Kinetics and Mechanism of Metal Nanoparticle Growth via Optical Extinction Spectroscopy and Computational Modeling: The Curious Case of Colloidal Gold

An overarching computational framework unifying several optical theories to describe the temporal evolution of gold nanoparticles (GNPs) during a seeded growth process is presented. To achieve this, we used the inexpensive and widely available optical extinction spectroscopy, to obtain quantitative kinetic data. In situ spectra collected over a wide set of experimental conditions were regressed using the physical model, calculating light extinction by ensembles of GNPs during the growth process. This model provides temporal information on the size, shape, and concentration of the particles and any electromagnetic interactions between them. Consequently, we were able to describe the mechanism of GNP growth and divide the process into distinct genesis periods. We provide explanations for several longstanding mysteries, for example, the phenomena responsible for the purple-greyish hue during the early stages of GNP growth, the complex interactions between nucleation, growth, and aggregation events, and a clear distinction between agglomeration and electromagnetic interactions. The presented theoretical formalism has been developed in a generic fashion so that it can readily be adapted to other nanoparticulate formation scenarios such as the genesis of various metal nanoparticles.Comment: Main text and supplementary information (accompanying MATLAB codes available on the journal webpage

Analysis of Paradoxes in Fingerprint Countermeasures

The widespread usage of new user tracking methods, i.e. web-based fingerprinting, is becoming a serious privacy concern as third parties try to track users across different websites. Meanwhile, it is usually difficult or impossible for users to opt-out fingerprinting if they want to fully benefit the services provided by the application or website. Several studies tried to address the privacy issue in browser fingerprinting, mostly by faking attribute values. However, such configuration spoofing may lead to inconsistencies that paradoxically make the user stand out even more. This study analyzes these paradoxes in browser configuration with the creation of a Markov model based on a test dataset. Given a target spoofed attribute, the implemented tool in this study outputs the other attributes that must be consequently altered, not to cause paradoxical configuration. Similarly, this tool can suggest a set of random attributes to be spoofed with suggested values, not creating a paradoxical configuration. The tool Implemented in this study can be used by browser extension developers and should help them spoof browser attributes more sophistically, thus preservingusers' privacy against cross-site web-based browser fingerprinting.Peer reviewe

SiMEA : a Framework for simulating neurons on Multi-Electrode Array

Proceeding volume: 38A Multi-Electrode Array (MEA) is a practical device for recording the extracellular activity of in-vitro biological culture. Such culture - for instance neurons - is prone to mistakes leading to irrelevant recordings or no recording at all. Additionally, with the expenses generated by in-vitro culture, minimizing risks is a must. This paper proposes a framework designed and implemented for simulating the spatial positioning of neuronal cultures on a MEA. The framework serves as a sandbox for researchers to simulate the model of their MEA experiments before its eventual in-vitro implementation. The framework enables simulating the density of the plated culture, the death of cells over time, choosing diverse reconstructed morphologies of cells, and simulating their spiking activity in interaction with Brian2 simulator.Peer reviewe

Sensitive Research, Practice, and Design in HCI

New research areas in HCI examine complex and sensitive research areas, such as crisis, life transitions, and mental health. Further, research in complex topics such as harassment and graphic content can leave researchers vulnerable to emotional and physical harm. There is a need to bring researchers together to discuss challenges across sensitive research spaces and environments. We propose a workshop to explore the methodological, ethical, and emotional challenges of sensitive research in HCI. We will actively recruit from diverse research environments (industry, academia, government, etc.) and methods areas (qualitative, quantitative, design practices, etc.) and identify commonalities in and encourage relationship-building between these areas. This one-day workshop will be led by academic and industry researchers with diverse methods, topical, and employment experiences

HCI and Sensitive Life Experiences

HCI research has identified a number of life events and life transitions which see individuals in a vulnerable state, such as gender transition, domestic abuse, romantic relationship dissolution, bereavement, and even genocide. Although these life events differ across the human lifespan, considering them as a group of ‘sensitive life experiences’, and exploring the similarities and differences in how we approach those experiences as researchers could be invaluable in generating a better understanding of them. In this workshop, we aim to identify current opportunities for, and barriers to, the design of social computing systems that support people during sensitive life events and transitions. Participants will take part in activities centred around exploring the similarities and differences between their own and others’ research methods and results, drawing on their own experiences in discussions around carrying out research in these sensitive contexts

Channel Estimation in Coded Modulation Systems

With the outstanding performance of coded modulation techniques in fading channels, much research efforts have been carried out on the design of communication systems able to operate at low signal-to-noise ratios (SNRs). From this perspective, the so-called iterative decoding principle has been applied to many signal processing tasks at the receiver: demodulation, detection, decoding, synchronization and channel estimation. Nevertheless, at low SNRs, conventional channel estimators do not perform satisfactorily. This thesis is mainly concerned with channel estimation issues in coded modulation systems where different diversity techniques are exploited to combat fading in single or multiple antenna systems. First, for single antenna systems in fast time-varying fading channels, the thesis focuses on designing a training sequence by exploiting signal space diversity (SSD). Motivated by the power/bandwidth efficiency of the SSD technique, the proposed training sequence inserts pilot bits into the coded bits prior to constellation mapping and signal rotation. This scheme spreads the training sequence during a transmitted codeword and helps the estimator to track fast variation of the channel gains. A comprehensive comparison between the proposed training scheme and the conventional training scheme is then carried out, which reveals several interesting conclusions with respect to both error performance of the system and mean square error of the channel estimator. For multiple antenna systems, different schemes are examined in this thesis for the estimation of block-fading channels. For typical coded modulation systems with multiple antennas, the first scheme makes a distinction between the iteration in the channel estimation and the iteration in the decoding. Then, the estimator begins iteration when the soft output of the decoder at the decoding iteration meets some specified reliability conditions. This scheme guarantees the convergence of the iterative receiver with iterative channel estimator. To accelerate the convergence process and decrease the complexity of successive iterations, in the second scheme, the channel estimator estimates channel state information (CSI) at each iteration with a combination of the training sequence and soft information. For coded modulation systems with precoding technique, in which a precoder is used after the modulator, the training sequence and data symbols are combined using a linear precoder to decrease the required training overhead. The power allocation and the placement of the training sequence to be precoded are obtained based on a lower bound on the mean square error of the channel estimation. It is demonstrated that considerable performance improvement is possible when the training symbols are embedded within data symbols with an equi-spaced pattern. In the last scheme, a joint precoder and training sequence is developed to maximize the achievable coding gain and diversity order under imperfect CSI. In particular, both the asymptotic performance behavior of the system with the precoded training scheme under imperfect CSI and the mean square error of the channel estimation are derived to obtain achievable diversity order and coding gain. Simulation results demonstrate that the joint optimized scheme outperforms the existing training schemes for systems with given precoders in terms of error rate and the amount of training overhead

Life Transitions and Social Technologies:Research and Design for Times of Life Change

When people experience major changes in their lives (e.g., relationship changes, transition from high school to college, realizing an LGBTQ identity, etc.), they often turn to social technologies to help navigate shifting identities and networks and find support and resources. People's experiences using social technologies during times of life transition, and how to better design such technologies, has been a major focus of social computing research. This workshop will gather researchers working in this space to discuss eight themes: life events vs. processes; changing identities; multiple overlapping life events; physical and digital transitions; technology non-use during life transitions; liminality framework; theoretical frames; and methodological considerations. Collaboratively, we will 1) synergize insights from workshop organizers' and participants' research to determine how social technologies can be designed to better support people during life transitions and 2) outline an agenda for the future of social computing work on life transitions.<br/