Abstract There is significant need for effective medical adhesives that function reliably on wet tissue surfaces with minimal inflammatory insult. To address these performance characteristics, we ...have generated a synthetic adhesive biomaterial inspired by the protein glues of marine mussels. In-vivo performance was interrogated in a murine model of extrahepatic syngeneic islet transplantation, as an alternative to standard portal administration. The adhesive precursor polymer consisted of a branched poly(ethylene glycol) (PEG) core, whose endgroups were derivatized with catechol, a functional group abundant in mussel adhesive proteins. Under oxidizing conditions, adhesive hydrogels formed in less than 1 min from catechol-derivatized PEG (cPEG) solutions. Upon implantation, the cPEG adhesive elicited minimal acute or chronic inflammatory response in C57BL6 mice, and maintained an intact interface with supporting tissue for up to one year. In-situ cPEG adhesive formation was shown to efficiently immobilize transplanted islets at the epididymal fat pad and external liver surfaces, permitting normoglycemic recovery and graft revascularization. These findings establish the use of synthetic, biologically-inspired adhesives for islet transplantation at extrahepatic sites.
Mussel-inspired adhesive hydrogels represent innovative candidate medical sealants or glues. In the present work, we describe an enzyme-degradable mussel-inspired adhesive hydrogel formulation, ...achieved by incorporating minimal elastase substrate peptide Ala-Ala into the branched poly(ethylene glycol) (PEG) macromonomer structure. The system takes advantage of neutrophil elastase expression upregulation and secretion from neutrophils upon recruitment to wounded or inflamed tissue. By integrating adhesive degradation behaviors that respond to cellular cues, we expand the functional range of our mussel-inspired adhesive hydrogel platforms. Rapid (<1 min) and simultaneous gelation and adhesion of the proteolytically active, catechol-terminated precursor macromonomer was achieved by addition of sodium periodate oxidant. Rheological analysis and equilibrium swelling studies demonstrated that the hydrogel is appropriate for soft tissue-contacting applications. Notably, hydrogel storage modulus (G′) achieved values on the order of 10 kPa, and strain at failure exceeded 200% strain. Lap shear testing confirmed the material’s adhesive behavior (shear strength: 30.4 ± 3.39 kPa). Although adhesive hydrogel degradation was not observed during short-term (27 h) in vitro treatment with neutrophil elastase, in vivo degradation proceeded over several months following dorsal subcutaneous implantation in mice. This work represents the first example of an enzymatically degradable mussel-inspired adhesive and expands the potential biomedical applications of this family of materials.
The natural world provides many examples of robust, permanent adhesive platforms. Synthetic adhesive interfaces and materials inspired by mussels of genus Mytulis have been extensively applied, and ...it is expected that characterization and adaptation of several other biological adhesive strategies will follow the Mytilus edulis model. These candidate species will be introduced, along with a discussion of the adhesive behaviors that make them attractive for synthetic adaptation. While significant progress has been made in the development of biologically inspired adhesive interfaces and materials, persistent questions, current challenges, and emergent areas of research will be also be discussed.
Although the literature on the Raman spectra of carbon fibers is vast, no consistent, robust predictive relationship between mechanical properties of carbon fibers and spectral parameters exists. ...This shortcoming is due to the use of numerous fitting functions to evaluate Raman spectra of carbon fibers and the inconsistencies in establishing the best fitting models in a statistically robust fashion. To address this gap, we present a comprehensive work on the Raman spectra of carbon fibers that combines a vast library of experimental data with a robust numerical analysis and a statistical evaluation of a wide range of suggested fitting models. This manuscript begins with a brief review of the commonly applied fitting models. Then, the Raman spectra of 32 commercially available polyacrylonitrile-based carbon fibers collected at excitation wavelengths 532, 633, and 785 nm are presented and the best fit for all fibers is evaluated based on several statistical criteria in conjunction with numerical calculations and physical arguments. The results suggest that high-performance fibers must be fit with at least five peaks, whereas high-tensile modulus fibers are best fit with at least six distinct peaks. Finally, we employ simultaneous fitting of the Raman spectra of specific fibers and wavelengths and demonstrate that strong correlations exist between mechanical properties and the D1 peak position and shape across the range of evaluated mechanical properties. We suggest straightforward improvements in fitting analysis procedures that can be implemented to increase coherency in the understanding of the underlying carbon fiber microstructure intuited from Raman spectroscopy.
Graphical Abstract
This paper reports a series of measurements that characterize the directional dependence of the scintillation response of crystalline melt-grown and solution-grown trans-stilbene to incident DT and ...DD neutrons. These measurements give the amplitude and pulse shape dependence on the proton recoil direction over one hemisphere of the crystal, confirming and extending previous results in the literature for melt-grown stilbene and providing the first measurements for solution-grown stilbene. In similar measurements of liquid and plastic detectors, no directional dependence was observed, confirming the hypothesis that the anisotropy in stilbene and other organic crystal scintillators is a result of internal effects due to the molecular or crystal structure and not an external effect on the measurement system.
Previous neuroimaging studies have implicated the prefrontal cortex (PFC) and nearby brain regions in deception. This is consistent with the hypothesis that lying involves the executive control ...system. To date, the nature of the contribution of different aspects of executive control to deception, however, remains unclear. In the present study, we utilized an activation likelihood estimate (ALE) method of meta-analysis to quantitatively identify brain regions that are consistently more active for deceptive responses relative to truthful responses across past studies. We then contrasted the results with additional ALE maps generated for 3 different aspects of executive control: working memory, inhibitory control, and task switching. Deception-related regions in dorsolateral PFC and posterior parietal cortex were selectively associated with working memory. Additional deception regions in ventrolateral PFC, anterior insula, and anterior cingulate cortex were associated with multiple aspects of executive control. In contrast, deception-related regions in bilateral inferior parietal lobule were not associated with any of the 3 executive control constructs. Our findings support the notion that executive control processes, particularly working memory, and their associated neural substrates play an integral role in deception. This work provides a foundation for future research on the neurocognitive basis of deception.
Laves phase alloys possess unique thermal and electrical conduction properties, yet the factors governing phase stability in these systems remain an open question. The influence of phonons in ...particular has been broadly overlooked. Here, we investigate the UCo
2
x
Ni
2(1−
x
)
chemical space using density functional theory, which offers a unique opportunity to explore the factors influencing Laves phase stability as all three primary Laves phases (C14, C15, C36) can be stabilized by changing the ratio of Co to Ni. Calculations of the thermodynamic and dynamical stability of pure UCo
2
and UNi
2
in each of three primary Laves phases confirm the stability of experimentally known Laves phases for UNi
2
and UCo
2
. A decrease in bonding strength is identified in UNi
2
compared to UCo
2
, aligned with redshifts observed in the UNi
2
phonon density of states and a decoupling of the U and Ni vibrational modes. Phonon calculations of C14 UCo
2
reveal dynamical instabilities. Efforts to remove the unstable mode at the
Γ
point in UCo
2
via
atomic displacements break the symmetry of the C14 phase, revealing a lower energy
P
2/
c
structure. Vibrational contributions to the free energy were calculated and did not change the thermodynamically stable Laves phase below 1000 K. The temperature-dependent free energies of single phase UCo
2
and UNi
2
were used to interpolate the relative stability of ternary UCo
2
x
Ni
2(1−
x
)
in each of the three Laves phases at varying temperatures and stoichiometries. The ternary C36 phase is only predicted to be thermodynamically stable over a narrow stoichiometric range below 600 K.
DFT investigations of the thermodynamic stability of UCo
2
and UNi
2
for three Laves phase structure types were extrapolated to UCo
2
x
Ni
2(1−
x
)
.
Plastic, organic scintillators have been tailored in composition to achieve an ultrafast temporal response, thereby enabling the design and development of fast neutron detection systems with high ...timing resolution. Eljen Technology's plastic, organic scintillators-EJ-230, EJ-232, and EJ-232Q-are prospective candidates for use in emerging neutron imaging systems, where fast timing is paramount. To support the neutron response characterization of these materials, the relative proton light yields (PLYs) of EJ-230, EJ-232, and EJ-232Q were measured at the 88-Inch Cyclotron at the Lawrence Berkeley National Laboratory. Using a broad-spectrum neutron source and a double-time-of-flight technique, the PLY relations were obtained over a proton recoil energy range of approximately 300 keV to 4 MeV. The EJ-230, EJ-232, and EJ-232Q scintillators exhibited similar PLY relations to each other and to other plastic scintillators with the same polymer base material. A comparison of the relative PLY of different sized cylindrical EJ-232 and EJ-232Q scintillators also revealed consistent results. This article provides key input data for the realistic computational modeling of neutron detection technologies employing these materials, thereby supporting new capabilities in near-field radionuclide detection for national security applications.
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