Dark Matter Search Results from the PICO-60 C_{3}F_{8} Bubble Chamber

New results are reported from the operation of the PICO-60 dark matter detector, a bubble chamber filled with 52 kg of C_{3}F_{8} located in the SNOLAB underground laboratory. As in previous PICO bubble chambers, PICO-60 C_{3}F_{8} exhibits excellent electron recoil and alpha decay rejection, and the observed multiple-scattering neutron rate indicates a single-scatter neutron background of less than one event per month. A blind analysis of an efficiency-corrected 1167-kg day exposure at a 3.3-keV thermodynamic threshold reveals no single-scattering nuclear recoil candidates, consistent with the predicted background. These results set the most stringent direct-detection constraint to date on the weakly interacting massive particle (WIMP)-proton spin-dependent cross section at 3.4×10^{-41}  cm^{2} for a 30-GeV c^{-2} WIMP, more than 1 order of magnitude improvement from previous PICO results.

Differentiation and growth of bone ornamentation in vertebrates: a comparative histological study among the Crocodylomorpha

Bone ornamentation, that is, hollow (pits and grooves) or protruding (ridges) repetitive reliefs on the surface of dermal bones, is a frequent, though poorly studied and understood, feature in vertebrates. One of the most typical examples of this characteristic is given by the Crurotarsi, a taxon formed by the crocodilians and their closest allies, which generally display deep ornamentation on skull roof and osteoderms. However, the ontogenetic process responsible for the differentiation and development of this character remains controversial. This study was conducted to settle the question on histological and microanatomical evidence in several crurotarsan taxa. Observational and experimental data in extant and extinct crocodyliforms show that bone ornamentation is initially created, and later maintained during somatic growth (that is indefinite in crocodilians), by a complex process of bone remodeling comprising local resorption of superficial bone cortices, followed by partial reconstruction. The superficial reliefs of crocodilian dermal bones are thus permanently modified through pit enlargement, drift, stretching, shrinking, or complete filling. Ridges are also remodeled in corresponding ways. These processes allow accommodation of unitary ornamental motifs to the overall dimensions of the bones during growth. A parsimony optimization based on the results of this study, but integrating also published data on bone histology in non-crocodyliform crurotarsans and some non-crurotarsan taxa, suggests that the peculiar mechanism described above for creating and maintaining bone ornamentation is a general feature of the Crurotarsi and is quite distinct from that attributed by previous authors to other vertebrates.

Impaired cell death and mammary gland involution in the absence of Dock1 and Rac1 signaling

Throughout life, the tight equilibrium between cell death and the prompt clearance of dead corpses is required to maintain a proper tissue homeostasis and prevent inflammation. Following lactation, mammary gland involution is triggered and results in the death of excessive epithelial cells that are rapidly cleared by phagocytes to ensure that the gland returns to its prepregnant state. Orthologs of Dock1 (dedicator of cytokinesis 1), Elmo and Rac1 (ras-related C3 botulinum toxin substrate 1) in Caenorhabditis elegans are part of a signaling module in phagocytes that is linking apoptotic cell recognition to cytoskeletal reorganization required for engulfment. In mammals, Elmo1 was shown to interact with the phosphatidylserine receptor Bai1 and relay signals to promote phagocytosis of apoptotic cells. Still, the role of the RacGEF Dock1 in the clearance of dying cells in mammals was never directly addressed. We generated two mouse models with conditional inactivation of Dock1 and Rac1 and revealed that the expression of these genes is not essential in the mammary gland during puberty, pregnancy and lactation. We induced mammary gland involution in these mice to investigate the role of Dock1/Rac1 signaling in the engulfment of cell corpses. Unpredictably, activation of Stat3 (signal transducer and activator of transcription 3), a key regulator of mammary gland involution, was impaired in the absence of Rac1 and Dock1 expression. Likewise, failure to activate properly Stat3 was coinciding with a significant delay in the initiation and progression of mammary gland involution in mutant animals. By using an in vitro phagocytosis assay, we observed that Dock1 and Rac1 are essential to mediate engulfment in epithelial phagocytes. In vivo, cell corpses accumulated at late time points of involution in Dock1 and Rac1 mutant mammary glands. Overall, our study demonstrated an unsuspected role for Dock1/Rac1 signaling in the initiation of mammary gland involution, and also suggested a role for this pathway in the clearance of dead cells by epithelial phagocytes.

Surface science and model catalysis with ionic liquid-modified materials

Materials making use of thin ionic liquid (IL) films as support-modifying functional layer open up a variety of new possibilities in heterogeneous catalysis, which range from the tailoring of gas-surface interactions to the immobilization of molecularly defined reactive sites. The present report reviews recent progress towards an understanding of "supported ionic liquid phase (SILP)" and "solid catalysts with ionic liquid layer (SCILL)" materials at the microscopic level, using a surface science and model catalysis type of approach. Thin film IL systems can be prepared not only ex-situ, but also in-situ under ultrahigh vacuum (UHV) conditions using atomically well-defined surfaces as substrates, for example by physical vapor deposition (PVD). Due to their low vapor pressure, these systems can be studied in UHV using the full spectrum of surface science techniques. We discuss general strategies and considerations of this approach and exemplify the information available from complementary methods, specifically photoelectron spectroscopy and surface vibrational spectroscopy.

Paleogenomic data suggest mammal-like genome size in the ancestral amniote and derived large genome size in amphibians

An unsolved question in evolutionary genomics is whether amniote genomes have been expanding or contracting since the common ancestor of this diverse group. Here, we report on the polarity of amniote genome size evolution using genome size estimates for 14 extinct tetrapod genera from the Paleozoic and early Mesozoic Eras using osteocyte lacunae size as a correlate. We find substantial support for a phylogenetically controlled regression model relating genome size to osteocyte lacunae size (P of slopes <0.01, r²=0.65, phylogenetic signal λ=0.83). Genome size appears to have been homogeneous across Paleozoic crown-tetrapod lineages (average haploid genome size 2.9-3.7 pg) with values similar to those of extant mammals. The differentiation in genome size and underlying architecture among extant tetrapod lineages likely evolved in the Mesozoic and Cenozoic Eras, with expansion in amphibians, contractions along the diapsid lineage, and no directional change within the synapsid lineage leading to mammals.

Osmotic tolerance and habitat of early stegocephalians: indirect evidence from parsimony, taphonomy, palaeobiogeography, physiology and morphology

There are probably many reasons for the widespread belief that temnospondyls and other early stegocephalians were largely restricted to freshwater, but three of the contributing factors will be discussed below. First, temnospondyls have been called amphibians (and thought to be more closely related to extant amphibians than to amniotes). Some authors may have simply concluded that, like extant amphibians, temnospondyls could not live in oceans and seas. Second, under some phylogenies, temnospondyls are more closely related to anurans (and possibly urodeles) than to gymnophionans and could be expected, for parsimony reasons, to share the intolerance of all extant amphibians to saltwater. Similarly, ‘lepospondyls’ are often thought to be more closely related to gymnophionans than to anurans, and could also be expected to lack saltwater tolerance. Third, extant lungfishes live exclusively in freshwater, and early sarcopterygians have long been thought to share this habitat. These interpretations probably explain the widespread belief that early amphibians and early stem-tetrapods were largely restricted to freshwater. However, these three interpretations have been refuted or questioned by recent investigations. A review of the evidence suggests that several (perhaps most) early stegocephalians tolerated saltwater, even although they also lived in freshwater.

A clarification of Pouydebat et al., 2008, evolution of grasping among anthropoids

Several statements by Pouydebat et al. (2008) do not adequately represent views of authors cited, in part because they reflect confusion in the literature about terminology regarding precision gripping. We address these problems, by tracing definitions of precision grips through the literature on manipulative behaviour and identifying the grip that is central to the Pouydebat et al. (2008) study. This allows us to offer a clarification of the statements by Pouydebat et al. (2008) regarding the sequence of appearance of human grip capabilities and possible morphological correlates to these capabilities in extant species.

Nitrite and nitrate formation on model NOx storage materials: on the influence of particle size and composition

A well-defined model-catalyst approach has been utilized to study the formation and decomposition of nitrite and nitrate species on a model NO(x) storage material. The model system comprises BaAl(2x)O(1+3x) particles of different size and stoichiometry, prepared under ultrahigh-vacuum (UHV) conditions on Al(2)O(3)/NiAl(110). Adsorption and reaction of NO(2) has been investigated by molecular beam (MB) methods and time-resolved IR reflection absorption spectroscopy (TR-IRAS) in combination with structural characterization by scanning tunneling microscopy (STM). The growth behavior and chemical composition of the BaAl(2x)O(1+3x) particles has been investigated previously. In this work we focus on the effect of particle size and stoichiometry on the reaction with NO(2). Particles of different size and of different Ba(2+) : Al(3+) surface ion ratio are prepared by varying the preparation conditions. It is shown that at 300 K the reaction mechanism is independent of particle size and composition, involving initial nitrite formation and subsequent transformation of nitrites into surface nitrates. The coordination geometry of the surface nitrates, however, changes characteristically with particle size. For small BaAl(2x)O(1+3x) particles high temperature (800 K) oxygen treatment gives rise to particle ripening, which has a minor effect on the NO(2) uptake behavior, however. STM shows that the morphology of the particle system is largely conserved during NO(2) exposure at 300 K. The reaction is limited to the formation of surface nitrites and nitrates, which are characterized by low thermal stability and completely decompose below 500 K. As no further sintering occurs before decomposition, NO(2) uptake and release is a fully reversible process. For large BaAl(2x)O(1+3x) particles, aggregates with different Ba(2+) : Al(3+) surface ion ratio were prepared. It was shown that the stoichiometry has a major effect on the kinetics of NO(2) uptake. For barium-aluminate-like particles with high Al(3+) concentration, the formation of nitrites and nitrates on the BaAl(2x)O(1+3x) particles at 300 K is slow, and kinetically restricted to the formation of surface species. Only at elevated temperature (500 K) are surface nitrates converted into well-defined bulk Ba(NO(3))(2). This bulk Ba(NO(3))(2) exhibits substantially higher thermal stability and undergoes restructuring and sintering before it decomposes at 700 K. For Ba(2+)-rich BaAl(2x)O(1+3x) particles, on the other hand, nitrate formation occurs at a much higher rate than for the barium-aluminate-like particles. Furthermore, nitrate formation is not limited to the surface, but NO(2) exposure gives rise to the formation of amorphous bulk Ba(NO(3))(2) particles even at 300 K.

Particle size dependent adsorption and reaction kinetics on reduced and partially oxidized Pd nanoparticles

Combining scanning tunneling microscopy (STM), IR reflection absorption spectroscopy (IRAS) and molecular beam (MB) techniques, we have investigated particle size effects on a Pd/Fe(3)O(4) model catalyst. We focus on the particle size dependence of (i) CO adsorption, (ii) oxygen adsorption and (iii) Pd nanoparticle oxidation/reduction. The model system, which is based on Pd nanoparticles supported on an ordered Fe(3)O(4) film on Pt(111), is characterized in detail with respect to particle morphology, nucleation, growth and coalescence behavior of the Pd particles. Morphological changes upon stabilization by thermal treatment in oxygen atmosphere are also considered. The size of the Pd particles can be varied roughly between 1 and 100 nm. The growth and morphology of the Pd particles on the Fe(3)O(4)/Pt(111) film were characterized by STM and IRAS of adsorbed CO as a probe molecule. It was found that very small Pd particles on Fe(3)O(4) show a strongly modified adsorption behavior, characterized by atypically weak CO adsorption and a characteristic CO stretching frequency around 2130 cm(-1). This modification is attributed to a strong interaction with the support. Additionally, the kinetics of CO adsorption was studied by sticking coefficient experiments as a function of particle size. For small particles it is shown that the CO adsorption rate is significantly enhanced by the capture zone effect. The absolute size of the capture zone was quantified on the basis of the STM and sticking coefficient data. Finally, oxygen adsorption was studied by means of MB CO titration experiments. Pure chemisorption of oxygen is observed at 400 K, whereas at 500 K partial oxidation of the particles occurs. The oxidation behavior reveals strong kinetic hindrances to oxidation for larger particles, whereas facile oxidation and reduction are observed for smaller particles. For the latter, estimates point to the formation of oxide layers which, on average, are thicker than the surface oxides on corresponding single crystal surfaces.

Development of a total quality system for transfusion medicine services in Ontario hospitals

TOTAL QUALITY SYSTEM: The purpose of the project was to develop a total quality system in Transfusion Medicine which would serve as a model for development of a provincial transfusion quality system. Pilot studies were carried out in Ottawa and Hamilton/Niagara. Each region was provided with resources to create a Quality Team. The Quality Team was comprised of several individuals including a Quality Team Leader, and a number of Quality Assistants. The responsibilities of the Quality Team included: working with Transfusion Medicine Laboratories in area hospitals to achieve a total quality system, identification, standardization and implementation of 'best transfusion practices' throughout the regional hospitals, development and implementation of standard operating procedures (SOP) based on best practices, development and implementation of transfusion/administration guidelines, assessment of blood utilization, education, training, non-conformance (error) management, and surveillance. Liaison was also established with the co-coordinator for the Transfusion Co-coordinator's Project (ONTRAC), the education coordinator for the Sunnybrook Project, the Public Health Agency of Canada, Quality Management Practice-Laboratory System, the Ontario Hospital Association and Laboratory Licensing. In Ottawa these activities resulted in the development of:

Phylogenetic Signal in Bone Microstructure of Sauropsids

In spite of the fact that the potential usefulness of bone histology in systematics has been discussed for over one and a half centuries, the presence of a phylogenetic signal in the variation of histological characters has rarely been assessed. A quantitative assessment of phylogenetic signal in bone histological characters could provide a justification for performing optimizations of these traits onto independently generated phylogenetic trees (as has been done in recent years). Here we present an investigation on the quantification of the phylogenetic signal in the following bone histological, microanatomical, and morphological traits in a sample of femora of 35 species of sauropsids: vascular density, vascular orientation, index of Haversian remodeling, cortical thickness, and cross-sectional area (bone size). For this purpose, we use two methods, regressions on distance matrices tested for significance using permutations (a Mantel test) and random tree length distribution. Within sauropsids, these bone microstructural traits have an optimal systematic value in archosaurs. In this taxon, a Mantel test shows that the phylogeny explains 81.8% of the variation of bone size and 86.2% of the variation of cortical thickness. In contrast, a Mantel test suggests that the phylogenetic signal in histological traits is weak: although the phylogeny explains 18.7% of the variation of vascular density in archosaurs, the phylogenetic signal is not significant either for vascular orientation or for the index of Haversian remodeling. However, Mantel tests seem to underestimate the proportion of variance of the dependent character explained by the phylogeny, as suggested by a PVR (phylogenetic eigenvector) analysis. We also deal with some complementary questions. First, we evaluate the functional dependence of bone vascular density on bone size by using phylogenetically independent contrasts. Second, we perform a variation partitioning analysis and show that the phylogenetic signal in bone vascular density is not a by-product of phylogentic signal in bone size. Finally, we analyze the evolution of cortical thickness in diapsids by using an optimization by squared change parsimony and discuss the functional significance of this character in terms of decreased buoyancy in crocodiles and mass saving in birds. These results are placed in the framework of the constructional morphology model, according to which the variation of a character in a clade has a historical (phylogenetic) component, a functional (adaptive) component, and a structural (architectural) component.

Transient and steady state CO oxidation kinetics on nanolithographically prepared supported Pd model catalysts: Experiments and simulations

Applying molecular-beam methods to a nanolithographically prepared planar PdSiO2 model catalyst, we have performed a detailed study of the kinetics of CO oxidation. The model catalyst was prepared by electron-beam lithography, allowing individual control of particle size and position. The sample was structurally characterized by atomic force microscopy and scanning electron microscopy before and after reaction. In the kinetic experiments, the O-rich and CO-rich regimes were investigated systematically with respect to their transient and steady-state behaviors, both under bistable and monostable reaction conditions. Separate molecular beams were used in order to supply the reactants, allowing individual control over the reactant fluxes. The desorbing CO2 was detected by both angle-resolved and angle-integrated mass spectrometries. The experimental results were analyzed using different types of microkinetic models, including a detailed reaction-diffusion model, which takes into account the structural parameters of the catalyst as well as scattering of the reactants from the support. The model quantitatively reproduces the results as a function of the reactant fluxes and the surface temperature. Various kinetic effects observed are discussed in detail on the basis of the model. Specifically, it is shown that under conditions of limited oxygen mobility, the switching behavior between the kinetic regimes is largely driven by the surface mobility of CO.

Local reaction rates and surface diffusion on nanolithographically prepared model catalysts: Experiments and simulations

Combining molecular beam methods and angular resolved mass spectrometry, we have studied the angular distribution of desorbing products during CO oxidation on a planar Pd/silica supported model catalyst. The model catalyst was prepared by means of electron beam lithography, allowing individual control of particle size, position, and aspect ratio, and was characterized by atomic force microscopy and scanning electron microscopy before and after reaction. In the experiment, both oxygen and CO rich regimes were investigated using separate molecular beams for the two reactants. This allows exploration of diffusion effects of reactants on the particles and of shadowing and backscattering phenomena. A reaction-diffusion model was developed in order to extract information about local reaction rates on the surface of the catalyst nanoparticles. The model takes into account the structural parameters of the catalyst as well as the backscattering of the reactants and products from the support. It allows a quantitative description of the experimental data and provides a detailed understanding of temperature and reactant flux dependent effects. Moreover, information on the surface mobility of oxygen under steady-state reaction conditions could be obtained by comparison with the experimental results.

Fluctuations and Bistabilities on Catalyst Nanoparticles

We show that coverage fluctuations on catalyst particles can drastically alter their macroscopic catalytic behavior. Scrutinizing the occurrence of kinetic bistabilities, it is demonstrated by molecular beam experiments on model catalysts that macroscopically observable bistabilities vanish completely with decreasing particle size, as previously predicted by theory. The effect is attributed to fluctuation-induced transitions between two kinetic reaction regimes, with a transition rate controlled by both particle size and surface defects. These results suggest that fluctuation-induced effects represent a general phenomenon affecting the reaction kinetics on nanostructured surfaces.

Molecular analysis of the stylar-expressed Solanum chacoense small asparagine-rich protein family related to the HT modifier of gametophytic self-incompatibility in Nicotiana

Gametophytic self-incompatibility (GSI) systems involving the expression of stylar ribonucleases have been described and extensively studied in many plant families including the Solanaceae, Rosaceae and Scrophulariaceae. Pollen recognition and rejection is governed in the style by specific ribonucleases called S-RNases, but in many self-incompatibility (SI) systems, modifier loci that can modulate the SI response have been described at the genetic level. Here, we present at the molecular level, the isolation and characterization of two Solanum chacoense homologues of the Nicotiana HT modifier that had been previously shown to be necessary for the SI reaction to occur in N. alata (McClure et al., 1999). HT homologues from other solanaceous species have also been isolated and a phylogenetic analysis reveals that the HT genes fall into two groups. In S. chacoense, these small proteins named ScHT-A and ScHT-B are expressed in the style and are developmentally regulated during anthesis identically to the S-RNases as well as following compatible and incompatible pollination. To elucidate the precise role of each HT isoform, antisense ScHT-A and RNAi ScHT-B lines were generated. Conversion from SI to self-compatibility (SC) was only observed in RNAi ScHT-B lines with reduced levels of ScHT-B mRNA. These results confirm the role of the HT modifier in solanaceous SI and indicate that only the HT-B isoform is directly involved in SI.

Molecular evidence for precambrian origin of amelogenin, the major protein of vertebrate enamel

Although molecular dating of cladogenetic events is possible, no molecular method has been described to date the acquisition of various tissues. Taking into account the specificity of the major protein in enamel in formation (amelogenin), we were able to develop such a method for enamel. Indeed, because the amelogenin protein is exclusively involved in enamel formation and mineralization and because it lacks pleiotropic effects, this protein is a good candidate to estimate the date of acquisition of this highly mineralized tissue. We searched DNA banks for similarities between the amelogenin sequence and other sequences. Similarities were found only to exon 2 of SPARC (osteonectin) in two protostomians and in eight deuterostomians, and to exon 2 of three SPARC-related deuterostomian genes (SC1, hevin, and QR1). The other amelogenin exons did not reveal significant similarities to other sequences. In these proteins, exon 2 mainly encodes the peptide signal that plays the essential role in enabling the protein to be ultimately localized in the extracellular matrix. We tested the significance of the exon 2 similarities. The observed values were always significantly higher than the expected randomly generated similarities. This demonstrates a common evolutionary origin of this exon. The phylogenetic analyses of exon 2 sequences indicated that exon 2 was duplicated to amelogenin from an ancestral SPARC sequence in the deuterostomian lineage before the duplication of deuterostomian SPARC and SC1/hevin/QR1. We were able to date the origin of the latter duplication at approximately 630 MYA. Therefore, amelogenin exon 2 was acquired before this date, in the Proterozoic, long before the so-called "Cambrian explosion," the sudden appearance of several bilateralian phyla in the fossil record at the Proterozoic-Phanerozoic transition. This sudden appearance has been often suggested to reflect intensive cladogenesis during this period. However, molecular dating of protostomian-deuterostomian divergence and of the cladogenesis among several major clades of Bilateralia lead to a different conclusion: many bilateralian clades were already present during the late Proterozoic. It has previously been proposed that these bilateralians were not mineralized and that they had low fossilization potential. Our results strongly suggest that late Proterozoic fossils possessing a mineralized tissue homologous to enamel might be found in the future.

The oldest stegocephalian from the Iberian peninsula: evidence that temnospondyls were euryhaline

The previous fossil record of limbed vertebrates of the Iberian peninsula started in the Triassic (245 Ma). The discovery of a new temnospondyl from the Late Carboniferous (Stephanian C, 290 Ma) extends the fossil record of stegocephalians in this region by at least 45 Ma. Early stegocephalians are usually thought to have been unable to live in salt water, but the new temnospondyl described below appears to have lived in a coastal region, presumably in salt water.

Arm morbidity after breast-conserving therapy for breast cancer

This study reports on 110 consecutive patients, mean age 59 years, operated on for partial mastectomy and axillary dissection. Radiotherapy of 50 Gy was administered to 75 of the patients. Most tumours were T1 tumours and all patients were NO. Lymphoedema is defined as an increase in arm volume > 10% and impaired shoulder mobility as an impairment of 15 degrees compared with the preoperative value. After operation, 21 patients developed lymphoedema, 17 in the radiotherapy group and 4 in the group without radiotherapy; 49% of the patients had reduced shoulder mobility, and of these, 57% were in the radiotherapy group and 30% in the group without radiotherapy. We found a good correlation between the number of patients stating arm swelling and patients with registered lymphoedema. There were fewer patients stating limitation of movement than patients with registered impaired mobility; 31% of patients were still perceiving some pain five years after the operation. We conclude, that breast-conserving therapy in breast cancer is afflicted with a significant arm morbidity that persists for several years after surgery.

[Problems with arms are common after breast surgery. Lymphedema is a frequent complication in elderly women treated for breast cancer]

75 women aged 70 years or more at the time of operation for breast carcinoma were monitored regarding arm morbidity; median follow-up was three years. 19 women (25%) developed lymphedema; of these, nine belonged to a group of 12 that had undergone both modified radical mastectomy and postoperative radiotherapy. Of this group of 12, ten had impaired arm mobility. Approximately 30% of those with lymphedema had not been identified at routine follow-up, while 20% reported moderate to severe pain. 15 of the 75 reported numbness and pricking sensations in the arm; of these, only one had lymphedema, while six had impaired arm mobility. Having thus found that a substantial number of elderly women experience complications in the upper extremity after primary treatment for breast carcinoma, we feel it essential to consider these factors when planning treatment protocols.

Evolutionary analysis of "hagfish amelogenin"

Hagfishes lack mineralized tissues and teeth. Part of a cDNA strand, allegedly from amelogenin, the major gene involved in enamel formation in mammals, has recently been cloned in a hagfish (Slavkin and Diekwish, Anat. Rec., 1996;245:131-150). This cloning is of great interest because it could change the current view about the evolution of mineralized tissues, but no phylogenetic analysis of this piece of DNA has been made by the authors. Phylogenetic analysis of this part of cDNA has been conducted using both phenetic and cladistic methods. The cDNA amplified in hagfish does not fit with a nonmammalian origin but fits well with a degraded rodent sequence. The gene cloned in hagfish is probably of mammalian origin due to contamination during PCR.

Identification of caries risk children and prevention of caries in pre-school children

A special model for dental care in pre-school children was used in a small clinic in the county of Blekinge in southern Sweden. The model is based on screening of caries risk performed by a dental assistant before the caries attack. Any single risk factor or risk behavior in pre-school children was considered. The aim was to 1) evaluate the dental assistant's selection of caries risk children up to the age of three years, 2) compare dental health variables in 4 yr olds in the test clinic with those for the whole county in 1994 and 3) compare time spent by the dentist and the dental assistant in the test clinic and in the whole county per child up to the age of four. 102 children participated. One specially trained dental assistant screened all children using background factors combined with clinical examinations at ages 1, 2 and 3. Eighty-two children participated each year from one year. A systematized form for questioning the parents was used. Individual caries prevention was given including fluoride and antimicrobial treatments as well as fissure sealants in primary molars at caries risk. The proportion of children with caries lesions at four years and a caries risk assessment up to the age of two was 1.0 (sensitivity). The proportion of children with no caries lesions at four years and no caries risk assessment at year two was 0.7 (specificity). The most frequent risk factors found at 2 yrs were frequency order: lack of oral hygiene (visible plaque), deep fissures in molars and frequent intakes of sweet drinks. The proportion of children with no caries lesions at 4 yrs of age in the test clinic was 92.9% compared to a county mean of 76.4%. In the group of children where a risk assessment was made each year from one year the proportion of caries free children was 96.3%. The total time spent per child in the test clinic was 22 minutes more than the county mean. However, dentist's time, excluding assistance, was 28 minutes less in the test clinic. The results suggest that the model used for caries prevention in pre-school children is cost-effective, and that dental health can be remarkably improved.

[Infectious mononucleosis and splenic pseudocyst: presentation of a case]

The authors report the clinical case of an 18-year-old patient who presented with a symptomatic mass in the left upper quadrant 6 months after having infectious mononucleosis. The preoperative investigation consisted principally of echography and computerized axial tomography of the abdomen, which demonstrated a cystic mass of the lower pole of the spleen. Splenectomy was carried out. Histologic examination showed a pseudocyst of the spleen with a fibrous capsule without an epithelial lining. The treatment and pathogenesis of pseudocysts of the spleen secondary to infectious mononucleosis are discussed.

Sympathetic uveitis 66 years after injury

We report a case of sympathetic uveitis occurring 66 years after perforating trauma to the other eye. To our knowledge this is the longest interval ever cited in the literature.