19 research outputs found
The Chicago Center for Green Technology: life-cycle assessment of a brownfield redevelopment project
The sustainable development of brownfields reflects a fundamental, yet logical, shift in
thinking and policymaking regarding pollution prevention. Life-cycle assessment (LCA) is a
tool that can be used to assist in determining the conformity of brownfield development
projects to the sustainability paradigm. LCA was applied to the process of a real brownfield
redevelopment project, now known as the Chicago Center for Green Technology, to determine
the cumulative energy required to complete the following redevelopment stages:
(1) brownfield assessment and remediation, (2) building rehabilitation and site development
and (3) ten years of operation. The results of the LCA have shown that operational energy is
the dominant life-cycle stage after ten years of operation. The preservation and rehabilitation
of the existing building, the installation of renewable energy systems (geothermal and
photovoltaic) on-site and the use of more sustainable building products resulted in 72
terajoules (TJ) of avoided energy impacts, which would provide 14 years of operational
energy for the site
Proton-Only Sensing of Hyperpolarized [1,2-<sup>13</sup>C<sub>2</sub>]Pyruvate
Hyperpolarized MRI is emerging as
a next-generation molecular imaging
modality that can detect metabolic transformations in real time deep
inside tissue and organs. 13C-hyperpolarized pyruvate is
the leading hyperpolarized contrast agent that can probe cellular
energetics in real time. Currently, hyperpolarized MRI requires specialized
âmultinuclearâ MRI scanners that have the ability to
excite and detect 13C signals. The objective of this work
is the development of an approach that works on conventional (i.e.,
proton-only) MRI systems while taking advantage of long-lived 13C hyperpolarization. The long-lived singlet state of [1,2-13C2]pyruvate is hyperpolarized with parahydrogen
in reversible exchange, and subsequently, the polarization is transferred
from the 13C2 spin pair to the methyl protons
of pyruvate for detection. This polarization transfer is accomplished
with spin-lock induced crossing pulses that are only applied to the
methyl protons yet access the hyperpolarization stored in the 13C2 singlet state. Theory and first experimental
demonstrations are provided for our method, which obviates 13C excitation and detection for proton sensing of 13C-hyperpolarized
pyruvate with an overall experimental-polarization transfer efficiency
of âŒ22% versus a theoretically predicted polarization transfer
efficiency of 25%
Delivering Robust Proton-Only Sensing of Hyperpolarized [1,2-<sup>13</sup>C<sub>2</sub>]âPyruvate Using Broad-Spectral-Range Nuclear Magnetic Resonance Pulse Sequences
Hyperpolarized
[1-13C]pyruvate is the leading hyperpolarized
injectable contrast agent and is currently under evaluation in clinical
trials for molecular imaging of metabolic diseases, including cardiovascular
disease and cancer. One aspect limiting broad scalability of the technique
is that hyperpolarized 13C MRI requires specialized 13C hardware and software that are not generally available
on clinical MRI scanners, which employ proton-only detection. Here,
we present an approach that uses pulse sequences to transfer 13C hyperpolarization to methyl protons for detection of the 13Câ13C pyruvate singlet, employing proton-only
excitation and detection only. The new pulse sequences are robust
to the B1 and B0 magnetic field inhomogeneities.
The work focuses on singlet-to-magnetization (S2M) and rotor-synchronized
(R) pulses, both relying on trains of hard pulses with broad spectral
width coverage designed to effectively transform hyperpolarized 13C2-singlet hyperpolarization to 1H
polarization on the CH3 group of [1,2-13C2]pyruvate. This approach may enable a broader adoption of
hyperpolarized MRI as a molecular imaging technique
Accessing Long-Lived Disconnected Spinâ<sup>1</sup>/<sub>2</sub> Eigenstates through Spins > <sup>1</sup>/<sub>2</sub>
Pairs of chemically
equivalent (or nearly equivalent) spin-<sup>1</sup>/<sub>2</sub> nuclei
have been shown to create disconnected
eigenstates that are very long-lived compared with the lifetime of
pure magnetization (<i>T</i><sub>1</sub>). Here the classes
of molecules known to have accessible long-lived states are extended
to include those with chemically equivalent spin-<sup>1</sup>/<sub>2</sub> nuclei accessed by coupling to nuclei with spin > <sup>1</sup>/<sub>2</sub>, in this case deuterium. At first, this appears
surprising
because the quadrupolar interactions present in nuclei with spin > <sup>1</sup>/<sub>2</sub> are known to cause fast relaxation. Yet it is
shown that scalar couplings between deuterium and carbon can guide
population into and out of long-lived states, i.e., those immune from
the dominant relaxation mechanisms. This implies that it may be practical
to consider compounds with <sup>13</sup>C pairs directly bound to
deuterium (or even <sup>14</sup>N) as candidates for storage of polarization.
In addition, experiments show that simple deuteration of molecules
with <sup>13</sup>C pairs at their natural abundance is sufficient
for successful lifetime measurements
Storage of Hydrogen Spin Polarization in Long-Lived <sup>13</sup>C<sub>2</sub> Singlet Order and Implications for Hyperpolarized Magnetic Resonance Imaging
Hyperpolarized
magnetic resonance imaging (MRI) is a powerful technique
enabling real-time monitoring of metabolites at concentration levels
not accessible by standard MRI techniques. A considerable challenge
this technique faces is the <i>T</i><sub>1</sub> decay of
the hyperpolarization upon injection into the system under study.
Here we show that A<sub><i>n</i></sub>AâČ<sub><i>n</i></sub>XXâČ spin systems such as <sup>13</sup>C<sub>2</sub>-1,2-diphenylacetylene (<sup>13</sup>C<sub>2</sub>-DPA) sustain
long-lived polarization for both <sup>13</sup>C and <sup>1</sup>H
spins with decay constants of almost 4.5 min at high magnetic fields
of up to 16.44 T without spin-locking; the <i>T</i><sub>1</sub> of proton polarization is only 3.8 s. Therefore, storage
of the proton polarization in a <sup>13</sup>C<sub>2</sub>-singlet
state causes a 69-fold extension of the spin lifetime. Notably, this
extension is demonstrated with proton-only pulse sequences, which
can be readily implemented on standard clinical scanners
High-Resolution Zero-Field NMR <i>J</i>âSpectroscopy of Aromatic Compounds
We report the acquisition and interpretation
of nuclear magnetic
resonance (NMR) <i>J</i>-spectra at zero magnetic field
for a series of benzene derivatives, demonstrating the analytical
capabilities of zero-field NMR. The zeroth-order spectral patterns
do not overlap, which allows for straightforward determination of
the spin interactions of substituent functional groups. Higher-order
effects cause additional line splittings, revealing additional molecular
information. We demonstrate resonance linewidths as narrow as 11 mHz,
permitting resolution of minute frequency differences and precise
determination of long-range <i>J</i>-couplings. The measurement
of <i>J</i>-couplings with the high precision offered by
zero-field NMR may allow further refinements in the determination
of molecular structure and conformation
High-Resolution Zero-Field NMR <i>J</i>âSpectroscopy of Aromatic Compounds
We report the acquisition and interpretation
of nuclear magnetic
resonance (NMR) <i>J</i>-spectra at zero magnetic field
for a series of benzene derivatives, demonstrating the analytical
capabilities of zero-field NMR. The zeroth-order spectral patterns
do not overlap, which allows for straightforward determination of
the spin interactions of substituent functional groups. Higher-order
effects cause additional line splittings, revealing additional molecular
information. We demonstrate resonance linewidths as narrow as 11 mHz,
permitting resolution of minute frequency differences and precise
determination of long-range <i>J</i>-couplings. The measurement
of <i>J</i>-couplings with the high precision offered by
zero-field NMR may allow further refinements in the determination
of molecular structure and conformation
High-Resolution Zero-Field NMR <i>J</i>âSpectroscopy of Aromatic Compounds
We report the acquisition and interpretation
of nuclear magnetic
resonance (NMR) <i>J</i>-spectra at zero magnetic field
for a series of benzene derivatives, demonstrating the analytical
capabilities of zero-field NMR. The zeroth-order spectral patterns
do not overlap, which allows for straightforward determination of
the spin interactions of substituent functional groups. Higher-order
effects cause additional line splittings, revealing additional molecular
information. We demonstrate resonance linewidths as narrow as 11 mHz,
permitting resolution of minute frequency differences and precise
determination of long-range <i>J</i>-couplings. The measurement
of <i>J</i>-couplings with the high precision offered by
zero-field NMR may allow further refinements in the determination
of molecular structure and conformation
Spin Relays Enable Efficient Long-Range Heteronuclear Signal Amplification by Reversible Exchange
A systematic
experimental study is reported on the polarization
transfer to distant spins, which do not directly bind to the polarization
transfer complexes employed in Signal Amplification By Reversible
Exchange (SABRE) experiments. Both long-range transfer to protons
and long-range transfer to heteronuclei, i.e., <sup>13</sup>C and <sup>15</sup>N, are examined. Selective destruction of hyperpolarization
on <sup>1</sup>H, <sup>13</sup>C, and <sup>15</sup>N sites is employed,
followed by their rehyperpolarization from neighboring spins within
the molecules of interest (pyridine for <sup>1</sup>H studies and
metronidazole-<sup>15</sup><i>N</i><sub>2</sub>-<sup>13</sup><i>C</i><sub>2</sub> for <sup>13</sup>C and <sup>15</sup>N studies). We conclude that long-range sites can be efficiently
hyperpolarized when a network of spin-1/2 nuclei enables relayed polarization
transfer (i.e., via short-range interactions between sites). In the
case of proton SABRE in the millitesla regime, a relay network consisting
of protons only is sufficient. However, in case <sup>13</sup>C and <sup>15</sup>N are targeted (i.e., via SABRE in SHield Enables Alignment
Transfer to Heteronuclei or SABRE-SHEATH experiment), the presence
of a heteronuclear network (e.g., consisting of <sup>15</sup>N) enables
a relay mechanism that is significantly more efficient than the direct
transfer of spin order from para-H<sub>2</sub>-derived hydrides
Catalyst-Free Aqueous Hyperpolarized [1-<sup>13</sup>C]Pyruvate Obtained by Re-Dissolution Signal Amplification by Reversible Exchange
Despite
great successes in oncology, patient outcomes are often
still discouraging, and hence the diagnostic imaging paradigm is increasingly
shifting toward functional imaging of the pathology to better understand
individual disease biology and to personalize therapies. The dissolution
Dynamic Nuclear Polarization (d-DNP) hyperpolarization method has
enabled unprecedented real-time MRI sensing of metabolism and tissue
pH using hyperpolarized [1-13C]pyruvate as a biosensor
with great potential for diagnosis and monitoring of cancer patients.
However, current d-DNP is expensive and suffers from long hyperpolarization
times, posing a substantial translational roadblock. Here, we report
the development of Re-Dissolution Signal Amplification By Reversible
Exchange (Re-D SABRE), which relies on fast and low-cost hyperpolarization
of [1-13C]pyruvate by chemical exchange with parahydrogen
at microtesla magnetic fields. [1-13C]pyruvate is precipitated
from catalyst-containing methanol using ethyl acetate and rapidly
reconstituted in aqueous media. 13C polarization of 9 ±
1% is demonstrated after redissolution in water with residual iridium
mass fraction of 8.5 ± 1.5 ppm; further improvement is anticipated
via process automation. Re-D SABRE makes hyperpolarized [1-13C]pyruvate biosensor available at a fraction of the cost (<$10,000)
and production time (â1 min) of currently used techniques and
makes aqueous hyperpolarized [1-13C]pyruvate âreadyâ
for in vivo applications