Characterizing stress in ultrathin silicon wafers

The aim of this letter is to calculate the mechanical grinding induced bow and stress in ultrathin silicon wafers. The reverse leakage current of a p-n junction diode fabricated on a 4 in. silicon wafer was measured for wafers thinned to various thicknesses. A correlation with the residual stress was obtained through band gap narrowing effect. The analytical results were compared with experimental bow measurements using a laser profiler. The bow in 50 mu m thick wafer was found to be less than 2 mm using the current grinding process. (c) 2006 American Institute of Physics. (DOI:10.1063/1.2336212

Thermal diffusivity of nonfractal and fractal nickel nanowires

The potential of using nanometallic wires inside a matrix as new generation of thermal interface material led us to study the thermal diffusivity of nickel nanowires embedded inside porous alumina template. Thermal diffusivity measurements using a laser flash method showed size dependence for nickel nanowires inside nanochannel alumina (NCA) templates having nominal pore diameters of 200, 100, and 20 nm. Nickel nanowires embedded inside these templates showed decreasing diffusivity values of 10.7x10(-6), 8.5x10(-6), and 6.5x10(-6) m(2) s(-1) at 300 K with decreasing wire diameter when deposited at 40 degrees C. Nanowires fabricated at 60 degrees C showed similar decreasing diffusivity with wire diameter, and a further 42%-48% reduction was observed when compared to 40 degrees C samples. The modified effective medium theory (MEMT) was employed to evaluate the experimental thermal diffusivity. Calculations based on MEMT resulted in mean thermal conductivities of 70.7 and 36.2 W m(-1) K(-1) for nickel nanowires fabricated at 40 and 60 degrees C respectively. These values are similar to 20% and 60% lower than the thermal conductivity value of bulk nickel. A strong grain size dependence of thermal diffusivity in the nanowires was observed. It is believed that the decrease in diffusivity in lower temperature wires is associated with defects/dislocations in large single crystals and reduction in wire diameters according to pore diameters of NCA. Whereas in higher temperature wires, the drastic reduction in diffusivity is believed to arise from self-similar fractal morphology composed of nanogranules, close to the dimension of electron mean free path

The Impact of Surfactant Sodium Dodecyl Sulfate on the Microstructure and Thermoelectric Properties of p-type (Sb1-xBix)2Te3 Electrodeposited Films

This work reports on the synthesis of p-type (Sb1-xBix)2Te3 thin films using pulsed electrodeposition with and without the presence of an anionic surfactant, sodium dodecyl sulfate (SDS). The effect of SDS on the morphology of the films was investigated, and it was found that films with SDS in the electrolyte were smooth and denser as compared to the films without SDS. Post-deposition annealing of the films resulted in preferential crystal orientation. The Seebeck coefficient showed an improvement of 49% for the films deposited with SDS, which improved the overall power factor of the films by 143%

Supercapattery based on binder-free Co3 (PO4)2·8H2O multilayer nano/microflakes on nickel foam

A binder-free cobalt phosphate hydrate (Co3(PO4)2·8H2O) multilayer nano/microflake structure is synthesized on nickel foam (NF) via a facile hydrothermal process. Four different concentrations (2.5, 5, 10, and 20 mM) of Co2+ and PO4–3 were used to obtain different mass loading of cobalt phosphate on the nickel foam. The Co3(PO4)2·8H2O modified NF electrode (2.5 mM) shows a maximum specific capacity of 868.3 C g–1 (capacitance of 1578.7 F g–1) at a current density of 5 mA cm–2 and remains as high as 566.3 C g–1 (1029.5 F g–1) at 50 mA cm–2 in 1 M NaOH. A supercapattery assembled using Co3(PO4)2·8H2O/NF as the positive electrode and activated carbon/NF as the negative electrode delivers a gravimetric capacitance of 111.2 F g–1 (volumetric capacitance of 4.44 F cm–3). Furthermore, the device offers a high specific energy of 29.29 Wh kg–1 (energy density of 1.17 mWh cm–3) and a specific power of 4687 W kg–1 (power density of 187.5 mW cm–3)

In vitro evaluation of the sealing ability of three newly developed root canal sealers: A bacterial microleakage study

The purpose of this study was to compare the sealing ability of MTA Fillapex, Apatite Root Canal Sealer and AH26 sealers. The present in vitro study was carried out on 142 extracted single-rooted human mature teeth. The teeth were randomly divided into three experimental groups (n=44) and two control groups (n=5). Three root canal sealers were MTA Fillapex, Apatite Root Canal Sealer and AH26. The teeth in the control groups were either filled with no sealer or made completely impermeable. The root canals were prepared and obturated with gutta-percha and one of the sealers. The teeth were sterilized with ethylene oxide gas prior to the bacterial leakage assessment using Enterococcus faecalis. Leakage was evaluated every 24 hours for 90 days. Data were analyzed with descriptive statistical methods and chi-squared test. If the data were significant, a proper post hoc test was used. Statistical significance was set at P<0.05. The positive control specimens exhibited total bacterial penetration whilst the negative control specimens showed no evidence of bacterial penetration. At the end of the study, the analysis of microleakage with chi-squared test showed no significant differences between the experimental groups (P<0.05). The results of chi-squared test analyzing the pair-wise differences between the groups considering the numerical values for leakage day indicated the lowest leakage with AH26 and the highest with Apatite root sealer. According to the results of the present study, sealing ability of AH26 was significantly higher than that of MTA Fillapex and Apatite Root Canal Sealer

Pseudocapacitance of α-CoMoO4 nanoflakes in non-aqueous electrolyte and its bi-functional electro catalytic activity for methanol oxidation

Nanocrystalline cobalt molybdate (CoMoO4) nanoflakes were grown directly on carbon fibre cloth (CFC) via a simple hydrothermal method without any template or surfactant. A symmetric supercapacitor was fabricated using CoMoO4 nanoflakes/CFC as both negative and positive electrodes. The device has delivered the maximum specific capacitance of 8.3 F g−1 at a constant current density of 1 A g−1 in organic electrolyte. It offers the reasonable energy (2.6 Wh kg−1) and power density (748.8 W kg−1) as comparable to the carbon based symmetric supercapacitors. As a catalyst for methanol oxidation, the CoMoO4 nanoflakes showed high current density (25 mA cm−2) and low onset potential (0.38 V). The impressive bi-functional electrochemical activity of CoMoO4 on CFC is mainly attributed to its porous microstructure, where reasonable electrical conductivity resulted from binder-free and intimate metal oxide/substrate integration

Effect of anti-inflammatory drug (Piroxicam) on the development of fatty streak and biochemical factors in cholesterol-fed rabbits

زمینه و هدف: با توجه به اینکه هنوز علت اصلی مرگ و میر در اکثر نقاط دنیا بیماریهای قلبی- عروقی است، پیشگیری و درمان این بیماریها با توجه به مکانیسم های جدید ارائه شده قابل توجه است. این پروژه با تکیه بر مکانیسم جدید بیماریهای عروقی مبنی بر یک بیماری التهابی در صدد یافتن ترکیبات خاص در پیشگیری از تشکیل و پیشرفت رگه های چربی (fatty streak) در آترواسکلروز بوده است. روش مطالعه: در یک مطالعه مداخله ای 20 خرگوش نر به مدت 14 هفته مورد بررسی قرار گرفتند. خرگوشها بصورت انتخابی در 4 گروه 5 تایی تقسیم شدند و همه این گروهها در ابتدا به مدت2 هفته تحت رژیم پایه قرار گرفتند. سپس، گروه اول تا پایان دوره تحت رژیم استاندارد، گروه دوم علاوه بر رژیم استاندارد، روزانه mg6 پیروکسیکام تزریقی دریافت کردند، گروه سوم تحت رژیم پرکلسترول و گروه چهارم علاوه بر رژیم پرکلسترول روزانه mg6 پیروکسیـــکام تزریقی دریافت کردند. در طـــی این دوره در دو نوبت (بعد از رژیم پایه و در پایـــان دوره) از خرگوشها جهت آزمایشات بیوشیمیـــایی مختلف از جمله کلسترول تام، لیپوپروتئین با دانسیته پائین (LDL)، لیپوپروتئین با دانسیتـــه بالا (HDL)، مالون دی آلدئید، قند خون ناشتا (FBS)، CRP (C-Reactive protein) کمی، تری گلیسیرید و ظرفیت آنتی اکسیدان خونگیری به عمل آمد. در پایان پس از اتوپسی، نمونه آئورت و کرونرهای راست و چپ مورد بررسی پاتولوژی قرار گرفت. نتایج: رژیم پرکلسترول در مقایسه با رژیم استاندارد باعث ایجاد fatty streakدر عروق کرونر و آئورت شد (0001/0

Targeted Fluoromagnetic Nanoparticles for Imaging of Breast Cancer MCF-7 Cells

Purpose: To achieve simultaneous imaging and therapy potentials, targeted fluoromagnetic nanoparticles were synthesized and examined in human breast cancer MCF-7 cells. Methods: Fe3O4 nanoparticles (NPs) were synthesized through thermal decomposition of Fe(acac)3. Then, magnetic nanoparticles (MNPs) modified by dopamine-poly ethylene glycol (PEG)-NH2; finally, half equivalent fluorescein isothiocyanate (FITC) and half equivalent folic acid were conjugated to one equivalent of it. The presence of Fe3O4-DPA-PEG-FA/FITC in the folate receptor (FR) positive MCF-7 cells was determined via fluorescent microscopy to monitor the cellular interaction of MNPs. Results: FT-IR spectra of final compound confirmed existence of fluorescein on folic acid grafted MNPs. The Fe3O4-DPA-PEG-FA/FITC NPs, which displayed a size rang about 30-35 nm using scanning electron microscopy (SEM) and transmission electron microscopy (TEM), were able to actively recognize the FR-positive MCF-7 cells, but not the FR-negative A549 cells. Conclusion: The uniform nano-sized Fe3O4-DPA-PEG-FA/FITC NPs displayed great potential as theranostics and can be used for targeted imaging of various tumors that overexpress FR