Comparing the scatter of citing and cited literature

Using the subjects desalination and educational psychology, the scatter of periodical articles over periodical titles was compared at two levels, the second level being a random sample of periodical articles cited by the first level. Several measures were used to compare the extent of scatter at the two levels. Some methods commonly used in bibliometrics produced conflicting evidence on whether the citing literature (first-level) or the cited (second-level) was more scattered. A computer-intensive sampling procedure, known as the Bootstrap method, was then used to estimate the scatter of the total cited population from the scatter of the empirical sample. Cumulative distributions were prepared to show what percentage of periodicals accounted for various percentages of articles at each level of scatter. Only at the 90th percentile of articles did the percentage of periodical titles in the cited literature significantly exceed that of the citing literature. At the tail-end of the Bradford-type distribution, the cited literature appears to be more scattered than the literature citing it.     

The simultaneous scaling of cited and citing articles in a common space

Scientific articles may be represented as points in a space whose spatial pattern reflects some of the substantive and social structures of science. The proximity of articles and the documents they reference leads to a centroid scalling method proposed in this paper. This method scales citing articles as close as possible to the articles they reference. The simultaneous scaling of citing and cited articles in a common space aids in the interpretation of the resultant configuration.     

A quantitative exploration on reasons for citing articles from the perspective of cited authors

Citation is regarded as one of the “norms of science” (Merton in Am Sociol Rev 22(6):635–659, 1957) and is deeply researched by the field of scientometrics. The motivations authors have for citing one another are considered significant and have been the subject of extensive qualitative research such as content analysis, questionnaires, and interviews of citing authors. However, the existing qualitative studies have covered a limited number of samples. To expand the dataset, this paper proposes a quantitative method applied to detecting citation reasons from the angle of citation networks and the attributes of cited authors, including their publication count (the number of single-authored publications, collaborative and first-authored publications as well as collaborative but non-first-authored publications, and number of whole publications), citation count, research topic interests, and gender. By applying the Exponential Random Graph Models (ERGMs), the current study revealed that authors in the field of information retrieval tend to cite those with more single-authored, collaborative and first-authored, and collaborative but not first-authored publications. Besides, in this field, the number of publications, similar topical domains, and same gender are proven to be significantly favorable in selecting references in our experiment.     

Exploring the analytical potential of NMR spectroscopy in chiral anisotropic media for the study of the natural abundance deuterium distribution in organic molecules

The deuterium/hydrogen (D/H)(i) ratio measurement by quantitative (2)H NMR spectroscopy is a method of choice for the analysis of kinetic isotopic effects associated with enzyme-catalyzed reactions during a biosynthetic pathway. However, the efficiency of the current isotropic (2)H-[(1)H] NMR can be limited by the rather small chemical shift dispersion of deuterium nuclei. In addition, this method does not allow the enantiotopic deuterons in prochiral molecules to be spectrally discriminated, hence precluding the quantification of isotopic fractionation on methylene prostereogenic sites. In this work, we explore another analytical strategy able to circumvent these disadvantages. This approach is based on the use of natural abundance (2)H 2D NMR experiments on solutes embedded in polypeptidic, chiral liquid crystalline solvent. Thus, we show that NMR in these oriented phases is a powerful way to separate deuterium signals on the basis of the quadrupolar interactions, providing a promising alternative to overcrowded (2)H NMR spectra obtained in liquid state. To illustrate our purpose, we have experimentally investigated the case of 1,1'-bis(phenylthio)hexane derived by cleavage from methyl linoleate of safflower. The (2)H NMR results in chiral liquid crystals are presented and discussed. We show, for the first time, that (D/H)(pro-R) and (D/H)(pro-S) can be measured at the same methylene position of a fatty acid chain.     

Exploring the circularity potential regarding the multiple use of residual material

Clean Technologies and Environmental Policy - Building on recent insights in exploring material circularity, this study attempts to develop a methodological approach toward allocating an available...     

An analytical model and tomographic calculation of vacuum electron beam welding heat source

According to the analysis to the characteristics of welding heat source and thermal effect, a mathematic model of rotary Gaussian body heat source with incremental power-density-distribution was developed, which was in line with the characteristics of heat source during vacuum electron beam welding. The affecting radius of source model decreases progressively with the law of Gaussian function and the power density varies gradually with the law of exponential function in depth direction. The evaluation of peak-power-density coefficient β and the tomographic calculation of the source model in different focused conditions were discussed. The results showed that the focused conditions, which were the deviation of depth of field in electron beam, were dependent on the coefficient β in the source model. Simulation of thermal effect and the analysis of weld formation in vacuum electron beam welding validated the feasibility of the model.     

Kernel-based parametric analytical model of source intensity distributions in lithographic tools

This paper proposes a parametric analytical source model for overall representation of the physical distribution property of partially coherent illumination sources in lithographic tools. A set of smooth kernels is adopted to construct the analytical model for the multiple mainstream illumination sources. Corrected parametrical terms are subsequently presented for characterization of different physical distortions of and deviations from actual illumination sources. The corrected parametrical terms can be decomposed into Fourier series, which have special physical meanings of respectively indicating different distortion types, including shift of the center, tilt, and ellipticity, etc. We fully expected that the proposed analytical model will provide both simulation conditions and a theoretical basis for the resolution enhancement technique and related research fields.     

On the analytical solution of a nonstationary kinetic equation for a point heat source

A nonstationary kinetic equation for a point heat source in a gas is analytically solved. The dependence of the temperature and concentration of gas molecules on the distance from the source is considered. The results are compared to experimental data on the spreading of acoustic oscillations.     

利用鱼的活动电位监测原水有毒物质

本方法是利用鱼类对有毒物质进入水体后引起活动电位变化,来自动连续监测水质的情况。以鱼在水中活动时产生的活动电位作为数学变量,根据其在正常情况下和有毒物质污染情况下的变化,应用计算机技术对该变量进行连续采集、运算、分析处理、控制,从而达到连续监测、及时自动预警、报警、采样的作用。     

A fourth-order plastic potential for anisotropic metals and its analytical calculation from the texture function

Summary A fourth-order potential is proposed for anisotropic metals, assuming orthotropic symmetry. It may be used as a yield criterion, but here it is used as a dual potential depending on the strain-rate. The concept of dual potential is recalled and the implementation in simulation codes is discussed, along with the extension to viscoplasticity. The coefficients depend linearly on the texture coefficients, up to a scale factor determinable by one mechanical test. The adjustment of the dual potential from texture data is numerically tested for steels, and compared with mechanical tests. A significant improvement of the flow rule (strain ratio R) is obtained as compared with both the Taylor model and the texture-adjusted Hill criterion. The predicted stress ratios are close to those predicted with the latter criterion, which were previously found to be in a good experimental agreement.     

Nanohydroxyapatite shape and its potential role in bone formation: an analytical study

Bone cells (osteoblasts) produce a collagen-rich matrix called osteoid, which is mineralized extracellularly by nanosized calcium phosphate (CaP). Synthetically produced CaP nanoparticles (NPs) have great potential for clinical application. However few studies have compared the effect of CaP NPs with different properties, such as shape and aspect ratio, on the survival and behaviour of active bone-producing cells, such as primary human osteoblasts (HOBs). This study aimed to investigate the biocompatibility and ultrastructural effects of two differently shaped hydroxyapatite [Ca₁₀(PO₄)₆(OH)₂] nanoparticles (HA NPs), round- (aspect ratio 2.12, AR2) and rice-shaped (aspect ratio 3.79, AR4). The ultrastructural response and initial extracellular matrix (ECM) formation of HOBs to HA NPs were observed, as well as matrix vesicle release. A transmission electron microscopy (TEM)-based X-ray microanalytical technique was used to measure cytoplasmic ion levels, including calcium (Ca), phosphorus (P), sodium (Na) and potassium (K). K/Na ratios were used as a measure of cell viability. Following HA NP stimulation, all measured cytoplasmic ion levels increased. AR2 NPs had a greater osteogenic effect on osteoblasts compared with AR4 NPs, including alkaline phosphatase activity and matrix vesicle release. However, they produced only a moderate increase in intracellular Ca and P levels compared with AR4. This suggests that particular Ca and P concentrations may be required for, or indicative of, optimal osteoblast activity. Cell viability, as measured by Na and K microanalysis, was best maintained in AR2. Initial formation of osteoblast ECM was altered in the presence of either HA NP, and immuno-TEM identified fibronectin and matrilin-3 as two ECM proteins affected. Matrilin-3 is here described for the first time as being expressed by cultured osteoblasts. In summary, this novel and in-depth study has demonstrated that HA NP shape can influence a range of different parameters related to osteoblast viability and activity.     

The citing practices of the authors to the national journals in mathematics,physics, and chemistry

In this essentially empirical study a comparative analysis of the age of references in scientific papers in three subject fields is performed. Comparisons are made: 1. among national and leading journals in the same scientific field, 2. for a number of high quality journals in physics and chemistry, and 3. between several groups of authors (according to the countries of origin), contributing to the same journals in chemistry. Variations found in the journals citing half-life values suggest that, if properly interpreted, the citing half-life might reflect the journal's quality and might serve as a certain indicator for the citing practices of specific groups of authors.     

Plasma potential distribution in tandem surface-plasma source of negative ions

We have experimentally studied the potential distribution in hydrogen plasma and measured its density and electron temperature in the tandem involving a circular multicusp magnetic trap and a positive-to-negative ion convertor. It is confirmed that the plasma potential in the circular trap is lower than the chamber wall potential. It is established that plasma potential in the ion convertor is virtually independent of the convertor potential in the working range.     

Increased analytical precision in the hollow cathode discharge emission source by improved discharge current control.

A significant improvement in the precision of the hollow cathode as an emission source is reported. Precision of 1% or less has been observed several times over periods of several hours. An average long-term stability of 4.3% for Ll and 6.0% for Na in the emission signal from microsamples (less than 50 nL) deposited in the hollow cathode discharge source is reported. The improved precision is attributed primarily to the introduction of electronics that hold the discharge current more nearly constant and to the shielding of all wiring to the source from the power supply. A current-controlled switch that is capable of driving a hollow cathode discharge in either dc or pulsed mode is described. This switch is capable of generating current pulses as short as 2 microseconds through a resistive load and greatly improves the discharge stability and repeatability at turn-on in both the dc and pulsed modes. The characteristics of pulses produced by this switch are presented; however, analytical performance is reported only for the dc mode. Temporal current plots are presented for the new instrumentation and compared to plots taken with commonly used current-controlled power supplies. Instrumentation, operation, and sample preparation procedures are described. Typical temporal profiles of the emission signal from microsamples deposited in AI and stainless steel hollow cathodes are given.     

Effect of aging the hollow cathode by sputtering on the analytical precision of the hollow cathode discharge emission source.

Sputtering changes the analytical performance of the hollow cathode as an emission source. Proper conditioning (aging) of the hollow with sputtering greatly improves precision. Conditioning decreases the blank emission signal and changes the shape of the hollow. Micrographs which show the evolution of the bottom of the hollow into a stable bulb shape are presented. The blank emission signal decreases with aging of the hollow and approaches a constant value when the hollow is properly conditioned. A short-term stability (n = 5) of approximately 1.8% RSD has been observed frequently. An average long-term stability over several days (n = 45) of 4.5% for Li and 3.5% for Na in the emission signal from microsamples (less than 50 nL) deposited in the hollow cathode discharge source is reported here. Instrumentation, operation, and sample preparation procedures are described.     

Highly cited old papers and the reasons why they continue to be cited. Part II., The 1953 Watson and Crick article on the structure of DNA

Reports the results of a citation study on Watson and Crick's 1953 paper announcing the discovery of the double helix structure of DNA. The paper has been cited more than 2,000 times since 1961, and there is no sign of any obsolescence to this article. An analysis was undertaken of the journals in which the citations appeared, and of mistakes in the bibliographic citations provided by citing articles. Watson and Crick themselves have only cited their own paper twice since 1961. An analysis was also undertaken of the reasons why the paper was cited; 100 citing articles were identified and read. The reasons for citing were then categorised using the Oppenheim and Renn method. Compared to earlier studies, it was found that a greater proportion of citations were for historical reasons, a smaller proportion of citing articles were actively using the Watson and Crick article, and a similar, but low proportion were criticising the Watson and Crick article. This revised version was published online in June 2006 with corrections to the Cover Date.     

The Social Physique Anxiety Scale: an example of the potential consequence of negatively worded items in factorial validity studies

Social physique anxiety (SPA) based on Hart, Leary, and Rejeski's (1989) Social Physique Anxiety Scale (SPAS) was originally conceptualized to be a unidimensional construct. Empirical evidence on the factorial validity of the SPAS has been contradictory, yielding both one- and two-factor models. The two-factor model, which consists of separate factors associated with positively and negatively worded items, has stimulated an ongoing debate about the dimensionality and content of the SPAS. The present study employed confirmatory factor analysis (CFA) to examine whether the two-factor solution to the 12-item SPAS was substantively meaningful or a methodological artifact. Results of the CFAs, which were performed on responses from four different samples (Eklund, Kelley, and Wilson, 1997; Eklund, Mack, and Hart, 1996), supported the existence of a single substantive SPA factor underlying responses to the 12-item SPAS. There were, in addition, method effects associated with the negatively worded items that could be modeled to achieve good fit. Therefore, it was concluded that a single substantive factor and a non-substantive method effect primarily related to the negatively worded items best represented the 12-item SPAS.     

The potential of a Rankine source between parallel planes and in a rectangular cylinder

When using the boundary element method to compute a potential field, the computations can be substantially reduced if the Green function implicitly satisfies some of the boundary conditions. This savings will be achieved at the expense of having to compute a more complicated Green function. This paper presents efficient formulae for computing the Green functions needed to solve the Laplace equation in domains bounded by a pair of parallel planes or an infinite rectangular cylinder. For both cases, an ascending power series is derived for the region close to the fundamental Rankine source, and a classical eigenfunction expansion is used in the complementary region.This work was performed while the author was a postdoctoral researcher in the Ocean Engineering Department of the Massachusetts Institute of Technology     

Effect on the journal impact factor of the number and document type of citing records: a wide-scale study

We studied the effect on journal impact factors (JIF) of citations from documents labeled as articles and reviews (usually peer reviewed) versus citations coming from other documents. In addition, we studied the effect on JIF of the number of citing records. This number is usually different from the number of citations. We selected a set of 700 journals indexed in the SCI section of JCR that receive a low number of citations. The reason for this choice is that in these instances some citations may have a greater impact on the JIF than in more highly-cited journals. After excluding some journals for different reasons, our sample consisted of 674 journals. We obtained data on citations that contributed to the JIF for the years 1998?C2006. In general, we found that most journals obtained citations that contribute to the impact factor from documents labeled as articles and reviews. In addition, in most of journals the ratio between citations that contributed to the impact factor and citing records was greater than 80% in all years. Thus, in general, we did not find evidence that citations that contributed to the impact factor were dependent on non-peer reviewed documents or only a few citing records.