Pengelupasan grafit untuk mengkomersilkan teknologi grafin

Kertas ini mengkaji teknologi pengelupasan untuk menghasilkan grafin, grafin oksida (GO) dan grafin oksida terturun (rGO). Empat teknologi pengelupasan yang utama dikenal pasti dalam tinjauan ini iaitu pengelupasan mekanik, pengelupasan cecair, interkalasi-pengelupasan dan pengoksidaan-pengelupasan-penurunan. Setiap teknologi ini dibincangkan daripada segi kualiti grafin, grafit nanoplat, GO dan rGO yang dihasilkan dan langkah utama proses termasuk bahan kimia yang digunakan. Kami juga membuat satu kajian kemudah-capaian dan analisis sensitiviti untuk menubuhkan satu kilang penghasilan grafin yang berasaskan teknologi pengelupasan, saiz pasaran grafin dan bahan mentahnya iaitu grafit. Berdasarkan kitar gemburan Gartner, teknologi dan produk yang berasaskan grafin terletak di tiga lokasi iaitu lembah kekecewaan, cerun pencerahan dan dataran tinggi produktiviti

XPS study of sulfur and phosphorus compounds with different oxidation states

In this report, we demonstrate that continuous improvement in XPS instruments and the calibration standards as well as analysis with standard component-fitting procedures can be used to determine the binding energies of compounds containing phosphorus and sulfur of different oxidation states with higher confidence. Based on such improved XPS analyses, the binding energies (BEs) of S2p signals for sulfur of increasing oxidation state are determined to be 166-167.5 eV for S=O in dimethyl sulfoxide, 168.1 eV for S=O2 in polysulfone, 168.4 eV for SO3 in polystyrene sulfonate and 168.8 eV for SO4 in chondroitin sulfate. The BEs of P2p signals show the following values: 132.9 eV for PO3 in triisopropyl phosphite, 133.3 eV for PO4 in glycerol phosphate, 133.5 eV for PO4 in sodium tripolyphosphate and 134.0 eV for PO4 in sodium hexametaphosphate. These results showed that there are only small increases in the binding energy when additional oxygen atoms are added to the S-O chemical group. A similar result is obtained when the fourth oxygen or poly-phosphate environment is added to the phosphorus compound. These BE values are useful to researchers involved in identifying oxidation states of phosphorus and sulfur atoms commonly observed on modified surfaces and interfaces found in applications such as biomaterials, super-capacitors and catalysis

Peranti suis nanoelektromekanikal (NEM) berunsurkan grafin dan tiub nano karbon (CNT)

Suis nanoelektromekanikal (NEM) mempunyai persamaan dengan suis konvensional semikonduktor apabila digunakan sebagai transistor dan penderia walaupun prinsip operasinya berbeza. Perbezaan prinsip operasi suis ini memberikan kelebihan kepada suis NEM untuk beroperasi dalam persekitaran yang melampau manakala suis konvensional semikonduktor mempunyai kelebihan daripada segi infrastruktur fabrikasi yang canggih. Dalam kertas ini, kami mengulas kemajuan terbaru dan potensi teknologi NEM dalam aplikasi pensuisan berdasarkan bahan berasaskan karbon seperti CNT dan grafin. Kemajuan reka bentuk geometri suis NEM seperti struktur rusuk berlubang, mempunyai kelebihan daripada segi voltan operasi peranti yang rendah, turut dibincangkan dalam kertas ini. Berdasarkan Kitaran Gemburan Gartner, teknologi, proses dan produk untuk suis NEM atau hibrid NEM-CMOS berada di takuk berbeza iaitu di jurang ilusi, cerun pencerahan dan dataran tinggi produktiviti. Kemudian, reka bentuk geometri suis NEM berasaskan bahan-bahan ini diulas dengan lengkap berdasarkan kajian kepustakaan terbaru. Kami mengenal pasti cabaran yang terlibat dalam proses fabrikasi suis NEM berasaskan CNT dan grafin seperti kebocoran get dan proses litografi yang mencabar. Kesimpulannya, kami meringkaskan kertas kajian ini kepada beberapa sudut perspektif, pandangan dan peluang pada masa depan dalam teknologi suis NEM

Diffusion Mechanism Of Silver Particles In Polymer Binder For Die Attach Interconnect Technology

Sintered Ag has gained strong interest as an important alternative material for interconnect technology in wide bandgap (WBG) semiconductor industries specifically for high thermal dissipations and high-speed applications. This material typically consists of metallic particles bounded by polymer binder expected to diffuse at the temperature much lower than its melting temperature. This paper studies the diffusion mechanism between Ag particles and its microstructural change over different heat treatment temperature that leads to the understanding on the formation of bonding particles into a predominantly solid Ag network as a conducting path for the interconnect systems. The surface diffusion initiated between Ag particles as they come into intimate contact through the formation of necking. Further atomic movement and diffusion between the particles neck resulting in volume expansion, necking growth as well as the transformation of the particle shape from spherical into an elongated structure. This results in the formation of a long chain of connecting particles, which transform the Ag particles into a solid Ag network

Prolonged Application of High Fluid Shear to Chondrocytes Recapitulates Gene Expression Profiles Associated with Osteoarthritis

BACKGROUND: Excessive mechanical loading of articular cartilage producing hydrostatic stress, tensile strain and fluid flow leads to irreversible cartilage erosion and osteoarthritic (OA) disease. Since application of high fluid shear to chondrocytes recapitulates some of the earmarks of OA, we aimed to screen the gene expression profiles of shear-activated chondrocytes and assess potential similarities with OA chondrocytes. METHODOLOGY/PRINCIPAL FINDINGS: Using a cDNA microarray technology, we screened the differentially-regulated genes in human T/C-28a2 chondrocytes subjected to high fluid shear (20 dyn/cm(2)) for 48 h and 72 h relative to static controls. Confirmation of the expression patterns of select genes was obtained by qRT-PCR. Using significance analysis of microarrays with a 5% false discovery rate, 71 and 60 non-redundant transcripts were identified to be ≥2-fold up-regulated and ≤0.6-fold down-regulated, respectively, in sheared chondrocytes. Published data sets indicate that 42 of these genes, which are related to extracellular matrix/degradation, cell proliferation/differentiation, inflammation and cell survival/death, are differentially-regulated in OA chondrocytes. In view of the pivotal role of cyclooxygenase-2 (COX-2) in the pathogenesis and/or progression of OA in vivo and regulation of shear-induced inflammation and apoptosis in vitro, we identified a collection of genes that are either up- or down-regulated by shear-induced COX-2. COX-2 and L-prostaglandin D synthase (L-PGDS) induce reactive oxygen species production, and negatively regulate genes of the histone and cell cycle families, which may play a critical role in chondrocyte death. CONCLUSIONS/SIGNIFICANCE: Prolonged application of high fluid shear stress to chondrocytes recapitulates gene expression profiles associated with osteoarthritis. Our data suggest a potential link between exposure of chondrocytes/cartilage to abnormal mechanical loading and the pathogenesis/progression of OA

Photochemically modified diamond-like carbon surfaces for neural interfaces

Diamond-like carbon (DLC) was modified using a UV functionalization method to introduce surface-bound amine and aldehyde groups. The functionalization process rendered the DLC more hydrophilic and significantly increased the viability of neurons seeded to the surface. The amine functionalized DLC promoted adhesion of neurons and fostered neurite outgrowth to a degree indistinguishable from positive control substrates (glass coated with poly-L-lysine). The aldehyde-functionalized surfaces performed comparably to the amine functionalized surfaces and both additionally supported the adhesion and growth of primary rat Schwann cells. DLC has many properties that are desirable in biomaterials. With the UV functionalization method demonstrated here it may be possible to harness these properties for the development of implantable devices to interface with the nervous system

Pubertal high fat diet: effects on mammary cancer development

INTRODUCTION: Epidemiological studies linking dietary fat intake and obesity to breast cancer risk have produced inconsistent results. This may be due to the difficulty of dissociating fat intake from obesity, and/or the lack of defined periods of exposure in these studies. The pubertal mammary gland is highly sensitive to cancer-causing agents. We assessed how high fat diet (HFD) affects inflammation, proliferative, and developmental events in the pubertal gland, since dysregulation of these can promote mammary tumorigenesis. To test the effect of HFD initiated during puberty on tumorigenesis, we utilized BALB/c mice, for which HFD neither induces obesity nor metabolic syndrome, allowing dissociation of HFD effects from other conditions associated with HFD. METHODS: Pubertal BALB/c mice were fed a low fat diet (12% kcal fat) or a HFD (60% kcal fat), and subjected to carcinogen 7,12-dimethylbenz[a]anthracene (DMBA)-induced tumorigenesis. RESULTS: HFD elevated mammary gland expression of inflammatory and growth factor genes at 3 and 4 weeks of diet. Receptor activator of nuclear factor kappa-B ligand (RANKL), robustly induced at 4 weeks, has direct mitogenic activity in mammary epithelial cells and, as a potent inducer of NF-κB activity, may induce inflammatory genes. Three weeks of HFD induced a transient influx of eosinophils into the mammary gland, consistent with elevated inflammatory factors. At 10 weeks, prior to the appearance of palpable tumors, there were increased numbers of abnormal mammary epithelial lesions, enhanced cellular proliferation, increased growth factors, chemokines associated with immune-suppressive regulatory T cells, increased vascularization, and elevated M2 macrophages. HFD dramatically reduced tumor latency. Early developing tumors were more proliferative and were associated with increased levels of tumor-related growth factors, including increased plasma levels of HGF in tumor-bearing animals. Early HFD tumors also had increased vascularization, and more intra-tumor and stromal M2 macrophages. CONCLUSIONS: Taken together in this non-obesogenic context, HFD promotion of inflammatory processes, as well as local and systemically increased growth factor expression, are likely responsible for the enhanced tumorigenesis. It is noteworthy that although DMBA mutagenesis is virtually random in its targeting of genes in tumorigenesis, the short latency tumors arising in animals on HFD showed a unique gene expression profile, highlighting the potent overarching influence of HFD

The primary headaches: genetics, epigenetics and a behavioural genetic model

The primary headaches, migraine with (MA) and without aura (MO) and cluster headache, all carry a substantial genetic liability. Familial hemiplegic migraine (FHM), an autosomal dominant mendelian disorder classified as a subtype of MA, is due to mutations in genes encoding neural channel subunits. MA/MO are considered multifactorial genetic disorders, and FHM has been proposed as a model for migraine aetiology. However, a review of the genetic studies suggests that the FHM genes are not involved in the typical migraines and that FHM should be considered as a syndromic migraine rather than a subtype of MA. Adopting the concept of syndromic migraine could be useful in understanding migraine pathogenesis. We hypothesise that epigenetic mechanisms play an important role in headache pathogenesis. A behavioural model is proposed, whereby the primary headaches are construed as behaviours, not symptoms, evolutionarily conserved for their adaptive value and engendered out of a genetic repertoire by a network of pattern generators present in the brain and signalling homeostatic imbalance. This behavioural model could be incorporated into migraine genetic research

One step ATRP initiator immobilization on surfaces leading to gradient-grafted polymer brushes

Published: April 30, 2014A method is described that allows potentially any surface to be functionalized covalently with atom transfer radical polymerization (ATRP) initiators derived from ethyl-2-bromoisobutyrl bromide in a single step. In addition, the initiator surface density was variable and tunable such that the thickness of polymer chain grafted from the surface varied greatly on the surfaces providing examples, across the surface of a substrate, of increased chain stretching due to the entropic nature of crowded polymer chains leading toward polymer brushes. An initiator gradient of increasing surface density was deposited by plasma copolymerization of an ATRP initiator (ethyl 2-bromoisobutyrate) and a non-ATRP reactive diluent molecule (ethanol). The deposited plasma polymer retained its chemical ability to surface-initiate polymerization reactions as exemplified by N,N'-dimethyl acrylamide and poly(ethylene glycol) methyl ether methacrylate polymerizations, illustrating linear and bottle-brush-like chains, respectively. A large variation in graft thickness was observed from the low to high chain-density side suggesting that chains were forced to stretch away from the surface interface--a consequence of entropic effects resulting from increased surface crowding. The tert-butyl bromide group of ethyl 2-bromoisobutyrate is a commonly used initiator in ATRP, so a method for covalent linkage to any substrate in a single step desirably simplifies the multistep surface activation procedures currently used.Bryan R. Coad, Katie E. Styan, and Laurence Meaghe