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 3 48 SH   SOLE   48 0 0
Algonquin Power & Utilities COM 015857105 3,551 293,058 SH   SOLE   294 0 292,764
Altus Midstream Company CL A 02215L100 12,790 3,438,264 SH   SOLE   3,438,264 0 0
American Water Works Company COM 030420103 215 1,852 SH   SOLE   1,852 0 0
Anadarko Petroleum Corp COM 032511107 7 98 SH   SOLE   98 0 0
Andeavor Logistics, L.P. COM UNIT LP INT 03350F106 446,031 12,277,216 SH   SOLE   11,385,746 0 891,470
Antero Midstream Corporation COM 03676B102 481,441 42,010,526 SH   SOLE   38,898,593 0 3,111,933
Antero Resources Corp COM 03674X106 6,751 1,220,767 SH   SOLE   1,220,767 0 0
Apache Corp COM 037411105 3,437 118,642 SH   SOLE   118,642 0 0
Aptiv PLC SHS G6095L109 1 18 SH   SOLE   18 0 0
Aqua America, Inc. COM 03836W103 192 4,636 SH   SOLE   4,636 0 0
Aquaventure Holdings Ltd SHS G0443N107 84 4,185 SH   SOLE   4,185 0 0
Atlantica Yield PLC SHS G0751N103 44 1,919 SH   SOLE   1,861 0 58
Autoliv, Inc. COM 052800109 1 8 SH   SOLE   8 0 0
Badger Meter, Inc. COM 056525108 80 1,339 SH   SOLE   1,339 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 102,091 6,595,026 SH   SOLE   5,992,454 0 602,572
Brookfield Renewable Energy Partners PARTNERSHIP UNIT G16258108 40 1,167 SH   SOLE   1,167 0 0
Buckeye Partners, L.P. UNIT LTD PARTN 118230101 589 14,345 SH   SOLE   14,345 0 0
Cabot Oil & Gas Corp. COM 127097103 17,841 777,048 SH   SOLE   777,048 0 0
Cactus, Inc. CL A 127203107 1 19 SH   SOLE   19 0 0
Carrizo Oil & Gas, Inc. COM 144577103 4,902 489,180 SH   SOLE   489,180 0 0
Celanese Corporation COM 150870103 2 16 SH   SOLE   16 0 0
Centennial Resource Development CL A 15136A102 2,072 273,033 SH   SOLE   273,033 0 0
Chart Industries, Inc. COM PAR $0.01 16115Q308 479 6,227 SH   SOLE   6,227 0 0
Cheniere Energy, Inc. COM 16411R208 551,027 8,050,063 SH   SOLE   7,706,132 0 343,931
Cheniere Energy Partners, L.P. COM UNIT 16411Q101 19,280 457,080 SH   SOLE   382,492 0 74,588
Chevron Corp COM 166764100 2,067 16,607 SH   SOLE   16,607 0 0
Cimarex Energy Co. COM 171798101 8,373 141,118 SH   SOLE   141,118 0 0
Clearway Energy, Inc. CL C 18539C204 24 1,436 SH   SOLE   1,436 0 0
Cms Energy Corp COM 125896100 192 3,322 SH   SOLE   3,322 0 0
CNX Midstream Partners, L.P. COM UNIT REPST 12654A101 74,515 5,303,582 SH   SOLE   5,303,582 0 0
Concho Resources, Inc. COM 20605P101 9,182 88,990 SH   SOLE   88,990 0 0
ConocoPhillips COM 20825c104 2,540 41,647 SH   SOLE   41,647 0 0
Continental Resources, Inc. COM 212015101 9,087 215,902 SH   SOLE   215,902 0 0
Core Laboratories N.V. COM N22717107 1 10 SH   SOLE   10 0 0
Covanta Holding Corporation COM 22282E102 5,697 318,092 SH   SOLE   2,000 0 316,092
Crestwood Equity Partners, L.P. UNIT LTD PARTNER 226344208 4 103 SH   SOLE   103 0 0
Danaher Corporation COM 235851102 179 1,255 SH   SOLE   1,255 0 0
DCP Midstream, L.P. COM UT LTD PTN 23311P100 157,839 5,386,989 SH   SOLE   5,232,657 0 154,332
Delek Logistics Partners, L.P. COM UNT RP INT 24664T103 10,359 323,720 SH   SOLE   323,720 0 0
Delek US Holdings, Inc. COM 24665A103 9,839 242,815 SH   SOLE   242,815 0 0
Delphi Technologies PLC SHS G2709G107 1 54 SH   SOLE   54 0 0
Devon Energy Corporation COM 25179M103 6,175 216,518 SH   SOLE   216,518 0 0
Diamondback Energy, Inc. COM 25278X109 9,474 86,937 SH   SOLE   86,937 0 0
Dominion Energy, Inc. COM 25746U109 297 3,842 SH   SOLE   3,842 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 2,226 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 74 377 SH   SOLE   377 0 0
Enable Midstream Partners, L.P. COM UNIT RP IN 292480100 3,584 261,428 SH   SOLE   261,428 0 0
Enbridge, Inc. COM 29250N105 210,932 5,846,234 SH   SOLE   5,846,234 0 0
Encana Corp. COM 292505104 5,905 1,151,104 SH   SOLE   1,151,104 0 0
Energy Recovery, Inc. COM 29270J100 22 2,068 SH   SOLE   2,068 0 0
Energy Transfer, L.P. COM UT LTD PTN 29273V100 1,299,050 92,262,055 SH   SOLE   84,538,869 0 7,723,186
Enlink Midstream, L.L.C. COM UNIT REP LTD 29336T100 331,130 32,817,606 SH   SOLE   30,918,533 0 1,899,073
Enterprise Products Partners L.P. COM 293792107 1,201,581 41,620,404 SH   SOLE   37,722,383 0 3,898,021
Enviva Partners, L.P. COM UNIT 29414J107 5,512 175,439 SH   SOLE   175,439 0 0
EOG Resources, Inc. COM 26875P101 9,077 97,433 SH   SOLE   97,433 0 0
EQM Midstream Partners, L.P. UNIT LTD PARTN 26885B100 659,478 14,760,030 SH   SOLE   13,414,769 0 1,345,261
EQT Corp. COM 26884L109 13,508 854,390 SH   SOLE   854,390 0 0
Equitrans Midstream Corporation COM 294600101 126,540 6,420,069 SH   SOLE   6,420,069 0 0
Esco Technologies, Inc. COM 296315104 3 35 SH   SOLE   35 0 0
Evoqua Water Technologies Corp. COM 30057T105 68 4,752 SH   SOLE   4,752 0 0
Exelon Corporation COM 30161N101 3 70 SH   SOLE   70 0 0
Extraction Oil & Gas, L.L.C COM 30227M105 1,231 284,405 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 LP UNIT LTD PTNRP Y2687W108 54,207 2,553,340 SH   SOLE   2,553,340 0 0
Genesis Energy L.P. UNIT LTD PARTN 371927104 17,510 799,532 SH   SOLE   799,532 0 0
Golar LNG Ltd SHS G9456A100 0 25 SH   SOLE   25 0 0
Gulfport Energy Corp COM 402635304 0 53 SH   SOLE   53 0 0
Halcon Resources Corp - Restri COM 40537Q605 171 970,000 SH   SOLE   970,000 0 0
Halliburton Company COM 406216101 1 34 SH   SOLE   34 0 0
Hannon Armstrong Sustainable I COM 41068X100 52 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
Hess Midstream Partners LP UNIT LTD PR INT 428104103 18,268 936,805 SH   SOLE   936,805 0 0
Holly Energy Partners, L.P. COM UT LTD PTN 435763107 147,967 5,380,631 SH   SOLE   5,380,631 0 0
IDEX Corporation COM 45167R104 90 524 SH   SOLE   524 0 0
iShares iBoxx High Yield Corp IBOXX HI YD ETF 464288513 4,428 50,795 SH   SOLE   50,795 0 0
Itron, Inc. COM 465741106 6 90 SH   SOLE   90 0 0
Keane Group Inc. COM 48669A108 0 70 SH   SOLE   70 0 0
Kinder Morgan, Inc. COM 49456B101 509,435 24,398,206 SH   SOLE   23,670,688 0 727,518
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 993,928 15,530,118 SH   SOLE   13,974,110 0 1,556,008
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 2,160 152,015 SH   SOLE   152,015 0 0
Marathon Petroleum Corp. COM 56585A102 2,252 40,306 SH   SOLE   40,306 0 0
Micron Technology, Inc. COM 595112103 2 52 SH   SOLE   52 0 0
Middlesex Water Co. COM 596680108 42 702 SH   SOLE   702 0 0
Monolithic Power Systems, Inc. COM 609839105 4 33 SH   SOLE   33 0 0
MPLX, L.P. COM UNIT REP LTD 55336V100 809,463 25,146,401 SH   SOLE   22,570,326 0 2,576,075
MRC Global, Inc. COM 55345K103 0 27 SH   SOLE   27 0 0
Mueller Water Products, Inc. COM SER A 624758108 22 2,206 SH   SOLE   2,206 0 0
National Fuel Gas Co. COM 636180101 1 23 SH   SOLE   23 0 0
NATIONAL OILWELL VARCO, INC. COM 637071101 0 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 2,158 10,533 SH   SOLE   10,533 0 0
Nextera Energy Partners, L.P. COM UNIT PART IN 65341B106 177 3,662 SH   SOLE   3,593 0 69
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 10,838 483,843 SH   SOLE   483,843 0 0
Noble Midstream Partners L.P. COM UNIT REPST 65506L105 86,576 2,352,968 SH   SOLE   2,352,968 0 250,040
NuStar Energy L.P. UNIT COM 67058H102 157,521 5,804,003 SH   SOLE   5,598,989 0 205,014
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 1,535 30,532 SH   SOLE   30,532 0 0
Oceaneering International Inc. COM 675232102 1 27 SH   SOLE   27 0 0
Olin Corporation COM PAR $1 680665205 1 42 SH   SOLE   42 0 0
ONEOK, Inc. COM 682680103 996,394 14,480,369 SH   SOLE   13,364,968 0 1,115,401
Ormat Technologies, Inc. COM 686688102 2 32 SH   SOLE   32 0 0
Parsley Energy, Inc. CL A 701877102 7,077 372,290 SH   SOLE   372,290 0 0
Pattern Energy Group, Inc. CL A 70338P100 4,187 181,314 SH   SOLE   1,192 0 180,122
Patterson-UTI Energy, Inc. COM 703481101 1 64 SH   SOLE   64 0 0
PBF Logistics, L.P. UNIT LTD PTNR 69318Q104 56,574 2,676,166 SH   SOLE   2,676,166 0 0
PDC Energy, Inc. COM 69327R101 4,006 111,100 SH   SOLE   111,100 0 0
Pembina Pipeline Corporation COM 706327103 1,094 29,395 SH   SOLE   29,395 0 0
PENTAIR, INC. SHS G7S00T104 1,007 27,070 SH   SOLE   3,695 0 23,375
Phillips 66 Partners, L.P. COM UNIT REP INT 718549207 491,495 9,959,370 SH   SOLE   9,042,148 0 917,222
Pioneer Natural Resources Co. COM 723787107 12,318 80,059 SH   SOLE   80,059 0 0
Plains All American Pipeline, L.P. UNIT LTD PARTN 726503105 971,674 39,904,482 SH   SOLE   35,169,833 0 4,734,649
Plains GP Holdings, L.P. LTD PARTNR INT A 72651A207 239,996 9,611,377 SH   SOLE   9,611,377 0 0
PPL Corporation COM 69351T106 3 96 SH   SOLE   96 0 0
QEP Resources Inc. COM 74733V100 0 68 SH   SOLE   68 0 0
Range Resources Corp COM 75281A109 7,586 1,086,760 SH   SOLE   1,086,760 0 0
Rattler Midstream Partners, L.P. COM UNITS 75419T103 91,193 4,703,103 SH   SOLE   4,411,257 0 291,846
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 62,118 5,176,525 SH   SOLE   5,176,525 0 0
Sempra Energy COM 816851109 297 2,159 SH   SOLE   2,159 0 0
Sempra Energy 6% PFD CONV A 816851406 5,575 50,000 SH   SOLE   50,000 0 0
Shell Midstream Partners LP UNIT LTD INT 822634101 475,843 22,965,393 SH   SOLE   21,572,682 0 1,392,711
SM Energy Co COM 78454L100 759 60,600 SH   SOLE   60,600 0 0
SPDR Bloomberg Barclays High Yield BLOOMBERG BRCLYS 78468R622 14,050 128,968 SH   SOLE   128,968 0 0
SPDR Bloomberg Barclays Short BLOOMBERG SRT TR 78468R408 13,882 509,804 SH   SOLE   509,804 0 0
Superior Energy Services, Inc. COM 868157108 0 74 SH   SOLE   74 0 0
Tallgrass Energy LP CLASS A SHS 874696107 407,257 19,292,154 SH   SOLE   17,867,033 0 1,425,121
Targa Resources Corp. COM 87612G101 556,236 14,168,008 SH   SOLE   13,542,732 0 625,276
TC Energy Corp. COM 87807B107 284,341 5,741,942 SH   SOLE   5,741,942 0 0
TechnipFMC PLC COM G87110105 1 37 SH   SOLE   37 0 0
Terraform Power Inc COM CL A 88104R209 2,992 209,208 SH   SOLE   3,299 0 205,909
Tesla Inc. COM 88160R101 8 36 SH   SOLE   36 0 0
Tetra Tech, Inc. COM 88162G103 130 1,653 SH   SOLE   1,653 0 0
The Goodyear Tire & Rubber Company COM 382550101 1 41 SH   SOLE   41 0 0
The York Water Co. COM 987184108 43 1,209 SH   SOLE   1,209 0 0
Tortoise North American Pipeli TORTOISE NRAM PI 56167N720 12,713 531,709 SH   SOLE   531,709 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 2,228 26,022 SH   SOLE   26,022 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 8,256 267,864 SH   SOLE   267,864 0 0
Vistra Energy Corp. COM 92840M102 1 63 SH   SOLE   63 0 0
Watts Water Technologies, Inc. CL A 942749102 21 226 SH   SOLE   226 0 0
WEC Energy Group, Inc. COM 92939U106 299 3,584 SH   SOLE   3,584 0 0
Western Midstream Partners, L.P. COM UNIT LP INT 958669103 848,094 27,562,374 SH   SOLE   24,942,090 0 2,620,284
Westlake Chem Corp COM 960413102 1 21 SH   SOLE   21 0 0
Westlake Chemical Partners, L.P. COM UNIT RP LP 960417103 17,236 700,934 SH   SOLE   700,934 0 0
Whiting Petroleum Corp. COM 966387409 2,939 157,330 SH   SOLE   157,330 0 0
Williams Companies, Inc. COM 969457100 1,012,513 36,109,596 SH   SOLE   33,446,102 0 2,663,494
WPX Energy, Inc. COM 98212B103 7,746 672,993 SH   SOLE   672,993 0 0
Xylem, Inc. COM 98419M100 218 2,605 SH   SOLE   2,605 0 0