Effect of Condensed Water at an Alumina/Epoxy Resin Interface on Curing Reaction.

The adhesion of epoxy adhesives to aluminum materials is an important issue in assembling parts for lightweight mobility. Aluminum surfaces typically possess an oxide layer, which readily adsorbs water. In this study, the aggregation states of water and its effect on the curing reaction were examined by placing a water layer between an amorphous alumina surface and a mixture of epoxy and amine components. This study used molecular dynamics simulations and density functional theory calculations. Before the reaction, water molecules strongly adsorbed onto the alumina surface, aggregating excess water. Some water diffused into the epoxy/amine mixture, accelerating the diffusion of unreacted substances. This led to faster reaction kinetics, particularly in proximity to the alumina surface. The adsorption of water molecules onto the alumina surface and the aggregation of excess water were similarly observed even after the curing process. Subsequently, the interaction between the alumina surface and various functional groups of the epoxy/amine mixture was evaluated before and after the reaction. Epoxy monomers had little interaction with the alumina surface before the reaction, whereas hydroxy groups formed by the ring-opening reaction of epoxy groups exhibited notable interaction. Conversely, sulfonyl and amino groups in amine compounds formed hydrogen bonds with OH groups on the alumina surface before the reaction. However, after the reaction, amino groups weakened their interaction with the alumina OH groups as they transformed from primary to tertiary during the curing reaction. Both epoxy and amine monomers/fragments similarly interacted with water molecules, both before and after the reaction. The insights gained from this study are expected to contribute to a better understanding of the impact of moisture absorption on the application of epoxy resins.

Electronic Interaction of Epoxy Resin with Copper at the Adhered Interface.

A better understanding of the aggregation states of adhesive molecules in the interfacial region with an adherend is crucial for controlling the adhesion strength and is of great inherent academic interest. The adhesion mechanism has been described through four theories: adsorption, mechanical, diffusion, and electronic. While interfacial characterization techniques have been developed to validate the aforementioned theories, that related to the electronic theory has not yet been thoroughly studied. We here directly detected the electronic interaction between a commonly used thermosetting adhesive, cured epoxy of diglycidyl ether of bisphenol A (DGEBA) and 4,4'-diaminodiphenylmethane (DDM), and copper (Cu). This study used a combination of density functional theory (DFT) calculations and femtosecond transient absorption spectroscopic (TAS) measurements as this epoxy adhesive-Cu pairing is extensively used in electronic device packaging. The DFT calculations predicted that π electrons in a DDM molecule adsorbed onto the Cu surface flowed out onto the Cu surface, resulting in a positive charge on the DDM. TAS measurements for the Cu/epoxy multilayer film, a model sample containing many metal/adhesive interfaces, revealed that the electronic states of excited DDM moieties at the Cu interface were different from those in the bulk region. These results were in good accordance with the prediction by DFT calculations. Thus, it can be concluded that TAS is applicable to characterize the electronic interaction of adhesives with metal adherends in a nondestructive manner.

Absolute local conformation of poly(methyl methacrylate) chains adsorbed on a quartz surface.

Polymer chains at a buried interface with an inorganic solid play a critical role in the performance of polymer nanocomposites and adhesives. Sum frequency generation (SFG) vibrational spectroscopy with a sub-nanometer depth resolution provides valuable information regarding the orientation angle of functional groups at interfaces. However, in the case of conventional SFG, since the signal intensity is proportional to the square of the second-order nonlinear optical susceptibility and thereby loses phase information, it cannot be unambiguously determined whether the functional groups face upward or downward. This problem can be solved by phase-sensitive SFG (ps-SFG). We here applied ps-SFG to poly(methyl methacrylate) (PMMA) chains in direct contact with a quartz surface, shedding light on the local conformation of chains adsorbed onto the solid surface. The measurements made it possible to determine the absolute orientation of the ester methyl groups of PMMA, which were oriented toward the quartz interface. Combining ps-SFG with all-atomistic molecular dynamics simulation, the distribution of the local conformation and the driving force are also discussed.

Associations of the timing of sleep and meals with the presence of gastroesophageal reflux disease in community-dwelling women in Japan.

BACKGROUND: It has been suspected that circadian rhythms may play a part in the pathogenesis of gastrointestinal diseases including gastroesophageal reflux disease (GERD). The present study aimed to examine the cross-sectional association of the timing of sleep and meals with the presence of GERD in community-dwelling women in Japan. METHODS: In total, 605 women responded to a self-administered questionnaire asking for information on GERD symptoms, sleep habits, sleep disturbances and the timing of meals. GERD symptoms were evaluated using the Frequency Scale for the Symptoms of GERD, and participants with a score of more than seven points were classified as having GERD. RESULTS: In total, 104 (17.2%) women were found to have GERD. Later bedtime on both weekdays and weekends and later midpoint of sleep were significantly associated with the odds ratios (OR) of GERD after controlling for covariates: ORs for each 1 h delay were 1.31 (95% confidence interval [CI] = 1.03-1.68), 1.38 (95% CI = 1.08-1.75) and 1.43 (95% CI = 1.06-1.95). Having lunch at irregular times was significantly associated with the increased OR of GERD (1.99; 95% CI = 1.02-3.91). Longer overnight fasting duration and longer time intervals from the midpoint of sleep to breakfast and lunch were significantly associated with decreased OR of GERD (ORs for each 1 h increase were 0.73 [95% CI = 0.56-0.95], 0.64 [95% CI = 0.46-0.88] and 0.70 [95% CI = 0.51-0.96]). CONCLUSIONS: These data suggest that the timing of sleep and timing of meals relative to the sleep/wake cycle are associated with the presence of GERD.

Theoretical Study on the Contribution of Interfacial Functional Groups to the Adhesive Interaction between Epoxy Resins and Aluminum Surfaces.

To ensure the quality and reliability of products bonded by epoxy resin adhesives, elucidation of the microscopic adhesion mechanism is essential. The adhesive interaction and bonding strength between epoxy resins and hydroxylated γ-alumina (001) surfaces were investigated by using a combined molecular dynamics (MD) and density functional theory (DFT) study. The curing reaction of an epoxy resin consisting of diglycidyl ether of bisphenol A (DGEBA) and 4,4'-diaminodiphenyl sulfone (DDS) was simulated. The resin structure was divided into fragmentary structures to study the interaction of each functional group with the alumina surface using DFT calculations. From the characteristics of the adhesive structures and the calculated adhesion energies, it was found that the fragments forming hydrogen bonds with hydroxy groups on the alumina surface resulted in large adhesion energies. On the other hand, the fragments adsorbed on the alumina surface via dispersion interactions resulted in small adhesion energies. The adhesion forces evaluated from the Hellmann-Feynman force calculations indicated the significant contribution of the hydroxy groups and benzene ether moieties derived from DGEBA to the adhesive stress of the DGEBA/DDS epoxy resin. The direction of hydrogen bonding between the epoxy resin and the surface and the difference in geometry at the interface between the donor and acceptor of hydrogen bonding played a central role in maintaining the adhesive strength during the failure process of the adhesive interface.

Spatial Distribution of the Network Structure in Epoxy Resin via the MAXS-CT Method.

We have succeeded in visualizing the spatial heterogeneity of the reaction ratio in epoxy resins by combining medium-angle X-ray scattering (MAXS) and computed tomography (CT). The reaction ratio is proportional to the degree of cross-linking between epoxy and amine in epoxy resins. The reaction ratio and its spatial inhomogeneity affect the toughness of epoxy resins. However, there has been no non-destructive method to measure the spatial inhomogeneity of the reaction ratio, although we can measure only the spatially averaged reaction ratio by Fourier-transform infrared spectroscopy (FT-IR). We found that the scattering peak reflected the cross-linking structures in the q region of MAXS and that the peak intensity is proportional to the reaction ratio. By reconstructing CT images from this peak intensity, we visualized the spatial heterogeneity of the reaction ratio. The application of this method may not be limited to epoxy resins but may extend to studying the heterogeneity of cross-linked structures in other materials.

Change in local conformation of polymer chains at film surface attached to solid surface.

Adhesion is a molecular event where polymer chains contact with a material surface to form an interfacial layer. To obtain a better understanding of the adhesion on a molecular scale, we herein examined the conformational change of polystyrene (PS) chains at the film surface after contacting with hydrophobic or hydrophilic surfaces using sum-frequency generation (SFG) spectroscopy. Chains altered their local conformations with a quartz surface more quickly than a hydrophobic alkyl-functionalized one. A full-atomistic molecular dynamics simulation showed that these results, which were coupled with the contact process of PS chains with the solid surface, could be explained in terms of the Coulomb interaction between them.

In situ transmission electron microscopy observation of the deformation and fracture processes of an epoxy/silica nanocomposite.

Herein, we report the in situ transmission electron microscopy observation of the deformation and fracture processes of an epoxy resin thin film containing silica nanoparticles under tensile strain. Under tensile strain, the dispersed silica nanoparticles in the composite arrest the progress of the crack tip and prevent crack propagation. Concomitantly, the generation and growth of nanovoids at the epoxy matrix/nanoparticle interfaces were clearly observed, particularly in the region near the crack tip. These nanovoids contribute to the dissipation of fracture energy, thereby enhancing the fracture toughness. We also analyzed the local distributions of the true strain and strain rate in the nanocomposite film during tensile testing using the digital image correlation method. In the region around the crack tip, the strain rate increased by 3 to 10 times compared to the average of the entire test specimen. However, the presence of large filler particles in the growing crack suppressed the generation of strain, potentially contributing to hindering crack growth.

Kinetics of the interfacial curing reaction for an epoxy-amine mixture.

A better understanding of the chemical reaction between epoxy and amine compounds at a solid interface is crucial for the design and fabrication of materials with appropriate adhesive strength. Here, we examined the curing reaction kinetics of epoxy phenol novolac and 4,4'-diaminodiphenyl sulfone at the outermost interface using sum-frequency generation spectroscopy, and X-ray and neutron reflectivity in conjunction with a full atomistic molecular dynamics simulation. The reaction rate constant was much larger at the quartz interface than in the bulk. While the apparent activation energy at the quartz interface obtained from an Arrhenius plot was almost identical to the bulk value, the frequency factor at the quartz interface was greater than that in the bulk. These results could be explained in terms of the densification and orientation of reactants at the interface, facilitating the encounter of the reactants present.

Mechanism of crescent-shaped and ring-shaped epidermal damage from laser hair removal with cryogen spray cooling.

The safety and efficacy of laser hair removal have been well established through many clinical studies and through clinical use over the past 25 years. A laser hair removal device that protects the epidermis by utilizing cryogen spray cooling (CSC) is widely used internationally. In darker skin types, post-inflammatory hyperpigmentation (PIH) can occur after laser hair removal. In particular, laser hair removal with CSC is known to cause crescent-shaped or ring-shaped PIH. In this experiment, we report a visualization of this PIH mechanism. The laser used in this experiment is a 755-nm-long-pulsed alexandrite laser. Graph paper was treated with this laser to assess for thermal damage. We investigated changes in thermal damage due to differences in laser spot size, fluence output, and laser beam angle in relation to the graph paper. When using a spot size of 18 mm, we observed that higher fluences caused crescent-shaped thermal damage on the margins of the treated graph paper. It was also confirmed that when the hand piece is not held perpendicular to the skin, the laser-treated area is expanded and the CSC range is narrowed. These factors caused the area of thermal damage to widen. This widening causes ring-shaped thermal injury, leading to PIH. We treated graph paper using a hair removal laser with CSC to investigate the mechanism of crescent or ring-shaped thermal damage. Laser treatment on graph paper is effective as a test for defects in the CSC device. Factors that cause inadequate cooling, which leads to PIH, are large spot size, high fluence, not holding the laser hand piece perpendicular to the skin, and malfunctioning of CSC device.

Entropy-driven segregation in epoxy-amine systems at a copper interface.

The composition of an epoxy resin at the interface with the adherend is usually different from that in the bulk due to the enrichment of a specific constituent, a characteristic called interfacial segregation. For better adhesion, it should be precisely understood how epoxy and amine molecules exist on the adherend surface and react with each other to form a three-dimensional network. In this study, the entropic factor of the segregation in a mixture of epoxy and amine at the copper interface before and after the curing reaction is discussed on the basis of a full-atomistic molecular dynamics (MD) simulation. Smaller molecules were preferentially segregated at the interface regardless of the epoxy and amine, and this segregation remained after the curing process. No segregation occurred at the interface for a combination composed of epoxy and amine molecules with a similar size. These findings make it clear that the size disparity between constituents affects the interfacial segregation via the packing and/or translational entropy. The curing reaction was slower near the interface than in the bulk, and a large amount of unreacted molecules remained there. Finally, the effect of molecular shape was also examined. Linear molecules were more likely to segregate than round-shaped ones even though they were similar in volume. We believe that these findings, which are difficult to obtain experimentally, contribute to the understanding of the interfacial adhesion phenomena on a molecular scale.

Dynamic behaviour of water molecules in heterogeneous free space formed in an epoxy resin.

Although an epoxy resin is a stable material, it absorbs moisture over a long period of time, causing deterioration of its material properties. We here applied a full-atomistic molecular dynamics (MD) simulation to study where water molecules exist in an epoxy resin and how they dynamically behave. First, the curing reaction was simulated to obtain a network structure so that the time course of the density, and thereby the free space, in the resin were obtained. The results made it possible to discuss the formation and size distribution of the free spaces which were not connected to each other. Then, a few percent of water were inserted into the free space of the cured epoxy resin to examine the location and dynamics of their molecules. We found that several water molecules were clustered at a preferred site, where hydrogen bonds can be formed with hydroxy, ether and amino groups of the network, in the free space, and they heterogeneously moved from there to other sites.

Local orientation of chains at crystal/amorphous interfaces buried in isotactic polypropylene thin films.

A better understanding of the aggregation states of polymer chains in thin films is of pivotal importance for developing thin film polymer devices in addition to its inherent scientific interest. Here we report the preferential orientation of the crystalline lamellae for isotactic polypropylene (iPP) in spin-coated films by grazing incidence of wide-angle X-ray diffraction in conjunction with sum frequency generation vibrational spectroscopy, which provides information on the local conformation of chains at crystal/amorphous interfaces buried in a thin film. The crystalline orientation of iPP, which formed cross-hatched lamellae induced by lamellar branching, altered from a mixture of edge-on and face-on mother lamellae to preferential face-on mother lamellae with decreasing thickness. The orientation of methyl groups at the crystal/amorphous interfaces in the interior region of the iPP films changed, accompanied by a change in the lamellar orientation.

[Sleeve Lobectomy for Right Middle Lobe and S6 Segment Lung Cancer:Report of a Case].

A 76-year-old man showed an abnormal chest shadow at the follow-up of treated gastric cancer. Chest computed tomography revealed mass lesions in the right middle and left upper lobes, and bronchoscopy revealed a nodular lesion at the entrance of the right B6. The right middle lobe and B6 lesions were diagnosed as lung cancer, and sleeve resection for the right middle lobe and S6 segment was performed. On postoperative day 98, partial resection of the left lung lesion was performed, and the pathological diagnosis was also lung cancer.

Effect of a heterogeneous network on glass transition dynamics and solvent crack behavior of epoxy resins.

In general, it has been widely accepted that the physical properties of an epoxy resin are strongly dependent on how it is prepared. However, a clear understanding of the mechanisms of the relationship at a molecular level has yet to be achieved. We here studied the glass transition dynamics and fracture behavior of four epoxy resins, which were pre-cured at different temperatures and well cured under the same conditions. Fourier-transform infrared spectroscopy revealed that the reaction kinetics for an epoxy-amine mixture were strongly dependent on the pre-curing temperature. The glass transition temperature of epoxy resins with the same cross-linking density was dependent on the pre-curing temperature. Dielectric relaxation spectroscopy and dynamic mechanical analysis revealed that the fragility index of the epoxy resin decreased with increasing pre-curing temperature, indicating that the network structure formed in it became more heterogeneous with increasing pre-curing temperature. Once the epoxy resin was immersed in a good solvent, it was partly swollen and was then macroscopically fractured. The fracture was initiated by the crack generation in an un-swollen region of the resin due to the stress induced upon swelling. The immersion time required to reach the fracture decreased as the extent of the heterogeneity increased. The knowledge here obtained should be useful for understanding and controlling fracture toughness of epoxy resins, leading to the furtherance of their functionalization.

Quantum Chemistry on Quantum Computers: A Polynomial-Time Quantum Algorithm for Constructing the Wave Functions of Open-Shell Molecules.

Quantum computers are capable to efficiently perform full configuration interaction (FCI) calculations of atoms and molecules by using the quantum phase estimation (QPE) algorithm. Because the success probability of the QPE depends on the overlap between approximate and exact wave functions, efficient methods to prepare accurate initial guess wave functions enough to have sufficiently large overlap with the exact ones are highly desired. Here, we propose a quantum algorithm to construct the wave function consisting of one configuration state function, which is suitable for the initial guess wave function in QPE-based FCI calculations of open-shell molecules, based on the addition theorem of angular momentum. The proposed quantum algorithm enables us to prepare the wave function consisting of an exponential number of Slater determinants only by a polynomial number of quantum operations.

Adiabatic quantum computing with spin qubits hosted by molecules.

A molecular spin quantum computer (MSQC) requires electron spin qubits, which pulse-based electron spin/magnetic resonance (ESR/MR) techniques can afford to manipulate for implementing quantum gate operations in open shell molecular entities. Importantly, nuclear spins, which are topologically connected, particularly in organic molecular spin systems, are client qubits, while electron spins play a role of bus qubits. Here, we introduce the implementation for an adiabatic quantum algorithm, suggesting the possible utilization of molecular spins with optimized spin structures for MSQCs. We exemplify the utilization of an adiabatic factorization problem of 21, compared with the corresponding nuclear magnetic resonance (NMR) case. Two molecular spins are selected: one is a molecular spin composed of three exchange-coupled electrons as electron-only qubits and the other an electron-bus qubit with two client nuclear spin qubits. Their electronic spin structures are well characterized in terms of the quantum mechanical behaviour in the spin Hamiltonian. The implementation of adiabatic quantum computing/computation (AQC) has, for the first time, been achieved by establishing ESR/MR pulse sequences for effective spin Hamiltonians in a fully controlled manner of spin manipulation. The conquered pulse sequences have been compared with the NMR experiments and shown much faster CPU times corresponding to the interaction strength between the spins. Significant differences are shown in rotational operations and pulse intervals for ESR/MR operations. As a result, we suggest the advantages and possible utilization of the time-evolution based AQC approach for molecular spin quantum computers and molecular spin quantum simulators underlain by sophisticated ESR/MR pulsed spin technology.

Exploring the Impact of Molecular Structure on Curing Kinetics: A Comparative Study of Diglycidyl Ether of Bisphenol A and F Epoxy Resins.

Epoxy resins are essential for various applications, and their properties depend on the curing reactions during which epoxy and amine compounds form the network structure. We here focus on how the presence or absence of two methyl groups in common epoxy bases, diglycidyl ether of bisphenol A and F (4,4'-DGEBA and 4,4'-DGEBF), affects the curing kinetics. The chemical reactions of both 4,4'-DGEBA and 4,4'-DGEBF, when cured with the same amine, were monitored by Fourier-transform infrared (FT-IR) spectroscopy and differential scanning calorimetry (DSC). Despite no difference in the reactivity of epoxy groups between 4,4'-DGEBA and 4,4'-DGEBF, the initial curing reaction was slower for the latter. This delay for the 4,4'-DGEBF system was attributed to intermolecular stacking, which hindered the approach of unreacted epoxy groups to amino groups and vice versa. This conclusion was drawn from the results obtained through ultraviolet (UV) spectroscopy, wide-angle X-ray scattering (WAXS), density functional theory (DFT) calculation, and all-atom molecular dynamics (MD) simulation.

Cadmium exposure and the risk of breast cancer in Japanese women.

Non-occupational exposure to cadmium has been suspected to be a risk factor for breast cancer. The present study examined the association between urinary cadmium level and the risk of breast cancer in a case-control study among Japanese women. Cases were 153 women newly diagnosed and histologically confirmed with breast cancer at a general hospital in Gifu, Japan. A total of 431 controls individually matched to cases by age, menopausal status, and the period of urine sampling were selected from those who attended a breast cancer mass screening at this hospital. Urinary cadmium levels were measured using spot urine samples. Spot urine samples were collected from cases after surgery but before any cancer therapy. For controls, spot urine samples were obtained at the date of the screening visit. Information on known or suggested breast cancer risk factors was obtained by a self-administered questionnaire. The odds ratios (ORs) and 95 % confidence intervals (CIs) of breast cancer according to the tertile of the creatinine-adjusted cadmium level were calculated using conditional logistic regression models. Women in the highest tertile of the creatinine-adjusted cadmium level (>2.620 µg/g) had significantly elevated OR of breast cancer relative to those in the lowest tertile (<1.674 µg/g) after controlling for covariates [OR = 6.05, (95 % CI 2.90, 12.62)]. The trend of increase in risk with increasing cadmium level was also statistically significant [OR = 1.67, (95 % CI 1.39, 2.01) for every 1.0 µg/g increase in urinary cadmium level, P-trend <0.01]. These data suggested that exposure to cadmium was associated with a risk of breast cancer in Japanese women.

Activation of different signals identified with glia cells contribute to the progression of hyperalgesia.

Hyperalgesia results from a decreased pain threshold, often subsequent to peripheral tissue damage. Recent reports revealed several promising mechanisms of hyperalgesia, but many issues remain unclear. The glial activation accompanying inflammation of neurotransmission in the spinal cord might be related to the initiation and maintenance of hyperalgesia. The present study investigated the pharmacological pain-modifying effects of mitogen-associated protein kinase (MAPK)-related inhibitors identified with glia cells over time during inflammatory pain. A model of inflammatory pain was produced by injecting mustard oil (MO) into the hind paws of rats. Following MO injection, the changes in paws flinching as the early onset of pain and paw withdrawal latency (PWL) in response to thermal stimulation were measured as delayed-onset hyperalgesia. Before and after the MO injection, one of the inhibitors, a p38-MAPK (SB), nuclear factor (NF)-κB (PDTC), BDNF-trk-B (K252a), or JNK-1 (SP), was administered and flinching and PWL were measured. In the SB, PDTC, and k252a groups, early flinching following MO injection was moderately suppressed. Hyperalgesia was significantly suppressed in the left-right difference of PWL in animals receiving SB, k252a, or PDTC pre-treatment. In animals receiving post-treatment, the suppressive effects were most potent in the SP group. The present results revealed that microglial activation resulting from the release of the phosphatase p38-MAPK, the transcription factor NF-κB, and BDNF contributes to the early stage of inflammatory pain. Astrocyte activation accompanying JNK activation contributes to subsequent hyperalgesia. Activation of different signals identified with glia cells is thought to contribute to the progression of hyperalgesia, which represents an applicable finding for the treatment of hyperalgesia.