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Publication Metadata only ‘Anti-commutable’ local pre-Leibniz algebroids and admissible connections(Elsevier, 2023) Department of Physics; N/A; Dereli, Tekin; Doğan, Keremcan; Faculty Member; PhD Student; Department of Physics; College of Sciences; Graduate School of Sciences and Engineering; 201358; N/AThe concept of algebroid is convenient as a basis for constructions of geometrical frameworks. For example, metric-affine and generalized geometries can be written on Lie and Courant algebroids, respectively. Furthermore, string theories might make use of many other algebroids such as metric algebroids, higher Courant algebroids, or conformal Courant algebroids. Working on the possibly most general algebroid structure, which generalizes many of the algebroids used in the literature, is fruitful as it creates a chance to study all of them at once. Local pre-Leibniz algebroids are such general ones in which metric-connection geometries are possible to construct. On the other hand, the existence of the 'locality operator', which is present for the left-Leibniz rule for the bracket, necessitates the modification of torsion and curvature operators in order to achieve tensorial quantities. In this paper, this modification of torsion and curvature is explained from the point of view that the modification is applied to the bracket instead. This leads one to consider 'anti-commutable' local pre-Leibniz algebroids which satisfy an anti-commutativity-like property defined with respect to a choice of an equivalence class of connections. These 'admissible' connections are claimed to be the necessary ones while working on a geometry of algebroids. This claim is due to the fact that one can prove many desirable properties and relations if one uses only admissible connections. For instance, for admissible connections, we prove the first and second Bianchi identities, Cartan structure equations, Cartan magic formula, the construction of Levi-Civita connections, the decomposition of connection in terms of torsion and non-metricity. These all are possible because the modified bracket becomes anti-symmetric for an admissible connection so that one can apply the machinery of almost-or pre-Lie algebroids. We investigate various algebroid structures from the literature and show that they admit admissible connections which are metric-compatible in some generalized sense. Moreover, we prove that local pre-Leibniz algebroids that are not anti-commutable cannot be equipped with a torsion-free, and in particular Levi-Civita, connection.Publication Metadata only (Im)moral borders in practice(Taylor & Francis, 2021) El Qadim, Nora; Isleyen, Beste; de Vries, Leonie Ansems; Hansen, Signe Sofie; Lisle, Debbie; Simonneau, Damien; N/A; Karadağ, Sibel; Researcher; Migration Research Program at Koç University (MIReKoç) / Göç Araştırmaları Uygulama ve Araştırma Merkezi (MIReKoç); N/A; N/AThis Forum aims to push existing debates in critical border and migration studies over the featuring of morals, ethics and rights in everyday practices relating to the governance of the mobility of non-citizen populations. Its contributors steer away from the actual evaluation or advocacy of the good/just/ethical, focusing instead on the sociological examination of morals and ethics in practice, i.e. how actors understand morally and ethically the border and migration policies they implement or resist. A proliferating interest in the discursive and non-discursive materialisation of moral and ethical elements in asylum and migration policies has examined the intertwinement of care and control logics underlying the management of refugee camps, borders and borderzones, and hotspots alongside the deployment of search-and-rescue operations. Nevertheless, recent research has shown the need to unpack narratives and actions displaying values and symbols that are not necessarily encompassed within this intertwinement of compassion and repression. We argue that there is a need to pay more attention to the diversity, plurality and the operation of morality, ethics and rights in settings and geographies, and of including a diversity of actors both across and beyond EUrope.Publication Metadata only 21 fs Cr:LiSAF laser mode locked with a single-walled carbon nanotube saturable absorber(Optical Soc Amer, 2019) Bae, Ji Eun; Rotermund, Fabian; Demirbaş, Ümit; N/A; N/A; N/A; Department of Physics; Tanısalı, Gökhan; Toker, Işınsu Baylam; Taşçı, Mısra; Sennaroğlu, Alphan; PhD Student; PhD Student; Undergraduate Student; Faculty Member; Department of Physics; Koç University Surface Science and Technology Center (KUYTAM) / Koç Üniversitesi Yüzey Teknolojileri Araştırmaları Merkezi (KUYTAM); Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; School of Medicine; College of Sciences; N/A; N/A; N/A; 23851We report the shortest femtosecond pulses directly generated from a solid-state laser that is mode locked by using a single-walled carbon nanotube saturable absorber (SWCNT-SA). In the experiments, we used a 660 nm diode-pumped, low-threshold extended-cavity Cr:LiSAF laser operating around 850 nm with a repetition rate of 47.9 MHz. The SWCNT-SA mode-locked Cr:LiSAF laser produced 21 fs pulses with a time-bandwidth product of 0.56 by using only 210 mW of pump power. Pump-probe spectroscopy measurements showed that the SWCNT-SA exhibited saturable absorption with slow and fast decay times of 2.7 ps and 0.4 ps. The single-pass modulation depth and saturation fluence of the SWCNT-SA were further determined as 0.3% and 45 mu J/cm(2) at the pump wavelength of 850 nm.Publication Metadata only 3D printed poly(lactic acid) scaffolds modified with chitosan and hydroxyapatite for bone repair applications(Elsevier, 2020) N/A; N/A; N/A; N/A; Department of Chemistry; Department of Chemical and Biological Engineering; Department of Chemistry; Nazeer, Muhammad Anwaar; Önder, Özgün Can; Sevgili, İlkem; Yılgör, Emel; Kavaklı, İbrahim Halil; Yılgör, İskender; PhD Student; PhD Student; PhD Student; Researcher; Faculty Member; Faculty Member; Department of Chemical and Biological Engineering; Department of Chemistry; Koç University Surface Science and Technology Center (KUYTAM) / Koç Üniversitesi Yüzey Teknolojileri Araştırmaları Merkezi (KUYTAM); Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; College of Sciences; College of Engineering; College of Sciences; N/A; N/A; N/A; N/A; 40319; 241813D printed poly(lactic acid) (PLA) scaffolds surface modified with chitosan (CS) and hydroxyapatite (HA) to produce a novel bioactive composite scaffold is reported. Excellent mechanical properties of PLA, the bioactivity of CS, and osteogenic characteristics of HA are combined to fabricate composite scaffolds using a simple desktop 3D printer. Scaffolds were characterized through attenuated total reflection-Fourier transform infrared (ATR-FTIR) spectroscopy, scanning electron microscopy (SEM), energy dispersive X-ray (EDX) spectroscopy, X-ray diffraction (XRD) and water contact angle measurements before and after modification. Formic acid was used as a solvent to prepare stable CS/HA dispersions and was found to be a suitable solvent for producing PLA/CS/HA composites. Surface properties of modified scaffolds were superior in terms of hydrophilicity and bioactivity, which resulted in enhanced attachment and proliferation of human osteosarcoma cells in vitro compared to the unmodified PLA scaffolds.Publication Metadata only 3D surface topography analysis in 5-axis ball-end milling(Elsevier, 2017) N/A; Department of Mechanical Engineering; Khavidaki, Sayed Ehsan Layegh; Lazoğlu, İsmail; PHD Student; Faculty Member; Department of Mechanical Engineering; Graduate School of Sciences and Engineering; College of Engineering; N/A; 179391This article presents a new analytical model to predict the topography and roughness of the machined surface in 5-axis ball-end milling operation for the first time. The model is able to predict the surface topography and profile roughness parameters such as 3D average roughness (Sa) and 3D root mean square roughness (Sq) by considering the process parameters such as the feedrate, number of flutes, step over and depth of cut as well as the effects of eccentricity and tool runout in 5-axis ball-end milling. This model allows to simulate the effects of the lead and tilt angles on the machined surface quality in the virtual environment prior to the costly 5-axis machining operations. The effectiveness of the introduced surface topography prediction model is validated experimentally by conducting 5-axis ball-end milling tests in various cutting conditions. (C) 2017 Published by Elsevier Ltd on behalf of CIRP.Publication Metadata only A bi-criteria optimization model to analyze the impacts of electric vehicles on costs and emissions(Elsevier, 2017) N/A; N/A; Department of Industrial Engineering; Kabatepe, Bora; Türkay, Metin; Master Student; Faculty Member; Department of Industrial Engineering; Graduate School of Sciences and Engineering; College of Engineering; N/A; 24956Electric vehicles (EV) are emerging as a mobility solution to reduce emissions in the transportation sector. The studies environmental impact analysis of EVs in the literature are based on the average energy mix or pre-defined generation scenarios and construct policy recommendations with a cost minimization objective. However, the environmental performance of EVs depends on the source of the marginal electricity provided to the grid and single objective models do not provide a thorough analysis on the economic and environmental impacts of EVs. In this paper, these gaps are addressed by a four step methodology that analyzes the effects of EVs under different charging and market penetration scenarios. The methodology includes a bi-criteria optimization model representing the electricity market operations. The results from a real-life case analysis show that EVs decrease costs and emissions significantly compared to conventional vehicles.Publication Metadata only A CAM-based path generation method for rapid prototyping applications(Springer London Ltd, 2011) N/A; Department of Mechanical Engineering; Lazoğlu, İsmail; N/A; Faculty Member; Department of Mechanical Engineering; Manufacturing and Automation Research Center (MARC); N/A; College of Engineering; N/A; 179391A wide range of rapid prototyping (RP) methods are available commercially. Even though the hardware and production materials of these RP methods differ, their production techniques are built on the same idea: layer-by-layer material additive manufacturing. Whatever the material is used, it is deposited, vulcanized, or melted by following a pre-determined path, and each layer is stowed on the previous one to create the 3D model which is designed by using a computer-aided design program. The path which is followed while creating the model is very crucial. In this paper, a novel idea for path generation for RP processes is introduced. This new method is based on computer numerical controlled milling operation. Although the RP process and the milling process are completely opposite of each other since one of them is an additive and the other one is a subtractive method, the paths which are followed for these operations are very similar and based on the same idea: The progress goes on layer by layer. In this novel method, cutter location source files are used to create paths for RP processes. Examples of the prototypes produced by using this new method are also presented in the paper.Publication Open Access A common genetic variation of melanoma inhibitory activity-2 labels a subtype of pancreatic adenocarcinoma with high endoplasmic reticulum stress levels.(Nature Publishing Group (NPG), 2015) Kong, Bo; Wu, Weiwei; Valkovska, Nataliya; Jager, Carsten; Hong, Xin; Nitsche, Ulrich; Friess, Helmut; Esposito, Irene; Kleeff, Joerg; Michalski, Christoph W.; N/A; Erkan, Murat Mert; Faculty Member; School of Medicine; 214689HNF1 homeoboxA(HNF1A)-mediated gene expression constitutes an essential component of the secretory pathway in the exocrine pancreas. Melanoma inhibitory activity 2 (MIA2), a protein facilitating protein secretion, is an HNF1A target. Protein secretion is precisely coordinated by the endoplasmic reticulum (ER) stress/unfolded protein response (UPR) system. Here, we demonstrate that HNFA and MIA2 are expressed in a subset of human PDAC tissues and that HNF1A induced MIA2 in vitro. We identified a common germline variant of MIA2 (c.A617G:p.I141M) associated with a secretory defect of the MIA2 protein in PDAC cells. Patients carrying MIA2(I141M) survived longer after tumor resection but the survival benefit was restricted to those patients who received adjuvant chemotherapy. The MIA2(I141M) variant was associated with high expression of ER stress/UPR genes - in particular those of the ERN1/XBP arm - in human PDAC samples. Accordingly, PDAC cell lines expressing the MIA2(I141M) variant expressed high levels of ERN1 and were more sensitive to gemcitabine. These findings define an interaction between the common MIA2(I141M) variant and the ER stress/UPR system and specify a subgroup of PDAC patients who are more likely to benefit from adjuvant chemotherapy.Publication Metadata only A comparison of piezosurgery with conventional techniques for internal osteotomy(Springer, 2017) Dogan, R.; N/A; Koçak, İlker; Gökler, Ozan; Doctor; Teaching Faculty; N/A; School of Medicine; Koç University Hospital; Koç University Hospital; N/A; 311179To compare conventional osteotomy with the piezosurgery medical device, in terms of postoperative edema, ecchymosis, pain, operation time, and mucosal integrity, in rhinoplasty patients. In this prospective study, 49 rhinoplasty patients were randomly divided into two groups according to osteotomy technique used, either conventional osteotomy or piezosurgery. For all patients, the total duration of the operation was recorded, and photographs were taken and scored for ecchymosis and edema on postoperative days 2, 4, and 7. In addition, pain level was evaluated on postoperative day 2, and mucosal integrity was assessed on day 4. All scoring and evaluation was conducted by a physician who was blinded to the osteotomy procedure. In the piezosurgery group, edema scores on postoperative day 2 and ecchymosis scores on postoperative days 2, 4, and 7 were significantly lower than in the conventional osteotomy group (p < 0.05). On postoperative day 2, the pain level was lower in the piezosurgery group than in the conventional osteotomy group (p < 0.05). In an endoscopic examination on postoperative day 4, while 24% of the patients in the conventional osteotomy group had mucosal damage, no such damage was observed in the piezosurgery group. When total operation duration was compared, there was no significant difference between the groups (p > 0.05). Piezosurgery is a safe osteotomy method, with less edema (in the early postoperative period) and ecchymosis compared with conventional osteotomy, as well as less pain, a similar operation duration, and no mucosal damage.Publication Metadata only A compassionate self is a true self? self-compassion promotes subjective authenticity(Sage, 2019) Zhang, Jia Wei; Chen, Serena; Shakur, Teodora K. Tomova; Chai, Wen Jia; Ramis, Tamilselvan; Shaban-Azad, Hadi; Razavi, Pooya; Nutankumar, Thingujam; Manukyan, Arpine; N/A; Bilgin, Begüm; Master Student; Graduate School of Social Sciences and Humanities; N/ATheory and research converge to suggest that authenticity predicts positive psychological adjustment. Given these benefits of authenticity, there is a surprising dearth of research on the factors that foster authenticity. Five studies help fill this gap by testing whether self-compassion promotes subjective authenticity. Study 1 found a positive association between trait self-compassion and authenticity. Study 2 demonstrated that on days when people felt more self-compassionate, they also felt more authentic. Study 3 discovered that people experimentally induced to be self-compassionate reported greater state authenticity relative to control participants. Studies 4 and 5 recruited samples from multiple cultures and used a cross-sectional and a longitudinal design, respectively, and found that self-compassion predicts greater authenticity through reduced fear of negative evaluation (Study 4) and heightened optimism (Study 5). Across studies, self-compassion's effects on authenticity could not be accounted for by self-esteem. Overall, the results suggest that self-compassion can help cultivate subjective authenticity.