Color and surface chemistry changes of extracted wood flour after heating at 120 °C     

Yao Chen  Mandla A. Tshabalala  Jianmin Gao  Nicole M. Stark  Yongming Fan 《Wood Science and Technology》2014,48(1):137-150

To investigate the effect of heat on color and surface chemistry of wood flour (WF), unextracted, extracted and delignified samples of commercial WF were heated at 120 °C for 24 h and analyzed by colorimetry, diffuse reflectance visible (DRV), attenuated total reflectance Fourier transform infrared (ATR-FTIR) and Fourier transform Raman (FT-Raman) spectroscopies. Unextracted samples showed a slight increase in CIEL^*a^*b^* color coordinates, a ^* and b ^*. Compared with unextracted samples, color changes of the extracted samples varied with composition of the extraction solvents with generally smaller increases in a ^* and larger decreases in b ^* values. Delignified samples were marked by even larger increases in both a ^* and b ^* values. The color changes could be explained by analysis of the respective DRV, FTIR and FT-Raman spectra of the samples before and after heating. Heating of the extracted WF at 120 °C resulted in a red shift of the absorption at 430 nm and increase in absorption in the violet-blue spectral region of visible light. Delignified samples showed even more pronounced absorption in this spectral region after heating.  相似文献   

Seasonality in surface‐layer net zooplankton communities in Prince William Sound,Alaska     

R. T. Cooney  K. O. Coyle  E. Stockmar  C. Stark 《Fisheries Oceanography》2001,10(Z1):97-109

The upper‐layer net‐zooplankton community in Prince William Sound, Alaska, is characterized by strong seasonality. Abundance and wet‐weight biomass in the upper 50 m drop to fewer than 100 individuals and 10 mg m^?3 in February before rebounding to 5000 individuals and 600 mg m^?3 in June. Copepods dominate in all months, but are augmented by other prominent taxa, particularly pteropods and larvaceans during the late spring, summer and fall. The small copepods Pseudocalanus, Acartia and Oithona are common. Though much less abundant, larger calanoids like Neocalanus, Calanus and Metridia contribute substantially to the biomass in spring and early summer. Meroplankters like barnacle nauplii are also occasionally very abundant. Neocalanus, Calanus and Pseudocalanus all exhibit ontogenetic vertical displacement of populations when stage 5 copepodites (C5) leave the surface in late May and early June for deep water. This seasonality has implications for food‐webs supporting juvenile pink salmon (Oncorhynchus gorbuscha) and Pacific herring (Clupea pallasi) in Prince William Sound.  相似文献   

Correction of intramural ureteral ectopia by ureteral transection and neoureterostomy with the distal ureter left in situ     

NJ Volstad  J Beck  DM Burgess 《Australian veterinary journal》2014,92(3):81-84

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Characterization of 2-methyl-4-amino-5-(2-methyl-3-furylthiomethyl)pyrimidine from thermal degradation of thiamin     

Jhoo JW  Lin MC  Sang S  Cheng X  Zhu N  Stark RE  Ho CT 《Journal of agricultural and food chemistry》2002,50(14):4055-4058

Thiamin hydrochloride was thermally degraded in phosphate buffer (pH 6.5) at 110 degrees C for 2 h. A major decomposition product was isolated by column chromatography and structurally identified by spectrometric techniques ((1)H NMR, (13)C NMR, 2D NMR, and MS) as 2-methyl-4-amino-5-(2-methyl-3-furylthiomethyl)pyrimidine (MAMP). The possible formation pathway of MAMP was studied using two model systems. It is proposed that MAMP is formed by nucleophilic attack of 2-methyl-3-furanthiol on the thiamin.  相似文献   

Glomus globiferum孢子的个体发育研究     

Wu  CG Sylv.  DM 《绵阳农专学报》1994,11(1):63-64

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Observation of Interference Between Two Bose Condensates     

MR Andrews  CG Townsend  H Miesner  DS Durfee  DM Kurn  W Ketterle 《Science (New York, N.Y.)》1997,275(5300):637-641

Interference between two freely expanding Bose-Einstein condensates has been observed. Two condensates separated by approximately 40 micrometers were created by evaporatively cooling sodium atoms in a double-well potential formed by magnetic and optical forces. High-contrast matter-wave interference fringes with a period of approximately 15 micrometers were observed after switching off the potential and letting the condensates expand for 40 milliseconds and overlap. This demonstrates that Bose condensed atoms are "laser-like"; that is, they are coherent and show long-range correlations. These results have direct implications for the atom laser and the Josephson effect for atoms.  相似文献   

Effects of Monomer Structure on Their Organization and Polymerization in a Smectic Liquid Crystal     

CA Guymon  EN Hoggan  NA Clark  TP Rieker  DM Walba  CN Bowman 《Science (New York, N.Y.)》1997,275(5296):57-59

Photopolymerizable diacrylate monomers dissolved in fluid-layer smectic A and smectic C liquid crystal (LC) hosts exhibited significant spatial segregation and orientation that depend strongly on monomer structure. Small, flexible monomers such as 1,6-hexanediol diacrylate (HDDA) oriented parallel to the smectic layers and intercalated, whereas rod-shaped mesogen-like monomers such as 1,4-di-(4-(6-acryloyloxyhexyloxy)benzoyloxy)-2-methylbenzene (C6M) oriented normal to the smectic layers and collected within them. Such spatial segregation caused by the smectic layering dramatically enhanced photopolymerization rates; for HDDA, termination rates were reduced, whereas for C6M, both the termination and propagation rates were increased. These polymerization precursor structures suggest novel materials-design paradigms for gel LCs and nanophase-separated polymer systems.  相似文献   

Role of Gene Interactions in Hybrid Speciation: Evidence from Ancient and Experimental Hybrids   总被引：6，自引：0，他引：6  

LH Rieseberg  B Sinervo  CR Linder  MC Ungerer  DM Arias 《Science (New York, N.Y.)》1996,272(5262):741-745

The origin of a new diploid species by means of hybridization requires the successful merger of differentiated parental species' genomes. To study this process, the genomic composition of three experimentally synthesized hybrid lineages was compared with that of an ancient hybrid species. The genomic composition of the synthesized and ancient hybrids was concordant (rs = 0.68, P < 0.0001), indicating that selection to a large extent governs hybrid species formation. Further, nonrandom rates of introgression and significant associations among unlinked markers in each of the three synthesized hybrid lineages imply that interactions between coadapted parental species' genes constrain the genomic composition of hybrid species.  相似文献   

Measurement of diurnal changes in potato tuber growth     

J. C. Stark  J. L. Halderson 《American Journal of Potato Research》1987,64(5):245-248

A system was developed for continuous,in situ measurement of potato tuber growth. The system consists of a linear variable differential transformer (LVDT) attached to a nylon line which is looped around a developing tuber. Tension is applied to the line so that changes in tuber circumference can be measured with the LVDT and recorded at selected time intervals with a datalogger. Measurements of tubers from potted plants grown in the greenhouse show that tubers follow a diurnal pattern of expansion and contraction. Expansion occurs primarily during the late night and early morning hours when turgor recovery normally occurs.  相似文献   

Response of four potato cultivars to rate and timing of nitrogen fertilizer     

S. L. Love  J. C. Stark  T. Salaiz 《American Journal of Potato Research》2005,82(1):21-30

The release of three new potato (Solarium tuberosum L.) cultivars, Bannock Russet, Gem Russet, and Summit Russet, with unique plant growth characteristics, necessitates the development of appropriate N fertilizer recommendations. These three new cultivars, along with the standard cultivar, Russet Burbank, were treated with four N rates (0, 100, 200, and 300 kg N ha^?1) using two different application timing procedures (“early,” with two-thirds N applied preplant, and “late,” with one-third applied preplant). Measurements included total and U.S. No. 1 yields, petiole NO₃-N concentrations, and net returns derived from economic analysis using a processing-based contract. Each of the four cultivars showed a unique response to N application treatments. Bannock Russet achieved maximum yield and net returns with relatively small amounts of N fertilizer. It also showed no response to N application timing and had moderate NO₃-N sufficiency concentrations early in the season, that decreased markedly late in the season. Gem Russet N requirement for maximum yield was similar to that of Russet Burbank, but required a higher amount of N for maximum net returns. Gem Russet also showed no response to application timing and had NO₃-N sufficiency concentrations similar to or slightly higher than those of Russet Burbank. Summit Russet showed a strong trend for improved N use-efficiency when most of the N was applied early. On the other hand, analysis of net returns revealed a trend for greater profitability for Summit Russet when the majority of N was applied during tuber bulking. Petiole NO₃-N sufficiency concentrations for Summit Russet were generally higher than those for the other three cultivars. In comparison with some earlier studies with Russet Burbank, this research suggested lower optimal N rates and petiole NO₃-N sufficiency concentrations.  相似文献