Attracting medical students and doctors into surgical training in the UK and Ireland.

AIMS: Core surgical training (CST) programmes in the UK have seen a significant reduction in competition ratios over the past five years. This study aimed to determine motivating factors and perceived barriers to pursuing a career in surgery amongst junior doctors in training and medical students attending an annual conference. METHODS: A self-reported, electronic questionnaire was distributed to medical students, foundation year doctors, and doctors in postgraduate surgical training programmes (DIPST) who attended the Association of Surgeons in Training (ASiT) Conference in 2016. Respondents ranked factors attracting them to a career in surgery and factors that could improve perceptions of surgical careers. Chi-square test was used to test for differences between groups (a = 0.05, R Studio, V3.3.1). RESULTS: Of 394 respondents (response rate = 50.9%), 44.9% were medical students or foundation doctors ('Pre-CST') and 55.1% were DIPST ('Peri/post-CST'). Practical application of skills (97.4%), enjoyment of the theatre environment (95.4%) and positive experiences in surgical firms (84.7%) were primary driving factors towards a surgical career. Availability of private practice (32.2%), and sustainability of consultant jobs (49.0%) had less influence. For 'Pre-CST' respondents, role models (82.8% pre-CST v 74.9% peri-post CST, p < 0.05) and defined career progression (67.2% pre-CST v 47.0% peri-post CST, p < 0.001) were particularly important. 91% of all respondents agreed that a better balance of training and service within worked hours would improve perceptions of surgery. CONCLUSION: Addressing the motivating factors and perceived barriers to surgical careers will help bolster recruitment of the future surgical workforce.

Development and validation of a weather-based warning system to advise fungicide applications to control dollar spot on turfgrass.

Dollar spot is one of the most common diseases of golf course turfgrass and numerous fungicide applications are often required to provide adequate control. Weather-based disease warning systems have been developed to more accurately time fungicide applications; however, they tend to be ineffective and are not currently in widespread use. The primary objective of this research was to develop a new weather-based disease warning system to more accurately advise fungicide applications to control dollar spot activity across a broad geographic and climactic range. The new dollar spot warning system was developed from data collected at field sites in Madison, WI and Stillwater, OK in 2008 and warning system validation sites were established in Madison, WI, Stillwater, OK, Knoxville, TN, State College, PA, Starkville, MS, and Storrs, CT between 2011 and 2016. A meta-analysis of all site-years was conducted and the most effective warning system for dollar spot development consisted of a five-day moving average of relative humidity and average daily temperature. Using this model the highest effective probability that provided dollar spot control similar to that of a calendar-based program across the numerous sites and years was 20%. Additional analysis found that the 20% spray threshold provided comparable control to the calendar-based program while reducing fungicide usage by up to 30%, though further refinement may be needed as practitioners implement this warning system in a range of environments not tested here. The weather-based dollar spot warning system presented here will likely become an important tool for implementing precision disease management strategies for future turfgrass managers, especially as financial and regulatory pressures increase the need to reduce pesticide usage on golf course turfgrass.

Infection and Colonization of Several Bermudagrasses by Ophiosphaerella korrae.

Bermudagrass (Cynodon spp.) is the most commonly used turfgrass in the southern United States where it is severely affected by spring dead spot (SDS) caused by Ophiosphaerella herpotricha, O. korrae, and O. narmari. In this study, infection of bermudagrass roots and stolons by O. korrae was characterized using a transformant that expressed the red fluorescent protein tdTomato. Roots of interspecific hybrid cultivars Midlawn and Tifway 419, C. transvaalensis accessions Uganda and 3200, and C. dactylon cultivar U3 were inoculated and observed from 2 to 14 days postinoculation (DPI) while stolons were observed from 2 to 22 DPI. For all five cultivars tested, a similar level of root colonization was observed; however, differences were observed in the rate of necrosis development. Necrosis of Tifway 419 and Midlawn tissues was evident at 2 DPI, in Uganda and 3200 at 8 DPI, and in U3 necrosis was often absent as late as 14 DPI. The fungus rapidly penetrated the root epidermis and colonized the cortex of all cultivars by 4 DPI. Colonization of stele tissues by O. korrae was rare in hybrid cultivars but common in C. transvaalensis and C. dactylon accessions. On intact stolons, the fungus did not penetrate the epidermis 22 DPI though epidermal necrosis was evident on the surface of only the hybrid bermudagrasses. Wounded stolons became necrotic in all cultivars. Infection and colonization of various bermudagrasses by O. korrae was found to be similar to that by O. herpotricha, suggesting that host genetic resistance may be used for effective management of SDS caused by both species.

First Report of Dollar Spot of Sandbur Caused by Sclerotinia homoeocarpa in Oklahoma.

Sandbur (Cenchrus incertus Curtis) is a warm-season, annual, noxious, grassy weed native to southern North America. It is common in sandy, disturbed soils and can also be found in home lawns and sport fields where low turf density facilitates its establishment. In July 2013, after a period of frequent rainfall and heavy dew, symptoms of dollar spot-like lesions (1) were observed on sandbur plants growing in a mixed stand of turf-type and native warm-season grasses in Logan County, Oklahoma. Lesions, frequently associated with leaf sheaths, were tan and surrounded by a dark margin. Symptomatic leaves were surface sterilized and plated on potato dextrose agar amended with 10 ppm rifampicin, 250 ppm ampicillin, and 5 ppm fenpropathrin. After incubation, a fungus morphologically identical to Sclerotinia homoeocarpa Bennett was consistently isolated. The nuclear ribosomal internal transcribed spacer (ITS) region of two different isolates, SCL2 and SCL3, were amplified using primers ITS4 and ITS5 (2). The DNA products were sequenced and BLAST analyses were used to compare sequences with those in GenBank. The sequence for isolate SLC2 was 869 bp, contained a type I intron in the 18S small subunit rDNA, and was identical to accession EU123803. The ITS sequence for isolate SLC3 was 535 bp and identical to accession EU123802. Twenty-five-day-old seedlings of C. incertus were inoculated by placing 5-mm-diameter agar plugs, colonized by mycelia of each S. homoeocarpa isolate, onto two of the plants' leaves. Plugs were held in place with Parafilm. Two plants were inoculated with each isolate and sterile agar plugs were placed on two leaves of another seedling as control. Plants were incubated in a dew chamber at 20°C and a 12-h photoperiod. After 3 days of incubation, water-soaked lesions surrounded by a dark margin appeared on inoculated plants only. Fungi that were later identified as S. homoeocarpa isolates SLC2 and SLC3 by sequencing of the ITS region were re-isolated from symptomatic leaves, fulfilling Koch's postulates. To our knowledge, this is the first report of dollar spot on sandbur. References: (1) R. W. Smiley et al. Page 22 in: Compendium of Turfgrass Diseases. 3rd ed. The American Phytopathological Society, St. Paul, MN, 2005. (2) T. J. White et al. Page 315 in: PCR Protocols: A Guide to Methods and Applications. Academic Press, San Diego, CA, 1990.

Influence of Fungicide Application Timings on the Management of Bermudagrass Spring Dead Spot Caused by Ophiosphaerella herpotricha.

Spring dead spot, caused by Ophiosphaerella spp., is the most important disease of bermudagrass (Cynodon dactylon and C. dactylon × C. transvaalensis) where cool temperatures induce dormancy. Field plot studies were conducted from 2004 to 2008 to determine the frequency and timings of fungicide applications for control of the disease. The fungicide treatments included tebuconazole applied two, three, or four times in the fall, once in the spring plus twice in the fall, or twice in the spring and twice in the fall. Propiconazole treatments consisted of one spring, one spring and one fall, one spring and two fall, or two fall applications. Disease severity in plots treated three or four times in the fall with tebuconazole was significantly lower than for those not treated. Based on the change in patch size prior to treatment, patches in plots treated four times with tebuconazole were smaller than in the previous year and were smaller than patches treated once in the spring and twice in the fall or twice in the fall. Plots receiving two fall, one spring and one fall, or one spring and two fall applications of propiconazole had less disease than plots treated once in the spring or plots not treated. Based on the change in plot area prior to treatment, plots receiving two fall, one spring and one fall, or one spring and two fall propiconazole applications had a reduction in plot area expressing symptoms of disease. These studies demonstrated that two fall or one spring and one fall application appear to provide the most effective and cost effective disease control in an integrated approach to managing the disease. The study also demonstrates the importance of disease severity assessment prior to treatment in evaluating the efficacy of a control measure for spring dead spot.

Species composition and seasonal occurrence of Phyllophaga (Coleoptera: Scarabaeidae) infesting intensely managed Bermudagrass in Oklahoma.

Larvae of Phyllophaga spp. (Coleoptera: Scarabaeidae) are important turfgrass pests in many regions of the United States. However, not all of the species associated with turfgrass are known, including species most likely to be of economic concern in Oklahoma turfgrasses, especially Bermuda grass. This study documented the species composition and seasonal occurrence of Phyllophaga associated with high maintenance Bermuda grass turf in Oklahoma over a 2-yr period. In 2005 and 2006, adult Phyllophaga spp. were collected with blacklight traps from selected golf courses throughout Oklahoma Phyllophaga larvae were obtained from Bermuda grass stands at selected sod production facilities adjacent to or near the light traps. We collected 20 species of Phyllophaga beetles in light traps, and nine species of Phyllophaga larvae from turfgrass. Peak flight periods for most species occurred in May and June, but some were captured as early as mid-April and others as late as September. The cytochrome c oxidase I (COI) gene from adults and larvae was amplified using polymerase chain reaction, sequenced, and then used to compare larval DNA against DNA from identified adults. These results confirmed the validity of using COI sequences to identify species of some Phyllophaga larvae. The identifications will aid in optimizing the timing of insecticide applications against Phyllophaga white grubs as discussed.

An investigation of the molecular geometry and electronic structure of nitryl chloride by a combination of rotational spectroscopy and ab initio calculations.

The ground-state rotational spectra of the six isotopomers (16)O(2) (14)N(35)Cl, (16)O(2) (14)N(37)Cl, (18)O(16)O(14)N(35)Cl, (18)O(2) (14)N(35)Cl, (16)O(2) (15)N(35)Cl, and (16)O(2) (15)N(37)Cl of nitryl chloride were observed with a pulsed-jet, Fourier-transform microwave spectrometer to give rotational constants, Cl and (14)N nuclear quadrupole coupling, and spin-rotation coupling constants. These spectroscopic constants were interpreted to give r(0), r(s), and r(m) ((2)) versions of the molecular geometry and information about the electronic redistribution at N when nitryl chloride is formed from NO(2) and a Cl atom. The r(m) ((2)) geometry has r(N-Cl)=1.8405(6) A, r(N-O)=1.1929(2) A, and the angle ONO=131.42(4) degrees , while the corresponding quantities for the r(s) geometry are 1.8489 A, 1.1940 A, and 131.73 degrees , respectively. Electronic structure calculations at CCSD(T)cc-pVXZ (X=T, Q, or 5) levels of theory were carried out to give a r(e) geometry, vibration-rotation corrections to equilibrium rotational constants, and values of the (35)Cl and (14)N nuclear hyperfine (quadrupole and spin-rotation) coupling constants in good agreement with experiment. The equilibrium geometry at the CCSD(T)/cc-pV5Z level of theory has r(N-Cl)=1.8441 A, r(N-O)=1.1925 A and the angle ONO=131.80 degrees . The observed rotational constants were corrected for the vibration-rotation effects calculated ab initio to yield semiempirical equilibrium constants which were then fitted to give the following semiempirical equilibrium geometry: r(N-Cl)=1.8467(2) A, r(N-O)=1.1916(1) A, and the angle ONO=131.78(3) degrees .

First Report of Dollar Spot of Buffalograss Caused by Sclerotinia homoeocarpa in Oklahoma.

Buffalograss (Buchloe dactyloides (Nutt.) Engelm.) is a perennial, warm-season grass native to the central plains of North America and a dominant plant over much of the shortgrass prairie ecosystem. Its prostrate growth habit and excellent drought tolerance make it a commercially promising turfgrass species, and numerous turf-type cultivars have been released. In the spring of 2007, the southern plains states experienced prolonged periods of excessive precipitation during which numerous buffalograss swards throughout north-central Oklahoma exhibited symptoms of dollar spot (1). A fungus morphologically identical to Sclerotinia homoeocarpa Bennett was consistently isolated from diseased buffalograss leaves collected from three locations in Oklahoma, two from Payne County and one from Logan County. Thirty-day-old seedlings of B. dactyloides ('Cody' and 'Topgun') and Agrostis stolonifera ('SR1020') were inoculated by placing potato dextrose agar (PDA) plugs, colonized by mycelia of each S. homoeocarpa isolate, onto the seedlings' leaves. Sterile PDA plugs were placed on plants as controls. Leaf lesions developed after 4 days only on inoculated plants, and S. homoeocarpa was reisolated from lesions, satisfying Koch's postulates. The nuclear ribosomal internal transcribed spacer (ITS) region was amplified from DNA extracted from cultures of the three buffalograss isolates and a bentgrass isolate using primers ITS4 and ITS5 (2) and sequenced. Sequences were similar to one another (97 to 99% identical), however, two isolates shared a 420-bp, type I intron in the 18S small subunit rDNA. A search of GenBank at NCBI found the ITS sequences were most similar to the ITS regions of other S. homoeocarpa accessions (97% identical). The ITS sequences from the four isolates were deposited in GenBank (Accession Nos. EU123800-EU123803). To our knowledge, this is the first report of dollar spot on a native, warm-season grass in the United States and the disease appears to be endemic to buffalograss in Oklahoma and Kansas (N. A. Tisserat, personal communication). References: (1) R. W. Smiley et al. Page 22 in: Compendium of Turfgrass Diseases. 3rd ed. The American Phytopathological Society, St. Paul, MN, 2005. (2) T. J. White et al. Page 315 in: PCR Protocols: A Guide to Methods and Applications. Academic Press Inc., New York, 1990.

Influence of Temperature and Time of Year on Colonization of Bermudagrass Roots by Ophiosphaerella herpotricha.

The influence of temperature on the infection of bermudagrass seedlings by Ophiosphaerella herpotricha and colonization of plants in the field was investigated. Bermudagrass seedlings (cv. Jackpot) inoculated with O. herpotricha exhibited dark lesions after 8 days. Root lesion length was greatest at 17°C and was similar for all temperatures examined below 21°C. Seedlings grown at 25 or 30°C had small lesions that remained similar in size when evaluated at 8 and 10 days post inoculation. Colonization of bermudagrass roots from field plots were examined in July, October, and November of 2003 and 2004. In 2003, no differences between sampling dates were observed for plants sampled from the edge of the spring patch in 5.4-cm increments to a total distance of 21.6 cm. In 2004, July and October samples were similar; however, an increase in root colonization was found between the October and November samplings. These studies suggest that infection and colonization of bermudagrass roots by O. herpotricha occurs over a wide range of cool soil temperatures, occurs in the spring, and can be variable in the autumn.

First Report of Ergot of Bermudagrass Caused by Claviceps cynodontis in Oklahoma.

During late June and early July of 2005, signs of bermudagrass ergot were reported from numerous northern and eastern counties in Oklahoma. Signs were observed primarily on forage-type bermudagrass (Cynodon dactylon (L.) Pers.), as well as bermudagrass turf. During the "honeydew" stage, honeydew was frequently observed exuding from most of the ovaries of infected inflorescences. These signs of ergot have been observed previously on bermudagrass in Oklahoma and Texas (1). Sphacelia-type conidia were abundantly produced during the honeydew stage and were single-celled, hyaline, averaged 14 × 5 µm in size, and were reniform to allantoid in shape. When streaked on water agar, conidia produced terminal holoblastic secondary conidia. Single-spore cultures were isolated from the honeydew of bermudagrasses from Logan and Muskogee counties in Oklahoma and grew slowly as white mycelium on potato dextrose agar (PDA). Koch's postulates were fulfilled for these two isolates by spray inoculating four bermudagrass inflorescences at anthesis with mycelium scraped from a PDA plate and homogenized in water. Control plants' inflorescences were sprayed with a water suspension of a similar amount of sterile PDA as inoculated plants. Plants were placed inside plastic bags to maintain humidity and incubated in a growth chamber at 22°C (14-h photoperiod) and 20°C (10 h of darkness). After 9 days, honeydew exuded from the inoculated inflorescences, but not from the controls. Single-spore cultures were reisolated from the honeydew, and conidia streaked on water agar formed identical secondary conidia. The complete nuclear ribosomal internal transcribed spacer (ITS) region was amplified from DNA extracted from honeydew and single-spore cultures using the ITS4 and ITS5 primers (4) and sequenced. All sequences were identical and a search of GenBank at NCBI found these sequences were most similar to the ITS regions of Claviceps cynodontis Langdon (100%, Accession No. AJ557074) and C. maximensis Theis (99%, Accession No. AJ133396). The ITS sequence from the Logan County isolate was deposited at Gen-Bank (Accession DQ187312). The morphology, secondary conidiation, and ITS sequences identify the causal fungus as C. cynodontis (2) and differentiate it from C. purpurea (Fr.) Tul., the previously identified cause of bermudagrass ergot (1). To our knowledge, this is the first report of C. cynodontis on bermudagrass in Oklahoma and may represent a recent introduction to the United States (2; S. Pazoutová and M. Flieger, personal communication). A Claviceps sp. isolated from bermudagrass has been shown to produce ergot alkaloids possibly causing "bermudagrass tremors" in cattle (3). In regions where bermudagrass is the predominant forage for livestock, the toxicological significance of bermudagrass ergot caused by C. cynodontis is unclear and requires further research. References: (1) K. E. Conway et al. Plant Dis. 76:1077, 1992. (2) S. Pazoutová et al. Can J. Plant Pathol. 27:541, 2005. (3) J. K. Porter et al. J. Agric. Food Chem. 22:838, 1974. (4) T. J. White et al. Pages 315-322 in: PCR Protocols: A Guide to Methods and Applications. Academic Press Inc., New York, 1990.

Infrared photodissociation spectroscopy of Mg(+)(H2O)Ar(n) complexes: isomers in progressive microsolvation.

Ion-molecule complexes of the form Mg(H2O)Ar(n)+ (n = 1-8) are produced by laser vaporization in a pulsed-nozzle cluster source. These complexes are mass-selected and studied with infrared photodissociation spectroscopy in the O-H stretch region. The spectra are interpreted with the aid of ab initio calculations on the n = 1-5 complexes, including examination of various isomeric structures. The combined spectroscopic and theoretical studies reveal the presence of multiple isomeric structures at each cluster size, as the argon atoms assemble around the Mg(+)(H2O) unit. Distinct infrared resonances are measured for argon-on-metal, argon-on-OH and argon-on-two-OH isomers.

Growth dynamics and intracluster reactions in Ni+(CO2)n complexes via infrared spectroscopy.

Ni(+)(CO(2))(n), Ni(+)(CO(2))(n)Ar, Ni(+)(CO(2))(n)Ne, and Ni(+)(O(2))(CO(2))(n) complexes are generated by laser vaporization in a pulsed supersonic expansion. The complexes are mass-selected in a reflectron time-of-flight mass spectrometer and studied by infrared resonance-enhanced photodissociation (IR-REPD) spectroscopy. Photofragmentation proceeds exclusively through the loss of intact CO(2) molecules from Ni(+)(CO(2))(n) and Ni(+)(O(2))(CO(2))(n) complexes, and by elimination of the noble gas atom from Ni(+)(CO(2))(n)Ar and Ni(+)(CO(2))(n)Ne. Vibrational resonances are identified and assigned in the region of the asymmetric stretch of CO(2). Small complexes have resonances that are blueshifted from the asymmetric stretch of free CO(2), consistent with structures having linear Ni(+)-O=C=O configurations. Fragmentation of larger Ni(+)(CO(2))(n) clusters terminates at the size of n=4, and new vibrational bands assigned to external ligands are observed for n> or =5. These combined observations indicate that the coordination number for CO(2) molecules around Ni(+) is exactly four. Trends in the loss channels and spectra of Ni(+)(O(2))(CO(2))(n) clusters suggest that each oxygen atom occupies a different coordination site around a four-coordinate metal ion in these complexes. The spectra of larger Ni(+)(CO(2))(n) clusters provide evidence for an intracluster insertion reaction assisted by solvation, producing a metal oxide-carbonyl species as the reaction product.

Infrared photodissociation spectroscopy of V+(CO2)n and V+(CO2)nAr complexes.

V+(CO2)n and V+(CO2)nAr complexes are generated by laser vaporization in a pulsed supersonic expansion. The complexes are mass-selected within a reflectron time-of-flight mass spectrometer and studied by infrared resonance-enhanced (IR-REPD) photodissociation spectroscopy. Photofragmentation proceeds exclusively through loss of intact CO2 molecules from V+(CO2)n complexes or by elimination of Ar from V+(CO2)nAr mixed complexes. Vibrational resonances are identified and assigned in the region of the asymmetric stretch of free CO2 at 2349 cm(-1). A linear geometry is confirmed for V+(CO2). Small complexes have resonances that are blueshifted from the asymmetric stretch of free CO2, consistent with structures in which all ligands are bound directly to the metal ion. Fragmentation of the larger clusters terminates at the size of n=4, and a new vibrational band at 2350 cm(-1) assigned to external ligands is observed for V+(CO2)5 and larger cluster sizes. These combined observations indicate that the coordination number for CO2 molecules around V+ is exactly four. Fourfold coordination contrasts with that seen in condensed phase complexes, where a coordination number of six is typical for V+. The spectra of larger complexes provide evidence for an intracluster insertion reaction that produces a metal oxide-carbonyl species.

Factors Associated with Populations of Plant-Parasitic Nematodes in Bentgrass Putting Greens in Oklahoma.

Numerous genera of plant-parasitic nematodes are frequently present at high populations in golf course putting greens. The objectives of this research were to identify and quantify plant-parasitic nematodes from Oklahoma bentgrass putting greens and to characterize specific soil physical and chemical features and management factors that may account for differences in or associated with the observed nematode populations. In the fall of 2000, nematodes were identified from 99 individual bentgrass putting greens sampled from 46 different locations in Oklahoma. In addition to green age and bentgrass cultivar; soil pH, nitrate-nitrogen (NO3-N), plant-available phosphorus and potassium, organic matter (OM), bulk density, and particle size distribution were determined for each green. Expenditures on management activities, including fertilizer, herbicide, fungicide, and insecticide, were determined for 20 of the sampled courses and compared with nematode populations. Nematodes from seven genera were found in Oklahoma greens, with Criconemella spp. being the most common. Paratrichodorus spp., Tylenchorhynchus spp., and Helicotylenchus spp. also were common. The logarithmic populations of all nematodes combined increased with greater green age (r = 0.37). A negative relationship was observed between soil bulk density and all nematodes combined (r = -0.29). Soil NO3-N, plant-available K, and OM increased with combined logarithmic populations of all plant parasitic nematodes (r = 0.23, 0.28, and 0.37, respectively). A four-factor model accounted for 75% of the total variation in the data and permitted groupings of all variables into four uncorrelated factors. Total logarithmic nematode populations increased with fungicide and herbicide expenditures (r = 0.31). This study suggests that populations of plant-parasitic nematodes may be influenced by the putting green abiotic soil environment and possibly indirectly by management practices on putting greens.

Microwave spectra, geometries, and hyperfine constants of OCCuX (X = F, Cl, Br).

A pulsed jet cavity Fourier transform microwave spectrometer has been used to measure the rotational spectra of OCCuX (X = F, Cl, Br) in the frequency range 5-21 GHz. Metal atoms were generated via laser ablation and were allowed to react with CO and a halide precursor, prior to stabilization of the products within a supersonic jet. These are the first experimental observations of OCCuF and OCCuBr and the first high-resolution spectroscopic study of gas-phase OCCuCl. All three molecules were found to be linear. Rotational constants, centrifugal distortion constants, nuclear quadrupole coupling constants, and nuclear spin-rotation coupling constants have been precisely determined. The rotational constants have been used to evaluate the various bond lengths, and the results are in good agreement with the trend established for OCAuX species. The C-O distance is found to be comparatively short and close to that of free CO. The M-C distance is longer than that predicted by ab initio calculations, and the Cu-X distances are very similar to those observed in the corresponding metal halides. Vibrational wavenumbers have been estimated from the distortion constants and are compared with the results of various ab initio studies. Changes in the Cu, Cl, and Br nuclear quadrupole coupling constants indicate that substantial charge rearrangement takes place on coordination with CO, consistent with the formation of strong Cu-C bonds. Mulliken orbital population analyses have been performed and provide evidence of pi-back-donation from Cu in all of the species studied. The evaluated nuclear spin-rotation coupling constants have been used to estimate the (63)Cu nuclear shielding constants, sigma, and their spans (Omega) in OC(63)CuF, OC(63)Cu(35)Cl, and OC(63)Cu(79)Br.

Comparisons in the behavior of stable copper(II), silver(II), and gold(II) complexes in the gas phase: are there implications for condensed-phase chemistry?

Experiments conducted in the gas phase have led to the formation of a series of stable gold(II) complexes with nitrogen- and oxygen-containing ligands. Such complexes are very rare in condensed-phase chemistry. However, there is also a significant group of potential ligands, for example, H2O and NH3, for which stable complexes could not be formed. There are strong similarities between these observations and earlier results presented for silver(II), but both metal ions behave markedly different from copper(II). As a group the majority of successful gold(II) ligands are characterized by being good sigma donor-pi acceptor molecules; however, it is also possible to understand the ability of individual ligands to stabilize the metal ion in terms of a simple electrostatic model. Application of the latter reveals a semiquantitative trend between the physical properties of a ligand, e.g. ionization energy, dipole moment, and polarizability, and the ligand's ability to stabilize either Cu(II), Ag(II), or Au(II). The model successfully accounts for the preference of Cu(II) for aqueous chemistry, in comparison to the complete absence of such behavior on the part of Ag(II) and Au(II). Ligands from recent examples of stable condensed-phase gold(II) complexes appear to meet at least one of the criteria identified from the model.

Influence of Meloidogyne incognita and Thielaviopsis basicola Populations on Early-Season Disease Development and Cotton Growth.

Microplot studies were used to examine the effect of various population densities of Meloidogyne incognita and Thielaviopsis basicola on cotton-plant development and disease severity. Plots were infested with 0, 20, or 100 T. basicola chlamydospores/g and 0, 5, or 10 M. incognita eggs and juveniles/cm3 of soil in a factorial arrangement in 1997 and 1998. Combinations of M. incognita and T. basicola reduced plant survival in both years compared to the noninfested control, except in 1998 for the high rate of T. basicola over all nematode rates. Plant height-to-node ratios were reduced by pathogen combinations compared to the noninfested control or to either pathogen alone. Plant dry weight was reduced by M. incognita in 1998 and the high rate of T. basicola in 1997. Root necrosis was increased by increasing rates of T. basicola in 1997 and by M. incognita over all rates of T. basicola in both years. Colonization of root tissue by T. basicola was increased by the low inoculum density of the nematode at 20 CFU/g soil in 1997 and 100 CFU/g in 1998. Nematode reproduction with the high M. incognita treatment rate was reduced in both years of the study by the high T. basicola rate. This study suggests the importance of population level of each pathogen to the severity of disease and confirms the potential of this disease interaction to impact cotton production.

Effect of Temperature on and Histopathology of the Interaction Between Meloidogyne incognita and Thielaviopsis basicola on Cotton.

ABSTRACT Controlled environments were used to study the relationship between the root-knot nematode (Meloidogyne incognita) and Thielaviopsis basicola on cotton. Temperature treatments were continuous 20, 24, and 28 degrees C or two cyclic linear regimes with ranges of 14 to 32 or 18 to 28 degrees C over 24 h. Cotton seeds were planted in fumigated soil infested with T. basicola, M. incognita, or both. After 42 days, pathogen effects on plant growth and pathogen development were evaluated. Histology was conducted on roots collected 14, 28, and 42 days after planting in the continuous 24 degrees C treatment. Reductions in plant height-to-node ratio and total fresh weight were observed for soils infested with both pathogens compared with the control or with soils infested with either pathogen, except for M. incognita-infested soil at 28 degrees C. T. basicola reduced root galling and reproduction of the nematode at all temperatures. Vascular discoloration caused by T. basicola was greater in the presence of M. incognita compared with that by T. basicola alone. At 2 and 4 weeks, histological studies showed that plants grown in all T. basicola-infested soils contained chlamydospore chains on the root surface and in cortical cells. The fungus was not observed inside the vascular cylinder. Roots from 4-week-old plants from soils infested with T. basicola and M. incognita showed fungal sporulation in vascular tissue and localized necrosis of vascular tissue adjacent to the nematodes. At 6 weeks, plants grown in soil infested with T. basicola alone exhibited no remaining cortical tissue and no evidence of vascular colonization by the fungus. Six-week-old plants grown in T. basicola + M. incognita-infested soils exhibited extensive vascular necrosis and sporulation within vascular tissue. These studies suggest that coinfection expands the temperature ranges at which the pathogens are able to cause plant damage. Further, M. incognita greatly increases the access of T. basicola to vascular tissue.

Interaction Between Meloidogyne incognita and Thielaviopsis basicola on Cotton (Gossypium hirsutum).

The effects of Meloidogyne incognita and Thielaviopsis basicola on the growth of cotton (Gossypium hirsutum) and the effects of T. basicola on M. incognita populations were evaluated in a 2-year study. Microplots were infested with M. incognita, T. basicola, or a combination of M. incognita and T. basicola. Uninfested plots served as controls both years. Seedling survival was decreased by the M. incognita + T. basicola treatment compared to the control. Meloidogyne incognita alone and M. incognita + T. basicola reduced plant height-to-node ratio for seedlings in both years. Seed cotton yield was reduced, and the length of time required for boll maturation was lengthened by M. incognita + T. basicola in 1994 and M. incognita both alone and with T. basicola in 1995. Position of the first sympodial node on the main stem was increased by M. incognita in both years and was higher for plants treated with M. incognita + T. basicola in 1995 in comparison to the control. The number of sympodial branches with bolls in the first and second fruiting position and the percentage of bolls retained in the second position were reduced both years by M. incognita + T. basicola compared to either the control or T. basicola alone. Orthogonal contrasts indicated that effects on height-to-node ratio, number of days to first cracked boll, and yield were significantly different for combined pathogen inoculations than with either pathogen alone. Meloidogyne incognita eggs at harvest were reduced by T. basicola in 1994 and 1995 compared to M. incognita alone. The study demonstrated a significant interaction between M. incognita and T. basicola on cotton that impacted the survival and development of cotton and the reproduction of M. incognita on cotton.

Seven-year follow-up of a smoking-prevention program for children.

Smoking-prevention programs, run by both teachers, and teachers and peers, have been introduced into school curricula in many parts of the world. This paper describes a long-term follow-up of a randomised controlled trial of a smoking education program for children conducted in Western Australia. Seven years after the first survey of 2,366 Year 7 students in 1981, 68 per cent of initial participants were traced through public records; 53 per cent of these responded to a new survey concerning smoking. Previous follow-up after one and two years had shown that both teacher-led and peer-led programs continued to reduce the taking up of smoking by girls to about the same degree, whereas in boys, the teacher-led program appeared to be effective after one year but neither program was effective after two years. In nonsmoking girls, both the intervention programs maintained their effects at the seven-year follow-up, with an almost 50 per cent reduction in smoking prevalence in the intervention group. Nonsmoking girls appeared to respond to cigarette advertisements. Mothers seemed to influence nonsmokers of both sexes and brothers seemed to influence smokers of both sexes. The seven-year follow-up confirmed the results seen at two years for boys, that the effects of the education program had dissipated. However, this study suggests that the smoking-prevention program had a lasting effect on preventing girls from taking up smoking.