD activity was found to be 450.0±106.4 U/g Hb in WNW and 443.1±83.1 U/g Hb in WNNW. The difference between two groups were not statistically significant (p= 0.582). CAT activity was found to be 426.0±98.0 k/g Hb in WNW and 432.6±109.0 k/g Hb in WNNW showing statistically insignificant difference (p= 0.621). MDA levels in erythrocytes from WNW was significantly higher than WNNW (39.28±10.22 nmol/g Hb and 32.51±10.73 nmol/g Hb, respectively and p= 0.0001). On the other hand, NO levels were found to be significantly reduced in WNW (0.275±0.187 µmol/g Hb) compared to WNNW (0.382±0.284 µmol/g Hb) (p= 0.001). When we analyzed the hematological parameters, all the cell counts increased in WNW except monocytes and platelets compared to WNNW (p= 0.0001). Related to this changes, hemoglobin, MCHC, and hematocrit also increased in WNW (p= 0.0001). The oxidative stress, which is possibly propagated by the physical environment, seems to have an important pathophysiological role in hearing loss and lipid peroxidative cellular changes in all of the workers who work in noisy occupations.Key words: Noise, Worker, Oxidative stress, Superoxide dismutase, Catalase, Malondialdehyde, Nitric oxide ÖZET Gürültünün ‹nsan Eritrositlerindeki Oksidan ve Antioksidan Dengeye EtkileriReaktif oksijen ve nitrojen türleri, yüksek ses kaynakl› duyma kay›plar›nda önemli bir patolojik faktör olarak kabul görmekte-dir. Bu vaka kontrollü çal›flmam›zda yüksek sesli ortamlarda çal›flan iflçilerin eritrositlerinde oksidan ve antioksidan dengeyi araflt›rd›k. Yüksek sesli ortamda çal›flan (YSOÇ) 127 iflçi ile normal ortamda çal›flan (NOÇ) 117 iflçinin kanlar› hemolizat elde etmek üzere içinde antikoagulan olarak potasyum EDTA bulunan tüplere al›nd›.