Dynamic response of a Timoshenko beam on a tensionless Pasternak foundation

Coskun, Irfan,Engin, Hasan,Tekin, Ayfer Techno-Press 2011 Structural Engineering and Mechanics, An Int'l Jou Vol.37 No.5

The dynamic response of a Timoshenko beam on a tensionless Pasternak foundation is investigated by assuming that the beam is subjected to a concentrated harmonic load at its middle. This action results in the creation of lift-off regions between the beam and the foundation that effect the character of the response. Although small displacements for the beam and the foundation are assumed, the problem becomes nonlinear since the contact/lift-off regions are not known at the outset. The governing equations of the beam, which are coupled in deflection and rotation, are obtained in both the contact and lift-off regions. After removing the coupling, the essentials of the problem (the contact regions) are determined by using an analytical-numerical method. The results are presented in figures to demonstrate the effects of some parameters on the extent of the contact lengths and displacements. The results are also compared with those of Bernoulli-Euler, shear, and Rayleigh beams. It is observed that the solution is not unique; for a fixed value of the frequency parameter, more than one solution (contact length) exists. The contact length of the beam increases with the increase of the frequency and rotary-inertia parameters, whereas it decreases with increasing shear foundation parameter.

Knowledge about Cervical Cancer Risk Factors and Pap Smear Testing Behavior among Female Primary Health Care Workers: A Study from South Turkey

Coskun, Savas,Can, Huseyin,Turan, Sercan Asian Pacific Journal of Cancer Prevention 2013 Asian Pacific journal of cancer prevention Vol.14 No.11

Background: Cervical cancer is one of the ten most frequent cancers in Turkey. We here examined knowledge about cervical cancer in relation to Papanicolaou (Pap) testing among female primary health care workers in Hatay, a city is located in the south of Turkey. Materials and Methods: The study was completed on 261 women healthcare workers who were or had been sexually active and who accepted to participate to the study. The participants gave verbal informed consent and thereafter questionnaires prepared by the investigators were administered by personal interview. Results: Only 30.3% (n=79) of the participants regularly had a gynecologic examination. While 87.4% (n=228) of the participants reported that they had already heard about the Pap smear test, only 45.2% (n=118) had undergone this test. It was determined that had undergone an average of $1.66{\pm}0.89$ times (1-4) within the last five years. Some 56.0% (n=117) of the participants were well informed about the Pap smear test (p<0,001) and 81.1% (n=63) of the participants who regularly had gynecological examinations (p<0,001) had this test. Conclusions: For the early diagnosis of the cervical cancer, regularly having a Pap smear test is crucial. Healthcare workers should also demonstrate sensitivity about this issue. We think that the importance of the issue should be re-highlighted by organizing in-service training for female primary healthcare workers. Studies are warranted to determine the psychosociological factors that cause individuals to not have the test.

High hopes: can molecular electronics realise its potential?

Coskun, Ali,Spruell, Jason M.,Barin, Gokhan,Dichtel, William R.,Flood, Amar H.,Botros, Youssry Y.,Stoddart, J. Fraser The Royal Society of Chemistry 2012 Chemical Society reviews Vol.41 No.14

<P>Manipulating and controlling the self-organisation of small collections of molecules, as an alternative to investigating individual molecules, has motivated researchers bent on processing and storing information in molecular electronic devices (MEDs). Although numerous ingenious examples of single-molecule devices have provided fundamental insights into their molecular electronic properties, MEDs incorporating hundreds to thousands of molecules trapped between wires in two-dimensional arrays within crossbar architectures offer a glimmer of hope for molecular memory applications. In this critical review, we focus attention on the collective behaviour of switchable mechanically interlocked molecules (MIMs)—specifically, bistable rotaxanes and catenanes—which exhibit reset lifetimes between their ON and OFF states ranging from seconds in solution to hours in crossbar devices. When these switchable MIMs are introduced into high viscosity polymer matrices, or self-assembled as monolayers onto metal surfaces, both in the form of nanoparticles and flat electrodes, or organised as tightly packed islands of hundreds and thousands of molecules sandwiched between two electrodes, the thermodynamics which characterise their switching remain approximately constant while the kinetics associated with their reset follow an intuitively predictable trend—that is, fast when they are free in solution and sluggish when they are constrained within closely packed monolayers. The importance of seamless interactions and constant feedback between the makers, the measurers and the modellers in establishing the structure-property relationships in these integrated functioning systems cannot be stressed enough as rationalising the many different factors that impact device performance becomes more and more demanding. The choice of electrodes, as well as the self-organised superstructures of the monolayers of switchable MIMs employed in the molecular switch tunnel junctions (MSTJs) associated with the crossbars of these MEDs, have a profound influence on device operation and performance. It is now clear, after much investigation, that a distinction should be drawn between two types of switching that can be elicited from MSTJs. One affords small ON/OFF ratios and is a direct consequence of the switching in bistable MIMs that leads to a relatively small remnant molecular signature—an activated chemical process. The other leads to a very much larger signature and ON/OFF ratios resulting from physical or chemical changes in the electrodes themselves. Control experiments with various compounds, including degenerate catenanes and free dumbbells, which cannot and do not switch, are crucial in establishing the authenticity of the small ON/OFF ratios and remnant molecular signatures produced by bistable MIMs. Moreover, experiments conducted on monolayers in MSTJs of molecules designed to switch and molecules designed not to switch have been probed directly by spectroscopic and other means in support of MEDs that store information through switching collections of bistable MIMs contained in arrays of MSTJs. In the quest for the next generation of MEDs, it is likely that monolayers of bistable MIMs will be replaced by robust crystalline extended structures wherein the switchable components, derived from bistable MIMs, are organised precisely in a periodic manner.</P> <P>Graphic Abstract</P><P>There is a world of difference between a molecular electronic device which switches at high (blue) rather than at low (red) bias. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c2cs35053j'> </P>

Response of a finite beam on a tensionless Pasternak foundation under symmetric and asymmetric loading

Coskun, Irfan,Engin, Hasan,Ozmutlu, Aydin Techno-Press 2008 Structural Engineering and Mechanics, An Int'l Jou Vol.30 No.1

The static response of a finite beam resting on a tensionless Pasternak foundation and subjected to a concentrated vertical load is assessed in this study. The concentrated vertical load may be applied at the center of the beam, or it may be offset from the center. The tensionless character of the foundation results in the creation of lift-off regions between the beam and the foundation. An analytical/ numerical solution is obtained from the governing equations of the contact and lift-off regions to determine the extent of the contact region. Although there is no nonlinear term in the equations, the problem shows a nonlinear character since the contact region is not known in advance. Due to that nonlinearity, the essentials of the problem (the coordinates of the lift-off points) are calculated numerically using the Newton-Raphson technique. The numerical results are presented in figures to illustrate the behaviours of the free-free and pinned-pinned beams under symmetric or asymmetric loading. The figures illustrate the effects of the shear foundation parameter and the symmetric and asymmetric loading options on the variation of the contact lengths and the displacement of the beam.

Dynamic contact response of a finite beam on a tensionless Pasternak foundation under symmetric and asymmetric loading

Coskun, Irfan Techno-Press 2010 Structural Engineering and Mechanics, An Int'l Jou Vol.34 No.3

The dynamic response of a finite Bernoulli-Euler beam resting on a tensionless Pasternak foundation and subjected to a concentrated harmonic load is investigated in this study. This load may be applied at the center of the beam, or it may be offset from the center. Since the elastic foundation is assumed to be tensionless, the beam may lift off the foundation, resulting in contact and non-contact regions in the system. An analytical/numerical solution is obtained from the governing equations of the contact and non-contact regions to determine the coordinates of the lift-off points. Although there is no nonlinear term in the equations, the problem appears to be nonlinear since the contact regions are not known in advance. Due to that nonlinearity, the essentials of the problem (the coordinates of the lift-off points) are calculated numerically using the Newton-Raphson technique. The results, which represent the symmetric and asymmetric responses of the beam, are presented graphically in this work. They illustrate the effects of the forcing frequency and the beam length on the extent of the contact regions and displacements.

Bias in Laboratory Medicine: The Dark Side of the Moon

Coskun Abdurrahman 대한진단검사의학회 2024 Annals of Laboratory Medicine Vol.44 No.1

Physicians increasingly use laboratory-produced information for disease diagnosis, patient monitoring, treatment planning, and evaluations of treatment effectiveness. Bias is the systematic deviation of laboratory test results from the actual value, which can cause misdiagnosis or misestimation of disease prognosis and increase healthcare costs. Properly estimating and treating bias can help to reduce laboratory errors, improve patient safety, and considerably reduce healthcare costs. A bias that is statistically and medically significant should be eliminated or corrected. In this review, the theoretical aspects of bias based on metrological, statistical, laboratory, and biological variation principles are discussed. These principles are then applied to laboratory and diagnostic medicine for practical use from clinical perspectives.

Free Fatty Acid Accumulation by Mesophilic Lactic Acid Bacteria in Cold-Stored Milk

Coskun, Hayri,Ondul, Eda The Microbiological Society of Korea 2004 The journal of microbiology Vol.42 No.2

This study was aimed to determine the accumulation of free fatty acid by mesophilic lactic acid bac-teria (Lactococcus lactis subsp. lactis 1471, Lactococcus lactis subsp. cremoris 1000 and Lactobacillus casei 111) in cold-stored milk. According to the results, all cold-stored milks had higher acid degree val-ues than those of fresh milk. This phenomenon showed that a slight increase occurred in the accumulation of free fatty acids as a result of spontaneous lipolysis during cold storage. All lactic acid bacteria showed good performance in production of titratable acidity, which increased during fermentation of the milk (fresh and stored milks). Moreover, as the storage time was prolonged, more free fatty acid accumulation was obtained from the fermentation of the cold-stored milk by the investigated lactic acid bacteria. The control milk, which was without lactic acid bacteria, showed no change in the accumulation of free fatty acid during fermentation. From this result, it can be suggested that longer cold-storage time can induce higher free fatty acid accumulation in milk by lactic acid bacteria.

Dynamic response of a Timoshenko beam on a tensionless Pasternak foundation

Irfan Coskun,Hasan Engin,Ayfer Tekin 국제구조공학회 2011 Structural Engineering and Mechanics, An Int'l Jou Vol.37 No.5

The dynamic response of a Timoshenko beam on a tensionless Pasternak foundation is investigated by assuming that the beam is subjected to a concentrated harmonic load at its middle. This action results in the creation of lift-off regions between the beam and the foundation that effect the character of the response. Although small displacements for the beam and the foundation are assumed, the problem becomes nonlinear since the contact/lift-off regions are not known at the outset. The governing equations of the beam, which are coupled in deflection and rotation, are obtained in both the contact and lift-off regions. After removing the coupling, the essentials of the problem (the contact regions) are determined by using an analytical-numerical method. The results are presented in figures to demonstrate the effects of some parameters on the extent of the contact lengths and displacements. The results are also compared with those of Bernoulli-Euler, shear, and Rayleigh beams. It is observed that the solution is not unique; for a fixed value of the frequency parameter, more than one solution (contact length) exists. The contact length of the beam increases with the increase of the frequency and rotary-inertia parameters, whereas it decreases with increasing shear foundation parameter.

Lipoleiomyoma of broad ligament mimicking ovarian cancer in a postmenopausal patient: case report and literature review

Mehmet Coskun Salman,Alp Usubutun,Kunter Yuce,Zeliha Atak 대한부인종양학회 2010 Journal of Gynecologic Oncology Vol.21 No.1

Lipoleiomyoma is a very rare tumor which is composed of adipocytes and smooth muscle cells. It is most commonly located in uterine corpus although cervical, ovarian, and retroperitoneal locations were also reported. Lipoleiomyoma located in broad ligament is extremely uncommon and only five cases were reported to date. Here, we report the sixth case of lipoleiomyoma of broad ligament which was diagnosed in a postmenopausal woman who was subjected to exploratory laparotomy with a preoperative diagnosis of a solid adnexal mass suggesting an ovarian malignancy.

The impact of the COVID-19 pandemic on science editing

Ilke Coskun Benlidayi 한국과학학술지편집인협의회 2021 Science Editing Vol.8 No.1

No abstract