       NOTE: This disposition is nonprecedential.


  United States Court of Appeals
      for the Federal Circuit
                 ______________________

         RULING MENG, PEI-HERNG HOR,
               Plaintiffs-Appellants

                            v.

               CHING-WU "PAUL" CHU,
                  Defendant-Appellee
                ______________________

                  2014-1746, 2015-1390
                 ______________________

    Appeals from the United States District Court for the
Southern District of Texas in No. 4:08-cv-03584, Judge
Keith P. Ellison.
                  ______________________

                 Decided: April 5, 2016
                 ______________________

    BRENT C. PERRY, Law Office of Brent C. Perry, Hou-
ston, TX, argued for plaintiff-appellant Ruling Meng. Also
represented by GORDON GRAY WAGGETT, Gordon G. Wag-
gett, P.C., Houston, TX.

   JOE W. BEVERLY, Dow Golub Remels & Beverly, LLP,
Houston, TX, argued for plaintiff-appellant Pei-Herng
Hor. Also represented by WILLIAM POWELL JENSEN, Crain
Caton & James, Houston, TX.
2                                           MENG   v. CHU



    LESTER L. HEWITT, Law Office of Lester L. Hewitt,
Houston, TX, argued for defendant-appellee. Also repre-
sented by DAVID R. CLONTS, REHAN M. SAFIULLAH, ASHLEY
M. BROWN, Akin, Gump, Strauss, Hauer & Feld, LLP,
Houston, TX; EMILY CURTIS JOHNSON, Washington, DC.
                ______________________

    Before PROST, Chief Judge, DYK and WALLACH, Circuit
                          Judges.
PROST, Chief Judge.
    Appellants Pei-Herng Hor (“Hor”) and Ruling Meng
(“Meng”) filed this suit against Appellee Ching-Wu Chu
(“Chu”) under 35 U.S.C. § 256 for correction of inventor-
ship of U.S. Patent Nos. 7,709,418 (“’418 patent”) and
7,056,866 (“’866 patent”). Following an eight-day bench
trial, the United States District Court for the Southern
District of Texas denied both parties’ claims. For reasons
discussed below, we affirm.
                       BACKGROUND
                            A
   The circumstances giving rise to this appeal are
summarized in the district court’s decisions, Hor v. Chu,
No. 4:08-CV-3584, 2015 WL 269123 (S.D. Tex. Jan. 21,
2015) and Hor v. Chu, 765 F. Supp. 2d 903, 906 (S.D. Tex.
2011), aff’d in part, rev’d in part and remanded, Hor v.
Chu, 699 F.3d 1331 (Fed. Cir. 2012). We provide infor-
mation relevant to the issues here below.
     The patents at issue generally relate to superconduct-
ing compounds that have transition temperatures higher
than the boiling point of liquid nitrogen. The ’418 patent,
filed on January 23, 1989 and issued on June 6, 2006,
covers compounds consisting of Yttrium, Barium, Copper,
and Oxygen, assembled according to a 2-1-4 ratio of
Yttrium to Barium to Copper. The ’866 patent, filed on
March 26, 1987 and issued on May 4, 2010, covers com-
MENG   v. CHU                                            3



pounds consisting of Yttrium and/or certain rare earth
elements (such as Gadolinium, Europium, and Samari-
um), Barium, Copper, and Oxygen, assembled according
to a 1-2-3 ratio. Chu is the sole named inventor on both
patents.
    Chu worked with Hor and Meng in the High Pressure
Low Temperature (“HPLT”) lab at the University of
Houston. Chu was a physics professor and the lab’s
principal investigator. Hor was Chu’s graduate student
and, later, post-doctoral fellow. Meng served as an inde-
pendent materials scientist.
     In November 1986, Meng’s Chinese mentor pointed
her to an article entitled “Possible High Tc Superconduc-
tivity in the Ba-La-Cu-O System” by Bednorz and Müller,
which she subsequently shared with Chu. Meng and Chu
decided to reproduce the compound described in the
article (“LBCO compound”) using the solid state reaction
method. Meng and Chu disagree as to whose idea it was
to use the solid state reaction method, an approach that
differed from Bednorz and Müller’s, who used a co-
precipitation method. Meng prepared the LBCO com-
pound in late November, and the group observed it had
superconducting qualities.
   At some point between December 1986 and January
1987, the group contemplated substituting Yttrium for
Lanthanum in the LBCO compound. 1 This substitution



   1    Both Hor and Chu claim that they were the first
to come up with the idea of substituting Yttrium for
Lanthanum. Compare Appellee Br. 13–14, with Cross-
Appellant Br. 8–10. This matter was disputed below as
the basis for Hor’s claims to inventorship of the ’418
patent, which the district court found Hor failed to prove
by clear and convincing evidence. J.A. 52. Hor does not
challenge the district court’s decision with respect to the
4                                             MENG   v. CHU



was first performed in late January using a 2-1-4 ratio of
Yttrium to Barium to Copper. The resulting compound,
YBCO-214, eventually became the subject of the ’418
patent.
    YBCO-214 contained a black phase, which was super-
conducting, and a green phase, which was not. Interested
in isolating the black superconducting phase, Chu di-
rected Meng to prepare samples of the black phase, so
that its chemical formula and structure could be deter-
mined.
    On or around February 22, 1987, the HPLT lab began
work on pair-breaking experiments which partially sub-
stituted Gadolinium, the most magnetic rare earth ele-
ment, for Yttrium in YBCO-214.                Chu claims
responsibility for these partial substitution experiments,
Appellee Br. 18–19, and Hor has conceded that “it is
possible that a compound with a small fraction substitu-
tion of Gadolinium for Yttrium was actually created—and
even possibly created at the direction of Chu . . . .” Cross-
Appellant Reply Br. 20. However, the parties dispute the
extent to which synthesis work was completed and veri-
fied.
    Days later, on February 27 or 28, the HPLT group re-
ceived preliminary results identifying black phase as
YBCO-123, a compound having a 1-2-3 ratio of Yttrium to
Barium to Copper. These results were finalized by March
8.
   Pair-breaking experiments ramped up in early March,
but with a new focus: instead of partially substituting
magnetic rare earth elements for Yttrium in YBCO-214,
the group completely substituted magnetic rare earth


’418 patent in this appeal, Cross-Appellant Br. 28, so we
need not reach the issue of whether Yttrium substitution
originated with Chu or Hor.
MENG   v. CHU                                            5



elements for Yttrium in YBCO-123. These complete
substitutions appear to have been contemplated as early
as March 7, as a lab notebook entry shows chemical
formulas for completely substituting rare earth elements
in YBCO-123 on this date. At trial, Chu testified that this
list of substitutions was “his.” J.A. 4150. Hor does not
claim responsibility for this entry. See Cross-Appellant
Br. 19 n.3; Oral Argument at 15:35–45, available at
http://oralarguments.cafc.uscourts.gov/default.aspx?fl=20
14-1746.mp3. Over the next two weeks, the group syn-
thesized and confirmed the superconductivity of at least
ten different compounds, all created by completely substi-
tuting Yttrium with a magnetic rare earth element,
including Europium (Eu), Samarium (Sm), Gadolinium
(Gd), Cerium (Ce), Terbium (Tb), Neodymium (Nd), Erbi-
um (Er), Dysprosium (Dy), Holmium (Ho), and Ytterbium
(Yb).
     Hor and Chu disagree as to how this new series of ex-
periments came about. According to Chu, he originally
had the idea to perform complete rare earth substitution
back in February, when he performed partial rare earth
substitution and observed that this did not suppress
superconductivity. He then claims that, as a natural
consequence of this activity, he instructed Meng in March
to try complete substitution of Europium and Samarium,
followed by Gadolinium and other rare earth elements.
Hor does not claim responsibility for the Europium and
Samarium substitutions, but instead dismisses them as
“substitutions [likely] done by Meng as a part of a vast
number of different elements being tried by the HPLT
lab.” Cross-Appellant Br. 19 n.3. Instead, he claims that
the true surge in complete rare earth substitution exper-
iments began with the successful substitution of Gadolin-
ium on March 15. Hor claims that he—not Chu—
triggered this activity on March 11 or 12, when he in-
structed Meng to synthesize a compound that completely
substituted Gadolinium for Yttrium in YBCO-123.
6                                          MENG   v. CHU



    Regardless of how they arose, the outcome of the com-
plete rare earth substitution experiments was significant;
they revealed an entire line of previously-unknown rare
earth superconductors, all of which had a transition
temperature higher than liquid nitrogen.
    Publication, patent, and commercialization efforts for
the rare earth superconductors soon followed. On March
16, Chu submitted a paper to the Physical Review Letters
describing complete substitution of the rare earth ele-
ments in YBCO-123, which was published on May 4. J.A.
5304–07. Hor and Meng are listed as first and second
authors to the paper, and Chu is listed last. J.A. 5304.
The article does not mention partial substitution of rare
earth elements in YBCO-214. Id.
    On March 26, Chu submitted a continuation-in-part
application which claimed partial and complete substitu-
tions of the rare earth elements. This application eventu-
ally issued as the ’866 patent.
    In 1988, DuPont licensed the technology relating to
the ’418 and ’866 patents. Chu shared the proceeds
evenly with the University of Houston, and then, out of
his remaining portion, gave $137,000 to Hor and $137,000
to Meng.
    Chu, Hor, and Meng continued to work together at the
University of Houston. In 1992, Chu wrote a letter of
recommendation for Hor in support of his promotion and
tenure at the university. The recommendation stated
that “Pei’s contributions to our research on high tempera-
ture superconducting (HTS) and related materials have
been significant and numerous.” J.A. 5301–02. It also
asserted that “[h]e and colleagues under his direction
discovered the whole series of the so-called 123 com-
pounds REBa2Cu3O7,” the compounds created by complete
rare earth substitution experiments. J.A. 5302.
MENG   v. CHU                                            7



    Chu continued to publish articles on the rare earth
superconductors through the 1990s. Several of these
articles make statements about the timing of the concep-
tion events discussed above. Relevant here, four articles
state that substitution of rare earth elements was under-
taken after the chemical formula and structure of YBCO-
123 was known. J.A. 5113, 5334, 5342, 5355.
                            B
    Hor filed this action against Chu in December 2008,
seeking correction of inventorship for the ’418 and ’866
patents under 35 U.S.C. § 256. Meng intervened in
February 2010, also seeking correction of inventorship for
the ’418 and ’866 patents.
    In January 2014, the district court held an eight-day
bench trial on the merits. On January 21, 2015, the
district court issued an order denying both Meng’s and
Hor’s claims. With respect to Meng, the district court
found that Meng had not met her burden under § 256
because her testimony on who decided to use the solid
state reaction method was “hopelessly at odds” with
Chu’s, she had not presented enough factual evidence that
she conceived of using this method, and she had not
shown that her contribution exceeded the ordinary skill in
the art. With respect to Hor, the district court found that
he had not met his burden under § 256 with respect to the
’418 patent because he did not have sufficient corroborat-
ing evidence, and that he had not met his burden with
respect to the ’866 patent because “the evidence as to
what was tested when, and by whom, is so conflicting that
the Court cannot deem it clear and convincing.” J.A. 52.
   Meng and Hor now appeal the district court’s decision.
We have jurisdiction under 28 U.S.C. § 1295(a).
                       DISCUSSION
    Section 256 provides for correction of inventorship on
an issued patent. 35 U.S.C. § 256; MCV, Inc. v. King–
8                                            MENG   v. CHU



Seeley Thermos Co., 870 F.2d 1568, 1570 (Fed. Cir. 1989).
Because issued patents are presumed to correctly name
their inventors, the burden of proving nonjoinder of
inventors is a “heavy one,” which must be demonstrated
by clear and convincing evidence. See Hess v. Advanced
Cardiovascular Sys., 106 F.3d 976, 980 (Fed. Cir. 1997).
In order to prevail on a § 256 claim, an alleged co-inventor
must show that he contributed to the conception of the
claimed invention and that his contribution was “not
insignificant in quality, when that contribution is meas-
ured against the dimension of the full invention.” Acro-
med Corp. v. Sofamor Danek Grp., 253 F.3d 1371, 1379
(Fed. Cir. 2001). An alleged co-inventor’s testimony
regarding his contribution must be corroborated, which
courts assess under a “rule of reason” analysis. Ethicon,
Inc. v. U.S. Surgical Corp., 135 F.3d 1456, 1461 (Fed. Cir.
1998).
    “Conception, and consequently inventorship, are ques-
tions of law” which we review de novo. Sewall v. Walters,
21 F.3d 411, 415 (Fed. Cir. 1994). We review underlying
factual determinations for clear error. Id. “Credibility
determinations are entitled to strong deference.” Hess,
106 F.3d at 980.
    On appeal, Hor challenges the district court’s denial of
his claims to joint inventorship with respect to the ’866
patent. Meng challenges the district court’s denial of her
claims to joint inventorship with respect to the ’418 and
’866 patents. We address each challenge in turn.
                             A
    Hor contends that he made a significant contribution
to the conception of the rare earth superconductors
claimed in the ’866 patent because he initiated the com-
plete replacement of Yttrium with Gadolinium on or
around March 11. In support of this argument, Hor
offers: (1) his own testimony that he conceived of complete
replacement of Gadolinium; (2) testimony from Meng and
MENG   v. CHU                                            9



other individuals associated with the HPLT lab, including
Dr. Jeffrey Bechtold and Dr. Kenneth Forster; (3) docu-
mentary evidence, including Chu’s 1992 letter of recom-
mendation and excerpts from Chu’s publications which
state that Gadolinium replacement was undertaken after
the chemical formula and structure of YBCO-123 were
determined; and (4) circumstantial evidence, including
the timing of the “surge” of synthesis activity in March
1987, the timing of the continuation-in-part application
and Chu’s Physical Review Letters paper (Chu’s first
publication on rare earth substitutions, which was sub-
mitted after the Gadolinium substitutions that Hor claims
credit for), the fact that Hor had been named a first
author on a publication, and the fact that Chu shared the
proceeds of the DuPont license with Hor. Hor argues that
this evidence corroborates his claim to have invented the
rare earth superconductors in March, and thus satisfies
his burden under § 256.
     Chu responds that the evidence cited by Hor is insuf-
ficient to meet his burden. In particular, Chu claims that
Hor’s arguments ignore evidence that Chu had fully
conceived of the ’866 patent before Hor’s Gadolinium
experiments, first through the February partial-
substitution experiments and then through the March
Europium and Samarium substitutions. Chu also attacks
Hor’s corroborating witnesses as interested and/or lacking
personal knowledge, and rebuts Hor’s other evidence as
equivocal.
    We agree with Chu and the district court that, in light
of the record evidence, Hor did not prove his claim for
joint inventorship by clear and convincing evidence. As
Hor and Chu agreed at oral argument, a lab notebook
entry dated March 7, 1987 contained chemical formulas
for the complete substitution of rare earth elements in
YBCO-123. See Oral Argument at 15:35–45, 33:35–34:50;
J.A. 5058–60. Hor does not claim responsibility for these
formulas. See Cross-Appellant Br. 19 n.3; Oral Argument
10                                           MENG   v. CHU



at 15:35–45. Instead, the earliest date he cites for his
version of the rare earth conception story is March 11,
when he claims he instructed Meng to synthesize a com-
pound by completely substituting Gadolinium for Yttrium
in YBCO-123. Cross-Appellant Br. 14. Accordingly, even
if we accept Hor’s version of events, this would not be
sufficient to establish that he was the first to conceive of
complete rare earth substitution.
    Moreover, even if Hor cannot establish that he was
the first to conceive of complete rare earth substitution,
he has not otherwise provided clear and convincing evi-
dence that he contributed to conception. “An alleged co-
inventor’s testimony, standing alone, cannot rise to the
level of clear and convincing evidence; he must supply
evidence to corroborate his testimony.” Symantec Corp. v.
Computer Assocs. Int’l, Inc., 522 F.3d 1279, 1295 (Fed.
Cir. 2008). The district court evaluated the entirety of
Hor’s corroborating evidence and found it insufficient.
J.A. 52. In particular, the district court found that Meng’s
testimony was only “mildly persuasive,” that the lab
records “do not conclusively point one way or the other,”
and that circumstantial evidence such as Hor being
named first author, the 1992 letter of recommendation,
and DuPont payments were “just not especially convinc-
ing.” Id.
    We see no reason to disturb the district court’s as-
sessment. Neither Dr. Forster nor Dr. Bechtold testified
that Hor ordered (or even discussed) experiments to
completely substitute Gadolinium for Yttrium in YBCO-
123, and, even though Meng testified to this fact, she is an
interested witness and the district court found her testi-
mony only “mildly persuasive.” J.A. 52. Chu’s 1992 letter
of recommendation was written five years after the rele-
vant time period and is a document designed to impart a
favorable impression of Hor, not a neutral recitation of
past events. Hor’s listing as first author and receipt of a
portion of the DuPont proceeds at most show that he had
MENG   v. CHU                                           11



a substantial involvement in the rare earth superconduc-
tor work at HPLT, but can neither prove nor disprove that
he contributed to the specific idea of complete rare earth
substitutions. Finally, none of the remaining evidence
cited by Hor provides any indication of the scope of his
personal involvement. For example, the alleged “surge” in
synthesis activity (drawn from lab records which the
district court found “do not conclusively point one way or
the other,” J.A. 52) could just as easily support Chu’s
contention that he initiated complete rare earth substitu-
tion experiments in March, as it could Hor’s. Accordingly,
considering the record evidence as a whole, we are not
persuaded that the district court erred in finding that Hor
failed to provide sufficient corroboration.
    Because we agree with the district court that Hor did
not meet his burden to show that he contributed to the
conception of the rare earth superconductors in March
1987, we need not reach Chu’s arguments that he con-
ceived of the rare earth superconductors in February
1987. We affirm the district court’s determination that
Hor did not prove his claim to correction of inventorship
under § 256 by clear and convincing evidence.
                            B
    Meng contends that she should be named a joint in-
ventor of the ’418 and ’866 patents because she developed
and implemented the solid state reaction methods by
which the claimed superconducting compounds were
synthesized. Meng asserts that her efforts, “through
extensive experimentation and analysis, required more
than the exercise of ordinary skill.” Appellant Br. 34.
She emphasizes that Chu only provided her with general
directions, and that she worked independently to come up
with the specific steps for creating the superconducting
compounds.
   Conception of a chemical compound “requires
knowledge of both the specific chemical structure of the
12                                            MENG   v. CHU



compound and an operative method of making it.” Fina
Oil & Chem. Co. v. Ewen, 123 F.3d 1466, 1473 (Fed. Cir.
1997). However, where the operative method requires
“nothing more than the use of ordinary skill in the art,”
this “would not normally be a sufficient contribution to
amount to an act of joint inventorship.” Falana v. Kent
State Univ., 669 F.3d 1349, 1357 (Fed. Cir. 2012).
    The district court considered Meng’s use of the solid
state reaction method and concluded that “the evidence is
not clear and convincing enough for the Court to find that
suggesting [use of the solid state reaction method] was
anything beyond that of ordinary skill in the profession.”
J.A. 51. Although Meng asserts the contrary, she does not
specifically explain what differentiates her efforts from
what would have been the ordinary efforts of a skilled
artisan. Meng seems to suggest that she exercised more
than ordinary skill because she “worked independently”
and engaged in “excessive experimentation,” but these are
only characterizations of the organizational structure of
the lab and the quantity of work that Meng performed,
not the level of skill she exercised. Accordingly, we agree
with the district court that Meng’s work does not exceed
the level of ordinary skill in the art.
    Given that Meng’s only asserted contribution to the
’418 and ’866 patents does not, under the facts and cir-
cumstances of this case, rise to the level of an act of joint
inventorship, her claims under § 256 fail. Because of this
fatal flaw, we do not need to reach the remainder of
Meng’s arguments, nor the district court’s decision with
respect to corroboration. We affirm the district court’s
determination that Meng did not prove her claim to
correction of inventorship under § 256 by clear and con-
vincing evidence.
MENG   v. CHU                                        13



                     CONCLUSION
    For the foregoing reasons, we affirm the district
court’s determination that neither Hor nor Meng is enti-
tled to correction of inventorship under § 256.
                     AFFIRMED
