Zeta potentials of the rare earth element fluorcarbonate minerals focusing on bastnäsite and parisite.

Rare earth elements (REE) are critical to a wide range of technologies ranging from mobile phones to wind turbines. Processing and extraction of REE minerals from ore bodies is, however, both challenging and relatively poorly understood, as the majority of deposits contain only limited enrichment of REEs. An improved understanding of the surface properties of the minerals is important in informing and optimising their processing, in particular for separation by froth flotation. The measurement of zeta potential can be used to extract information regarding the electrical double layer, and hence surface properties of these minerals. There are over 34 REE fluorcarbonate minerals currently identified, however bastnäsite, synchysite and parisite are of most economic importance. Bastnäsite-(Ce), the most common REE fluorcarbonate, supplies over 50% of the world's REE. Previous studies of bastnäsite have showed a wide range of surface behaviour, with the iso-electric point (IEP), being measured between pH values of 4.6 and 9.3. In contrast, no values of IEP have been reported for parisite or synchysite. In this work, we review previous studies of the zeta potentials of bastnäsite to investigate the effects of different methodologies and sample preparation. In addition, measurements of zeta potentials of parisite under water, collector and supernatant conditions were conducted, the first to be reported. These results showed an iso-electric point for parisite of 5.6 under water, with a shift to a more negative zeta potential with both collector (hydroxamic and fatty acids) and supernatant conditions. The IEP with collectors and supernatant was <3.5. As zeta potential measurements in the presence of reagents and supernatants are the most rigorous way of determining the efficiency of a flotation reagent, the agreement between parisite zeta potentials obtained here and previous work on bastnäsite suggests that parisite may be processed using similar reagent schemes to bastnäsite. This is important for future processing of REE deposits, comprising of more complex REE mineralogy.

Inhibition of Listeria monocytogenes by Enterococcus mundtii isolated from soil.

Two bacterial isolates with inhibitory activity against Listeria monocytogenes and Enterococcus faecalis were obtained from soil. Genotypic and phenotypic characterization identified them as Enterococcus mundtii, a species whose ability to compete with L. monocytogenes is relatively unexplored compared to other members of the genus. The thermal stability of the inhibitory factor and its sensitivity to proteolytic enzymes indicate that it is most likely a bacteriocin. Both isolates grew at comparable rates to L. monocytogenes at 5 °C and 10 °C in vitro. One isolate killed L. monocytogenes when it reached concentrations of 10(6)-10(8) CFU ml(-1). Minimum inocula of 10(6) and 10(5) CFU ml(-1) of E. mundtii were required to reduce and maintain L. monocytogenes concentrations beneath the level of detection at 5 °C and 10 °C, respectively. In situ experiments at 5 °C showed that E. mundtii inhibited the growth of L. monocytogenes on vacuum-packed cold smoked salmon during its four week shelf life. E. mundtii could, therefore, control the growth of L. monocytogenes at low temperatures, indicating a potential application in controlling this pathogen in chilled foods. To control growth of Listeria, the concentration of E. mundtii needs to be high, but it is possible that a purified bacteriocin could be used to achieve the same effect.

Assesing the potential for struvite recovery at sewage treatment works.

Struvite in wastewater treatment plants was identified as early as 1939. Problems with struvite formation date back to the 1960s when it was noticed at the Hyperion treatment plant, Los Angeles. Operators at the plant noticed crystalline deposits on the underside of post digestion screens. The digested sludge stream was diluted and it was thought the problem was solved, until five years later when the normal gravity flow of digested sludge had decreased to such a stage that pumping was required. This paper reports the findings of a series of experiments undertaken to identify the potential of recovering struvite from sludge liquors. Seven sludge treatment works (STW) have been investigated including one detail. A number of the works has the potential to form over 100 mg l(-1) of struvite.

Correlation between upper and lower sidebands.

Experimental measurements supported by a simple model show that the upper and lower phase modulation (PM) noise sidebands are always equal and 100% correlated, independent of the noise power originating from multiplicative or additive processes. Similarly, we show that the upper and lower amplitude modulation (AM) noise sidebands are also equal and 100% correlated, independent of the noise power originating from multiplicative or additive processes, Moreover, the single sideband (SSB) PM noise is always equal to one-half the total PM noise. The same is true for the AM noise. Although the upper and lower PM or AM noise sidebands are equal and correlated for broadband additive noise, the phase between the AM and the PM sidebands varies randomly with time. These conclusions still hold even when the RF noise sidebands are not symmetric about the carrier.

Famciclovir as antiviral prophylaxis in laser resurfacing procedures.

Latent herpes simplex virus (HSV types I and II) may be reactivated by laser resurfacing procedures, presenting serious postoperative complications in approximately 9 percent of patients. Perioperative prophylactic administration of nucleoside analog antiviral agents has been shown to decrease the duration and severity of postsurgical herpes infection and to prevent recurrence. This study was conducted to assess the efficacy of famciclovir in preventing orofacial herpes virus reactivation and primary infection in patients undergoing laser resurfacing. HSV history was obtained from a total of 121 patients undergoing the procedure. Antiviral prophylaxis with famciclovir was begun 1 to 2 days before surgery and continued for 5 days after surgery. Patients with no history of orofacial herpes (n = 94) received 125 mg of famciclovir twice daily. Those with a history of orofacial herpes (n = 27) received 250 mg of famciclovir twice daily. Postsurgical HSV infection rates in patients receiving famciclovir prophylaxis were compared with those from a similar historical control group of HSV-positive patients (n = 127) who received no prophylaxis. In patients receiving famciclovir prophylaxis, one patient (1.1 percent) in the HSV-negative history group and no patients in the HSV-positive history group had postsurgical herpes infection. Famciclovir significantly reduced postsurgical herpes infection when compared with the 9.4 percent rate of herpes reactivation in patients who received no prophylaxis (p = 0.003). This study suggests that twice-daily famciclovir prophylaxis markedly reduces orofacial herpes virus infection in patients undergoing laser resurfacing.

A role of Lys614 in the sulfotransferase activity of human heparan sulfate N-deacetylase/N-sulfotransferase.

An active sulfotransferase (ST, residues 558-882) domain of the human heparan sulfate N-deacetylase/N-sulfotransferase (hHSNST) has been identified by aligning the amino acid sequence of hHSNST to that of mouse estrogen sulfotransferase (EST). The bacterially expressed ST domain transfers the 5'-sulfuryl group of 3'-phosphoadenosine-5'-phosphosulfate (PAPS) to only deacetylated heparin with an efficiency similar to that previously reported for the purified rat HSNST. Moreover, the K(m,PAPS) (2.1 microM) of the ST domain is also similar to that of the rat enzyme. Lys48 is a key residue in mEST catalysis. The residue corresponding to Lys48 is conserved in all known heparan sulfate sulfotransferases (Lys614 in the ST domain of hHSNST). Mutation of Lys614 to Ala abolishes N-sulfotransferase activity, indicating an important catalytic role of Lys614 in the ST domain. Crystals of the ST domain have been grown (orthorhombic space group P2(1)2(1)2) with diffraction to 2.5 A resolution.

Free flap breast reconstruction: the LSU experience (1984-1996).

From 1984 through 1996 the section of Plastic and Reconstructive Surgery at Louisiana State Medical Center has performed over 330 breast reconstructive procedures with free flaps. Seven types of reconstructive procedures have been used during this time span, each with its specific salient positive and negative points. The breast reconstruction techniques included the use of (1) Superior Gluteal Myocutaneous Free Flap, (2) Superficial Inferior Epigastric Artery Flap, (3) Transverse Rectus Abdominis Myocutaneous Free Flap, (4) Deep Inferior Epigastric Perforator Flap, (5) Superior Gluteal Artery Perforator Flap, (6) Inferior Gluteal Artery Perforator Flap, and (7) Lateral Thigh Perforator Flap. The experience with these different methods of breast reconstruction has led us to believe that the ideal material for breast reconstruction is skin and fat, rather than muscle or prosthetic devices. At our institution we have evolved from the myocutaneous flap to the use of perforator flaps for breast reconstruction: the donor site morbidity is less, the 99% success rate is superior, and it allows more options with the perforator free flaps than ever realized with the myocutaneous free flap technique. We feel that, in the future, these perforator techniques will become the standard for autogenous breast reconstruction.

Conflict resolution and distress alleviation in monkeys and apes.

Research on nonhuman primates has produced compelling evidence for reconciliation and consolation, that is, postconflict contacts that serve to respectively repair social relationships and reassure distressed individuals, such as victims of attack. This has led to a view of conflict and conflict resolution as an integrated part of social relationships, hence determined by social factors and modifiable by the social environment. Implications of this new model of social conflict are discussed along with evidence for behavioral flexibility, the value of cooperation, and the possibility that distress alleviation rests on empathy, a capacity that may be present in chimpanzees and humans but not in most other animals.

Comparison of gallium-67-citrate and thallium-201 scintigraphy in peripheral and intrathoracic lymphoma.

UNLABELLED: We performed this study in an attempt to reconcile the differences with respect to 67Ga uptake as a function of tumor grade and type in the literature, as well as to determine the sensitivity of 201Tl uptake in both Hodgkin's and non-Hodgkin's lymphoma. METHODS: Thirty-six (9 with low-grade lymphoma, 11 with intermediate-grade lymphoma, 4 with high-grade lymphoma and 12 with Hodgkin's lymphoma) patients underwent both 67Ga and 201Tl scintigraphy. Biopsies were done on all patients. A semiquantitative rating system was used to make statistical comparisons for thallium versus gallium in all lymphoma subgroups, as well as comparisons of thallium and gallium to themselves in all subgroups. RESULTS: Patient sensitivity was only 56% and site sensitivity was 32% in patients with low-grade lymphoma. Conversely, 201Tl sensitivity was 100%, respectively, for patients and sites. The difference between 201Tl and 67Ga sensitivity in patients with low-grade lymphoma on a site basis was statistically significant. When compared to itself in lymphoma subgroups, 201Tl was found to be statistically more avid for low-grade lymphoma than for intermediate, high or Hodgkin's lymphoma. Gallium-67 sensitivity for low-grade lymphoma was significantly less than for Hodgkin's and intermediate grade lymphomas. No significant differences were found when 201Tl and 67Ga were compared in the intermediate, high or Hodgkin's lymphoma groups. CONCLUSION: Thallium-201 demonstrates significantly greater tumor avidity in the low-grade lymphoma group compared to 67Ga citrate. Gallium-67-citrate appears relatively nonavid for low-grade lymphoma compared to 201Tl and is statistically inferior in detecting low-grade lymphoma in comparison to its ability to detect intermediate or high-grade lymphomas. Gallium-67-citrate should not be considered dependable in evaluating patients with low-grade lymphoma. Neither 201Tl or 67Ga is dependable in the evaluation of low-grade lymphoma within the abdomen, since gallium avidity for low-grade lymphoma is low and gastrointestinal excretion of 201Tl is poorly controlled.

An efficient method for routine Epstein-Barr virus immortalization of human B lymphocytes.

A variety of methods exist for the immortalization of B lymphocytes by Epstein-Barr virus due to the simplicity of such techniques to establish cell lines with stable genomic DNA. Two different methods for immortalizing lymphoblastoid cell lines were compared for differences in techniques and materials, time between initiation and immortalization, and success rate of immortalization. An incubation period in Epstein-Barr virus and the use of conditioned media improved immortalization efficiency from 86 to 98% and decreased the time (usually weeks) from culture initiation to cryopreservation. The resulting cell bank was used to produce DNA for genetic studies focusing on the genes involved in non-insulin-dependent diabetes mellitus.

Interferon enhancement of radioimmunotherapy for colon carcinoma.

Recombinant human gamma-interferon (IFN-gamma) has recently been shown to enhance localization of radiolabeled monoclonal antibodies (MAb) to human colon carcinoma xenografts in athymic mice. The present study investigates the ability of gamma-interferon to enhance radioimmunotherapy of a low carcinoembryonic antigen-expressing human colon cancer (WiDr) in athymic mice. Growth curve analysis, antibody localization, and dose estimation studies were performed. A significant tumor growth delay, measured as the time to reach 1.0 g, was noted for animals receiving specific anti-carcinoembryonic antigen 90Y-MAb (ZCE025, 120 microCi) plus IFN-gamma (61.8 days) as compared to animals that received specific 90Y-MAb with phosphate-buffered saline (34.9 days; P less than 0.005). IFN-gamma (100,000 units) was given i.p. every 8 h for 2 days before and 4 days after 90Y-MAb therapy. The time required to reach 1.0 g for animals treated with nonspecific 90Y-MAb (ZME018) was significantly less either with (38.3 days) or without (34.4 days) IFN-gamma. The difference was more apparent when compared to animals receiving IFN-gamma alone (30.0 days) or phosphate-buffered saline alone (28.9 days; P less than 0.001). Increased antibody localization in the tumors of animals treated with IFN-gamma plus specific 90Y-MAb (43.2% injected dose/g) was seen in comparison to animals treated with specific 90Y-MAb without IFN-gamma (18.2% injected dose/g). The estimate of radiation dose delivered to the tumors, based on biodistribution data over time, revealed significantly higher levels in animals treated with specific 90Y-MAb with IFN-gamma (2477 cGy) compared to animals treated without IFN-gamma (1217 cGy). These results provide support for the use of gamma-interferon as an immunomodulating agent prior to radioimmunotherapy.

Discrete mechanics and special relativistic random walks.

Random walks with step lengths equal to the shortest possible physically meaningful distances are considered from the point of view of special relativity involving two observers moving uniformly with respect to each other. A requirement of statistical equivalence of the probability distributions seen by those observers leads to the Lorentz transformations, provided a randomly moving particle shifts from one submicroscopic cell of uncertainty to a neighbor with a speed equivalent to that of light. Ordinary smooth motion would appear to involve a tremendous amount of submicroscopic back and forth randomness subject to a statistical bias favoring a particular direction. The diffusive nature of the motion naturally leads to a spreading of the probability distribution.

Discrete wave mechanics: Multidimensional systems.

Discrete wave mechanics is pursued further by extending the one-dimensional treatment to two (or more) dimensions in the light of explicit momentum considerations. Cognizance is taken of the effect of particle motion on mass and hence on the interactions between components of motion in different directions. The overall energy parameter turns out to be a product instead of a sum of parameters identified with each of several orthogonal axes. Accordingly, the separation of variables is most directly accomplished by factoring the principal energy parameter in conjunction with factoring the wave vector expression itself. Wave vector energies, on the other hand, remain additive. Finally, group velocity components are discussed for higher-dimensional systems.

Discrete wave mechanics: The hydrogen atom with angular momentum.

A discrete wave mechanical treatment of the hydrogen atom is extended to deal with states involving nonzero angular momentum. Only the radial portions of the wave vectors are covered. It is predicted that there is a nonzero minimum distance between the electron and the nucleus; this threshold distance increases with increasing angular momentum. Appropriate finite difference equations are formulated. The states with angular momentum exhibit the same degeneracy as do corresponding energy levels obtained from solutions of Schrödinger's equation.

Discrete wave mechanics: An introduction.

Discrete wave mechanics is formulated for particles in one-dimensional systems by use of a simple finite difference equation. The solutions involve wave vectors (instead of wave functions) as well as a newly defined "wave vector energy." In the limit, as c --> infinity, the treatment reduces to that of Schrödinger's wave mechanics. Specific calculations are made for completely free particles as well as for particles confined to a one-dimensional box. The results exhibit a striking compatibility with relativistic considerations. The wave vectors show properties that can be identified with particles and anti-particles-each possess identical probability distributions with energies that add up to zero.

Discrete wave mechanics: The hydrogen atom.

The quantum mechanical problem of the hydrogen atom is treated by use of a finite difference equation in place of Schrödinger's differential equation. The exact solution leads to a wave vector energy expression that is readily converted to the Bohr-Rydberg formula. (The calculations here reported are limited to spherically symmetric states.) The wave vectors reduce to the familiar solutions of Schrödinger's equation as c --> infinity. The internal consistency and limiting behavior provide support for the view that the equations employed could well constitute an approach to a relativistic formulation of wave mechanics.

Freeze-fracture confirmation of the presence of a core in the specialized tip structure of Mycoplasma pneumoniae.

The presence of a specialized terminal region in Mycoplasma pneumoniae was seen in thin sections viewed in an electron microscope. Actively growing cells were examined by the freeze-fracture technique in the absence of fixation to further establish the core as a significant structural entity. Cross fractures revealed a cytoplasmic matrix surrounding a central core structure of about 54 nm. This structure disappeared rapidly in aging cells. The convex protoplastic faces of the membrane around the core had characteristic 5- to 10-nm intramembrane particles evenly distributed across the cell surface, with no apparent difference in the region of the specialized tip. A periodicity previously noted in negatively stained preparations was clearly defined here in thin sections. Attachment of actively growing cells to sheep erythrocytes was seen primarily as a side attachment rather than attachment at the tip alone. This association between the mycoplasma and the sheep erythrocytes seriously deformed the sheep erythrocytes, but no membrane fusion could be detected.

Statistics of flexible chain configurations.

When Monte Carlo methods are employed to study the statistical dimensions of flexible polymer chains, it is necessary that the sampling be statistically unbiased. One Monte Carlo procedure is the so-called "slithering snake" technique, which has proved to be very useful. A question arises, however, as to how long it takes for a "slithering snake" to be completely regenerated to avoid biasing the samples around a particular configuration. It is demonstrated theoretically and verified by Monte Carlo studies that the number of iterations required to completely regenerate a sample polymer is a quadratic function of the chain length. This verification applies to chains in dilute solution but may not hold for bulk polymers.

Self-avoiding random walks on lattice strips.

A self-avoiding walk on an infinitely long lattice strip of finite width will asymptotically exhibit an end-to-end separation proportional to the number of steps. A proof of this proposition is presented together with comments concerning an earlier attempt to deal with the matter. In addition, some unproved, yet "obvious," conjectures concerning self-avoiding walks are cited as basic propositions requiring study.