Variations in spruce (Picea sp.) distribution in the Chinese Loess Plateau and surrounding areas during the Holocene

&nbsp;&nbsp;&nbsp; Based on published pollen data from 44 sites in the Loess Plateau and surrounding areas, we recalculate values of Picea abundance digitized from the original diagrams and construct six isopoll maps to reconstruct the distribution of spruce forest at 2000 yr intervals during the Holocene. Spruce forest gradually expanded from about 10 ka BP ago and reached its peak distribution around 8 ka BP. It retained its maximum extent between 8 ka BP and 6 ka BP, broadly covering the subalpine area and stretching to the valleys of the western Loess Plateau with high densities and even reaching the edges of the adjacent desert regions. After 6 ka BP, spruce forest began to retreat to higher elevations. This trend was accelerated after 4 ka BP. After 2 ka BP, it disappeared completely from the Loess Plateau and most of its surrounding areas. Precipitation strongly dominated by the Asian summer monsoon was the primary controlling factor in the distribution of spruce before 2 ka BP. After about 2 ka BP, the increasing intensity of human activity became the primary factor in the disappearance of spruce in the Loess Plateau, resulting in an enormous impact on the present landscape.</h3

TWITTER IN THE MARKETING

We report on a compact and highly efficient diode-end-pumped TEM00 Nd:YVO4 slab laser with an output power of 103 W and beam quality M2 1.5. The optical-to-optical efficiency was 41.5%. In electro-optically Q-switched operation. 83 W of average power at a pulse-repetition rate of 50 kHz with a pulse length of 11.3 ns was obtained. At a pulse-repetition rate of 10 kHz, 5.6 mJ of pulse energy, and 870 kW of peak power were measured

Elasticity solutions for a transversely isotropic functionally graded circular plate subject to an axisymmetric transverse load qrk

AbstractThis paper considers the bending of transversely isotropic circular plates with elastic compliance coefficients being arbitrary functions of the thickness coordinate, subject to a transverse load in the form of qrk (k is zero or a finite even number). The differential equations satisfied by stress functions for the particular problem are derived. An elaborate analysis procedure is then presented to derive these stress functions, from which the analytical expressions for the axial force, bending moment and displacements are obtained through integration. The method is then applied to the problem of transversely isotropic functionally graded circular plate subject to a uniform load, illustrating the procedure to determine the integral constants from the boundary conditions. Analytical elasticity solutions are presented for simply-supported and clamped plates, and, when degenerated, they coincide with the available solutions for an isotropic homogenous plate. Two numerical examples are finally presented to show the effect of material inhomogeneity on the elastic field in FGM plates

Correlation of mechanical factors and gallbladder pain

Acalculous biliary pain occurs in patients with no gallstones, but is similar to that experienced by patients with gallstones. Surgical removal of the gallbladder (GB) in these patients is only successful in providing relief of symptoms to about half of those operated on, so a reliable pain-prediction model is needed. In this paper, a mechanical model is developed for the human biliary system during the emptying phase, based on a clinical test in which GB volume changes are measured in response to a standard stimulus and a recorded pain profile. The model can describe the bile emptying behaviour, the flow resistance in the biliary ducts, the peak total stress, including the passive and active stresses experienced by the GB during emptying. This model is used to explore the potential link between GB pain and mechanical factors. It is found that the peak total normal stress may be used as an effective pain indicator for GB pain. When this model is applied to clinical data of volume changes due to Cholecystokinin stimulation and pain from 37 patients, it shows a promising success rate of 88.2% in positive pain prediction

Novel modular switched reluctance machines for performance improvement

Compared to non-modular machines, modular topologies become increasingly attractive due to their simplified manufacture process, better fault tolerant capability and potentially reduced material consumption. In order to maintain or even enhance the machine performance while achieving high fault tolerant capability, novel modular, single layer winding switched reluctance machines (SRMs) with different pole numbers are proposed, which are supplied by rectangular wave current with different conduction angles. The influences of the pole number and flux gap width between E-core segmented stators on the electromagnetic performance have been investigated in terms of self- and mutual inductances, electromagnetic torque, copper loss, iron loss, and radial force. It has been found that the modular structures with higher rotor pole numbers than stator slot numbers (12-slot/14-pole and 12-slot/16-pole SRMs) can maintain and even improve the average torque due to the nature of self- and mutual inductances. In addition, the torque ripple for modular machines are significantly reduced (below 50%), so do the iron loss and radial force, leading to higher efficiency albeit with potentially lower vibration and acoustic noise. Two prototypes with 12-slot/8-pole and 12-slot/14-pole combinations have been built with both non-modular and modular structures to validate the predictions in terms of inductances and static torques

Diffuse export of nutrients under different land uses in the irrigation area of lower Beiyunhe River (China)

AbstractNon-point source pollution is serious in the agriculture watershed of China. Understanding the characteristics of rainfall-runoff from agriculture watershed can provide theoretical support for controlling non-point source pollution. In this study, we investigated runoff characteristics of eight indices (dissolved total N, NO3--N, NH4+-N, total phosphorus, dissolved total phosphorus, particulate phosphorus, total organic carbon, COD) from three types of land uses, including farmland, forest and village in the downstream irrigation area of the Beiyunhe River basin. The results showed that the event mean concentrations (EMCs) of total dissolved N in village, farmland and forestland were 17.81mg/L, 12.68mg/L and 3.14mg/L, respectively. EMC of total phosphorus in the order: farmland (0.44mg/L) > village (0.22mg/L) > forestland (0.17mg/L). EMC of COD in the order: farmland (45.07mg/L) > forestland (27.06mg/L) > village (18.03mg/L). The changes in the nutrients concentrations of the runoff water over a rainfall event indicated that the transports of the nutrients are similar among various land use types. The instantaneous concentrations of TN, NH4+-N, and NO3--N were high in the initial period of runoff, tend to decreasing with rainfall continuing, and increase in later period. Phosphorus concentration with time variation was not obvious among three land use types. The phosphorus species with high proportion in the total phosphorus was particle P (accounting for 75%) in forestland, dissolve P (79%) in farmland, and particle P (48%) and dissolve P (52%) in village. The curves of COD and TOC had been shown as high in the initial period of runoff, tending to increasing with rainfall continuing, and decrease in the later period. First-flush of all the indices were obvious in all three land use types with the rank of village > forestland > farmland. In village, all of the pollutions have taken place the phenomenon of first flush, while in farmland, pollutions tended to uniformly distribute or dilution throughout the storm event

Evaluación comparativa de la composición química y las actividades antimicrobianas de los aceites esenciales extraídos de diferentes quimiotipos de Cinnamomum camphora (L.) Presl

The purpose of this study is to determine the chemical composition of the essential oils of&nbsp;Cinnamomum camphora&nbsp;(L.) Presl leaves (CCPL) from 5 different habitats in China by GC-MS, and to evaluate their antimicrobial activities against 3 foodborne pathogens, using a paper disc diffusion method. A total of 30 compounds were identified with a predominance of oxygenated monoterpenes, including linalool (42.65%-96.47%), eucalyptol (39.07%-55.35%) and camphor (26.08%) as well as monoterpene hydrocarbons such as sabinene (6.18%-12.93%) and α-terpineol (8.19%-13.81%). Through cluster analysis, CCPL from 5 different habitats can be well divided into 2 categories. Combining with principal component analysis, the habitats can be better correlated with the chemical constituents of the essential oils. The antimicrobial activities of 5 extracted essential oils against 2 gram-negative bacteria and one gram-positive bacteria were assessed. It showed that the essential oil extracted from the CCPL harvested in Jinxi had the strongest antibacterial property. The results of this study provided basis for resource identification of CCPL and quality difference identification of essential oils. Research on the antibacterial properties of several pathogenic strains has proved its application value as a natural food preservative.El objetivo de este estudio es determinar la composición química de los aceites esenciales de hojas de&nbsp;Cinnamomum camphora&nbsp;(L.) Presl (CCPL) de 5 hábitats diferentes de China mediante GC-MS, y evaluar sus actividades antimicrobianas contra 3 patógenos transmitidos por los alimentos, utilizando un método de difusión de disco de papel. Se identificaron un total de 30 compuestos, con predominio de monoterpenos oxigenados, entre ellos linalol (42,65%-96,47%), eucaliptol (39,07%-55,35%) y alcanfor (26,08%) así como hidrocarburos monoterpenos como el sabineno (6,18%-12,93%) y α-terpineol (8,19%-13,81%). A través del análisis de conglomerados, los CCPL de 5 hábitats diferentes se pueden dividir bien en 2 categorías. En combinación con el análisis de componentes principales, los hábitats se pueden correlacionar mejor con los componentes químicos de los aceites esenciales. Se evaluaron las actividades antimicrobianas de 5 aceites esenciales extraídos contra 2 bacterias gramnegativas y una bacteria grampositiva. Se demuestra que el aceite esencial extraído del CCPL cosechado en Jinxi tenía la propiedad antibacteriana más fuerte. Los resultados de este estudio proporcionaron la base para la identificación de recursos de CCPL y la identificación de diferencias de calidad de los aceites esenciales. La investigación sobre las propiedades antibacterianas de varias cepas patógenas ha demostrado su valor de aplicación como conservante natural de alimentos

Understanding of hydrogel network formation and its application in the architecture of significantly enhanced hydrogel

An understanding of the physical hydrogel network formation has been obtained by dynamic rheological experiments. The evidence shows that the network formation turns out to be a nucleation-controlled process. It was found that there exists a critical temperature Tc; fiber branching is greatly enhanced when the network formation is performed in the regime of T&lt;Tc (T, the final setting temperature). This finding enables the authors to build significantly enhanced gel networks. So far G&prime; (elastic modulus) of the hydrogel network has been enhanced by 187% while the formation period can be greatly shortened to only 1/20 of the previous process.<br /