Oxidation of As(III) by potassium permanganate

The oxidation of As(III) with potassium permanganate was studied under conditions including pH, initial As(III) concentration and dosage of Mn(VII). The results have shown that potassium permanganate was an effective agent for oxidation of As(III) in a wide pH range. The pH value of tested water was not a significant factor affecting the oxidation of As(III) by Mn(VII). Although theoretical redox analyses suggest that Mn(VII) should have better performance in oxidization of As(III) within lower pH ranges, the experimental results show that the oxidation efficiencies of As(III) under basic and acidic conditions were similar, which may be due to the adsorption of As(III) on the Mn(OH)2 and MnO2 resulting from the oxidation of As(III).

Removal of humic substances (HS) from water by electro-microfiltration (EMF)

Humic substances (HS) represent the common agents contributing to flux decline during membrane filtration of natural water. In order to minimize the fouling during microfiltration (MF) of HS, modifying the operation of MF presents a promising alternative. A laboratory-scale electro-microfiltration (EMF) module was used to separate Aldrich HS from water by applying a voltage across the membrane. The presence of an electric field significantly reduced the flux decline. A flux comparable to that of ion-free water was attained when the voltage was near the critical electric field strength (Ecritical), i.e., the electrical field gradient that balances the advective and electrophoretic velocities of solute. At an applied voltage of 100 V (approximately 110 V/cm), it was able to reduce UV absorbance at 254 nm (UV254), total organic carbon (TOC) and trihalomethane formation potential (THMFP) by over 50% in the permeate. Results from 1H nuclear magnetic resonance (1H NMR) analysis suggest that the aromatic and functionalized aliphatic fractions decreased significantly in the permeate. The charged HS have large molecule weight compared with those passing through membrane. Results clearly indicate that a combination of electric force with MF can increase HS rejection and decrease flux decline. Electrophoretic attraction was the major mechanism for the improvement of flux and rejection over time.

Predicting metals partitioning in wastewater treatment plant influents

Interactions of heavy metals with primary sludge particulates were investigated using batch equilibrium metal uptake experiments. Results showed that metal uptake by primary sludge is significantly affected by pH. A mathematical model was developed to describe metals partitioning as a function of pH. The metal adsorption constants were determined. Results showed that for the same metal ion, the values of metal adsorption constants for primary sludge samples collected from different locations and at different times were in the same order of magnitude. Therefore, the adsorption constants were normalized and calibrated using field data. For Ag(I), Cd(II), Co(II), Cr(III), Cu(II), Ni(II), Pb(II), and Zn(II), the calibrated values of adsorption constants (logK(S)) are, respectively, 4.4, 5.1, 3.6, 4.5, 4.6, 3.6, 6.0, and 6.0. These constants can be used to predict the metal partitioning in plant influents and metal removal in primary treatment processes.

Adsorption of arsenic(V) by activated carbon prepared from oat hulls

The efficiency of self-manufactured activated carbon (AC) produced from oat hulls in adsorbing arsenic(V) was tested in a batch reactor. The results indicated that the adsorptive capacity of AC was affected by initial pH value, with adsorption capacity decreasing from 3.09 to 1.57 mg As g(-1) AC when the initial pH values increased from 5 to 8. A modified linear driving force model conjugated with a Langmuir isotherm was created to describe the study's kinetics. The test results show that rapid adsorption and slow adsorption exist simultaneously when AC is used to remove arsenic(V).

Removal of arsenic and humic substances (HSs) by electro-ultrafiltration (EUF)

A laboratory scale electro-ultrafiltration (EUF) system was developed and used to explore the removal of arsenic and humic substances (HSs) from water. As a negatively charged species, arsenate(V) was readily removed after applying voltage to the EUF cell. Arsenite(III) was removed via EUF after the pH of the water had been adjusted. Meanwhile, the rejection of HSs increased due to the presence of an electric field. This study also showed that the removal of arsenite(III) from water relies primarily on electrostatic and non-electrostatic mechanisms. In the presence of HSs, arsenate(V) complexed with the HSs and was then able to be removed by EUF. This study demonstrates that EUF is a highly promising means of removing arsenic from water.

Modeling heavy metal uptake by sludge particulates in the presence of dissolved organic matter

The uptake of the seven heavy metal ions Cd(II), Co(II), Cr(III), Cu(II), Ni(II), Pb(II), and Zn(II) by sludge particulates in single-metal systems was investigated. Results showed that under acidic and neutral pH conditions, the uptake of all heavy metals by sludge particulates increases with the increase of pH. However, in the alkaline pH region, the uptake of Cu(II), Ni(II), and Co(II) decreases with the increase of pH, primarily due to the high dissolved organic matter (DOM) concentration in high pH conditions. Based on chemical reactions among heavy metal, sludge solids, and DOM, a mathematical model describing metal uptake as functions of DOM and pH was developed. The stability constants of metal-sludge and metal-DOM complexes can be determined using this model in conjunction with experimental metal uptake data. Results showed that, for the secondary sludge sample collected from Baltimore Back River Wastewater Treatment plant on March 1997, the stability constants of Cu(II)-sludge complex (log K(S)) and Cu(II)-DOM complex (log K(L)) are 5.3+/-0.2 and 4.7+/-0.3, respectively; for Ni(II), they are 4.0+/-0.2 and 3.9+/-0.2, respectively. Results also showed that under neutral and low pH conditions (pH<8), the DOM effects on metal uptake for all heavy metals are insignificant. Therefore, the DOM term in the model can be ignored. Results showed that, for the secondary sludge sample collected from Baltimore Back River Wastewater Treatment plant on December 1996, the estimated log K(S) values of metal-sludge complexes for Cd(II), Co(II), Cr(III), Cu(II), Ni(II), Pb(II), and Zn(II) are, respectively, 3.6+/-0.2, 3.0+/-0.1, 5.5+/-0.1, 4.8+/-0.1, 3.1+/-0.1, 5.1+/-0.1, and 4.4+/-0.3.

Interactions of silver with wastewater constituents

The interactions of silver ion with wastewater constituents including chloride, sludge particulates, and dissolved organic matter (DOM) were investigated using fresh and processed sludge samples from various municipal wastewater treatment plants. Fresh sludge samples were used to examine the silver removal characteristics in the presence of chloride. Processed sludge samples that were subjected to a deionized-water washing procedure to remove the chloride ion were used to examine the interactions among Ag(I), sludge solids, and DOM. Results showed that, under field conditions, most of the silver can be removed through precipitation with chloride and adsorption by sludge particulates. Results obtained using washed sludge samples showed that Ag(I) adsorption by sludge particulates increases with the increase of pH in the acidic pH range, but decreases with the increase of pH in the alkaline pH range. Since the DOM concentration increases significantly with the increase of pH in the alkaline pH region, it can be concluded that the formation of Ag(I)-DOM complexes reduces the Ag(I) adsorption by sludge. Fitting of the Langmuir isotherm to the adsorption data indicated that adsorption constants have a slight increase with the increase of pH in the acidic pH range, but decrease significantly with the increase of pH in the alkaline pH range. The decrease of the Ag(I) adsorption constants in the alkaline pH range can be attributed to the formation of Ag(I)-DOM complexes which weaken the Ag(I) binding strength by sludge surface sites. The fitted isotherms also showed that the Ag(I) adsorption capacity increases with the increase of pH in the entire pH range.

The surface characteristics of activated carbon as affected by ozone and alkaline treatment

The surface chemical characteristics of activated carbon treated by ozone and alkaline are determined in terms of surface functional groups and surface acidity. Surface functional groups are analyzed by the IR spectroscopic method and Boehm's titration technique. The surface acidity of activated carbon is determined by electrophoretic mobility measurements. The oxygen concentration of activated carbon increases upon ozone and NaOH treatment. Surface functional groups increase mostly in the hydroxyl and carboxyl categories rather than the carbonyl category upon ozone and NaOH treatment.

Ozonation of activated carbon and its effects on the adsorption of VOCs exemplified by methylethylketone and benzene

Ozonation can modify the surface property of an activated carbon such as specific surface area, pore volume, and functional group. Results indicate that ozonation can increase the specific surface area of an activated carbon from 783+/-51 to 851+/-25 m2/g due in part to increasing micropores (those below 15 A). However, there is no change in macropore and mesopore upon ozonation. The amount of oxygen functional group (OFG) increases from 197+/-4 to 240+/-4 microeq/g, mostly in hydroxyl and carboxyl groups upon ozone treatment. These oxygen-containing functional groups are stable in the temperature range 30-250 degrees C, but begin to decompose when temperature increases beyond 300 and 350 degrees C. When the temperature reaches 1200 degrees C, all OFGs virtually disappear. The effect of ozone treatment on the adsorption of volatile organic carbon (VOC) was exemplified by methylethylketone (MEK) and benzene. The adsorption density of MEK and benzene by ozone treated activated carbon (AC(O3)) are greater than that by the untreated (AC), with MEK being more adsorbable than benzene. Results of factorial analysis indicate that physical characteristics, namely, micropore, BET surface area, pore diameter (PD), micropore volume (MV) play an important role on benzene and MEK adsorption.

The adsorption of benzene and methylethylketone onto activated carbon: thermodynamic aspects

The adsorption of volatile organic compounds (VOCs), exemplified by benzene and methylethylketone (MEK), onto seven different types of activated carbon was investigated. Results show that for benzene adsorption the adsorption characteristic energy, enthalpy, free energy and entropy are in the range 17.12-36.86, -20.8 to -44.7, -11.89 to -16.22 kJ/mole and -29.4 to -85.3 J/mole/K, respectively. For the adsorption of MEK, the adsorption characteristic energy, enthalpy, free energy and entropy are in the range 14.47-32.34, -18.3 to -40.8, -10.78 to -15.56 kJ/mole and -24.8 to approximately -60.3 J/mole/K, respectively. The adsorption enthalpy can be calculated indirectly from statistical thermodynamic method and directly from the immersion enthalpy method. The adsorption characteristic energy is calculated by the Dubinin-Astokhov equation. The free energy is calculated by the measured equilibrium adsorption constant.

Heavy metal removal by activated sludge: influence of Nocardia amarae

The goal of this research was to examine the metal binding capacity of Nocardia amarae cells and to assess the influence of Nocardia cells on the overall metal binding capacity of activated sludge. Metal sorption capacities of the pure Nocardia cells and activated sludge biomass containing various levels of added Nocardia pure cultures were determined by a series of batch experiments. Batch sorption isotherms for nickel (Ni), copper (Cu), and cadmium (Cd) showed that the pure culture of N. amarae exhibited significantly higher metal sorption capacity than the activated sludge biomass obtained from Wilmington Wastewater Treatment Plant (Wilmington, DE). Surface area of biomass estimated by a dye technique showed that pure N. amarae cells growing at stationary phase have substantially more specific surface area than that of activated sludge from Wilmington Treatment Plant. A two-fold difference in specific surface area indicated that the higher metal sorption capacity of Nocardia cells may be due to the higher specific surface area. The metal sorption capacity of activated sludge increased proportionally with the amount of Nocardia cells present in the mixed liquor. This increase was attributed to the greater specific surface area of the mixed liquor samples containing greater amounts of Nocardia cells.

Sonochemical decomposition of dibenzothiophene in aqueous solution

Dibenzothiophene is decomposed rapidly by sonication in aqueous solution. Decomposition of dibenzothiophene follows a first-order reaction kinetics. The rate constant was found to increase with increasing ultrasonic energy intensity, temperature, and pH and decrease with increasing initial dibenzothiophene concentration. The activation energy was 12.6 kJ mol in the temperature range of 15-50 degrees C, suggesting a diffusion-controlled reaction. Hydroxydibenzothiophenes and dihydroxydibenzothiophenes were identified as reaction intermediates. It is proposed that dibenzothiophene is oxidized by OH radical to hydroxy-dibenzothiophenes and then to dihydroxy-dibenzothiophenes. Kinetic analysis suggests that approximately 72% of the dibcnzothiophene decomposition occurred via OH radical addition. A pathway and a kinetic model for the sonochemical decomposition of dibenzothiophene in aqueous solution are proposed.

A microscope system with a dual-band filter for the simultaneous enumeration of Cryptosporidium parvum oocysts and sporozoites

A dual band filter set was designed to allow the simultaneous viewing of two fluorochromes (fluorescein isothiocyanate (FITC) and 4',6-diamidino-2-phenylindole (DAPI)) so that Cryptosporidium oocysts and sporozoites can be viewed together. Simultaneous viewing increases accuracy and decreases examination time as compared to current Environmental Protection Agency (EPA) Method 1623 for the detection of Cryptosporidium and Giardia in water by filtration/IMS/FA (Immunomagnetic Separation/Fluorescent Antibodies). Additionally, a microscope equipped with a programmable, motorized stage, CCD camera, and display monitor was used to facilitate well slide evaluation in a quick and precise fashion ensuring complete coverage without overlap and eliminating the optical strain associated with counting hundreds of images through an eyepiece.

Adsorption of hydrazoic acid from aqueous solution by macroreticular resin

Sodium azide is a key component in the automobile air bag. When dissolved in aqueous solution, it reacts rapidly with water to form hydrazoic acid which is a highly toxic chemical and is strongly regulated by government. In the present study, adsorption of hydrazoic acid from aqueous solution by macroreticular resin is investigated. This method can provides a convenient means for dealing with the toxic hydrazoic acid. Experimental tests of batch equilibrium adsorption and continuous column adsorption of hydrazoic acid were conducted and the test results were employed to establish adsorption isotherm and to evaluate the column adsorption efficiency. The test results revealed that the multilayer adsorption isotherms, like the modified Langmuir or Jossens model, are needed to adequately describe the hydrazoic acid adsorption equilibrium between the liquid and solid (resin) phases. In the column adsorption process, a theoretical model was adopted for representing the hydrazoic acid change in the aqueous solution exiting the column and the verified theoretical model significantly facilitates prediction of adsorption breakthroughs and column design. Regeneration of exhausted resin was investigated. Solution of 10% (w/w) NaCl was found to be a very efficient regenerant.

Factors affecting the distribution of heavy metals in wastewater treatment processes: role of sludge particulate

The distribution of heavy metals, namely, Ag(I), Cd(II), Co(II), Cr(III,VI), Cu(II), Hg(II), Ni(II), Pb(II), and Zn(II) in 4 municipal wastewater treatment plants was evaluated as a function of several parameters including pH, COD, ionic strength and SS. Although there are variations in pH, alkalinity, COD and ionic strength, the results show that wastewater samples containing less than 5 g/L suspended solids concentration have similar characteristics. Correlations among heavy metal distribution (as the ratio between dissolved to total metals) and wastewater characteristics were attempted. Correlation between the parameters monitored and metal distribution is poor. In the case of pH, no apparent relationship could be seen. In general, increasing COD and ionic strength decreases the metal distribution. Metal distribution relies almost entirely on the concentration of solids in wastewater samples. Total metal removal in primary treatment process is lower than that reported in the literature. This could be attributed to the low average solids removal observed in the treatment plants investigated. Solids reduction at the effluent were larger than 80% and total metals removal was identical to that of the primary treatment process.

A highly digestible sorghum mutant cultivar exhibits a unique folded structure of endosperm protein bodies

The endosperm of a sorghum mutant cultivar, with high in vitro uncooked and cooked protein digestibilities, was examined by transmission electron microscopy and alpha-, beta-, and gamma-kafirins (storage proteins) were localized within its protein bodies. Transmission electron microscopy micrographs revealed that these protein bodies had a unique microstructure related to high protein digestibility. They were irregular in shape and had numerous invaginations, often reaching to the central area of the protein body. Protein bodies from normal cultivars, such as P721N studied here, with much lower uncooked and cooked digestibilities are spherical and contain no invaginations. Immunocytochemistry results showed that the relative location of alpha- and beta-kafirins within the protein bodies of the highly digestible genotype were similar to the normal cultivar, P721N. Gamma-kafirin, however, was concentrated in dark-staining regions at the base of the folds instead of at the protein body periphery, as is typical of normal cultivars. The resulting easy accessibility of digestive enzymes to alpha-kafirin, the major storage protein, in addition to the increased surface area of the protein bodies of the highly digestible cultivar appear to account for its high in vitro protein digestibility.

Rhizosphere bacteria enhance the accumulation of selenium and mercury in wetland plants

The role of rhizosphere bacteria in facilitating Se and Hg accumulation in two wetland plants, saltmarsh bulrush (Scirpus robustus Pursh) and rabbitfoot grass (Polypogon monspeliensis (L.) Desf.), was studied. Ampicillin-amended plants (i.e., with inhibited rhizosphere bacteria) supplied with Na(2)SeO(4) or HgCl(2) had significantly lower concentrations of Se and Hg, respectively, in roots than plants without ampicillin. These results were confirmed by inoculating axenic saltmarsh bulrush plants with bacteria isolated from the rhizosphere of plants collected from the field; these plants accumulated significantly more Se and Hg compared to axenic controls. Therefore, rhizosphere bacteria can increase the efficiency of Se and Hg phytoremediation by promoting the accumulation of Se and Hg in tissues of wetland plants.

Cognition and utilization of Papanicolaou testing after the implementation of National Health Insurance in rural Taiwan

Previous reports have indicated that knowledge and utilization of Papanicolaou (Pap) testing in Taiwan are low, especially among residents of rural areas. However, those studies were conducted before the implementation of National Health Insurance (NHI), which now covers Pap testing. To assess the cognition and utilization of Pap testing after the implementation of NHI in 1995, 708 women aged 40 years or more were interviewed by the Yang-Ming Crusade in July 1997. Of these women, 276 (39%) had heard of the Pap test, 226 (32%) had had the test, and 156 (22%) had had the test in the last 3 years (1995-1997). Of those who had never had the Pap test before 1995, 17% underwent it for the first time after the implementation of NHI. In contrast to an earlier comparable study, the present study shows a significant increase in both the cognition and utilization rates of Pap testing (from 27% to 39%, and 18% to 32%, respectively) among women in rural areas after the test was covered by NHI. However, both knowledge and use of the test among older and lower-educated women are still low.

Adsorption Characteristics of Dye onto Sludge Particulates

The dye adsorption characteristics of sludge particulates, both primary and secondary, were studied. Major factors such as pH, SS (suspended solid), and ionic strength on dye adsorption were evaluated. An anionic dye, new coccine acid red #18 was used as the adsorbate. Results show that dye adsorption is a fast process and can reach equilibrium in 30 min. Results also show that pH is the most important factor determining the dye adsorption. Decreasing pH can significantly increase the adsorption of the dye. Greater adsorption density can be achieved at SS less than 1 g/L. However, at SS concentration greater than 1 g/L, the dye adsorption density remains relatively unchanged. It is found that the increase in the ionic strength decreases the dye adsorption density. Dye adsorption can be described by a multilayer adsorption isotherm. The multilayer adsorption model allows the calculation of both the monolayer adsorption density (i.e., the maximum first layer adsorption density) and the equilibrium constants for the first layer and subsequent adsorption. Based on the monolayer adsorption capacity, it is possible to determine the specific surface area of various sludge particles. Copyright 1998 Academic Press.

Expression and purification of correctly processed, active human TACE catalytic domain in Saccharomyces cerevisiae

Human tumor necrosis factor-alpha (TNF alpha) converting enzyme (TACE) releases soluble TNF alpha from cells. It is a member of the adamalysin family of metalloproteases. A truncated form of TACE cDNA was expressed in Saccharomyces cerevisiae and purified to homogeneity in order to study TACE structure and function. Recombinant TACE was expressed as a preproprotein including the pro- and catalytic (PROCAT) domains fused to the yeast alpha-factor leader. A C-terminal immunoreactive FLAG peptide was added for Western blot detection and anti-FLAG antibody column purification. We constructed two glycosylation mutant PROCAT TACE isoforms to facilitate purification. A PROCAT isoform, mutated to eliminate two N-linked glycosylation sites, was buffer exchanged and purified to homogeneity by ion exchange chromatography and an anti-FLAG antibody affinity step. N-terminal sequence analysis showed that the mutant preproprotein was processed in yeast at the furin protease cleavage site and yielded an active catalytic domain which has TNF alpha peptide-specific protease activity. Mass spectrometry of the purified catalytic domain showed that removal of both N-linked sites results in a homogeneous sized polypeptide lacking further posttranslational modifications.

Cloning and characterization of TRAIL-R3, a novel member of the emerging TRAIL receptor family

TRAIL-R3, a new member of the TRAIL receptor family, has been cloned and characterized. TRAIL-R3 encodes a 299 amino acid protein with 58 and 54% overall identity to TRAIL-R1 and -R2, respectively. Transient expression and quantitative binding studies show TRAIL-R3 to be a plasma membrane-bound protein capable of high affinity interaction with the TRAIL ligand. The TRAIL-R3 gene maps to human chromosome 8p22-21, clustered with the genes encoding two other TRAIL receptors. In contrast to TRAIL-R1 and -R2, this receptor shows restricted expression, with transcripts detectable only in peripheral blood lymphocytes and spleen. The structure of TRAIL-R3 is unique when compared to the other TRAIL receptors in that it lacks a cytoplasmic domain and appears to be glycosyl-phosphatidylinositol-linked. Moreover, unlike TRAIL-R1 and -R2, in a transient overexpression system TRAIL-R3 does not induce apoptosis.

Identification and characterization of a new member of the TNF family that induces apoptosis

A novel tumor necrosis factor (TNF) family member has been cloned and characterized. This protein, designated TNF-related apoptosis-inducing ligand (TRAIL), consists of 281 and 291 aa in the human and murine forms, respectively, which share 65% aa identity. TRAIL is a type II membrane protein, whose C-terminal extracellular domain shows clear homology to other TNF family members. TRAIL transcripts are detected in a variety of human tissues, most predominantly in spleen, lung, and prostate. The TRAIL gene is located on chromosome 3 at position 3q26, which is not close to any other known TNF ligand family members. Both full-length cell surface expressed TRAIL and picomolar concentrations of soluble TRAIL rapidly induce apoptosis in a wide variety of transformed cell lines of diverse origin.

Ti:sapphire amplifier producing millijoule-level, 21-fs pulses at 1 kHz

We have developed a Ti:sapphire amplifier system capable of producing pulses of 1 mJ, with 20-22-fs pulse duration, at a 1-kHz repetition rate. The amplifier has a unique design consisting of a three-mirror multipass ring configuration with a highly doped Ti:sapphire crystal as the gain medium. Pulses of 15-fs duration from a Ti:sapphire oscillator are temporally stretched and injected into the amplifier, which is an eight-pass system with a total gain of 10(6). The amplif ier is more than 10% efficient, and the shot-to-shot energy fluctuation of the output is less than 2%. The output beam focuses to 1.8 times the diffraction limit.

Clinical application of coralline hydroxyapatite ocular implants in the eviscerated eyes

BACKGROUND

During the past several years, coralline hydroxyapatite ocular implant has gained increasingly wide acceptance among ophthalmologists. This ocular implant is used in eviscerated eyes to restore volume loss. Its advantages and complications are presented.

METHODS

Seventy-three patients received a coralline hydroxyapatite sphere as a buried integrated ocular implant after evisceration surgery between August 1991 and May 1994. The follow-up period was from 4 to 33 months, with mean of 13.5 months.

RESULTS

There have been no recognizable cases of orbital infection, implant extrusion, or implant migration. Complications have been minimal and easily managed. Motility of the socket and fornices has been excellent, and most patients have cosmetically satisfactory motility of the prosthesis.

CONCLUSIONS

The hydroxyapatite implant appears to offer excellent cosmetic reconstruction without the unacceptable infection and extrusion rates seen with other implants.

Space-time focusing of femtosecond pulses in a Ti:sapphire laser

We present what is to our knowledge the first three-dimensional model of a femtosecond pulse propagating in a Ti:sapphire laser crystal, which includes dispersion, self-focusing, and finite response time of the medium and does not assume the slowly varying envelope approximation. The combined action of material dispersion and phase modulation leads to a dramatic space-time focusing on the pulse. Dispersion prevents catastrophic selffocusing and self-steepening of the pulse, even though the peak power of the pulse is much greater than the critical power for self-focusing filamentation. Extrapolation of these results to shorter-pulse durations shows that this space-time focusing mechanism can operate even for pulses with durations close to the response time of the Kerr nonlinearity.

Amplification of 26-fs, 2-TW pulses near the gain-narrowing limit in Ti:sapphire

We report the generation of 26-fs-duration pulses, with an energy of 60 mJ, from a simple multipass Ti:sapphire amplifier system. The peak power of our amplified pulses is 2 TW, and the repetition rate is 10 Hz. Our amplifier design consists of two highly doped multipass amplifiers and is simple and compact. We use an all-reflective, low-groove-density grating stretcher and compressor, combined with a relatively short material path length in the amplifier. This design allows us to minimize higher-order dispersion. The result is a laser system that generates multiterrawatt transform-limited pulses, with good beam quality and low amplified-spontaneous-emission levels, at a duration near the theoretical limit imposed by gain narrowing in Ti:sapphire.

Fourth-order dispersion-limited solitary pulses

We analyze the performance of a Ti:sapphire self-mode-locked laser with near-zero second- and third-order dispersion. Our simulations show that, in the presence of fourth-order dispersion, solitary laser pulses can be supported within a wide parameter range, close to the experimental values of these parameters. We also conclude that it is possible to generate pulses much shorter than 10 fs if fourth-order dispersion is further reduced.

Pulse evolution in a broad-bandwidth Ti:sapphire laser

We demonstrate that by operating near the zero second- and third-order dispersion point in a self-mode-locked Ti:sapphire laser we can generate sub-10-fs pulses. Our numerical simulations show that the pulse duration is limited by fourth-order dispersion and that shorter pulses will be possible if this can be reduced. Also, by inserting a pellicle in various positions in a Ti:sapphire cavity, we have measured the intracavity pulse duration and chirp of the circulating pulse in the laser. Our results demonstrate that the pulse is shortest near the middle of the laser crystal, in one direction of propagation. In the other direction of propagation, the pulse is positively chirped and several times longer.

Generation of 11-fs pulses from a self-mode-locked Ti:sapphire laser

By optimizing the intracavity dispersion compensation in a self-mode-locked Ti:sapphire laser, we have generated pulses of 10.95-fs duration. Dispersion within the laser cavity is reduced by use of a short 4.5-mm highly doped Ti:sapphire crystal and fused-silica prisms. The output from the laser has an average power of as much as 500 mW, with a wavelength centered at 780 nm and a bandwidth of 62 nm. Our results demonstrate that the exceptionally broad bandwidth of Ti:sapphire can be utilized to generate pulses that, to our knowledge, are shorter than has been possible with any other type of laser material to date.

17-fs pulses from a self-mode-locked Ti:sapphire laser

We have generated sub-17-fs-duration pulses directly from a self-mode-locked Ti:sapphire laser. These pulses are near transform limited, with a wavelength centered at 817 nm, a pulse repetition rate of 80 MHz, and an average power of 500 mW. By minimizing the amount of material inside the laser cavity and choosing the correct glass for the intracavity prism pair, third-order dispersion in the laser can be significantly reduced compared with that in previous designs. Extracavity compensation for group-velocity dispersion in the output coupler and autocorrelator optics is necessary to measure this pulse width. To our knowledge this laser generates pulses substantially shorter than any other laser to date.

[Pancreatoblastoma: report of one case]

Pancreatoblastoma is an extremely rare pancreatic tumor in childhood, comprising 0.5% of pancreatic non-endocrine tumors. It mostly affects children of under 8 years old without special sexual predilection. Abdominal mass is the dominant clinical feature and abdominal X-ray, sonography, UGI series, CT scan are of assistance in establishing diagnosis. The presence of acinar cells with zymogen granules, squamous metaplasia and endocrine components makes the diagnosis. We report a case of 4-year-old girl, who suffered from abdominal pain for two months. Abdominal mass was found at our OPD and abdominal sonography, UGI series, CT scan all indicated a parapancreatic tumor. AFP was 4700 ng/ml. Laparotomy confirmed a pancreatic tumor and only partial excision was performed due to tumor invasion and adhesion to major vessels. Diagnosis of pancreatoblastoma was made by pathohistology, cytochemical special stains and electronic microscopic examination of the tumor. Neither chemotherapy nor radiotherapy was performed due to family refusal. Then patient followed up at NTUH OPD regularly. Unfortunately patient expired because of the regrowth of residual tumor eight months later.

Photochemotherapy of generalized granuloma annulare

Various forms of treatment for generalized granuloma annulare have been employed with little success. The results of treatment with topical and intralesional corticosteroids, as well as systemic therapy with corticosteroids, salicylates, aspirin, niacinamide, and chloroquine, have been generally disappointing. We describe five patients with generalized granuloma annulare of several years' duration who were treated with oral psoralen plus ultraviolet A irradiation. Lesions were present on the extremities, buttocks, and trunk in the form of macules, papules, and plaques. One patient also had perforating lesions on her thighs. Flattening of the lesions with decreased erythema and pigmentation was noted as early as 1 month after initiation of treatment. Complete clearance was achieved in all patients. Maintenance therapy has been required, resulting in prolonged disease-free intervals. Although the mechanism of action of oral psoralen plus ultraviolet A irradiation in granuloma annulare is unclear, one possibility is selective elimination of the cells that are responsible for initiating the disease.

Meiotic origin of triploidy in the frog detected by genetic analysis of enzyme polymorphisms

A female frog heterozygous at two unlinked loci, specifying electrophoretic forms of mannosephosphate isomerase (MPI) and malate dehydrogenase (MDH) was crossed to male frogs homozygous for different alleles at each locus. In the offspring approximately ten percent proved to be triploid according to nucleolar and chromosome counts of tail tip cells. Most of these triploids had both maternal alleles at the MDH and MPI loci suggesting that the first meiotic division was repressed. Others seemed to represent a repressed second meiotic division and one animal, a pentaploid, could only have resulted from inhibition of both meiotic divisions of the egg. Densitometer tracings of starch gels stained for 6 phosphogluconate and isocitrate dehydrogenases, expected to be heterozygous in a particular cross, demonstrated that the triploids had twice as much maternal as paternal gene product for each locus, similar to patterns found in triploids produced by nuclear transplantation.

Adsorpition of tryptophan onto calcum carbonate surface

Adsorption of tryptophan onto CaCO3 at constant ionic strength (0.05 M Nacl) and from dilute aqueous solution (10(-4) M to 10(-3) M tryptophan) is reported. Adsorption was primarily determined by the charge characteristics of both the adsorbate amino acid and adsorbent CaCO3. When both adsorbate and adsorbent are semicharged, tryptophan ions are expelled away from the CaCO3-solution interface. Tryptophan is only removed by CaCO3 in a narrow pH range, 6.0 greater than pH less than 8.5 within which CaCO3 has positive charges, and tryptophan is negatively charged. The pH of zero point of charge, pHzpc, of CaCO3 was also determined by alkalimetric tritration and coagulation techniques and a value of 9.50 +/- 0.5 was found. These preliminary finding demonstrate primarily that interfacial chemical reactions play an important role in the temporal and spatial transformation of dissolved organic matter in natural water systems.