Switchgrass Seedling Development as Affected by Seed Size

Seed size has been associated with early seedling vigor (i.e., germination rate, emergence rate, and growth) in grasses. This study was conducted to compare seedling development over a 60-d period in the field as affected by heavy seed (HS) (0.19 to 0.21 g 100 seed-1) and light seed (LS) (0.13 to 0.16 g 100 seed-1) of \u27Blackwell\u27 and \u27Trailblazer\u27 switchgrass (Panicum virgatum L.). The experiment was conducted in 1995 and 1996 at Lincoln, NE, on a Kennebec silt loam (fine-silty, mixed, superactive, mesic Cumnlic Hapludolls). The experimental design was a randomized complete block with four replicates. Seed was separated into two sizes using a South Dakota seed blower. Seed was planted into rows at a rate of 100 pure live seed per meter of row. Plants were excavated and evaluated for shoot weight, leaf area, and root weight. Shoot and root systems were morphologically staged four times during the summer. Seed size differences in switchgrass appeared to produce only slight differences in morphological development of shoot and root systems, leaf area, shoot weight, and adventitious root weight from seedling emergence to 6 wk of growth. Adventitious roots formed more quickly on seedlings from heavier than lighter seed, but the advantage to seedling establishment was minimal even when soil moisture appeared to be lacking. By 8 to 10 wk after emergence, growth and development of LS seedlings were similar to HS seedlings. Once seedlings formed two or more adventitious roots, seed size no longer affected establishment and growth. Seed size in switchgrass appears to have a minimal long-term effect on growth and development of seedlings

Crucial role of SLP-76 and ADAP for neutrophil recruitment in mouse kidney ischemia-reperfusion injury.

Neutrophils trigger inflammation-induced acute kidney injury (AKI), a frequent and potentially lethal occurrence in humans. Molecular mechanisms underlying neutrophil recruitment to sites of inflammation have proved elusive. In this study, we demonstrate that SLP-76 (SH2 domain-containing leukocyte phosphoprotein of 76 kD) and ADAP (adhesion and degranulation promoting adaptor protein) are involved in E-selectin-mediated integrin activation and slow leukocyte rolling, which promotes ischemia-reperfusion-induced AKI in mice. By using genetically engineered mice and transduced Slp76(-/-) primary leukocytes, we demonstrate that ADAP as well as two N-terminal-located tyrosines and the SH2 domain of SLP-76 are required for downstream signaling and slow leukocyte rolling. The Tec family kinase Bruton tyrosine kinase is downstream of SLP-76 and, together with ADAP, regulates PI3Kγ (phosphoinositide 3-kinase-γ)- and PLCγ2 (phospholipase Cγ2)-dependent pathways. Blocking both pathways completely abolishes integrin affinity and avidity regulation. Thus, SLP-76 and ADAP are involved in E-selectin-mediated integrin activation and neutrophil recruitment to inflamed kidneys, which may underlie the development of life-threatening ischemia-reperfusion-induced AKI in humans

Morphological Development of Switchgrass as Affected by Planting Date

Late-spring and early-summer plantings of warm-season grasses often fail, due to dry soil conditions and competition from annual grass and broadleaf weeds. The objective of this study was to compare the morphological development of switchgrass (Panicum virgatum L.) planted in early, mid, and late spring in eastern Nebraska. This study was conducted in 1994 and 1995 at Lincoln, NE, on a Kennebec silt loam (fine-silty, mixed, mesic Cumulic Hapludolls). \u27Blackwell\u27 and \u27Trailblazer\u27 switchgrass were planted in mid-March, late April, and late May using a single-row, precision grass-seed cone planter to a depth of 0.6 to 1.3 cm at 98 pure live seed per linear meter of row in a split-plot design. Twenty seedlings from each plot were excavated to a depth of 20 cm with a spade. Seedling morphological parameters measured were mean stage count root (MSCR) and shoot (MSCS), leaf area, shoot weight, and primary and adventitious root weight. Plots were sampled every 10 d following the first sample date. In 1994, seedlings from the March planting date were more advanced morphologically in MSCR and MSCS, had accumulated 2.5 times more leaf area, and about 3 times more shoot and adventitious root mass than the April planting date when sampled from late May to late June. In 1995, seedlings from the March planting date generally were more advanced morphologically in root and shoot development, had accumulated 2 to 12 times more leaf area, had 2 to 10 times more shoot mass, and had 2 to 33 times more adventitious root mass than the April or May planting dates at the sample periods from early June to mid-July. We suggest that switchgrass should be planted in early spring instead of in late April and May, as suggested by previous research

Developing a second generation Laue lens prototype: high reflectivity crystals and accurate assembly

Laue lenses are an emerging technology that will enhance gamma-ray telescope sensitivity by one to two orders of magnitude in selected energy bands of the \sim 100 keV to \sim 1.5 MeV range. This optic would be particularly well adapted to the observation of faint gamma ray lines, as required for the study of Supernovae and Galactic positron annihilation. It could also prove very useful for the study of hard X-ray tails from a variety of compact objects, especially making a difference by providing sufficient sensitivity for polarization to be measured by the focal plane detector. Our group has been addressing the two key issues relevant to improve performance with respect to the first generation of Laue lens prototypes: obtaining large numbers of efficient crystals and developing a method to fix them with accurate orientation and dense packing factor onto a substrate. We present preliminary results of an on-going study aiming to enable a large number of crystals suitable for diffraction at energies above 500 keV. In addition, we show the first results of the Laue lens prototype assembled using our beamline at SSL/UC Berkeley, which demonstrates our ability to orient and glue crystals with accuracy of a few arcsec, as required for an efficient Laue lens telescope.Comment: Published in the proceedings of the SPIE conference held in San Diego in August 201

The Invertebrate Prey of the Northern Leopard Frog, Rana pipiens, in a Northeastern Ohio Population

Author Institution: Department of Biological Sciences, Kent State UniversityThe purpose of this investigation was to determine the feeding habits of the northern leopard frog, Rana pipiens, in northeastern Ohio. To accomplish this we examined the stomach contents of 13 adults and 19 juveniles collected from a restored wetland in Summit County, Ohio during the summers of 1996 and 1997. The adult and juvenile frogs ingested 142 invertebrates representing 2 phyla, 3 classes, 12 orders, and 34 families. Adult and juvenile frogs consumed both diurnal and nocturnal prey belonging primarily to the insect orders Coleoptera, Hemiptera, and Hymenoptera. Although juvenile frogs consumed more individual prey items than adults (t = 2.196, p <0.05), neither age cohort specialized on active or inactive prey (X2 = 3.84, p <0.05)- Approximately 67% of all prey consumed consisted of fossorial or crawling organisms. Our data suggest that R. pipiens is an efficient predator that maximizes prey diversity by employing more than one feeding strategy

Collapsar Gamma-ray Bursts Grind their Black Hole Spins to a Halt

The spin of a newly formed black hole (BH) at the center of a massive star evolves from its natal value due to two competing processes: accretion of gas angular momentum that increases the spin, and extraction of BH angular momentum by outflows that decreases the spin. Ultimately, the final, equilibrium spin is set by the balance between both processes. In order for the BH to launch relativistic jets and power a $\gamma$-ray burst (GRB), the BH magnetic field needs to be dynamically important. Thus, we consider the case of a magnetically arrested disk (MAD) driving the spin evolution of the BH. By applying the semi-analytic MAD BH spin evolution model of Lowell et al. (2023) to collapsars, we show that if the BH accretes $\sim 20\%$ of its initial mass, its dimensionless spin inevitably reaches small values, $a \lesssim 0.2$. For such spins, and for mass accretion rates inferred from collapsar simulations, we show that our semi-analytic model reproduces the energetics of typical GRB jets, $L_{\rm jet}\sim10^{50}\,\,{\rm erg\,s^{-1}}$. We show that our semi-analytic model reproduces the nearly constant power of typical GRB jets. If the MAD onset is delayed, this allows powerful jets at the high end of the GRB luminosity distribution, $L_{\rm jet}\sim10^{52}\,\,{\rm erg\,s^{-1}}$, but the final spin remains low, $a \lesssim 0.3$. These results are consistent with the low spins inferred from gravitational wave detections of binary BH mergers. In a companion paper, Gottlieb et al. (2023), we use GRB observations to constrain the natal BH spin to be $a \simeq 0.2$

Collapsar Black Holes are Born Slowly Spinning

Collapsing stars constitute the main black hole (BH) formation channel, and are occasionally associated with the launch of relativistic jets that power $\gamma$-ray bursts (GRBs). Thus, collapsars offer an opportunity to infer the natal (before spin-up/down by accretion) BH spin directly from observations. We show that once the BH saturates with large-scale magnetic flux, the jet power is solely dictated by the BH spin and mass accretion rate. Recent core-collapse simulations by Halevi et al. 2022 and GRB observations favor stellar density profiles that yield a typical BH accretion rate, $\dot{m} \approx 10^{-2} {\rm M_\odot~s^{-1}}$, which is weakly dependent on time. This leaves the BH spin as the main factor that governs the jet power. By comparing the resultant jet power to characteristic GRB luminosities, we find rapidly spinning BHs produce jets with excessive power, so that the majority of BHs associated with jets are born slowly spinning with a dimensionless spin $a \simeq 0.2$, or $a \simeq 0.5$ for wobbling jets. This result could be applied to the entire core-collapse BH population, unless an anti-correlation between the stellar magnetic field and angular momentum is present. In a companion paper (Jacquemin-Ide et al. 2023), we show that regardless of the natal spin, the extraction of BH rotational energy ultimately leads to inevitable spin-down to $a \lesssim 0.2$. These results are consistent with recent gravitational wave observations of BH mergers that indicate low spins. We verify our results by carrying out the first 3D general relativistic magnetohydrodynamic simulations of collapsar jets with characteristic GRB energies, powered by slowly spinning BHs. We find that jets of typical GRB power do not retain their energy during the propagation in the star, providing the first numerical indication that many jets might fail to generate a GRB

Skap2 is required for β2 integrin-mediated neutrophil recruitment and functions.

Integrin activation is required for neutrophil functions. Impaired integrin activation on neutrophils is the hallmark of leukocyte adhesion deficiency (LAD) syndrome in humans, characterized by impaired leukocyte recruitment and recurrent infections. The Src kinase-associated phosphoprotein 2 (Skap2) is involved in integrin functions in different leukocyte subtypes. However, the role of Skap2 in β2 integrin activation and neutrophil recruitment is unknown. In this study, we demonstrate the crucial role of Skap2 in regulating actin polymerization and binding of talin-1 and kindlin-3 to the β2 integrin cytoplasmic domain, thereby being indispensable for β2 integrin activation and neutrophil recruitment. The direct interaction of Skap2 with the Wiskott-Aldrich syndrome protein via its SH3 domain is critical for integrin activation and neutrophil recruitment in vivo. Furthermore, Skap2 regulates integrin-mediated outside-in signaling events and neutrophil functions. Thus, Skap2 is essential to activate the β2 integrins, and loss of Skap2 function is sufficient to cause a LAD-like phenotype in mice

Prediction of leaf:stem ratio in grasses using near infrared reflectance spectroscopy

Leaf:stem ratio of grass stands is an important factor affecting diet selection, quality, and forage intake. Estimates of leaf:stem ratios commonly are based on a labor intensive process of hand separating leaf and stem fractions. Near infrared reflectance spectroscopy (NIRS) has been used successfully to predict forage quality and botanical composition of vegetation samples. The objective of this study was to evaluate the use of NIRS to predict leaf:stem ratios in big bluestem (Andropogon gerardii Vitman), switchgrass (Punicum virgatum L.), and smooth bromegrass (Bromus inermis Leyss.). A total of 72 hand-clipped samples of each species was taken from seeded monocultures in eastern Nebraska throughout the 1992,1993, and 1994 growing seasons. Leaf:stem ratio was determined first for each sample and then the entire sample was ground. Samples were scanned by a Perstorp model 6500 near infrared scanning monochromator. Three calibration equations were developed based on using 18, 36, and 54 (l/4, l/2, and 3/4 of total samples, respectively) samples. These 3 calibration equations were used to determine the number of samples necessary to achieve an r2 of 0.70 or higher for each data set. Big bluestem and switchgrass had coefficients of determination (r2) of ≤ 0.69 for all calibration equations except for the equation using only 18 samples of big bluestem r2 = 0.60). Smooth bromegrass had a r2 ranging from only 0.06 to 0.14 for the calibration equations regardless of the number of samples used. Near infrared reflectance spectroscopy was a rapid means of estimating leaf:stem ratios in monocultures of big bluestem and switchgrass but it was not suitable for smooth bromegrass