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Permanent URI for this collectionhttps://hdl.handle.net/20.500.14288/3
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Publication Metadata only Stuck in a whirlpool? The role of hope and despair in dealing with risks during Afghan migration journeys(OXFORD UNIV PRESS, 2024) Van Heelsum, Anja; Graduate School of Social Sciences and HumanitiesMigration journeys are full of risk, navigated not just by physical obstacles but also by emotional tides. This study explores how the fluctuation of hope and despair plays a role in dealing with risks. Drawing upon in-depth interviews with Afghans in Turkey, this paper demonstrates that hope and despair fluctuate along migration journeys contingent upon three elements: (1) empirical evidence about the future, (2) (un)certainty and potential in the future, and (3) the agency or capability to act. The research finds that hope arises when the future is perceived as uncertain, offering individuals alternative pathways and restoring a sense of agency by transforming uncertainty into potentiality. Conversely, despair sets in when individuals perceive their near future as certain, devoid of alternatives. This sense of certainty about the near future leaves migrants feeling trapped, akin to being stuck in a whirlpool.Publication Metadata only Migration aspirations in relation to border closures, employment opportunities and risk-taking attitudes: lessons from an online survey experiment(Routledge Journals; Taylor and Francis, 2024) Elçi, Ezgi; Department of International Relations; Önay, Ayşen Ezgi Üstübici; Department of International Relations; College of Administrative Sciences and Economics; Graduate School of Social Sciences and HumanitiesThis article investigates the effect of structural and individual factors on migration aspirations in a secondary migration context. Through an online survey experiment conducted with Syrian migrants (N = 551) living in Turkey, we unpack factors explaining aspirations to stay and move onward from the current country of residence. The findings indicate that open borders alone do not compel migrants to move onward. Instead, employment opportunities in their current residence play a crucial role in shaping aspirations to stay put. Moreover, individuals inclined to take risks are more likely to migrate, even when strict border controls are in place. By highlighting the question of what motivates migrants to stay as well as to move onward, this research emphasizes individual differences in forming migration aspirations and contributes to migration aspirations literature in the secondary migration context.Publication Metadata only Validating digital traces with survey data: the use case of religiosity(Association for Computing Machinery, Inc, 2024) Department of Sociology;Department of Mathematics; Yörük, Erdem; Atsızelti, Şükrü; Yardı, Melih Can; Duruşan, Fırat; Etgü, Tolga; College of Social Sciences and Humanities; Graduate School of Social Sciences and Humanities; College of SciencesThis paper tests the validity of a digital trace database (Politus) obtained from Twitter, with a recently conducted representative social survey, focusing on the use case of religiosity in Turkey. Religiosity scores in the research are extracted using supervised machine learning under the Politus project. The validation analysis depends on two steps. First, we compare the performances of two alternative tweet-To-user transformation strategies, and second, test for the impact of resampling via the MRP technique. Estimates of the Politus are examined at both aggregate and region-level. The results are intriguing for future research on measuring public opinion via social media data.Publication Metadata only Vilma: a zero-shot benchmark for linguıstic and temporal grounding in video-language models(International Conference on Learning Representations, ICLR, 2024) Pedrotti, Andrea; Dogan, Mustafa; Cafagna, Michele; Parcalabescu, Letitia; Calixto, Iacer; Frank, Anetteh; Gatt, Albert; Department of Electrical and Electronics Engineering; Kesen, İlker; Erdem, Aykut; Department of Electrical and Electronics Engineering; Koç Üniversitesi İş Bankası Yapay Zeka Uygulama ve Araştırma Merkezi (KUIS AI)/ Koç University İş Bank Artificial Intelligence Center (KUIS AI); Graduate School of Sciences and Engineering; College of EngineeringWith the ever-increasing popularity of pretrained Video-Language Models (VidLMs), there is a pressing need to develop robust evaluation methodologies that delve deeper into their visio-linguistic capabilities. To address this challenge, we present VILMA), a task-agnostic benchmark that places the assessment of fine-grained capabilities of these models on a firm footing. Task-based evaluations, while valuable, fail to capture the complexities and specific temporal aspects of moving images that VidLMs need to process. Through carefully curated counterfactuals, VILMA offers a controlled evaluation suite that sheds light on the true potential of these models, as well as their performance gaps compared to human-level understanding. VILMA also includes proficiency tests, which assess basic capabilities deemed essential to solving the main counterfactual tests. We show that current VidLMs' grounding abilities are no better than those of vision-language models which use static images. This is especially striking once the performance on proficiency tests is factored in. Our benchmark serves as a catalyst for future research on VidLMs, helping to highlight areas that still need to be explored.Publication Metadata only Robotic radical prostatectomy for prostate cancer in renal transplant recipients: results from a multicenter series(Elsevier, 2022) Marra, Giancarlo; Agnello, Marco; Giordano, Andrea; Soria, Francesco; Oderda, Marco; Dariane, Charles; Timsit, Marc-Olivier; Branchereau, Julien; Hedli, Oussama; Mesnard, Benoit; Olsburgh, Jonathon; Kulkarni, Meghana; Kasivisvanathan, Veeru; Breda, Alberto; Biancone, Luigi; Gontero, Paolo; Tilki, Derya; School of Medicine; Koç University HospitalBackground: Despite an expected increase in prostate cancer (PCa) incidence in the renal transplant recipient (RTR) population in the near future, robot-assisted radical prostatectomy (RARP) in these patients has been poorly detailed. It is not well understood whether results are comparable to RARP in the non-RTR setting. Objective: To describe the surgical technique for RARP in RTR and report results from our multi-institutional experience. Design, setting, and participants: This was a retrospective review of the experience of four referral centers. Surgical procedure: Transperitoneal RARP with pelvic lymph node dissection in selected patients. Measurements: We measured patient, PCa, and graft baseline features; intraoperative and postoperative parameters; complications, (Clavien classification); and oncological and functional outcomes. Results and limitations: We included 41 men. The median age, American Society of Anesthesiologists score, preoperative renal function, and prostate-specific antigen were 60 yr (interquartile range [IQR] 57-64), 2 points (IQR 2-3), 45 ml/min (IQR 30-62), and 6.5 ng/ml (IQR 5.2-10.2), respectively. Four men (9.8%) had a biopsy Gleason score >7. The majority of the patients (70.7%) did not undergo lymphadenectomy. The median operating time, hospital stay, and catheterization time were 201 min (IQR 170-250), 4 d (IQR 2-6), and 10 d (IQR 7-13), respectively. At final pathology, 11 men had extraprostatic extension and seven had positive surgical margins. At median follow-up of 42 mo (IQR 24-65), four men had biochemical recurrence, including one case of local PCa persistence and one local recurrence. No metastases were recorded while two patients died from non-PCa-related causes. Continence was preserved in 86.1% (p not applicable) and erections in 64.7% (p = 0.0633) of those who were continent/potent before the procedure. Renal function remained unchanged (p = 0.08). No intraoperative complications and one major (Clavien 3a) complication were recorded. Conclusions: RARP in RTR is safe and feasible. Overall, operative, oncological, and functional outcomes are comparable to those described for the non-RTR setting, with graft injury remaining undescribed. Further research is needed to confirm our findings. Patient summary: Robot-assisted removal of the prostate is safe and feasible in patients who have a kidney transplant. Cancer control, urinary and sexual function results, and surgical complications seem to be similar to those for patients without a transplant, but further research is needed.Publication Metadata only The digital twin synchronization problem: framework, formulations, and analysis(Taylor & Francis Inc, 2023) Matta, Andrea; Department of Business Administration; Tan, Barış; Department of Business Administration; College of Administrative Sciences and EconomicsAs the adoption of digital twins increases steadily, it is necessary to determine how to operate them most effectively and efficiently. In this article, the digital twin synchronization problem is introduced and defined formally. Frequent synchronizations would increase cost and data traffic congestion, whereas infrequent synchronizations would increase the bias of the predictions and yield wrong decisions. This work defines the synchronization problem variants in different contexts. To discuss the problem and its solution, the problem of determining when to synchronize an unreliable production system with its digital twin to minimize the average synchronization and bias costs is formulated and analyzed analytically. The state-independent, state-dependent, and full-information solutions have been determined by using a stochastic model of the system. Solving the synchronization problem using simulation is discussed, and an approximate policy is proposed. Our results show that the performance of the state-dependent policy is close to the optimal solution that can be obtained with full information and significantly better than the performance of the state-independent policy. Furthermore, the approximate periodic state-dependent policy yields near-optimal results. To operate digital twins more effectively, the digital twin synchronization problem must be considered and solved to determine the optimal synchronization policy.Publication Metadata only Liquid metal microdroplet-initiated ultra-fast polymerization of a stimuli-responsive hydrogel composite(Wiley-V C H Verlag Gmbh, 2023) Zhang, Jianhua; Liao, Jiahe; Liu, Zemin; Zhang, Rongjing; Department of Mechanical Engineering; Sitti, Metin; Department of Mechanical Engineering; College of Engineering; School of MedicineRecent advances in composite hydrogels achieve material enhancement or specialized stimuli-responsive functionalities by pairing with a functional filler. Liquid metals (LM) offer a unique combination of chemical, electrical, and mechanical properties that show great potential in hydrogel composites. Polymerization of hydrogels with LM microdroplets as initiators is a particularly interesting phenomenon that remains in its early stage of development. In this work, an LM-hydrogel composite is introduced, in which LM microdroplets dispersed inside the hydrogel matrix have dual functions as a polymerization initiator for a polyacrylic acid-poly vinyl alcohol (PAA/PVA) network and, once polymerized, as passive inclusion to influence its material and stimuli-responsive characteristics. It is demonstrated that LM microdroplets enable ultra-fast polymerization in approximate to 1 min, compared to several hours by conventional polymerization techniques. The results show several mechanical enhancements to the PAA/PVA hydrogels with LM-initiated polymerization. It is found that LM ratios strongly influence stimuli-responsive behaviors in the hydrogels, including swelling and ionic bending, where higher LM ratios are found to enhance ionic actuation performance. The dual roles of LM in this composite are analyzed using the experimental characterization results. These LM-hydrogel composites, which are biocompatible, open up new opportunities in future soft robotics and biomedical applications. A composite hydrogel embedded with liquid metal (LM) microdroplets is introduced, where the LM microdroplets have dual roles of initiating ultra-fast polymerization and passive inclusion. The physical effects of LM on polymerization and stimuli-responsive behaviors are analyzed, including swelling and ionic actuation due to osmotic pressure differences. Their benefits to the LM-hydrogel functionalities, such as robot locomotion, are demonstrated.Publication Metadata only Micro- and nanofabrication of dynamic hydrogels with multichannel information(Nature Research, 2023) Zhang, Mingchao; Lee, Yohan; Zheng, Zhiqiang; Khan, Muhammad Turab Ali; Lyu, Xianglong; Byun, Junghwan; Giessen, Harald; Department of Mechanical Engineering; Sitti, Metin; Department of Mechanical Engineering; College of Engineering; School of MedicineCreating micro/nanostructures containing multi-channel information within responsive hydrogels presents exciting opportunities for dynamically changing functionalities. However, fabricating these structures is immensely challenging due to the soft and dynamic nature of hydrogels, often resulting in unintended structural deformations or destruction. Here, we demonstrate that dehydrated hydrogels, treated by a programmable femtosecond laser, can allow for a robust fabrication of micro/nanostructures. The dehydration enhances the rigidity of the hydrogels and temporarily locks the dynamic behaviours, significantly promoting their structural integrity during the fabrication process. By utilizing versatile dosage domains of the femtosecond laser, we create micro-grooves on the hydrogel surface through the use of a high-dosage mode, while also altering the fluorescent intensity within the rest of the non-ablated areas via a low-dosage laser. In this way, we rationally design a pixel unit containing three-channel information: structural color, polarization state, and fluorescent intensity, and encode three complex image information sets into these channels. Distinct images at the same location were simultaneously printed onto the hydrogel, which can be observed individually under different imaging modes without cross-talk. Notably, the recovered dynamic responsiveness of the hydrogel enables a multi-information-encoded surface that can sequentially display different information as the temperature changes.Publication Metadata only Hydrogel muscles powering reconfigurable micro-metastructures with wide-spectrum programmability(Nature Portfolio, 2023) Zhang, Mingchao; Pal, Aniket; Zheng, Zhiqiang; Gardi, Gaurav; Yildiz, Erdost; Department of Mechanical Engineering; Sitti, Metin; Department of Mechanical Engineering; College of Engineering; School of MedicineStimuli-responsive geometric transformations endow metamaterials with dynamic properties and functionalities. However, using existing transformation mechanisms to program a single geometry to transform into diverse final configurations remains challenging, imposing crucial design restrictions on achieving versatile functionalities. Here, we present a programmable strategy for wide-spectrum reconfigurable micro-metastructures using linearly responsive transparent hydrogels as artificial muscles. Actuated by the hydrogel, the transformation of micro-metastructures arises from the collaborative buckling of their building blocks. Rationally designing the three-dimensional printing parameters and geometry features of the metastructures enables their locally isotropic or anisotropic deformation, allowing controllable wide-spectrum pattern transformation with programmable chirality and optical anisotropy. This reconfiguration mechanism can be applied to various materials with a wide range of mechanical properties. Our strategy enables a thermally reconfigurable printed metalattice with pixel-by-pixel mapping of different printing powers and angles for displaying or hiding complex information, providing opportunities for encryption, miniature robotics, photonics and phononics applications. It is difficult to program a single stimuli-responsive geometry to transform into diverse final configurations in a systematic manner. Here, linearly responsive transparent hydrogels are developed to create micro-metastructures with wide-spectrum thermal reconfigurability.Publication Metadata only Pangolin-inspired untethered magnetic robot for on-demand biomedical heating applications(Nature Portfolio, 2023) Soon, Ren Hao; Yin, Zhen; Dogan, Metin Alp; Dogan, Nihal Olcay; Tiryaki, Mehmet Efe; Karacakol, Alp Can; Aydin, Asli; Esmaeili-Dokht, Pouria; Department of Mechanical Engineering; Sitti, Metin; Department of Mechanical Engineering; College of Engineering; School of MedicineUntethered magnetic miniature soft robots capable of accessing hard-to-reach regions can enable safe, disruptive, and minimally invasive medical procedures. However, the soft body limits the integration of non-magnetic external stimuli sources on the robot, thereby restricting the functionalities of such robots. One such functionality is localised heat generation, which requires solid metallic materials for increased efficiency. Yet, using these materials compromises the compliance and safety of using soft robots. To overcome these competing requirements, we propose a pangolin-inspired bi-layered soft robot design. We show that the reported design achieves heating > 70 degrees C at large distances > 5cm within a short period of time <30s, allowing users to realise on-demand localised heating in tandem with shape-morphing capabilities. We demonstrate advanced robotic functionalities, such as selective cargo release, in situ demagnetisation, hyperthermia and mitigation of bleeding, on tissue phantoms and ex vivo tissues. Untethered soft robots developed to date display limited functionalities beyond locomotion and cargo delivery. Here, the authors present a pangolin-inspired robotic design which enables heating >70 degrees C at distances > 5cm without compromising their compliance, for biomedical applications.