The Pennsylvania Academy of Science was founded and organized on April 18, 1924, and is an independent non-profit organization that strives "to embrace all disciplines of science and help ensure the scholarly and ethical pursuit of all scientific endeavors." Today the Pennsylvania Academy of Science has members throughout the United States and in other countries. The current president is Andre Walther of Cedar Crest College and the President-Elect is Tammy Tintjer of King's College. Matthew Wallace of East Stroudsburg University of Pennsylvania serves as Immediate-Past President..
Isoprenoids, sometimes also called terpenoids, form a large and diversified family of natural compounds. All isoprenoids are synthesized from a branched five-carbon isoprene unit, which is derived in plants in the cytoplasmic/endoplasmic reticulum (ER)/peroxisome mevalonic acid (MVA) pathway and plastidial methylerythritol phosphate (MEP) pathway. The isoprene unit modules in isoprenoid molecules may be arranged in various ways, the relatively simplest being iterative head-to-tail condensation. Long-chain linear polymers derived in this manner are present in plastidial membranes, where they play a role in photosynthesis. Long-chain linear isoprenoid polymers synthesized on the MVA pathway are also found in the ER membrane (dolichols) and mitochondrial inner membrane [all-trans(E)-nonaprenol trivial name solanesol or all-trans(E)-decaprenol trivial name spadicol]. Both dolichol and solanesol play crucial roles in eukaryotic metabolism: dolichol serves as a cofactor in protein glycosylation and glycosylphosphatidylinositol (GPI) anchor synthesis, while solanesol (or spadicol) acts as the side chain of ubiquinone in electron transport during cellular respiration. Some new roles of the long-chain linear isoprenoid compounds in plants may also be anticipated based on in vivo work on yeast and in vitro biophysical experiments. This review focuses on the known and emerging roles of these compounds in the context of plant physiology and sexual reproduction.
Plants constantly and precisely control their growth by inducing distinct developmental programs to survive and produce high-quality offspring in the changing environment. The fine-tuning of the development according to endogenous and environmental signals requires exact intercellular signaling and a balanced response. Kinases of the Sucrose nonfermenting-1-Related protein Kinases type 2 (SnRK2s) family primarily take part in the response and adaptation to environmental stress factors. Notably, here we show that 2 ABA-nonactivated SnRK2s, SnRK2.4, and SnRK2.10, is also activated in nonstress conditions in developmentally senescing leaves of Arabidopsis thaliana. Phenotypic, biochemical, and molecular analyses performed on single snrk2.4 or snrk2.10, and double snrk2.4/2.10 kinase mutants showed that SnRK2.4 and SnRK2.10, acting redundantly, promote developmental leaf senescence. Further, SnRK2.4 and SnRK2.10 enhance ABA accumulation in senescing leaves by inducing NCED2, one of the key ABA biosynthesis-related genes. The 2 kinases induce developmental leaf senescence by modulating the expression of multiple ABA-responsive, osmotic stress-, and senescence-related genes, such as the senescence master regulators ORE1, ORS1, WRKY33, WRKY75, and ANAC087. Furthermore, we show that SnRK2.4 and SnRK2.10 act upstream of MAPK signaling by enhancing the expression of MAPKKK18, a senescence-inducing kinase. These results document a new regulatory function of SnRK2.4 and SnRK2.10: they are activated in Arabidopsis leaves in response to endogenous signals and redundantly induce developmental leaf senescence by stimulating ABA production and sustaining major ABA-dependent and -independent signaling pathways.
Solid-solution formation and their melting in the Ca3Y2(BO3)(4) - Ca3Yb2(BO3)(4) system were studied. Powder X-ray diffraction confirmed continuous, congruently melting solid solutions for x <= 1.6. A Ca3YYb(BO3)(4) single crystal grown by the Czochralski method partially decomposed upon cooling in the 600-900 C range with the formation of the oxyborate phase CaY1-xYbx(BO3)O. This effect is linked to cation redistribution between the M2 and M3 sites. In contrast, phase-pure Ca3YYb(BO3)(4) crystal blocks were obtained for the first time by spontaneous crystallization from the melt. The refined unit cell parameters are a = 7.130 +/- 0.001 & Aring;, b = 15.253 +/- 0.005 & Aring;, c = 8.609 +/- 0.005 & Aring;. The absorption spectrum of the crystal consisted of a broad (200-400 nm) charge-transfer band and Stark-split lines at 900-1050 nm assigned to the (2)F7/2 -> (2)F5/2 transitions of Yb3+ ion. A dependence of mechanical properties of the crystals on an ionic rare-earth radius was studied and discussed. A nonlinear decrease of Vickers hardness of (100) plane for Ca3YYb(BO3)(4) and Ca3RE2(BO3)(4) (RE-Y, Gd, Nd) crystals at a practically linear increase of the unit cell volume was observed at increase of an ionic radius of RE cation. Such behavior is due to SOFRE increase for M1 and M2 sites and decrease one for M3 site.
We consider strategic reasoning for multi-agent systems modelled as networks of continuous-time probabilistic timed automata (TA) with asynchronous execution (PCAMAS) in the setting of imperfect information. We define PTATL, a probabilistic extension of the alternating-time timed temporal logic TATL, which is interpreted over PCAMAS. Focusing on memoryless strategies of agents with imperfect information, both probabilistic (irP) and deterministic (irp), we establish theoretical results regarding the computational complexity of model checking for the proposed logic: between PSPACE and EXPTIME for PTATL(irp), and in 2EXPTIME for PTATL(irP). We demonstrate the practical feasibility of verification for PTATLirp formulas through a novel proof-of-concept combination of state-of-the-art tools IMITATOR and PRISM on a scalable benchmark, with encouraging results.
Mitochondria are considered one of the main sites of reactive oxygen species (ROS) production in the eukaryotic cells. For this reason, mitochondrial dysfunction associated with increased ROS production underlies various pathological conditions as well as promotes aging. Chronically increased rates of ROS production contribute to oxidative damage to macromolecules, i.e., DNA, proteins, and lipids. Accumulation of unrepaired oxidative damage may result in progressive cell dysfunction, which can finally trigger cell death. The main by-product of mitochondrial oxidative phosphorylation is superoxide, which is generated by the leak of electrons from the mitochondrial respiratory chain complexes leading to one-electron reduction of oxygen. Mitochondrial superoxide dismutase (MnSOD, SOD2) as well as cytosolic superoxide dismutase (Cu/ZnSOD, SOD1), whose smaller pool is localized in the mitochondrial intermembrane space, converts superoxide to H2O2, which can be then degraded by the catalase to harmless H2O.In this chapter, we focus on the relationship between one of the bioenergetic parameters, which is mitochondrial membrane potential, and the rate of ROS formation. We present a set of various methods enabling the characterization of these parameters applicable to isolated mitochondria or intact cells. We also present examples of experimental data demonstrating that the magnitude and direction (increase or decrease) of a change in mitochondrial ROS production depend on the mitochondrial metabolic state.
