Gardenia Memories

A dazzling stream of golden morning sunlight slants between claret coloured drapes to touch three gardenias on a mahogany dressing table

Understory Growth Dynamics and Mensuration Techniques in Uneven-Aged, Mixed-Species Northern Conifer Stands

Managing uneven-aged, mixed-species stands requires balancing the need for high leaf area allocation in the overstory where it is most efficient versus the need to allow for sufficient growth of younger cohorts in the understory. To help forest managers make informed decisions to maintain this balance, the understory growth dynamics of northern conifer species in stands managed under uneven-aged silvicultural systems were studied. Sapling height growth of Picea rubens Sarg., Abies balsamea (L.) Mill, and Tsuga canadensis (L.) Carr. were modeled as a function of overstory canopy openness (gap fraction) using regression analysis. Research was conducted in four uneven-aged northern conifer stands on the Penobscot Experimental Forest in eastern Maine; two replicates each of selection cutting on five- and ten-year cycles. Gap fraction estimates were obtained directly above 167 sample trees between 0.5-6.0 m in height, using a LI- COR LAI-2000 plant canopy analyzer. These estimates were tested in several model forms along with initial tree height to predict sapling height growth. The effect of different vertical distributions of foliage on sapling height growth was also explored using analysis of covariance. Using cluster analysis, plots were grouped into one of three categories based on similar vertical leaf area structure. Species-specific height growth was then compared between groups of similar vertical structure using initial tree height as a covariate. An innovative method employing vertical point sampling was used to obtain leaf area estimates to quantify plot-level vertical leaf area structure. To validate the use of vertical point sampling, plot-level leaf area index (LAI) and basal area (BA) estimates based on vertical point sampling were compared with conventional horizontal point sampling using a 2 m2/ha basal area factor (BAF) prism. Tree-level LA1 estimates were replaced with specieslspecific constants based on projected leaf area (PLA)-height squared and PLA-DBH\u27 linear regression coefficients in an effort to develop a quick and accurate method to estimate LA1 in the field using both vertical point sampling and prism sampling. Leaf area index measurements, BA, and tree tallies from vertical point sampling were also related to gap fraction measurements to determine if an efficient method for in-the-field gap fraction estimation could also be developed. Regression modeling demonstrated that sapling height growth of all three species followed a monotonically increasing pattern with respect to decreasing canopy closure. Abies balsamea appeared to be the most aggressive competitor demonstrating the greatest response to changes in gap fraction while Tsuga canadensis appeared to be the least responsive to changes in gap fraction. Although total plot-level LA1 was not significant in predicting height growth in these complex stands, the vertical distribution of leaf area was. While height growth of Abies balsamea and Tsuga canadensis were not significantly different between vertical leaf area structures, height growth of Picea rubens was significantly higher in plots with well-developed understories with high LAI, regardless of overstory LAI. Vertical point sampling showed strong promise in providing LA1 estimates, and in particular facilitating in-the-field LA1 estimation with the use of species-specific tree- level LA1 constants that remove the need for individual tree measurements. More field- testing of this technique needs to be done. Simple vertical point sample measures were not successful in accurately predicting gap fraction

Resolving Phonon Fock States in a Multimode Cavity with a Double-Slit Qubit

We resolve phonon number states in the spectrum of a superconducting qubit coupled to a multimode acoustic cavity. Crucial to this resolution is the sharp frequency dependence in the qubit-phonon interaction engineered by coupling the qubit to surface acoustic waves in two locations separated by $\sim40$ acoustic wavelengths. In analogy to double-slit diffraction, the resulting self-interference generates high-contrast frequency structure in the qubit-phonon interaction. We observe this frequency structure both in the coupling rate to multiple cavity modes and in the qubit spontaneous emission rate into unconfined modes. We use this sharp frequency structure to resolve single phonons by tuning the qubit to a frequency of destructive interference where all acoustic interactions are dispersive. By exciting several detuned yet strongly-coupled phononic modes and measuring the resulting qubit spectrum, we observe that, for two modes, the device enters the strong dispersive regime where single phonons are spectrally resolved.Comment: 9 pages, 8 figures; revised arguments in paragraphs 3 and 8, added Hamiltonian description, and corrected typo

Parametrically controlling solitary wave dynamics in modified Kortweg-de Vries equation

We demonstrate the control of solitary wave dynamics of modified Kortweg-de Vries (MKdV) equation through the temporal variations of the distributed coefficients. This is explicated through exact cnoidal wave and localized soliton solutions of the MKdV equation with variable coefficients. The solitons can be accelerated and their propagation can be manipulated by suitable variations of the above parameters. In sharp contrast with nonlinear Schr\"{o}dinger equation, the soliton amplitude and widths are time independent.Comment: 4 pages, 5 eps figure

A study of the flocculation of phospholipids as a model of membrane interactions

Dispersion of the pure phospholipids phosphatidylcholine (lecithin) and phosphatidyiserine were prepared in solutions of different ionic type and concentration. The dispersions were prepared so as to give particies, spherules, of the phospholipids which were of a fairly constant diameter, i.e. they were quasi-monodisperse suspensions. The dispersions were subjected to a laminar flow shear gradient was to affect collisions between the particles of the dispersions and thus to bring about flocculation or aggregation of the suspensions. By measuring the total number of particles in the dispersions at timed intervals a parameter was calculated for each aggregation, the collision efficiency. The collision efficiency is a measure of the rate of aggregation and can also be used to calculate the enrgy of the adhesive interaction of the particles. The values of the collision efficiency for the flocculation of lecithin spherules showed that for the monovalent cations the order of increasing efficacy was Potassium: Sodium: Lithium which is the order of decreasing ionic radius. The results for divalent cations showed that these were more effective by at least two orders of magnitude. Further divalent cations exhibited a reversal of charge behaviour at concentrations above about 10-3 molar. The order of increasing efficacy did not reflect the order of decreasing ionic radius and was Magnesium: Strontium: Barium: Calcium, which suggest that lecithin may have a specific affinity for Calcium. The trivalent cation Lanthanum was more effective than the divalent cations and showed a charge reversal at a lower concentration. Temperature was found to have little effect on the rate of flocculation of lecithin dispersion. For the flocculation of phosphatidylserine dispersions higher concentrations of sodium and calcium ions were found to be necessary, than for the flocculation of lecithin dispersions. This was to be expected because phosphatidylserine spherules are considered to bear a considerable negative surface charge, whereas those of lecitihin are considered to be uncharged. The collision efficiency, measured in ionic conditions where the spherules are probably uncharged, was used to calculate a value for the London-Hamaker constant. Values in the range 7x10

Plasmodium berghei Kinesin-5 Associates With the Spindle Apparatus During Cell Division and Is Important for Efficient Production of Infectious Sporozoites

Kinesin-5 motors play essential roles in spindle apparatus assembly during cell division, by generating forces to establish and maintain the spindle bipolarity essential for proper chromosome segregation. Kinesin-5 is largely conserved structurally and functionally in model eukaryotes, but its role is unknown in the Plasmodium parasite, an evolutionarily divergent organism with several atypical features of both mitotic and meiotic cell division. We have investigated the function and subcellular location of kinesin-5 during cell division throughout the Plasmodium berghei life cycle. Deletion of kinesin-5 had little visible effect at any proliferative stage except sporozoite production in oocysts, resulting in a significant decrease in the number of motile sporozoites in mosquito salivary glands, which were able to infect a new vertebrate host. Live-cell imaging showed kinesin-5-GFP located on the spindle and at spindle poles during both atypical mitosis and meiosis. Fixed-cell immunofluorescence assays revealed kinesin-5 co-localized with α-tubulin and centrin-2 and a partial overlap with kinetochore marker NDC80 during early blood stage schizogony. Dual-color live-cell imaging showed that kinesin-5 is closely associated with NDC80 during male gametogony, but not with kinesin-8B, a marker of the basal body and axonemes of the forming flagella. Treatment of gametocytes with microtubule-specific inhibitors confirmed kinesin-5 association with nuclear spindles and not cytoplasmic axonemal microtubules. Altogether, our results demonstrate that kinesin-5 is associated with the spindle apparatus, expressed in proliferating parasite stages, and important for efficient production of infectious sporozoites

Nucleotide– and Mal3-dependent changes in fission yeast microtubules suggest a structural plasticity view of dynamics

Using cryo-electron microscopy, we characterize the architecture of microtubules assembled from Schizosaccharomyces pombe tubulin, in the presence and absence of their regulatory partner Mal3. Cryo-electron tomography reveals that microtubules assembled from S. pombe tubulin have predominantly B-lattice interprotofilament contacts, with protofilaments skewed around the microtubule axis. Copolymerization with Mal3 favors 13 protofilament microtubules with reduced protofilament skew, indicating that Mal3 adjusts interprotofilament interfaces. A 4.6-Å resolution structure of microtubule-bound Mal3 shows that Mal3 makes a distinctive footprint on the S. pombe microtubule lattice and that unlike mammalian microtubules, S. pombe microtubules do not show the longitudinal lattice compaction associated with EB protein binding and GTP hydrolysis. Our results firmly support a structural plasticity view of microtubule dynamics in which microtubule lattice conformation is sensitive to a variety of effectors and differently so for different tubulins