Naturally occurring substitution of an amino acid in a plant virus gene-silencing suppressor enhances viral adaptation to increasing thermal stress

Cereal yellow dwarf virus (CYDV-RPV) encodes a P0 protein that functions as a viral suppressor of RNA silencing (VSR). The strength of silencing suppression is highly variable among CYDV-RPV isolates. In this study, comparison of the P0 sequences of CYDV-RPV isolates and mutational analysis identified a single C-terminal amino acid that influenced P0 RNA-silencing suppressor activity. A serine at position 247 was associated with strong suppressor activity, whereas a proline at position 247 was associated with weak suppressor activity. Amino acid changes at position 247 did not affect the interaction of P0 with SKP1 proteins from Hordeum vulgare (barley) or Nicotiana benthamiana. Subsequent studies found P0 proteins containing a P247 residue were less stable than the P0 proteins containing an S247 residue. Higher temperatures contributed to the lower stability and in planta and the P247 P0 proteins were subject to degradation via the autophagy-mediated pathway. A P247S amino acid residue substitution in P0 increased CYDV-RPV replication after expression in agroinfiltrated plant leaves and increased viral pathogenicity of P0 generated from the heterologous Potato virus X expression vector system. Moreover, an S247 CYDV-RPV could outcompete the P247 CYDV-RPV in a mixed infection in natural host at higher temperature. These traits contributed to increased transmission by aphid vectors and could play a significant role in virus competition in warming climates. Our findings underscore the capacity of a plant RNA virus to adapt to climate warming through minor genetic changes in gene-silencing suppressor, resulting in the potential for disease persistence and prevalence.

Timings of major glaciations, inherent selection schemes and the origins of cold hardy animal phyla

　　BACKGROUND: Knowing the origin dates of specific phyla may help in understanding the intricate relationships between environments and their biota. Past extreme environments would have challenged biota and led to the evolution of phyla that were and possibly still are able to withstand extreme conditions.

OBJECTIVE

We test the hypothesis that major glaciation events imposed strong selection schemes, ultimately leading to the origins of cold hardy phyla.

METHODS

We identified dates of past major glaciation events, cold hardy phyla and their origin dates and synthesized these data in a phylogenetic context.

RESULTS

Origin dates of cold hardy phyla do not correspond with major glaciation events, falsifying the hypothesis.

CONCLUSION

An alternative hypothesis is proposed in which varying degrees of cold hardiness evolved at other taxonomic levels within these phyla.

Rapid full-length cloning of nonpolyadenylated RNA virus genomes

Access to a full-length infectious clone of a viral genome is a virtual necessity for research aimed at understanding virus replication and gene expression mechanisms. While construction of a full-length clone may be straightforward, obtaining one that is infectious is by no means routine. Here the authors describe methods to maximize the likelihood of obtaining a full-length infectious clone. These include protocols to (1) sequence the ends of nonpolyadenylated RNA genomes, (2) obtain a full-length PCR product in a single reaction directly from viral RNA, and (3) efficiently clone the PCR product into a vector that allows in vitro transcription of viral RNA containing perfect or near-perfect termini. Given the traditional difficulty of obtaining infectious clones of RNA genomes (especially of nonpolyadenylated RNA viruses), this unit should be valuable to all virologists working with nonpolyadenylated as well as polyadenylated viruses of plants and animals.

A baculovirus-expressed dicistrovirus that is infectious to aphids

Detailed investigation of virus replication is facilitated by the construction of a full-length infectious clone of the viral genome. To date, this has not been achieved for members of the family Dicistroviridae. Here we demonstrate the construction of a baculovirus that expresses a dicistrovirus that is infectious in its natural host. We inserted a full-length cDNA clone of the genomic RNA of the dicistrovirus Rhopalosiphum padi virus (RhPV) into a baculovirus expression vector. Virus particles containing RhPV RNA accumulated in the nuclei of baculovirus-infected Sf21 cells expressing the recombinant RhPV clone. These virus particles were infectious in R. padi, a ubiquitous aphid vector of major cereal viruses. The recombinant virus was transmitted efficiently between aphids, despite the presence of 119 and 210 vector-derived bases that were stably maintained at the 5' and 3' ends, respectively, of the RhPV genome. The maintenance of such a nonviral sequence was surprising considering that most RNA viruses tolerate few nonviral bases beyond their natural termini. The use of a baculovirus to express a small RNA virus opens avenues for investigating replication of dicistroviruses and may allow large-scale production of these viruses for use as biopesticides.

Barley yellow dwarf virus: Luteoviridae or Tombusviridae?

Summary Barley yellow dwarf virus (BYDV), the most economically important virus of small grains, features highly specialised relationships with its aphid vectors, a plethora of novel translation mechanisms mediated by long-distance RNA interactions, and an ambiguous taxonomic status. The structural and movement proteins of BYDV that confer aphid transmission and phloem-limitation properties resemble those of the Luteoviridae, the family in which BYDV is classified. In contrast, many genes and cis-acting signals involved in replication and gene expression most closely resemble those of the Tombusviridae.

TAXONOMY

BYDV is in genus Luteovirus, family Luteoviridae. BYDV includes at least two serotypes or viruses: BYDV-PAV and BYDV-MAV. The former BYDV-RPV is now Cereal yellow dwarf virus-RPV (CYDV-RPV). CYDV is in genus Polerovirus, family Luteoviridae. Genus Luteovirus shares many features with family Tombusviridae. Physical properties: approximately 25 nm icosahedral (T = 3) virions. One major (22 kDa) and one minor (50-55 kDa) coat protein. 5.6-5.8 kb positive sense RNA genome with no 5'-cap and no poly(A) tail.

HOST RANGE

Most grasses. Most important in oats, barley and wheat. Also infects maize and rice.

SYMPTOMS

Yellowing and dwarfing in barley, stunting in wheat; reddening, yellowing and blasting in oats. Some isolates cause leaf notching and curling. Key attractions: Model for the study of circulative transmission of aphid-transmitted viruses. Plethora of unusual translation mechanisms. Evidence of recombination in recent evolutionary history creates taxonomic ambiguity. Economically important virus of wheat, barley and oats, worldwide. Useful websites/meetings: International symposium: 'Barley Yellow Dwarf Disease: Recent Advances and Future Strategies', CIMMYT, El Batan, Mexico, 1-5 September 2002, http://www.cimmyt.cgiar.org/Research/wheat/Conf_BYD_02/invitation.htm http://www.cimmyt.org/Research/wheat/BYDVNEWS/htm/BYDVNEWS.htm Aphid transmission animation: http://www.ppws.vt.edu/~sforza/tmv/bydv_aph.html.

The 3prime prime or minute-terminal structure required for replication of Barley yellow dwarf virus RNA contains an embedded 3prime prime or minute end

We determined the 3prime prime or minute-terminal primary and secondary structures required for replication of Barley yellow dwarf virus (BYDV) RNA in oat protoplasts. Computer predictions, nuclease probing, phylogenetic comparisons, and replication assays of specific mutants and chimeras revealed that the 3prime prime or minute-terminal 109 nucleotides (nt) form a structure with three to four stem-loops followed by a coaxially stacked helix incorporating the last four nt [(A/U)CCC]. Sequences upstream of the 109-nt region also contributed to RNA accumulation. The base-pairing but not the sequences or bulges in the stems were essential for replication, but any changes to the 3prime prime or minute-terminal helix destroyed replication. The two 3prime prime or minute-proximal tetraloops tolerated all changes, but the two 3prime prime or minute-distal tetraloops gave most efficient replication if they fit the GNRA consensus. A mutant lacking the 3prime prime or minute-proximal stem-loop produced elevated levels of less-than-full-length minus strands, and no (+) strand. We propose that a "pocket" structure is the origin of (minus sign)-strand synthesis, which is negatively regulated by the inaccessible conformation of the 3prime prime or minute terminus, thus favoring a high (+)/(minus sign) ratio. This 3prime prime or minute structure and the polymerase homologies suggest that genus Luteovirus is more closely related to the Tombusviridae family than to other Luteoviridae genera.

Fate and toxicity of endosulfan in Namoi River water and bottom sediment

Endosulfan (6,7,8,9,10,10,-hexachloro-1,5,5a,6,9,9a-hexahydro-6,9-methano-2,4,3-benzodioxathiepine-3-oxide) sorption (standardized to 1% total organic carbon and dry weight) was significantly (P < 0.05) more concentrated on the large (>63 microm) particle fraction compared with smaller size fractions (<5 microm and 5-24 microm) of bottom sediments from the Namoi River, Australia. Following completion of the particle size fractionation (6 to 12 wk) and a sediment toxicity assessment (2 wk), the sediments showed large decreases in concentrations of alpha-endosulfan that coincided with an increase in endosulfan sulfate concentrations and minimal changes in beta-endosulfan concentrations. In the Namoi River, similar patterns were observed in the composition of total endosulfan in monthly measurements of bottom sediments and in passive samplers placed in the water column following runoff from cotton (Gossypium hirsutum L.) fields. The toxicity of endosulfan sulfate in river water indicated by the nymphs of the epibenthic mayfly Jappa kutera, was more persistent than the alpha- and beta-endosulfan parent isomers due to its longer half-life. This suggests that endosulfan sulfate would contribute most to previously observed changes in population densities of aquatic biota. Measured concentrations of total endosulfan in river water of up to 4 microg L(-1) following storm runoff, exceed the range of the 96-h median lethal concentration (LC50) values in river water for both alpha-endosulfan (LC50 = 0.7 microg L(-1); 95% confidence interval [CI] = 0.5 to 1.1) and endosulfan sulfate (LC50 = 1.2 microg L(-1); 95% CI = 0.4 to 3.3). In contrast, the 10-d LC50 value for total endosulfan in the sediment toxicity test (LC50 = 162 microg kg(-1); 95% CI = 120 to 218 microg kg(-1)) was more than threefold higher than the highest measured concentration of total endosulfan in field samples of bottom sediment (48 microg kg(-1)). This suggests that pulse exposures of endosulfan in the water column following storm runoff may be more acutely toxic to riverine biota than in contaminated bottom sediment.

Determination of total and EDTA extractable metal distributions in the colloidal fraction of contaminated soils using SdFFF-ICP-HRMS

Newly developed methods involving an on-line combination of sedimentation field-flow fractionation-inductively coupled plasma-high resolution mass spectrometry (SdFFF-ICP-HRMS) have been used to study the distributions of extractable heavy metals in a soil which had been treated with sewage sludge contaminated with Cu or Pb. The relationship of these metals with other elements in the colloidal fraction was also investigated. The colloidal fraction from the soil was obtained by repeated gravitational sedimentation and extracted with 0.11 M acetic acid, 0.1 M hydroxylamine hydrochloride, 0.05 M ethylenediaminetetraacetic acid disodium salt (EDTA) or aqua regia to assess the potential availability of the metals Cu and Pb. Large proportions of the Cu and Pb were extracted by EDTA, approaching that removed by aqua regia, whereas < 10% of the aqua regia extractable metals were removed by acetic acid and hydroxylamine chloride. The distributions of the heavy metals, the major mineral forming element (Al) and the elements forming sesquioxides (Fe and Mn) within different size classes (0.05-1 microm) of the colloidal fraction were measured using SdFFF-ICP-HRMS before and after extraction with EDTA. This information provides an insight into the composition of the colloids and the distributions of metal contaminants. In the contaminated soil colloids, the concentration of Fe, Mn and Pb is greatest in the smaller particles (<0.2 microm). In contrast, the Cu concentration is constant over the size range studied. Iron oxide surface coatings probably play a significant role in Pb adsorption on soil particles, but may be less important for Cu. The combination of selective chemical extraction, SdFFF and ICP-HRMS provides a means of determining the distribution of potentially available heavy metals within the colloidal fraction of contaminated soils.

The effect of surface coatings on the association of orthophosphate with natural colloids

A new method has been utilised for the characterisation of natural particle surface coatings. The method involves the use of sedimentation field-flow fractionation (SdFFF), radiolabelling and inductively coupled plasma-high resolution mass spectrometry (ICP-HR MS) techniques to study the effect of colloidal surface coatings on the adsorptive behaviour of orthophosphate. Colloidal river sediment and soil samples were chemically treated in an attempt to selectively remove metal hydroxyoxides and natural organic matter. The samples were then radiolabelled with 33PO4(3-) and analysed by SdFFF to determine the surface adsorption density (SAD) of orthophosphate as a function of particle size. The SdFFF unit was directly coupled to an ICP-HR MS to determine the chemical composition of the colloidal samples as a function of particle size. Element concentration/UV detector signal and element atomic molar ratios were plotted against particle size, and the trends used in the interpretation of SAD distribution (SADD) changes for the samples were studied. In general, non-constant trends in the orthophosphate SADDs were found, except for the river sediment treated with hydroxylamine hydrochloride. The results indicated that, in the soil sample studied, the Mn oxide coating was a dominant factor in determining phosphorus adsorption. This method could also be applicable to other industrial or similar samples.

Fractionation and composition of colloidal and suspended particulate materials in rivers

The association of pollutants (nutrients, heavy metals and organic compounds) with colloidal and suspended particle matter (SPM) plays a dominant role in determining their transport, fate, biogeochemistry, bioavailability and toxicity in natural waters. A scheme for the fractionation and composition of colloidal and SPM from river waters has been tested. All four separation methods, i.e. sieving, continuous flow centrifugation, tangential flow filtration, sedimentation field-flow fractionation, were for the first time used to separate five size particulate fractions from river. Significant (gram) amounts of colloidal material (<1 microm) in three size ranges, nominally 1-0.2, 0.2-0.006 and 0.006-0.003 microm were obtained. The separation scheme was able to process large samples (100 l), within reasonable times (1 day) and the apparatus was portable. The aquatic colloid size was also characterized with high resolution by using sedimentation field-flow fractionation technique. The mass-based particle size distribution for the water sample showed a broad size distribution between 0.05 and 0.4 microm with the maximum around 0.14 microm. There was a systematic increase in the content of organic carbon (estimated by loss on ignition), Mg, Ca, Na, Cu and Zn with decreasing particle size, highlighting the importance of the colloidal (<1 microm) fraction. It was concluded that the colloidal Cu and Zn concentrations in rivers might be much higher than those reported before.

An exploration of child sexual abusers' sexual fantasies before and after treatment

Although there is a substantial literature looking at the relationship between deviant sexual fantasies and child sexual abuse, there is scant previous work that focuses upon the actual content of such fantasies. The present study looks at child sexual abusers' deviant fantasies both pre- and postintervention. Using both qualitative and quantitative methodologies, a description of the frequency and content of, and triggers for, child sexual abusers' deviant fantasies is reported both pre- and postintervention. The implications of this information for subsequent intervention programs is explored.

[Psychiatric rehabilitation in a secure treatment setting]

Working with severely mentally ill persons within the locked environment of a secure residential treatment facility presents a provocative challenge in attempting to establish a rehabilitative program. The author describes the mission, goals and methods of one of Oregon's newly organized facilities for "hard to place" former state hospital patients. The value of teaching the residents self-control is emphasized. Clinical vignettes illustrate how the staff involve the residents in real-life tasks, apply natural consequences to problem behaviors, and make attempts at minimizing the potential sources of confrontation.

[Training in preventing assaultive behaviors for psychiatric professionals]

Dangerous behaviors in psychiatric institutions constitute major clinical and administrative problems. Staff competency in dealing with assaultive patients is an important factor in reducing institutional violence. One of the training programs for mental health staff working with dangerous patients is called Professional Assault Response Training (PART). PART is a product of several years of experience accumulated by the group of California authors in their efforts at designing a safe and effective approach in responding to various dangerous behaviors. PART principles guide staff in 1) de-escalating dangerous incidents through verbal crisis interventions; 2) avoiding or minimizing the risk of minor physical injury through evasion; 3) preventing serious bodily harm through the use of manual restraint. The importance of maintaining self-control by staff is reinforced throughout the entire course as a crucial professional skill. Other PART principles include identifying realistic treatment expectations for assaultive patients, proper physical mobility and emotional balance of staff, recognizing warning signals of impeding danger, using reasonable force to match response to the level of dangerousness. The PART training explores various theoretical explanations of violence (legal model, stress model, environmental model, communication model, developmental model, basic needs model and common-sense model). Verbal interventions which are a cornerstone of the PART approach are matching specific motives of threatening behavior--fear, frustration, manipulation and intimidation. Physical interventions taught in the course (evasion and manual restraint) include only techniques which can be used safely and which are not pain inducing. Finally, the PART training also assists staff in properly documenting assaultive incidents.

Long-term follow-up in the Peer Assessment Program for nonspecialist physicians in Ontario, Canada

BACKGROUND

The College of Physicians and Surgeons of Ontario has assessed randomly selected physician office practices since 1972. Each assessment consists of a tour of the premises and a review of a random selection of 20 to 30 medical records to evaluate the system of record keeping and the content of the records and to thereby indicate the quality of the physician's examinations, history taking, diagnosis and management plan. About 12% of nonspecialist physicians who need help to improve their records and/or the care they provide are identified annually, and following an interview with peers and simple educational interventions, more than 75% are successful in improving.

METHODS

A follow-up was conducted to assess physician practices an average of six years after the first intervention. The reviewers were blinded as to whether the physician being reviewed had been reviewed previously. Each revisited physician was matched to three others undergoing their initial assessments in the same year. The matching variables were age, sex, school of graduation (Canadian versus other), rural versus urban practice location, and affiliation status with the College of Family Physicians of Canada. The assessed performance of the two groups was compared.

RESULTS

The performance of the revisit group was significantly better than that of the matched group (p = 0.05).

CONCLUSIONS

The assessment, interview, and educational interventions undertaken by the licensing authority produced an improvement in practice in the short term in the bottom 10%-15% of all physicians reviewed, which was sustained for more than six years.

Entropic Contribution to the Retention of Nonspherical Particles in Field-Flow Fractionation

In this paper the effect of particle shape on the entropy of nonspherical particles adjacent to a plane surface is considered. The subsequent influence on particle retention in field-flow fractionation (FFF) has been estimated. New retention equations for thin rod and disc shaped particles have been derived to cover this steric-entropic region of FFF. As particle size increases relative to the mean cloud thickness, the retention ratio for nonspherical particles is predicted to increase compared to small spherical particles of the same mass. This could result in a significant underestimation of the calculated equivalent spherical diameter (d) by FFF methods. The steric-entropic FFF equations could be used to calculate accurate d values if the large particle dimension is estimated independently (e.g., by microscopy). Alternatively, run conditions could be designed to minimize steric-entropic perturbations to the ideal retention equation.

Steroid injection for carpal tunnel syndrome

We studied the medium- to long-term results of steroid injection into the carpal tunnel of women with the carpal tunnel syndrome (CTS). Of 45 hands, only 11 had lasting relief of symptoms and 22 had no relief whatsoever. There was no correlation of the typical signs and symptoms of CTS with outcome. Other series have offered various predictive factors for the outcome of injection but we found little or no correlation between these factors and outcome.

Variations in the fluorescence intensity of intact DAPI-stained bacteria and their implications for rapid bacterial quantification

As current techniques for the quantification of bacteria are laborious and often imprecise, instrumental approaches such as sedimentation field-flow fractionation (SdFFF) are attractive. In this technique, fluorogenic dyes specific for nucleic acids are used to identify bacterial cells. Bacterial biomass can be quantified directly with SdFFF if the specific fluorescence of bacterial cells is constant. The effect of different growth conditions on the specific fluorescence of one strain each of Escherichia coli, Pseudomonas aeruginosa, Proteus mirabilis and Staphylococcus epidermidis stained with 4',6-diamidino-2-phenylindole was examined. Specific fluorescence varied over a 500-fold range, from 0.22 to 103 arbitrary fluorescence units per cell. Specific fluorescence was highest when cells were in log phase, and lowest when cells were in stationary phase. Specific fluorescence decreased when cells harvested in log phase were starved for 7 d in a carbon-free minimal medium, and increased rapidly (within 2 h) after cells were relieved from carbon limitation. Such variations in specific fluorescence must be considered when using gross fluorescence as a direct indicator of bacterial numbers in the SdFFF technique for quantifying bacterial biomass. Moreover, they have serious implications for the application of fluorescence techniques in other instrumental approaches for bacterial enumeration in environmental samples.

Physical Characterization and Quantification of Bacteria by Sedimentation Field-Flow Fractionation

Studies in microbial ecology require accurate measures of cell number and biomass. Although epifluorescence microscopy is an accepted and dependable method for determining cell numbers, current methods of converting biovolume to biomass are error prone, tedious, and labor-intensive. This paper describes a technique with sedimentation field-flow fractionation to enumerate bacteria and determine their density, size, and mass. Using cultured cells of different shapes and sizes, we determined optimum values for separation run parameters and sample-handling procedures. The technique described can separate and detect 4′, 6-diamidino-2-phenylindole-stained cells and generate a fractogram from which cell numbers and their size or mass distribution can be calculated. A direct method for estimating bacterial biomass (dry organic matter content) which offers distinct advantages over present methods for calculating biomass has been developed.

A trial of two cognitive-behavioural methods of treating drug-resistant residual psychotic symptoms in schizophrenic patients: I. Outcome

Despite neuroleptic medication, many schizophrenic patients continue to experience residual positive psychotic symptoms. These residual symptoms cause distress and disability. We report a controlled trial of two cognitive-behavioural treatments to alleviate residual hallucinations and delusions. Forty-nine patients were recruited into the trial, of whom 27 entered the trial and completed post-treatment assessment, and 23 were reassessed at six-month follow-up. Patients were randomly allocated to either coping strategy enhancement (CSE) or problem solving (PS). Half the patients were allocated to a high-expectancy positive demand condition and half to a counter-demand condition to evaluate expectation of improvement. Patients receiving either cognitive-behavioural treatment showed significant reductions in psychotic symptoms compared with those in the waiting period, who showed no improvement. There was some evidence, although equivocal, that patients receiving CSE improved more than those receiving PS. There was no evidence that improvements generalised to negative symptoms or social functioning, nor was there evidence that expectancy of treatment benefit contributed to the treatment effect.

A trial of two cognitive behavioural methods of treating drug-resistant residual psychotic symptoms in schizophrenic patients. II. Treatment-specific changes in coping and problem-solving skills

Changes in coping skills and problem-solving skills were examined in two groups of schizophrenic patients. The groups received either coping skills enhancement or problem-solving treatments to reduce their drug-resistant residual psychotic symptoms. The coping skills group showed significant increases both in the number of positive coping strategies used and in their efficacy, whereas the problem-solving group showed a decrease in these measures during treatment. Both groups showed significant improvements in problem-solving skills. Changes in coping but not problem solving were significantly related to decreases in psychotic symptoms during treatment. It was concluded that treatment involving the teaching of coping skills had a specific treatment effect.

Morbid jealousy: a review and cognitive-behavioural formulation

Jealousy is a common emotion which can be considered pathological in some circumstances. The term ‘morbid jealousy’ has been used to signify this abnormal or extreme condition. However, the literature on morbid jealousy is sparse and the empirical data fragmentary. The aims of this paper are to briefly review the concept, to define the dimensions of the disorder and to apply a cognitive-behavioural framework to it. Such a summary paper is timely, to draw together the different aspects of the problem and to provide a theoretical base from which to generate further research.

Mating activity of Nematospiroides dubius in laboratory mice

Incidence of mating pairs in 40 worm infections in 5 week old female CBA mice increased up to day 30 post infection. By this time, and thereafter until the experiment ended on day 70, approximately 60% of the worm population occurred as mating pairs. Mating began during the ontogenetic migration of the worms. There was no difference between the percentage of worms mating in the more highly populated anterior sections of the small intestine as compared to the less densely populated more posterior sections. Significantly more female than male worms were recovered between days 8 and 20 post infection (P < 0.02 to 0.001) and there was a significant decline in overall recoveries during the experimental period (r = -0.77, P < 0.01). Low intensity infections, with 4 to 16 worms per mouse, demonstrated that a larger percentage of worms in the infection were mating at an earlier time post infection than in the 40 worm infections. Ontogenetic migration was reduced in low intensity infections because the initial distribution of worms was more restricted.

An electron spin resonance study of (N-2-Pyridylsalicylaldiminato)copper(II) nitrate

The magnetic susceptibility of (N-2-pyridylsalicylaldiminato)copper(II) nitrate and chloride has been measured at room temperature and 97 K. Contrary to results reported previously we find no evidence for the presence of magnetic exchange interactions in these compounds. Electron spin resonance spectral data on the ethanol-dimethylformamide solutions of the chelates show that the chelates are monomeric in the liquid phase but largely in dimeric form in frozen solution. Computer simulation of the experimental e.s.r. spectra due to the dimeric form has enabled a determination of the symmetry arrangement and structural properties of the pair system to be made.

Magnetism and structure of a novel trinuclear cluster compound of divalent copper

The magnetic properties of a series of salts of the type [Cu3L3OH]2+ (where HL is pyridine-2-aldehyde oxime and L is the deprotonated ligand) have been examined. All of the compounds showed a magnetic moment of 1.00 B.M. per copper atom over a wide temperature range which suggests that the cation contains a trinuclear cluster of interacting copper atoms. The crystal structure of Cu3L3OH(SO4),xH2O has been determined by single- crystal X-ray diffraction techniques and confirms that the complex does indeed contain an unusual type of trinuclear cluster of metal atoms. The three copper atoms form an equilateral triangle and the sulphato group exhibits a highly novel ?tripod? bridging function to the Cu3 triangle. On the other side of the triangle, the hydroxyl group also bridges to all the metal atoms. A qualitative molecular orbital analysis not only suggests that the hydroxyl group is involved in four-centre bonding with the Cu3 triads, but also highlights its role in reducing the spin of the trimer so that only a doublet ground state is populated between 80-300�K. However, the alternative super-exchange mechanism cannot be ruled out by the magnetic and structural data.

The Thermal Decomposition of Thorium Oxalate

The thermal decomposition of hydrated thorium oxalate was followed by determining weight loss, change in electrical conductivity, and chemical composition of products. At temperatures below 200�C. the weight-loss curve indicated the existence of a tri- and a dihydrate and possibly a pentahydrate of thorium oxalate as stages m the dehydration. At higher temperatures dehydration was accompanied by loss of CO and CO2. Almost all the (C2O4)= decomposed sharply over a small temperature range near 300�C. Although some carbonate was formed, it did not exceed a concentration of 0.076 mole per mole of total thorium. According to chemical analysis the residue after heating at 350�C. was ThO2 with a trace of carbonate and water. X-ray analysis, however, showed it to be a mixture of ThO2, and a second substance whose identity is unknown. In the electron microscope the hydrated oxalate and the thoria produced from it were little different in appearance. Both appeared as relic crystals which were square prisms about l μ across and 0.2 μ thick, with a characteristic central aperture which exposed a large area of surface.