Time series analyses of biological and environmental variables for Suisun Bay and the Sacramento and San Joaquin rivers

EXTRACT (SEE PDF FOR FULL ABSTRACT): Arima analysis was used to compute cross-correlations between principal component axes that described environmental variables, chlorophyll concentration and zooplankton density for the Sacramento and San Joaquin rivers and Suisun Bay. ... Cross-correlations among the time series may provide information about links between environmental and biological variables within the estuary and the possible influence of climate.

Influence of climate on environmental factors associated with long-term changes in chlorophyll production for the Sacramento-San Joaquin delta and Suisun Bay, California

Long-term changes in chlorophyll production were predicted from environmental variables for the Sacramento and San Joaquin rivers and Suisun Bay using Box-Jenkins transfer function models. Data used for the analyses were collected semimonthly or monthly between 1971 and 1987. Transfer function models developed to describe changes in chlorophyll production over time as a function of environmental variables were characterized by lagged responses and described between 39 and 51 percent of the data variation. Significant correlations between environmental variables and the California climate index (CA SLP) were used to develop a conceptual model of the link between regional climate and estuarine production.

Late Holocene environmental variability in the upper San Francisco Estuary as reconstructed from tidal marsh sediments

EXTRACT (SEE PDF FOR FULL ABSTRACT): Tidal marsh sediments collected from Browns Island in the lower Sacramento/San Joaquin Delta, California, are used to reconstruct environmental variability over the past 6.8 ka. Calibrated radiocarbon dates provide chronostratigraphic control. Trace metal analyses, grain-size variability, organic content, and macrofossils are used to define short- and long-term variations in relative salinity and inundation frequency. Aggradation began in subtidal fresh water conditions about 6.8 ka. Subtidal aggradation of clayey silts continued until about 6.3 ka, when conditions shifted toward a lower intertidal brackish marsh environment. By 5.1 ka, a brackish marsh plain had evolved, with surface water freshening after 4.1 ka. Conditions returned to brackish similar to the present after 2.3 ka.

Physical, chemical, and biological characterization of water year types in the San Francisco Bay estuary [abstract]

EXTRACT (SEE PDF FOR FULL ABSTRACT): Twenty-three years of physical, chemical, and biological data were used to characterize conditions associated with wet, normal, dry, and critical water year types in the upper San Francisco Bay estuary.

The influence of climate on phytoplankton communities in the upper San Francisco estuary

EXTRACT (SEE PDF FOR FULL ABSTRACT): The 1977 climate shift was characterized by low chlorophyll a concentrations and a shift in phytoplankton community composition throughout the upper San Francisco Bay estuary. ... For climate to be a driving force in phytoplankton communities, it must affect mechanisms that control biomass and community composition. The influence of climate on environmental conditions and phytoplankton community composition among water-year types was examined using 19 years of physical, chemical, and phytoplankton data collected monthly at 15 stations throughout the estuary.

Lista de peces de la provincia de San Luis.

Esta serie tiene como finalidad dar a conocer las especies presentes en los diferentes estados provinciales. Tomando como base los trabajos de López et al. (2003), Reis et al. (2003), y Liotta (2006), mencionamos para cada territorio los cambios y novedades posteriores a estas publicaciones. Consideramos que este modesto aporte contribuirá a precisar el conocimiento ictiofaunístico regional, ya que, además de las listas de especies, adjuntamos bibliografía de referencia y el marco biogeográfico e hídrico correspondientes, que podrán ser de utilidad para quienes hagan uso de este trabajo. Por otra parte entendemos que la participación de autores involucrados en la región considerada, le da un verdadero sentido federal a esta contribución, además de reforzar vínculos en los protagonistas de nuestra especialidad. En este nuevo número presentamos la provincia de San Luis que se encuentra limitada al norte por San Juan y La Rioja, al este por Córdoba, al oeste por Mendoza y al sur por la provincia de La Pampa. Si bien las especies potencialmente pueden ampliar su rango de distribución, ante cambios climáticos y/o modificaciones de cuencas, es importante considerar para futuros análisis, la acción generada por la antropocoria. Esta, muchas veces realizada de forma involuntaria por los propios pescadores, y en otras ocasiones, bajo responsabilidad de los organismos del estado han desvirtuado la distribución natural de varias especies, afectando tanto estudios zoogeográficos como las medidas dirigidas a la conservación y manejo de los recursos. A las 16 especies citadas por Liotta 2006 para la provincia debemos agregar nuevas citas de especies introducidas (Tabla I y II). Además consideramos que tanto Trichomycterus tenuis como Jenynsia obscura requieren ser confirmadas para la provincia ya que sólo se cuenta con un registro (Tabla III).

聚（ε-已内酯）（PCL）/苯乙烯-丙烯腈共聚物（SAN）共混物的研究

本工作采用DSC方法、红外光谱方法、光学显微镜方法、小角激光光散射方法及X射线衍射和散射方法研究了聚（ε-已内酯）（PCL）/苯乙烯-丙烯腈共聚物（SAN）共混物的相容性、熔融行为、结晶过程及结晶形态。观察到PCL/SAN共混物在0～30%wt PCL组成范围内，表现出单一的玻璃化转变，这个转变界于两个纯组合的玻璃化转变之间。在红外光谱上观察到PCL的羰基峰随着SAN的混入移向低频率。说明PCL分子与SAN分子之间存在着特殊的相互作用。从熔点下降计算的相互作用参数结果表明，PCL/SAN共混物在热力学上是相容的。共混物中PCL的熔点下降表明SAN分子对于PCL熔融行为是有影响的，同时不同的退火条件对于PCL/SAN共混物的PCL熔点也是有影响的，退火温度越高相应的PCL熔点越高。在PPCL/SAN共混物体中，PCL的球晶生长速率类似于均聚物，并且随着SAN含量的增加球晶生长速率下降，说明SAN分子阻碍了PCL分子链段的迁移，并且可以从理论上模拟共物混物中PCL的线性生长速率。在结晶性的PCL/SAN共混物中，PCL是以球晶形式存在的，在不同的结晶条件下，产生不同的球晶形态。在慢速降温结晶条件，SAN的加入促使PCL片晶发生扭曲形成环状球晶，通过光学显微镜方法和光散射方法计算出扭曲周期，结果表明扭曲周期随着SAN含量的增加而减少，同时也表明球晶半径随着SAN含量的增加而减小。在等温结晶条件下，SAN的加入，使得PCL的球晶半径减小。X射线衍射结果表明SAN分子并不存在PCL晶体中，而小角X射线散射结果表明在共混物中，随着SAN含量的增加，PCL片晶中心之间距离（长周期）逐渐增加，而且片晶与无定形片层的界面是分明的。指出无定形相是存在在PCL的片晶之间。

PMMA/SAN共混物薄膜表面相分离动力学的原位AFM研究

本论文主要借助原子力显微镜（AFM）、X-射线光电子能谱（XPS）等实验手段，纳米尺度上在线原位地研究了高温临界组成PMMMA/SAN（50／50，w／w）共混薄膜体系，分析并探讨了此共混薄膜表面相分离及其超薄膜体系的润湿／去润湿和相分离行为。首先，从敲击式AFM中相位图的成像原理出发，建立了一个高温下用原位AFM定性鉴别不同聚合物的纳米尺寸微区的方法，即：先在基底（硅）上铺展一层非常平坦的单一组分（SAN）薄膜，再在此千膜上，通过旋涂由选择性溶剂（冰醋酸）配制的另一组分（PMMA）的极稀溶液，使之不能形成一层连续的完整膜，最后在高温（175℃）下用敲击模式的原子力显微镜（TM-AFM）检测相位图随退火时间的变化。得到在175℃的相位图中，PMMA富相比SAN的富相显得更暗，这为后续工作提供了定性鉴别相区的方法。其次，高温下用原位AFM研究了PMMA/SAN薄膜表面相分离过程，在线观察了相分离的归并过程，定量地得到了临界相分离温度，并给出了特征波矢对时间依赖关系的标度指数，划分了相分离动力学演变的不同阶段。对于膜厚约为130nm的体系，表面相分离的临界温度大约为165℃，其表面相分离的特征波矢与时间的标度关系q+（t）-t-n，在整个实验时间内，随时间的演变过程中，显示了两个不同的指数变化区，即前期很慢的n=0.13和后期的n＝1／3。0.13的指数关系可能是由于表面聚合物链的几何受限及表面富集相把部分新生成的另一相覆盖所致，1／3的指数关系可以认为是由普遍的Brownian扩散所致。而对于膜厚为50曲的此组成共混薄膜，得到的标度关系与C汕n线性理论吻合得非常好的Spinodal Deposition（SD）表面相分离的初期，即n＝0，这是由于降低膜厚 增加了共混物的相容性，提高了临界温度，从而减缓了相分离过程，使得在我 们观测的时间范围内更易观察到表面相分离的初期。再次，用阶梯式降温的好M和XPS，发现了PMMA/SAN体系原位和离位实验结果存在巨大差别的主要原因之一—润湿温度的存在。对PMMA/SAN（50／50，w／w，-130nm）共混薄膜体系，原位AFM的退火和准淬火实验表明， 虽然在高温和室温、真空和常态、原位和离位，相分离的聚合物共混薄膜表面 形貌变化不大，但是表面物理性质却有很大的区别。原位XPS实验表明，未经 任何处理的样品在185℃退火时，很快在离表面很薄的下面形成一层PMMA含 量远低于本体值的薄层，之后最表面的PMMA也往本体迁移，直至表面SAN 的含量远高于它的本体值。对已在175℃退火20hr的此样品，逐渐降温退火过 程的原位XPS表明，当退火温度降至145oC时，样品表面几乎完全被PMMA覆盖，很好地验证了Conlposto等提出的润湿温度的假设，即对此体系，润湿温 度是原位和离位存在巨大的差异的主要因素之一，这与原位AFM的实验结果也，存在很好的一致性。最后，高温下原位观察了硅基底上PMMA/SAN超薄膜（膜厚-Rg）的去润湿、相分离过程和PMMA在基底上的润湿过程，以及云母基底上的该体系高温下的稳定润湿行为。以硅为基底的PMM刀sAN共混超薄膜在155”c下发生了类 似sPinodal dewetting的去润湿，其原因可能是在垂直于基底的浓度梯度引起的表面组成的涨落，对这种去润湿的动力学还进行了探讨。以硅为基底的PMMA/SAN共混超薄膜在175℃下不仅发生了类似spinodal dewetting的去润 湿，而且还发生了去润湿液滴内部的相分离以及相分离析出的PMMA润湿硅基底的过程，提出了一个简单的模型描述了这种复杂的过程。此外，还研究了不同基底对此共混超薄膜体系的润湿行为进行了研究，以云母为基底的此共混体系在175℃下长时间内是稳定的，其原因可能是云母与PMMA和SAN均有很强的作用力，足于补偿聚合物链在构象嫡上的损失。

the ebb-tidal delta of the venice lagoon,Italy

Very high-resolution seismic lines were collected offshore the Venice Lagoon in the framework of the Co.Ri.La'New very high resolution seismic methods to study the Venice Lagoon subsoil' project. The 140 km boomer profiles led to the identification of a convex-upward,lens-shaped body just outside the Lido inlet,one of the three lagoon inlets,which has been interpreted as an ebb-tidal delta.The comparison between the scismostratigraphic setting og this deposit, as revealed by the seismic lines,and the analyses of historicalbathymetric maps highlighted the key role of human interventions in the formation and evolution of the Lido inlet cbb-tidal delta.To preserve the lagoon environment but also to ensure a navigable way, human interventions at the Lidoinlet,performed since the fourteenth centtury, caused profound variations in the inlet dynamics,ldading to a progressive increase in the sediment dispersion from the lagoon interior towards the sea. The ebb-tidal delta of the Lido nilet is thus a very recent feature compared with the formation of the Venice lagoon and formed mainly as a consequence of the construction of the two jetties that have bound the inlet form AD 1886 to the present day.

Surface phase separations of PMMA/SAN blends investigated by atomic force microscopy

The thin films of poly(methyl methacrylate) (PMMA), poly(styrene-co-acrylonitrile) (SAN) and their blends were prepared by means of spin-coating their corresponding solutions onto silicon wafers, followed by being annealed at different temperatures. The surface phase separations of PMMA/SAN blends were characterized by virtue of atomic force microscopy (AFM). By comparing the tapping mode AFM (TM-AFM) phase images of the pure components and their blends, surface phase separation mechanisms of the blends could be identified as the nucleation and growth mechanism or the spinodal decomposition mechanism. Therefore, the phase diagram of the PMMA/SAN system could be obtained by means of TM-AFM. Contact mode AFM was also used to study the surface morphologies of all the samples and the phase separations of the blends occurred by the spinodal decomposition mechanism could be ascertained. Moreover, X-ray photoelectron spectroscopy was used to characterize the chemical compositions on the surfaces of the samples and the miscibility principle of the PMMA/SAN system was discussed.

ABS树脂合成中影响PB-g-SAN接枝共聚物接枝率的因素

采用种子乳液聚合方式 ,以 K2 S2 O8为引发剂引发聚合 ,合成了一系列 PB- g- SAN接枝共聚物。考察了引发剂用量、分子量调节剂 (TDDM)用量和橡胶 (PB)含量对 PB- g- SAN接枝共聚物接枝率的影响。并将 K2 S2 O8引发剂与氧化 -还原引发体系做了比较。结果表明 ,随着引发剂 K2 S2 O8用量逐渐增加 ,PB- g- SAN接枝共聚物的接枝率逐渐降低。引发剂用量太少时 ,不能满足聚合要求 ,PB- g- SAN接枝共聚物的接枝率也会降低。随着分子量调节剂 (TDDM)用量的增加 ,PB- g- SAN接枝共聚物的接枝率逐渐降低。随胶含量的增加 ,PB- g- SAN接枝共聚物的接枝率逐渐降低。采用氧化 -还原引发体系引发聚合有利于接枝反应的进行 ,在 PB含量相同时 ,采用氧化 -还原引发体系合成的 PB- g- SAN接枝共聚物的接枝率比采用 K2 S2 O8合成的接枝共聚物接枝率高。