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Purpose: The coronavirus 2019 (COVID-19) pandemic—caused by a new type of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)—has posed severe impacts on public health worldwide and has resulted in a total of > 6 million deaths. Notably, male patients developed more complications and had mortality rates ~ 77% higher than those of female patients. The extensive expression of the SARS-CoV-2 receptor and related proteins in the male reproductive tract and the association of serum testosterone levels with viral entry and infection have brought attention to COVID-19’s effects on male fertility. Methods: The peer-reviewed articles and reviews were obtained by searching for the keywords SARS-CoV-2, COVID-19, endocrine, spermatogenesis, epididymis, prostate, and vaccine in the databases of PubMed, Web of Science and Google Scholar from 2020–2022. Results: This review summarizes the effects of COVID-19 on the male reproductive system and investigates the impact of various types of SARS-CoV-2 vaccines on male reproductive health. We also present the underlying mechanisms by which SARS-CoV-2 affects male reproduction and discuss the potentially harmful effects of asymptomatic infections, as well as the long-term impact of COVID-19 on male reproductive health. Conclusion: COVID-19 disrupted the HPG axis, which had negative impacts on spermatogenesis and the epididymis, albeit further investigations need to be performed. The development of vaccines against various SARS-CoV-2 variations is important to lower infection rates and long-term COVID risks.

Although 53BP1 has been established well as a mediator in DNA damage response, its function in mitosis is not clearly understood. We found that 53BP1 is a mitotic-binding partner of the kinases Plk1 and AuroraA, and that the binding with Plk1 increases the stability of 53BP1 by accelerating its interaction with the deubiquitinase USP7. Depletion of 53BP1 induces mitotic defects such as chromosomal missegregation, misorientation of spindle poles and the generation of extra centrosomes, which is similar phenotype to USP7-knockdown cells. In addition, 53BP1 depletion reduces the levels of p53 and centromere protein F (CENPF), interacting proteins of 53BP1. These phenotypes induced by 53BP1 depletion were rescued by expression of wild-type or phosphomimic mutant 53BP1 but not by expression of a dephosphomimic mutant. We propose that phosphorylation of 53BP1 at S380 accelerates complex formation with USP7 and CENPF to regulate their stability, thus having a crucial role in proper centrosome positioning, chromosomal alignment, and centrosome number.

Context.We present the observational results of multi-colour optical monitoring of eight red blazars from 2003 September to 2004 February.Aims.The aim of our monitoring is to investigate the spectral variability as well as the flux variations at short and long time scales.Methods.The observations were carried out using the 1.0 m robotic telescope of Mt. Lemmon Optical Astronomy Observatory, in Arizona, USA, the 0.6 m telescope of Sobaeksan Optical Astronomy Observatory and the 1.8 m telescope of Bohyunsan Optical Astronomy Observatory, in the Republic of Korea.Results.During the observations, all sources show strong flux variations with amplitudes of larger than 0.5 mag. Variations with amplitudes of over 1 mag are found in four sources. Intraday variations with amplitudes larger than 0.15 mag, and a rapid brightness increase with a rate of ~0.2 mag per day in four days, are detected in S5 0716+71. We investigate the relationship between the colour index and source brightness for each source. We find that two out of three FSRQs tend to be redder when they are brighter, and, conversely, all BL Lac objects tend to be bluer. In particular, we find a significant anti-correlation between the $V-I$colour index and Rmagnitude for 3C 454.3. This implies that the spectrum became steeper when the source was brighter, which is opposite to the common trend for blazars. In contrast, significant positive correlations are found in 3C 66A, S5 0716+71, and BL Lac. However, there are only very weak correlations for PKS 0735+17 and OJ 287.Conclusions.We propose that the different relative contributions of the thermal versus non-thermal radiation to the optical emission may be responsible for the different trends of the colour index with brightness in FSRQs and BL Lac objects.

We present a method for optimizing the multi-turn injection efficiency for a medical synchrotron. We show that for a given injection energy, the injection efficiency can be greatly enhanced by choosing transverse tunes appropriately and by optimizing the injection bump and the number of turns required for beam injection. We verify our study by applying the method to the Korea Heavy Ion Medical Accelerator (KHIMA) synchrotron which is currently being built at the campus of Dongnam Institute of Radiological and Medical Sciences (DIRAMS) in Busan, Korea. First the frequency map analysis was performed with the help of the ELEGANT and the ACCSIM codes. The tunes that yielded good injection efficiency were then selected. With these tunes, the injection bump and the number of turns required for injection were then optimized by tracking a number of particles for up to one thousand turns after injection, beyond which no further beam loss occurred. Results for the optimization of the injection efficiency for proton ions are presented.

This land reclamation project used stacked geotextile tubes to construct a 1 km long containment bund. In the past, sand is the preferred infilling material of geotextile tubes due to its ease of construction. However, due to sand scarcity in Singapore, soft soil becomes a potential alternative infilling material. One of the challenges of using soft soil as infilling material is that there will be an excessive settlement and concerns about the overall stability of the stacked tubes. Hence, the soft soil is lightly cemented before infilling into the geotextile tubes. This paper presents the design consideration and the construction sequence of the construction of a stacked geotextile tubes containment bund. Extensive instrumentation was installed at a section of the containment bund to study the behaviour of this geotextile tube. The instrumentation includes strain gauges, pore pressure transducer and total pressure cell. After two years of construction was completed, Standard Penetration Test (SPT) and laboratory triaxial test were used to evaluate the strength of the infilling material. All the instrument data and strength tests results were used to ascertain the performance of the stacked geotextile tubes containment bund.

In this letter, we report the perpendicular magnetic anisotropy of [CoSiB tCoSiBnm/Pd 1.3 nm]5multilayer for tCoSiBequal to 0.1, 0.2, 0.3, 0.4, 0.5 and 0.6 nm and of [CoSiB 0.3 nm/Pd tPdnm]5multilayer for tPdequal to 1.1, 1.2, 1.3, 1.4, 1.5, and 1.6 nm. We also presented to for [CoSiB 0.3 nm/Pd 1.3 nm]nmultilayer for n equal to 3, 5, 7, 9, 11 and 13. The coercivity (Hc) and the saturation magnetization (Ms) of the amorphous ferromagnetic material Co75Si15B10were taken to be 1.6 Oe and 407 emu/cm3, respectively. The Hcin [CoSiB tCoSiBnm/Pd 1.3 nm]5multilayers increased with increasing tCoSiBto reach a maximum at tCoSiB= 0.3 nm and then decreased for tCoSiB> 0.3 nm. The highest Hcof 0.26 k Oe was obtained in [CoSiB 0.3 nm/Pd 1.3 nm]5whereas the lowest Msof 0.26 emu/cm3was obtained in the [CoSiB 0.3 nm/Pd 1.3 nm]3multilayer. Additional Pd layers did not contribute to the perpendicular magnetic anisotropy. The single-domain structure evolved into a striped multi-domain structure as the bilayer repetition number n was increased above 7 after which (n > 7) the hysteresis had a bow-tie shapes.

Abstract: Perpendicular magnetic anisotropy is being widely studied as a possible candidate for a high-density spin-transfer torque magnetic random access memory. The key issues of a high-density spin-transfer torque magnetic random access memory are decreasing the switching current and the high thermal stability. In order to solve these problems, two approaches are suggested: One is the development a new amorphous ferromagnetic material as a pinned layer for a multilayer with a low saturated magnetization (M s ) value because of the interface roughness between the two layers. The other is a search for the most suitable materials with high perpendicular magnetic anisotropy in order to have high thermal stability. In this work, we present an amorphous ferromagnetic Co75Si15B10 material and compare the magnetic properties of a [CoSiB (0.3, 0.4, 0.5 nm)/Pt (1.4 nm)]5 multilayer and new combinations [CoSiB (0.3, 0.4, 0.5 nm)/Au (1.5 nm)]5.

Abstract: This paper presents a design technique to optimize the shape of a vehicle bumper beam that satisfies both the safety requirements for a front rigid-wall impact and the regulations protecting pedestrians from lower leg injuries caused by bumper impacts. An intermediate response surface modeling (IRSM) technique was introduced to approximate the non-linear force-displacement curves obtained from the front impact analysis of a vehicle bumper. The accuracy of the IRSM model was tested by comparing its results with those of the non-linear finite element analysis. The maximum displacement error between the two models did not exceed 3%. Using pedestrian impact analyses based on the experimental arrangement of the Plackett-Burman design, the approximate functions describing the response values acting on the lower legs were calculated. The shape of the bumper beam was optimized by integrating the IRSM with the force-displacement model and the approximate functions on lower leg impact. The optimization results satisfied safety regulations on the maximum allowable displacement of the vehicle bumper, and also the regulations protecting pedestrians from lower leg injuries caused by bumper impacts.

Abstract: Methods have been developed to reduce the side load and friction force acting on the shock absorber inherent in the MacPherson strut system, popularly used in vehicle suspension systems. Reducing this friction force is one of the most important issues in improving the ride comfort of a car. The side load of the shock absorber can be reduced by controlling the force line of the coil spring. To reduce the side load, we designed an S-shaped coil spring. For the design of the side load spring, we also developed an analytical process, which utilizes finite element analysis and mechanical system analysis. All analysis results for the stiffness, stress, fatigue life, and spring force line were validated through experiments.

Doublebarrier magnetic tunnel junctions DMTJs with and without an amorphous ferromagnetic material such as CoFeSiB 10, CoFe 5CoFeSiB 5, and CoFe 10 nm were prepared and compared to investigate the bias voltage dependence of the tunneling magnetoresistance TMR ratio. Typical DMTJ structures were Ta 45Ru 9.5IrMn 10CoFe 7AlOxfree layer 10AlOxCoFe 7IrMn 10Ru 60 in nanometers. The interlayer coupling field and the normalized TMR ratios at the applied voltages of 0.4 and –0.4 V of the amorphous CoFeSiB freelayer DMTJ offer lower and higher values than that of the polycrystalline CoFe freelayer DMTJ, respectively. An amorphous ferromagnetic CoFeSiB layer improves the interface roughness of the free layertunnel barrier and, as a result, the interlayer coupling field and bias voltage dependence of the TMR ratio are suppressed at a given voltage. © 2008 WILEYVCH Verlag GmbH & Co. KGaA, Weinheim

Diphtheria toxin (DT) contains separate domains for receptor-specific binding, translocation, and enzymatic activity. After binding to cells, DT is taken up into endosome-like acidic compartments where the translocation domain inserts into the endosomal membrane and releases the catalytic domain into the cytosol. The process by which the catalytic domain is translocated across the endosomal membrane is known to involve pH-induced conformational changes; however, the molecular mechanisms are not yet understood, in large part due to the challenge of probing the conformation of the membrane-bound protein. In this work neutron reflection provided detailed conformational information for membrane-bound DT (CRM197) in situ. The data revealed that the bound toxin oligomerizes with increasing DT concentration and that the oligomeric form (and only the oligomeric form) undergoes a large extension into solution with decreasing pH that coincides with deep insertion of residues into the membrane. We interpret the large extension as a transition to the open form. These results thus indicate that as a function of bulk DT concentration, adsorbed DT passes from an inactive state with a monomeric dimension normal to the plane of the membrane to an active state with a dimeric dimension normal to the plane of the membrane.

Poly(N-isopropylacrylamide) (PNIPAM) is perhaps the most well-known member of the class of responsive polymers. Free PNIPAM chains have a lower critical solution temperature (LCST) in water at about 30 °C. This very sharp transition (about 5 °C) is attributed to alterations in the hydrogen-bonding interactions of the amide groups. Grafted chains of PNIPAM have shown promise for creating responsive surfaces. Conformational changes of the polymer are likely to play a role in some of these applications, in addition to changes in local interactions. In this work we investigated the temperature-dependent conformational changes of grafted PNIPAM chains in D2O over a range of surface density and molecular weight using neutron reflection. The surface density was controlled using mixed self-assembled monolayers. The molecular weight was controlled using atom transfer radical polymerization (ATRP). Grafted layers were synthesized on gold and also on silicon oxide. The largest conformational changes were observed for intermediate grafting densities and high molecular weights. This is explained by a competition between the well-known chain stretching effect of laterally interacting tethered chains and the phenomenological χ(φ) determined empirically for PNIPAM free chains in water. Comparison is made with the recent numerical SCF calculations of Mendez et al.

The structure and orientation of adsorbed myoglobin as directed by metal−histidine complexation at the liquid−film interface was studied as a function of time using neutron and X-ray reflectivity (NR and XR, respectively). In this system, adsorption is due to the interaction between iminodiacetate (IDA)-chelated divalent metal ions Ni(II) and Cu(II) and histidine moieties at the outer surface of the protein. Adsorption was examined under conditions of constant area per lipid molecule at an initial pressure of 40 mN/m. Adsorption occurred over a time period of about 15 h, allowing detailed characterization of the layer structure throughout the process. The layer thickness and the in-plane averaged segment volume fraction were obtained at roughly 40 min intervals by NR. The binding constant of histidine with Cu(II)-IDA is known to be about four times greater than that of histidine with Ni(II)-IDA. The difference in interaction energy led to significant differences in the structure of the adsorbed layer. For Cu(II)-IDA, the thickness of the adsorbed layer at low protein coverage was ≤20 Å and the thickness increased almost linearly with increasing coverage to 42 Å. For Ni(II)-IDA, the thickness at low coverage was ~ 38 Å and increased gradually with coverage to 47 Å. The in-plane averaged segment volume fraction of the adsorbed layer independently confirmed a thinner layer at low coverage for Cu(II)-IDA. These structural differences at the early stages are discussed in terms of either different preferred orientations for isolated chains in the two cases or more extensive conformational changes upon adsorption in the case of Cu(II)-IDA. Subphase dilution experiments provided additional insight, indicating that the adsorbed layer was not in equilibrium with the bulk solution even at low coverages for both IDA-chelated metal ions. We conclude that the weight of the evidence favors the interpretation based on more extensive conformational changes upon adsorption to Cu(II)-IDA.

Thin films of organosilanes have great technological importance in the areas of adhesion promotion, durability, and corrosion resistance. However, it is well-known that water can degrade organosilane films, particularly at elevated temperatures. In this work, X-ray and neutron reflectivity (XR and NR) were combined with attenuated total reflection infrared (ATR-IR) spectroscopy to study the chemical and structural changes within thin films of (3-glycidoxypropyl)trimethoxysilane (GPS) after exposure for various periods of time to air saturated with either D2O or H2O at 80 °C. For NR and XR, ultrathin (~100 Å) films were prepared by spin-coating. Both D2O and H2O provide neutron scattering contrast with GPS. Variations in the neutron scattering length density (SLD) profiles (a function of mass density and atomic composition) with conditioning time were measured after drying the samples out and also swelled with H2O or D2O vapor at room temperature. For samples that were dried out prior to measurement, little or no change was observed for H2O conditioning up to 3.5 days, but large changes were observed after 30 days of conditioning. The range of conditioning time for this structural change was narrowed to between 4 and 10 days with XR. The SLD profiles indicated that the top portion of the GPS film was transformed into a thick low-density layer after conditioning, but the bottom portion showed little structural change. A previous NR study of as-prepared GPS films involving swelling with deuterated nitrobenzene showed that the central portion of the film has much lower cross-link density than the region nearest the substrate. The present data show that the central portion also swells to a much greater extent with water and hydrolyzes more rapidly. The chemical degradation mechanism was identified by IR as hydrolysis of siloxane bonds. For ATR-IR, GPS films were prepared by dip-coating, which resulted in a greater and more variable thickness than for the spin-coated samples. The IR spectra revealed an increase in vicinal silanol generation over the first 3 days of conditioning followed by geminal silanol generation. Thus, the structural change detected by NR and XR roughly coincided with the onset of geminal silanol generation. Finally, little change in the reflectivity data was observed for films conditioned with D2O at 80 °C for 1 month. This indicates that hydrolysis of Si−O−Si is much slower with D2O than with H2O.

The temperature‐dependent conformational change of poly(N‐isopropylacrylamide) (PNIPAM) brushes in D2O was investigated as a function of the molecular weight (M) at a high grafting density with neutron reflection. PNIPAM chains with three different M values were grafted at the same high surface density from a gold surface by atom transfer radical polymerization. A significant change in the segment concentration profile was observed for all three samples as the temperature passed through the lower critical solution temperature (∼30 °C), in contrast to previous results obtained for samples with much lower surface density. Somewhat surprisingly, the fractional change in the first moment of the segment concentration profile (〈z〉) from 20 to 41 °C was weaker with increasing M. This is contrary to the trend for systems involving only van der Waals (VDW) interactions, in which higher M chains experience larger conformational changes with change in solvent quality. Indeed, the M dependence of the first moment of the segment concentration profile for the grafted PNIPAM chains at 20 °C was much weaker than has been reported previously for dense brushes involving only VDW interactions under good solvent conditions. At 20 °C, the form of the segment concentration profile varied systematically with M. A single‐layer profile resulted for the highest M, but the profiles became more bilayer in character with decreasing M. At 41 °C, the profiles for all three samples were adequately described by a single dense layer with a smooth transition region to bulk D2O. The weak dependence of 〈z〉 on M at 20 °C and the trend from a bilayer profile at lower M to a single‐layer profile at higher M appear to be related. These results are interpreted in terms of concentration‐dependent segment–segment interactions that result in a weak attraction for high segment densities at 20 °C. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 3302–3310, 2004

Silane adhesion promoters are commonly used to improve the adhesion, durability, and corrosion resistance of polymer−oxide interfaces. The current study investigates a model interface consisting of the natural oxide of 〈100〉 Si and an epoxy cured from diglycidyl ether of bisphenol A (DGEBA) and triethylenetetraamine (TETA). The thickness of (3-glycidoxypropyl)trimethoxysilane (GPS) films placed between the two materials provided the structural variable. Five surface treatments were investigated:  a bare interface, a rough monolayer film, a smooth monolayer film, a 5 nm thick film, and a 10 nm thick film. Previous neutron reflection experiments revealed large extension ratios (>2) when the 5 and 10 nm thick GPS films were exposed to deuterated nitrobenzene vapor. Despite the larger extension ratio for the 5 nm thick film, the epoxy/Si fracture energy (Gc) was equal to that of the 10 nm thick film under ambient conditions. Even the smooth monolayer exhibited the same Gc. Only when the monolayer included a significant number of agglomerates did the Gc drop to levels closer to that of the bare interface. When immersed in water at room temperature for 1 week, the threshold energy release rate (Gth) was nearly equal to Gc for the smooth monolayer, 5 nm thick film, and 10 nm thick film. While the Gth for all three films decreased with increasing water temperature, the Gth of the smooth monolayer decreased more rapidly. The bare interface was similarly sensitive to temperature; however, the Gth of the rough monolayer did not change significantly as the temperature was raised. Despite the influence of pH on hydrolysis, the Gth was insensitive to the pH of the water for all surface treatments.

The adsorption of myoglobin to Langmuir monolayers of a metal-chelating lipid in crystalline phase was studied using neutron and X-ray reflectivity (NR and XR) and grazing incidence X-ray diffraction (GIXD). In this system, adsorption is due to the interaction between chelated divalent copper or nickel ions and the histidine moieties at the outer surface of the protein. The binding interaction of histidine with the Ni−IDA complex is known to be much weaker than that with Cu−IDA. Adsorption was examined under conditions of constant surface area with an initial pressure of 40 mN/m. After ~12 h little further change in reflectivity was detected, although the surface pressure continued to slowly increase. For chelated Cu²⁺ ions, the adsorbed layer structure in the final state was examined for bulk myoglobin concentrations of 0.10 and 10 μM. For the case of 10 μM, the final layer thickness was ~43 Å. This corresponds well to the two thicker dimensions of myoglobin in the native state (44 Å × 44 Å × 25 Å) and so is consistent with an end-on orientation for this disk-shaped protein at high packing density. However, the final average volume fraction of amino acid segments in the layer was 0.55, which is substantially greater than the value of 0.44 calculated for a completed monolayer from the crystal structure. This suggests an alternative interpretation based on denaturation. GIXD was used to follow the effect of protein binding on the crystalline packing of the lipids and to check for crystallinity within the layer of adsorbed myoglobin. Despite the strong adsorption of myoglobin, very little change was observed in the structure of the DSIDA film. There was no direct evidence in the XR or GIXD for peptide insertion into the lipid tail region. Also, no evidence for in-plane crystallinity within the adsorbed layer of myoglobin was observed. For 0.1 μM bulk myoglobin concentration, the average segment volume fraction was only 0.13 and the layer thickness was ≤25 Å. Adsorption of myoglobin to DSIDA-loaded with Ni²⁺ was examined at bulk concentrations of 10 and 50 μM. At 10 μM myoglobin, the adsorbed amount was comparable to that obtained for adsorption to Cu²⁺-loaded DSIDA monolayers at 0.1 μM. But interestingly, the adsorbed layer thickness was 38 Å, substantially greater than that obtained at low coverage with Cu−IDA. This indicates that either there are different preferred orientations for isolated myoglobin molecules adsorbed to Cu−IDA and Ni−IDA monolayer films or else myoglobin denatures to a different extent in the two cases. Either interpretation can be explained by the very different binding energies for individual interactions in the two cases. At 50 μM myoglobin, the thickness and segement volume fraction in the adsorbed layer for Ni−IDA were comparable to the values obtained with Cu−IDA at 10 μM myoglobin.

Poly(N-isopropylacrylamide) is perhaps the most well-known member of the class of temperature responsive polymers. It has a lower critical solution temperature (LCST) in water at about 32 °C. This very sharp transition (~5 °C) is attributed to alterations in the hydrogen-bonding interactions of the amide group. In this work we investigated the conformation of end-tethered PNIPAM chains at the interface of silicon with D2O and d-acetone using neutron reflection. End-tethered PNIPAM layers were prepared utilizing the interaction between COOH-terminated PNIPAM and OH-terminated self-assembled monolayers (“method A”) and also by polymerizing N-isopropylacrylamide monomers from the silicon surface (“method B”). Reflectivity data from the protonated layers in deuterated water were obtained using a liquid cell over a range of temperature from 10 to 55 °C. For method A, PNIPAM molecular weights of 33K and 220K were examined. In D2O, we observed very limited change in the conformation of the tethered chains as the temperature increased through the LCST. No conformational change was detected for the lowest molecular weight PNIPAM−COOH sample (33K). Only a slight change in conformation with temperature was detected for the higher molecular weight sample (220K) and the sample from method B. The profiles indicated that the chains were well hydrated above 32 °C, consistent with the observation of very low receding water contact angles. On the other hand, a significant change in the segment concentration profiles occurred when D2O was replaced by d-acetone. Bilayer profiles were observed for all samples in D2O. By contrast, in d-acetone the profiles were composed of a single monotonically decaying layer. Surprisingly, the profiles were more contracted in d-acetone than in D2O despite the fact that PNIPAM dissolves in d-acetone but solutions of PNIPAM in D2O are cloudy above the LCST. This observation, as well as the lack of conformational change with temperature for these low surface density brushes in D2O, is explained on the basis of a concentration-dependent Flory χ parameter.

The interfacial structure and properties of immiscible deuterated polystyrene (dPS)/epoxy bilayer films were investigated with neutron reflectivity as functions of the composition of the epoxy layer, the thickness of the dPS layer, and the annealing time. We have found that the interfacial width and its growth rate depend strongly on the compositions of the epoxy layer but only weakly on the thickness of the dPS layer. The effect of the resin/crosslinker composition on the interfacial width and its growth rate is likely due to the different near-surface structures that result for different epoxy stoichiometries. For an ultra-thin dPS film (thickness = 2Rg), the data suggest a slight suppression of the growth of the interfacial width that could be due to confinement effects for the long-chain molecules such as have been previously reported for a thickness of less than approximately 4Rg, where Rg is the radius of gyration of polymer molecules. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 2653–2660, 2002

The adsorption of the strong polyelectrolyte sodium poly(styrenesulfonate) (NaPSS) to the air surface of water was investigated as a function of polymer concentration from the dilute regime to the beginning of the semidilute regime. Detailed segment profiles of the deuterated polymer were determined by neutron reflection (NR). Data were obtained for 0.67 and 2.50 M KCl. For two samples differing widely in molecular weight (1150 and 56.1 kg/mol), we find that with increasing polymer concentration the adsorbed amount first increases, reaches a maximum, and then decreases strongly. The PSS concentration at which the maximum is reached is dependent on both the molecular weight and the salt concentration in a manner that correlates with the chain overlap concentration. Regarding the segment profiles, at low polymer concentration the profiles are composed of a thin layer of high concentration at the air surface (trains), followed by a distinct second layer of much lower segment concentration that extends to larger depths into the liquid (loops and tails). Complementary X-ray reflection (XR) revealed a localization of ions about 10 Å below the surface for dilute PSS concentration. This layer becomes more diffuse at higher PSS concentration, in conjunction with the decrease in PSS adsorbed amount measured by NR. This surprising behavior of the adsorbed amount with polymer concentration is not explained by current SCF theory treating the adsorption of strong polyelectrolytes to neutral surfaces. We discuss a few possible explanations for this desorption transition. Finally, we observe that the surface tension decreases monotonically with increasing concentration of PSS in bulk solution but is not correlated with the adsorbed amount of PSS at the surface.

The interfacial structure in thin epoxy bilayer films was investigated with neutron reflection. For each experiment, a mixture of crosslinker and deuterated resin was spun onto a chemically similar, fully cured, protonated epoxy film. The reflectivity measurements were performed before and after curing the top epoxy film. We focused on the extent of penetration of the components of the top layer into the network of the bottom layer. The effect of the cure temperature of each layer was examined. In addition, the effect of the initial molecular weight of the oligomers in the top layer was probed by the partial curing of the mixture before spinning. As deposited, the components of the top layer penetrated the bottom layer to an extent that was largely independent of the aforementioned factors. The principal observation was that an additional penetration occurred with curing. This additional penetration was dependent upon both the molecular weight of the top layer and the cure temperature of the top layer relative to the glass-transition temperature of the bottom layer. A decrease in the thickness of the top layer with curing was also observed, which likely indicates some evaporation of oligomers. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1709–1718, 2002

The interfacial structure in thin epoxy bilayer films was investigated with neutron reflection. For each experiment, a mixture of crosslinker and deuterated resin was spun onto a chemically similar, fully cured, protonated epoxy film. The reflectivity measurements were performed before and after curing the top epoxy film. We focused on the extent of penetration of the components of the top layer into the network of the bottom layer. The effect of the cure temperature of each layer was examined. In addition, the effect of the initial molecular weight of the oligomers in the top layer was probed by the partial curing of the mixture before spinning. As deposited, the components of the top layer penetrated the bottom layer to an extent that was largely independent of the aforementioned factors. The principal observation was that an additional penetration occurred with curing. This additional penetration was dependent upon both the molecular weight of the top layer and the cure temperature of the top layer relative to the glass-transition temperature of the bottom layer. A decrease in the thickness of the top layer with curing was also observed, which likely indicates some evaporation of oligomers. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1709–1718, 2002

The interfacial structure in thin epoxy bilayer films was investigated with neutron reflection. For each experiment, a mixture of crosslinker and deuterated resin was spun onto a chemically similar, fully cured, protonated epoxy film. The reflectivity measurements were performed before and after curing the top epoxy film. We focused on the extent of penetration of the components of the top layer into the network of the bottom layer. The effect of the cure temperature of each layer was examined. In addition, the effect of the initial molecular weight of the oligomers in the top layer was probed by the partial curing of the mixture before spinning. As deposited, the components of the top layer penetrated the bottom layer to an extent that was largely independent of the aforementioned factors. The principal observation was that an additional penetration occurred with curing. This additional penetration was dependent upon both the molecular weight of the top layer and the cure temperature of the top layer relative to the glass-transition temperature of the bottom layer. A decrease in the thickness of the top layer with curing was also observed, which likely indicates some evaporation of oligomers. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1709–1718, 2002

Thin films of organosilanes have great technological importance for adhesion promotion, durability, and corrosion resistance. Although the cross-link density profile within such films is likely to strongly affect their performance, no reliable assay has been available to characterize this distribution. In this work we use solvent swelling combined with neutron and X-ray reflection to study the cross-link density distribution within ultrathin films (50−100 Å) of (3-glycidoxypropyl)trimethoxysilane (GPS) and bis(triethoxysilyl)ethane (BTSE) on silicon. The films are swelled with vapors of the good solvent nitrobenzene (NB). For GPS films, the solvent concentration profile has a strong maximum in the central region of the film. We conclude from this that the GPS films possess a high cross-link density near the silicon surface and a much lower cross-link density in the bulk of the film. The decreased solvent concentration at the air surface is more difficult to interpret. It appears to also indicate an elevated cross-link density, but may also involve contributions from other effects such as the difference in surface tension between GPS and NB. The degree of swelling reaches ~50−60% in the bulk of the films. Good reproducibility is obtained for several swelling/deswelling cycles, indicating that swelling with d-NB does not irreversibly change the structure of the network. In contrast to GPS, highly cross-linked films of BTSE do not swell when exposed to d-NB, even though NB is also a good solvent for the BTSE monomers.

AbstractThe relationships between fundamental interfacial interactions, energy dissipation mechanisms, and fracture stress or fracture energy in a glassy thermoset/inorganic solid joint are not well understood. This subject is addressed with a model system involving an epoxy adhesive on a polished silicon wafer containing its native oxide. The proportions of physical and chemical interactions at the interface, and the in-plane distribution, are varied using self-assembling monolayers of octadecyltrichlorosilane (ODTS). The epoxy interacts strongly with the bare silicon oxide surface, but interacts only weakly with the methylated tails of the ODTS monolayer. The fracture stress is examined as a function of ODTS coverage in the napkin-ring (nominally pure shear) loading geometry. The relationship between fracture stress and ODTS coverage is catastrophic, with a large change in fracture stress occurring over a narrow range of ODTS coverage. This transition in fracture stress does not correspond to a wetting transition of the epoxy. Rather, the transition in fracture stress corresponds to the onset of large-scale plastic deformation within the epoxy. We postulate that the transition in fracture stress occurs when the local stress that the interface can support becomes comparable to the yield stress of the epoxy. The fracture results are independent of whether the ODTS deposition occurs by island growth (Tdep= 10°C) or by homogeneous growth (Tdep= 24°C).

The behavior of Langmuir monolayers of octadecyl-substituted preformed polyimide molecules exhibits a strong dependence on temperature when the isotherms are measured using a Wilhelmy balance. This suggests a change in structure with temperature, though isotherms measured with a Langmuir balance change only modestly with temperature. Brewster angle microscopy images of the monolayer morphology are consistent with the notion that the monolayer is extremely rigid at 20−21 °C, while it has somewhat more fluidity at 28 °C. Polarization-modulated infrared reflection absorption spectroscopy results also indicate a qualitative difference between the characters of the monolayer at the two temperatures. The Wilhelmy plate method is sensitive to this difference, but its limited accuracy in the case of very rigid films results in a response that greatly amplifies the character of this change as compared to other means of probing the monolayer structure.

The adsorption of the strong polyelectrolyte poly(styrenesulfonate) (PSS) to the air surface of dilute aqueous solutions was investigated as a function of molecular weight and salt concentration. Detailed segment profiles of the deuterated polymer were determined by neutron reflection. Surface activity was also examined through surface tension measurements. In general, the segment profiles are composed of a thin layer (10−20 Å thick) of high concentration at the air surface, followed by a distinct second layer of much lower segment concentration that extends to larger depths into the liquid. The high segment density at the air surface is due to a strong surface attraction, arising from the low surface energy of the PSS backbone relative to the surface tension of water. At low salt concentration, the profiles tend toward a single dense layer, suggesting that the chains lie nearly flat at the interface in that limit. The adsorbed amount increases with salt concentration, with a stronger dependence for higher molecular weight chains. The adsorbed amounts at the air/water interface are higher than reported previously for PSS adsorbed onto neutral solid surfaces, consistent with the fact that the air−liquid interface provides a stronger surface attraction. While the trends of adsorbed amount with salt concentration and molecular weight are in good agreement with numerical self-consistent-field lattice calculations, the measured bilayer profiles are rather different from the smoothly decaying theoretical profiles. The surface tensions of the PSS solutions are significantly lowered relative to those of pure salt solutions. Combining the reflectivity and surface tension measurements, an approximately linear relationship is established between the surface pressure and the PSS adsorbed amount.

Structure within thin epoxy films is investigated by neutron reflectivity (NR) as a function of resin/cross-linker composition and cure temperature. Variation in the cross-link density normal to the substrate surface is examined by swelling the films with the good solvent d-nitrobenzene (d-NB). The principal observation is a large excess of d-NB near the air surface. This is not a wetting layer, but rather indicates a lower cross-link density in the near-surface region. This effect is due to preferential segregation of the cross-linker to the air surface, driven by the lower surface tension of the cross-linker relative to the epoxide oligomers. The magnitude of the effect is a function of composition and cure temperature. Exclusion of d-NB from the region immediately adjacent to the substrate surface is also observed, possibly indicating a tightly bound layer of epoxy. Regarding swelling in the bulk of the films, the behavior is nonsymmetric with departure from the stoichiometric ratio. The films deficient in curing agent show greater equilibrium swelling and faster swelling kinetics than the films with an excess of curing agent.

Monolayers of alkyl side chain substituted poly(ferrocenylsilane) (FCSIOCT) have been studied for the first time. The monolayer behavior is found to be strongly temperature dependent and also to change distinctly when the monolayer is oxidized by addition of FeCl3 to the polymer before spreading. The zero pressure area per repeat unit for the unoxidized polymers is ~20 Ų at 20 °C, which suggests that the ferrocene moiety must be excluded from the water surface and the silane repeat units with the aliphatic side chains alone occupy the surface area on the air−water interface. The FCSIOCT monolayer mixed with FeCl3 shows the liquid analogous state occurring at much larger areas, with a plateau region appearing in the isotherm at 44 mN/m. The zero pressure area in the liquid analogous state is ~45 Ų, which is almost equal to the theoretical area required for both the silane and ferrocene moieties to be at the surface. For both monolayers, the area per repeat unit continuously decreases with time at constant pressure. Monolayers transferred onto substrates have been studied using X-ray reflectometry. The thickness of the unoxidized FCSIOCT monolayer is higher than that of the oxidized monolayer. When the oxidized monolayer relaxes on the water surface, the thickness increases and approaches the thickness of the pure FCSIOCT monolayer.

The aim of the present study was to determinethe efficacy of a new combination regimen including anantioxidant, a proton pump inhibitor, and antibioticsagainst Helicobacter pylori and to document the changes of oxidative stress and cytokinesinvolved in H. pylori-associated gastric inflammation.From 57 patients with endoscopically diagnosed gastricand/or duodenal ulcers associated with H. pylori infection five gastric antral biopsy specimenswere taken for the diagnosis of H. pylori and for theexperimental measures. The patients were then treatedeither with lansoprazole 30 mg + amoxicillin 1.5 g (LAgroup; 21 patients) or lansoprazole 30 mg amoxicillin1.5 g + rebamipide 300 mg (LAM group; 36 patients) fortwo weeks. Four weeks after the initiation of treatment,the patients were endoscoped again and biopsy specimens were obtained. Mucosalmalondialdehyde (MDA) levels; myeloperoxidase (MPO)activities; superoxide dismutase; catalase; glutathioneperoxidase; cytokines IL-1, IL-6, TNF-α; andchemokines IL-8, GRO-α, RANTES (regulated onactivation normal T expressed and secreted) weremeasured. Using paraffin-embedded tissue sections, insitu terminal deoxyribonucleotide transferase (TdT)mediated dUTP nick end labeling (TUNEL) for apoptosisand immunohistochemical staining for inducible nitricoxide synthase (iNOS) were performed. Two weeks oftreatment with the LA regimen resulted in 57.4%eradication rates of H. pylori, whereas two weeks oftreatment with the LAM regimen resulted in 75.0%eradication rates. Eradication rates between these twogroups were statistically significantly different (P< 0.05). Mucosal MDA levels and MPO activities weresignificantly lower in the LAM group than the LA group.Mucosal levels of cytokines IL-1, IL-6, and TNF-αand of chemokines IL-8, GRO-α, and RANTES were all significantly decreased after the treatmentof H. pylori, especially so in the LAM group. Theapoptotic index and iNOS score were significantlyreduced after the eradication of H. pylori. The addition of an antioxidative drug to the eradicationregimen against H. pylori has advantages either inaugmenting the eradication rates of H. pylori or indecreasing the oxidative stress and cytokines levelsgenerated by H. pylori infection.

Multilayer films of preformed polyimide molecules have been obtained for the first time by the Langmuir−Blodgett technique. The pressure−area isotherm shows that the polyimide monolayers are strongly dependent on compression rate. The zero-pressure area per repeat unit is about 1.7 nm² when the film is compressed at 100 cm²/min. This value is higher than that expected (1.2 nm²) for a closely packed structure. Multilayers have been investigated with X-ray reflectometry. The thickness of a bilayer film is about 4.05 nm, which is between the average bilayer thickness of a interdigitated multilayer film and that of a bilayer film containing closely packed backbones and fully extended alkyl side chains. The multilayer films do not display a distinctively periodic structure. When the films are annealed for a few hours at 180 °C, the structure relaxes somewhat and thickness decreases slightly.

A series of mixed self-assembled monolayers of functionalized (Br(CH2)11SiCl3) and unfunctionalized (CH3(CH2)10SiCl3) alkyltrichlorosilanes of different compositions have been prepared on bulk silicon substrates. By in situ modification of these monolayers the bromo end groups were transformed to amino end groups as shown by X-ray photoelectron spectroscopy measurements. The change of hydrophilicity was monitored by water contact angle measurements, showing the expected decrease of contact angles with increase amino group content on the surface. These substrates were used to initiate N-carboxyanhydrides in dioxane to yield α-helical polypeptides grafted from the surface. The thicknesses of the obtained polymer layers were measured with ellipsometry and X-ray reflectometry. Fourier transform infrared measurements confirm that the grafted polymers are in the α-helical conformation.

Oxidation-reduction properties of methylglyoxal-modified protein in relation to free radical generation were investigated. Glycation of bovine serum albumin by methylglyoxal generated the protein-bound free radical, probably the cation radical of the cross-linked Schiff base, as observed in the reaction of methylglyoxal with L-alanine (Yim, H.-S., Kang, S.-O., Hah, Y. C., Chock, P. B., and Yim, M. B. (1995) J. Biol. Chem. 270, 28228-28233) or with Nalpha-acetyl-L-lysine. The glycated bovine serum albumin showed increased electrophoretic mobility suggesting that the basic residues, such as lysine, were modified by methylglyoxal. The glycated protein reduced ferricytochrome c to ferrocytochrome c in the absence of oxygen or added metal ions. This reduction of cytochrome c was accompanied by a large increase in the amplitude of the electron paramagnetic resonance signal originated from the protein-bound free radical. In addition, the glycated protein catalyzed the oxidation of ascorbate in the presence of oxygen, whereas the protein free radical signal disappeared. These results indicate that glycation of protein generates active centers for catalyzing one-electron oxidation-reduction reactions. This active center, which exhibits enzyme-like characteristic, was suggested to be the cross-linked Schiff base/the cross-linked Schiff base radical cation of the protein. It mimics the characteristics of the metal-catalyzed oxidation system. The glycated bovine serum albumin cross-linked further to the cytochrome c in the absence of methylglyoxal. The cross-linked cytochrome c maintains its oxidation-reduction properties. These results together indicate that glycated proteins accumulated in vivo provide stable active sites for catalyzing the formation of free radicals.

The formation of alpha-dicarbonyl compounds seems to be an important step for cross-linking proteins in the glycation or Maillard reaction. To elucidate the mechanism for the cross-linking reaction, we studied the reaction between a three-carbon alpha-dicarbonyl compound, methylglyoxal, and amino acids. Our results showed that this reaction generated yellow fluorescent products as formed in some glycated proteins. In addition, three types of free radical species were also produced, and their structures were determined by EPR spectroscopy. These free radicals are 1) the cross-linked radical cation, 2) the methylglyoxal radical anion as the counterion, and 3) the superoxide radical anion produced only in the presence of oxygen. The generation of the cross-linked radical cations and the methylglyoxal radical anions does not require metal ions or oxygens. These results indicate that dicarbonyl compounds cross-link free amino groups of protein by forming Schiff bases, which donate electrons directly to dicarbonyl compounds to form the cross-linked radical cations and the methylglyoxal radical anions. Oxygen can accept an electron from the radical anion to generate a superoxide radical anion, which can initiate damaging chain reactions. Time course studies suggest that the cross-linked radical cation is a precursor of yellow fluorescent glycation end products.

A new osmotically inducible gene in Escherichia coli, osmY, was induced 8- to 10-fold by hyperosmotic stress and 2- to 3-fold by growth in complex medium. The osmY gene product is a periplasmic protein which migrates with an apparent molecular mass of 22 kDa on sodium dodecyl sulfate-polyacrylamide gels. A genetic fusion to osmY was mapped to 99.3 min on the E. coli chromosome. The gene was cloned and sequenced, and an open reading frame was identified. The open reading frame encoded a precursor protein with a calculated molecular weight of 21,090 and a mature protein of 18,150 following signal peptide cleavage. Sequencing of the periplasmic OsmY protein confirmed the open reading frame and defined the signal peptide cleavage site as Ala-Glu. A mutation caused by the osmY::TnphoA genetic fusion resulted in slightly increased sensitivity to hyperosmotic stress.

We report the detection of endogenous intracellular glutathionyl (GS.) radicals in the intact neuroblastoma cell line NCB-20 under oxidative stress. Spin-trapping and electron paramagnetic resonance (EPR) spectroscopic methods were used for monitoring the radicals. The cells incubated with the spin trap 5,5-dimethyl-1-pyrroline 1-oxide (DMPO) were challenged with H2O2 generated by the enzymic reaction of glucose/glucose oxidase. These cells exhibit the EPR spectrum of the GS. radical adduct of DMPO (DMPO-.SG) without exogenous reduced glutathione (GSH). The identity of this radical adduct was confirmed by observing hyperfine coupling constants identical to previously reported values in in vitro studies, which utilized known enzymic reactions, such as horseradish peroxidase and Cu/Zn superoxide dismutase, with GSH and H2O2 as substrates. The formation of the GS. radicals required viable cells and continuous biosynthesis of GSH. No significant effect on the resonance amplitude by the addition of a membrane-impermeable paramagnetic broadening agent indicated that these radicals were located inside the intact cell. N-Acetyl-L-cysteine (NAC)-treated cells produced NAC-derived free radicals (NAC.) in place of GS. radicals. The time course studies showed that DMPO-.SG formation exhibited a large increase in its concentration after a lag period, whereas DMPO-NAC. formation from NAC-treated cells did not show this sudden increase. These results were discussed in terms of the limit of antioxidant enzyme defenses in cells and the potential role of the GS. radical burst in activation of the transcription nuclear factor NF-kappa B in response to oxidative stress.

Cu,Zn-superoxide dismutase (SOD) is known to be a locus of mutation in familial amyotrophic lateral sclerosis (FALS). Transgenic mice that express a mutant Cu,Zn-SOD, Gly-93--> Ala (G93A), have been shown to develop amyotrophic lateral sclerosis (ALS) symptoms. We cloned the FALS mutant, G93A, and wild-type cDNA of human Cu,Zn-SOD, overexpressed them in Sf9 insect cells, purified the proteins, and studied their enzymic activities for catalyzing the dismutation of superoxide anions and the generation of free radicals with H2O2 as substrate. Our results showed that both enzymes contain one copper ion per subunit and have identical dismutation activity. However, the free radical-generating function of the G93A mutant, as measured by the spin trapping method, is enhanced relative to that of the wild-type enzyme, particularly at lower H2O2 concentrations. This is due to a small, but reproducible, decrease in the value of Km for H2O2 for the G93A mutant, while the kcat is identical for both enzymes. Thus, the ALS symptoms observed in G93A transgenic mice are not caused by the reduction of Cu,Zn-SOD activity with the mutant enzyme; rather, it is induced by a gain-of-function, an enhancement of the free radical-generating function. This is consistent with the x-ray crystallographic studies showing the active channel of the FALS mutant is slightly larger than that of the wild-type enzyme; thus, it is more accessible to H2O2. This gain-of-function, in part, may provide an explanation for the association between ALS and Cu,Zn-SOD mutants.