Nanoindentation study of polydimethylsiloxane elastic modulus using Berkovich and flat punch tips

This article explores polydimethylsiloxane (PDMS) mechanical properties, and presents nanoindentation experiments with Berkovich and flat punch indenters. In the Berkovich tip quasi‐static nanoindentation test, there are pull‐in and pull‐off events observed during the initial tip contact, and when withdrawing from the surface, respectively. The pull‐in interaction needs to be accounted for to properly determine the initial contact point, and thus the accurate contact area. Once accounted for the pull‐in event, the Berkovich and flat punch tips quasi‐static nanoindentation tests give comparable results of about 1.5 MPa for the PDMS elastic modulus (5 : 1 elastomer base to the curing agent ratio). However, PDMS unloading stiffness is higher than the loading stiffness, and dynamic PDMS testing yields higher elastic modulus of about 3.6 MPa. While these results are comparable with the large strain macroscopic compression test results, the difference underscores the complexity of elastomer mechanical characterization and illustrates the discrepancies typical of the reported values. This article describes nanoindentation methods and critical aspects of interpreting results to assess PDMS mechanical properties. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41384.     

Identification of a reservoir for HIV-1 in patients on highly active antiretroviral therapy

The hypothesis that quiescent CD4+ T lymphocytes carrying proviral DNA provide a reservoir for human immunodeficiency virus-type 1 (HIV-1) in patients on highly active antiretroviral therapy (HAART) was examined. In a study of 22 patients successfully treated with HAART for up to 30 months, replication-competent virus was routinely recovered from resting CD4+ T lymphocytes. The frequency of resting CD4+ T cells harboring latent HIV-1 was low, 0.2 to 16.4 per 10(6) cells, and, in cross-sectional analysis, did not decrease with increasing time on therapy. The recovered viruses generally did not show mutations associated with resistance to the relevant antiretroviral drugs. This reservoir of nonevolving latent virus in resting CD4+ T cells should be considered in deciding whether to terminate treatment in patients who respond to HAART.     

Oropharyngeal candidiasis in patients with AIDS: randomized comparison of fluconazole versus nystatin oral suspensions

A total of 167 human immunodeficiency virus (HIV)-infected patients with oropharyngeal candidiasis were randomly assigned to receive 14 days of therapy with liquid suspension fluconazole (100 mg once daily) or liquid nystatin (500,000 U four times daily). At day 14, 87% of the fluconazole-treated patients were clinically cured, as opposed to 52% in the nystatin-treated group (P < .001). Fluconazole eradicated Candida organisms from the oral flora in 60%, vs. a 6% eradication rate with nystatin (P < .001). The fluconazole group had fewer relapses noted on day 28 (18%, vs. 44% in the nystatin group; P < .001). This relapse difference no longer existed by day 42. Fluconazole oral suspension as a systemic therapy was more effective than liquid nystatin as a topical therapy in the treatment of oral candidiasis in HIV-infected patients and provided a longer disease-free interval before relapse.     

Neural activity in areas V1, V2 and V4 during free viewing of natural scenes compared to controlled viewing

BACKGROUND AND PURPOSE: The three-dimensional (3D) dose distribution in combination with 3D anatomy of 13 patients treated for cervical carcinoma with intracavitary brachytherapy was analyzed. The aim of this study was to determine the correlation between a dose value obtained from the integral dose volume histogram (DVH) of the rectum and (a) the Nederlands Kanker Instituut (NKI) point of reference for the rectum dose (R) and (b) the highest dose to the frontal rectum wall in the transverse CT slice near the top of the vagina through point R. RESULTS: The correlation between the DVH rectum dose value for 2 cm3 in the highest dose region and the rectum dose at point R was poor (regression coefficient 0.50). On the contrary, however, the correlation between the DVH rectum dose value for 2 cm3 in the highest dose region and the maximum rectum dose value in a transverse CT slice through point R was good (regression coefficient 0.90). CONCLUSIONS: The maximal rectum dose value obtained from a transverse CT slice near the top of the vagina through point R was found to be a more representative point for the rectal dose burden and might therefore show a good correlation with complications. The point of reference for the rectal dose (R) was found not to be a reliable estimation of the maximal dose in the rectum.     

Supreme Court decision making: Cognitive style as a predictor of ideological consistency of voting.

An integrative complexity coding system was used to explore the relations between cognitive style and political ideology among US Supreme Court justices who served on the Court between 1964 and 1978. The integrative complexity of case opinions that Ss authored during their 1st terms on the Court and the overall liberalism–conservatism of their voting records throughout their tenure were assessed. Consistent with past work on cognitive style and political ideology, Ss with liberal and moderate voting records exhibited more integratively complex styles of thought in their early case opinions than did those with conservative voting records. Unexpectedly, these relationships between cognitive style and ideology were more powerful on cases involving economic conflicts of interest than on cases involving civil liberties and rights issues. Results remain significant after controlling for a variety of demographic and background characteristics of the Ss (e.g., age, religion, quality of law school attended) and characteristics of the judicial opinions scored for integrative complexity (unanimous or split-Court, majority–minority status of opinion). Possible explanations for the results and processes that limit the cross-issue generality of relationships between cognitive style and ideology are discussed. (60 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

On a premenstrual psychiatric diagnosis: What's in a name?

A new diagnosis has been approved for inclusion in a special appendix of the revised catalog of psychiatric disorders, the Diagnostic and Statistical Manual of Mental Disorders (3rd ed.). This diagnosis, "Late Luteal Phase Dysphoric Disorder," is gender specific, insofar as only women have the potential for menstrual cycles. Because it pertains to only one gender, this diagnosis should be carefully scrutinized for potential bias. To aid in evaluating the diagnosis, we critically examine research on premenstrual symptoms, the rationale and supporting evidence for the diagnosis, and its potential scientific, clinical, and social ramifications. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Corrosion inhibition of Al–B4C metal matrix composites in a NaCl solution by benzotriazole

Benzotriazole (BTAH) was used for the first time to inhibit the corrosion of Al–B₄C composites in a NaCl solution. Its corrosion inhibition effect was systematically investigated as a function of BTAH concentrations, volume fractions of B₄C particles and immersion time by using potentiodynamic polarization, electrochemical impedance and infrared reflection adsorption spectroscopy techniques. It was found that BTAH is a good corrosion inhibitor for the Al–B₄C MMCs in a 3.5 g L⁻¹ NaCl solution, and its inhibition efficiency increased with increasing BTAH concentration. For the same BTAH concentration and immersion time, higher B₄C volume fraction leads to higher corrosion inhibition efficiency. The inhibition efficiency of benzotriazole was also influenced by the immersion time: the inhibition efficiency increases with the immersion time in the first 18 h. However, prolonging the immersion time leads to a decrease in the inhibition efficiency. As the BTAH was an inhibitor with a cathodic character and it inhibited corrosion by physically adsorbing on B₄C particles at the composite surface, it obeyed the Freundlich adsorption isotherm.     

Chemical nature of superhydrophobic aluminum alloy surfaces produced via a one-step process using fluoroalkyl-silane in a base medium

Various surface characterization techniques were used to study the modified surface chemistry of superhydrophobic aluminum alloy surfaces prepared by immersing the substrates in an aqueous solution containing sodium hydroxide and fluoroalkyl-silane (FAS-17) molecules. The creation of a rough micronanostructure on the treated surfaces was revealed by scanning electron microscopy (SEM). X-ray photoelectron spectroscopy (XPS) and infrared reflection absorption spectroscopy (IRRAS) confirmed the presence of low surface energy functional groups of fluorinated carbon on the superhydrophobic surfaces. IRRAS also revealed the presence of a large number of OH groups on the hydrophilic surfaces. A possible bonding mechanism of the FAS-17 molecules with the aluminum alloy surfaces has been suggested based on the IRRAS and XPS studies. The resulting surfaces demonstrated water contact angles as high as ~166° and contact angle hystereses as low as ~4.5°. A correlation between the contact angle, rms roughnesses, and the chemical nature of the surface has been elucidated.