A Message to the Student Forester

Many times during his four years of academic life the average student forester is confronted with the problem of choosing between the subjects of forest management, forest utilization, or any one o£ the other allied subjects offered in this course. Whether he desires to work for private industry, or some governmental agency, any decision he makes will place him in one o£ these three categories. A student preparing for one type o£ work may be required to study subjects that are foreign to the other branches. However, the fundamental duties, the accompanying responsibilities, and the essential requirements of each after graduation, are practically the same

The Kawishiwi Experimental Forest

An experimental forest is an outdoor laboratory where investigations of plant life may be studied under natural conditions. To be most useful it should be typical of the forested area that it represents so that the results obtained may have general application

Excitation transfer in C-phycocyanin

Calculations of excitation transfer rates among the chromophores of C-phycocyanin using the Förster inductive resonance transfer mechanism have been carried out using the new coordinates for the position and orientation of the chromophores (Schirmer, T., Bode, W. and Huber, R. (1987) J. Mol. Biol. 196, 677–695). Several of the rate constants are significantly altered from the results of our calculations using the previously published coordinates (Sauer, K., Scheer, H. and Sauer, P. (1987) Photochem. Photobiol. 46, 427–440). In particular, for the (αβ)3-trimers of Mastigocladus laminosus or for the (αβ)3-trimers or the (αβ)6-hexamers of Agmenellum quadruplicatum, the new calculations predict excited state relaxation components with exponential time constants shorter than 1 ps. In fact, some of the interchromophore interactions are so strong that exciton coupling is probably the relevant mechanism of interaction. The largest exciton energy is calculated to be about 56 cm−1, for the interaction between the adjacent α84 and β84 chromophores of neighboring monomer units within the (αβ)3-trimers or (αβ)6-hexamers. An energy transfer model invoking a combination of pairwise exciton formation followed by slower Förster transfer steps is described

BEAM-CAVITY INTERACTION IN ELECTRON STORAGE RINGS

A formal expression is obtained for the energy loss per turn, of a rigid bunch of electrons, to a closed cylindrical cavity with quality factor Q. The expression is valid provided the diameter of the entrance and exit ports for the beam are small compared to the bunch length. The effect of the ports is studied in an independent computational method. The energy loss is numerically evaluated for a range of parameters of interest to electron storage rings

A general theory of the spectroscopic properties of partially ordered ensembles. II. Two‐vector problems

We have expanded on the results of an earlier paper [J. Chem. Phys. 72, 221 (1980)] which deals with a method for determining the response of a static, partially ordered ensemble of molecules to various types of electromagnetic probes. In this paper we consider types of spectroscopy whose response depends on the location of two vectors in an axis system fixed with respect to the molecule. Examples of such spectroscopies discussed in detail include fluorescence polarization, photoselection linear dichroism, Raman spectroscopy, and two‐photon absorption. We outline the kinds of structural information available from polarization experiments on partially ordered ensembles.Keywords: ENSEMBLE, POLARIZATION, SPECTROSCOPY, ORIENTATION, RAMAN SPECTRA, MOLECULES, DICHROISM, FLUORESCENC

Single photon timing system for picosecond fluorescence lifetime measurements

A single‐photon timing system is described which is capable of extracting fluorescence lifetimes as short as 25 ps. The system is an improved version of an earlier apparatus. The new system uses a synchronously pumped, mode‐locked dye laser with 10‐ps pulses operating at 82‐MHz repetition rate. A fast photodetector and a leading‐edge discriminator were developed to use with this light source. Also, a special rate reduction circuit was built to eliminate large oscillations in fluorescence decay spectra due to the excessive stop rates that overload commercial time‐to‐amplitude converters.This is the publisher’s final pdf. The published article is copyrighted by the American Institute of Physics and can be found at: http://rsi.aip.org/.Keywords: pulses, photodetectors, fluorescence, mode locking, experimental data, optical pumping, lifetime, photons, mhz range, synchronization, dye lasers, time measurement, time−to−amplitude converter

Electronic Structure and Oxidation State Changes in the Mn4Ca Cluster of Photosystem II

Oxygen-evolving complex (Mn4Ca cluster) of Photosystem II cycles through five intermediate states (Si-states, i =0-4) before a molecule of dioxygen is released. During the S-state transitions, electrons are extracted from the OEC, either from Mn or alternatively from a Mn ligand. The oxidation state of Mn is widely accepted as Mn4(III2,IV2) and Mn4(III,IV3) for S1 and S2 states, while it is still controversial for the S0 and S3 states. We used resonant inelastic X-ray scattering (RIXS) to study the electronic structure of Mn4Ca complex in the OEC. The RIXS data yield two-dimensional plots that provide a significant advantage by obtaining both K-edge pre-edge and L-edge-like spectra (metal spin state) simultaneously. We have collected data from PSII samples in the each of the S-states and compared them with data from various inorganic Mncomplexes. The spectral changes in the Mn 1s2p3/2 RIXS spectra between the S-states were compared to those of the oxides of Mn and coordination complexes. The results indicate strong covalency for the electronic configuration in the OEC, and we conclude that the electron is transferred from a strongly delocalized orbital, compared to those in Mn oxides or coordination complexes. The magnitude for the S0 to S1, and S1 to S2 transitions is twice as large as that during the S2 to S3 transition, indicating that the electron for this transition is extracted from a highly delocalized orbital with little change in charge density at the Mn atoms

Acoustic detection and quantification of benthic egg beds of the squid Loligo opalescens in Monterey Bay, California

Author Posting. © Acoustical Society of America, 2006. This article is posted here by permission of Acoustical Society of America for personal use, not for redistribution. The definitive version was published in Journal of the Acoustical Society of America 119 (2006): 844-856, doi:10.1121/1.2149840.The squid Loligo opalescens is a key species in the nearshore pelagic community of California, supporting the most valuable state marine fishery, yet the stock biomass is unknown. In southern Monterey Bay, extensive beds occur on a flat, sandy bottom, water depths 20–60 m, thus sidescan sonar is a prima-facie candidate for use in rapid, synoptic, and noninvasive surveying. The present study describes development of an acoustic method to detect, identify, and quantify squid egg beds by means of high-frequency sidescan-sonar imagery. Verification of the method has been undertaken with a video camera carried on a remotely operated vehicle. It has been established that sidescan sonar images can be used to predict the presence or absence of squid egg beds. The lower size limit of detectability of an isolated egg bed is about 0.5 m with a 400-kHz sidescan sonar used with a 50-m range when towed at 3 knots. It is possible to estimate the abundance of eggs in a region of interest by computing the cumulative area covered by the egg beds according to the sidescan sonar image. In a selected quadrat one arc second on each side, the estimated number of eggs was 36.5 million.funding from the National Sea Grant, Essential Fish Habitat Program, Sea Grant Project No. NA16RG2273

Where Water is Oxidized to Dioxygen: Structure of thePhotosynthetic Mn4Ca Cluster

Oxidation of water to dioxygen is catalyzed withinphotosystem II (PSII) by a Mn4Ca cluster, the structure of which remainselusive. Polarized extended X-ray absorption fine structure (EXAFS)measurements on PSII single crystals constrain the Mn4Ca cluster geometryto a set of three similar high-resolution structures. Combining polarizedEXAFS and X-ray diffraction data, the cluster was placed within PSIItaking into account the overall trend of the electron density of themetal site and the putative ligands. The structure of the cluster fromthe present study is unlike either the 3.0 or 3.5 Angstrom resolutionX-ray structures, and other previously proposed models