Exponential lower bounds for depth three Boolean circuits

We consider the class of unbounded fan-in depth three Boolean circuits, for which the bottom fan-in is limited by k and the top gate is an OR. It is known that the smallest such circuit computing the parity function has gates (for k = O(n ^1/2)) for some , and this was the best lower bound known for explicit (P-time computable) functions. In this paper, for k = 2, we exhibit functions in uniform NC ¹ that require size depth 3 circuits. The main tool is a theorem that shows that any circuit on n variables that accepts a inputs and has size s must be constant on a projection (subset defined by equations of the form x _i = 0, x _i = 1, x _i = x _j or x _i = ) of dimension at least log(a/s)log n. Received: April 1, 1997.     

Effects of Potato Fiber and Potato‐Resistant Starch on Biomarkers of Colonic Health in Rats Fed Diets Containing Red Meat

Abstract: The effects of red meat consumption with and without fermentable carbohydrates on indices of large bowel health in rats were examined. Sprague‐Dawley rats were fed cellulose, potato fiber, or potato‐resistant starch diets containing 12% casein for 2 wk, then similar diets containing 25% cooked beef for 6 wk. After week 8, cecal and colonic microbiota composition, fermentation end‐products, colon structure, and colonocyte DNA damage were analyzed. Rats fed potato fiber had lower Bacteroides‐Prevotella‐Porphyromonas group compared to other diet groups. Colonic Bifidobacterium spp. and/or Lactobacillus spp. were higher in potato fiber and potato‐resistant starch diets than in the cellulose diet. Beneficial changes were observed in short‐chain fatty acid concentrations (acetic, butyric, and propionic acids) in rats fed potato fiber compared with rats fed cellulose. Phenol and p‐cresol concentrations were lower in the cecum and colon of rats fed potato fiber. An increase in goblet cells per crypt and longer crypts were found in the colon of rats fed potato fiber and potato‐resistant starch diets. Fermentable carbohydrates had no effect on colonic DNA damage. Dietary combinations of red meat with potato fiber or potato‐resistant starch have distinctive effects in the large bowel. Future studies are essential to examine the efficacy of different types of nondigestible carbohydrates in maintaining colonic health during long‐term consumption of high‐protein diets. Practical Application: Improved understanding of interactions between the food consumed and gut microbiota provides knowledge needed to make healthier food choices for large bowel health. The impact of red meat on large bowel health may be ameliorated by consuming with fermentable dietary fiber, a colonic energy source that produces less harmful by‐products than the microbial breakdown of colonic protein for energy. Developing functional red meat products with fermentable dietary fiber could be one way to promote a healthy and balanced macronutrient diet.     

The choice of an input-output table embedded in regional econometric input-output models

In this paper, we investigate the role of input-output data sources in regional econometric input-output models. While there has been a great deal of experimentation focused on the accuracy of alternative methods for estimating regional inputoutput coefficients, little attention has been directed to the role of accuracy when the input-output system is nested within a broader accounting framework. The issues of accuracy were considered in two contexts, forecasting and impact analysis focusing on a model developed for the Chicago region. We experimented with three input-output data sources: observed regional data, national input-output, and randomly generated inputoutput coefficients. The effects of different sources of input-output data on regional econometric input-output models revealed that there are significant differences in results obtained in both forecast and impact analyses. The adjustment processes inherent in the econometric input-output system did not mask the differences imbedded in input-output tables derived from different data sources. Since applications of these types of models involve both impact and forecasting exercises, there should be strong motivation for basing the syste on the most accurate set of input-output accounts.     

Effect of ex situ Post-annealing Treatments on Sr2FeMoO6 Thin Films

Magnetoresistive Sr₂FeMoO₆ thin films were grown by pulsed laser deposition at optimized deposition atmosphere and temperature. Films were then ex?situ post-annealed in different atmospheres and by vacuum annealing at temperatures between 500?°C and 1100?°C. Ar and air annealed samples were destroyed by ex?situ post-annealing treatment, due to formation and dominance of SrMoO₄ impurity phase. X-ray diffraction showed no impurities and full texturation of vacuum and ArH₂ (5%) annealed samples. Those samples showed also similar magnetic and magnetoresistive behavior like as-deposited sample. Neither magnetic, magnetotransport nor structural properties could be improved by ex?situ post-annealing treatments.     

Combination of Ag Substrate Decoration with Introduction of?BaZrO3 Nano-Inclusions for?Enhancing Critical Current Density of?YBa2Cu3O7 Films

The combination of two methods: Ag substrate decoration and introduction of BZO nano-inclusions has been used in a pulsed laser deposition (PLD) method to increase the critical density (J _c ) of YBCO films. The films were deposited on single crystal SrTiO₃ (STO) substrates decorated with various architecture of Ag nano-dots. We have studied the diameter and density of Ag nano-dots and their influence on J _c of BZO-added YBCO films. We found that 15 laser pulses on the Ag target gives an optimum result in increasing J _c in comparison with BZO-doped YBCO films of the same thickness in self-field and low applied magnetic fields. A higher number of laser pulses on the Ag target led to increasing critical current density in high applied magnetic fields only (above 2 T). We have studied films of the thickness from 0.4 ??m to 3.8 ??m and found that the highest J _c at all applied fields investigated is achieved for a 1.2 ??m thick film. The transmission electron microscopy clearly shows BZO nano-rods that provide strong c-axis pinning centres in the films.     

Controlling chaotic dynamics of periodically forced spheroids in simple shear flow: Results for an example of a potential application

Recently, we studied the technologically important problem of periodically forced spheroids in simple shear flow and demonstrated the existence of chaotic parametric regimes. Our results indicated a strong dependence of the solutions obtained on the aspect ratio of the spheroids, which can be used to separate particles from a suspension. In this paper we demonstrate that controlling the chaotic dynamics of periodically forced particles by a suitably engineered novel control technique, which needs little information about the system and is easy to implement, leads to the possibility of better separation. Utilizing the flexibility of controlling chaotic dynamics in a desired orbit irrespective of initial state, we show that it is theoretically possible to separate particles much more efficiently than otherwise from a suspension of particles having different shapes but similar sizes especially for particles of aspect ratior _e >1.0. The strong dependence of the controlled orbit on the aspect ratio of the particles may have many applications such as in the development of computer-controlled intelligent rheology. The results suggest that control of chaos as discussed in this work may also have many applications. A list of symbols is given at the end of the paper     

Biorthogonally accessed three-dimensional two-photon memory for relational database operations

Memory bandwidth is a bottleneck for very large database machines. Parallel-access three-dimensional two-photon memories have the potential of achieving enormous throughput (>100 Gbit/s) and capacity (1 Tbit/cm(3)) [Appl. Opt. 29, 2058 (1990)] and, consequently, are well suited for this application. Our analysis shows that some operations can be completed more than 2 orders of magnitude faster with this type of memory than with a system based on serial-access storage. These particular memories have a further feature of being accessible in orthogonal directions. We show that this property, used in conjunction with a three-dimensional data-organization scheme designed for this approach, leads to improved performance by permitting the user a choice of accessing strategies for a given operation.