Katz School of Science and Health: Faculty Publications
Permanent URI for this collectionhttps://hdl.handle.net/20.500.12202/3942
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Item Open Access Distribution of blackouts in the power grid and the Motter and Lai model(arXiv.org, 2020-08-03) Cwilich, Gabriel; Kornbluth, Yosef; Buldyrev, Sergey V.; Soltan, Saleh; Zussman, Gil; 0000-0001-6736-3517Carreras, Dobson and colleagues have studied empirical data on the sizes of the blackouts in real grids and modeled them by computer simulations using the direct current approximation. They have found that the resulting blackout sizes are distributed as a power law and suggested that this is because the grids are driven to the self-organized critical state. In contrast, more recent studies found that the distribution of cascades is bimodal as in a first order phase transition, resulting in either a very small blackout or a very large blackout, engulfing a finite fraction of the system. Here we reconcile the two approaches and investigate how the distribution of the blackouts change with model parameters, including the tolerance criteria and the dynamic rules of failure of the overloaded lines during the cascade. In addition, we study the same problem for the Motter and Lai model and find similar results, suggesting that the physical laws of flow on the network are not as important as network topology, overload conditions, and dynamic rules of failure. Comment: (10 pages, 6 figures)Item Metadata only Synergy between antifreeze proteins is driven by complementary ice-binding(2019) Drori, Ran; 0000-0002-6436-5602In some cold-adapted organisms, over a dozen isoforms of antifreeze (glyco)proteins or AF(G)Ps are present. Although these isoforms are structurally similar, their ability to inhibit ice growth varies significantly, and, in some fish, passive isoforms can be much more abundant than the active ones. Laboratory experiments demonstrated more than a decade ago that mixtures of AFP isoforms can exhibit synergistic enhancement of each other's activity. The mechanism of this synergy effect has remained obscure and is addressed here. Using cold-stages, microfluidics, and fluorescence microscopy, the activity of binary mixtures of structurally distinct AF(G)Ps from different fish and plant species was measured. While several mixtures exhibited enhancement, some mixtures exhibited antagonism. These latter mixtures included AF(G)Ps that bind to the same crystal planes, thereby exhibiting competition. Fluorescence microscopy experiments with a synergistic mixture of two isoform types labeled with different dyes showed they bound to different crystal planes. These results helped develop a kinetic description of the mechanism by which AF(G)Ps achieve synergy. The requirements of an active isoform include high adsorption rates, and prism plane binding, while passive isoforms usually bind to a pyramidal plane at slower rates. For synergy to occur, an active isoform first binds to the faster growing prism plane. This binding slows the advancement of the prism plane and creates more pyramidal surfaces to which a passive isoform bind. These results, in part, explain the biological observation of isoform distribution in fish, and the physical chemistry of the synergistic crystal growth inhibition by two inhibitors.Item Open Access Random sequential adsorption on euclidean, fractal and random lattices(arxiv.org, 2019) Cwilich, Gabriel; Pasinetti, Pedro M.; Ramirez, Lucia S.; Centres, Paulo M.; Ramirez-Pastor, Antonio J.; 0000-0001-6736-3517Irreversible adsorption of objects of diferent shapes and sizes on Euclidean, fractal and random lattices is studied. The adsorption process is modeled by using random sequential adsorption (RSA) algorithm. Objects are adsorbed on one-, two-, and three-dimensional Euclidean lattices, on Sierpin- ski carpets having dimension d between 1 and 2, and on Erdos-Renyi random graphs. The number of sites is M = Ld for Euclidean and fractal lattices, where L is a characteristic length of the sys- tem. In the case of random graphs it does not exist such characteristic length, and the substrate can be characterized by a xed set of M vertices (sites) and an average connectivity (or degree) g. The paper concentrates on measuring (1) the probability WL(M)( ) that a lattice composed of Ld(M) elements reaches a coverage , and (2) the exponent j characterizing the so-called \jamming transition". The results obtained for Euclidean, fractal and random lattices indicate that the main quantities derived from the jamming probability WL(M)( ) behave asymptotically as M1=2. In the case of Euclidean and fractal lattices, where L and d can be de ned, the asymptotic behavior can be written as M1=2 = Ld=2 = L1= j , and j = 2=d.Item Open Access Aghamolla, C., & Hashimoto, T. (2020). Information arrival, delay, and clustering in financial markets with dynamic freeriding. Journal of Financial Economics, 138(1), 27-52.(Wiley Subscription Services, Inc., 2021., 2021) Hashimoto, Tadashi; 0000-0002-4048-7234Aggressive Boards and CEO Turnover∗ Cyrus Aghamolla† Tadashi Hashimoto‡ January 4, 2021 Abstract This study investigates a communication game between a CEO and a board of directors where the CEO’s career concerns can potentially impede value-increasing informative communication. By adopting a policy of aggressive boards (excessive replacement), shareholders can facilitate communication between the CEO and the board. The results are in contrast to the multitude of models which generally find that management-friendly boards improve communication, and help to explain empirical results concerning CEO turnover. The results also provide the following novel pre- dictions concerning variation in CEO turnover: (i) there is greater CEO turnover in firms or industries where CEO performance is relatively more difficult to assess; (ii) the board is more aggressive in their replacement of the CEO in industries or firms where the board’s advisory role is more salient; and (iii) there is comparatively less CEO turnover in firms or industries where the variance of CEO talent is high.Item Metadata only Information arrival, delay, and clustering in financial markets with dynamic freeriding(Elsevier B. V., 2020) Hashimoto, Tadashi; Aghamolla, Cyrus; 0000-0002-4048-7234We study informational freeriding in a model where agents privately acquire information and then decide when to reveal it by taking an action. Examples of such freeriding are prevalent in financial markets, e.g., the timing of initial public offerings, analysts’ forecasts, and mutual funds’ investment decisions. The main results show that, in large populations, few agents provide significant information while the vast majority of agents freeride. We highlight the role of uncertainty and market size in shaping the dynamics of price discovery. Among other results, we find that heightened uncertainty over the underlying state enhances information production, yet weakens the precision and speed of information aggregation in the market.Item Metadata only Understanding father-child joint play experience using a convergent mixed-methods design(American Occupational Therapy Association, 2022) Waldman-Levi, Amiya; Cope, Amber; Olson, Laurette; 0000-0002-4698-8427•Importance: Research on the characteristics of father-child play is limited, and how fathers perceive this experience and its contribution to children's development and the parent-child relationship is insufficiently described. •Objective: To explore associations between fathers' own playfulness, their supportiveness of child playfulness, and child playfulness and fathers' perceptions of their joint play experiences. Design: Convergent mixed-methods design. •Setting: Family homes. Participants: The participants were 57 father-child dyads who resided in a metropolitan area. Children were ages 2 to 5 yr. Interviews with 11 fathers (ages 25-56 yr) were included in the qualitative analysis. •Outcomes and Measures: Fathers completed a background questionnaire and the Short Measure of Adult Playfulness (SMAP) and participated in a semistructured interview. Fifteen minutes of video-recorded joint play were scored using the Parent/Caregiver Support of Children's Playfulness (PCSCP) and the Test of Playfulness (ToP). •Results: Fathers' own playfulness as measured with the SMAP was not related to their child's playfulness as measured with the ToP; however, their supportive behavior as measured with the PCSCP was associated with their child's playfulness. Fathers recognized the benefits of joint play for their child's development. •Conclusions and Relevance: The current findings help fill the gap in research linking fathers' own playfulness and supportiveness during joint play and their child's playfulness with fathers' perceptions of this experience. What This Article Adds: Understanding fathers' perceptions and behaviors can further enhance service delivery to children and families through interprofessional work to benefit parent-child relationships as well as child development. Play is a central and fundamental area of occupation in children's lives, and it significantly contributes to their overall development (e.g., Skard & Bundy, 2008; Waldman-Levi & Bundy, 2016). Joint [...]Item Metadata only Playing playfully to overcome adversity: A telehealth-based group teacher training program.(SAGE, 2023) Waldman-Levi, Amiya; Halperin, Lola; 0000-0002-4698-8427Teacher's exposure to childhood adversity may lead to secondary stress compromising child-teacher interactions. Our telehealth-delivered teacher group program focused on play and playfulness in the classroom and stress management for teachers. Program manual and fidelity checklist were developed, and program's fidelity was assessed through manual adherence and participants attendance and satisfaction. Five participants attended the program, and five occupational therapy students served as fidelity raters. Rater agreement levels confirmed that the checklist was sufficiently developed to capture the program's essential elements. Follow-up interviews indicated that the program equipped participants with new skills and validated their existing knowledge/experience while offering tangible learning materials. Teachers' stress can be mitigated by providing them with a safe space to learn skills to promote playfulness in the classroom and to share with and support each other. The manualization of our program and fidelity checklist can guide the development of similar interventions.Item Metadata only Securing microservices against password guess attacks using hardware performance counters(Institute of Electrical and Electronics Engineers (IEEE), 2022-09) Kadiyala, Sai Praveen; Li, Xiaolan; Lee, Wonjun; Catlin, Andrew Gar; 0000-0001-5996-2421Modern customer-facing applications need to be easy to use, localizable, and to scale out to serve large customer bases. Microservice architectures have the potential to decentralize functionality, improve flexibility, and provide faster time to market of incremental changes. However, applications implemented as microservices also have a larger surface area, which may make them more prone to cyber attacks. Modern operating systems provide performance counters which are tamper-resistant, and can be used to track the run-time behavior of applications. In this work, we aim to detect a password guess attack on microservice using performance counter data. Our approach consists of modelling behavior of normal and attack user login requests, identification of key performance counters that effectively distinguish these requests and developing a machine learning model that classifies unknown login requests. A fully connected neural network-based classification model gave us 98.3% test accuracy in detecting the attacks with a false negative rate of 1.6%.Item Metadata only Utilization of 3D printed orthoses for musculoskeletal conditions of the upper extremity: A systematic review.(Elsevier, 2021-11-21) Schwartz, Deborah A.; Schofield, Katherine A.● A systematic review was performed on studies utilizing 3D printed orthoses for musculoskeletal conditions of the elbow, wrist, hand and digits in clinical settings. ● The 10 studies included in this systematic review report on actual patient use of 3D printed orthoses. ● The 3D printing process of orthoses for the upper extremity remains complex and under-utilized. ● There is a need for more clinical trials to study the benefits of 3D printed orthoses compared with custom made low temperature thermoplastic orthoses for patients in the hand therapy setting. Systematic Review 3D printed orthoses are emerging as a possible option in the field of hand therapy to fabricate conventional casts and orthoses. It is unknown how this technology is currently being used to treat upper extremity musculoskeletal conditions, and if 3D orthoses are comparable to custom- made low temperature thermoplastic orthoses fabricated by hand therapists. The primary aim of this review was to investigate the utilization, effectiveness and feasibility of 3D printed technology to manufacture custom orthoses for musculoskeletal conditions of the upper extremity. Studies describing 3D printed orthoses or casts used in treatment with patients were included following a comprehensive literature search using CINAHL, PubMed, Medline, ProQuest, and EBSCO databases. The selected studies had to address musculoskeletal conditions of the elbow, wrist, hand and/or digits that would typically be immobilized with a cast or brace or orthotic or orthosis. Ten studies met the inclusion criteria. Study designs included case studies, case series, and 1 randomized clinical trial. 3D printed orthoses/casts appear to be comfortable, provide adequate immobilization, and have pleasing aesthetics. However, expensive equipment, lack of appropriate software and scanning tools and lack of highly skilled clinicians are all factors preventing the implementation of 3D printed orthoses into current clinical practice. 3D printed orthoses appear to be effective at immobilization of a limb, aesthetically pleasing, and utilize lightweight and well -ventilated materials. However, the feasibility of implementing 3D printing technology in hand therapy settings remains challenging in part due to the resources required. While 3D printing shows promise, the high cost of equipment, lack of training and skill of clinicians and the long time required for production are all factors that need to be improved to make 3D printing a viable option in the hand therapy setting. [ABSTRACT FROM AUTHOR]Item Metadata only A Hard Pill to Swallow(The Johns Hopkins Press, 2022) Barrera, Marissa A.; O’Connor Wells, B.; O’Connor Wells, B.; Procaro, C. K.; 0000-0001-7410-9955Item Restricted Presbyphagia versus dysphagia normal versus abnormal swallowing symptoms in older adults with Parkinson disease and multiple sclerosis(Wolters Kluwer Health, 2023) Barrera, Marissa A.; O'Connor Wells, B.; 0000-0001-7410-9955The purpose of this article is to describe normal, age-related changes in the swallowing mechanism, clinically referred to as “presbyphagia.” The authors compare presbyphagia in the oral, pharyngeal, and esophageal phases of the swallow to abnormal, or impaired swallowing, termed “dysphagia.” This article focuses on how older persons with Parkinson disease and multiple sclerosis frequently have dysphagia symptoms, such as food residue, delayed swallow trigger, penetration, and/or aspiration, superimposed over presbyphagia. Information on the psychosocial and emotional impacts of dysphagia on persons with Parkinson disease and/or multiple sclerosis, along with common treatment approaches to alleviate swallowing difficulties, has also been discussed.