Properties of Four Biological Flocs as Related to Settling

The influence of four industrial wastewater types (organic chemical, dye, leather, and winery industries) on the exopolymeric substances (EPSs) constituents [protein, polysaccharide, and deoxyribonucleic acid (DNA)] and physicochemical properties of flocs (contact angle, surface charge, and bound water) was determined. Four laboratory scale activated sludge systems were used; they were fed with real wastewaters and were operated continuously under steady-state conditions. The EPS analysis showed that between 70 and 80% of the extracellular organic material could be attributed to protein. The proteins in the bound form were quantitatively greater than the soluble protein form in winery industry floc EPSs. The soluble protein ratios were higher than bound protein ratios in organic chemical, dye, and leather industries flocs. Lower amounts of protein and high DNA content were found in the EPS flocs grown on wastewaters containing more complex substrates (organic chemical, leather, and dye). Changing the wastewater from chemical, leather, and dye to that of winery industry resulted in an increase in protein and a decrease in DNA level of floc EPSs. The sludge surface of winery industry flocs were less hydrophobic (small contact angle) and more highly negatively charged compared to chemical, dye, and leather industry flocs. A higher sludge volume index (SVI), an indication of poorer settleability, was associated with both small amounts of EPS and protein and a high amount of DNA. Both high hydrophilic and negatively charged surfaces corresponded to lower levels of SVI and good settling properties. The results of this study demonstrated that wastewater type influenced the EPS composition and physicochemical properties of sludge. The surface properties (surface charge, contact angle, and bound water) and composition of EPS, apart from the carbohydrate content, governed the settleability of sludge and were important in controlling the SVI.     

Design and operation of a 150 W near diffraction-limited laseramplifier with SBS wavefront correction

The design and operation of a Nd:glass regenerative amplifier using a stimulated Brillouin scattering (SBS) phase conjugate mirror is presented. The system can be operated at 25-30 J per pulse with a pulse width of 14 ns and a pulse repetition frequency (PRF) of 6 Hz. This results in an average output power of >150 W with a peak power of 2 GW. The experimentally measured divergence of the amplifier output is 1.25× the diffraction limit and it can be frequency doubled with >80% efficiency. The detailed considerations required for this specific amplifier design are discussed as well as how these considerations apply to the design of high average power, high beam quality laser systems in general     

Evaluation and treatment of gynecomastia

Gynecomastia is a proliferation of the glandular component of the male breast. Causes include altered estrogen-androgen levels, aging, puberty, chronic disease, tumors and drugs. The physician must determine whether the condition has a physiologic or pathologic cause. Pubertal gynecomastia is generally physiologic and regresses without treatment. The likelihood of pathology is increased in patients over 26 years of age who present with new-onset gynecomastia. A thorough history, a complete physical examination and an appropriate clinical evaluation facilitate the prompt diagnosis and treatment of this condition.     

Measuring the progression of foreign-body reaction to silicone implants using in vivo MR microscopy

We used in vivo magnetic resonance (MR) microscopy to follow the growth of fibrous capsule as a foreign body reaction to silicone implants in rats. Anesthetized rats were imaged 1, 7, 14, and 28 days after silicone-coated MR imaging coils were sutured to their neck muscles. On the twenty-eighth day, rats were sacrificed and coils and adjacent tissues were removed en bloc and fixed in formalin, reimaged with MR, and sectioned for conventional histology. Three-dimensional (3-D) spin-echo [3DFT] acquisition gave in-plane resolution of 32 x 32 microns in vivo and 16 x 16 microns ex vivo. All MR images showed a diffuse band of elevated signal intensity between the silicone of the coil and adjacent tissue. The border of the hyperintense band was thin and not well defined at seven days post-implantation. From 7-28 days, the band showed relatively homogeneous signal intensity and its thickness increased 44% on the rectus muscle side and 78% on the subcutaneous side. The capsule thickness determined either by MR in vivo and ex vivo microscopy or conventional histology was not significantly different, and there was a significant correlation between thickness measurements among those methods. MR in vivo microscopy provides sufficient resolution and spatial information to serially evaluate the growth of the foreign body fibrous capsule over time, thus achieving greater accuracy and consistency in measurements.     

Dentastic bond strength to dentin

PURPOSE: To evaluate the shear bond strength to the dentin of permanent teeth and failure site of Dentastic hydrophilic dentin bonding agent. MATERIALS AND METHODS: Forty permanent noncarious molar teeth stored in distilled water were obtained. The teeth were cleaned with pumice and a rubber cup. The mesio-buccal surface of the teeth was ground flat with hand pressure with a series of SiC paper ending with the 600 grit to provide a uniform surface on dentin to which the resin composite could be applied. After preparing the tooth surface, the teeth were stored in distilled water for 48 hours. They were then divided at random into four groups of 10 specimens each: Group 1: Dentastic, five coats of primer; Group 2: Dentastic, three coats of primer; Group 3: Dentastic, five coats of primer, light-cured adhesive before resin bonding; Group 4: Dentastic, three coats of primer, light-cured adhesive before resin bonding. All specimens were thermocycled (500x) and sheared in a testing machine. After shear testing, the debonded sites of all samples were examined with a stereomicroscope and a scanning electron microscope. RESULTS: The results in MPa were: Group 1: 22.63 +/- 6.24; Group 2: 23.35 +/- 5.14; Group 3: 23.58 +/- 5.66; Group 4: 27.26 +/- 8.22. ANOVA and Student-Newman-Keuls showed no statistically significant difference between the groups. In all groups, all specimens failed at the dentin (dentin cohesive failure = dentin fracture) or at the resin (resin cohesive failure = resin fracture). This means that the bond strength of the product is stronger than the cohesive strengths of the dentin and the resin.     

Trapping of soursop (Annona muricata) juice volatiles on porapak Q by suction

The trapping technique of Singleton and Pattee, in which the volatiles are swept to a Porapak Q trap by suction rather than by a sweeping gas, was modified and used to isolate soursop juice volatiles. Using fixed, low vacuum and operating conditions determined specifically for soursop volatiles, very high reproducibility was obtained. The majority of the peaks had a coefficient of variation less than 0.10. The relative amounts of the volatile components obtained by direct headspace sampling was fairly well maintained in the Porapak Q concentrate. The chromatograms showed distinct differences between two commercial brands or between lots of the same brand of soursop juice. The trapping technique appear to have wide applicability provided that the operating conditions are adapted to each product studied.     

Contribution of emotionally traumatic events and inheritance to the report of current physical health problems in 4042 Vietnam era veteran twin pairs

STATEMENT OF PROBLEM: Use of temporary crowns and fixed partial dentures is especially relevant when the treatment plan requires restorations for long interim periods, and the in-service discoloration of provisional restorative materials is a major drawback. PURPOSE: This study evaluated the discoloration effect of coffee and tea on some materials that are commonly used in the fabrication of provisional restorations. MATERIAL AND METHODS: Six commercially available provisional resins (Jet, Caulk TBR, Protemp Garant, Luxatemp Solar, Provipont DC and SR-Ivocron-PE) were evaluated after 1 day, 7 days, and 30 days of immersion in various staining solutions. Color measurements were obtained by using a Dr Lange Micro Color tristimulus colorimeter and color differences (delta E*) were estimated. RESULTS: The 2 chemically activated resins (Jet and Caulk TBR) and the heat-cured resin (SR-Ivocron PE) exhibited the least color changes, whereas the Provipont-DC resin was the least color stable. After immersion for 30 days, the combination with the coffee solution resulted in unacceptable discoloration for all the tested materials. CONCLUSIONS: Provisional restorative materials, staining solutions, and immersion time were significant factors that affected color stability. After immersion for 7 days, all materials showed observable color changes. The composite-based materials, especially light-curing composites, were the least color stable. The coffee solution exhibited more staining capacity than the tea solution.     

Improving the processing properties of chlorinated PVC resins

An earlier paper (1) established the need for new compounding technology to deal with changes in melt flow resulting from the postchlorination of PVC resins. The present work attacks the more-than-doubled melt viscosity of chlorinated PVC as measured in stabilized resin. The potential for marked reduction in viscosity. improvement in processing stability, and retention of marketable product properties is explored. The development process including the definition of performance requirements, test methods used, and resulting balance of properties is described.