Thermal quench effects on ferroelectric domain walls

Using piezoresponse force microscopy on epitaxial ferroelectric thin films, we have measured the evolution of domain wall roughening as a result of heat-quench cycles up to 735C, with the effective roughness exponent \zeta\ changing from 0.25 to 0.5. We discuss two possible mechanisms for the observed \zeta\ increase: a quench from a thermal 1-dimensional configuration, and from a locally-equilibrated pinned configuration with a crossover from a 2- to 1-dimensional regime. We find that the post-quench spatial structure of the metastable states, qualitatively consistent with the existence of a growing dynamical length scale whose ultra slow evolution is primarily controlled by the defect configuration and heating process parameters, makes the second scenario more plausible. This interpretation suggests that pinning is relevant in a wide range of temperatures, and in particular, that purely thermal domain wall configurations might not be observable in this glassy system. We also demonstrate the crucial effects of oxygen vacancies in stabilizing domain structures.Comment: 17 pages (preprint), 4 figure

Perceived Behavioral Control, Stress, Body Image, and Exercise Intentions in Overweight African American Women

A disproportionate number of African American women are at risk for illness and mortality due to obesity. The aim of this study was to explore perceived behavioral control (PBC), stress, body image, and exercise intentions (EI) using the theory of planned behavior (TPB) as the primary theoretical framework. The TPB is a leading model in health research to predict behavioral intentions, yet its application to the general female African American population is lacking. Seventy-nine African American women were sampled utilizing a cross-sectional, online survey method. A series of bivariate correlations tested the relationships among PBC, stress, body image, age, and physical activity with EI as the dependent variable. Findings showed that PBC and EI were significantly correlated (r = .62, p\u3c.001). There was also a significant correlation between physical activity level and EI (r = .34, p=.003). Stress, body image, and age were not significantly correlated with EI. A standard multiple regression analysis was used to test if PBC, stress, and body image significantly predicted EI. PBC and stress explained 42% of the variance (R-² = .42, F(3,75)=18.49, p\u3c.001). These findings highlight the importance of strengthening PBC beliefs and reducing stress to enhance successful weight loss. Social change implications include a culturally-sensitive approach to weight loss that could help decrease obesity rates and related health problems

Multiscaling analysis of ferroelectric domain wall roughness

Using multiscaling analysis, we compare the characteristic roughening of ferroelectric domain walls in PZT thin films with numerical simulations of weakly pinned one-dimensional interfaces. Although at length scales up to a length scale greater or equal to 5 microns the ferroelectric domain walls behave similarly to the numerical interfaces, showing a simple mono-affine scaling (with a well-defined roughness exponent), we demonstrate more complex scaling at higher length scales, making the walls globally multi-affine (varying roughness exponent at different observation length scales). The dominant contributions to this multi-affine scaling appear to be very localized variations in the disorder potential, possibly related to dislocation defects present in the substrate.Comment: 5 pages, 4 figure

Molecular dynamics simulations of energetic Ar cluster bombardment of Ag(111)

Large-scale molecular dynamics computer simulations are used to investigate the dynamics of material ejection during high-energy Ar_{n} cluster bombardment of Ag(111) at normal incidence. The silver sample containing 7 million atoms is bombarded with Ar_{n} projectiles (n=45-30000) with kinetic energy spanning from a few keV up to 1 MeV. Such a wide range of projectile parameters allows probing processes taking place during low-density collision cascade as well as during high-density events characteristic of micrometeorite bombardment in space. The material modifications and total sputtering yield of ejected particles are investigated. While at low-energy impacts, ejection of individual silver atoms is the main emission channel, the ejection of large clusters from the corona of the created crater dominates for the high-energy impacts

Sputtering of benzene sample by large Ne, Ar and Kr clusters : molecular dynamics computer simulations

Molecular dynamics simulations are employed to probe the role of an impact angle on emission efficiency of organic molecules sputtered from benzene crystal bombarded by 15 keV $Ne_{2953}$, $Ar_{2953}$, and $Kr_{2953}$ clusters. It is found that both the cluster type and the angle of incidence have significant effect on the emission efficiency. The shape of the impact angle dependence does not resemble the dependence characteristic for medium size clusters ($C_{60}, Ar_{366}$), where sputtering yield only moderately increases with the impact angle, has a shallow maximum around 40° and then decreases. On the contrary, for the large projectiles ($Ne_{2953}, Ar_{2953}$, and $Kr_{2953}$) the emission efficiency steeply increases with the impact angle, has a pronounced maximum around 55° followed by rapid signal decay. It has been found that the sputtering yield is the most sensitive to the impact angle change for Kr cluster projectiles, while change of the impact angle of Ne projectile has the smallest effect on the efficiency of material ejection

Introducing Semi-Interpenetrating Networks of Chitosan and Ammonium-Quaternary Polymers for the Effective Removal of Waterborne Pathogens from Wastewaters

The present work aims to study the influence of ammonium-quaternary monomers and chitosan, obtained from different sources, upon the effect of semi-interpenetrating polymer network (semi-IPN) hydrogels upon the removal of waterborne pathogens and bacteria from wastewater. To this end, the study was focused on using vinyl benzyl trimethylammonium chloride (VBTAC), a water-soluble monomer with known antibacterial properties, and mineral-enriched chitosan extracted from shrimp shells, to prepare the semi-IPNs. By using chitosan, which still contains the native minerals (mainly calcium carbonate), the study intends to justify that the stability and efficiency of the semi-IPN bactericidal devices can be modified and better improved. The new semi-IPNs were characterized for composition, thermal stability and morphology using well-known methods. Swelling degree (SD%) and the bactericidal effect assessed using molecular methods revealed that hydrogels made of chitosan derived from shrimp shell demonstrated the most competitive and promising potential for wastewater (WW) treatment.Introducing Semi-Interpenetrating Networks of Chitosan and Ammonium-Quaternary Polymers for the Effective Removal of Waterborne Pathogens from WastewaterspublishedVersio

The CHK1 inhibitor MU380 significantly increases the sensitivity of human docetaxel-resistant prostate cancer cells to gemcitabine through the induction of mitotic catastrophe.

As treatment options for patients with incurable metastatic castration-resistant prostate cancer (mCRPC) are considerably limited, novel effective therapeutic options are needed. Checkpoint kinase 1 (CHK1) is a highly conserved protein kinase implicated in the DNA damage response (DDR) pathway that prevents the accumulation of DNA damage and controls regular genome duplication. CHK1 has been associated with prostate cancer (PCa) induction, progression, and lethality; hence, CHK1 inhibitors SCH900776 (also known as MK-8776) and the more effective SCH900776 analog MU380 may have clinical applications in the therapy of PCa. Synergistic induction of DNA damage with CHK1 inhibition represents a promising therapeutic approach that has been tested in many types of malignancies, but not in chemoresistant mCRPC. Here, we report that such therapeutic approach may be exploited using the synergistic action of the antimetabolite gemcitabine (GEM) and CHK1 inhibitors SCH900776 and MU380 in docetaxel-resistant (DR) mCRPC. Given the results, both CHK1 inhibitors significantly potentiated the sensitivity to GEM in a panel of chemo-naïve and matched DR PCa cell lines under 2D conditions. MU380 exhibited a stronger synergistic effect with GEM than clinical candidate SCH900776. MU380 alone or in combination with GEM significantly reduced spheroid size and increased apoptosis in all patient-derived xenograft 3D cultures, with a higher impact in DR models. Combined treatment induced premature mitosis from G1 phase resulting in the mitotic catastrophe as a prestage of apoptosis. Finally, treatment by MU380 alone, or in combination with GEM, significantly inhibited tumor growth of both PC339-DOC and PC346C-DOC xenograft models in mice. Taken together, our data suggest that metabolically robust and selective CHK1 inhibitor MU380 can bypass docetaxel resistance and improve the effectiveness of GEM in DR mCRPC models. This approach might allow for dose reduction of GEM and thereby minimize undesired toxicity and may represent a therapeutic option for patients with incurable DR mCRPC

In silico design of novel probes for the atypical opioid receptor MRGPRX2

The primate-exclusive MRGPRX2 G protein-coupled receptor (GPCR) has been suggested to modulate pain and itch. Despite putative peptide and small molecule MRGPRX2 agonists, selective nanomolar potency probes have not yet been reported. To identify a MRGPRX2 probe, we first screened 5,695 small molecules and found many opioid compounds activated MRGPRX2, including (−)- and (+)-morphine, hydrocodone, sinomenine, dextromethorphan and the prodynorphin-derived peptides, dynorphin A, dynorphin B, and α- and β-neoendorphin. We used these to select for mutagenesis-validated homology models and docked almost 4 million small molecules. From this docking, we predicted ZINC-3573, which represents a potent MRGPRX2-selective agonist, showing little activity against 315 other GPCRs and 97 representative kinases, and an essentially inactive enantiomer. ZINC-3573 activates endogenous MRGPRX2 in a human mast cell line inducing degranulation and calcium release. MRGPRX2 is a unique atypical opioid-like receptor important for modulating mast cell degranulation, which can now be specifically modulated with ZINC-3573

The CHK1 inhibitor MU380 significantly increases the sensitivity of human docetaxel-resistant prostate cancer cells to gemcitabine through the induction of mitotic catastrophe

As treatment options for patients with incurable metastatic castration-resistant prostate cancer (mCRPC) are considerably limited, novel effective therapeutic options are needed. Checkpoint kinase 1 (CHK1) is a highly conserved protein kinase implicated in the DNA damage response (DDR) pathway that prevents the accumulation of DNA damage and controls regular genome duplication. CHK1 has been associated with prostate cancer (PCa) induction, progression, and lethality; hence, CHK1 inhibitors SCH900776 (also known as MK-8776) and the more effective SCH900776 analog MU380 may have clinical applications in the therapy of PCa. Synergistic induction of DNA damage with CHK1 inhibition represents a promising therapeutic approach that has been tested in many types of malignancies, but not in chemoresistant mCRPC. Here, we report that such therapeutic approach may be exploited using the synergistic action of the antimetabolite gemcitabine (GEM) and CHK1 inhibitors SCH900776 and MU380 in docetaxel-resistant (DR) mCRPC. Given the results, both CHK1 inhibitors significantly potentiated the sensitivity to GEM in a panel of chemo-naïve and matched DR PCa cell lines under 2D conditions. MU380 exhibited a stronger synergistic effect with GEM than clinical candidate SCH900776. MU380 alone or in combination with GEM significantly reduced spheroid size and increased apoptosis in all patient-derived xenograft 3D cultures, with a higher impact in DR models. Combined treatment induced premature mitosis from G1 phase resulting in the mitotic catastrophe as a prestage of apoptosis. Finally, treatment by MU380 alone, or in combination with GEM, significantly inhibited tumor growth of both PC339-DOC and PC346C-DOC xenograft models in mice. Taken together, our data suggest that metabolically robust and selective CHK1 inhibitor MU380 can bypass docetaxel resistance and improve the effectiveness of GEM in DR mCRPC models. This approach might allow for dose reduction of GEM and thereby minimize undesired toxicity and may represent a therapeutic o