nils-herrmann/clean_scirepeval huggingface dataset:
Selecting Confounders from Covariates

Most analyses of observational studies to investigate the relationship between a risk factor and an outcome use some data-dependent method to select a subset of the available covariates to include as confounders. This paper evaluates methods which can be used to make this selection in linear models. The methods are applied to the selection of covariates in a study of the effect of lead in the blood on children's ability and are evaluated by a simulation study on multivariate normal data. None of the methods can be guaranteed to give satisfactory results in all cases, and all the methods can result in misleading inferences. Recommendations for the design and analysis of observational studies are made in the light of these results. Selection procedures for variables, such as stepwise regression methods, are commonly used in the analysis of observational studies. They are the default option in the regression procedures of most statistical packages and, in my experience, most users of such packages believe that good statistical practice requires their use. Their most obvious role is as part of exploratory data analysis, to seek out the most important independent variables. But it is also common to use a selection procedure before estimating a parameter or making a prediction, and then to work from the chosen model as if it had been chosen a priori. The general problem of statistical inferences after preliminary tests has long been recognized (e.g. Bancroft (1964)) and guidelines for some problems were investigated in the 1960s, when it was expected that the availability of high speed computers would help to determine when preliminary tests (like those used to select variables) would give increased power without compromising the validity of the final inference. Reality has turned out somewhat differently. High speed computers have increased the number of preliminary tests that are carried out, largely ignoring their influence on the true size of the final test or confidence interval. The selection of a subset of variables in a linear model for the prediction of future values of the dependent variable has been the focus of many statistical papers. Much of this work, reviewed by Hocking (1976) and Thompson (1978a, b), has been concerned with deriving mean-square error of prediction (MSEP) criteria that can be calculated from the data and have expectations equal to the MSEP. Several statistical packages now include a regression option that uses a leaps and bounds

Field of study: Mathematics
Determination of Rebaudioside A in steviosides by HPLC

A quantitative method for the determination of rebaudioside A (R-A) in stevia rebaudiana extration by means of HPLC. According to GB 8270-1999, we used external standard method to determine R-A through UV detector and Kromasil NH2 Column (250 mm×4.6 mm i.d., 5 μm) as analysis column, acetonitrile and water (80∶20) as mobile phase. The linear range of R-A was 0.1~1.0 mg/mL. The average recovery was 101.51%,RSD was 1.22%. It is suggested that this method is simple, rapid and good linear for R-A quantitative analysis.

Field of study: Agricultural and Food sciences
Measuring attitudes regarding bisexuality in lesbian, gay male, and heterosexual populations

Five studies on the development and validation of the Attitudes Regarding Bisexuality Scale (ARBS) were conducted. Factor analysis of an initial pool of 80 items yielded 2 factors assessing the degree to which bisexuality is viewed as a tolerable, moral sexual orientation (Tolerance) and a legitimate, stable sexual orientation (Stability). Three forms of the ARBS were created: a form to assess attitudes about female and male bisexuality (i.e., ARBS-FM) and forms to assess attitudes about female bisexuality (i.e., ARBS-F) and male bisexuality (ARBS-M). These forms evidenced moderate-to-high internal consistency reliability in both lesbian and gay samples and heterosexual samples. In heterosexual women and men, subscales were most strongly related to attitudes toward lesbians and gay men; frequency of religious attendance; political ideology; and prior contact with lesbian, gay, and bisexual people. In lesbians and gay men, subscales correlated with prior experiences with bisexual people, desired contact with bisexual people, contact with heterosexual people, and sexual orientation identity.

Field of study: Psychology
Geochemical signatures of the early Campanian belemnite Belemnellocamax mammillatus from the Kristianstad Basin in Scania, Sweden

article Macrofossil calcite plays a central role for palaeoenvironmental reconstructions because its preservation state and geochemical signatures can be checked using a variety of screening techniques. Reconstructions of the ecology and seawater composition from such data require knowledge about species-specific compositions of well-preserved calcitic fossils. Comprehensive datasets, recording averages, intraspecimen and intraspecific variability of geochemical proxies in fossil calcite, however, are still largely lacking. Here we report δ 13 C and δ 18 O values, as well as Mg/Ca, Sr/Ca and Mn/Ca ratios of 204 aliquots sampled along transectsthroughthree rostraof thelate earlyCampanianbelemnite speciesBelemnellocamax mammillatus. Geo- chemical signatures of partially altered samples are consistent to those reported for early marine calcite cemen- tationandshowtrendstowardsmoderatelyhigherMn/Ca,heavier δ 13 CandlowerSr/Ca.Incontrast,Mg/Caratios and δ 18 O values remain similar to projected original values. Median δ 18 Ov alues of−0.3 to 0.0‰ are comparable to the heaviest values of coeval oysters from the same localities, and internal variability of the well-preserved parts of the rostra is low. These findings suggest that B. mammillatus lived mostly in the deep part of the basin where seasonal changes were low and water temperatures cool. The δ 13 C is offset from oysters and most coeval

Field of study: Environmental science, Geography
An Axiomatic Approach to “Preference for Freedom of Choice”

The paper axiomatically characterizes a notion of “freedom of choice.“ The central condition considered in this paper is the following. In every non-empty opportunity set there exists at least one alternative such that its exclusion would reduce an agent 's freedom. It turns out that this condition induces a formal structure which is familiar from the theory of revealed preference. Under a somewhat different interpretation, some well-known rationality conditions are used to characterize models of freedom. Furthermore, a link is established between the notion of “preference for freedom” and Kreps' concept of “preference for flexibility.”Journal of Economic LiteratureClassification Number: D71.

Field of study: Economics
Proenkephalin A-derived peptides in invertebrate innate immune processes.

Lipopolysaccharides (LPS) injection into the coelomic fluid of the leech Theromyzon tessulatum stimulates release of proenkephalin A (PEA)-derived peptides as determined by immunoprecipitation and Western blot analyses. This release occurs in the first 15 min after LPS exposure and yields a 5.3-kDa peptide fragment corresponding to the C-terminal part of the precursor. This fragment is then cleaved to free an antibacterial peptide related to mammals arginine phenylalanine extended enkelytin: the peptide B. These PEA processing peptides were characterized using a combination of techniques including reversed-phase HPLC, microsequencing and mass spectrometry. The isolated invertebrate peptide B presents a high sequence homology with the bovine's and the same activity against Gram+bacteria. Titrations revealed the simultaneous appearance of Methionine-enkephalin (ME) and peptide B in invertebrates after stimulation by LPS (in a dose-dependent manner), surgical trauma or electrical stimulations to neural tissues of the mussel. Furthermore, peptide B processing in vitro yields Methionine-enkephalin arginine phenylalanine (MERF), which exhibits via the delta receptors, immunocyte excitatory properties, i.e., movement and conformational changes, but no antibacterial activity. We surmise that this unified response to the various stimuli is a survival strategy for organism by providing immediate antibacterial activity and immunocyte stimulation, thereby reducing any immune latency period needed for an adequate immune response.

Field of study: Biology
Computations via Newtonian and relativistic kinematic systems

We are developing a rigorous methodology to analyse experimental computation, by which we mean the idea of computing a set or function by experimenting with some physical equipment. Here we consider experimental computation by kinematic systems under both Newtonian and relativistic kinematics. An experimental procedure, expressed in a language similar to imperative programming languages, is applied to equipment, having the form of a bagatelle, and is interpreted using the two theories. We prove that for any set A of natural numbers there exists a two-dimensional kinematic system B"A with a single particle P whose observable behaviour decides [email protected]?A for all [email protected]?N. The procedure can operate under (a) Newtonian mechanics or (b) relativistic mechanics. The proofs show how any information (coded by some A) can be embedded in the structure of a simple kinematic system and retrieved by simple observations of its behaviour. We reflect on the methodology, which seeks a formal theory for performing abstract experiments with physical restrictions on the construction of systems. We conclude with some open problems.

Field of study: Mathematics
Local oscillating electron heating mechanism during laser plasma interaction

The interaction between laser and plasma has been studied using a 2.5 dimensional particle simulation code. The results show that electrons are accelerated by J×B heating mechanism and a strong electrostatic field is caused by charge separation, which has a potential well structure. Electrons are oscillating in electrostatic field potential wells and can be accelerated many times. Some electrons with higher velocity escape from potential wells, so that charge separation becomes stronger and stronger, and then electrostatic fields break up and electrons get the energy of electrostatic field. During the process, electrons are oscillating locally and accelerated, their relativistic kinetic energy can reach over 10 MeV. This is a new kind of heating mechanism and is named local oscillating electron heating mechanism.

Field of study: Physics
Experimental investigation on TBAB clathrate hydrate slurry flows in a horizontal tube: Forced convective heat transfer behaviors

Tetra-n-butyl-ammonium bromide (TBAB) clathrate hydrate slurry (CHS) is one kind of secondary refrigerants, which is promising to be applied into air-conditioning or latent-heat transportation systems as a thermal storage or cold carrying medium for energy saving. it is a solid-liquid two phase mixture which is easy to produce and has high latent heat and good fluidity. In this paper, the heat transfer characteristics of TBAB slurry were investigated in a horizontal stainless steel tube under different solid mass fractions and flow velocities with constant heat flux. One velocity region of weakened heat transfer was found. Moreover, TBAB CHS was treated as a kind of Bingham fluids, and the influences of the solid particles, flow velocity and types of flow on the forced convective heat transfer coefficients of TBAB CHS were investigated. At last, criterial correlations of Nusselt number for laminar and turbulent flows in the form of power function were summarized, and the error with experimental results was within +/-20%.

Field of study: Engineering
Emerging Markets Commerce: The Role of Country-of-Origin and Animosity in Purchase Intention

At present, firms must face interrelated challenges in global marketing, such as the increased consumer market internationalization and the rapid growth of emerging markets economy. In this context, the purpose of this study is to differentiate between cognitive and affective components of the country–of-origin (reputation of firms from a country–of-origin and animosity) and frame them as antecedents of trust and purchase intention. The study supports the view that the reputation of firms from the country–of-origin helps to engender trust in international markets and indirectly impacts purchase intention. Also, this study analyses the mediation role that trust plays in the relationship between reputation of firms from the country–of-origin, consumer animosity and purchase intention.

Field of study: Business
Laser ablation U-series analysis of fossil bones and teeth

Over the past decade, we have applied laser ablation ICP mass spectrometry U-series analysis to a large number of bones and teeth. The method is fast and provides high-resolution data of U-series isotopes, which give insights into the complexity of uranium migration into, within and out of bones. In this paper, we present our laser ablation approach in detail, from the experimental set up, to data reduction and uranium diffusion modelling. Laser ablation analysis can now be applied with minimum damage. Complete diffusion data sets can be obtained by laser drilling which leaves a hole of around 200 μm in diameter and 1–2 mm depth. If the natural U-diffusion follows a simple single-stage process, valuable age information can be obtained. In other cases, highly complex U-migrations have been observed, which make any age assessment impossible. Two examples from Wadjak and Callao illustrate the potential of nearly non-destructive laser ablation U-series analysis of human skeletal tissues. The results demonstrate the physical presence of modern humans in south-east Asia at a time when our species just started to migrate into Europe.

Field of study: Environmental science, Geography
Zur Kenntnis des Selenphotoelements IV. Verhalten bei tiefer Temperatur

ZusammenfassungDie Arbeit stellt einen weiteren experimentellen Beitrag zur Enthüllung der elementaren Vorgänge im Selenphotoelement dar. Sie verfolgt im besonderen von verschiedenen Seiten den eigenartigen Temperatureinfluß, der in einer vorhergehenden Untersuchung festgestellt werden konnte, und sucht die Mannigfaltigkeit der hierhergehörigen Erscheinungen einheitlich zusammenzufassen. Es ergeben sich gewisse allgemeine, von den Besonderheiten der einzelnen Elemente unabhängige Eigenschaften, die als charakteristische Merkmale des photoelektrischen bzw. stofflichen Verhaltens des Selenphotoelements erscheinen und daher für das theoretische Verständnis desselben bedeutungsvoll sind.

Field of study: Physics
Preparation of Nanosheets by Ultrasonic Exfoliation with the Aid of Surfactant Poly(vinylpyrrolidone)

Using poly(vinylpyrrolidone) (PVP) as a stabilizing agent graphite nanosheets (GNs) and molybdenum disulfide nanosheets (MNs) were conveniently obtained under ultrasound treatment. The two kinds of...

Field of study: Chemistry
Perirhinal cortex inactivation produces retrieval deficits in fear extinction to a discontinuous visual stimulus.

Several studies suggest that the perirhinal cortex (PER) may function to unitize stimulus components across time or modalities. While the PER has been shown to be critical for fear acquisition to discontinuous stimuli, the role of the PER in fear extinction memory has not been evaluated. The current study assessed the involvement of the PER during fear extinction training to a continuous or discontinuous conditioned stimulus (CS). Rats were randomly assigned to 1 of 4 groups based on 2 factors: the CS type (a continuous or discontinuous light) and a pretesting PER manipulation (muscimol inactivation or saline). Results showed that PER inactivation impaired fear memory to both CS types; however, PER inactivation had only impaired extinction memory to the discontinuous light. These results suggest the role of the PER in stimulus unitization extends to supporting the acquisition of fear extinction memory.

Field of study: Biology, Psychology
On $q$-series for principal characters of standard $A_2^{(2)}$-modules

We present sum-sides for principal characters of all standard (i.e., integrable and highest-weight) irreducible modules for the affine Lie algebra $A_2^{(2)}$. We use modifications of five known Bailey pairs; three of these are sufficient to obtain all the necessary principal characters. We then use the technique of Bailey lattice appropriately extended to include "out-of-bounds" values of one of the parameters, namely, $i$. We demonstrate how the sum-sides break into six families depending on the level of the modules modulo 6, confirming a conjecture of McLaughlin--Sills.

Field of study: Mathematics
Internationalization and the construction of world class universities:A case study of Tsinghua University

Internationalization is one of the inevitable elements to construct a world class university.It has been embedded in the development of Tsinghua University in student international flowing,faculty international standard,internationalization of teaching and curriculum,international cooperation in research and collaboration in education,but there are also certain problems.Internationalization is one of the essential strategies for developing countries to cater to the trend of economic globalization and international competition,therefore a fundamental path for those developing countries to construct world class universities.However,it still requires further consideration and efforts to pursuit the localization of these universities in the process of internationalization.

Field of study: Education
Numerical Simulation of Cooling Process for Hot Forming Ultrahigh Strength Steel

In view of the cooling pipe arrangement in hot forming die cooling system,a hot forming finite element model for ultra high strength steel was estabilished,and the hot stamping was simulated using ABAQUS,the influence of forming speed and holding pressure time on the cooling was mainly analyzed.The simulation results show that,the faster the forming speed,the smaller the deformation resistance and maximum temperature difference of sheet.It is not so that the longer holding pressure time,the better the results during cooling.The results provide the reference for the similar steel plate when choosing hot forming process parameters.

Field of study: Materials science
When shooting a coyote kills a wolf: Mistaken identity or misguided management?

The recovery of wolf populations in the United States (U.S.) is hampered by ongoing human-wolf conflicts. In particular, the illegal killing of grey wolves (Canis lupus), red wolves (Canis rufus), and Mexican wolves (Canis lupus baileyi) protected under the U.S. Endangered Species Act has contributed to relatively high mortality rates in some areas. One issue is that wolves are often mistaken as coyotes (Canis latrans) and illegally shot by hunters. To minimise cases of mistaken identity, stricter regulation of coyote hunting is being adopted in some areas where endangered wolves exist. Here we argue that such management should be adopted more widely, and especially in areas where wolves are at low densities or recolonising new areas. Such a proposal may face opposition, particularly where coyote hunting is common, or where coyotes are perceived as a threat to human enterprises such as livestock ranching. Appropriate education and training is needed to ensure that the public is aware that (i) wolves and coyotes are difficult to distinguish from a distance and (ii) coyotes are far too resilient to be affected by most periodic eradication programs, let alone from derbies or recreational hunting. We conclude that recreational hunting of coyotes could restrict wolf recolonisation while providing little benefit to animal agriculture. Consideration of new management strategies is therefore required to assist with wolf restoration efforts and to minimise ongoing human-wildlife conflicts.

Field of study: Environmental science
A Simple Voltage Controlled Oscillator Using Bootstrap Circuits and NOR-RS Flip Flop

This paper presents a simple and successful design for a voltage controlled oscillator. The proposed circuit is based on the use of two identical bootstrap circuits and a NOR-RS Flip Flop to generate wide-tunable sawtooth and square waves. Increasing control voltage linearly increases the output oscillation frequency. Experimental results verifying the performances of the proposed circuit are in agreement with the calculated values.

Field of study: Computer science
Can the Communion of Saints Help the Search for Justice in Dying well (Enough), “In Abraham's Arms, Where Lazarus is Poor no Longer”?

How can we practice dying in community? What communal practices nourish positive acts that make dying well (enough)—more than prudent caution in avoiding causing death (killing)? What part of our common ecclesial life as Catholics enables us to accompany dying persons as a gracious return to God? We are twice haunted: most first world deaths result from foreseen end-stage illnesses; mortality is less feared than burdensomeness for caregivers from vulnerable dependence. Of those who die in the hospital, many deaths result from decisions to withhold and withdraw treatments. From ten kinds of desolation about dying, ten parallel consolations are discerned in hopes and outcomes-based best practices.

Field of study: Medicine, Philosophy
Transverse hydrodynamics with sudden isotropization and freeze-out

We assume that the early evolution of matter produced in relativistic heavy-ion collisions is described by the transverse hydrodynamics. In this approach only transverse degrees of freedom are thermalized, while the longitudinal motion is described by free streaming. When the energy density of the system drops to a certain value, the system becomes isotropic (locally, in the momentum space) and freezes out. The sudden isotropization transition is described with the help of the Landau matching conditions, and the freeze-out is modeled with THERMINATOR. Within this scenario one is able to reproduce in the quite satisfactory way the transverse-momentum spectra, the elliptic flow coefficient v2, and the HBT radii of pions and kaons studied at RHIC (Au+Au collisions at the top beam energy). The obtained results indicate that the system produced at RHIC does not have to be fully thermalized in the early stage. On the other hand, the final three-dimensional thermalization is necessary to reproduce the HBT radius Rlong.

Field of study: Physics