Pedagogical demonstration of twitter data analysis: A case study of world AIDS day, 2014

As a pedagogical demonstration of Twitter data analysis, a case study of HIV/AIDS-related tweets around World AIDS Day, 2014, was presented. This study examined if Twitter users from countries with various income levels responded differently to World AIDS Day. The performance of support vector machine (SVM) models as classifiers of relevant tweets was evaluated. A manual coding of 1,826 randomly sampled HIV/AIDS-related original tweets from November 30 through December 2, 2014 was completed. Logistic regression was applied to analyze the association between the World Bank-designated income level of users’ self-reported countries and Twitter contents. To identify the optimal SVM model, 1278 (70%) of the 1826 sampled tweets were randomly selected as the training set, and 548 (30%) served as the test set. Another 180 tweets were separately sampled and coded as the held-out dataset. Compared with tweets from low-income countries, tweets from the Organization for Economic Cooperation and Development countries had 60% lower odds to mention epidemiology (adjusted odds ratio, aOR = 0.404; 95% CI: 0.166, 0.981) and three times the odds to mention compassion/support (aOR = 3.080; 95% CI: 1.179, 8.047). Tweets from lower-middle-income countries had 79% lower odds than tweets from low-income countries to mention HIV-affected sub-populations (aOR = 0.213; 95% CI: 0.068, 0.664). The optimal SVM model was able to identify relevant tweets from the held-out dataset of 180 tweets with an accuracy (F1 score) of 0.72. This study demonstrated how students can be taught to analyze Twitter data using manual coding, regression models, and SVM models

Tau neutrino deep inelastic charged current interactions

The nu_mu -> nu_tau oscillation hypothesis will be tested through nu_tau production of tau in underground neutrino telescopes as well as long-baseline experiments. We provide the full QCD framework for the evaluation of tau neutrino deep inelastic charged current (CC) cross sections, including next-leading-order (NLO) corrections, charm production, tau threshold, and target mass effects in the collinear approximation. We investigate the violation of the Albright-Jarlskog relations for the structure functions F_4,5 which occur only in heavy lepton (tau) scattering. Integrated CC cross sections are evaluated naively over the full phase space and with the inclusion of DIS kinematic cuts. Uncertainties in our evaluation based on scale dependence, PDF errors and the interplay between kinematic and dynamical power corrections are discussed and/or quantified.Comment: 28 pages, 10 figure

Aspects of Two-Photon Physics at Linear e+e- Colliders

We discuss various reactions at future e+e- and gamma-gamma colliders involving real (beamstrahlung or backscattered laser) or quasi--real (bremsstrahlung) photons in the initial state and hadrons in the final state. The production of two central jets with large pT is described in some detail; we give distributions for the rapidity and pT of the jets as well as the di--jet invariant mass, and discuss the relative importance of various initial state configurations and the uncertainties in our predictions. We also present results for `mono--jet' production where one jet goes down a beam pipe, for the production of charm, bottom and top quarks, and for single production of W and Z bosons. Where appropriate, the two--photon processes are compared with annihilation reactions leading to similar final states. We also argue that the behaviour of the total inelastic gamma-gamma cross section at high energies will probably have little impact on the severity of background problems caused by soft and semi--hard (`minijet') two--photon reactions. We find very large differences in cross sections for all two--photon processes between existing designs for future e+e- colliders, due to the different beamstrahlung spectra; in particular, both designs with >1 events per bunch crossing exist.Comment: 51 pages, 13 figures(not included

The Opportunity Cost of the Conservation Reserve Program: A Kansas Land Example

The effects of the Conservation Reserve Program (CRP) on farmland values is investigated using a set of parcel-level data for land sales in Kansas over the period 1998 to 2014. The sales data are used to estimate a hedonic model of land values that allows for the opportunity cost of CRP enrollment to vary across space and time. Factors impacting the opportunity costs include the relative productivity of land, returns to farming, and the time remaining under the CRP contracts. We find that the discount associated with having land under CRP contract averages 7%

Estudo fitoquímico de folhas de Solanum lycocarpum A. St.-Hil (Solanaceae) e sua aplicação na alelopatia

(Phytochemistry of Solanum lycocarpum A.St.–Hil (Solanaceae) leaves and their application in allelopathy). Solanum lycocarpum A.St.-Hil (Solanaceae) is a typical shrub in the Cerrado of central Brazil. The allelopathic activity of aqueous extracts of the leaves and fruits of this species has already been proven in previous studies. The goal of this work was to verify the allelopathic activity of different leaf extracts of S. lycocarpum on the germination and growth of four target species. The leaves were collected, dried, triturated and submitted to two distinct methods of extraction: 1- liquid--liquid (ethyl acetate and dichloromethane) from the aqueous extract and 2- with solvents of increasing polarities (hexane, dichloromethane, ethyl acetate, acetone, methanol and water) directly from the leaves. Each extraction was made with ultrasound equipment for one hour, filtered and evaporated. From these extracts, solutions of 800, 400 and 200 ppm were prepared, and water and Logran® were used as positive and negative controls, respectively. Each solution, as well as the controls, was dissolved in DMSO for the bioassays. The target species used were lettuce, watercress, tomato and onion. To each plate, 20 seeds were added and 1 mL of the tested solutions (with 4 repetitions). The plates were incubated at 25 oC without light, and the shoots and roots of the seedlings were then measured and the percentage of germination and the inhibition of each extract were calculated. Tomato was the most sensitive to the extracts, followed by watercress, onion and lettuce. The extracts with stronger activity were AcOEt, acetone and the liquid-liquid extraction, indicating the fractions that may contain the active principles of the leaves in this species

The Cholecystectomy As A Day Case (CAAD) Score: A Validated Score of Preoperative Predictors of Successful Day-Case Cholecystectomy Using the CholeS Data Set

Background Day-case surgery is associated with significant patient and cost benefits. However, only 43% of cholecystectomy patients are discharged home the same day. One hypothesis is day-case cholecystectomy rates, defined as patients discharged the same day as their operation, may be improved by better assessment of patients using standard preoperative variables. Methods Data were extracted from a prospectively collected data set of cholecystectomy patients from 166 UK and Irish hospitals (CholeS). Cholecystectomies performed as elective procedures were divided into main (75%) and validation (25%) data sets. Preoperative predictors were identified, and a risk score of failed day case was devised using multivariate logistic regression. Receiver operating curve analysis was used to validate the score in the validation data set. Results Of the 7426 elective cholecystectomies performed, 49% of these were discharged home the same day. Same-day discharge following cholecystectomy was less likely with older patients (OR 0.18, 95% CI 0.15–0.23), higher ASA scores (OR 0.19, 95% CI 0.15–0.23), complicated cholelithiasis (OR 0.38, 95% CI 0.31 to 0.48), male gender (OR 0.66, 95% CI 0.58–0.74), previous acute gallstone-related admissions (OR 0.54, 95% CI 0.48–0.60) and preoperative endoscopic intervention (OR 0.40, 95% CI 0.34–0.47). The CAAD score was developed using these variables. When applied to the validation subgroup, a CAAD score of ≤5 was associated with 80.8% successful day-case cholecystectomy compared with 19.2% associated with a CAAD score >5 (p < 0.001). Conclusions The CAAD score which utilises data readily available from clinic letters and electronic sources can predict same-day discharges following cholecystectomy