Dataset Information

Negative-pressure polymorphs made by heterostructural alloying.

ABSTRACT: The ability of a material to adopt multiple structures, known as polymorphism, is a fascinating natural phenomenon. Various polymorphs with unusual properties are routinely synthesized by compression under positive pressure. However, changing a material's structure by applying tension under negative pressure is much more difficult. We show how negative-pressure polymorphs can be synthesized by mixing materials with different crystal structures-a general approach that should be applicable to many materials. Theoretical calculations suggest that it costs less energy to mix low-density structures than high-density structures, due to less competition for space between the atoms. Proof-of-concept experiments confirm that mixing two different high-density forms of MnSe and MnTe stabilizes a Mn(Se,Te) alloy with a low-density wurtzite structure. This Mn(Se,Te) negative-pressure polymorph has 2× to 4× lower electron effective mass compared to MnSe and MnTe parent compounds and has a piezoelectric response that none of the parent compounds have. This example shows how heterostructural alloying can lead to negative-pressure polymorphs with useful properties-materials that are otherwise nearly impossible to make.

SUBMITTER: Siol S

PROVIDER: S-EPMC5930396 | biostudies-literature | 2018 Apr

REPOSITORIES: biostudies-literature

ACCESS DATA

Publications

Negative-pressure polymorphs made by heterostructural alloying.

Siol Sebastian S Holder Aaron A Steffes James J Schelhas Laura T LT Stone Kevin H KH Garten Lauren L Perkins John D JD Parilla Philip A PA Toney Michael F MF Huey Bryan D BD Tumas William W Lany Stephan S Zakutayev Andriy A

Science advances 20180420 4

The ability of a material to adopt multiple structures, known as polymorphism, is a fascinating natural phenomenon. Various polymorphs with unusual properties are routinely synthesized by compression under positive pressure. However, changing a material's structure by applying tension under negative pressure is much more difficult. We show how negative-pressure polymorphs can be synthesized by mixing materials with different crystal structures-a general approach that should be applicable to many ...[more]

PMID: 29725620

Similar Datasets

Project description:Pressure sensitive adhesives made with blends of thermoplastic polyurethanes (TPUs PSAs) with satisfactory tack, cohesion, and adhesion have been developed. A simple procedure consisting of the physical blending of methyl ethyl ketone (MEK) solutions of two thermoplastic polyurethanes (TPUs) with very different properties-TPU1 and TPU2-was used, and two different blending procedures have been employed. The TPUs were characterized by infra-red spectroscopy in attenuated total reflectance mode (ATR-IR spectroscopy), differential scanning calorimetry, thermal gravimetric analysis, and plate-plate rheology (temperature and frequency sweeps). The TPUs PSAs were characterized by tack measurement, creep test, and the 180° peel test at 25 °C. The procedure for preparing the blends of the TPUs determined differently their viscoelastic properties, and the properties of the TPUs PSAs as well, the blending of separate MEK solutions of the two TPUs imparted higher tack and 180° peel strength than the blending of the two TPUs in MEK. TPU1 + TPU2 blends showed somewhat similar contributions of the free and hydrogen-bonded urethane groups and they had an almost similar degree of phase separation, irrespective of the composition of the blend. Two main thermal decompositions at 308-317 °C due to the urethane hard domains and another at 363-373 °C due to the soft domains could be distinguished in the TPU1 + TPU2 blends, the weight loss of the hard domains increased and the one of the soft domains decreased by increasing the amount of TPU2 in the blends. The storage moduli of the TPU1 + TPU2 blends were similar for temperatures lower than 20 °C and the moduli at the cross over of the moduli were lower than in the parent TPUs. The improved properties of the TPU1 + TPU2 blends derived from the creation of a higher number of hydrogen bonds upon removal of the MEK solvent, which lead to a lower degree of phase separation between the soft and the hard domains than in the parent TPUs. As a consequence, the properties of the TPU1 + TPU2 PSAs were improved because good tack, high 180° peel strength, and sufficient cohesion were obtained, particularly in 70 wt% TPU1 + 30 wt% TPU2 PSA.

Project description:Introduction: The use of negative pressure dressings for open abdominal therapy has made a great impact on strategies for open abdominal treatment. Observed intestinal damage and developement of fistula formation raises questions about safety of commonly used systems (AB-Thera). The most common used system uses foils for shielding intestines directly from negative pressure. As an alternative a system with open pore dressing in double layer film was introduced (Suprasorb CNP) and proved to safe in animal studies. We compared the effects of this two systems on patients requiring open abdominal treatment. Materials and methods: Patients with secondary peritonitis in at least two abdominal quadrants were included in this randomized study. Inclusion criteria were secondary peritonitis (ACS), abdominal compartment syndrome, and abdominal trauma combined with ACS and/or contaminated abdomen. Patients with active bleeding and pancreatitis were not included. We examined Mannheim peritonitis Index (MPI), bloodcount, PCT, amount of fluid collected, and morphological changes on the bowel. Data were collected on day 2, 4, 7, 14, 21, and 28. Primary end point was fascial closure. Examination was terminated in case of death and damage to the abdominal organs. Groups were compared using Mann Whitney U-test and chi square test. Trend evaluation was evaluated using an one way repeated measure analysis of variance. P-values below 0.05 was considered significat. Results: Thirty four patients were included between August 2010 and September 2012. There were no significant difference between two groups in MPI, age, and gender. Mean duration of treatment, WBC, CRP, and abdominal closure rate were not significantly different between groups. Suprasorb CNP System collected twice more fluid than AB-Thera and decreased PCT on significantly faster rate than AB-Thera. Four patients died (11%) and four patients developed enteric fistula (11%). Closure rate was achieved in 27 out of 34 Patients (79.5%). Closure rate was not significantly different between groups. Conclusion: The use of both systems proved to be efficient and safe. The application of well-dosed, moderate negative pressure on contaminated areas of the abdomen seems to have a lot of potential and it is worth directing greater research potential in this direction.

Project description:Background: Negative-pressure wound therapy has become widely available in modern chronic wound cares. Accelerated keratinocyte (HaCaT cell) movements and decreased E-cadherin expressions induced by the applied negative pressure gradient of 125 mmHg (NP) have been reported in previous studies. However, the molecular mechanism for E-cadherin regulations under NP remains unexplored. We highlighted the signal transduction involved in NP-induced E-cadherin regulation for keratinocytes in the study. Results: Microarray results showed that catenin 1 (CTNND1) gene, the gene encoding the p120-catenin (p120ctn) in cell-cell junctions, was significantly (p = 0.0005) upregulated in HaCaT cells under NP for 12 hours in comparison with those at ambient pressure (AP). Cell fractionations and immunoblotting data showed that NP increased p120ctn phosphorylation, and resulted in p120ctn translocation from the plasma membrane to the cytoplasm. Fluorescent stains suggested that NP diminished the co-localization of p120ctn and E-cadherin on the plasma membrane. Similar phenomenon was also observed in the cells with overexpressed p120ctn at NP. Interestingly, overexpression of dN- p120ctn, a deletion mutant of p120ctn without the N-terminal phosphorylation sites, restored the adherens junctions (AJ) at NP. Knockdown of p120ctn with lentiviral small hairpin RNA not only diminished E-cadherin expressions but also accelerated cell movement at AP. Conclusions: Phosphorylation of p120ctn is endowed to respond rapidly to NP and contributes to the AJ disassembly. This NP-induced E-cadherin downregulation can possibly accelerate wound-healing process. Conclusions: Phosphorylation of p120ctn is endowed to respond rapidly to NP and contributes to the AJ disassembly. This NP-induced E-cadherin downregulation can possibly accelerate wound-healing process. HaCaT cells under negative pressure (NP) gradient of 125 mmHg for 12 hours in comparison with those at ambient pressure (AP) were tested for RNA extraction and hybridization on Affymetrix microarrays. The experiments have been biological replicated three times. The differential expression gene between NP and AP were selected and validated with qPCR method.

Dataset Information

Negative-pressure polymorphs made by heterostructural alloying.

Publications

Negative-pressure polymorphs made by heterostructural alloying.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets