CHARACTERIZATION OF THE SURFACE PROPERTIES OF TWO PRESSURE SENSITIVE ADHESIVES

Pressure sensitive adhesive (PSAs) are ubiquitous polymers employed as adhesives tapes and sticky notes. PSAs adhere on a substrate after the application of a light pressure and are widely used in many industries such as electronic, medical, or consumer products. In some situations, it is necessary for the PSA make or maintain a bond in a in a humid environment or even underwater. Similarly, PSAs need to adhere to a broad range of surfaces, including skin which can be very compliant. The objective of this work is to understand how the surface and rheological properties of two PSAs are affected by exposure to water as well as to develop model soft substrate to study the effect of substrate compliance on adhesion. In Chapter 1 the characterization of two PSAs: poly(2-Ethylhexyl acrylate) and poly(2-Ethylhexyl acrylate-co-AA), is presented. The two PSAs are almost identical, except that one of the two contains 5 wt% of acrylic acid as a comonomer. The objective of the work is to understand how the presence of 5 wt% of AA affects the properties of the PSA. We characterize the underwater surface properties of the two PSAs using the contact angle measurements to determine the surface energy and surface pKa. The surface zeta potential to determine the effect of the solution pH on the charge. We then use these measurements to interpret separate probe-tack adhesion measurements. Our measurements show that the acrylic acid comonomer significantly affects the properties of the PSAs, especially under wet condition where it deprotonates. In chapter 2, we reports on the synthesis and characterization of the surface and bulk properties of poly(dimethyl siloxane) (PDMS) with different degree of crosslinking. The objective of the work is to study adhesion of PSAs on compliant substrates. To do so, we selected PDMS as a model compliant substrate and report on the change in surface and mechanical properties of PDMS for different degree of crosslinking. Our measurements show a direct relationship between the concentration of crosslinking agent and the elastic modulus (as measured by shear rheology). We also characterized the surface properties of PDMS after an oxygen plasma treatment. We show that stable contact angle measurements are obtained after extraction of unreacted oligomers

The large area detector onboard the eXTP mission

The Large Area Detector (LAD) is the high-throughput, spectral-timing instrument onboard the eXTP mission, a flagship mission of the Chinese Academy of Sciences and the China National Space Administration, with a large European participation coordinated by Italy and Spain. The eXTP mission is currently performing its phase B study, with a target launch at the end-2027. The eXTP scientific payload includes four instruments (SFA, PFA, LAD and WFM) offering unprecedented simultaneous wide-band X-ray timing and polarimetry sensitivity. The LAD instrument is based on the design originally proposed for the LOFT mission. It envisages a deployed 3.2 m2 effective area in the 2-30 keV energy range, achieved through the technology of the large-area Silicon Drift Detectors - offering a spectral resolution of up to 200 eV FWHM at 6 keV - and of capillary plate collimators - limiting the field of view to about 1 degree. In this paper we will provide an overview of the LAD instrument design, its current status of development and anticipated performance

High-pressure synthesis and thermal expansivity investigation of carbonate solid solutions Mg1-xMnxCO3

Using synthesized MgCO3 and reagent-grade MnCO3 as starting materials, a series of Mg1-xMnxCO3 carbonate solid solutions were synthesized by a simple solid reaction under high-temperature-pressure conditions of 3 GPa and 800 degrees C for 4 h. The phase compositions of as-synthesized Mg1-xMnxCO3 samples were investigated by powder X-ray diffraction (XRD); no impurities were observed. The lattice parameters were refined and showed a linear relationship as a function of the Mn2+ content, which is expected to be in accordance with the ideal solution model. Based on this, high-temperature XRD measurements were carried out to further study the thermal expansivity of Mg1-xMnxCO3. The axis thermal expansion coefficients (alpha(a) and alpha(c)) and the volumetric thermal expansion coefficient alpha(V) for Mg1-xMnxCO3 were quantified as alpha(a) = 7.41 x 10(-6)/degrees C, alpha(c) = 2.37 x 10(-5)/degrees C and alpha(V) = 3.86 x 10(-5)/degrees C for x = 0.0; alpha(a) = 6.67 x 10(-6)/degrees C, alpha(c) = 2.31 x 10(-5)/degrees C and alpha(V) = 3.67 x 10(-5)/degrees C for x = 0.1; alpha(a) = 6.16 x 10(-6)/degrees C, alpha(c) = 2.35 x 10(-5)/degrees C and alpha(V) = 3.59 x 10(-5)/degrees C for x = 0.3; alpha(a) = 5.91 x 10(-6)/degrees C, alpha(c) = 2.40 x 10(-5)/degrees C and alpha(V) = 3.58 x 10(-5)/degrees C for x = 0.5; alpha(a) = 5.47 x 10(-6)/degrees C, alpha(c) = 2.53 x 10(-5)/degrees C and alpha(V) = 3.61 x 10(-5)/degrees C for x = 0.7; alpha(a) = 4.76 x 10(-6)/degrees C, alpha(c)= 2.55 x 10(-5)/degrees C and alpha(V) = 3.52 x 10(-5)/degrees C for x = 0.9; alpha(a) = 4.18 x 10(-6)/degrees C, alpha(c) = 2.50 x 10(-5)/degrees C and alpha(V) = 3.35 x 10(-5)/degrees C for x = 1.0. The thermal expansion coefficients (alpha(a), alpha(c), and alpha(V)) can be fitted with a symmetric cubic function of the Mn2+ content as alpha(a) = 7.34 x 10(-6)-7.06 x 10(-6)x + 1.21 x 10(-5)x(2)-8.19 x 10(-6)x(3); alpha(c) = 2.37 x 10(-6)-7.94 x 10(-6)x + 2.57 x 10(-5)x(2) - 1.64 x 10(-5)x(3); alpha(V) = 3.85 x 10(-5) - 2.08 x 10(-5)x + 4.59 x 10(-5)x(2) - 3.01 x 10(-5)x(3)

Transcriptome Analysis of the SL221 Cells at the Early Stage during Spodoptera litura Nucleopolyhedrovirus Infection.

Spodoptera litura (S. litura) is one of the most destructive agricultural pests worldwide. There is urgent need for a nuclear polyhedrosis virus that is specific to S. litura. To date, there have been no reports regarding the responses of S. litura cells to early Spodoptera litura nucleopolyhedrovirus (SpltNPV) infection due to the lack of a reference genome and transcriptome for S. litura. In this study, a cell transcriptome from the host S. litura was assembled and used for Illumina strand-specific RNA sequencing (RNA-seq) to generate 99180 unigenes, representing the 18 hour infection cycle. More than 2000 S. litura genes were significant differentially regulated throughout the infection. The levels of viral mRNAs began to increase dramatically at 6 hpi, and this increase continued throughout the remainder of the infection. We focused on the expression of genes related to stress responses, apoptosis, metabolic enzymes and host cell innate immune system. A small subset of genes related to host stress response, especially for 62 ones being able to annotated as enzyme, ligand and receptor genes, were observed to be specifically differentially expressed at 6 hpi. At 18 hpi, 104 unigenes were continuously significantly changing from 0 hpi to 18 hpi, considered to be viral multiplication related genes, including 3 annotated SL221 unigenes and 81 viral genes, such as tetraspanin and iap gene. This information and further studies on the regulation of host gene expression by baculovirus infection at early stage will provide the tools needed to enhance the utility of this virus as an effective insecticide

Decomposition of an odorant in olfactory perception and neural representation

Molecules-the elementary units of substances-are commonly considered the units of processing in olfactory perception, giving rise to undifferentiated odour objects invariant to environmental variations. By selectively perturbing the processing of chemical substructures with adaptation (&#39;the psychologist&#39;s microelectrode&#39;) in a series of psychophysical and neuroimaging experiments (458 participants), we show that two perceptually distinct odorants sharing part of their structural features become significantly less discernible following adaptation to a third odorant containing their non-shared structural features, in manners independent of olfactory intensity, valence, quality or general olfactory adaptation. The effect is accompanied by reorganizations of ensemble activity patterns in the posterior piriform cortex that parallel subjective odour quality changes, in addition to substructure-based neural adaptations in the anterior piriform cortex and amygdala. Central representations of odour quality and the perceptual outcome thus embed submolecular structural information and are malleable by recent olfactory encounters. This study demonstrates the decomposition of an odour compound in olfactory perception and central neural representation and establishes a direct correspondence between the coding of submolecular chemical features and odour quality.</p

Gene ontology (GO) term distribution.

<p>A total of 17,196 unigenes were classified by WEGO software to perform the GO functional classification.</p

COG annotations of SL221 unigenes.

<p>COG annotations of SL221 unigenes.</p

GO analysis of differentially expressed unigenes among different biological processes.

<p>GO analysis of differentially expressed SL221 transcripts was performed, and distributions of differentially expressed unigenes at 6 hpi (upper panel), 12 hpi (middle panel) and 18 hpi (lower panel) are shown. Blue represents biological process, Red represents cellular component and yellow represents molecular function.</p

Volcano plots of up/downregulated and non-differentially expressed SL221 unigenes and viral genes throughout infection.

<p>A: Unigene expression levels between cells at 6/12/18 hpi and mock (horizontal axis), and unigene expression levels between adjacent infection time points (vertical axis). DEG: differentially expressed genes. B: Venn diagrams showing the protein overlap in biological replicates of cells at mock, 6 hpi and 12 hpi. C: Venn diagrams showing the protein overlap in biological replicates of cells at mock, 12 hpi and 18 hpi.</p

Validation of the RNA-seq results by quantitative real-time PCR (qRT-PCR).

<p>Two viral unigenes (GP41 and IAP) and 2 host cell unigenes (CYP450 and HSP70) with different fold changes were randomly selected for analysis using qRT-PCR, GAPDH was used for normalization.</p