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Conventional flat plate-shaped brushite, dicalcium phosphate dihydrate, CaHPO 4 ·2H 2 O), produced by reacting Ca-chloride and alkali phosphate salt solutions, were found to undergo a maturation process (changing their Ca/P molar ratio from 0.8 to the theoretical value of 1) similar to those seen in biological apatites. Water lily (WL)-shaped brushite crystals were produced in nonstirred aqueous solutions at room temperature in 24 h, by using precipitated calcite and NH 4 H 2 PO 4 as the starting chemicals. The hydrothermal transformation of WLtype brushite into octacalcium phosphate (OCP) or Ca-deficient hydroxyapatite (CDHA) was tested at 37°C by using four different biomineralization solutions, including Tris-buffered SBF (synthetic body fluid) and sodium lactate-buffered SBF solutions. All four solutions used in this study consumed the starting brushite in 1 week and caused transformation into a biphasic mixture of nanocrystalline OCP and CDHA of high surface area. WL-type brushite crystals when synthesized in the presence of small amounts of Zn 2+ ions resulted in the formation of, for the first time, spherical micro-granules of brushite.

The simultaneous one-dimensional Knudsen diffusion and chemical reaction description of low-pressure chemical vapor deposition in features on patterned surfaces is used to show that a substantial decrease in processing time can be achieved for a given step coverage by varying the deposition rate in a prescribed manner during the process. For constantrate CVD (CRCVD) processes, the rate is dictated by the rate required to obtain a good step coverage at the end of the process when the instantaneous aspect ratio becomes very large. The use of a programmed-rate CVD (PRCVD) process allows a larger average deposition rate, since the initial rate is much higher than the rate required to maintain good step coverage close to feature closure. The PRCVD concept is demonstrated for the thermally activated deposition of silicon dioxide from tetraethylorthosilicate (TEOS) by decreasing the temperature during deposition. The two-step process path chosen for our calculations is not optimal; however, it can be easily implemented and modified. The time saved depends on the reaction kinetics, but approaches 50% of the constant rate process time for step coverages above 95%.

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Two models used for predicting film profile evolution during low pressure chemical vapor deposition in features on patterned substrates are compared; (i) a ballistic transport-reaction model (BTRM) in which transport between surfaces in a feature is "line of sight" and (it) a diffusion-reaction model (DRM) in which gas-phase transport is expressed in terms of concentration gradients and Knudsen diffusion. In order to compare the qualitative and quantitative predictions of the two models we use blanket tungsten deposition by the hydrogen reduction of tungsten hexafluoride in long (two-dimensional) rectangular trenches as an example. The two models are based on the same underlying assumptions: however, they differ in their treatment of molecular transport in features. For both models, film deposition occurs through heterogeneous gas-solid reactions, and profile evolution is two dimensional. The BTRM is formulated in terms of three-dimensional fluxes to the evolving film surface. These fluxes are expressed in terms of fluxes from all other points on the surface of the feature and from the source volume and are therefore "nonlocal." In the DRM, fluxes to the local surface are expressed in terms of local gas-phase concentrations. Because of the assumptions used to compute Knudsen diffusivity in the DRM, the transport occurs in one dimension. "Rules of thumb" relating qualitative changes in film conformality to changes in process conditions, derived using the governing equations of the two models, are the same and agree well with observed trends. Using a "relative reactant depletion criterion," both models predict the same ratio of partial pressures of reactants which maximizes film conformality. Quantitative step coverage predictions obtained from the BTRM simulations are consistently higher than those of the DRM.Process modeling is gaining importance in the microelectronics industry and has assumed multiple roles in process development, modification, and optimization. For example, low pressure chemical vapor deposited (LPCVD) process models are used to predict film conformality 1-9 as well as to develop novel process protocols to increase film cortformality and wafer throughput. 3,g Typical LPCVD systems are characterized by the presence of free molecular or Knudsen flow (high Knudsen numbers) within micronscale features and heterogeneous gas-solid reactions which lead to film growth. In recent years, two different physically based models of LPCVD processes have achieved reasonable success: (i) a "continuum-like" diffusion-reaction model (DRM), 14 and (it) a particle-based modified line-ofsight or ballistic transport-reaction model (BTRM). 44The BTRM has the advantage that its equations are derived from a strong fundamental basis; however, its application is restricted to low pressure processes. The advantage with the DRM is that it can be modified to simulate CVD processes at higher pressures (lower Knudsen numbers), in addition to the low pressure processes. Limitations of the DRM lie mainly in its treatment of mo...

Simulation of inductors has been a very popular area of analog circuit research and the alternative choice for realizing inductor-based circuits in integrated circuits. In this paper, lossless, grounded and floating inductor topologies using current-controlled-current-feedback amplifier (CC-CFA) with single grounded capacitor are presented. The proposed topologies can be tuned electronically by changing the biasing current of the CC-CFA. Two topologies for grounded inductor simulator employ two CC-CFA and one grounded capacitor. One topology for floating inductor simulator employs three CC-CFA and one grounded capacitor. The performance of the grounded and floating inductor simulators are demonstrated on resonant circuits. The theoretical analysis is verified by PSPICE simulation results.

Patients presenting with idiopathic cytopenia with non-diagnostic marrow morphology and a normal karyotype pose a diagnostic and therapeutic challenge. Additional diagnostic information from mutation analysis could provide important clinical insights. However, one has to be cautious during such diagnostic interpretations in view of the recent documentation of clonal somatic mutations in healthy elder individuals. Whether to regard clonality synonymous with malignant proliferation or a manifestation of ageing process is to be judged carefully. Areas covered: The review covers defining criteria and diagnostic work up for Idiopathic cytopenia of undetermined significance (ICUS), Clonal cytopenia of undetermined significance (CCUS), Clonal hematopoiesis of indeterminate potential (CHIP). It also presents the results from previous reports on this subject. In addition the evolution and potential impact of these entities is discussed. Expert commentary: Current evidence does not support the use of somatic mutations as presumptive evidence of myelodysplastic syndrome (MDS). Including CCUS under the category of MDS requires further insight on natural disease course. Longitudinal follow up study on ICUS, CCUS, CHIP may eventually identify the pathological significance of the clonal mutations. An absence of mutation however may still be useful as good predictor of not having MDS.

Collagen sponges seeded with fibroblasts have been used as a soft tissue substitute in wound healing applications. This biomaterial is a good in vitro analog of a connective tissue. Therefore, analysis of the properties of this material may be useful for theoretically modeling soft tissues. Stress-strain curves for such cell-seeded collagen sponges were measured to determine composite stiffness and ultimate tensile strength. Theoretical modeling was done by defining a particle-reinforced matrix using the composite sphere model. A system of uniaxially oriented fibers was then introduced to this equivalent homogeneous media and material properties were determined using the composite cylinder model. Geometric averaging was performed to yield the stiffness and Poissons' ratio for a composite with randomly oriented fibers. Inputs to the model were constituent material properties, cell volume fraction, and fiber volume fraction. From theoretical results, material properties of soft tissues and their substitutes depend on fiber mechanical properties and volume fraction and not cellular mechanical properties and volume fraction. Therefore, the increase in experimentally observed composite stiffness with increased cell number was due to deposition of newly synthesized stiffer collagen fibers, and not due to the physical presence of cells themselves.