Spatial and Temporal Trends of Mining-Related Lead-Zinc Sediment Contamination, Galena River Watershed, SW Wisconsin-NW Illinois

Alluvial sediments within the Galena River Watershed were severely contaminated with heavy metals by historical zinc (Zn) and lead (Pb) mining operations during the early 1800s until 1979. Since the mines closed, there have been efforts to remediate on-site mine waste. However, the effectiveness of these efforts to reduce metal concentrations in stream sediments is unknown. This study compares present-day (2017) contamination trends in the Galena River Watershed to trends reported 25 years ago. A total of 415 sediment/soil samples were collected and analyzed using X-ray florescence spectrometry to determine sediment metal concentrations. The highest concentrations of zinc measured were 23,577 ppm in the channel bed, 19,825 ppm in the channel banks, and 51,273 ppm in tailings. Zinc concentrations averaged 198 ppm within the unmined Madden Branch (n=10), 2,057 ppm within the main branch of the Galena (n=31), 9,569 ppm within the heavily mined Diggings Branch (n=11), and 26,158 ppm in tailings (n=16). Present day contamination trends show little difference compared to 25 years ago. However, stream sediments collected downstream of some large-scale remediation projects have shown significant decreases in Zn concentrations. Nevertheless, even with continued efforts to remediate contaminated sediments in the Galena River, high concentrations will probably persist far into the future

Lower bounds for the Tur\'an densities of daisies

For integers $r \geq 3$ and $t \geq 2$, an $r$-uniform $t$-daisy $\mathcal{D}^t_r$ is a family of $\binom{2t}{t}$ $r$-element sets of the form $$\{S \cup T \ : T\subset U, \ |T|=t \}$$ for some sets $S,U$ with $|S|=r-t$, $|U|=2t$ and $S \cap U = \emptyset$. It was conjectured by Bollob\'as, Leader and Malvenuto (and independently Bukh) that the Tur\'an densities of $t$-daisies satisfy $\lim\limits_{r \to \infty} \pi(\mathcal{D}_r^t) = 0$ for all $t \geq 2$; this has become a well-known problem, and it is still open for all values of $t$. In this paper, we give lower bounds for the Tur\'an densities of $r$-uniform $t$-daisies. To do so, we introduce (and make some progress on) the following natural problem in additive combinatorics: for integers $m \geq 2t \geq 4$, what is the maximum cardinality $g(m,t)$ of a subset $R$ of $\mathbb{Z}/m\mathbb{Z}$ such that for any $x \in \mathbb{Z}/m\mathbb{Z}$ and any $2t$-element subset $X$ of $\mathbb{Z}/m\mathbb{Z}$, there are $t$ distinct elements of $X$ whose sum is not in the translate $x+R$? This is a slice-analogue of the extremal Hilbert cube problem considered by Gunderson and R\"odl and its generalization studied by Cilleruelo and Tesoro.Comment: 11 pages. Minor changes made in response to comments of two anonymous referee

The optimisation of a paired emitter-detector diode optical pH sensing device

With recent improvements in wireless sensor network hardware there has been a concurrent push to develop sensors that are suitable in terms of price and performance. In this paper a low cost gas sensor is detailed, and significant improvements in sensor characteristics have been achieved compared to previously published results. A chemical sensor is presented based on the use of low cost LEDs as both the light source and photodetector, coupled with a sensor slide coated with a pH sensitive colorimetric dye to create a simple gas sensor. Similar setups have been successfully used to detect both acetic acid and ammonia. The goal of this work was to optimise the system performance by integration of the sensing technique into a purposely deigned flowcell platform that holds the colorimetric slide and optical detector in position. The reproducibility of the sensor has been improved through this arrangement and careful control of deposited film thickness. The enhanced reproducibility between sensors opens the potential of calibration-free measurement, in that calibration of one sensor can be used to model the characteristics of all sensors in a particular batch

Extensions of Autocorrelation Inequalities with Applications to Additive Combinatorics

Barnard and Steinerberger [‘Three convolution inequalities on the real line with connections to additive combinatorics’, Preprint, 2019, arXiv:1903.08731] established the autocorrelation inequality Min_(0≤t≤1)∫_Rf(x)f(x+t) dx ≤ 0.411||f||²L¹, for fϵL¹(R), where the constant 0.4110.411 cannot be replaced by 0.370.37. In addition to being interesting and important in their own right, inequalities such as these have applications in additive combinatorics. We show that for f to be extremal for this inequality, we must have max min_(x₁∈R 0≤t≤1)[f(x₁−t)+f(x₁+t)] ≤ min_max(x₂∈ R0≤t≤1)[f(x₂−t)+f(x₂+t)]. Our central technique for deriving this result is local perturbation of f to increase the value of the autocorrelation, while leaving ||f||L¹|| unchanged. These perturbation methods can be extended to examine a more general notion of autocorrelation. Let d, n∈Z⁺, f∈L¹, A be a d×n matrix with real entries and columns a_i for 1≤i≤n and C be a constant. For a broad class of matrices A, we prove necessary conditions for f to extremise autocorrelation inequalities of the form Min_(t∈ [0,1]^d)∫R∏_(i=1)^n f(x+t⋅a_i)dx≤C||f||^nL¹

OpenEarable:Open Hardware Earable Sensing Platform

Earables are ear-worn devices that offer functionalities beyond basic audio in- and output. In this paper we present the ongoing development of a new, open-source, Arduino-based earable platform called OpenEarable. It is based on standard components, is easy to manufacture and costs roughly $40 per device at batch size ten. We present the first version of the device which is equipped with a series of sensors and actuators: a 3-axis accelerometer and gyroscope, an ear canal pressure and temperature sensor, an inward facing ultrasonic microphone as well as a speaker, a push button, and a controllable LED. We demonstrate the versatility of the prototyping platform through three different example application scenarios. In sum, OpenEarable offers a general-purpose, open sensing platform for earable research and development.<br/

The development of low-cost, robust, reproducible optical chemical sensors using inkjet printing

The optical sensor industry is forseen to be- come a $4 billion market worldwide within 10 years. This projected figure suggests the incorporation of wireless sensor networks into our daily lives. In order to achieve this, many hardware requirements have already been met, with many of the world’s top university in- volved in wireless "mote" development. The objective of this study is to prove that inkjet printed sensors will be compatible with these motes in terms of both accuracy and more im- portantly reproducibility