Influence of furfural concentration on growth and ethanol yield of Saccharomyces kluyveri

Furfural is an important inhibitor in ethanol fermentation process using lignocellulosic hydrolysates as raw materials. In order to find out the furfural concentration range in which furfural inhibits the fermentation process, we used one strain Saccharomyces kluyveri selected from soil and cultured in several different furfural content media under low glucose concentration condition. Experiment results showed that microorganism growth was stimulated and dry cell weight increased when furfural concentration in the medium was 0.25 mg/ml. Furfural had negative effect on cell growth when its concentration was above 1.00 mg/ml. At the same time, the strain growed better and had a higher glucose consumption rate in 5% original glucose concentration condition than in 3% original glucose concentration condition. The results showed that appropriate exaltation of original glucose concentration in stalk hydrolysates will increase the strain resistance to furfural.     

Water Discoloration in Alexandria, Egypt, April 1993. I. Occurrence of Prorocentrum Triestinum Schiffer (Red Tide) Bloom and Associated Physical and Chemical Conditions

A yellow-brown coloration of water developed in the Eastern Harbour of Alexandria (Egypt) during April 1993. the dinoflagellate Prorocentrum triestinum, the causative organism, culminated in a population peak of 71-10⁶ cells 1^-1, chlorophyll a nearly 361 μgl^-1. the bloom occurred with a thermohaline stratified water column and low surface nutrient levels. Water temperature was considered a crucial environmental factor controlling the occurrence of P. triestinum and nitrate was significantly correlated with its counts. the high relative growth constant (3.4 d^-1), calculated just prior to the massive occurrence of the species, explains the rapid development of the bloom. A comparison with the earlier phytoplankton studies in the harbour is made.     

中国“人口流动-经济增长收敛谜题”——基于新古典内生经济增长模型的分析与检验

大规模人口从中西部向东部发达地区流动必将对区域经济产生重要影响。人口流动是否促进区域经济增长,区域经济增长是发散还是收敛对促进区域经济协调发展具有重要的现实意义。本文从人均产出出发,以Barro and Sala-i-Martin国际人口迁移模型为理论基础,用数理分析方法推演出携带人力资本的人口流动新古典内生经济增长收敛机制。在稳态邻域内,发达地区经济增长收敛速度加快,同时欠发达地区经济增长收敛速度减慢,最终导致区域经济相对发散。随后,本文借鉴DR模型建立动态面板数据模型,该模型既能预测内生经济增长发散性,又可以预测新古典经济增长收敛性。通过利用2005—2014年中国29个省份面板数据,采用系统GMM方法对区域经济增长收敛性进行实证检验。实证结果显示:1人口流动促进了区域经济增长;2以2008年为时间节点,西部大开发政策的实施加速了西部地区经济增长;3中国区域经济具有新古典经济增长收敛机制和内生经济增长收敛机制。这意味着理论模型和实证检验相矛盾,从而产生"人口流动-经济增长收敛谜题"。"收敛谜题"产生的原因可能有政策效应、追赶效应、人力资本效应、收入转移效应和干中学效应。"收敛谜题"告诉我们,要使区域经济协调发展,从根本上解决区域差距扩大的矛盾,发挥新古典经济收敛机制和内生经济收敛机制的作用,就必须提高国民整体人力资本水平、解决好就业市场体制问题和流动人口福利待遇问题。     

Measuring and decomposing changes in agricultural productivity, nitrogen use efficiency and cumulative exergy efficiency: Application to OECD agriculture

This paper uses an aggregate quantity space to decompose the temporal changes in nitrogen use efficiency and cumulative exergy use efficiency into changes of Moorsteen-Bjurek (MB) Total Factor Productivity (TFP) changes and changes in the aggregate nitrogen and cumulative exergy contents. Changes in productivity can be broken into technical change and changes in various efficiency measures such as technical efficiency, scale efficiency and residual mix efficiency. Changes in the aggregate nitrogen and cumulative exergy contents can be driven by changes in the quality of inputs and outputs and changes in the mixes of inputs and outputs. Also with cumulative exergy content analysis, changes in the efficiency in input production can increase or decrease the cumulative exergy transformity of agricultural production. The empirical study in 30 member countries of the Organisation for Economic Co-operation Development from 1990 to 2003 yielded some important findings. The production technology progressed but there were reductions in technical efficiency, scale efficiency and residual mix efficiency levels. This result suggests that the production frontier had shifted up but there existed lags in the responses of member countries to the technological change. Given TFP growth, improvements in nutrient use efficiency and cumulative exergy use efficiency were counteracted by reductions in the changes of the aggregate nitrogen contents ratio and aggregate cumulative exergy contents ratio. The empirical results also confirmed that different combinations of inputs and outputs as well as the quality of inputs and outputs could have more influence on the growth of nutrient and cumulative exergy use efficiency than factors that had driven productivity change.     

Detecting Density Dependence in Recovering Seal Populations

Time series of abundance estimates are commonly used for analyses of population trends and possible shifts in growth rate. We investigate if trends in age composition can be used as an alternative to abundance estimates for detection of decelerated population growth. Both methods were tested under two forms of density dependence and different levels of environmental variation in simulated time series of growth in Baltic gray seals. Under logistic growth, decelerating growth could be statistically confirmed after 16 years based on population counts and 14 years based on age composition. When density dependence sets in first at larger population sizes, the age composition method performed dramatically better than population counts, and a decline could be detected after 4 years (versus 10 years). Consequently, age composition analysis provides a complementary method to detect density dependence, particularly in populations where density dependence sets in late.     

曝气时长对中试曝气塘-浮萍塘联合系统中污染物去除的影响

浮萍塘污水处理技术具有管理简便、运行成本低、可资源化回收氮磷污染物等优势。然而,因水体溶解氧(DO)不足造成的污染物去除率低的问题限制了该技术的推广应用。为此,本研究在浮萍塘前端引入曝气塘,构建中试曝气塘-浮萍塘联合系统,借此增加浮萍塘DO含量,并进一步考察了曝气时长(0、0.5、1、2和4 h)对污染物去除效果及浮萍生长的影响,以此探寻低耗高效的最佳曝气时长。结果表明,曝气塘可有效降低水体的浊度,但对氮磷去除的贡献较小,氮磷的去除以浮萍塘为主。曝气处理可显著提高曝气塘及浮萍塘水体DO含量和氧化还原电位(Eh),且DO和Eh随曝气时长的增加而上升。此外,曝气处理还能显著促进浮萍生长及其污染物的去除,但促进效果并未简单地随曝气时长的增加而提高。其中,TN、氨氮和浊度的去除率在曝气时长1 h时已基本达到峰值(去除率分别为58.42%、61.89%和89.90%),TP去除率虽在曝气时长4 h时最大(81.44%),但与曝气时长0.5 h(73.05%)相比并无显著差异;浮萍虽在曝气时长2 h时干基生长速率最高(8.00 g·(m²·d)⁻¹),但与曝气时长0.5 h和1 h(7.35 g·(m²·d)⁻¹左右)相比也无显著差异,而曝气成本却成倍增加。因此,综合考虑污染物去除、浮萍生长及曝气成本,建议曝气时长不宜高于1 h,推荐0.5~1 h为佳。以上结果可为曝气塘-浮萍塘联合系统的应用及曝气时长的选择提供参考。     

Transmission of employment shocks before and after the Oklahoma City tornado

This study examined the economic impact of the May 3, 1999 Oklahoma tornado outbreak on the labor markets of Oklahoma City (OK), Wichita (KS), and Kansas City (MO). In particular, this article examines the transmission of shocks to employment growth across these different labor markets. Using monthly employment data from January 1990 to December 2004, we provide empirical evidence on the cross-market relationships that existed before and after the Oklahoma City tornado. The results suggest that the impact of the wind event may have altered labor market dynamics in Oklahoma City, as well as Wichita and Kansas City.     

农田生态系统中作物—昆虫—杂草的消长与农业环境

通过水旱作物轮换种植，探索与利用作物—昆虫（害虫和益虫）—杂草三大群落的消长与变迁规律，去发展生产，保持农田生态平衡，优化农业生态环境，最大限度地提高作物产量。     

雨生红球藻3个株系的生长及对光盐反应初探

对雨生红球藻3个株系（No.3、No.712和No.797)的生长、对诱导虾青素形成的光盐因子的反应进行了比较,结果表明：No.3、No.712和No.797的生长速率分别为0．128d^-1,0.137d^-1和0.144d^-1;外加盐的量较大（4gL^-1)时导致雨生红球藻细胞数的减少,而外加盐浓度较低（2gL^-1)时,细胞数的反应因株系和光照的不同而有所差异;盐和强光照均导致静细胞比例显著增加;盐的加入仅在弱光照下诱导雨生红球藻3个株系的虾青素累积,在强光照下却导致件株系虾青素含量的下降,强光照下不外加盐时No.3、NO.712和No.797藻液的虾青素含量无显著差异,分别为2.15、2.77和2．45mg L^-1。图1表2参12