Experimental and analytical investigation on mechanics of metal cutting including edge forces

Almost every field of industry requires machining in their processes. Products are mass manufactured from a sequence of machining operations in certain amount of time. In this material removal processes metal cutting is the most common one. The main purpose is to shape metals and alloys by using chip formation operations and any improvement in the cycle time will reduce the total cost significantly. Therefore, modeling of the machining operations such as turning and milling is very important in terms of process effectiveness. In accordance with the technological developments and computer integration, the modeling of the metal cutting processes becomes easier. Depending on the application, machining type may differ; however the basic principles remain the same. In this respect, mechanics and the dynamics of the orthogonal cutting model provide invaluable insight regarding the selection of process parameters. In this thesis, the mechanics of orthogonal and oblique cutting is reviewed using analytical and experimental methods for different materials and process conditions. The results are used in mechanistic modeling of the cutting forces and predicted cutting forces are compared with the experimental results. As an important part of the experimental work, edge forces are also analyzed empirically. The effect of hone radius on the cutting process is investigated, and taken into account in force predictions using an analytical model proposed by Ozlu [20], and promising results are obtained and verified by experiments

Estimated probabilities of positive, vs. negative, events show separable correlations with covid-19 preventive behaviours

Research has associated optimism with better health-protective behaviours, but few studies have measured optimism or pessimism directly, by asking participants to estimate probabilities of events. We used these probability estimates to examine how optimism and/or pessimism relate to protecting oneself from COVID-19. When COVID-19 first reached Turkey, we asked a snowball sample of 494 Istanbul adults how much they engaged in various COVID-protective behaviours. They also estimated the probabilities of their catching COVID-19, and of other positive and negative events happening to them. Estimated probability of general positive events (optimism) correlated positively with officially-recommended helpful behaviours (e.g. wearing masks), but not with less-helpful behaviours (e.g. sharing ‘alternative’ COVID-related information online). Estimated probabilities of general negative events (pessimism), or of catching COVID, did not correlate significantly with helpful COVID-related behaviours; but they did correlate with psychopathological symptoms, as did less-helpful COVID-related behaviours. This shows important nuances can be revealed by measuring optimism and pessimism, as separate variables, using probability estimates.WOS:000766608100006Scopus - Affiliation ID: 60105072PMID: 35228768Social Sciences Citation IndexQ2ArticleUluslararası işbirliği ile yapılan - EVETMarch2022YÖK - 2021-22Hazira

Enhanced Light-Driven Antimicrobial Activity of Cationic Poly (oxanorbornene) s by Phthalocyanine Incorporation into Polymer as Pendants

Amphiphilic poly(oxanorbornene)s are promising synthetic polymers that mimic the structural properties and antimicrobial functions of naturally occurring antimicrobial peptides. Here, poly(oxanorbornene)s bearing pendant zinc(II) phthalocyanine and triphenyl(ethyl) phosphonium functionalities are synthesized by ring-opening metathesis polymerization (ROMP). Fluorescence, singlet oxygen and triplet quantum yields of polymers are measured in dimethyl sulfoxide and aqueous medium. The singlet oxygen quantum yields of copolymers with the highest triphenyl and triethyl phosphonium content are found to be 0.29 and 0.41, respectively. Then, antimicrobial activities of polymers against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) are investigated under both dark and light conditions. Synergistic effect of zinc(II) phthalocyanine and phosphonium-containing poly(oxanorbornene) is observed that the conjugate possessing the most triphenyl phosphonium side chains has the highest activity under light against both gram-positive and gram-negative bacterial strains after 80 min irradiation, reducing the survival of E. coli or S. aureus by 99.9999%. Hemolytic concentrations of the copolymers are found between 8 and 512 µg mL−1. Scanning electron microscopy (SEM) proves that the bacteria membrane deforms after contacting with the biocidal polymer

3D Propolis-Sodium Alginate Scaffolds: Influence on Structural Parameters, Release Mechanisms, Cell Cytotoxicity and Antibacterial Activity

FEN-C-YLP-130319-0065 BAPKO Project. UID/CTM/50025/2019In this study, the main aim was to fabricate propolis (Ps)-containing wound dressing patches using 3D printing technology. Different combinations and structures of propolis (Ps)-incorporated sodium alginate (SA) scaffolds were developed. The morphological studies showed that the porosity of developed scaffolds was optimized when 20% (v/v) of Ps was added to the solution. The pore sizes decreased by increasing Ps concentration up to a certain level due to its adhesive properties. The mechanical, swelling-degradation (weight loss) behaviors, and Ps release kinetics were highlighted for the scaffold stability. An antimicrobial assay was employed to test and screen antimicrobial behavior of Ps against Escherichia coli and Staphylococcus aureus strains. The results show that the Ps-added scaffolds have an excellent antibacterial activity because of Ps compounds. An in vitro cytotoxicity test was also applied on the scaffold by using the extract method on the human dermal fibroblasts (HFFF2) cell line. The 3D-printed SA-Ps scaffolds are very useful structures for wound dressing applications.publishersversionpublishe

Incidence and Prognosis of COVID-19 in Patients with Psoriasis: A Multicenter Prospective Study from the Eastern Black Sea Region of Turkey

COVID-19 infection can have a poor prognosis, especial- ly in patients with chronic diseases and those receiving immunosup- pressive or immunomodulating therapies. This study aimed to investigate the severity of COVID-19 infection in patients with psoriasis and compare the infection severity for sys- temic treatments and comorbidities. We conducted a study in the dermatology clinics of five different centers in the Eastern Black Sea region of Turkey. Four hundred and eighty-eight patients were included, and 22.5% were confirmed as having COVID-19 infection. In our study, the frequency of hospitalization rates due to COVID-19 infection were similar (15.4%, 25.9% respectively) in patients receiv- ing biological treatment and receiving non-biological systemic treat- ment (P=0.344). Hospitalization rates were higher in patients with hypertension, androgenetic alopecia, and acitretin use (P=0.043, P=0.028, P=0.040). In conclusion, current biologic treatments and non-biologic system- ic treatments in patients with psoriasis did not appear to increase the risk of the severe form of COVID-19, except for acitretin