Effect of operating parameters and reactor structure on moderate temperature dry desulfurization

A moderate temperature dry desulfurization process at 600-800 degrees C was studied in a pilot-scale circulating fluidized bed flue gas desulfurization (CFB-FGD) experimental facility. The desulfurization efficiency was investigated for various operating parameters, such as bed temperature, CO2 concentration, and solids concentration. In addition, structural improvements in key parts of the CFB-FGD system, i.e., the cyclone separator and the distributor, were made to improve the desulfurization efficiency and flow resistance. The experimental results show that the desulfurization efficiency increased rapidly with increasing temperature above 600 degrees C due to enhanced gas diffusion and the shift of the equilibrium for the carbonate reaction. The sorbent sulfated gradually after quick carbonation of the sorbent with a long particle residence time necessary to realize a high desulfurization ratio. A reduced solids concentration in the bed reduced the particle residence time and the desulfurization efficiency. A single-stage cyclone separator produced no improvement in the desulfurization efficiency compared with a two-stage cyclone separator. Compared with a wind cap distributor, a large hole distributor reduced the flow resistance which reduced the desulfurization efficiency due to the reduced bed pressure drop and worsened bed fluidization. The desulfurization efficiency can be improved by increasing the collection efficiency of fine particles to prolong their residence time and by improving the solids concentration distribution to increase the gas-solid contact surface area.

Unassisted membrane insertion as the initial step in DeltapH/Tat-dependent protein transport

In the thylakoid membrane of chloroplasts as well as in the cytoplasmic membrane of bacteria, the DeltapH/Tat-dependent protein transport pathway is responsible for the translocation of folded proteins. Using the chimeric 16/23 protein as model substrate in thylakoid transport experiments, we dissected the transport process into several distinct steps that are characterized by specific integral translocation intermediates. Formation of the early translocation intermediate Ti-1, which still exposes the N and the C terminus to the stroma, is observed with thylakoids pretreated with (i) solutions of chaotropic salts or alkaline pH, (ii) protease, or (iii) antibodies raised against TatA, TatB, or TatC. Membrane insertion takes place even into liposomes, demonstrating that proteinaceous components are not required. This suggests that Tat-dependent transport may be initiated by the unassisted insertion of the substrate into the lipid bilayer, and that interaction with the Tat translocase takes place only in later stages of the process.

Toc, Tic, Tat et al.: structure and function of protein transport machineries in chloroplasts

The chloroplast is an organelle of prokaryotic origin that is situated in an eukaryotic cellular environment. As a result of this formerly endosymbiotic situation, the chloroplast houses a unique set of protein transport machineries. Among those are evolutionarily young transport pathways which are responsible for the import of the nuclear-encoded proteins into the organelle as well as ancient pathways operating in the 'export' of proteins from the stroma (the former cyanobacterial cytosol) across the thylakoid membrane into the thylakoid lumen. In this review, we have tried to address the main features of these various transport pathways.

[Immunohistochemical analysis of cell cycle-associated proteins p27 in oral cancer and precancer]

OBJECTIVE

To evaluate the expression of p27 protein in oral precancerous lesions and oral squamous cell carcinoma (OSCC).

METHODS

Immunohistochemistry was used to detect p27, p53, murine double minute (MDM2) and p21 protein expression in a series of 13 specimens with simple hyperplasia, 44 with dysplasia and 48 with OSCC. An attempt was made to correlate the protein levels with clinicopathologic parameters and Ki-67 protein levels.

RESULTS

Positive p27 staining was present in 79.55% of the dysplasia samples, as well as in 81.25% of the OSCC samples. p27 protein overexpression in OSCC group was significantly higher than that in leukoplakia group (P < 0.001). The extent of p27 expression was positively associated with Ki-67 expression (P < 0.001). Cases with p27 overexpression displayed concurrent expression of p53 and/or MDM2 (P = 0.034) in OSCC group.

CONCLUSIONS

p27, p53, MDM2 and p21 may all play important roles in the genesis of OSCC. The alterations of one or more cell cycle regulators are prevalent in oral premalignant lesions and OSCC and the regulators can regulate each other.

Femtosecond microscopy of radial energy transport in a micrometer-scale aluminum plasma excited at relativistic intensity

Using femtosecond microscopy, we observe subpicosecond transport of thermal energy radially outward from a micrometer-sized spot of an aluminum target following P-polarized excitation at >10(18) W/cm2 with a 24 fs pulse. The rapid expansion coincides with the onset of nonlocal energy transport dominated by radiation and hot electrons.

Tuning of photonic bandgaps by a field-induced structural change of fractal metamaterials

Bandgaps of a structure with electrorheological fluids sandwiched between planar metallic fractal electrodes are investigated in the microwave regime. Our results show that bandgaps are tunable as a result of the electrorheological effect induced by the external electric field applied directly to the structure. A finite-difference time-domain simulation reveals that the tunability of bandgaps is not related to the average dielectric constant but is caused by the field-induced structural change in the electrorheological fluids.

Resonance-induced wave penetration through electromagnetic opaque object

The enhanced transmission of electromagnetic waves through an opaque object is reported in this paper. The samples are constructed as two different configurations: a subwavelength metallic mesh sandwiched either between two metallic plates with periodic fractal slots (ABA for short) or between two plastic plates with periodic metallic fractals (CBC for short). Such ABA or CBC configuration exhibits multiple transmission peaks, indicating the wave penetrations through the opaque metallic mesh. The experimental observations and theoretical simulations demonstrate that the transmission enhancements for two configurations are induced by local resonances in the sandwiching layers.

Hydrothermal synthesis, characterization, and photocatalytic performance of silica-modified titanium dioxide nanoparticles

Silica-modified titanium dioxides were prepared by a hydrothermal method and then characterized by XRD, FT-IR, XPS, TEM, and UV-visible spectroscopy. The silica-modified titanium dioxides were in anatase phase and had large surface areas. There was strong interaction between SiO2 and TiO2, and TiOSi bonds formed during the hydrothermal process. The addition of silica in TiO2 particles could effectively suppress the formation of the rutile phase and the growth of titanium dioxide crystals. DRS spectra proved an increase in the band-gap transition with the increase of silica. The silica-modified TiO2 nanoparticles exhibited better photocatalytic activity, which increased with the silica amount, in comparison with pure TiO2 nanoparticles. Due to better thermal stability, the photocatalytic activity of the silica-modified TiO2 sample held good photocatalytic activity even after calcined at 1273 K.

Relativistic generation of isolated attosecond pulses in a lambda 3 focal volume

Lasers that provide an energy encompassed in a focal volume of a few cubic wavelengths (lambda(3)) can create relativistic intensity with maximal gradients, using minimal energy. With particle-in-cell simulations we found, that single 200 attosecond pulses could be produced efficiently in a lambda(3) laser pulse reflection, via deflection and compression from the relativistic plasma mirror created by the pulse itself. An analytical model of coherent radiation from a charged layer confirms the pulse compression and is in good agreement with simulations. The novel technique is efficient (approximately 10%) and can produce single attosecond pulses from the millijoule to the joule level.

Non-isomerizable artificial pigments: implications for the primary light-induced events in bacteriorhodopsin

The primary events in the photosynthetic retinal protein bacteriorhodopsin (bR) are reviewed in light of photophysical and photochemical experiments with artificial bR in which the native retinal polyene is replaced by a variety of chromophores. Focus is on retinals in which the "critical" C13=C14 bond is locked with respect to isomerization by a rigid ring structure. Other systems include retinal oxime and non-isomerizable dyes noncovalently residing in the binding site. The early photophysical events are analyzed in view of recent pump-probe experiments with sub-picosecond time resolution comparing the behavior of bR pigments with those of model protonated Schiff bases in solution. An additional approach is based on the light-induced cleavage of the protonated Schiff base bond that links retinal to the protein by reacting with hydroxylamine. Also described are EPR experiments monitoring reduction and oxidation reactions of a spin label covalently attached to various protein sites. It is concluded that in bR the initial relaxation out of the Franck-Condon (FC) state does not involve substantial C13=C14 torsional motion and is considerably catalyzed by the protein matrix. Prior to the decay of the relaxed fluorescent state (FS or I state), the protein is activated via a mechanism that does not require double bond isomerization. Most plausibly, it is a result of charge delocalization in the excited state of the polyene (or other) chromophores. More generally, it is concluded that proteins and other macromolecules may undergo structural changes (that may affect their chemical reactivity) following optical excitation of an appropriately (covalently or non-covalently) bound chromophore. Possible relations between the light-induced changes due to charge delocalization, and those associated with C13=C14 isomerization (that are at the basis of the bR photocycle), are discussed. It is suggested that the two effects may couple at a certain stage of the photocycle, and it is the combination of the two that drives the cross-membrane proton pump mechanism.

[Pyruvate oxidase gene from Streptococcus sanguis: molecular cloning and sequence analysis of the gene]

OBJECTIVE

To clone and sequence the gene of pyruvate oxidase (Sopox) from Streptococcus sanguis.

METHODS

The PCR primers for Sopox gene were designed and synthesized according to the sequence of pyruvate oxidase (spxB) gene of S. pneumonia. The amplified PCR product was cloned into pUC18 and then subcloned into M13mp18 and M13mp19. The DNA sequence of the gene was analyzed.

RESULTS

Sopox gene was successfully amplified from S. sanguis ATCC10557. The nucleotide sequence of the whole gene was revealed to be 1788 base pairs with one open reading frame coding pyruvate oxidase with 591 amino acid residuals.

CONCLUSION

The clone and DNA sequence of Sopox gene were obtained which could serve as a foundation on which to elucidate the molecular mechanisms of hydrogen peroxide production and its regulation by oral streptococci.

[Expression of pyruvate oxidase gene sopox from Streptococcus sanguis in E. coli]

OBJECTIVE

To reconstruct the expression plasmid of Sopox gene for further understanding the regulation of its expression.

METHODS

Sopox was recombined with expression vector pBV220 and the expression of Sopox in E. coli JM105 was observed after transformation.

RESULTS

pBV220/Sopox/JM105 expressed a protein with molecular weight of 65 kd on SDS-PAGE after induction, and the expression reached the maximal amount with induction at 42 degrees C for 4 hours.

CONCLUSION

Sopox was successfully cloned into pBV220 and expressed in E. coli JM105.

[Clinical and pathological characteristics of gastric stump cancer and recurrent gastric stump cancer]

OBJECTIVE

To study early diagnosis and rational treatment of gastric stump cancer and recurrent gastric stump cancer.

METHODS

The data of 27 patients with gastric stump cancer and 23 patients with recurrent gastric stump cancer were analysed retrospectively during the past 20 years based on their clinical and pathological findings.

RESULTS

The onset time was 10 years or more for gastric stump cancer and less than 10 years for recurrent gastric stump cancer after gastrectomy. Gastroscopy was better than double contrast radiography in diagnosis. Partial resection of gastric stump was performed for patients with early cancer at the anastomotic stoma of gastrojejunostomy. Total resection of gastric stump was made for other patients. Lymph node of the mesojejunum were dissected routinely because their metastasis rate was about 40.0% in patients with cancer of anastomotic stoma. The effect of surgical treatment was poor for patients with advanced cancer.

CONCLUSIONS

Regular gastroscopy is useful in detecting gastric stump cancer in patients with gastric cancer after gastrectomy, or in those years after removal benign. Malignancy was more evident in recurrent gastric stump cancer than in primary gastric cancer. Prognosis is good for early stage cases and poor for late stage cases after surgical treatment.

Right ventricular function of patients with septic shock: clinical significance

OBJECTIVE

To understand the effect of right ventricular dysfunction on circulatory supportive therapy in patients with septic shock.

METHODS

25 patients with septic shock who were admitted consecutively to the intensive care unit (ICU) of Peking Union Medical College Hospital were observed prospectively. Hemodynamic profile of the left side and right side heart was monitored with right ventricular ejection fraction catheter and transthoracic echocardiography. Intramucosal pH (pHi) and oxygen delivery were also monitored to illustrate any relation with patient outcome.

RESULTS

Stroke volume index (SVI) and right ventricular ejection fraction (RVEF) were significantly higher in survivors than in nonsurvivors (P < 0.01 and < 0.05, respectively). The pulmonary vascular resistance index (PVRI) was significantly lower in survivors (P < 0.01). At the onset of shock, the left ventricular end-diastolic volume index (LVEDVI) of both groups was very low, and steadily increased in survivors but not in nonsurvivors. Left ventricular ejection fraction (LVEF) and systemic vascular resistance index (SVRI) decreased during treatment, which were not different in both groups. Right ventricular end-diastolic volume index (RVEDVI) increased in both survivors and nonsurvivors. Oxygen delivery of nonsurvivors was significantly lower than that of survivors. LVEDVI and RVEF were correlated with SVI in both survivors and nonsurvivors.

CONCLUSIONS

The impairment of right heart function may be more severe than that of left heart function in the patients with early septic shock. "Right heart priority" must be seriously considered in supportive treatment of patients with septic shock. The present treatment of septic shock has significant limitations, and even aggravates the existing cardiac dysfunction.

Bacterial proteins carrying twin-R signal peptides are specifically targeted by the delta pH-dependent transport machinery of the thylakoid membrane system

Glucose-fructose oxidoreductase (GFOR), a periplasmic protein of Zymomonas mobilis, is synthesized as a precursor polypeptide with a twin-R signal peptide for Sec-independent protein export in bacteria. In higher plant chloroplasts, twin-R signal peptides are specific targeting signals for the Sec-independent delta pH pathway of the thylakoid membrane system. In agreement with the assumed common phylogenetic origin of the two protein transport mechanisms, GFOR can be efficiently translocated by the delta pH-dependent pathway when analyzed with isolated thylakoid membranes. Transport is sensitive to the ionophore nigericin and competes with specific substrates for the delta pH-dependent transport route. In contrast, neither sodium azide nor enzymatic destruction of the nucleoside triphosphates in the assays affects thylakoid transport of GFOR indicating that the Sec apparatus is not involved in this process. Mutagenesis of the twin-R motif in the GFOR signal peptide prevents membrane translocation of the protein emphasizing the importance of these residues for the transport process.