Sequential piezoresponse force microscopy and the 'small-data' problem

The term big-data in the context of materials science not only stands for the volume, but also for the heterogeneous nature of the characterization data-sets. This is a common problem in combinatorial searches in materials science, as well as chemistry. However, these data-sets may well be 'small' in terms of limited step-size of the measurement variables. Due to this limitation, application of higher-order statistics is not effective, and the choice of a suitable unsupervised learning method is restricted to those utilizing lower-order statistics. As an interesting case study, we present here variable magnetic-field Piezoresponse Force Microscopy (PFM) study of composite multiferroics, where due to experimental limitations the magnetic field dependence of piezoresponse is registered with a coarse step-size. An efficient extraction of this dependence, which corresponds to the local magnetoelectric effect, forms the central problem of this work. We evaluate the performance of Principal Component Analysis (PCA) as a simple unsupervised learning technique, by pre-labeling possible patterns in the data using Density Based Clustering (DBSCAN). Based on this combinational analysis, we highlight how PCA using non-central second-moment can be useful in such cases for extracting information about the local material response and the corresponding spatial distribution

Investigation of structural, magnetic and dielectric properties of gallium substituted Z-type Sr3Co2-xGaxFe24O41 hexaferrites for microwave absorbers

Gallium substituted Z-type hexagonal ferrites with chemical composition Sr3Co2-xGaxFe24O41 (x = 0.0,0.4, 0.8, 1.2, 1.6, and 2.0) were successfully synthesised in air at 1200 °C for 5 h using the sol-gel auto-combustion technique, in order to investigate the effect of gallium substitution on structural, magnetic and dielectric properties. X-ray Diffraction (XRD) analysis of all samples reveals the formation of mixed hexaferrite phases, with Z ferrite as the major phase (72–90%).The average crystallite size of heated powders was found to be in the range of 21–40 nm. The saturation magnetisation decreases after gallium substitution, with the lowest values of 64 Am2 kg−1 for composition x = 1.6, which also hasthe highest value of coercivity (28.3 kA m−1). Nevertheless, all were soft ferrites, with Hc between 3.4 and 28.3 kA m−1.The Mr/MS ratio of all samples was found to be less than 0.5, suggesting that all the compositions possess multi-domain microstructures. Mössbauer spectroscopic analysis confirmed that the Fe ions were found in the 3 + high spin state for compositions below x ≤ 0.4, whereas ∼1.5% of the Fe ions were converted into Fe2+ high spin state beyond x ≥ 0.8 compositions, as Ga3+ began to substitute for Fe3+, forming Fe2+ in the cobalt positions. The average hyperfine magnetic field () was found to be decreased with Ga-substitution. Dielectric parameters such as dielectric constant and loss factor were studied as a function of frequency, and their results show normal behaviour for ferrimagnetic materials. In complex measurements at microwave frequencies (8 GHz–12.5 GHz, the X-band), all samples had a real permittivity of around 8–14. For sample x = 2.0, a dielectric resonance peak was observed around 12.15 GHz. All showed a real permeability of around 1.0–1.4 over the frequency of 8 GHz–12.5 GHz range, and ferromagnetic resonance (FMR) was observed in x = 0.0 and 2.0 samples, at around 11 and 12 GHz, respectively. This suggests that the prepared samples can be used as microwave absorbers/EMI shielding at specific microwave frequencies. The co-existence of FMR and dielectric resonance at the same frequency of 12.15 GHz for x = 2.0 could lead to the coupling of these resonances and the development of potential metamaterials

Alterations in vasodilator-stimulated phosphoprotein (VASP) phosphorylation: associations with asthmatic phenotype, airway inflammation and β(2)-agonist use

BACKGROUND: Vasodilator-stimulated phosphoprotein (VASP) mediates focal adhesion, actin filament binding and polymerization in a variety of cells, thereby inhibiting cell movement. Phosphorylation of VASP via cAMP and cGMP dependent protein kinases releases this "brake" on cell motility. Thus, phosphorylation of VASP may be necessary for epithelial cell repair of damage from allergen-induced inflammation. Two hypotheses were examined: (1) injury from segmental allergen challenge increases VASP phosphorylation in airway epithelium in asthmatic but not nonasthmatic normal subjects, (2) regular in vivo β(2)-agonist use increases VASP phosphorylation in asthmatic epithelium, altering cell adhesion. METHODS: Bronchial epithelium was obtained from asthmatic and non-asthmatic normal subjects before and after segmental allergen challenge, and after regularly inhaled albuterol, in three separate protocols. VASP phosphorylation was examined in Western blots of epithelial samples. DNA was obtained for β(2)-adrenergic receptor haplotype determination. RESULTS: Although VASP phosphorylation increased, it was not significantly greater after allergen challenge in asthmatics or normals. However, VASP phosphorylation in epithelium of nonasthmatic normal subjects was double that observed in asthmatic subjects, both at baseline and after challenge. Regularly inhaled albuterol significantly increased VASP phosphorylation in asthmatic subjects in both unchallenged and antigen challenged lung segment epithelium. There was also a significant increase in epithelial cells in the bronchoalveolar lavage of the unchallenged lung segment after regular inhalation of albuterol but not of placebo. The haplotypes of the β(2)-adrenergic receptor did not appear to associate with increased or decreased phosphorylation of VASP. CONCLUSION: Decreased VASP phosphorylation was observed in epithelial cells of asthmatics compared to nonasthmatic normals, despite response to β-agonist. The decreased phosphorylation does not appear to be associated with a particular β(2)-adrenergic receptor haplotype. The observed decrease in VASP phosphorylation suggests greater inhibition of actin reorganization which is necessary for altering attachment and migration required during epithelial repair

The isothiocyanate class of bioactive nutrients covalently inhibit the MEKK1 protein kinase

<p>Abstract</p> <p>Background</p> <p>Dietary isothiocyanates (ITCs) are electrophilic compounds that have diverse biological activities including induction of apoptosis and effects on cell cycle. They protect against experimental carcinogenesis in animals, an activity believed to result from the transcriptional induction of "Phase 2" enzymes. The molecular mechanism of action of ITCs is unknown. Since ITCs are electrophiles capable of reacting with sulfhydryl groups on amino acids, we hypothesized that ITCs induce their biological effects through covalent modification of proteins, leading to changes in cell regulatory events. We previously demonstrated that stress-signaling kinase pathways are inhibited by other electrophilic compounds such as menadione. We therefore tested the effects of nutritional ITCs on MEKK1, an upstream regulator of the SAPK/JNK signal transduction pathway.</p> <p>Methods</p> <p>The activity of MEKK1 expressed in cells was monitored using in vitro kinase assays to measure changes in catalytic activity. The activity of endogenous MEKK1, immunopurified from ITC treated and untreated LnCAP cells was also measured by in vitro kinase assay. A novel labeling and affinity reagent for detection of protein modification by ITCs was synthesized and used in competition assays to monitor direct modification of MEKK1 by ITC. Finally, immunoblots with phospho-specific antibodies were used to measure the activity of MAPK protein kinases.</p> <p>Results</p> <p>ITCs inhibited the MEKK1 protein kinase in a manner dependent on a specific cysteine residue in the ATP binding pocket. Inhibition of MEKK1 catalytic activity was due to direct, covalent and irreversible modification of the MEKK1 protein itself. In addition, ITCs inhibited the catalytic activity of endogenous MEKK1. This correlated with inhibition of the downstream target of MEKK1 activity, i.e. the SAPK/JNK kinase. This inhibition was specific to SAPK, as parallel MAPK pathways were unaffected.</p> <p>Conclusion</p> <p>These results demonstrate that MEKK1 is directly modified and inhibited by ITCs, and that this correlates with inhibition of downstream activation of SAPK. These results support the conclusion that ITCs may carry out many of their actions by directly targeting important cell regulatory proteins.</p

A Biphasic and Brain-Region Selective Down-Regulation of Cyclic Adenosine Monophosphate Concentrations Supports Object Recognition in the Rat

Background: We aimed to further understand the relationship between cAMP concentration and mnesic performance. Methods and Findings: Rats were injected with milrinone (PDE3 inhibitor, 0.3 mg/kg, i.p.), rolipram (PDE4 inhibitor, 0.3 mg/ kg, i.p.) and/or the selective 5-HT4R agonist RS 67333 (1 mg/kg, i.p.) before testing in the object recognition paradigm. Cyclic AMP concentrations were measured in brain structures linked to episodic-like memory (i.e. hippocampus, prefrontal and perirhinal cortices) before or after either the sample or the testing phase. Except in the hippocampus of rolipram treated-rats, all treatment increased cAMP levels in each brain sub-region studied before the sample phase. After the sample phase, cAMP levels were significantly increased in hippocampus (1.8 fold), prefrontal (1.3 fold) and perirhinal (1.3 fold) cortices from controls rat while decreased in prefrontal cortex (,0.83 to 0.62 fold) from drug-treated rats (except for milrinone+RS 67333 treatment). After the testing phase, cAMP concentrations were still increased in both the hippocampus (2.76 fold) and the perirhinal cortex (2.1 fold) from controls animals. Minor increase were reported in hippocampus and perirhinal cortex from both rolipram (respectively, 1.44 fold and 1.70 fold) and milrinone (respectively 1.46 fold and 1.56 fold)-treated rat. Following the paradigm, cAMP levels were significantly lower in the hippocampus, prefrontal and perirhinal cortices from drug-treated rat when compared to controls animals, however, only drug-treated rats spent longer time exploring the novel object during the testing phase (inter-phase interval of 4 h)

Somatostatin Inhibits Cell Migration and Reduces Cell Counts of Human Keratinocytes and Delays Epidermal Wound Healing in an Ex Vivo Wound Model

The peptide hormone somatostatin (SST) and its five G protein-coupled receptors (SSTR1-5) were described to be present in the skin, but their cutaneous function(s) and skin-specific signalling mechanisms are widely unknown. By using receptor specific agonists we show here that the SSTRs expressed in keratinocytes are functionally coupled to the inhibition of adenylate cyclase. In addition, treatment with SSTR4 and SSTR5/1 specific agonists significantly influences the MAP kinase signalling pathway. As epidermal hormone receptors in general are known to regulate re-epithelialization following skin injury, we investigated the effect of SST on cell counts and migration of human keratinocytes. Our results demonstrate a significant inhibition of cell migration and reduction of cell counts by SST. We do not observe an effect on apoptosis and necrosis. Analysis of signalling pathways showed that somatostatin inhibits cell migration independent of its effect on cAMP. Migrating keratinocytes treated with SST show altered cytoskeleton dynamics with delayed lamellipodia formation. Furthermore, the activity of the small GTPase Rac1 is diminished, providing evidence for the control of the actin cytoskeleton by somatostatin receptors in keratinocytes. While activation of all receptors leads to redundant effects on cell migration, only treatment with a SSTR5/1 specific agonist resulted in decreased cell counts. In accordance with reduced cell counts and impaired migration we observe delayed re-epithelialization in an ex vivo wound healing model. Consequently, our experiments suggest SST as a negative regulator of epidermal wound healing

Profiling the mental health of diabetic patients: a cross-sectional survey of Zimbabwean patients

Objective The burden of diabetes mellitus has exponentially increased in low resource settings. Patients with diabetes are more likely to exhibit poor mental health which negatively affects treatment outcomes. However, patients with high levels of social support (SS) are likely to report optimal mental health. We sought to determine how SS affects the report of psychiatric morbidity and health-related quality of life (HRQoL) in 108 diabetic patients in Harare, Zimbabwe. Results The average age of participants was 54.1 (SD 18.6) years. Most of the participants were; females (69.4%), married (51.9%), and were of low level of income (43.5%). 37.1% of the participants exhibited signs of psychiatric morbidity [mean Shona Symptoms Questionnaire score—6.7 (SD 3.2)]. Further, patients also reported lower HRQoL [mean EQ-5D-VAS score—64.1 (SD 15.3)] and high levels of SS [mean Multidimensional Scale of Perceived Social Support score—43.7 (SD 11.5)]. Patients who received greater amount of SS had optimal mental health. Being female, unmarried, lower education attainment, having more comorbid conditions, being diagnosed with type 2 diabetes and having been diagnosed of diabetes for a longer duration were associated with poorer mental health. It is important to develop context-specific interventions to improve diabetic patients’ mental health

A family history of type 2 diabetes increases risk factors associated with overfeeding

Aims/hypothesis: The purpose of the study was to test prospectively whether healthy individuals with a family history of type 2 diabetes are more susceptible to adverse metabolic effects during experimental overfeeding. Methods: We studied the effects of 3 and 28 days of overfeeding by 5,200 kJ/day in 41 sedentary individuals with and without a family history of type 2 diabetes (FH+ and FH− respectively). Measures included body weight, fat distribution (computed tomography) and insulin sensitivity (hyperinsulinaemic–euglycaemic clamp). Results: Body weight was increased compared with baseline at 3 and 28 days in both groups (p<0.001), FH+ individuals having gained significantly more weight than FH− individuals at 28 days (3.4±1.6 vs 2.2±1.4 kg, p<0.05). Fasting serum insulin and C-peptide were increased at 3 and 28 days compared with baseline in both groups, with greater increases in FH+ than in FH− for insulin at +3 and +28 days (p<0.01) and C-peptide at +28 days (p<0.05). Fasting glucose also increased at both time points, but without a significant group effect (p=0.1). Peripheral insulin sensitivity decreased in the whole cohort at +28 days (54.8±17.7 to 50.3±15.6 μmol min−1 [kg fat-free mass]−1, p=0.03), and insulin sensitivity by HOMA-IR decreased at both time points (p<0.001) and to a greater extent in FH+ than in FH− (p=0.008). Liver fat, subcutaneous and visceral fat increased similarly in the two groups (p<0.001). Conclusions: Overfeeding induced weight and fat gain, insulin resistance and hepatic fat deposition in healthy individuals. However, individuals with a family history of type 2 diabetes gained more weight and greater insulin resistance by HOMA-IR. The results of this study suggest that healthy individuals with a family history of type 2 diabetes are predisposed to adverse effects of overfeeding.D. Samocha-Bonet, L.V. Campbell, A. Viardot, J. Freund, C.S. Tam, J.R. Greenfield and L.K. Heilbron