The Securities and Exchange Commission has not necessarily reviewed the information in this filing and has not determined if it is accurate and complete.
The reader should not assume that the information is accurate and complete.

UNITED STATES SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549
FORM 13F

FORM 13F INFORMATION TABLE
OMB APPROVAL
OMB Number: 3235-0006
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COLUMN 1 COLUMN 2 COLUMN 3 COLUMN 4 COLUMN 5 COLUMN 6 COLUMN 7 COLUMN 8
VALUE SHRS OR SH/ PUT/ INVESTMENT OTHER VOTING AUTHORITY
NAME OF ISSUER TITLE OF CLASS CUSIP (x$1000) PRN AMT PRN CALL DISCRETION MANAGER SOLE SHARED NONE
ABB Ltd. SPONSORED ADR 000375204 1 49 SH   SOLE   49 0 0
Acuity Brands, Inc. COM 00508Y102 2 15 SH   SOLE   15 0 0
Advanced Energy Industries, Inc. COM 007973100 1 22 SH   SOLE   22 0 0
Albemarle Corporation COM 012653101 4 48 SH   SOLE   48 0 0
Algonquin Power & Utilities COM 015857105 3 294 SH   SOLE   294 0 0
Altus Midstream Company CL A 02215L100 20,286 3,438,264 SH   SOLE   3,438,264 0 0
American Water Works Company, Inc. COM 030420103 13 123 SH   SOLE   123 0 0
Anadarko Petroleum Corp. COM 032511107 9,172 201,682 SH   SOLE   201,682 0 0
Andeavor Logistics, L.P. COM UNIT LP INT 03350F106 501,234 14,215,365 SH   SOLE   13,032,859 0 1,182,506
Antero Midstream Corporation COM 03676B102 479,488 34,795,923 SH   SOLE   32,338,273 0 2,457,650
Antero Resources Corp. COM 03674X106 8,379 948,957 SH   SOLE   948,957 0 0
Apache Corp. COM 037411105 3,357 96,842 SH   SOLE   96,842 0 0
Aptiv PLC SHS G6095L109 1 18 SH   SOLE   18 0 0
Aqua America, Inc. COM 03836W103 6 175 SH   SOLE   175 0 0
Aquaventure Holdings Ltd. SHS G0443N107 4 223 SH   SOLE   223 0 0
Atlantica Yield PLC SHS G0751N103 36 1,861 SH   SOLE   1,861 0 0
Autoliv, Inc. COM 052800109 1 8 SH   SOLE   8 0 0
Badger Meter, Inc. COM 056525108 3 53 SH   SOLE   53 0 0
Baker Hughes, a GE Company, L.L.C CL A 05722G100 2 69 SH   SOLE   69 0 0
BorgWarner, Inc. COM 099724106 2 45 SH   SOLE   45 0 0
BP Midstream Partners, L.P. UNIT LTD PTNR 0556EL109 89,206 6,164,881 SH   SOLE   5,567,905 0 596,976
Brookfield Renewable Energy Partners PARTNERSHIP UNIT G16258108 37 1,167 SH   SOLE   1,167 0 0
Buckeye Partners, L.P. UNIT LTD PARTN 118230101 375,451 11,036,173 SH   SOLE   10,215,136 0 821,037
Cabot Oil & Gas Corp. COM 127097103 19,715 755,375 SH   SOLE   755,375 0 0
Cactus, Inc. CL A 127203107 1 19 SH   SOLE   19 0 0
Carrizo Oil & Gas, Inc. COM 144577103 5,114 410,080 SH   SOLE   410,080 0 0
Celanese Corporation COM 150870103 2 16 SH   SOLE   16 0 0
Centennial Resource Development CL A 15136A102 2,553 290,433 SH   SOLE   290,433 0 0
Chart Industries, Inc. COM PAR $0.01 16115Q308 1 7 SH   SOLE   7 0 0
Cheniere Energy Inc. COM 16411R208 541,597 7,922,721 SH   SOLE   7,642,687 0 280,034
Cheniere Energy Partners, L.P. COM UNIT 16411Q101 4,575 109,102 SH   SOLE   59,926 0 49,176
Chevron Corp. COM 166764100 1,941 15,760 SH   SOLE   15,760 0 0
Cimarex Energy Co. COM 171798101 8,319 119,018 SH   SOLE   119,018 0 0
Clearway Energy, Inc. CL A 18539C204 22 1,436 SH   SOLE   1,436 0 0
Cms Energy Corp. COM 125896100 185 3,322 SH   SOLE   3,322 0 0
CNX Midstream Partners, L.P. COM UNIT REPST 12654A101 76,855 5,052,909 SH   SOLE   5,052,909 0 0
Concho Resources, Inc. COM 20605P101 13,619 122,738 SH   SOLE   122,738 0 0
ConocoPhillips COM 20825c104 2,485 37,231 SH   SOLE   37,231 0 0
Continental Resources, Inc. COM 212015101 10,918 243,863 SH   SOLE   243,863 0 0
Core Laboratories N.V. COM N22717107 1 10 SH   SOLE   10 0 0
Covanta Holding Corporation COM 22282E102 35 2,000 SH   SOLE   2,000 0 0
Crestwood Equity Partners, L.P. UNIT LTD PARTNER 226344208 4 103 SH   SOLE   103 0 0
Danaher Corporation COM 235851102 7 54 SH   SOLE   54 0 0
DCP Midstream, L.P. COM UT LTD PTN 23311P100 133,997 4,054,364 SH   SOLE   3,903,800 0 150,564
Delek Logistics Partners, L.P. COM UNT RP INT 24664T103 9,337 287,927 SH   SOLE   287,927 0 0
Delek US Holdings, Inc. COM 24665A103 9,993 274,379 SH   SOLE   274,379 0 0
Delphi Technologies PLC SHS G2709G107 1 54 SH   SOLE   54 0 0
Devon Energy Corporation COM 25179M103 7,821 247,818 SH   SOLE   247,818 0 0
Diamondback Energy, Inc. COM 25278X109 8,255 81,302 SH   SOLE   81,302 0 0
Dominion Energy, Inc. COM 25746U109 440 5,736 SH   SOLE   5,736 0 0
Dril-Quip, Inc. COM 262037104 1 20 SH   SOLE   20 0 0
DTE Energy Company COM 233331107 5 41 SH   SOLE   41 0 0
DTE Energy Preferred UNIT 99/99/9999 233331883 2,192 39,600 SH   SOLE   39,600 0 0
Duke Energy Corporation COM 26441C204 3 36 SH   SOLE   36 0 0
Eastman Chemical Co. COM 277432100 1 17 SH   SOLE   17 0 0
Ecolab, Inc. COM 278865100 6 33 SH   SOLE   33 0 0
Enbridge, Inc. COM 29250N105 223,532 6,164,713 SH   SOLE   6,164,713 0 0
Encana Corp. COM 292505104 7,406 1,022,904 SH   SOLE   1,022,904 0 0
Energy Recovery, Inc. COM 29270J100 1 72 SH   SOLE   72 0 0
Energy Transfer, L.P. COM UT LTD PTN 29273V100 1,417,810 92,245,286 SH   SOLE   84,712,959 0 7,532,327
Enlink Midstream, L.L.C COM UNIT REP LTD 29336T100 403,236 31,552,103 SH   SOLE   29,688,149 0 1,863,954
Ensco PLC SHS CL A G3157S106 0 35 SH   SOLE   35 0 0
Enterprise Products Partners, L.P. COM 293792107 1,198,593 41,188,748 SH   SOLE   37,260,853 0 3,927,895
Enviva Partners, L.P. COM UNIT 29414J107 5,658 175,439 SH   SOLE   175,439 0 0
EOG Resources, Inc. COM 26875P101 10,428 109,556 SH   SOLE   109,556 0 0
EQM Midstream Partners, L.P. UNIT LTD PARTN 26885B100 638,829 13,836,445 SH   SOLE   12,616,913 0 1,219,532
EQT Corp. COM 26884L109 36,485 1,759,160 SH   SOLE   1,759,160 0 0
Equitrans Midstream Corporation COM 294600101 144,385 6,629,234 SH   SOLE   6,629,234 0 0
Esco Technologies Inc. COM 296315104 2 35 SH   SOLE   35 0 0
Evoqua Water Technologies Corp. COM 30057T105 3 243 SH   SOLE   243 0 0
Exelon Corporation COM 30161N101 4 70 SH   SOLE   70 0 0
Extraction Oil & Gas, L.L.C COM 30227M105 1,203 284,405 SH   SOLE   284,405 0 0
Exxon Mobil Corp. COM 30231G102 3 35 SH   SOLE   35 0 0
FireEye, Inc. COM 31816Q101 1 53 SH   SOLE   53 0 0
Ford Motor Co. COM 345370860 2 207 SH   SOLE   207 0 0
Forum Energy Technologies, Inc. COM 34984V100 0 41 SH   SOLE   41 0 0
FTS International, Inc. COM 30283W104 0 49 SH   SOLE   49 0 0
GasLog Partners, L.P. UNIT LTD PTNRP Y2687W108 47,596 2,103,244 SH   SOLE   2,103,244 0 0
Genesis Energy, L.P. UNIT LTD PARTN 371927104 1,084 46,539 SH   SOLE   46,539 0 0
Golar LNG Ltd. SHS G9456A100 1 25 SH   SOLE   25 0 0
Gulfport Energy Corp. COM 402635304 0 53 SH   SOLE   53 0 0
Halcon Resources Corp COM PAR 40537Q605 1,310 970,000 SH   SOLE   970,000 0 0
Halliburton Company COM 406216101 1 34 SH   SOLE   34 0 0
Hannon Armstrong Sustainable Infrastructure COM 41068X100 47 1,835 SH   SOLE   1,835 0 0
Helmerich & Payne, Inc. COM 423452101 1 20 SH   SOLE   20 0 0
Hess Corp. COM 42809H107 1 19 SH   SOLE   19 0 0
Holly Energy Partners, L.P. COM UT LTD PTN 435763107 158,086 5,857,215 SH   SOLE   5,857,215 0 0
IDEX Corporation COM 45167R104 3 20 SH   SOLE   20 0 0
InfraREIT, Inc. COM 45685L100 21 1,000 SH   SOLE   1,000 0 0
iShares iBoxx High Yield Corp IBOXX HI YD ETF 464288513 13,920 160,978 SH   SOLE   160,978 0 0
Itron, Inc. COM 465741106 4 90 SH   SOLE   90 0 0
Keane Group, Inc. COM 48669A108 1 70 SH   SOLE   70 0 0
Kinder Morgan, Inc. COM 49456B101 498,063 24,890,725 SH   SOLE   24,154,179 0 736,546
Laredo Petroleum, Inc. COM 516806106 1,289 417,200 SH   SOLE   417,200 0 0
Lear Corporation COM 521865204 0 3 SH   SOLE   3 0 0
Liberty Oilfield Services, Inc. COM CL A 53115L104 0 16 SH   SOLE   16 0 0
Magellan Midstream Partners, L.P. COM UNIT RP LP 559080106 977,841 16,128,000 SH   SOLE   14,548,038 0 1,579,962
Magna International, Inc. COM 559222401 2 44 SH   SOLE   44 0 0
Magnolia Oil and Gas Corporation CL A 559663109 1 77 SH   SOLE   77 0 0
Marathon Oil Corp. COM 565849106 1,775 106,215 SH   SOLE   106,215 0 0
Marathon Petroleum Corp. COM 56585A102 2,163 36,138 SH   SOLE   36,138 0 0
Micron Technology, Inc. COM 595112103 2 52 SH   SOLE   52 0 0
Middlesex Water Co. COM 596680108 1 18 SH   SOLE   18 0 0
Monolithic Power Systems, Inc. COM 609839105 4 33 SH   SOLE   33 0 0
MPLX, L.P. COM UNIT REP LTD 55336V100 882,061 26,818,513 SH   SOLE   24,242,314 0 2,576,199
MRC Global, Inc. COM 55345K103 0 27 SH   SOLE   27 0 0
Mueller Water Products, Inc. COM SER A 624758108 1 69 SH   SOLE   69 0 0
National Fuel Gas Co. COM 636180101 1 23 SH   SOLE   23 0 0
NATIONAL OILWELL VARCO, INC. COM 637071101 1 22 SH   SOLE   22 0 0
New Fortress Energy, L.L.C CL A SHS RP LLC 644393100 2 192 SH   SOLE   192 0 0
Newpark Resources, Inc. COM PAR $.01 651718504 1 91 SH   SOLE   91 0 0
Nextera Energy, Inc. COM 65339F101 1,244 6,436 SH   SOLE   6,436 0 0
Nextera Energy Partners, L.P. COM UNIT PART IN 65341B106 168 3,593 SH   SOLE   3,593 0 0
Nio Inc. SPON ADS 62914V106 0 49 SH   SOLE   49 0 0
Nisource Inc. COM 65473P105 2 64 SH   SOLE   64 0 0
Noble Energy Inc. COM 655044105 14,119 570,943 SH   SOLE   570,943 0 0
Noble Midstream Partners, L.P. COM UNIT REPST 65506L105 83,031 2,305,764 SH   SOLE   2,054,165 0 251,599
NuStar Energy, L.P. UNIT COM 67058H102 108,519 4,035,672 SH   SOLE   4,035,672 0 0
nVent Electric PLC SHS G6700G107 1 23 SH   SOLE   23 0 0
NVIDIA Corporation COM 67066G104 3 17 SH   SOLE   17 0 0
Occidental Petroleum Corp. COM 674599105 2 32 SH   SOLE   32 0 0
Oceaneering International, Inc. COM 675232102 0 27 SH   SOLE   27 0 0
Olin Corporation COM PAR $1 680665205 1 42 SH   SOLE   42 0 0
ONEOK, Inc. COM 682680103 1,012,403 14,496,031 SH   SOLE   13,411,336 0 1,084,695
Ormat Technologies, Inc. COM 686688102 2 32 SH   SOLE   32 0 0
Parsley Energy, Inc. CL A 701877102 7,706 399,290 SH   SOLE   399,290 0 0
Pattern Energy Group, Inc. CL A 70338P100 26 1,192 SH   SOLE   1,192 0 0
Patterson-UTI Energy, Inc. COM 703481101 1 64 SH   SOLE   64 0 0
PBF Logistics, L.P. CL A 69318Q104 38,375 1,825,666 SH   SOLE   1,825,666 0 0
PDC Energy, Inc. COM 69327R101 3,775 92,800 SH   SOLE   92,800 0 0
Pembina Pipeline Corp. COM 706327103 210,816 5,738,886 SH   SOLE   5,738,886 0 0
PENTAIR, INC. SHS G7S00T104 6 129 SH   SOLE   129 0 0
Phillips 66 Partners, L.P. COM UNIT REP INT 718549207 546,707 10,443,311 SH   SOLE   9,527,770 0 915,541
Pioneer Natural Resources Co. COM 723787107 14,857 97,565 SH   SOLE   97,565 0 0
Plains All American Pipeline UNIT LTD PARTN 726503105 928,682 37,889,941 SH   SOLE   33,370,596 0 4,519,345
Plains GP Holdings, L.P. LTD PARTNR INT A 72651A207 245,586 9,854,985 SH   SOLE   9,854,985 0 0
PPL Corporation COM 69351T106 3 96 SH   SOLE   96 0 0
QEP Resources, Inc. COM 74733V100 1 68 SH   SOLE   68 0 0
Range Resources Corp. COM 75281A109 10,347 920,560 SH   SOLE   920,560 0 0
Schlumberger, Ltd. COM 806857108 3 66 SH   SOLE   66 0 0
Select Energy Services, Inc. CL A COM 81617J301 0 28 SH   SOLE   28 0 0
Semgroup Corp CL A 81663A105 76,928 5,219,019 SH   SOLE   5,219,019 0 0
Sempra Energy COM 816851109 271 2,155 SH   SOLE   2,155 0 0
Sempra Energy 6% PFD CONV A 816851406 5,285 50,000 SH   SOLE   50,000 0 0
Shell Midstream Partners, L.P. UNIT LTD INT 822634101 485,269 23,729,540 SH   SOLE   22,305,633 0 1,423,907
SM Energy Co. COM 78454L100 1,154 66,000 SH   SOLE   66,000 0 0
SPDR Bloomberg Barclays High Yield BLOOMBERG BRCLYS 78464A417 13,917 386,905 SH   SOLE   386,905 0 0
SPDR Bloomberg Barclays Short BLOOMBERG SRT TR 78468R408 13,892 509,804 SH   SOLE   509,804 0 0
Splunk, Inc. COM 848637104 1 8 SH   SOLE   8 0 0
Sunrun, Inc. COM 86771W105 4 294 SH   SOLE   294 0 0
Superior Energy Services, Inc. COM 868157108 0 74 SH   SOLE   74 0 0
Tallgrass Energy, L.P. CLASS A SHS 874696107 528,200 21,010,323 SH   SOLE   19,523,099 0 1,487,224
Targa Resources Corp. COM 87612G101 546,535 13,153,678 SH   SOLE   12,530,377 0 623,301
TechnipFMC PLC COM G87110105 1 37 SH   SOLE   37 0 0
Terraform Power, Inc. COM CL A 88104R209 45 3,299 SH   SOLE   3,299 0 0
Tesla, Inc. COM 88160R101 9 31 SH   SOLE   31 0 0
Tetra Tech, Inc. COM 88162G103 4 63 SH   SOLE   63 0 0
The Goodyear Tire & Rubber Co. COM 382550101 1 41 SH   SOLE   41 0 0
The York Water Co. COM 987184108 1 41 SH   SOLE   41 0 0
Tortoise North American Pipeline TORTOISE NRAM PI 56167N720 12,697 531,710 SH   SOLE   531,710 0 0
TransAlta Renewables, Inc. COM 893463109 20 1,974 SH   SOLE   1,974 0 0
Transcanada Corp. COM 89353D107 285,912 6,362,083 SH   SOLE   6,362,083 0 0
Transocean Ltd. REG SHS H8817H100 0 40 SH   SOLE   40 0 0
USA Compression Partners, L.P. COMUNIT LTDPAR 90290N109 1 33 SH   SOLE   33 0 0
Valero Energy Corp. COM 91913Y100 972 11,456 SH   SOLE   11,456 0 0
Veoneer, Inc. COM 92336X109 0 8 SH   SOLE   8 0 0
Verisk Analytics, Inc. COM 92345Y106 1 10 SH   SOLE   10 0 0
Viper Energy Partners, L.P. COM UNT RP INT 92763M105 8,882 267,864 SH   SOLE   267,864 0 0
Vistra Energy Corp. COM 92840M102 2 63 SH   SOLE   63 0 0
Watts Water Technologies, Inc. CL A 942749102 1 10 SH   SOLE   10 0 0
WEC Energy Group, Inc. COM 92939U106 283 3,584 SH   SOLE   3,584 0 0
Western Midstream Partners, L.P. COM UNIT LP INT 958669103 846,830 27,003,514 SH   SOLE   24,496,410 0 2,507,104
Westlake Chem Corp. COM 960413102 1 21 SH   SOLE   21 0 0
Westlake Chemical Partners, L.P. COM UNIT RP LP 960417103 15,140 700,934 SH   SOLE   700,934 0 0
Whiting Petroleum Corp. COM 966387409 2,934 112,230 SH   SOLE   112,230 0 0
Williams Companies, Inc. COM 969457100 1,081,939 37,671,954 SH   SOLE   34,984,614 0 2,687,340
WPX Energy, Inc. COM 98212B103 9,201 701,793 SH   SOLE   701,793 0 0
Xylem, Inc. COM 98419M100 13 166 SH   SOLE   166 0 0