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Diatoms are unicellular or chain-forming phytoplankton that use silicon (Si) in cell wall construction. Their survival during periods of apparent nutrient exhaustion enhances carbon sequestration in frontal regions of the northern North Atlantic. These regions may therefore have a more important role in the 'biological pump' than they have previously been attributed1, but how this is achieved is unknown. Diatom growth depends on silicate availability, in addition to nitrate and phosphate2, 3, but northern Atlantic waters are richer in nitrate than silicate4. Following the spring stratification, diatoms are the first phytoplankton to bloom2, 5. Once silicate is exhausted, diatom blooms subside in a major export event6, 7. Here we show that, with nitrate still available for new production, the diatom bloom is prolonged where there is a periodic supply of new silicate: specifically, diatoms thrive by 'mining' deep-water silicate brought to the surface by an unstable ocean front. The mechanism we present here is not limited to silicate fertilization; similar mechanisms could support nitrate-, phosphate- or iron-limited frontal regions in oceans elsewhere.

Population density, one of the most fundamental demographic attributes, may vary systematically with spatial scale, but this scale-sensitivity is incompletely understood. We used a novel approach-based on fully censused and mapped distributions of eastern grey squirrel (Sciurus carolinensis) dreys, beaver (Castor canadensis) lodges, and moose (Alces alces)--to explore the scale-dependence of population density and its relationship to landscape features. We identified population units at several scales, both objectively, using cluster analysis, and arbitrarily, using artificial bounds centred on high-abundance sites. Densities declined with census area. For dreys, this relationship was stronger in objective versus arbitrary population units. Drey density was inconsistently related to patch area, a relationship that was positive for all patches but negative when non-occupied patches were excluded. Drey density was negatively related to the proportion of green-space and positively related to the density of buildings or roads, relationships that were accentuated at coarser scales. Mean drey densities were more sensitive to scale when calculated as organism-weighted versus area-weighted averages. Greater understanding of these scaling effects is required to facilitate comparisons of population density across studies.

The cognitive effects of long-term exposure to organic solvents could be similar to those triggered by certain neurodegenerative diseases.The purpose of this study was to evaluate the effects exerted by accumulated exposure on the cognitive functions.105 subjects with an average history of exposure of 19.3 years were evaluated using seven computerised cognitive tasks (CPT, digit-symbol substitution, Stroop, memory span, word learning and recognition, and TRD) and results were later compared with the performance of a non-exposure group and with a normative reference. A study was made of the association between the length of exposure and performance in the variables in which the exposed subjects displayed significantly lower values than control subjects. In order to evaluate the effect exerted by age, regression functions between performance and age were calculated for each group.Only the indicators from the Stroop and digit-symbol tasks correlated with the length of exposure. The regression functions between performance and age for each group showed that the former decreased significantly faster among exposed subjects than among controls.Findings suggest that, while recent exposure seems to have an effect on a wide range of functions, chronic exposure exerts a selective influence on a smaller group. In this case, only selective attention appears to deteriorate. Similar deficits have been observed in the early stages of patients with Alzheimer's and Parkinson's.

A series of compounds containing the [Mo(3)-mgr;(3)S-(mgr;S(2))(3)-(dtc)(3)](+) complex (dtc = diethyldithiocarbamate) with the anions I(-) (1), I(-) and Br(-) (2), S(2)(-) (3), ClO(4)(-) (4), NO(3)(-) (5), and SO(4)(2)(-) (6) was prepared and characterized by elemental analysis, NMR, IR, and Raman spectroscopy, and FAB mass spectrometry. The previously reported crystal structure of 1 was reinvestigated. The X-ray analysis revealed the incorporation of CH(2)Cl(2) in the crystal having the composition [Mo(3)S(7)(dtc)(3)]I.0.5CH(2)Cl(2) (1a), which was in contradiction to the previous protocol. The corresponding ClO(4)(-) compound (4a) is isotypic. Crystal data: C(15.5)H(31)Cl(2)Mo(3)N(3)O(4)S(13), orthorhombic space group Aba2, a = 25.816(5) Å, b = 17.761(4) Å, c = 16.250(3) Å, Z = 8. For 1a, 4a, 6, and the previously analyzed 2 and 3 the crystal structures revealed characteristic interactions between the anions X and the three axial (out-of-plane) sulfur atoms S(ax) of the disulfido bridges. The Raman data showed a significant decrease of the S(eq)-S(ax) stretch resonance frequency in the order 4, 5, 613. This decrease is paralleled with a slight increase of the S(eq)-S(ax) bond length and with a significant shortening of the X.S(ax) distances when compared to the sum of the corresponding van der Waals radii. A comprehensive quantum chemical study, using both density functional theory and semiempirical calculations, revealed that for hard counterions such as NO(3)(-) and ClO(4)(-) the S(ax).X interactions can be understood in terms of an almost entirely electrostatic interaction, whereas for soft nucleophiles such as I(-) and S(2)(-) significant covalency is observed. In addition, the general reaction of [Mo(3)S(7)](4+) complexes with a nucleophile was modeled. With regard to the side-on bonding of themgr;-S(2) groups to Mo, the calculations indicated a significantly higher bond energy for the axial (out-of-plane) sulfur atoms, explaining the much higher lability of the sulfur atoms in the equatorial (in-plane) position. Analogous differences for the ligating atoms of the peripheral ligands, having a cis and trans position with respect tomgr;(3)-S, are less pronounced.

The epidemic neuropathy that occurred in Cuba between 1992-1993 had three clinical forms: optic, peripheral and mixed. Epidemic neuropathy patients often complained of disorders in the recent memory.We studied 120 patients: 68 with peripheral form, 26 with the optic form and 26 of the mixed form and 70 healthy subjects as control group. The short term memory was evaluated with the paradigm of Brown and Petersen, task of free recall for verbal nonsense material, during several intervals of retention (0, 15, 30, 45 seconds). Also, we applied tests for general capacity, depression and a subjective questionnaire about neuropathic symptoms intensity.Significant differences were observed in the severity of the forgetfulness and depression level between the peripheral form patients and the others groups. The correlation between severity of visual symptoms and the forgetfulness were not significant (S = -0.05; t (176) = -0.7; NS), whereas there was a significant correlation between severity of neuropathic peripheral symptoms and the forgetfulness (S = 0.2; t (184) = 2.7; p0.008). This effect on the mediate memory was not observed in the group of visual neuropathy and only occurred, of attenuated form, in the mixed group.An explanation for this dissociation is suggested based on the physiopathogenic mechanisms invoked in the illness.

The mechanism of the protonation of ferrocene, the simplest model for the electrophilic attack on a metallocene, has been studied extensively. However, neither experiment nor computation have reached agreement on the details of the mechanism. The different model calculations applied [Hartree–Fock, Moller–Plesset, and density functional theory (HF, MP2, and DFT) with different functionals] come to contradicting conclusions. As a complement to our previous work, we report the results obtained for neutral and protonated ferrocene using the coupled-cluster method [CCSD(T)] with polarized double- and triple-zeta basis sets. These calculations show that the metal-protonated and the agostic forms represent minima on the potential energy surface, whereas the ring-protonated form is higher in energy with no minimum structure identified. With regard to the reaction, these results indicate an exo reaction path. The CCSD(T) results are in good agreement with the predictions made by the DFT calculations, whereas the results obtained from the Hartree–Fock and MP2 computations appear to be incorrect.

Resumen El rabdomioma es una tumoracion rara detectada, en la mayor parte de las ocasiones, por ecografia y representa aproximadamente un 1% del total de las anomalias cardiacas halladas intrautero. La evolucion intrauterina y su repercusion hemodinamica dependen del crecimiento del tumor. Grandes masas pueden ser causa de obstrucciones y posteriormente de hidropesia y taquiarritmias. A estas complicaciones se anade su asociacion a la esclerosis tuberosa, la cual ocupa un lugar importante en el consejo prenatal a los padres, ya que su herencia es autosomica dominante. La frecuencia de la asociacion es del 50-70% en las distintas series.

A significant proportion of the expected oil reserves to be found and produced in Eastern Venezuela, are located on wetlands from the Orinoco River Delta (Monagas and Delta Amacuro States). These environments have complex hydraulic due to the confluence in a very flat topography of mayor drainage and confinements basins of the Orinoco River. Additional complexity is derived from a tidal system with back tides and varying tidal levels according to locations. Furthermore, previous studies have demonstrated that great extensions of these wetlands have several meters of peat accumulations, laid on top of sulphidic marine clays that can generate strong acidification problems if are drained and/or exposed to oxidation. In order to solve this environmental constraints, allowing access without dredging and minimum perturbation of this substrates, a modular road concept was developed and tested in a swamp environment at the Caripito Oil Terminal (Monagas State), that uses a light concrete cylinder and other smaller components as building blocks. The cylinder of 860 Kg. and 0.7 m. of outer diameter has a length of 2.82m. An internal honeycomb structure allows for flotation. In order to test the concept a road of 50 m length was built using 270 cylinders placed over a swamp soil with a resistance of 0,18 Kg/cm2. A truck loaded with 100 ton. was passed over 110 times, and settling rates and road deformation was topographically measured. The road was subsequently dismounted and the cylinder inspected for fractures. No fractures were reported in any of the cylinders.

The mechanism of the electrophilic substitution reaction of ferrocene has been investigated using density functional theory. In particular, reactions with two hard electrophiles (protonation and acetylation) and one soft electrophile (mercuration) have been studied at the LDA and B-PW91 levels of theory using a triple-ζ STO basis set. A general description of the reactions has been obtained, leading to results in agreement with experiment. Acetylation is found to occur via exo attack, whereas mercuration follows an endo mechanism. In the case of protonation, evidence for a rapid equilibrium between metal-protonated and agostic ring-protonated ferrocene is obtained, and no clear conclusion concerning the exo or endo mechanism can be deduced. The calculated proton affinities corresponding to both metal-protonated and agostic ring-protonated structures are in excellent agreement with experiment.

As recently reported by Klopper and Luthi, there is a discrepancy between experiment and high-level quantum chemical calculations as to the value of the heterolytic metal–ligand bond disruption enthalpy of ferrocene. Indeed their ab initio calculations lead to a best estimate of 655 kcal/mol, whereas the experimental value is 635 kcal/mol. We report here results obtained using density functional theory. In addition to ferrocene, other metallocenes such as vanadocene, manganocene, nickelocene and ruthenocene, have also been investigated. Gradient-based corrections are crucial for a quantitative description of bond dissociation, our best estimate for ferrocene being 663 kcal/mol.

Heart failure (HF) results in significant costs and requires longterm monitoring and selfcare to prevent recurrence of symptoms. Health care providers have played a key role in monitoring patients and educating them for selfcare. Some have argued that there is distinction between patient education and self-management education. Patient education is designed to help patient manage their disease, whereas self-management is intended to give people the skills to live actively with their chronic condition. Whether the process is called patient education or self-management education, there is consensus that educational preparation is a central nonpharmacologic strategy for longterm management of HF. In the era of cost containment, it is important to design an education program that is accessible to patients and addresses time and economic efficiencies. The interactive group teaching may potentially provide significant education as patients may learn from the interaction of the multidisciplinary care providers with other patients. This presentation will highlight one centre's experience in conducting a multidisciplinary interactive group teaching program for HF. The initiative was designed using the result of the evaluation from previous heart failure awareness public education program. Satisfaction questionnaires that address various components of the participant's learning needs have been completed. Results of the questionnaire will be analyzed to provide insights into whether patients understand the information received and to gain insights into clients' motivation to make the necessary changes to promote selfcare.

Fifty-one patients with adenocarcinoma of the large bowel seen at Hillbrow Hospital over a 36-month period are reviewed. The mean age at diagnosis was 53 years. Advanced disease was present in at least 60%. Carcinoma of the rectum constituted 48% and colonic carcinoma 52%. Cancer and polyps of the large bowel in urban blacks are no longer a rarity in urban hospitals.

We report a case of symptomatic myelolipoma with a good evolution at three and a half years' follow up. The clinical features and the diagnosis of this tumor type are discussed. In this case, as in most cases, CT proved to be the most useful in making the diagnosis. Like most of the cases, the patient was middle aged, obese and hypertensive. The etiology, pathogenesis, clinical features and diagnosis of this disease entity are reviewed. The treatment modalities utilized according to the specific features of each case are discussed.

Introduccion. Las medidas de tiempo de reaccion (TR) se consideran como las mas sensibles para identificar deficit cognitivos en las etapas iniciales de la infeccion por el virus de inmunodeficiencia humana (VIH-1), debido a que el enlentecimiento cognitivo parece ser el signo mas temprano del trastorno cognitivomotor asociado. Las evidencias indican, en general, que a mayores demandas de procesamiento de la tarea, mayor es la probabilidad de que esta sea sensible a los efectos de la infeccion por VIH-1. Objetivo. Evaluar la relacion entre TR y demandas cognitivas de la tarea en individuos seropositivos al VIH-1. Sujetos y metodos. 50 seropositivos neurologicamente asintomaticos se compararon con 34 controles seronegativos en cuatro tareas de TR discriminativo, con diferente nivel de demandas de procesamiento central y con iguales demandas de respuesta motora. Resultados. En la tarea de mayor demanda de procesamiento los seropositivos fueron mas lentos y cometieron mas errores. En las de menores demandas no se observaron diferencias de TR ni de calidad de ejecucion. En la tarea con un nivel significativo de demandas de codificacion sensorial se observaron diferencias de TR, pero no de calidad de la ejecucion. Conclusiones. Aunque se observa una relacion positiva entre nivel de demandas de procesamiento central y enlentecimiento del TR, la presencia de diferencias de TR en ausencia de una disminucion de la calidad de la ejecucion en una tarea con demandas significativas de codificacion sensorial, no permite excluir un deficit en los mecanismos perifericos de procesamiento como locus del deficit de TR en las etapas iniciales de la infeccion por VIH-1.

A significant increase in urine arylsulfatase A activity (p less than 0.01) was found in patients with urothelial tumors. Arylsulfatase A activity was 1.36 +/- 1.10 U/24-h urine in control specimens, 1.90 +/- 1.66 U/24-h urine in various genitourinary tract disorders, and 3.90 +/- 1.98 U/24-h urine in transitional cell carcinoma specimens. Surgical treatment of the neoplastic patients lowered the arylsulfatase A activity found in urine to within reference values. The arylsulfatase A excreted by patients with these tumors was highly sensitive to thermal inactivation while the enzyme activity in the control urines was less affected by the heat treatment. The time course of the arylsulfatase A reaction with 4-nitrocatechol sulfate was not linear in normal individuals, while it was linear in 90% of patients with urothelial tumors. This difference in the kinetic pattern of the enzyme could be used to increase the diagnostic specificity of the determination.

O presente trabalho teve por objetivo verificar o comportamento de variedades de couve em relação à preferência de Brevicoryne brassicae, em condições de campo e laboratório. As variedades 'Manteiga de Ribeirão Pires 2446', 'M.R.P. 2620' e 'M. 1811' foram as menos preferidas no campo, enquanto que em laboratório destacaram-se as variedades 'Roxa', M. Tupi' e 'M. Jundiai'. De forma geral, pode-se considerar como 'Roxa' e 'M. Tupi', enquanto que a 'Crespa 918' suscetível em ambas as condições.

Body size and mating success are analyzed in field collections of three species of Meloidae. Two of these, Lytta vulnerata (LeConte) and Epicauta ochrea (LeConte), mate assortatively for size. The third species, Tegrodera erosa LeConte, does not, although mated individuals are significantly larger than unmated counterparts. Assortative mating is correlated with courtship pattern in these species. Males of L. vulnerata and E. ochrea court from a mounted position on the dorsum of the female. Those of T. erosa court from an unmounted position on the substrate in front of the female. It is proposed that assortative mating occurs in L. vulnerata and E. ochrea because delivery of tactile courtship depends on a reasonably close size match of the sexes. Results of a laboratory mating experiment with Meloe niger Kirby illustrate effect of intersexual size disparity in a species with mounted behavior. A discussion of possible selective advantages of unmounted versus mounted display in the Meloidae is included.

Interfacing a minicomputer with a high resolution densitometer permits the online acquisition and statistical analysis of population parameters for experimental and control sample patterns of various macromolecules obtained by polyacrylamide gel electrophoresis. This technique, illustrated in this paper using protein from the brains of Japanese quail, enables the experimenter to make comparisons which were previously not readily available for electrophoresis.

Puromycin appears to block long-term memory of color discrimination training (measured 3 days after initial training) and inhibits its acquisition (measured as the number of days taken to reach the task criterion). The antibiotic has no effect on long-term memory of pattern discrimination, although it does affect acquisition to criterion. These results suggest that puromycin’s influence on long-term memory is a function of the extent of long-term memory formation on the initial day of training as determined by task difficulty.

The use of vasectomy has increased considerably over the past few years in the province of Guadalajara, Spain. This study reviews the records of 140 men who underwent vasectomy between March 1985-March 1986. The protocol included a personal interview and a questionnaire on attitudes toward contraception, sex, marriage, sterilization, and likelihood of desiring more children in the future. Candidates for vasectomy were required to have 2 children. The operations were performed under local anesthesia on an outpatient basis. Semen analyses were done at 4 weeks after a minimum of 10 ejaculations and at 12 weeks. A new questionnaire 12 months after the operation sought information on postoperative pain, changes in libido, and satisfaction of the couple with the operation. The average of the men was 37 years and the average duration of union was 11 years. Couples had 3 children on average and 85% had primary educations. At the time of the initial consultation, 44% were using condoms, 17% pills, 10% IUDs, and 20% withdrawal. 63% had undesired children, mainly due to failure of withdrawal. No sperm were found 4 or 12 weeks in any of the cases, and no pregnancies were reported. Infections developed at the site of the incision in 10 cases and epididymitis occurred 25 cases.

Two cDNA clones (lambda GC-1 and lambda GC-2) for human beta-glucocerebrosidase [EC 3.2.1.45] have been isolated from a human hepatoma library in lambda gt11 by immunological screening using monospecific polyclonal antibody for beta-glucocerebrosidase. Restriction endonuclease mapping indicates that these clones are probably identical in size, each with a 1900 bp insert. The 50 kDa size of the insert-encoded polypeptide produced by these clones in fusion with beta-galactosidase of lambda gt11 in E. coli BNN103 is consistent with the size of the nascent form of beta-glucocerebrosidase. These fusion proteins are shown by Western blotting to react with antibody to beta-glucocerebrosidase. Amino acid sequence deduced from the nucleotide sequence of the insert ir pGC-1 is identical to known amino acid sequence of beta-glucocerebrosidase, and thus, confirms that the clones are specific for beta-glucocerebrosidase.

A PDP-12 interface was designed, constructed, and tested for realtime input and output of binary information. Within limits this interface can be used with any peripheral device which operates in the binary mode. In addition to its generality of application the interface features include ease of expansion and low cost. A description of its design and operation is give here in terms of a typical application: the control of behavioral equipment (i.e. “Skinner Boxes”) for operant conditioning.

An operant conditioning and data analysis software system was developed for use on a PDP-12A minicomputer. The operant software functions in quasi time-sharing fashion to control and acquire data from any peripheral device that operates in the binary mode. In addition to independently running different experiments in near simultaneous fashion, the program also provides information on the current status of each experiment using a cathode ray-tube display. Response data from each experimental subject is stored on magnetic tape and analyzed, off-line, by the data analysis portion of the software system. A discussion of the operation of this system is given for one possible application: visual discrimination training.

One hundred seventy transnasal balloon catheter dilation procedures were performed in 35 patients with esophageal strictures to assess the efficacy and safety of the procedure. On the average, five dilations were required per patient. Depending on the cause of the esophageal stricture, success rates for the technique ranged from 67% to 87%, with success defined as the resolution of dysphagia to both fluids and solids. Three complications, all perforations, were seen; one perforation required surgical repair. No procedure-related deaths were identified in this series. Balloon catheter dilation can be safely applied to esophageal strictures from a variety of causes, with a high degree of clinical success.