Random Projections For Large-Scale Regression

Fitting linear regression models can be computationally very expensive in large-scale data analysis tasks if the sample size and the number of variables are very large. Random projections are extensively used as a dimension reduction tool in machine learning and statistics. We discuss the applications of random projections in linear regression problems, developed to decrease computational costs, and give an overview of the theoretical guarantees of the generalization error. It can be shown that the combination of random projections with least squares regression leads to similar recovery as ridge regression and principal component regression. We also discuss possible improvements when averaging over multiple random projections, an approach that lends itself easily to parallel implementation.Comment: 13 pages, 3 Figure

Near-forward Raman scattering by bulk and surface phonon-polaritons in the model percolation-type ZnBeSe alloy

We study the bulk and surface phonon-polaritons of the Zn0.67Be0.33Se zincblende alloy by near-forward Raman scattering. The short (Be-Se) bond exhibits a distinct percolation doublet in the conventional backscattering Raman spectra, corresponding to a three-mode behavior in total [1(Zn-Se),2(Be-Se)] for Zn0.67Be0.33Se. This offers an opportunity to achieve a refined understanding of the phonon-polariton modes of a zincblende alloy beyond the current two-mode approximation, corresponding to a [1(Zn-Se),1(Be-Se)] description in the present case. The discussion is supported by contour modeling of the Raman signals of the multi-mode bulk and surface phonon-polaritons within the formalism of the linear dielectric response

Understanding the risk of emerging bacterial resistance to over the counter antibiotics in topical sore throat medicines

Aims The aims of this study were to explore the development of bacterial resistance and cross‐resistance in four common human pathogens following realistic exposure to antibiotics found in over‐the‐counter (OTC) sore throat medicines: gramicidin, neomycin, bacitracin and tyrothricin. Methods and Results Bacterial exposure to in‐use (concentration in the product before use) and diluted concentration (i.e. during use ) of antibiotic where conducted in broth for 24 h or until growth was visible. The changes in bacterial susceptibility profile before and after exposure was determined using standardized ISO microdilution broth. Antibiotic testing was performed according to EUCAST guidelines. We demonstrated that test bacteria were able to survive exposure to the in‐use concentrations of some antibiotics used in OTC medicines. Exposure to during use concentrations of bacitracin resulted in stable increase in minimal inhibitory concentration (MIC) (>8‐fold) in Staphylococcus aureus and Acinetobacter baumannii . Exposure to tyrothricin resulted in a stable increase in MIC (2·4‐fold) in Klebsiella pneumoniae , and exposure to neomycin resulted in a stable increase MIC (5000‐fold higher than the baseline) in Streptococcus pyogenes . Clinical cross‐resistance to other antibiotics (ciprofloxacin, fusidic acid, gentamicin, cefpodoxime, amoxicillin/clavulanic acid and cefotaxime) was also demonstrated following exposure to bacitracin or tyrothricin. Bacitracin exposure lead to a stable bacterial resistance after 10 passages. Conclusions Our results indicate that OTC antibiotic medicines have the potential to drive resistance and cross‐resistance in vitro . Significance and Impact of the Study Tackling antibiotic resistance is a high worldwide priority. It is widely accepted that the overuse and misuse of antibiotics increase the risk of the development and spread of antibiotic resistance within communities. A number of OTC sore throat products, widely available across the world for topical use in respiratory indications, contain locally delivered antibiotics. Our findings showed that these antibiotics in OTC medicines present a risk for emerging cross‐resistance in a number of bacterial respiratory pathogens

Private Incremental Regression

Data is continuously generated by modern data sources, and a recent challenge in machine learning has been to develop techniques that perform well in an incremental (streaming) setting. In this paper, we investigate the problem of private machine learning, where as common in practice, the data is not given at once, but rather arrives incrementally over time. We introduce the problems of private incremental ERM and private incremental regression where the general goal is to always maintain a good empirical risk minimizer for the history observed under differential privacy. Our first contribution is a generic transformation of private batch ERM mechanisms into private incremental ERM mechanisms, based on a simple idea of invoking the private batch ERM procedure at some regular time intervals. We take this construction as a baseline for comparison. We then provide two mechanisms for the private incremental regression problem. Our first mechanism is based on privately constructing a noisy incremental gradient function, which is then used in a modified projected gradient procedure at every timestep. This mechanism has an excess empirical risk of $\approx\sqrt{d}$, where $d$ is the dimensionality of the data. While from the results of [Bassily et al. 2014] this bound is tight in the worst-case, we show that certain geometric properties of the input and constraint set can be used to derive significantly better results for certain interesting regression problems.Comment: To appear in PODS 201

Near-forward Raman selection rules of the phonon-polariton created by alloying in (Zn,Be)Se

The Raman selection rules of the (ZnSe, BeSe) mixed phonon polariton created by alloying in the three mode (1ZnSe, 2BeSe) ZnBeSe system, whose dramatic S like dispersion covers the large frequency gap between the ZnSe and BeSe spectral ranges, is studied in its wave vector dependence by near forward scattering. Both the collapse regime away from the Brillouin zone centre and the reinforcement regime near the Brillouin zone centre are addressed, using appropriate laser lines and Be contents. We find that in both regimes the considered phonon polariton, in fact a transverse mode with mixed mechanical and electrical character, obeys the same nominal Raman selection rules as its purely mechanical variant commonly observed in the backscattering geometry. Besides, marked differences in the phonon polariton Raman lineshapes in the two regimes give a hint about how the phonon polariton electrical field E develops while descending the S like dispersion towards the Brillouin zone centre. In the reinforcement regime E is large, leading to intramode on top of intermode transfers of oscillator strength mediated by E between the two BeSe modes, that both exhibit a fine structure on account of the alloy disorder. In contrast, in the collapse regime E remains weak, as testified by the absence of intramode transfer. The discussion is supported by contour modeling of the multi phonon polariton Raman lineshapes in their wave vector dependence within the linear dielectric approach.Comment: 16 pages, 7 figure

An Evolutionary Optimization Approach to Risk Parity Portfolio Selection

In this paper we present an evolutionary optimization approach to solve the risk parity portfolio selection problem. While there exist convex optimization approaches to solve this problem when long-only portfolios are considered, the optimization problem becomes non-trivial in the long-short case. To solve this problem, we propose a genetic algorithm as well as a local search heuristic. This algorithmic framework is able to compute solutions successfully. Numerical results using real-world data substantiate the practicability of the approach presented in this paper

Extreme State Aggregation Beyond MDPs

We consider a Reinforcement Learning setup where an agent interacts with an environment in observation-reward-action cycles without any (esp.\ MDP) assumptions on the environment. State aggregation and more generally feature reinforcement learning is concerned with mapping histories/raw-states to reduced/aggregated states. The idea behind both is that the resulting reduced process (approximately) forms a small stationary finite-state MDP, which can then be efficiently solved or learnt. We considerably generalize existing aggregation results by showing that even if the reduced process is not an MDP, the (q-)value functions and (optimal) policies of an associated MDP with same state-space size solve the original problem, as long as the solution can approximately be represented as a function of the reduced states. This implies an upper bound on the required state space size that holds uniformly for all RL problems. It may also explain why RL algorithms designed for MDPs sometimes perform well beyond MDPs.Comment: 28 LaTeX pages. 8 Theorem

Acute and Chronic Effects of SGLT2 Inhibitor Empagliflozin on Renal Oxygenation and Blood Pressure Control in Nondiabetic Normotensive Subjects: A Randomized, Placebo-Controlled Trial.

Background The sodium/glucose cotransporter 2 inhibitor empagliflozin has cardiorenal protective properties through mechanisms beyond glucose control. In this study we assessed whether empagliflozin modifies renal oxygenation as a possible mechanism of renal protection, and determined the metabolic, renal, and hemodynamic effects of empagliflozin in nondiabetic subjects. Methods and Results In this double-blind, randomized, placebo-controlled study, 45 healthy volunteers underwent blood and urine sampling, renal ultrasound, and blood-oxygenation-level-dependent magnetic resonance imaging before and 180 minutes after administration of 10 mg empagliflozin (n=30) or placebo (n=15). These examinations were repeated after 1 month of daily intake. Cortical and medullary renal oxygenation were not affected by the acute or chronic administration of empagliflozin, as determined by 148 renal blood-oxygenation-level-dependent magnetic resonance imaging examinations. Empagliflozin increased glucosuria (24-hour glucosuria at 1 month: +50.1±16.3 g). The acute decrease in proximal sodium reabsorption, as determined by endogenous fractional excretion of lithium (-34.6% versus placebo), was compensated at 1 month by a rise in plasma renin activity (+28.6%) and aldosterone (+55.7%). The 24-hour systolic and diastolic ambulatory blood pressures decreased significantly after 1 month of empagliflozin administration (-5.1 and -2.0 mm Hg, respectively). Serum uric acid levels decreased (-28.4%), hemoglobin increased (+1.7%), and erythropoietin remained the same. Conclusions Empagliflozin has a rapid and significant effect on tubular function, with sustained glucosuria and transient natriuresis in nondiabetic normotensive subjects. These effects favor blood pressure reduction. No acute or sustained changes were found in renal cortical or medullary tissue oxygenation. It remains to be determined whether this is the case in nondiabetic or diabetic patients with congestive heart failure or kidney disease. REGISTRATION: URL: https://www.clini​caltr​ials.gov; Unique identifier: NCT03093103

Impact of material properties in determining quaternary ammonium compound adsorption and wipe product efficacy against biofilms

Background Disinfectant wipes containing quaternary ammonium compounds (QACs) are widely used within healthcare. Viscose remains a popular material for these products, though limited information is available concerning its impact on performance against biofilms when compared to alternatives. Aim Identify disinfectant wipe materials and surface properties which optimise product performance against biofilms. Methods Biofilm eradication performance of two commercial viscose-QAC wipes was determined against Staphylococcus aureus and Acinetobacter baumannii dry surface biofilms (DSBs), using an ASTM E2967-based procedure. Additionally, five materials were impregnated with a commercial liquid formulation containing didecyldimethylammonium chloride (DDAC). Following 24-hour storage, eradication performance and DDAC content of extracted liquid were determined and compared to material properties including zeta potential, hydrophobicity and surface area. Findings Under stringent test conditions, eradication of DSBs by commercial products was no greater than equivalent materials impregnated with water. Extract from one viscose-based product contained 89% less DDAC than the impregnation solution, indicating extensive adsorption. Of the other tested materials, viscose performed worst; nearly 70% of DDAC had depleted from material extracts within 24-hours. In contrast, DDAC depletion from polypropylene (PP) extracts was only 25% and DSB eradication was >100-times greater than viscose. Biofilm eradication performance against both species correlated to the DDAC content of extracts which, in turn, correlated to zeta potential and hydrophobicity. Conclusion Biofilm eradication performance of QAC-based wipes was significantly greater when selecting thermoplastic substrates over viscose. However, these materials are non-sustainably sourced and non-biodegradable. This study highlights a need to develop new wipe products more effective against biofilms