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Bibliometric Analysis for Papers on Topics Related to Pollution Prevention (P2)
March 29, 2005

This is a bibliometric analysis of the papers prepared by intramural and extramural researchers of the U.S. Environmental Protection Agency (EPA) on topics related to pollution prevention (P2). For this analysis, 509 papers were reviewed. These 509 papers, published from 1995 to 2005, were cited 8,277 times in the journals covered by Thomson’s Web of Science1. Of these 509 papers, 401 (79%) have been cited at least once in a journal.

The analysis was completed using Thomson’s Essential Science Indicators (ESI) and Journal Citation Reports (JCR) as benchmarks. ESI provides access to a unique and comprehensive compilation of essential science performance statistics and science trends data derived from Thomson’s databases. The chief indicators of output, or productivity, are journal article publication counts. For influence and impact measures, ESI employs both total citation counts and cites per paper scores. The former reveals gross influence while the latter shows weighted influence, also called impact. JCR presents quantifiable statistical data that provide a systematic, objective way to evaluate the world’s leading journals and their impact and influence in the global research community.

Summary of Analysis

More than one-third of the P2 publications are highly cited papers. A review of the citations indicates that 174 (34.2%) of the P2 papers qualify as highly cited when using the ESI criteria for the top 10% of highly cited publications. Thirty-one (6.1%) of the P2 papers qualify as highly cited when using the criteria for the top 1%. Nine (1.8%) of these papers qualify as very highly cited (in the top 0.1%), and two papers actually meet the top 0.01% threshold.

The P2 papers are more highly cited than the average paper. Using the ESI average citation rates for papers published by field as the benchmark, in 8 of the 12 fields in which the EPA P2 papers were published, the ratio of actual to expected cites is greater than 1, indicating that the P2 papers are more highly cited than the average papers in those fields.

Nearly one-third of the P2 papers are published in very high impact journals. One-hundred fifty-five (155) of 509 papers were published in the top 10% of journals ranked by JCR Impact Factor, representing 30.4% of EPA’s P2 papers. Nearly one-third of the P2 papers are published in the top 10% of journals ranked by JCR Immediacy Factor. One-hundred fifty-seven (157) of the 509 papers appear in the top 10% of journals, representing 30.8% of EPA’s P2 papers.

Twelve of the P2 papers qualify as hot papers. Using the hot paper thresholds established by ESI as a benchmark, 12 hot papers, representing 2.4% of the P2 papers, were identified in the analysis.

The author self-citation rate is below average. Three-hundred sixty-four (364) of the 8,277 cites are author self-cites. This 4.4% author self-citation rate is below the accepted range of 10-30% author self-citation rate.

Highly Cited P2 Publications

The 509 P2 papers reviewed for this analysis covered 12 of the 22 ESI fields. The distribution of the papers among these 12 fields and the number of citations by field are presented in Table 1.

Table 1. P2 Papers by ESI Fields

No. of Citations

ESI Field

No. of EPA P2 Papers

Average Cites/Paper

6,099

Chemistry

317

19.24

1,358

Engineering

92

14.76

258

Biology & Biochemistry

28

9.21

215

Multidisciplinary

1

215.00

102

Environment/Ecology

27

3.78

83

Materials Science

26

3.19

80

Computer Science

8

10.00

40

Economics & Business

2

20.00

36

Physics

3

12.00

4

Mathematics

2

2.00

1

Pharmacology & Toxicology

2

0.50

1

Social Science, general

1

1.00

Total = 8,277

 

Total = 509

 

There were 174 (34.2% of the papers analyzed) highly cited EPA P2 papers in 9 of the 12 fields—Chemistry, Engineering, Multidisciplinary, Biology & Biochemistry, Computer Science, Economics & Business, Materials Science, Physics, and Environment/Ecology—when using the ESI criteria for the top 10% of papers. Table 2 shows the number of EPA papers in those 9 fields that met the top 10% threshold in ESI. Thirty-one (6.1%) of the papers analyzed qualified as highly cited when using the ESI criteria for the top 1% of papers. These papers covered three fields—Chemistry, Engineering, and Multidisciplinary. Table 3 shows the 31 papers by field that met the top 1% threshold in ESI. There were nine very highly cited EPA P2 papers in two fields—Chemistry and Engineering. These nine papers met the top 0.1% threshold in ESI (1.8% of the papers analyzed). Two of these nine P2 papers actually met the top 0.01% threshold in ESI (i.e., the papers by Savage and Blanchard).

Table 2. Number of Highly Cited P2 Papers by Field (top 10%)

Citations

ESI Field

No. of Papers

Average Cites/Paper

% of EPA Papers in Field

4,837

Chemistry

113

42.80

35.65%

1,282

Engineering

43

29.81

46.74%

215

Multidisciplinary

1

215.00

100.00%

102

Biology & Biochemistry

3

34.00

10.71%

72

Computer Science

6

12.00

75.00%

27

Economics & Business

1

27.00

50.00%

26

Materials Science

5

5.20

19.23%

19

Physics

1

19.00

33.33%

1

Environment/Ecology

1

1.00

3.70%

 

Total =

174

   

Table 3. Number of Highly Cited P2 Papers by Field (top 1%)

Citations

ESI Field

No. of Papers

Average Cites/Paper

% of EPA Papers in Field

2,188

Chemistry

19

115.16

5.99%

838

Engineering

11

76.18

11.96%

215

Multidisciplinary

1

215.00

100.00%

 

Total =

31

   

The citations for the highly cited papers in the top 1% are presented in Tables 4 through 6. The citations for the very highly cited papers (top 0.1%) are listed in Table 7.

Table 4. Highly Cited P2 Papers in the Field of Chemistry(top 1%)

No. of Cites

First Author

Paper

296

Li CJ

Aqueous Barbier-Grignard type reaction: scope, mechanism, and synthetic applications. Tetrahedron 1996;52(16):5643-5668.

83

Mesiano AJ

Supercritical biocatalysis. Chemical Reviews 1999;99(2):623-633.

119

Hudlicky T

Enzymatic dihydroxylation of aromatics in enantioselective synthesis: expanding asymmetric methodology. Aldrichimica Acta 1999;32(2):35-62.

152

Matyjaszewski K

Transition metal catalysis in controlled radical polymerization: atom transfer radical polymerization. Chemistry–A European Journal 1999;5(11):3095-3102.

190

Patten TE

Copper(I)-catalyzed atom transfer radical polymerization. Accounts of Chemical Research 1999;32(10):895-903.

293

Li CJ

Organic syntheses using indium-mediated and catalyzed reactions in aqueous media. Tetrahedron 1999;55(37):11149-11176.

380

Varma RS

Solvent-free organic syntheses – using supported reagents and microwave irradiation. Green Chemistry 1999;1(1):43-55.

42

Varma RS

An expeditious solvent-free route to ionic liquids using microwaves. Chemical Communications 2001;7:643-644.

66

Varma RS

Solvent-free accelerated organic syntheses using microwaves. Pure and Applied Chemistry 2001;73(1):193-198.

81

Blanchard LA

High-pressure phase behavior of ionic liquid/CO 2 systems. Journal of Physical Chemistry B 2001;105(12):2437-2444.

236

Huddleston JG

Characterization and comparison of hydrophilic and hydrophobic room temperature ionic liquids incorporating the imidazolium cation. Green Chemistry 2001;3(4):156-164.

31

Li CJ

Quasi-nature catalysis: developing C-C bond formations catalyzed by late transition metals in air and water. Accounts of Chemical Research 2002;35(7):533-538.

33

Li CJ

Highly efficient Grignard-type imine additions via C-H activation in water and under solvent-free conditions. Chemical Communications 2002;3:268-269.

51

Varma RS

Clay and clay-supported reagents in organic synthesis. Tetrahedron 2002;58(7):1235-1255.

57

Wei CM

Enantioselective direct-addition of terminal alkynes to imines catalyzed by copper(I)pybox complex in water and in toluene. Journal of the American Chemical Society 2002;124(20):5638-5639.

18

Holbrey JD

Crystal polymorphism in 1-butyl-3-methylimidazolium halides: supporting ionic liquid formation by inhibition of crystallization. Chemical Communications 2003;14:1636-1637.

20

Kaar JL

Impact of ionic liquid physical properties on lipase activity and stability. Journal of the American Chemical Society 2003;125(14):4125-4131.

32

Swatloski RP

Ionic liquids are not always green: hydrolysis of 1-butyl-3-methylimidazolium hexafluorophosphate. Green Chemistry 2003;5(4):361-363.

8

Li ZG

Three-component coupling of aldehyde, alkyne, and amine catalyzed by silver in ionic liquid. Tetrahedron Letters 2004;45(11):2443-2446.

Table 5. Highly Cited P2 Papers in the Field of Engineering (top 1%)

No. of Cites

First Author

Paper

405

Savage PE

Reactions at supercritical conditions – applications and fundamentals. AIChE Journal 1995;41(7):1723-1778.

45

Fan L

Supercritical-phase alkylation reaction on solid acid catalysts: mechanistic study and catalyst development. Industrial & Engineering Chemistry Research 1997;36(5):1458-1463.

47

Chandler K

Alkylation reactions in near-critical water in the absence of acid catalysts. Industrial & Engineering Chemistry Research 1997;36(12):5175-5179.

37

Hua JZ

Enhanced interval analysis for phase stability: Cubic equation of state models. Industrial & Engineering Chemistry Research 1998;37(4):1519-1527.

47

Clancy JL

UV light inactivation of Cryptosporidium oocysts. Journal American Water Works Association 1998;90(9):92-102.

55

Bukhari Z

Medium-pressure UV for oocyst inactivation. Journal American Water Works Association 1999;91(3):86-94.

26

Taylor JD

Experimental measurement of the rate of methyl tert-butyl ether hydrolysis in sub- and supercritical water. Industrial & Engineering Chemistry Research 2001;40(1):67-74.

121

Blanchard LA

Recovery of organic products from ionic liquids using supercritical carbon dioxide. Industrial & Engineering Chemistry Research 2001;40(1):287-292.

31

Visser AE

Task-specific ionic liquids incorporating novel cations for the coordination and extraction of Hg 2+ and Cd 2+: synthesis, characterization, and extraction studies. Environmental Science & Technology 2002;36(11):2523-2529.

18

Abraham MH

Some novel liquid partitioning systems: water-ionic liquids and aqueous biphasic systems. Industrial & Engineering Chemistry Research 2003;42(3):413-418.

6

Suh S

System boundary selection in life-cycle inventories using hybrid approaches. Environmental Science & Technology 2004;38(3):657-664.

Table 6. Highly Cited P2 Papers in the Field of Multidisciplinary (top 1%)

No. of Cites

First Author

Paper

215

Blanchard LA

Green processing using ionic liquids and CO 2. Nature 1999;399(6731):28-29.

Table 7. Very Highly Cited P2 Papers (Top 0.1%)

Field

No. of Cites

First Author

Paper

Chemistry

190

Patten TE

Copper(I)-catalyzed atom transfer radical polymerization. Accounts of Chemical Research 1999;32(10):895-903.

 

293

Li CJ

Organic syntheses using indium-mediated and catalyzed reactions in aqueous media. Tetrahedron 1999;55(37):11149-11176.

 

380

Varma RS

Solvent-free organic syntheses – using supported reagents and microwave irradiation. Green Chemistry 1999;1(1):43-55.

 

236

Huddleston JG

Characterization and comparison of hydrophilic and hydrophobic room temperature ionic liquids incorporating the imidazolium cation. Green Chemistry 2001;3(4):156-164.

Engineering

405

Savage PE 2

Reactions at supercritical conditions – applications and fundamentals. AIChE Journal 1995;41(7):1723-1778.

Engineering

121

Blanchard LA2

Recovery of organic products from ionic liquids using supercritical carbon dioxide. Industrial & Engineering Chemistry Research 2001;40(1):287-292.

 

31

Visser AE

Task-specific ionic liquids incorporating novel cations for the coordination and extraction of Hg 2+ and Cd 2+: synthesis, characterization, and extraction studies. Environmental Science & Technology 2002;36(11):2523-2529.

 

18

Abraham MH

Some novel liquid partitioning systems: water-ionic liquids and aqueous biphasic systems. Industrial & Engineering Chemistry Research 2003;42(3):413-418.

 

6

Suh S

System boundary selection in life-cycle inventories using hybrid approaches. Environmental Science & Technology 2004;38(3):657-664.

Ratio of Actual Cites to Expected Citation Rates

The expected citation rate is the average number of cites that a paper published in the same journal in the same year and of the same document type (article, review, editorial, etc.) has received from the year of publication to the present. Using the ESI average citation rates for papers published by field as the benchmark, in 8 of the 12 fields in which the EPA P2 papers were published, the ratio of actual to expected cites is greater than 1, indicating that the EPA papers are more highly cited than the average papers in those fields (see Table 8).

Table 8. Ratio of Average Cites to Expected Cites for P2 Papers by Field

ESI Field

Total Cites

Expected Cite Rate

Ratio

Chemistry

6,099

2,023.23

3.01

Engineering

1,358

220.45

6.16

Biology & Biochemistry

258

243.53

1.06

Multidisciplinary

215

4.87

44.15

Environment/Ecology

102

130.29

0.78

Materials Science

83

92.2

0.90

Computer Science

80

20.12

3.98

Economics & Business

40

11.24

3.56

Physics

36

20.91

1.72

Mathematics

4

2.75

1.45

Pharmacology & Toxicology

1

19.94

0.05

Social Science, general

1

3.07

0.03

JCR Benchmarks

The Impact Factor is a well known metric in citation analysis. It is a measure of the frequency with which the average article in a journal has been cited in a particular year. The Impact Factor helps evaluate a journal’s relative importance, especially when compared to others in the same field. The Impact Factor is calculated by dividing the number of citations in the current year to articles published in the 2 previous years by the total number of articles published in the 2 previous years.

Table 9 indicates the number of P2 papers published in the top 10% of journals, based on the JCR Impact Factor. One-hundred fifty-five (155) of 509 papers were published in the top 10% of journals, representing 30.4% of EPA’s P2 papers.

Table 9. P2 Papers in Top 10% of Journals by JCR Impact Factor

EPA P2 Papers in that Journal

Journal

Impact Factor

(IF)

JCR IF Rank

25

Green Chemistry

2.820

767

21

Journal of Organic Chemistry

3.297

573

19

Chemical Communications

4.031

376

16

Macromolecules

3.621

470

12

Journal of the American Chemical Society

6.516

174

10

Environmental Science & Technology

3.592

487

7

Organic Letters

4.092

368

4

Journal of Physical Chemistry B

3.679

454

4

Journal of Catalysis

3.276

581

4

Applied Catalysis A–General

2.825

764

3

Journal of Bacteriology

4.175

358

3

Langmuir

3.098

641

2

Accounts of Chemical Research

15.000

41

2

Chemistry of Materials

4.374

329

2

Chemistry–A European Journal

4.353

332

2

Applied Catalysis B-Environmental

3.476

523

2

Biomacromolecules

2.824

765

1

Nature

30.979

8

1

Chemical Reviews

21.036

23

1

Angewandte Chemie-International Edition

8.427

108

1

Advances in Catalysis

7.889

122

1

Aldrichimica Acta

7.077

151

1

Advances in Polymer Science

6.955

157

1

Analytical Chemistry

5.250

248

1

Journal of Medicinal Chemistry

4.820

278

1

International Review of Cytology – A Survey of Cell Biology

4.286

340

1

Applied and Environmental Microbiology

3.820

418

1

Advanced Synthesis & Catalysis

3.783

426

1

Environmental Health Perspectives

3.408

538

1

Metabolic Engineering

3.397

540

1

Inorganic Chemistry

3.389

544

1

Organometallics

3.375

546

1

Bioscience

3.266

584

1

Biotechnology Advances

2.875

739

Total = 155

     

Immediacy Index

The journal Immediacy Index is a measure of how quickly the average article in a journal is cited. It indicates how often articles published in a journal are cited within the year they are published. The Immediacy Index is calculated by dividing the number of citations to articles published in a given year by the number of articles published in that year.

Table 10 indicates the number of EPA papers published in the top 10% of journals, based on the JCR Immediacy Index. One-hundred fifty-seven (157) of the 509 papers appear in the top 10% of journals, representing 30.8% of EPA’s P2 papers.

Table 10. P2 Papers in Top 10% of Journals by JCR Immediacy Index

EPA P2 Papers in that Journal

Journal

Immediacy Index

(II)

JCR II Rank

35

Tetrahedron Letters

0.522

700

21

Journal of Organic Chemistry

0.716

425

19

Chemical Communications

0.783

375

16

Macromolecules

0.583

594

12

Journal of the American Chemical Society

1.212

168

7

Organic Letters

0.835

331

5

Synlett

0.607

563

4

Journal of Physical Chemistry B

0.582

595

4

Journal of Catalysis

0.514

721

3

Journal of Bacteriology

0.972

245

3

Current Organic Chemistry

0.674

471

3

Langmuir

0.523

694

2

Accounts of Chemical Research

2.168

69

2

Chemistry–A European Journal

0.935

268

2

New Journal of Chemistry

0.670

475

2

Chemistry of Materials

0.609

560

2

Journal of Chemical Information and Computer Sciences

0.567

612

1

Nature

6.679

6

1

Chemical Reviews

2.955

40

1

Angewandte Chemie-International Edition

1.655

106

1

Bioscience

1.205

169

1

Advanced Synthesis & Catalysis

1.135

186

1

Environmental Health Perspectives

0.869

304

1

Advances in Polymer Science

0.857

310

1

Journal of Medicinal Chemistry

0.817

342

1

Organometallics

0.716

425

1

Aldrichimica Acta

0.667

478

1

Annals of Occupational Hygiene

0.661

487

1

Analytical Chemistry

0.657

493

1

Inorganic Chemistry

0.623

546

1

Crystal Growth & Design

0.532

670

1

European Journal of Organic Chemistry

0.530

677

Total = 157

     

Hot Papers

ESI establishes citation thresholds for hot papers, which are selected from the highly cited papers in different fields, but the time frame for citing and cited papers is much shorter—papers must be cited within 2 years of publication and the citations must occur in a 2-month time period. Papers are assigned to 2-month periods and thresholds are set for each period and field to select 0.1% of papers. There were no hot papers identified for the current 2-month period (i.e., January-February 2005), but there were a number of hot papers identified from previous periods.

Using the hot paper thresholds established by ESI as a benchmark, 12 hot papers, representing 2.4% of the P2 papers, were identified in two fields—Chemistry and Engineering. The hot papers are listed in Table 11.

Table 11. Hot Papers Identified Using ESI Thresholds

Field

ESI Hot Papers Threshold

No. of Cites in 2-Month Period

Paper

Chemistry

8

11 cites in May-June 2003

Huddleston JG, Visser AE, et al. Characterization and comparison of hydrophilic and hydrophobic room temperature ionic liquids incorporating the imidazolium cation. Green Chemistry 2001;3(4):156-164.

   

10 cites in March-April 2001

Matyjaszewski K. Transition metal catalysis in controlled radical polymerization: atom transfer radical polymerization. Chemistry–A European Journal 1999;5(11):3095-3102.

   

10 cites in September-October 2000

Li CJ, Chan TH. Organic syntheses using indium-mediated and catalyzed reactions in aqueous media. Tetrahedron 1999;55(37):11149-11176.

   

10 cites in October-November 2001

Patten TE, Matyjaszewski K. Copper(I)-catalyzed atom transfer radical polymerization. Accounts of Chemical Research 1999;32(10):895-903.

   

9 cites in March-April 2004

Wei CM, Li CJ. Enantioselective direct-addition of terminal alkynes to imines catalyzed by copper(I)pybox complex in water and in toluene. Journal of the American Chemical Society 2002;124(20):5638-5639.

   

9 cites in August-September 2001

Hudlicky T, Gonzalez D, et al. Enzymatic dihydroxylation of aromatics in enantioselective synthesis: expanding asymmetric methodology. Aldrichimica Acta 1999;32(2):35-62.

   

8 cites in July-August 2004

Swatloski RP, Holbrey JD, et al. Ionic liquids are not always green: hydrolysis of 1-butyl-3-methylimidazolium hexafluorophosphate. Green Chemistry 2003;5(4):361-363.

   

8 cites in January-February 2001

Varma RS. Solvent-free organic syntheses – using support reagents and microwave irradiation. Green Chemistry 1999;1(1):43-55.

Engineering

4

9 cites in June-July 1996

Savage PE, Gopalan S, et al. Reactions at supercritical conditions – applications and fundamentals. AIChE Journal 1995;41(7):1723-1778.

   

4 cites in August-September 2004

Abraham MH, Zissimos AM, et al. Some novel liquid partitioning systems: water-ionic liquids and aqueous biphasic systems. Industrial & Engineering Chemistry Research 2003;42(3):413-418.

   

9 cites in May-June 2003

Blanchard LA, Brennecke JF. Recovery of organic products from ionic liquids using supercritical carbon dioxide. Industrial & Engineering Chemistry Research 2001;40(1):287-292.

   

4 cites in July-August 2002

Taylor JD, Steinfeld JI, et al. Experimental measurement of the rate of methyl tert-butyl ether hydrolysis in sub- and supercritical water. Industrial & Engineering Chemistry Research 2001;40(1):67-74.

Author Self-Citation

Self-citations are journal article references to articles from that same author (i.e., the first author). Because higher author self-citation rates can inflate the number of citations, the author self-citation rate was calculated for the P2 papers. Of the 8,277 total cites, 364 are author self-cites—a 4.4% author self-citation rate. Garfield and Sher3 found that authors working in research-based disciplines tend to cite themselves on the average of 20% of the time. MacRoberts and MacRoberts4 claim that approximately 10% to 30% of all the citations listed fall into the category of author self-citation. Therefore, the 4.4% self-cite rate for the P2 papers is below the range for author self-citation.

1 Thomson’s Web of Science provides access to current and retrospective multidisciplinary information from approximately 8,700 of the most prestigious, high impact research journals in the world. Web of Science also provides cited reference searching.

2 These papers also met the top 0.01% threshold in ESI.

3 Garfield E, Sher IH. New factors in the evaluation of scientific literature through citation indexing. American Documentation 1963;18(July):195-201.

4 MacRoberts MH, MacRoberts BR. Problems of citation analysis: a critical review. Journal of the American Society of Information Science 1989;40(5):342-349.

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