Model based on trap-assisted tunneling for two-level current fluctuations in submicrometer metal-silicon-dioxide-silicon diodes.
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Journal Article↗
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Influence of silicon dioxide-silicon interface trap charges on the performance of monolithic metal-zinc oxide-silicon nitride-silicon dioxide-silicon convolver.
An enhancement in the convolution efficiency is obtained by annihilating the SiO2-Si interface trap charges in the metal-ZnO-Si3N4-SiO2-Si convolver structure. The annealing process uses a source of hydrogen created underneath the SiO2-Si interface by implanting H3(+) ion followed by rapid thermal anneal of 5s at 900 degrees C. The silicon nitride layer is inducted to protect ZnO films from hydrogen influx during low temperature oxygen anneal.
Letter↗
Comparing study of the effect of nanosized silicon dioxide and microsized silicon dioxide on fibrogenesis in rats.
This study compares the effect of nanosized silicon dioxide (nanosized SiO2) and microsized silicon dioxide (microsized SiO2) particles on fibrogenesis in rats. Wistar rats were instilled intratracheally with saline, 20 mg of nanosized SiO2 or 20 mg of microsized SiO2, and were sacrificed at 1 and 2 months after instillation. The lungs of rats were analysed for the changes of lung/body coefficient and hydroxyproline content. Changes in pathology and fibrotic grade were observed by use of hematoxylin and eosin and Van Gieson dyeing. The expression of interleukin-4 (IL-4) and transforming growth factor-beta1 (TGF-beta1) was observed by use of immunohistochemical technique, and protein expression quantitatively analysed by image analysis. The lung/body coefficient and hydroxyproline content of nanosized SiO2 groups were significantly lower than those of microsized SiO2 groups at both 1 and 2 months after instillation (P<0.05 or P<0.01), but without significant differences from those of saline control groups. At 1 month after instillation, there were mainly cellular nodules (Stage I) in nanosized SiO2 group, while in microsized SiO2 group Stage II, II+ of silicotic nodules were observed. At 2 months after instillation, there were still Stage I of silicotic nodules in nanosized SiO2 group. In microsized SiO2 group mainly Stage II+, III of silicotic nodules were found. Quantity image analysis showed that the expressions of IL-4 and TGF-beta1 in nanosized SiO2 groups were significantly lower than those in microsized SiO2 groups (P<0.01), but without significant difference from those of saline control groups. Our experiment revealed that the effect of fibrogenesis of nanosized SiO2 might be milder than that of microsized SiO2 in rats, potentially resulting from nanoparticals tending to be diffused and easily translocated due to their ultrafine particle size compared to microsized particles.
Animals↗
Pinpoint and bulk electrochemical reduction of insulating silicon dioxide to silicon.
Silicon dioxide (SiO(2)) is conventionally reduced to silicon by carbothermal reduction, in which the oxygen is removed by a heterogeneous-homogeneous reaction sequence at approximately 1,700 degrees C. Here we report pinpoint and bulk electrochemical methods for removing oxygen from solid SiO(2) in a molten CaCl(2) electrolyte at 850 degrees C. This approach involves a 'contacting electrode', in which a metal wire supplies electrons to a selected region of the insulating SiO(2). Bulk reduction of SiO(2) is possible by increasing the number of contacting points. The same method was also demonstrated with molten LiCl-KCl-CaCl(2) at 500 degrees C. The novelty and relative simplicity of this method might lead to new processes in silicon semiconductor technology, as well as in high-purity silicon production. The methodology may be applicable to electrochemical processing of a wide variety of insulating materials, provided that the electrolyte dissolves the appropriate constituent ion(s) of the material.
Calcium Chloride↗
[Comparative study of nanosized and microsized silicon dioxide on spermatogenesis function of male rats].
OBJECTIVE: To compare the effects of nanosized and microsized silicon dioxide on spermatogenesis function of male rats exposed by inhalation. METHODS: 45 male rats were randomly divided into control group and four experimental groups which were exposed by 100 mg/m3 or 300 mg/m3 nanosized and microsized silicon dioxide in inhalation chambers 2 hours every other day. Age-matched rats were exposed to room air with the same condition and served as controls. 65 days later, the testicular and epididymal viscera coefficients, the quantity and quality of sperm were examined and the histopathological assessment was done. The changes in biochemical parameters in serum and testes were also measured. RESULTS: Nanosized silicon dioxide could induce histopathological changes of testes in rats, and the effect was higher than that of microsized particles at the same concentration. Nanosized silicon dioxide could reduce the sperm counts of rats and the testicular LDH-C4 activities, increase MDA levels in the testes and the effect was higher than that of microsized particles at the same concentration. Nanosized silicon dioxide could lead to the reduction of sperm motility, testicular LDH-C4 activities and 8-hydroxydeoxyguanosine (8-OHdG) concentration in serum elevation in particles-exposed rats compared with the control animals, but there are no significant difference compared with that of microsized particles at the same concentration. CONCLUSION: The present findings suggest a different effect of impairment of sperm production and maturation induced by inhalation of nanosized and microsized silicon dioxide, and nanosized silicon dioxide exerted more severe reaction.
Animals↗
Experimental influenza virus infection, silicon dioxide polymorphs, and pulmonary fibrogenesis.
Inhalation exposure to silicon dioxide is known to result in acute lung injury followed by pulmonary fibrosis. Recently it has been shown that the acute lung damage during influenza virus infection is also followed by a fibrogenic process. To investigate the interaction between silicon dioxide and influenza virus infection, mice were intratracheally instilled with either alpha-quartz or cristobalite and 3 d later infected by aerosol inhalation with influenza A/PR8/34 virus. At 30, 60, and 90 d after infection, groups of virus infected and noninfected mice were sacrificed and their lungs assessed for total and differential lavage cell counts, lung hydroxyproline content, and morphometric analysis. The silica polymorphs did not alter the proliferation of virus in the lungs as quantitated by infectious virus titers of lung homogenates at 1, 5, 7, 10, and 13 d after infection. In noninfected animals, cristobalite was more reactive than alpha-quartz. The virus infection, in all parameters measured at all time intervals, enhanced the overall fibrogenic response of the lungs to the mineral dusts, suggestive of an additive fibrogenic model. The data demonstrate that virus infection following silicon dioxide exposure results in an interaction that leads to an enhanced fibrogenic response.
Albumins↗
Determination of traces of bismuth by quenching of solid-substrate room-temperature phosphorescence from morin-labeled silicon dioxide nano-particles.
Silicon dioxide nano-particles, diameter 50 nm, containing morin (morin-SiO2) have been synthesized by the sol-gel method. They emit strong and stable room-temperature phosphorescence (SS-RTP) on filter paper as substrate, and bismuth can quench the intensity of the SS-RTP. On this basis a new morin-SiO2 solid-substrate room-temperature phosphorescence-quenching method has been established for determination of traces of bismuth. Reduction of phosphorescence intensity (DeltaI(p)) is directly proportional to the concentration of bismuth in the working range 0.16-14.4 ag spot(-1) (sample volume 0.40 muL spot(-1), corresponding to the concentration range 0.40-36.0 fg mL(-1)). The regression equation of the working curve is DeltaI(p)=14.86+5.279x[Bi3+] (ag spot(-1)) (n=6, r=0.9982). The detection limit of this method is 0.026 ag spot(-1) (corresponding to a concentration of 6.5 x 10(-17) g mL(-1)).This sensitive, reproducible and accurate method has been used for successful analysis of real samples.
Journal Article↗
Monocyte-dependent stimulation of human T cells by silicon dioxide.
Mononuclear cells were isolated by Ficoll-Hypaque density gradient centrifugation from randomly selected silicone breast implant recipients for testing. Restricted antibody to HLA-DR (28-33 kD) depleted the concanavalin A mitogenic response which was expected but failed to inhibit the proliferative response to silicon dioxide. Further testing with monoclonal antibodies to HLA-DP, -DQ, and a second -DR with specificity for the NS1 region of the MHC class II genome, all markedly inhibited proliferation of T cells despite otherwise adequate stimulation by concanavalin A or silicon dioxide. Monoclonal antibodies directed against B7-1 also inhibited proliferation of T cells following stimulation with concanavalin A or silicon dioxide. These results confirm the T-cell response to silicon dioxide is monocyte-dependent and not a superantigen as has been speculated.
Antibodies, Monoclonal↗
[Expression and role of nuclear transcription factor Sp1 in macrophages stimulated by silicon dioxide].
OBJECTIVE: To study the expression and localization of nuclear transcription factor Sp1 in macrophages after stimulated by silicon dioxide in vivo and in vitro. METHODS: Forty Sprague Dawley rats were randomly divided into the control group and the silica exposure group, 20 in each group. The rat silicosis models were established by direct tracheal instillation of silica into rat lung (0.2 g/kg) only once while the control group was instilled with equal amount of saline. Animals were killed at 1st, 7th, 14th, 21st and 28th day after instillation. Dynamic changes of Sp1 protein expression and its cellular localization were detected by immunohistochemistry in pulmonary macrophages. In vitro, Sp1 mRNA and protein expression and their dynamic changes were monitored by RT-PCR and western blotting after stimulated by silicon dioxide in cultured RAW264.7 macrophages respectively. Cellular localization of Sp1 protein was characterized by immunocytochemistry. RESULTS: Compared to the control group, the Sp1 protein expression was increased in pulmonary macrophages and reached the peak at the 14th day in the silica exposure group. In vitro, the Sp1 mRNA level began to rise at 30 minutes after the administration of silicon dioxide and reached the peak at 240 minutes and then decreased to the minimal level at 960 minutes. The Sp1 total protein and nuclear protein also exhibited the similar trend. The former reached the peak at 240 minutes and the latter at 480 minutes. The significant nuclear translocation of Sp1 protein was observed at 120 minutes after the administration of silicon dioxide and became most significant at 480 minutes. CONCLUSION: Silicon dioxide can activate nuclear transcription factor Sp1 in macrophages in vivo and in vitro. Sp1 might play an important pathogenic role in the development of silicosis.
Animals↗
Silicon dioxide calculi in humans in the absence of silicate antacid medication.
The occurrence of silicon dioxide in human urinary calculi is more common than generally believed. During a 3 year study we have analyzed about 750 human urinary calculi using the scanning electron microscope and x-ray crystallographic methods. Silicon dioxide of the alpha quartz variety was found to be the principal constituent in calculi from 5 male patients. Some of the patients were recurrent stone formers and 1 patient has previously produced a silicon dioxide calculus. In none of the 5 cases was there any history of gastric disorders or of any ingestion of antacids in the form of magnesium trisilicate. Some of the silica particles have a morphology typical of glacial sand.
Adult↗
[Expression of early growth response gene-1 in macrophages stimulated by silicon dioxide].
OBJECTIVE: To study the expression and localization of early growth response gene-1 (Egr-1) in macrophages after stimulation by silicon dioxide in vivo and in vitro and to discuss the role of Egr-1 in the development of silicosis. METHODS: The expression of Egr-1 in animal model of silicosis was analyzed by using immunohistochemistry. Western-blot, immunofluorescence and RT-PCR analysis were used to detect the expression and localization of Egr-1 protein and the dynamic changes of Egr-1 mRNA in cultured macrophages RAW264.7, after stimulation by silicon dioxide. RESULTS: In animal model with induced silicosis, there was an increased expression of Egr-1 in pulmonary macrophages. The expression levels peaked at the 14th day. In vitro, the transcription of Egr-1 increased in RAW264.7 macrophages during 15 to 240 minutes after the administration of silicon dioxide. The response peaked at 15 minutes and diminished to a minimal level at 480 minutes. Nuclear translocation was most apparent at 60 minutes, lasted till 120 minutes and diminished gradually. During the period from 60 to 120 minutes, the expression of Egr-1 protein also reached a peak. CONCLUSIONS: Silicon dioxide can activate the nuclear transcription factor Egr-1 in vivo and in vitro in macrophages. Egr-1 may thus play an important pathogenetic role in the development of silicosis.
Animals↗
Alternative dielectrics to silicon dioxide for memory and logic devices
The silicon-based microelectronics industry is rapidly approaching a point where device fabrication can no longer be simply scaled to progressively smaller sizes. Technological decisions must now be made that will substantially alter the directions along which silicon devices continue to develop. One such challenge is the need for higher permittivity dielectrics to replace silicon dioxide, the properties of which have hitherto been instrumental to the industry's success. Considerable efforts have already been made to develop replacement dielectrics for dynamic random-access memories. These developments serve to illustrate the magnitude of the now urgent problem of identifying alternatives to silicon dioxide for the gate dielectric in logic devices, such as the ubiquitous field-effect transistor.
Journal Article↗
Biphasic cellular and tissue response of rat lungs after eight-day aerosol exposure to the silicon dioxide cristobalite.
Cristobalite is a crystalline silicon dioxide that elicits pulmonary inflammation and fibrosis in humans and experimental animals. Exposure of rats to aerosols of respirable cristobalite for 8 days led to a rapid influx of neutrophils and macrophages into alveolar and tissue compartments of the lung followed by a more gradual accumulation of T lymphocytes. This inflammatory response persisted throughout 52 weeks after the end of the exposure. For some variables studied there appeared to be a cyclical nature to the response. Statistical analysis of alveolar cell populations and lung tissue weight, protein, and hydroxyproline showed significant time-dependent fluctuations. Histologic analysis revealed a progressive deposition of collagen and type II cell hyperplasia centered on airways, however, there appeared to be some correlation between fluctuations in alveolar cell populations and overall tissue pathology. The observed cellular and biochemical fluctuations and the persistence of the inflammatory response may be due to the presence of silica in the lung, which serves as a source of repetitive stimulation of lung cells.
Aerosols↗
Partial dewetting of polyethylene thin films on rough silicon dioxide surfaces.
The effect of roughness on the dewetting behavior of polyethylene thin films on silicon dioxide substrates is presented. Smooth and rough silicon dioxide substrates of 0.3 and 3.2-3.9 nm root-mean-square roughness were prepared by thermal oxidation of silicon wafers and plasma-enhanced chemical vapor deposition on silicon wafers, respectively. Polymer thin films of approximately 80 nm thickness were deposited by spin-coating on these substrates. Subsequent dewetting and crystallization of the polyethylene were observed by hot-stage optical microscopy in reflection mode. During heating, the polymer films melt and dewet on both substrates. Further observations after cooling indicate that, whereas complete dewetting occurs on the smooth substrate surface, partial dewetting occurs for the polymer film on the rough surface. The average thickness of the residual film on the rough surface was determined by ellipsometry to be a few nanometers, and the spatial distribution of the polymer in the cavities of the rough surface could be obtained by X-ray reflectometry. The residual film originates from the impregnation of the porous surface by the polymer fluid, leading to the observed partial dewetting behavior. This new type of partial dewetting should have important practical consequences, as most real surfaces exhibit significant roughness.
Crystallization↗
A food-grade silicon dioxide is hypocholesterolemic in the diet of cholesterol-fed rats.
Silicon dioxide, commonly referred to as silica, is present in plant cell walls and interstitial spaces, and is often found as a component of dietary fibers that have exhibited hypocholesterolemic activity in animals. The primary objective of this study was to determine the cholesterolemic effects of two different morphological forms of silicon in the diet of cholesterol-fed rats. Male Wistar rats were provided diets containing 1 g cholesterol/100 g diet, and 0.65 g Si/100 g diet as either a sodium salt (silicate group) or silicon dioxide, a synthetic silica polymer (silica group). Cellulose was used as a control (control group). The in vitro bile acid binding capacity of the SiO2 was also measured. After 44 d of diet administration, animals were deprived of food for 24 h and then killed. Plasma total, VLDL, and LDL cholesterol concentrations were 18%, 29%, and 26% lower, respectively, in the silica group than in the control group. However, liver cholesterol concentrations were not different among dietary treatments. During the initial 15 d of the study, average daily total fecal bile acids were 38% higher in the silica group than in the control group, but fecal bile acid outputs were not different for the remainder of the experiment. The silica polymer used in the feeding trial was found to adsorb 5 times more cholate than chenodeoxycholate, at pH 7.5 in vitro. In vivo, the potential for silica to enhance fecal cholic acid excretion, relative to chenodeoxycholic acid during the initial stage of the study, may have contributed to the hypocholesterolemic response to the silica diet.(ABSTRACT TRUNCATED AT 250 WORDS)
Administration, Oral↗
Investigation of the glidant properties of compacted colloidal silicon dioxide by angle of repose and X-ray photoelectron spectroscopy.
The optimal flow-enhancing effect of a new compacted, hydrophilic colloidal silicon dioxide (AEROSIL 200 VV Pharma) on microcrystalline cellulose (Avicel PH 101) and pregelatinized starch (Starch 1500) was found to be 0.25% under gentle and 0.125% under strong mixing conditions, as measured by the angle of repose. The effect could be explained by X-ray photoelectron spectroscopy (XPS) investigations. The Si 2p signals of the silicon dioxide indicated that the coverage of the excipient surface with AEROSIL was greater for all mixtures produced under strong mixing conditions and corresponded to a higher degree of de-agglomeration of the AEROSIL aggregates. The more extensive surface coverage of Avicel PH 101 as compared to Starch 1500 could be explained by the particle morphology on the one hand and by the XPS C 1s signals on the other. Due to the different conformation of the two excipients, Avicel PH 101 offers a higher density of hydroxyl groups on its surface which are available for hydrogen bonding with the surface hydroxyl groups of hydrophilic colloidal silicon dioxide.
Cellulose↗
Food applications and the toxicological and nutritional implications of amorphous silicon dioxide.
The chemical and physical characteristics of the different types of amorphous silicon dioxide contribute to the versatility of these compounds in a variety of commercial applications. Traditionally, silicas have had a broad spectra of product usage including such areas as viscosity control agents in inks, paints, corrosion-resistant coatings, etc. and as excipients in pharmaceuticals and cosmetics. In the food industry, the most important application has been as an anticaking agent in powdered mixes, seasonings, and coffee whiteners. However, amorphous silica has multifunctional properties that would allow it to act as a viscosity control agent, emulsion stabilizer, suspension and dispersion agent, desiccant, etc. The utilization of silicas in these potential applications, however, has not been undertaken, partially because of the limited knowledge of their physiochemical interactions with other food components and partially due to their controversial status from a toxicological point of view. The main goal of this review is to compile current information on the incorporation of amorphous silicon dioxide as a highly functional and viable additive in the food processing industry as well as to discuss the most recent toxicological investigations of silica in an attempt to present some of the potential food applications and their concomitant toxicological implications. Some of the more significant differences between various silicas and their surface chemistries are presented to elucidate some of their mechanisms of interaction with food components and other biological systems and to aid in the prediction of their rheological or toxicological behavior.
Animals↗
Instability of digoxin in digoxin-amorphous silicon dioxide triturates prepared by solvent deposition and ball milling.
Digoxin underwent hydrolytic degradation to its molecular components when solvent deposited on or ball milled with various commercial grades of amorphous silicon dioxide. The degradation was greater during ball milling than after solvent deposition, and increased with a longer ball milling. By itself digoxin was also degraded by ball milling, but not as much as when a silicon dioxide was present. The extent of the degradation appeared to depend on the acidity, surface area and pore size of the silicon dioxide used. A similar degradative behavior was observed for the related glycoside digitoxin.
Chemistry, Pharmaceutical↗