In seed plants, the ovule is the female reproductive structure, which surrounds and nourishes the gametophyte and embryo. This investigation describes the PRETTY FEW SEEDS2 (PFS2) locus, which regulates ovule patterning. The pfs2 mutant exhibited developmental defects in the maternal integuments and gametophyte. This mutation was inherited as a maternal trait, indicating that gametophyte defects resulted from ovule patterning aberrations. Specifically, the boundary between the chalaza and the nucellus, two regions of the ovule primordia, shifted towards the distal end of pfs2 ovule primordia. Results indicated that the PFS2 locus could: (i) be involved in the development of either the nucellus or the chalaza; or (ii) establish a boundary between these two regions. Examination of genetic interactions of the pfs2 mutation with other well-characterized ovule loci indicates that this locus affects integument morphogenesis. Interestingly, the pfs2 inner no outer and pfs2 strubbelig double mutants had inner integuments that appeared similar to their ancestral precursor. The fossil record indicates that the inner integument evolved by fusion of sterilized sporangia or branches around a central megasporangium. The question of whether the structures observed in these double mutants are homologous or merely analogous to the ancestral precursors of the inner integument is discussed.

Compensatory renal hypertrophy leads to an increase in the size and metabolic capacity of renal tubular cells. Increased transport and metabolic activities must be sustained by an augmented rate of energy production, which is largely dependent on mitochondrial processes. Although previous studies have suggested that mitochondria proliferate in the hypertrophying cell, the data to support this have not been convincing. This study was designed to determine whether the mitochondria of the hypertrophied renal proximal tubular cell undergo hypertrophy or proliferation. Flow cytometric analysis of proximal tubular cells obtained from the kidneys of uninephrectomized rabbits revealed an increase in cell size and RNA content compared with control cells but showed no change in DNA content and nuclear size and no evidence of entry into the S/G2/M phases of the cell cycle. Histomorphometric analysis of cortical proximal tubules revealed that although cytoplasmic volume increased, mitochondrial density remained constant, indicating that mitochondrial volume increases in proportion to the increase in cell volume. By day 14, mitochondrial volume had increased 66% above control values. Electron microscopic examination of isolated S2 proximal tubules from 5/6 nephrectomized rabbits with maximal hypertrophy revealed mitochondrial cristae which appeared to be more densely packed than that in normal cells. The size of the functional mitochondrial pool per cell was determined by rhodamine-123 fluorescence. This increased within 24 h of uninephrectomy, peaked at approximately 80% above control levels at 5 days, and remained elevated throughout the 16 days of observation. The initial increase (days 1 and 2) occurred before a measurable increase in mitochondrial volume occurred and presumably reflects an increase in mitochondrial membrane potential.(ABSTRACT TRUNCATED AT 250 WORDS)

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In this paper, the problem of precise relative positioning using GPS (Global Positioning System) CarrierPhase (CP) information is addressed. The unknown cycle ambiguity between GPS satellites and antennas at the moment of receiving the CP signal should be resolved for precise navigation. The sequential Monte Carlo filter approach, called particle filter (PF), is applied to the relative positioning problem which includes the ambiguity resolution problem for the CP nonlinear observation and dynamic equations. The proposed algorithm of GPS CP navigation is based on two main factors. First, even though most existing GPS CP navigation algorithms focus on obtaining the correct integer value among the integer candidates, we directly sample from the three dimensional position space and construct integers consistent with the PF. This allows the PF position estimates to be insensitive to changes of GPS satellites and cycle-slips. Second, the potential large number of samples in position space is handled with the resampling technique in the sequential particle filters. The experimental results show the performance and the advantages of the proposed approach compared to the existing methods.

The Global Positioning System has great potential for the development of new collision avoidance systems and is being considered for the next-generation traffic alert and collision avoidance system. The navigation states estimated by Global Positioning System code information can be broadcast to nearby airplanes via the current traffic alert and collision avoidance system equipment. In this paper, the problem of aircraft collision detection system using Global Positioning System carrier-phase information is addressed. A new approach to the carrier-phase-based relative position estimation problem is proposed that uses particle filters in which the samples are drawn from Cartesian position space coordinates. The particle filters with position samples makes the Global Positioning System carrierphase-based position estimation algorithm robust and practical in that the algorithm is not sensitive to changes of Global Positioning System satellites and cycle slips. The same algorithm can be used to estimate the vehicle attitude if multiple Global Positioning System antennas are used. For a reliable and enhanced collision avoidance system, threedimensional trajectories are projected using relative position, velocity, and attitude estimates. It is shown that the performance of the Global Positioning System carrier-phase-based collision-detecting algorithm meets the accuracy requirements for a precise approach of flight with significantly less collision false alarms and no miss alarms.