Anagrus spp. (Hymenoptera: Mymaridae) reared from plants collected during winter in south central Washington and north central Oregon

Anagrus daanei S. Triapitsyn, A. erythroneurae S. Trjapitzin and Chiappini, and A. frettakovae S. Triapitsyn parasitize Western grape leafllopper, Erythroneura elegantula Osborn, and Virginia creeper leafhopper, E. ziczac Walsh, eggs during the summer. These leafhoppers overwinter as adults and Anagrus overwinter in leafhopper eggs. Thus, Anagrus must find other leafhopper eggs in which to overwinter. To identify plants on which these parasitoids and their host eggs overwinter, we collected 31 species of plants from 52 sites in the grape growing region of south central Washington and north central Oregon during the winter from 2000 to 2007. A total of 733 female and 1066 male Anagrus was reared from the plants. Twelve plant species harboured Anagrus spp. during the winter. Anagrus erythroneurae was reared from blackberry, Rubus armeniacus Focke; willow, Salix spp.; Wood’s rose, Rosa woodsii Lindley; sweetbrier rose, R. eglanteria L.; rugose rose, R. rugosa Thunberg; and ornamental roses, Rosa spp. L. Anagrus tretiakovae was found on choke cherry, Prunus virginiana L.; rugose rose; Rosa spp.; and blackberry. Only one specimen, from omamental rose, was tentatively identified as A. daanei. Other specimens were identified as A. atomus L., A. avalae Soyka, A. nr. sp. avalae, A. nr. sp. columbi Perkins, A. nigriventris Girault, and A. nr. sp. nigriventris

Sources of Spring and Fall Hop Aphid, Phorodon humuli (Schrank), (Homoptera: Aphididae) Migrants in South Central Washington

The hop aphid, Phorodon humuli (Schrank), flies from hop, Humulus lupulus L., to its overwintering Prunus spp. hosts in the fall. The sources of these aphids were not known because much of the aphid flight occurs after hop plants are removed from fields during harvest. We found that the bottoms of hop plants remaining alive in harvested hop yards averaged 1.7 to 5.8 hop aphids per leaf in three years of sampling. Unharvested hop plants remaining after harvest averaged 32.8 to 127.1 aphids per leaf in two years. Feral hops were also infested with hop aphids in late summer and early fall. Sources for the spring aphid flight from Prunus spp. to hop included Prunus cerasifera Ehrhart, which averaged 44.0 to 105.1 aphids per shoot in two years of sampling. Fruit-type Prunus spp. trees growing on residential properties averaged 0.9 and 11.3 aphids per shoot in the same years but few of these trees were found. Plum and prune orchards averaged 0 to 5.5 aphids per shoot in two years and estimates indicate that orchard trees are much more numerous than other hop aphid host trees. Potential alternative management strategies for hop aphid control are discussed

6% of the primary parasitoids in 1999 and for 52.1% in 2000. Praon unicum Smith was second in abundance with 14.3% in 1999 and 37

ABSTRACT In 1999, 802 primary parasitoids and 1,448 hyperparasitoids were reared from 83 samples of hop aphids, Phorodon humuli (Schrank), collected from Prunus sp. at 47 sites in the hop-growing area of south central Washington. In 2000, we collected 94 primary parasitoids and 180 hyperparasitoids in 59 samples from 28 sites. Parasitoids (primary plus hyperparasitoids) were reared from over 86% of the samples in 1999 and 61% of the samples in 2000. Lysiphlebus testaceipes (Cresson) was the most abundant primary parasitoid, accounting for 81.6% of the primary parasitoids in 1999 and for 52.1% in 2000. Praon unicum Smith was second in abundance with 14.3% in 1999 and 37.2% in 2000. Other primary parasitoids were Aphelinidae (0.9% in 1999 and 4.3% in 2000), Aphidius ervi Haliday (1.0% in 1999 and 1.1% in 2000), Diaeretiella rapae (M'Intosh) (0.3% in 1999 and 0% in 2000), and P. occidentale Baker (0.4% in 1999 and 0% in 2000). Aphelinidae have not been reported previously from hop aphids. D. rapae and P. occidentale Baker are new records for the hop aphid on Prunus. Hyperparasitoids were in the genera Alloxysta (Charipidae), Asaphes and Pachyneuron (Pteromalidae), and Dendrocerus (Megaspilidae). This initial study indicates that the primary parasitoids have potential as biological control agents

A multiwavelength study of the remnant of nova GK Persei

We present new observations of the nebular remnant of the old nova GK Persei 1901, in the optical using the 2m HCT and at low radio frequencies using the GMRT. The evolution of the nova remnant indicates shock interaction with the ambient medium, especially in the southwest quadrant. Application of a simple model for the shock and its evolution to determine the time dependence of the radius of the shell in the southwest quadrant indicates that the shell is now expanding into an ambient medium that has a lower density compared to the density of the ambient medium ahead of the shock in 1987.There are indications of a recent interaction of the nova remnant with the ambient medium in the northeast quadrant also. The nova remnant of GK Per is detected at all the observed radio frequencies and is of similar extent as the optical remnant. Putting together our radio observations with VLA archival data on GK Per from 1997, we obtain three interesting results: 1. The spectrum above 1.4 GHz follows a power law with an index -0.7 and below 1.4 GHz follows a power law with an index ~ -0.85. This could be due to the presence of at least two populations of electrons dominating the global emission at different frequencies. 2. We record an annual secular decrease of 2.1% in the flux density of the nova remnant at 1.4 and 4.9 GHz between 1984 and 1997 which has left the spectral index unchanged at -0.7. No such decrease is observed in the flux densities below 1 GHz. 3. We record an increase in the flux density at 0.33 GHz compared to the previous estimate in 1987. We conclude that the remnant of nova GK Per is similar to supernova remnants and in particular, to the young supernova remnant Cas A.Comment: 10 pages; uses A&A style; figures 1, 2 & 6 are in JPEG format. Accepted for publication in Astronomy & Astrophysics. Full paper including Figures 1, 2 & 6 may be downloaded from http://www.iiap.res.in/personnel/gca/gca.htm

Preserving the positive student outcomes of CUREs through disruption: implications for remote learning

We evaluated how faculty adapted course-based undergraduate research experiences (CUREs) to remote instruction and compared student outcomes with CUREs offered in-person in prior semesters. Our findings suggest that partially remote CUREs can be as effective as face-to-face CUREs and provide evidence supporting the potential benefits of CUREs in hybrid or remote learning contexts.Published versio

Tin Whisker Electrical Short Circuit Characteristics

Existing risk simulations make the assumption that when a free tin whisker has bridged two adjacent exposed electrical conductors, the result is an electrical short circuit. This conservative assumption is made because shorting is a random event that has an unknown probability associated with it. Note however that due to contact resistance electrical shorts may not occur at lower voltage levels. In our first article we developed an empirical probability model for tin whisker shorting. In this paper, we develop a more comprehensive empirical model using a refined experiment with a larger sample size, in which we studied the effect of varying voltage on the breakdown of the contact resistance which leads to a short circuit. From the resulting data we estimated the probability distribution of an electrical short, as a function of voltage. In addition, the unexpected polycrystalline structure seen in the focused ion beam (FIB) cross section in the first experiment was confirmed in this experiment using transmission electron microscopy (TEM). The FIB was also used to cross section two card guides to facilitate the measurement of the grain size of each card guide's tin plating to determine its finish

All-optical switching in a two-channel waveguide with cubic-quintic nonlinearity

We consider dynamics of spatial beams in a dual-channel waveguide with competing cubic and quintic (CQ) nonlinearities. Gradually increasing the power in the input channel, we identify four different regimes of the pulses coupling into the cross channel, which alternate three times between full pass and full stop, thus suggesting three realizations of switching between the channels. As in the case of the Kerr (solely cubic) nonlinearity, the first two regimes are the linear one, and one dominated by the self-focusing nonlinearity, with the beam which, respectively, periodically couples between the channels, or stays in the input channel. Further increase of the power reveals two novel transmission regimes, one characterized by balance between the competing nonlinearities, which again allows full coupling between the channels, and a final regime dominated by the self-defocusing quintic nonlinearity. In the latter case, the situation resembles that known for a self-repulsive Bose-Einstein condensate trapped in a double-well potential, which is characterized by strong symmetry breaking; accordingly, the beam again abides in the input channel, contrary to an intuitive expectation that the self-defocusing nonlinearity would push it into the cross channel. The numerical results are qualitatively explained by a simple analytical model based on the variational approximation.Comment: Journal of Physics B (in press

One more neighbor: The first brown dwarf in the VVV survey

Context. The discovery of brown dwarfs (BDs) in the solar neighborhood and young star clusters has helped to constraint the low-mass end of the stellar mass function and the initial mass function. We use data of the Vista Variables in the V\'ia L\'actea (VVV), a near-infrared (NIR) multiwavelength (Z Y J H Ks) multi-epoch (Ks) ESO Public Survey mapping the Milky Way bulge and southern Galactic plane to search for nearby BDs. Aims. The ultimate aim of the project is to improve the completeness of the census of nearby stellar and substellar objects towards the Galactic bulge and inner disk regions. Methods. Taking advantage of the homogeneous sample of VVV multi-epoch data, we identified stars with high proper motion (> 0.1"/yr), and then selected low-mass objects using NIR colors. We searched for a possible parallax signature using the all available Ks band epochs. We set some constraints on the month-to-year scale Ks band variability of our candidates, and even searched for possible transiting companions. We obtained NIR spectra to properly classify spectral type and then the physical properties of the final list of candidates. Results. We report the discovery of VVV BD001, a new member of the local volume-limited sample (within 20pc from the sun) with well defined proper motion, distance, and luminosity. The spectral type of this new object is an L5+-1, unusually blue dwarf. The proper motion for this BD is PM(\alpha)=-0.5455+-0.004 "/yr, PM(\delta)=-0.3255+-0.004 "/yr, and it has a parallax of 57+-4 mas which translates into a distance of 17.5 +- 1.1 pc. VVV BD001 shows no evidence of variability (\Delta Ks <0.05mag) over two years, especially constrained on a six month scale during the year 2012.Comment: 5 pages, 4 figures, 1 table, Accepted for publication in Astronomy and Astrophysics Letter