Surface-enhanced Raman scattering study of polymer on metals. III. Chemisorbed polybenzimidazole and its corrosion-inhibiting properties at high temperature

Chemisorption of polybenzimidazole on silver and copper etched with nitric acid has been observed by surface-enhanced Raman scattering (SERS). The polymer is found to react chemically with silver, forming a complexed film on the surface. The SERS spectra show that polybenzimidazole film inhibits oxidation of the metal at high temperature, unlike chemisorbed benzimidazole, benzotriazole, and poly(4-vinyl pyridine). © 1992 John Wiley & Sons, Inc.     

Cover Picture: Toward Large‐Scale Alignment of Electrohydrodynamic Patterning of Thin Polymer Films (Adv. Funct. Mater. 15/2006)

By integrating lithography and self‐assembly via electrohydrodynamic instabilities, Russel and co‐workers are able to guide initially flat polymer films to evolve into periodic arrays of pillars over regions much greater in extent than their natural domain sizes, as detailed on p. 1992. Novel structures that involve a combination of linear ridges and pillars are also produced, mainly as as result of the dynamic merging among preformed pillars. To pattern thin polymer films via electrohydrodynamic instabilities, we design and utilize two different kinds of mask patterns to guide pillars into alignment over regions much greater in extent than their natural domain sizes. First, narrow protruding ridges that intersect to form regular patterns on the mask trigger the growth of pillars beneath. Later, square and triangular packings of pillars develop in the regions enclosed by those ridges, preserving the registry from one domain to the next over a much larger area than within individual domains in unpatterned portions of the mask. Second, small square protrusions that are prealigned into a large regular array on the mask guide the formation of square packings of pillars in domains that conform to the mask, forming a large array of pillars. Novel structures involving a combination of linear ridges and pillars are also produced mainly due to the dynamic merging among preformed pillars. Finally, we find vertex symmetry of the mask pattern is necessary for generating and preserving ordered patterns on the polymer film.     

Caged ATP-fuel for bionanodevices

Micro- and nanodevices require the controlled delivery of energy to power a variety of processes. The current paradigm of connecting a miniaturized device to a set of macroscopic auxiliary devices, such as power supplies or pumps, for the delivery of electrical and mechanical energy needs to be replaced to enable the design of stand-alone integrated bionanodevices with applications in remote biosensing or nanomedicine. Biological nanomachines, such as the motor protein kinesin, can efficiently convert energy stored in chemical compounds, in particular adenosine 5'-triphosphate (ATP), into mechanical work. This ability is an attractive feature of hybrid devices powered by biomolecular motors, since it removes the need for the storage and conversion of electrical energy. The consequences are a simplified fabrication process and packaging, leading to higher yields and lower costs, and the broadening of the applications, which can now include field-deployable nanodevices. Here, the potential of caged ATP as fuel for such engineering applications is discussed. Caged ATP can be stored in the buffer solution of a bionanodevice, "uncaged" by UV light, and utilized as fuel by many enzymes to catalyze chemical changes or power active transport. We demonstrate that DMNPE-caged ATP can be stored in sufficient amounts in a typical device and that the activation can be triggered with a UV lamp or even sunlight.     

Bulk growth of Hg0.8Cd0.2Te single crystals by a combined CVT-seeding technique

The growth of high quality Hg_0.8Cd_0.2Te bulk single crystals by CVT, combined with an in-situ seeding technique, is reported here for the first time. For this purpose, a temperature difference of 590° → 540° C with a gradient of 40°-50° C/cm at the solid-vapor interface, and about 0.1 atm of HgI₂ as a transport agent, were employed. The bulk crystals have the expected stoichiometry and compositional homogeneity. Etch pit densities of 10⁴-10⁵ cm⁻² on the (111) face and hitherto unreported etch pits on the (100) face were observed in this work. Possible origins of the sub-grain structure are discussed.     

A novel SAL-PINSCH quantum-well laser structure for a pinched beamdivergence

Summary form only given. An edge-emitting strained AlGaAs/InGaAs/GaAs quantum-well laser structure is reported. It has a periodic index separate confinement heterostructure (PINSCH) optical confinement layers for a small beam divergence and high output power. Preliminary measurements of AR/HR-coated self-aligned ridge waveguide lasers show a CW output power of up to 350 mW and a 20° transverse beam divergence at a 980-nm lasing wavelength. This low beam divergence results in a high coupling efficiency of 51% into single-mode fibers. The expanded optical field in PINSCH confinement layers significantly pinches the transverse beam divergence and increases the maximum output power     

DISTRIBUTION OF THE（0，∞）ACCUMULATIVE LINES OF MEROMORPHIC FUNCTIONS

Suppose that f(z)is a meromorphic function of order λ（0<λ<+∞）and of lower order μ in the plane.Let ρ be a positive number such that μ≤ρ≤λ.(1)If f^(l)(z)(0≤l<+∞）has p(1≤p<+∞）finite nonzero deficient valnes αi(i=1,…，p)with deficiencies δ（αi,f^(l)),then f(z)has a (0,∞）accumulative line of order ≥ρin any angular domain whose vertex is at the origin and whose magnitude is larger than max(π/ρ，2π-4/ρ ∑i=1^p arcsin √δ（αi,f^(l))/2).(2)If f(z) has only p(0<p<+∞）（0,∞）,accumulative lines of order≥ρ：arg z=θk(0≤θ1<θ2<…<θp<2π，θp+1=θ1+2π）,then λ≤π/ω，where ω=min I≤k≤p(θk+1-θk),provided that f^(l)(z)(0≤l<+∞）has a finite nonzero deficient value.     

离子束引起的在Al／Cr双层薄膜界面处的原子混合

用600keV的Kr~ 离子轰击Al/Cr双层薄膜样品进行界面原子反应及相互混合的研究。实验样品是在单晶硅上蒸镀约500nm厚的铝膜,相继再蒸上所需厚度的铬膜而制成的。轰击剂量为2.0×10~(15)-2.5×10~(16)Kr~ /cm~2。用2.0MeVa粒子对轰击前后的样品进行了卢瑟福背散射(RBS)分析,发现界面处有明显的原子混合存在;当轰击剂量≥1.0×10~(16)Kr~ /cm~2时,RBS谱出现有明显的坪台,经拟合计算和x射线衍射(XRD)测量证实确有化合物Al_(13)Cr_2存在;还分别得到了原子混合量及混合效率与轰击剂量的关系;最后对界面处的原子混合机制进行了讨论。     

Non-quasi-static models including all injection levels and DC, AC,and transient emitter crowding in bipolar transistors

Two-dimensional equivalent-circuit models for bipolar junction transistors are systematically derived by solving the continuity equations for DC, AC, and transient excitations. These models take into account carrier propagation delay, all injection levels, as well as exponential doping profiles. They include analytically DC, AC, and transient emitter crowding in a more detailed and accurate manner than previously available. Extensions of the models to accommodate arbitrarily doped and heavily doped quasi-neutral layers and to include energy-gap narrowing due to the electron-hole plasma present at high current density are described. The analysis leads to compact large- and small-signal equivalent-circuit lumped models, suitable for use in circuit simulators such as SPICE. The analytical solutions obtained reveal the two-dimensional distribution of the current and carrier densities in the intrinsic base layer and the onset of emitter crowding. They also provide information for the extraction of the intrinsic base resistance. Several assumptions made in the derivations are assessed by the computer program PISCES. The methods presented apply to both homojunction and heterojunction bipolar transistors     

激光对生产β-胡萝卜素的藻种——盐生杜氏藻(Dunaliella salina)诱变的研究

用激光(335nm,0.014MW/mm~2)对产生6-胡萝卜素的盐生杜氏藻(Dunaliella Salina)进行了诱变研究,藻的存活率为90％。诱导后筛选到三个盐生杜氏藻的品系。生长速度较原藻最高增加20％,长度增加7.5％,萨-胡萝卜素生产能力为0.48mg·100ml~(-1)天~-1),比原藻增加19％。     

A generalized Adadorov theory for anisotropic thin-walled beams

This paper presents a generalized Adadorov theory for anisotropic thin—walled beams. The theory takes account of the shear strain of the middle surface, which exerts a significant influence on the anisotropic thin-walled beams. A new approach is established to solve the governing equations, which have the same form for both open and closed section beams. The numerical examples show that the effects of the shear strain cannot be neglected for this class of beams.This work was part of research project supported by the National Natural Science Foundation of China