Characteristics of mammary mitochondria in lines of mice genetically divergent for milk production

The purpose of this study was to determine the relationship of mitochondrial proliferation and ATP production to milk production in two lines of mice that were genetically divergent for milk production. Milk production differed between high production and low production lines by .8 phenotypic standard deviations as determined by cross-fostered litter weight gain from 1 to 12 d postpartum. Mammary weight, mammary total DNA, and RNA:DNA ratio were greater in glands of high line mice. Mammary DNA and protein, expressed per gram mammary tissue, were similar between lines. Mammary mitochondrial mass per gland differed after six generations of divergent selection. Rates of succinate-supported ATP production and ADP:O of isolated mitochondria differed, but the rate of pyruvate-supported ATP production did not differ between lines. Differences between selection lines in mitochondrial mass and in the efficiency of succinate use for support of ATP production were probable consequences of selection for divergent milk production.     

Constructing free-energy approximations and generalized belief propagation algorithms

Important inference problems in statistical physics, computer vision, error-correcting coding theory, and artificial intelligence can all be reformulated as the computation of marginal probabilities on factor graphs. The belief propagation (BP) algorithm is an efficient way to solve these problems that is exact when the factor graph is a tree, but only approximate when the factor graph has cycles. We show that BP fixed points correspond to the stationary points of the Bethe approximation of the free energy for a factor graph. We explain how to obtain region-based free energy approximations that improve the Bethe approximation, and corresponding generalized belief propagation (GBP) algorithms. We emphasize the conditions a free energy approximation must satisfy in order to be a "valid" or "maxent-normal" approximation. We describe the relationship between four different methods that can be used to generate valid approximations: the "Bethe method", the "junction graph method", the "cluster variation method", and the "region graph method". Finally, we explain how to tell whether a region-based approximation, and its corresponding GBP algorithm, is likely to be accurate, and describe empirical results showing that GBP can significantly outperform BP.     

Energetics of Donor‐Doping,Metal Vacancies,and Oxygen‐Loss in A‐Site Rare‐Earth‐Doped BaTiO3

The energetics of La‐doping in BaTiO₃ are reported for both (electronic) donor‐doping with the creation of Ti³⁺ cations and ionic doping with the creation of Ti vacancies. The experiments (for samples prepared in air) and simulations demonstrate that ionic doping is the preferred mechanism for all concentrations of La‐doping. The apparent disagreement with electrical conduction of these ionic doped samples is explained by subsequent oxygen‐loss, which leads to the creation of Ti³⁺ cations. Simulations show that oxygen‐loss is much more favorable in the ionic‐doped system than undoped BaTiO₃ due to the unique local structure created around the defect site. These findings resolve the so‐called “donor‐doping” anomaly in BaTiO₃ and explain the source of semiconductivity in positive temperature coefficient of resistance (PTCR) BaTiO₃ thermistors.     

SIR-C data quality and calibration results

The SIR-C/X-SAR imaging radar took its first flight on the Space Shuttle Endeavour in April 1994 and flew for a second time in October 1994. This multifrequency radar has fully polarimetric capability at L- and C-band, and a single polarization at X-band (X-SAR). The Endeavour missions were designated the Space Radar Laboratory-1 (SRL-1) and -2 (SRL-2). Calibration of polarimetric L- and C-band data for all the different modes SIR-C offers is an especially complicated problem. The solution involves extensive analysis of pre-flight test data to come up with a model of the system, analysis of in-flight test data to determine the antenna pattern and gains of the system during operation, and analysis of data from over fourteen calibration sites distributed around the SIR-C/X-SAR orbit track. The SRL missions were the first time a multifrequency polarimetric imaging radar employing a phased array antenna has been flown in space. Calibration of SIR-C data products involved some unique technical problems given the complexity of the radar system. In this paper, the approach adopted for calibration of SIR-C data is described and the calibration performance of the data products is presented     

Viterbi decoding of the (63, 57) Hamming code-implementation andperformance results

Use of the Viterbi decoder to decode the (63, 57) Hamming code is considered, Implementation and performance of systematic and nonsystematic codes are addressed. It is shown that a Viterbi decoder for the constraint length seven, rate-½ convolutional code can be used to decode both systematic and nonsystematic (63, 57) Hamming codes, but an additional step is needed to complete the decoding of the systematic code. Bounds and simulation results for postdecoding bit-error probability are given and it is shown that the systematic code performs 0.4 dB better than the nonsystematic code. A heuristic explanation is provided     

Properties of ZnO Thin Films Codoped with Lithium and Phosphorus

The properties of ZnO thin films codoped with lithium and phosphorus have been characterized. The films were deposited from high-purity ZnO and Li₃PO₄ solid targets onto c-plane sapphire substrates by radiofrequency (RF) magnetron sputtering. A substrate temperature of 900°C was determined as optimum for depositing undoped ZnO films with background electron concentration of 9.9 × 10¹⁵ cm^?3 as the buffer layer on the sapphire substrate. Postdeposition annealing was carried out using rapid thermal processing in O₂ at temperatures ranging from 500°C to 1000°C for 3 min. Analyses performed using low-temperature photoluminescence spectroscopy measurements revealed luminescence peaks at 3.356 eV, 3.307 eV, 3.248 eV, and 3.203 eV at 12 K for the codoped samples. X-ray diffraction 2θ-scans showed a single peak at about 34.4° with full-width at half-maximum of about 0.09°. Hall-effect measurements revealed initial p-type conductivities, but these were unstable and toggled between p-type and n-type over time with Hall concentrations that varied between 2.05 × 10¹³ cm^?3 and 2.89 × 10¹⁵ cm^?3. The fluctuation in the carrier type could be due to lateral inhomogeneity in the hole concentration caused by stacking faults in the films. An additional cause could be the small Hall voltages in the measurements, which could be significantly impacted by even small spikes in signal noise inherent in the measurements.     

Circuit analysis of an ultrafast junction mixing scanning tunnelingmicroscope

A lumped element circuit model for the operation of a junction mixing scanning tunneling microscope (JM-STM) is presented. Fits from this model show excellent agreement with experimental results in the picosecond time regime. The tip sample capacitance employed in the model was calculated to be 33 fF, using the method of images. By varying the capacitance, various tip/sample geometries can be investigated. Testing the response of the model tunnel junction, for faster electrical pulses, suggests how the JM-STM can be pushed into the femtosecond time regime     

Strain compensated InGaAs-GaAsP-InGaP laser

The performance characteristics of InGaAs-GaAsP-InGaP strain compensated laser emitting near 1 /spl mu/m are reported. The ridge waveguide lasers have room temperature threshold current of 18 mA and differential quantum efficiency of 0.45 W/A/facet. The linewidth enhancement factor is smaller and gain coefficient is larger for these strain compensated lasers compared to that for conventional strained layer laser. This may be due to higher effective compressive strain in the light emitting layer of these devices which reduces the effective mass. The observed larger gain coefficient is consistent with the measured larger relaxation oscillation frequency of these lasers compared to that for a conventional strained layer laser.     

A 210-GHz fT SiGe HBT with a non-self-aligned structure

A record 210-GHz f_T SiGe heterojunction bipolar transistor at a collector current density of 6-9 mA/μm² is fabricated with a new nonself-aligned (NSA) structure based on 0.18 μm technology. This NSA structure has a low-complexity emitter and extrinsic base process which reduces overall thermal cycle and minimizes transient enhanced diffusion. A low-power performance has been achieved which requires only 1 mA collector current to reach 200-GHz f_T. The performance is a result of narrow base width and reduced parasitics in the device. Detailed comparison is made to a 120-GHz self-aligned production device