487 research outputs found
Structural, Vibrational and Electronic Properties of Single Layer Hexagonal Crystals of Groups IV and V
Using first-principles density functional theory calculations, we investigate
a family of stable two-dimensional crystals with chemical formula ,
where and belong to groups IV and V, respectively ( = C, Si, Ge, Sn,
Pb; = N, P, As, Sb, Bi). Two structural symmetries of hexagonal lattices
and are shown to be dynamically stable, named as
- and -phases correspondingly. Both phases have similar cohesive
energies, and the -phase is found to be energetically favorable for
structures except CP, CAs, CSb and CBi, for which the -phase is favored.
The effects of spin-orbit coupling and Hartree-Fock corrections to
exchange-correlation are included to elucidate the electronic structures. All
structures are semiconductors except CBi and PbN, which have metallic
character. SiBi, GeBi and SnBi have direct band gaps, whereas the remaining
semiconductor structures have indirect band gaps. All structures have quartic
dispersion in their valence bands, some of which make the valence band maximum
and resemble a Mexican hat shape. SnAs and PbAs have purely quartic valence
band edges, i.e. , a property reported for the first
time. The predicted materials are candidates for a variety of applications.
Owing to their wide band gaps, CP, SiN, SiP, SiAs, GeN, GeP can find their
applications in optoelectronics. The relative band positions qualify a number
of the structures as suitable for water splitting, where CN and SiAs are
favorable at all pH values. Structures with quartic band edges are expected to
be efficient for thermoelectric applications
Amyloid Inspired Self-Assembled Peptide Nanofibers
Cataloged from PDF version of article.Amyloid peptides are important components in many degenerative
diseases as well as in maintaining cellular metabolism. Their unique stable structure
provides new insights in developing new materials. Designing bioinspired selfassembling
peptides is essential to generate new forms of hierarchical nanostructures.
Here we present oppositely charged amyloid inspired peptides (AIPs),
which rapidly self-assemble into nanofibers at pH 7 upon mixing in water caused
by noncovalent interactions. Mechanical properties of the gels formed by selfassembled
AIP nanofibers were analyzed with oscillatory rheology. AIP gels
exhibited strong mechanical characteristics superior to gels formed by self-assembly
of previously reported synthetic short peptides. Rheological studies of gels
composed of oppositely charged mixed AIP molecules (AIP-1 + 2) revealed superior mechanical stability compared to individual
peptide networks (AIP-1 and AIP-2) formed by neutralization of net charges through pH change. Adhesion and elasticity
properties of AIP mixed nanofibers and charge neutralized AIP-1, AIP-2 nanofibers were analyzed by high resolution force−
distance mapping using atomic force microscopy (AFM). Nanomechanical characterization of self-assembled AIP-1 + 2, AIP-1,
and AIP-2 nanofibers also confirmed macroscopic rheology results, and mechanical stability of AIP mixed nanofibers was higher
compared to individual AIP-1 and AIP-2 nanofibers self-assembled at acidic and basic pH, respectively. Experimental results were
supported with molecular dynamics simulations by considering potential noncovalent interactions between the amino acid
residues and possible aggregate forms. In addition, HUVEC cells were cultured on AIP mixed nanofibers at pH 7 and biocompatibility
and collagen mimetic scaffold properties of the nanofibrous system were observed. Encapsulation of a zwitterionic
dye (rhodamine B) within AIP nanofiber network was accomplished at physiological conditions to demonstrate that this network
can be utilized for inclusion of soluble factors as a scaffold for cell culture studies. Copyright © 2012 American Chemical Societ
Gemcitabine Integrated Nano-Prodrug Carrier System
Peptide nanomaterials have received a great deal of interest in drug-delivery applications due to their biodegradability, biocompatibility, suitability for large-scale synthesis, high drug-loading capacities, targeting ability, and ordered structural organization. The covalent conjugation of drugs to peptide backbones results in prolonged circulation time and improved stability of drugs. Therapeutic efficacy of gemcitabine, which is used for breast cancer treatment, is severely compromised due to its rapid plasma degradation. Its hydrophilic nature poses a challenge for both its efficient encapsulation into nanocarrier systems and its sustained release property. Here, we designed a new peptide prodrug molecule for the anticancer drug gemcitabine, which was covalently conjugated to the C-terminal of 9-fluorenylmethoxy carbonyl (Fmoc)-protected glycine. The prodrug was further integrated into peptide nanocarrier system through noncovalent interactions. A pair of oppositely charged amyloid-inspired peptides (Fmoc-AIPs) were exploited as components of the drug-carrier system and self-assembled into one-dimensional nanofibers at physiological conditions. The gemcitabine integrated nanoprodrug carrier system exhibited slow release and reduced the cellular viability of 4T1 breast cancer cell line in a time- and concentration-dependent manner. © 2017 American Chemical Society
An alternative surgical approach to subclavian and innominate stenosis: a case series
We report three cases of symptomatic stenosis of the great vessels or supra-aortic trunks successfully treated surgically with aorto-subclavian and aorto-innominate bypass. Two were performed via manubriotomy and a third case via standard median sternotomy because of concomitant coronary revascularisation. There was complete symptomatic relief on follow-up, and radiological imaging confirmed good flow in the grafts and post-stenotic arteries
Exposure of mediterranean countries to ocean acidification
This study examines the potential effects of ocean acidification on countries and fisheries of the Mediterranean Sea. The implications for seafood security and supply are evaluated by examining the sensitivity of the Mediterranean to ocean acidification at chemical, biological, and macro-economic levels. The limited information available on impacts of ocean acidification on harvested (industrial, recreational, and artisanal fishing) and cultured species (aquaculture) prevents any biological impact assessment. However, it appears that non-developed nations around the Mediterranean, particularly those for which fisheries are increasing, yet rely heavily on artisanal fleets, are most greatly exposed to socioeconomic consequences from ocean acidification. © 2014 by the authors; licensee MDPI, Basel, Switzerland
Label-Free Nanometer-Resolution Imaging of Biological Architectures through Surface Enhanced Raman Scattering
Label free imaging of the chemical environment of biological specimens would readily bridge the supramolecular and the cellular scales, if a chemical fingerprint technique such as Raman scattering can be coupled with super resolution imaging. We demonst
Oncocytic carcinoma of the parotid gland with late cervical lymph node metastases: a case report
<p>Abstract</p> <p>Introduction</p> <p>Oncocytic carcinoma is a rare proliferation of cytomorphologically malignant oncocytes mainly found in glandular tissue, accounting for 0.5% of all epithelial salivary gland malignancies and 0.18% of all epithelial salivary gland tumors.</p> <p>Case presentation</p> <p>We report a case of oncocytic carcinoma arising in the parotid gland of a 65-year-old Caucasian man. Our patient initially underwent left superficial parotidectomy, including the removal of the mass. A close follow-up was made, and four years after first surgery cervical lymph node metastases were confirmed. Therefore, a complete parotidectomy and radical neck dissections were performed. There were no complications and no sign of recurrence after six months of follow-up.</p> <p>Conclusion</p> <p>Oncocytic carcinoma is an extremely rare malignancy in the salivary glands. Prophylactic neck dissection may be indicated for tumors larger than 2 cm in diameter (our patient's tumor was 2.5 cm at its greatest diameter). The clinical course of our patient, with the appearance of cervical lymph node metastases after four years of follow-up, supports this approach. Further investigation of the prognosis and correct treatment of patients with oncocytic carcinoma are required as more cases are reported.</p
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