Context. Molecular clouds trace the spiral arms of the Milky Way and all its star forming regions. Large-scale mapping of molecular clouds will provide an approach to understand the processes that govern star formation and molecular cloud evolution.Aims. As a part of the Milky Way Imaging Scroll Painting (MWISP) survey, the aim is to study the physical properties of molecular clouds and their associated star formation toward the Galactic plane within 216.25 degrees <= l <= 218.75 degrees and -0.75 degrees <= b <= 1.25 degrees, which covers the molecular cloud complex S287.Methods. Using the 3 x 3 Superconducting Spectroscopic Array Receiver (SSAR) at the PMO-13.7m telescope, we performed a simultaneous (CO)-C-12 (1-0), (CO)-C-13 (1-0), (CO)-O-18 (1-0) mapping toward molecular clouds in a region encompassing 3.75 square degrees. We also make use of archival data to study star formation within the molecular clouds.Results. We reveal three molecular clouds, the 15 km s(-1) cloud, the 27 kms(-1) cloud, and the 50 km s(-1) cloud, in the surveyed region. The 50 kms(-1) cloud is resolved with an angular resolution of similar to 1' for the first time. Investigating their morphology and velocity structures, we find that the 27 kms(-1) cloud is likely affected by feedback from the stellar association Mon OB3 and the 50 kms(-1) cloud is characterized by three large expanding molecular shells. The surveyed region is mapped in (CO)-O-18 (1-0) for the first time. We discover seven (CO)-O-18 clumps that are likely to form massive stars, and 15 dust clumps based on the Bolocam Galactic Plane Survey (BGPS) archive data. Using infrared color-color diagrams, we find 56 Class I and 107 Class II young stellar object (YSO) candidates toward a slightly larger region of 5.0 square degrees. Based on the distribution of YSO candidates, an overdensity is found around the HII region S287 and the intersection of two shells; this is probably indicative of triggering. The star formation efficiency (SFE) and rate (SFR) of the 27 km s(-1) cloud are discussed. Comparing the observed values of the filament S287-main with fragmentation models, we suggest that turbulence controls the large-scale fragmentation in the filament, while gravitational fragmentation plays an important role in the formation of YSOs on small scales. We find that star-forming gas tends to have a higher excitation temperature, a higher (CO)-C-13 (1-0) opacity, and a higher column density than non-star-forming gas, which is consistent with the point that star formation occurs in denser gas and star-forming gas is heated by YSOs. Using the 1.1 mm dust emission to trace dense gas, we obtain a dense gas fraction of 2.7-10.4% for the 27 km s(-1) cloud.

Tin whisker growth has been observed on the surface of bulk Sn-Nd alloys with Nd contents of 30, 5 and 0.5 wt%, under ambient conditions of temperature and atmosphere. It is shown that the whiskers originate from the area of Sn-Nd intermetallic compounds after a very short incubation period and that they exhibit a relatively high growth rate on the surface of the bulk alloys. The results show that these Sn-based, rare-earth alloys have a very strong propensity to grow tin whiskers, i. e. this rare-earth element in tin is a catalytic agent for whisker growth. Direct evidence is also shown that whiskers can grow from the surface of a bulk Sn-based alloy.

The confined crystallization behavior of polycaprolactone (PCL) in thin and ultrathin films was studied by AFM (atomic force microscopy). It was found that the crystalline morphology of PCL depended on the film’s thickness. When the thickness is d > 2 Rg (radius of gyration), the polymer can crystallize into spherulites; when Rg < d < 2 Rg, a dense-branch morphology and dendrites could be found; when d < Rg, an “islands” structure could be obtained. Moreover, the effects of the crystallization temperature and the substrate and the molecular weight on the crystalline morphology were discussed. It was shown that the crystallization of PCL in thin films is a diffusion-controlled process, and it can be explained by diffusion-limited aggregation.

采用溶胶-凝胶法制备了不同烧结温度的钙钛矿类锰氧化物La0.67Sr0.33MnO3样品.实验结果表明,在1 573 K以上烧结的样品,晶粒出现异常长大,晶界效应明显.随着烧结温度的提高,磁化强度逐渐增大,但样品的居里温度基本不变.此外,在1 173和1 573 K温度下烧结的样品,均出现了低于居里温度的金属-半导体导电行为转变.在合适的烧结条件下,可以观察到隧道磁电阻(TMR)和超大磁电阻(CMR)2种磁电阻效应.实验表明,自旋电子的输运,不仅与样品平均粒径的大小和密度有关,而且与晶界的微观结构有密切关系.

The ordered double perovskites SrLaMnBO_(6)(B:Mo,W) were prepared by sol-gel reaction.The XRD results suggest that the crystal structure of SrLaMnMoO_(6) belongs to the monoclinic P2_(1)/n space group and that of SrLaMnWO_(6) belongs to the tetragonal I4/m space group.The competition between band filling effect and steric effect results in the expansion of cell volume for SrLaMnBO_(6)(B:Mo,W).Magnetic measurements indicated that both samples showed very weak ferro-/ferrimagntism,but the magnetic moments at H=0(extrapolated) from the magnetic moment vs applied magnetic field curves are 0.72μ_(B) and 0.16μ_(B) for SrLaMnMoO_(6) and SrLaMnWO_(6),respectively,much smaller than the expected net magnetic moments.From the(temperature) dependence of magnetization for SrLaMnMoO_(6),ferromagnetic-paramagnetic transition is(observed),which is not shown for SrLaMnWO_(6).

A new solvothermal route has been developed for synthesizing the size-controlled CdSe nanocrystals with relatively narrow size distribution, and the photoluminescence (PL) quantum yields (QYs) of the nanocrystals can reach 5–10%. Then the obtained CdSe nanocrystals served as cores to prepare the core/shell CdSe/CdS nanocrystals via a two-phase thermal approach, which exhibited much higher PL QYs (up to 18–40%) than the CdSe core nanocrystals. The nanocrystal samples were characterized by ultraviolet–visible (UV–vis) absorption spectra, PL spectra, wide-angle X-ray diffraction (WAXD), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM).

The mono-armed CdS nanorods with a few multi-armed nanorods were synthesized through a reaction of CdCl2 with thioacetamide(TAA) under basic conditions at room temperature in the presence of the rod-shaped micellar template of cetyltrimethylammonium bromide (CTAB). The length of the arms can be controlled via adjusting the amount of cyclohexane. To some extent, more cyclohexane results in longer nanorods. The nanorods can be prepared with a diameter of 26 - 48 nm and a length of 240-1 200 nm through this approach. The resulting nanorods were characterized by wide-angle X-ray diffraction (WAXD ) , transmission electron microscopy (TEM) , selected area electron diffraction ( SAED) and X-ray photoelectron spectroscopy( XPS).

Novel organic–inorganic hybrid composite films with ternary lanthanide complex covalently bonded with silica matrix were prepared in situ via co-ordination of N-(3-propyltriethoxysilane)-4-carboxyphthalimide (TAT) and 1,10-phenanthroline (Phen) with europium ion (Eu3+) during a sol–gel approach and characterized by the means of spectrofluorimeter, phosphorimeter and infrared spectrophotometer (FTIR). The resulting transparent films showed improved photophysical properties, i.e. increased luminescence intensity and longer luminescence lifetime, compared with the corresponding binary composite films without Phen. All the results revealed that the intense luminescence of the composite film was attributed to the efficient energy transfer from ligands, especially Phen, to chelated Eu3+ and the reduced non-radiation through the rigid silica matrix and “site isolation”.

Teardrop-shaped and tetrapod-shaped CdS nanocrystals were prepared in aqueous solution under mild conditions through adjusting the concentration of reactants and the equilibrium reaction.Effects of the(precursors) on nanorods were further discussed.TEM images showed that nanocrystals had a narrow size distribution and a controllable aspect ratio(1~7) to some extent,and XRD measurement confirmed the wurtzite structure for the resulting CdS nanorods.

The ordered double perovskites, Sr2 – xLaMnMoO6, were prepared by sol-gel reaction. Structural, magnetic, and electrical properties were investigated for a series of ordered double perovskites Sr2 – xLaxMnMoO6 (0 ≤ x ≤ 1). The compounds have a monoclinic structure (space group P21/n) and the cell volume expands monotonically with La doping. The Tc and the magnetic moment rise and the cusp-like transition temperature below which the magnetic frustration occurs shifts to high temperature as x increases. With La doping, electrical resistivity of Sr2 – xLaxMnMoO6 decreases only at low doping levels (x ≤ 0.2); while at high doping levels (0.8 ≤ x ≤ 1), electrical resistivity tends to increase greatly. The results suggest that the competition between band filling effect and steric effect coexists in the whole doping range, and the formation of ferrimagnetic interactions is not simply at the expense of antiferromagnetic interactions.

The single-phase double perovskites Sr2MWO6 (M=Co, Ni) were prepared by sol-gel method. Crystal Structure, magnetic properties and the morphology of Sr2CoWO6 and Sr2NiWO6 were investigated. X-ray powder diffraction (XRD) analysis shows single phase structure for Sr2MWO6 (M=Co, Ni) without any traces of impurities and the crystal structure of all the samples belongs to the tetragonal I4/m space group. SEM image for Sr2MWO6 (M=Co, Ni) indicate that the grains are homogeneous and connect each other very well. The Neel temperature for Sr2CoWO6 and Sr2NiWO6 are 23 K and 59 K, respectively. Magnetic measurements showed that the magnetic moment in these double perovskites originates mainly from the interactions between Ni ions and Co ions.

The size- and shape-controlled CdSe and CdTe nanocrystals, which exhibit obvious quantum confinement effect, have been synthesized by a solvothermal route. It is found that initial precursor concentrations are key factors in controlling the shape of the resulting nanocrystals. Moreover, the obtained nanocrystals are all of zinc blende structure, regardless of their sizes and shapes. A possible mechanism for the formation and growth of the nanocrystals is put forward. It is inferred that the adhesion and subsequent recrystallization of nanocrystals with an assistance of remaining monomers should be a major reason for formation and growth of the elongated nanocrystals.

Confined crystallization behavior of poly(epsilon-caprolactone) was studied by DSC,WAXD and SAXS in the mixtures of poly(epsilon-caprolactone) (PCL) and poly(styrene-co-acrylonitrile) (SAN). Because the crystallization and melting temperatures of PCL are lower than the glass transition temperature of SAN, the experimental results indicated that multi-scale crystallization behavior of PCL is confided in the mixtures. DSC measurements showed that the crystallinity of PCL is reduced with increasing the SAN concentration in mixtures. WAXD and SAXS results indicated that both PCL crystallite size and lamellae structure are disturbed by SAN with high glass transition temperature in the mixtures.

High-quality CdSe quantum dots have been synthesized through an organometallic method with cadmium methoxide as a cadmium precursor. Without any size sorting, the FWHM (full width at half-maximum) in PL spectra almost for all CdSe samples is less than 30 nm and only 22 nm from the best sample. The emission peaks with different particle size in toluene can be tuned from 478 to 654 nm corresponding to a color change from blue-green to red.

The transition of crystalline morphology is revealed in poly(E-caprolactone) (PCL) thin films as the polymer film thickness changes from hundreds of nanometers to several nanometers. The PCL can crystallize into spherulites, densebranching morphology (DBM), or dendrites, depending on the polymer film thickness. It was found that when the polymer film thickness approaches 2Rg (radius of gyration of polymer), there is a remarkable change in crystalline morphology. Under this condition, the polymer crystallization is a diffusion-controlled process. When the value of polymer film thickness closes to Rg, PCL cannot crystallize, and a dewetting phenomenon will take place. Moreover, polymer morphology can be controlled by varying supercooling. The effect of molecular weight on polymer morphology has been investigated. The main factors that affected pattern formation in nonequilibrium crystallization are also discussed. (c) 2005 Wiley Periodicals, Inc.

. The surface topography of thin diblock copolymer films is studied by atomic force microscopy (AFM). With AFM an island-to-ribbon transition is observed for symmetric polystyrene-b-poly (4-vinylpyridine) (PS-b-P4VP) on mica with increasing solution concentration. Our study also demonstrates how the formation of the pattern strongly depends on the copolymer composition based on the volume fraction. The substrate and solvent used both have great effects on the morphology of the thin films. Only by using highly polar substrate (mica), can we gain regular pattern. The reason why the regular islands cannot be obtained with symmetric PS-b-P4VP on graphite is also explained. On mica using nonselective and selective solvents, a rather regular pattern can be obtained. The difference is only in the solution concentration for forming regular patterns.

The time development of the surface morphology of asymmetric polystyrene-b-poly(4-vinylpyridine) (PS-b-P4VP) thin films ‘annealing’ in methanol vapor, a selective solvent for minority P4VP block, was investigated by atomic force microscopy(AFM). For PS-b-P4VP with cylindrical structure in bulk, as annealing time progressed, the surface morphology underwent structural transitions from featureless topography to hybrid morphology of cylindrical and spherical pits, to cylinders, to nanoscale depressions, back to cylinders again. The different film thickness made the number of the transitions observed, at any given annealing time, different. The thicker the film is the more transitions at a given annealing time can be observed. If the film was not thick enough, depressions appeared. For PS-b-P4VP with spherical structure in bulk, it displayed nanoscale depressions with the annealing time increasing. A possible mechanism of the transition of morphologies during solvent annealing was proposed.

A new two-phase route has been developed to synthesize high-quality CdS nanocrystals with a narrow size distribution and a high photoluminescence (PL) quantum yield (QY). In the two-phase system, toluene and water were used as separate solvents for cadmium myristate (CdM2) and thiourea, which served as cadmium source and sulfur source, respectively, and oleic acid (OA) was used as a ligand for stabilizing the nanocrystals. The reactions were completed in the heated autoclaves. The initial Cd/S molar ratio of the precursors and the reaction temperature were found to be factors that affected the growth of nanocrystals. Furthermore, a seeding-growth technique was developed to synthesize CdS nanocrystals of different sizes, which exhibit PL peaks with quite similar full width at half-maximum (FWHM) values compared to those of the initial nanocrystal seeds in all cases.

A simple, productive, low-cost route has been developed to synthesize the high-quality 1-D nanorods of CdE (E = Se, Te) with 3-8 nm in diameter and 5-40 nm in length using myristic acid as a complexing agent. Moreover, the reaction is performed under mild conditions and relatively low temperatures. The Xray powder diffraction patterns confirmed the CdE nanorods with wurtzite structure.