Synthesis-chracteristics and sintering behavior of PZT-powder

Kemal Köseo lu 한양대학교 세라믹연구소 2007 Journal of Ceramic Processing Research Vol.8 No.1

In the Pb(Zr0,525Ti0,475)O3 system, two powders were produced by chemical co-precipitation and mechanical mixing of Pb(NO3)2, Zr(OC3H7)4 and Ti(OC3H7)4. The powders were characterized with regard to their specific surface area, particle size distribution, phases present and the pore size distribution of the pressed powder tablets. The co-precipitated powder was sintered already at 750 °C to 99% of its theoretical density. The mechanically-mixed powders reached only 62.5% of the theoretical density at 900 °C sintering temperature, although they had a higher specific surface area and finer particle size than the co-precipitated powder. The better sintering behavior of the co-precipitated powder can be explained by a narrow pore size distribution and small pore size in its pressed powder tablets. This is further proof that a determination of the pore size distribution of pressed powder tablets gives reliable indications about the sintering behavior. In the Pb(Zr0,525Ti0,475)O3 system, two powders were produced by chemical co-precipitation and mechanical mixing of Pb(NO3)2, Zr(OC3H7)4 and Ti(OC3H7)4. The powders were characterized with regard to their specific surface area, particle size distribution, phases present and the pore size distribution of the pressed powder tablets. The co-precipitated powder was sintered already at 750 °C to 99% of its theoretical density. The mechanically-mixed powders reached only 62.5% of the theoretical density at 900 °C sintering temperature, although they had a higher specific surface area and finer particle size than the co-precipitated powder. The better sintering behavior of the co-precipitated powder can be explained by a narrow pore size distribution and small pore size in its pressed powder tablets. This is further proof that a determination of the pore size distribution of pressed powder tablets gives reliable indications about the sintering behavior.

Headache related to mask use of healthcare workers in COVID-19 pandemic

( Cansu Köseoğlu Toksoy ),( Hayri Demirbaş ),( Erhan Bozkurt ),( Hakan Acar ),( Ülkü Türk Börü ) 대한통증학회 2021 The Korean Journal of Pain Vol.34 No.2

Background: It has been reported that a new type of headache may develop as a result of face mask use during the COVID-19 pandemic. The aim of this study is to investigate the clinical features of face mask-related headache during the COVID-19 pandemic. Methods: This is a cross-sectional study carried out on healthcare workers at the Afyonkarahisar Health Sciences University. The number of workers at our university was established. Sample size was calculated using the G*Power program. A questionnaire consisting of questions relating to pre-existing headache, an aggravation in headache, and de-novo headache was filled out by 3 neurologists with all participants. Results: Data was collected from a total of 375 participants, after the exclusion of 5 individuals who refused to participate. Out of all participants, 26 (6.9%) used a filtering mask, 274 (73.1%) used a surgical mask, 75 (20.0%) participants used a combination of both masks. The number of participants with preexisting headache was 114 (30.4%) had pre-existing headache. Of those with pre-existing headache, 77 (67.5%) healthcare workers had reported an aggravation in their headache after mask use. De-novo headache was observed in 116 (30.9%) of participants. De-novo headache characteristics included throbbing in 17 (14.7%) participants and pressing in 99 (85.3%) participants. In addition, symptoms such as tachypnea, sleep disturbance, and fatigue were found to be significantly higher. Conclusions: This study indicates that healthcare workers develop headaches due to use of masks during the COVID-19 outbreak.

The Effects of Etodolac, Nimesulid and Naproxen Sodium on the Frequency of Sister Chromatid Exchange after Enclused Third Molars Surgery

Banu Gürkan Köseoğlu,Hülya Koçak,Şükrü Öztürk,Şükrü Palanduz,Kıvanç Çefle 연세대학교의과대학 2008 Yonsei medical journal Vol.49 No.5

Purpose: Non-steroidal anti-inflammatory drugs (NSAID) are frequently used in oral surgical procedures in dentistry. The evaluation of the frequency of sister chromatid exchange (SCE) is accepted as a reliable cytogenetic method to assess the genotoxic effects of environmental factors. Materials and Methods: In this study, the genotoxic effects of various NSAIDs were assessed in 30 patients to who they were administered following encluosed third molar surgery using SCE analysis before and after the operation. The frequency of SCE was evaluated before the operation and after 3 days of etodolac, nimesulid and naproxen use. Results: There was no statistically significant difference in the frequency of SCE between the preoperative and postoperative states in patients given etodolac, nimesulid or naproxen sodium. Conclusion: Short term use of selective and non-selective NSAIDs was not associated with a significant genotoxic effect that could be detected using the SCE method in peripheric lymphocytes.

IDENTIFICATION CAMPAIGN OF SUPERNOVA REMNANT CANDIDATES IN THE MILKY WAY. I.<i>CHANDRA</i>OBSERVATION OF G308.3-1.4

Hui, C. Y.,Seo, K. A.,Huang, R. H. H.,Trepl, L.,Woo, Y. J.,Lu, T.-N.,Kong, A. K. H.,Walter, F. M. IOP Publishing 2012 The Astrophysical journal Vol.750 No.1

<P>ROSAT all-sky survey data have provided another window in which to search for supernova remnants (SNRs). In re-examining this data archive, a list of unidentified extended X-ray objects have been suggested as promising SNR candidates. However, most of these targets have not yet been fully explored by state-of-the-art X-ray observatories. To select a pilot target for a long-term identification campaign, we observed the brightest candidate, G308.3-1.4, with the Chandra X-ray Observatory. An incomplete shell-like X-ray structure that is well correlated with the radio shell emission at 843 MHz has been revealed. The X-ray spectrum suggests the presence of a shock-heated plasma. All these evidences confirm G308.3-1.4 as an SNR. The brightest X-ray point source detected in this field of view is also the one located closest to the geometrical center of G308.3-1.4, which has a soft spectrum. The intriguing temporal variability and the identification of the optical/infrared counterpart rule out the possibility of an isolated neutron star. On the other hand, the spectral energy distribution from the K-s band to the R band suggests a late-type star. Together with a putative periodicity of similar to 1.4 hr, the interesting excesses in the V and B bands and in H alpha suggest that this source is a promising candidate for a compact binary that survived a supernova explosion.</P>

Prevalence of Multiple Sclerosis in a Turkish City Bordering an Iron and Steel Factory

Ülkü Türk Börü,Adnan Burak Bilgiç,Cansu Köseoğlu Toksoy,Abdullah Yasir Yılmaz,Mustafa Tasdemir,Nilay Padir Sensöz,Özgür Öztop Çakmak,Arda Duman,Cem Bölük 대한신경과학회 2018 Journal of Clinical Neurology Vol.14 No.2

Background and Purpose Multiple sclerosis (MS) is an autoimmune disease characterizedby inflammatory demyelination. Recent studies have shown that long-term exposure to air pollutants(including PM10 particulates) is potentially an environmental risk factor for MS. Weaimed to determine the prevalence rates of MS in two cities with different levels of air pollution. Methods This door-to-door population-based study was conducted between April 2014 andJune 2015. Two cities were screened for the prevalence rates of MS: 1) Karabük, which bordersan iron-and-steel factory, and 2) Akçakoca, which is a coastal city located in the same region. A validated survey form was used for screening MS. The 2010 McDonald Criteria were usedfor diagnosing MS. The patients were examined twice, first by a neurology assistant in the fieldand then by a senior neurologist in public health centers in the cities. Results The prevalence of MS was 95.9/100,000 in Karabük and 46.1/100,000 in Akçakoca. Intotal, 33 patients were diagnosed with clinically definite MS. The female/male ratio was 1.5, and21 patients were diagnosed with relapsing-remitting MS, 9 with secondary progressive MS, and3 with primary progressive MS. Conclusions We found that the prevalence of MS was more than two fold higher in Karabükthan in Akçakoca, which supports a link between air pollution and the pathogenesis of MS. However, larger etiological and epidemiological studies are needed to confirm this hypothesis.

Endovascular Treatment of a Giant Aneurysm of the Aberrant Right Hepatic Artery in a Patient with Osler-Weber-Rendu Syndrome: A Case Report

Mehmet Burak Çildağ,Mustafa Gök,Tuğba Öztürk,Ömer Faruk Kutsi Köseoğlu 대한혈관외과학회 2023 Vascular Specialist International Vol.39 No.3

Osler-Weber-Rendu syndrome (OWR) is an autosomal dominant disorder characterized by recurrent epistaxis, mucocutaneous or visceral telangiectasias, and arteriovenous malformations in the lungs, liver, brain, and gastrointestinal tract. Hepatic artery aneurysms (HAAs) can also occur in OWR patients. HAAs are the second most common type of visceral artery aneurysm, and mortality rates are high owing to the lack of a tamponade effect. Anatomical variations of the celiacomesenteric vasculature are common, and the most common variation is that of the right hepatic artery originating from the superior mesenteric artery (SMA). We present the endovascular treatment of a patient with OWR and an aberrant right HAA originating from the SMA, with coil embolization and stent grafting. Giant HAAs can be treated endovascularly. However, stent graft placement should be reconsidered because of the need for antithrombotic medication, which may increase the incidence of epistaxis attacks in that patient group.