东海区海岸带景观格局变化对生态系统服务价值的影响

对大尺度、长时序的海岸带景观格局和生态系统服务价值(ecosystem services value,ESV)的研究,有利于更好地促进区域生态系统保护工作的开展。以1990,1995,2000,2005,2010,2015年6期遥感影像解译结果为基础,对东海区海岸带景观格局变化特征和ESV时空演变进行了分析,并探讨了ESV与景观格局变化二者间的关系。结果表明,1990—2015年的25 a间,受人类活动的影响,东海区海岸带农田和海域面积大量减少,建设用地面积大幅增加;在所研究的5类地貌类型中,除中起伏山地外,其余地貌类型景观面积转移都较为剧烈。25 a间东海区海岸带斑块数量、斑块密度、边界密度、shannon多样性指数等不断增加,景观破碎化、复杂化、多样化增强。农田景观的最大斑块指数、形态指数、边界密度等变化均较大。东海区海岸带ESV呈先增加后减小的趋势,其中森林景观对ESV总量贡献最大;水文调节、生物多样性维持、气候调节、土壤保持、废物处理和气体调节是东海区海岸带主要的生态系统服务功能;在空间上表现出以单位面积中、低ESV为主导的空间分布,高、极高和极低ESV分布较少。研究区ESV总量与农田和海域以及水域和建设用地面积显著相关;与斑块密度、边界密度和形态指数呈显著负相关。同时,食物生产、气体调节、气候调节、土壤保持和生物多样性维持的服务价值与景观指数间均显著相关。     

An electron-diffraction study of the molecular structure of gaseous perbromyl fluoride and calculation of its force field and vibrational amplitudes

The molecular structure of FBrO₃ has been studied by gas-phase electron diffraction. Least-squares refinements of the molecular geometry using fixed spectroscopic amplitudes revealed two geometrical minima. Initially, the amplitudes employed were derived from diagonal force fields obtained by spectroscopic least-squares refinements to fit observed and calculated wave numbers; for each geometry there are two spectroscopic minima. In the lowest geometrical minimum the wave number agreement is poor, however, the introduction of the ∠OBrO/∠FBrO interaction force constant removed the discrepancies; the resulting force field is F(Br-O) = 6.92 ± 0.02 mdyn Å^?1F(Br-F) = 3.22 ± 0.03 mdyn Å^?1, F(∠OBrO) = 1.06 ± 0.02 mdyn Å, F(∠FBrO) = 0.81 ± 0.03 mdyn Å, F(∠OBrO/∠FBrO) = ?0.19 ± 0.02 mdyn Å. In the corresponding geometrical minimum r_g(Br-O) = 1.582 ± 0.001 Å, r_g(Br-F) = 1.708 ± 0.003 Å, r_α(∠OBrO) = 114.9 ± 0.3°, r_α(∠FBrO) = 103.3 ± 0.3°. Perpendicular amplitude correction coefficients, calculated for each force field employed, were used throughout to relate the interatomic distances through the r_α-structure. The geometries of the r_α^o- and r_e-structures are estimated.     

A Conversation with William A. Fowler – Part I

Nobel laureate William A. Fowler recalls his early education in physics; his part in the history of nuclear physics at the California Institute of Technology in the 1930s; parallel efforts elsewhere, particularly at Berkeley and the Department of Terrestrial Magnetism in Washington,D.C.; his contacts with J. Robert Oppenheimer; and his work with Charles C. Lauritsen and Tommy Lauritsen before and after World War II.John Greenberg received his Ph.D. degree from the University of Wisconsin and was Caltech research fellow in history from 1980–1984. The Editors were saddened to learn that he died while this interview was in press. Requests for reprints may be directed to Judith R. Goodstein, Institute Archives 015A-74, Caltech, Pasadena, CA 91125 USA; e-mail: jrg@caltech.edu.     

Asymptotic analysis of Emden–Fowler type equation with an application to power flow models

Emden–Fowler type equations are nonlinear differential equations that appear in many fields such as mathematical physics, astrophysics and chemistry. In this paper, we perform an asymptotic analysis of a specific Emden–Fowler type equation that emerges in a queuing theory context as an approximation of voltages under a well-known power flow model. Thus, we place Emden–Fowler type equations in the context of electrical engineering. We derive properties of the continuous solution of this specific Emden–Fowler type equation and study the asymptotic behavior of its discrete analog. We conclude that the discrete analog has the same asymptotic behavior as the classical continuous Emden–Fowler type equation that we consider.     

Nonlinear dynamics of the heartbeat: I. The AV junction: Passive conduit or active oscillator?

Under physiologic conditions, the AV junction is traditionally regarded as a passive conduit for the conduction of impulses from the atria to the ventricles. An alternative view, namely that subsidiary pacemakers play an active role in normal electrophysiologic dynamics during sinus rhythm, has been suggested based on nonlinear models of cardiac oscillators. A central problem has been the development of a simple but explicit mathematical model for coupled nonlinear oscillators relevant both to stable and perturbed cardiac dynamics. We use equations describing an analog electrical circuit with an external d.c. voltage source (V₀) and two nonlinear oscillators with intrinsic frequencies in the ratio of 3:2, comparable to the SA node and AV junction rates. The oscillators are coupled by means of a resistor. 1:1 (SA:AV) phase-locking of the oscillators occurs over a critical range of V₀. Externally driving the SA oscillator at increasing rates results in 3:2 AV Wenckebach periodicity and a 2:1 AV block. These findings appear with no assumptions about conduction time or refractoriness. This dynamical model is consistent with the new interpretation that normal sinus rhythm may represent 1:1 coupling of two or more active nonlinear oscillators and also accounts for the appearance of an AV block with critical changes in a single parameter such as the pacing rate.     

Cloud and aerosol contributions to variation in shortwave surface irradiance over East Asia in July during 2001 and 2007

It is important to clarify the contributions of clouds and aerosols to the variation of surface shortwave irradiance (S) for climatological studies. This study examined the contributions of clouds and aerosols to the variation in S over East Asia (75-135°E, 20-55°N) in July during 2001 and 2007 using the index of potential radiative forcing (PRF) to characterize the temporal and geographical variations. After confirming the validity of PRF for multiyear analyses, we performed several temporal analyses of clouds and aerosols over the whole research domain. Changes in the geographical distribution, contribution histograms, and averaged values were studied. In agreement with previous studies that treated single-year cases, we confirmed that the magnitudes of the temporal changes in S variations due to clouds and aerosols were highly variable geographically. As for domain-averaged S variations, we did not observe defined trends for the research period. It was also found that the temporal variation between one parameter and its S variation was negatively correlated, from the point analyses at two locations. Based on these results, we concluded that PRF is a promising tool for research into long-term S variations. This kind of information will be quite valuable as basic data for use in climate modeling.     

A PRELIMINARY RESEARCH ON WEATHERING PROCESS IN CASEY STATION, EAST ANTARCTIC

The chief aim of this preliminary work is to investigate the weathering process of the bed rock and moraine in Antarctic by the method of sedimentology. Microfractures, the depth of which is less than 1 cm, and macrofissures are formed through frost weathering process. The chemical composition of the weathering products are observably related to their size due to migration process. Weathering materials are relatively rich in rare-earth elements of Ce family. Weathering clay minerals are mainly illite hydromica which can considerably absorb the elements of Ti, K, Cs, Rb, Sc, Sb, As and Fe. The weathering crust of the bed rock has hardly any CaCO_3 component, it belongs to primigenial debris weathering crust, with only a slight As pollution.     

The crystal structure of a tricarbonyliron-substituted cyclobutadiene complex: Tricarbonyl[1,2,2a,12a-η-5,10-dimethyldibenzo[a,c]cyclobuta[f]cyclooctene-3,12-dione] iron

The crystal structure of tricarbonyl[1,2,2a,12a-η-5,10-dimethyldibenzo[a,c] cyclobuta[f] cyclooctene-3,12-dione] iron, C₂₀O₂H₁₄Fe(CO)₃, has been determined by the single crystal X-ray diffraction technique using data collected with a fully automated diffractometer. The unit cell is monoclinic, space group P2₁/c with a = 12.025(2), b = 23.204(3), c = 14.614(2) Å, β = 102.16(2)°, and contains eight molecules (two per asymmetric unit). The structure was elucidated to study the coordination of the iron atom and to correlate the conformation of the eight-membered ring with an NMR study. The final structure was obtained by Patterson-superposition and Fourier techniques and refined by full-matrix least-squares to a crystallographic residual of 0.070. In both independent molecules the iron atom is 1.77 Å from the cyclobutadiene ring to which it is coordinated. The eight-membered ring is flattened from a boat conformation and the six-membered rings are twisted from coplanarity by an angle of 74°. The twist is such that if one ring points above the eight-membered ring, the other ring will point below it with concomitant pointing in the opposite sense by neighboring carbonyl groups. Such a structure has conformational chirality. It is postulated that the stability of each enantiometer is due to the particularly high energy of the transition state through which each would pass to achieve inter-conversion.     

Determination of Cd,Pb, and Cu in the Atmospheric Aerosol of Central East Antarctica at Dome C (Concordia Station)

Trace heavy metals Cd, Pb, and Cu were determined (by square wave anodic stripping voltammetry) in aerosol samples collected at Dome C (the Italo-French Station Concordia), a remote site of the Central East Antarctic plateau, for which no data are available until now. During the Austral Summer 2005–2006, three PM10 high-volume impactors were installed in two locations nearby of Concordia station: the first one very close and downwind of the station (about 50 m north), the other two (very close to each other) in a ‘distant’ site, upwind of the station and close to the astrophysics tent (not used in that expedition) at ~800 m south of Station Concordia. For each sample, the availability of the mass of the aerosol collected (obtained by differential weighing carried out on site), in addition to the volume of the filtered air, allowed us to express results both in terms of metal mass fractions in the aerosol and in the usual way of metal atmospheric concentrations. Metal contents increased in the order Cd < Pb < Cu with the following ranges of values: Cd 1.0–8.4 µg g⁻¹ (0.09–3.1 pg m⁻³), Pb 96–470 µg g⁻¹ (12–62 pg m⁻³), and Cu 0.17–20 mg g⁻¹ (0.027–2.4 ng m⁻³). From the metal temporal profiles obtained we estimated the following background values for the area of Dome C, expressed both in mass fractions and in atmospheric concentrations: Cd 1.2 ± 0.2 µg g⁻¹ (0.24 ± 0.13 pg m⁻³), Pb (here fixed as upper limit) 113 ± 13 µg g⁻¹ (21 ± 8 pg m⁻³), and Cu 0.91 ± 0.48 mg g⁻¹ (0.12 ± 0.07 ng m⁻³). The highest values were observed in the first part of the season, and particularly for the site close to the station, possibly related to sample contamination linked to intense activity at the Concordia station connected with the beginning of the expedition, including aircraft arrivals/departures. Increments of up to 10 times (and even 20 times for Cu) were recorded with respect to the background values. The metal excesses of the contaminated over background samples were found approximately, except for Cu, in the same proportion of the metal contents of the special Antarctic blend (SAB) diesel fuel, which is used almost exclusively at Concordia Station. The effect of the wind direction was also observed. Thus in the intermediate period of the campaign, when the wind direction reversed for several days with respect to the prevailing one, Cd and Pb metal contents decreased at the sampling point installed close to the station, now upwind of Concordia station, and increased at the ‘clean’ site astrophysics tent, turned downwind at the main station. No simple and easily interpretable effect of the wind direction was observed for Cu, which suggests that some other extemporaneous and not clearly identified factor may have intervened in this case. These results suggest that the human impact at Dome C influences mainly the zone very close to the station, but also the area in the neighborhood, including the supposed clean site of the astrophysics tent (about 800 m far from the station), when the wind direction reverses with respect to the prevailing one, leaving the site downwind of the station Concordia. Since no other data are reported for the Dome C area, our results are compared with literature data referred to the South Pole Station (the only other plateau site for which data are available) and several other coastal Antarctic sites, observing that our results (excluding Cu) are the lowest ever observed for Antarctic aerosol.     

Our expedition in the construction of fluorescent supramolecular metallacycles

During the past few years, the construction of fluorescent supramolecular metallocycles has attracted extensive attention due to their diverse applications such as sensing, photoelectric devices, and mimicking complicated natural photo-processes. In this review, we will discuss how we entered the field of fluorescent supramolecular metallacycles and what we investigated in this field. The preparation of various fluorescent supramolecular metallacycles and their applications in monitoring the dynamics of coordination-driven self-assembly, sensing, catalysts, and supramolecular gels will be summarized.