Characterization of a dual wavelength fibre laser based-on dumbbell configuration

This paper reports the design of a dual wavelength fibre laser system using a dumbbell shaped configuration. The oscillation of the lasing wavelength is completed via fibre loop mirrors with a tuneable bandpass filter. The output power, side mode suppression ratio and wavelength spacing of the lasers were investigated against the pump power for forward and backward pumping schemes. The output powers of 4.99 and 3.69 dBm at 1545.08 and 1547.28 nm, respectively, for forward pumping scheme. On contrary, the output powers of 1.93 and 2.14 dBm at 1546.12 and 1551.48 nm, respectively, for backward pumping scheme. The peak output powers of less than 1 dB difference are obtained without any adjustment of the intra-cavity loss over a wider spectral range.     

Oligo(fluorenyleneethynylenegermylene)s and their metallopolymers

Oligo(fluorenyleneethynylenegermylene)s and their polyplatinynes are synthesized and photophysically characterized; inclusion of heavy germylene bridges greatly boosts the phosphorescence decay rate in metallopolymers.     

Porosity characteristics and pore developments of various particle sizes palm kernel shells activated carbon (PKSAC) and its potential applications

The adsorption behaviour and the micro- and mesopore size distributions of commercial palm kernel shell activated carbons (PKSAC) and other commercial activated carbon are characterized. The results showed that PKSAC are predominantly microporous materials, where micropores account 68–79% of total porosity. On the other hand, commercial activated carbons: Norit SX Plus, Calgon 12×40, and Shirasagi “A” activated carbons contained high mesopore fraction ranging from 33 to 52%. The analysis showed that the degree of mesoporosity of PKSAC is increased steadily with the decrease of particle size. This is due to the presence of channels interconnect the smaller pores in the interior of smaller particle size PKSAC. The smaller size PKSAC particle that is highly mesoporous has preformed better on the adsorption of larger molecules such as methylene blue. On the other hand, bigger size PKSAC particle has better performance on the adsorption of smaller adsorbates such as iodine.     

1.54 and 1.75 μm infrared luminescence of Y2O3:Er

A new 1.75 μm infrared emission transition of Y₂O₃:Er³⁺ is assigned to the ⁴S_3/2 → ⁴I_9/2 transition of Er³⁺ ions situated at the C₂ sites of cubic RE₂O₃ (RE = Y, Gd, Lu). The intensities of features in the 1.54 μm ⁴I_15/2–⁴I_13/2 absorption transition due to Er³⁺ at S₆ and C₂ sites are consistent with the site occupation ratio and the relative magnetic dipole–electric dipole intensity contributions of Er³⁺ at the different sites. The 1.54 μm emission lines are predominantly from Er³⁺ ions at C₂ sites. The different behaviours of the emission intensities 1.75 and 1.54 μm groups with change in Er³⁺ dopant ion concentration, preparation technique, Yb³⁺ co-doping, temperature change and different excitation line are rationalized.     

The crystalline structures of carboxylic acid monolayers adsorbed on graphite

X-ray and neutron diffraction have been used to investigate the formation of solid crystalline monolayers of all of the linear carboxylic acids from C(6) to C(14) at submonolayer coverage and from C(8) to C(14) at multilayer coverages, and to characterize their structures. X-rays and neutrons highlight different aspects of the monolayer structures, and their combination is therefore important in structural determination. For all of the acids with an odd number of carbon atoms, the unit cell is rectangular of plane group pgg containing four molecules. The members of the homologous series with an even number of carbon atoms have an oblique unit cell with two molecules per unit cell and plane group p2. This odd-even variation in crystal structure provides an explanation for the odd-even variation observed in monolayer melting points and mixing behavior. In all cases, the molecules are arranged in strongly hydrogen-bonded dimers with their extended axes parallel to the surface and the plane of the carbon skeleton essentially parallel to the graphite surface. The monolayer crystal structures have unit cell dimensions similar to certain close-packed planes of the bulk crystals, but the molecular arrangements are different. There is a 1-3% compression on increasing the coverage over a monolayer.     

Temperature effect on porous silicon luminescence

A theoretical surface-state model of porousilicon luminescence is proposed. The temperature effect on the PhotoLuminescence (PL) spectrum for pillar and spherical structures is considered, and it is found that the effect is dependent on the doping concentration, the excitation strength, and the shape and dimensions of the Si microstructure. The doping concentration has an effect on the PL intensity at high temperatures and the excitation strength has an effect on the PL intensity at low temperatures. The variations of the PL intensity with temperature are different for the pillar and spherical structures. At low temperatures the PL intensity increases in the pillar structure, while in the spherical structure the PL intensity decreases as the temperature increases, at high temperatures the PL intensities have a maximum for both models. The temperature, at which the PL intensity reaches its maximum, depends on the doping concentration. The PL spectrum has a broader peak structure in the spherical structure than in the pillar structure. The theoretical results are in agreement with experimental results.     

水热法制备近红外发光NaLa(WO4)2∶Ln(Ln=Er, Nd)球形粒子的研究

利用水热法制备了NaLa（WO4）2∶Ln（Ln=Er,Nd）球形粉末,分别用XRD,TEM和发光光谱等对粉末的物相、形貌、发光性质进行研究。XRD和SEM结果表明：制得的NaLa（WO4）2∶Ln（Ln=Er,Nd）粉末为白钨矿晶型,分散性良好,粒度均匀,呈规则的球形,粒径为1μm左右。发光光谱的测试表明：样品的最佳掺杂浓度为1.0%;随着煅烧温度的增加,样品发光强度逐渐增大;700℃下煅烧时最佳煅烧时间是4 h。     

Metabotyping of human colorectal cancer using two-dimensional gas chromatography mass spectrometry

Colorectal cancer (CRC) is the fourth most common cause of death from cancer in the world. The limitations of the currently available methods and biomarkers for CRC management highlight the necessity of finding novel markers. Metabonomics can be used to search for potential markers that can provide molecular insight into human CRC. The emergence of two-dimensional gas chromatography time of flight mass spectrometry (GC?×?GC/TOFMS) has comprehensively enhanced the metabolic space coverage of conventional GC/MS. In this study, a GC?×?GC/TOFMS was developed for the tissue-based global metabonomic profiling of CRC. A Pegasus GC?×?GC/TOFMS (Leco Corp., St. Joseph, MI, USA) system comprising an Agilent 7890 GC and Pegasus IV TOFMS was used for this purpose. An Agilent DB-1 (30 m?×?250 μm?×?0.25 μm) fused silica capillary column and a Restek Rxi®-17 (1 m?×?100 μm?×?0.10 μm) fused silica capillary column were used as the primary and secondary columns, respectively. The method was applied for global metabonomic profiling of matched CRC and normal tissues (n?=?63) obtained from 31 CRC patients during surgery. An attempt was also made to compare GC?×?GC/TOFMS with GC/MS and NMR in similar application. The results showed that the metabotype associated with CRC is distinct from that of normal tissue and led to the identification of chemically diverse marker metabolites. Metabolic pathway mapping suggested deregulation of various biochemical processes such as glycolysis, Krebs cycle, osmoregulation, steroid biosynthesis, eicosanoid biosynthesis, bile acid biosynthesis, lipid, amino acid and nucleotide metabolism.

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Fig Workflow of GCGC/TOFMS metabonomic profiling of human colorectal cancer