Revealing the Influence of SiC Particle Size on the Hot Workability of SiCp/6013 Aluminum Matrix Composites.

SiC particle (SiCp) size has been found to significantly influence the hot workability of particle-reinforced aluminum matrix composites (AMC). In this work, therefore, three types of SiCp/6013 composites with different SiCp sizes (0.7, 5 and 15 µm) were prepared and then subjected to isothermal hot compression tests. In addition, constitutive analysis, processing maps and microstructural characterizations were used to reveal the influence of SiCp size on the hot workability of SiCp/6013 composite. The results showed that the values of hot deformation activation energy Q increased with decreasing SiCp size. Specifically, at lower temperatures (e.g., 350 and 400 °C), the highest peak stress was shown in the AMC with SiCp size of 0.7 µm (AMC-0.7), while in the AMC with SiCp size of 5 µm (AMC-5) at higher temperatures (e.g., 450 and 500 °C). This is because a finer SiCp size would lead to stronger dislocation pinning and grain refinement strengthening effects, and such effects would be weakened at higher temperatures. Further, dynamic softening mechanisms were found to transform from dynamic recovery to dynamic recrystallization with increasing SiCp size, and the dynamic recrystallization occurred more easily at higher temperatures and lower strain rates. Consequently, the instability zones of the composites are all mainly located in the deformation region with lower temperature and higher strain rate, and smaller SiCp results in larger instability zones.

Hot Workability of the Multi-Size SiC Particle-Reinforced 6013 Aluminum Matrix Composites.

The size and distribution of ceramic particles in aluminum matrix composites have been reported to remarkably influence their properties. For a single ceramic particle, the particle size is too small and prone to agglomeration, which makes the mechanical properties of the composites worse. When the ceramic particle size is too large, the particles and alloy at the interface are not firmly bonded, and the effect of dispersion distribution is not achieved, which will also reduce the mechanical properties of the composites. The multi-size ceramic particles are expected to improve this situation, while their effect on hot workability is less studied. In this study, the hot deformation behavior, constitutive model, processing map and SEM microstructure were investigated to evaluate the hot workability of multi-size SiC particle-reinforced 6013 aluminum matrix composites. The results showed that the increased deformation temperature and decreased strain rate could decrease flow stresses. The flow stress behaviors of the composites can be described by the sine-hyperbolic Arrhenius equation with the deformation activation energy of Q = 205.863 kJ/mol. The constitutive equation of the composites is ε ˙=3.11592×1013sinh0.024909σ4.12413exp−205863RT. Then, the hot processing map of the SiCp/6013 composites was constructed and verified by SEM observations. The rheological instability zone was in the region of a high strain rate. The optimal processing zone for composites was 450~500 °C and 0.03~0.25 s−1. In addition, the strain level was found to increase both the Q value and the area of the instability zone.

Quantitative assessment of OCT and OCTA parameters in diabetic retinopathy with and without macular edema: single-center cross-sectional analysis.

Aim: The retinal and choroidal parameters were analyzed to understand the impairment of microcirculation of both retina and choroid in patients with diabetic retinopathy (DR). Methods: Fifty-five treatment-naive non-proliferative diabetic retinopathy (NPDR) patients (75 eyes) with type 2 diabetes mellitus (T2DM), including 28 patients (36 eyes) with diabetic macular edema (DME) and 27 patients (39 eyes) without DME, and 25 healthy subjects (47 eyes) were enrolled in this study. The following parameters of DR patients with and without DME were evaluated: the foveal avascular zone area (FAZ-a), FAZ perimeter (FAZ-p), FAZ circularity index (FAZ-CI), total subfoveal choroidal area (TCA), luminal area (LA), stromal area (SA), choroidal vascularity index (CVI), choriocapillaris flow area percentage, superficial capillary plexus (SCP), and deep capillary plexus (DCP). Results: SCP, DCP, and the percentage of choriocapillaris flow area were significantly different between DR patients with and without DME. The DR patients presented lower LA, CVI, and FAZ-CI compared to those of healthy controls (all p < 0.05). The percentage of choriocapillaris flow area in DR patients with and without DME was significantly lower than that in healthy controls (p < 0.05). SCP and DCP were significantly correlated with FAZ-a and FAZ-p but presented insignificant associations with FAZ-CI. Conclusions: Optical coherence tomography (OCT) and OCT angiography (OCTA) parameters, such as LA, CVI, FAZ-CI, and the percentage of choriocapillaris flow area, were reduced compared to those in controls, indicating that the microcirculations of the retina and choroid in the macular area were impaired in DR patients with DME and without DME.

Risk factors for glial cell proliferation after idiopathic macular hole repair with internal limiting membrane flap.

BACKGROUND: To study the influencing factors for different healing patterns of patients with idiopathic macular holes (IMH) after vitrectomy surgery performed with the internal limiting membrane (ILM) flap technique. METHODS: This study was a retrospective, consecutive, observational case series study. We recruited 52 IMH patients who underwent vitrectomy with the ILM flap technique. The participants were divided into 2 groups: group A (25 patients), without significant glial cell proliferation in the macular area on postoperative optical coherence tomography (OCT); and group B (27 patients), with significant glial cell proliferation. The postoperative visual acuity (VA), external limiting membrane (ELM) and ellipsoid zone (EZ) recovery characteristics were compared between the two groups. RESULTS: There were statistically significant differences in minimum linear diameter (MLD) of the macular hole and postoperative VA (p = 0.02, 2.81 E-4 respectively) between the two groups. Compared with patients in group A, patients in group B had poorer VA and EZ recovery in the first 12 months after surgery, and a longer ELM recovery period. The OCT results showed that patients in group B had more extensive ILM filling in the macular area after surgery than patients in group A. CONCLUSION: The presence of aberrant glial cell proliferation was related to a larger MLD of the IMH, and the filling approach for the ILM during the operation was related to the postoperative healing pattern and vision acuity.

Expression of ghrelin and GHSR-1a in mammary glands of dairy goat during the lactation and the effects of gherlin on regulation of mammary function in vitro.

Recent studies have implicated the peripheral actions of ghrelin in reproductive tissues. The present study provides novel evidence for the expression of ghrelin and its functional receptor (GHSR-1a) in the mammary glands of dairy goat during lactation and the effects of ghrelin on regulation of mammary function in vitro. Ghrelin and GHSR-1a mRNA and protein were persistently detected in goat mammary glands throughout the lactation, and patterns of expression of ghrelin, GHSR-1a and ß-casein were generally similar, with highest levels during peak milk yield (day 60-120 of lactation) and lower levels during late (day 180) of lactation. The distribution of ghrelin and GHSR-1a in the mammary glands were substantiated by immunohistochemical method, alveolar and ductal epithelial cells showed distinct immunoreactivity at the different stages of lactation, strong reactivity was seen in most epithelial cells during peak stage, in some alveoli, the vast majority of the epithelial cells were immunoreactivity. Ghrelin and GHSR-1a mRNA expression were demonstrated in cultured primary mammary epithelial cells (MECs). In addition, the results showed that ghrelin could induce a dose-dependent promotion on ß-casein expression in cultured mammary tissues and MECs, and the stimulative effects on ß-casein expression were blocked by D-Lys3-GHRP6 (a GHSR-1a antagonist). Additionally, ghrelin induced a dose-dependent promotion on cell proliferation. Our present findings suggest that ghrelin may play an important role in regulation of mammary function in lactating dairy goats via GHSR-1a.

Phototransformation of selected organophosphorus pesticides: roles of hydroxyl and carbonate radicals.

The phototransformation of two organophosphorus pesticides, parathion and chlorpyrifos, by hydroxyl radicals and carbonate radicals in aqueous solution were studied. Addition of hydrogen peroxide increased the UV degradation rates of both pesticides and data were simulated through kinetic modeling. The second-order rate constants of parathion and chlorpyrifos with hydroxyl radical were determined to be 9.7 +/- 0.5 x 10(9) and 4.9 +/- 0.1 x 10(9) M(-1) s(-1), respectively. The presence of bi/carbonate ions reduced the pesticide degradation rates via scavenging of hydroxyl radical but the formation of carbonate radical also contributed to the degradation of the pesticides with second-order reaction rate constants of 2.8 +/- 0.2 x 10(6) and 8.8 +/- 0.4 x 10(6) M(-1) s(-1) for parathion and chlorpyrifos, respectively. The dual roles of bicarbonate ion in UV/H2O2 treatment systems, i.e., scavenging of hydroxyl radicals and formation of carbonate radicals, were examined and discussed using a simulative kinetic model. The transformation of pesticides by carbonate radicals at environmentally relevant bi/carbonate concentrations was shown to be a significant contributor to the environmental fate of the pesticides and it reshaped the general phototransformation kinetics of both pesticides in UV/H2O2 systems.

The preparation of neem oil microemulsion (Azadirachta indica) and the comparison of acaricidal time between neem oil microemulsion and other formulations in vitro.

The preparation of neem oil microemulsion and its acaricidal activity in vitro was developed in this study. In these systems, the mixture of Tween-80 and the sodium dodecyl benzene sulfonate (SDBS) (4:1, by weight) was used as compound surfactant; the mixture of compound surfactant and hexyl alcohol (4:1, by weight) was used as emulsifier system; the mixture of neem oil, emulsifier system and water (1:3.5:5.5, by weight) was used as neem oil microemulsion. All the mixtures were stired in 800 rpm for 15 min at 40 degrees C. The acaricidal activity was measured by the speed of kill. The whole lethal time value of 10% neem oil microemulsion was 192.50 min against Sarcoptes scabiei var. cuniculi larvae in vitro. The median lethal time value was 81.7463 min with the toxicity regression equations of Y=-6.0269+3.1514X. These results demonstrated that neem oil microemulsion was effective against Sarcoptes scabie var. cuniculi larvae in vitro.

Ultraviolet photolysis of chlorpyrifos: developmental neurotoxicity modeled in PC12 cells.

BACKGROUND: Ultraviolet photodegradation products from pesticides form both in the field and during water treatment. OBJECTIVES: We evaluated the photolytic breakdown of the organophosphate pesticide chlorpyrifos (CPF) in terms of both the chemical entities generated by low-pressure ultraviolet C irradiation and their potential as developmental neurotoxicants. METHODS: We separated by-products using high-performance liquid chromatography and characterized them by gas chromatography/mass spectrometry. We assessed neurotoxicity in neuronotypic PC12 cells, both in the undifferentiated state and during differentiation. RESULTS: Photodegradation of CPF in methanol solution generated CPF oxon and trichloropyridinol, products known to retain developmental neurotoxicant actions, as well as a series of related organophosphate and phosphorothionate derivatives. Exposure conditions that led to 50% degradation of CPF thus did not reduce developmental neurotoxicity. The degradation mixture inhibited DNA synthesis in undifferentiated cells to the same extent as native CPF. In differentiating cells, the products likewise retained the full ability to elicit shortfalls in cell number and corresponding effects on cell growth and neurite formation. When the exposure was prolonged to the point where 70% of the CPF was degraded, the adverse effects on PC12 cells were no longer evident; however, these conditions were sufficiently severe to generate toxic products from the methanol vehicle. CONCLUSIONS: Our results indicate that field conditions or remediation treatments that degrade a significant proportion of the CPF do not necessarily produce inactive products and, indeed, may elicit formation of even more toxic chemicals that are more water soluble and thus have greater field mobility than CPF itself.