Proactive Countermeasures Research Articles

Increased Frequency of Pink Bollworm Resistance to Bt Toxin Cry1Ac in China

Transgenic crops producing insecticidal proteins from Bacillus thuringiensis (Bt) kill some key insect pests, but evolution of resistance by pests can reduce their efficacy. The main approach for delaying pest adaptation to Bt crops uses non-Bt host plants as “refuges” to increase survival of susceptible pests. To delay evolution of pest resistance to transgenic cotton producing Bt toxin Cry1Ac, the United States and some other countries have required refuges of non-Bt cotton, while farmers in China have relied on “natural” refuges of non-Bt host plants other than cotton. The “natural” refuge strategy focuses on cotton bollworm (Helicoverpa armigera), the primary target of Bt cotton in China that attacks many crops, but it does not apply to another major pest, pink bollworm (Pectinophora gossypiella), which feeds almost entirely on cotton in China. Here we report data showing field-evolved resistance to Cry1Ac by pink bollworm in the Yangtze River Valley of China. Laboratory bioassay data from 51 field-derived strains show that the susceptibility to Cry1Ac was significantly lower during 2008 to 2010 than 2005 to 2007. The percentage of field populations yielding one or more survivors at a diagnostic concentration of Cry1Ac increased from 0% in 2005–2007 to 56% in 2008–2010. However, the median survival at the diagnostic concentration was only 1.6% from 2008 to 2010 and failure of Bt cotton to control pink bollworm has not been reported in China. The early detection of resistance reported here may promote proactive countermeasures, such as a switch to transgenic cotton producing toxins distinct from Cry1A toxins, increased planting of non-Bt cotton, and integration of other management tactics together with Bt cotton.

Immigration Policy and Counterterrorism

A terrorist group, based in a developing (host) country, draws unskilled and skilled labor from the productive sector to conduct attacks in that nation and abroad. The host nation chooses proactive countermeasures. Moreover, a targeted developed nation decides its optimal mix of immigration quotas and defensive counterterrorism actions. Even though proactive measures in the host country may not curb terrorism directed at it, it may still be advantageous in terms of national income. Increases in the unskilled immigration quota augment terrorism against the developed country. By contrast, increases in the skilled immigration quota can reduce terrorism in the developed country if skilled migrants have a small marginal impact on terrorism there. When the developed country assumes a leadership role, it strategically should reduce its skilled immigration quota to induce more proactive measures in the host developing country.

Early warning of cotton bollworm resistance associated with intensive planting of Bt cotton in China.

Transgenic crops producing Bacillus thuringiensis (Bt) toxins kill some key insect pests, but evolution of resistance by pests can reduce their efficacy. The predominant strategy for delaying pest resistance to Bt crops requires refuges of non-Bt host plants to promote survival of susceptible pests. To delay pest resistance to transgenic cotton producing Bt toxin Cry1Ac, farmers in the United States and Australia planted refuges of non-Bt cotton, while farmers in China have relied on “natural” refuges of non-Bt host plants other than cotton. Here we report data from a 2010 survey showing field-evolved resistance to Cry1Ac of the major target pest, cotton bollworm (Helicoverpa armigera), in northern China. Laboratory bioassay results show that susceptibility to Cry1Ac was significantly lower in 13 field populations from northern China, where Bt cotton has been planted intensively, than in two populations from sites in northwestern China where exposure to Bt cotton has been limited. Susceptibility to Bt toxin Cry2Ab did not differ between northern and northwestern China, demonstrating that resistance to Cry1Ac did not cause cross-resistance to Cry2Ab, and implying that resistance to Cry1Ac in northern China is a specific adaptation caused by exposure to this toxin in Bt cotton. Despite the resistance detected in laboratory bioassays, control failures of Bt cotton have not been reported in China. This early warning may spur proactive countermeasures, including a switch to transgenic cotton producing two or more toxins distinct from Cry1A toxins.

Understanding Crash Mechanisms and Selecting Interventions to Mitigate Real-Time Hazards on Urban Expressways

The concept of dynamic black spot identification has matured substantially over the past decade. Rather than being confined to improving prediction accuracy, the concept has expanded to understanding the crash mechanism by using sensor data and devising real-time countermeasures. A major drawback of most studies has been considering a crash as a generic mechanism throughout the expressway. Consequently, proposed countermeasures, such as warning messages, variable speed limits, and ramp metering, have been independent of location. Some studies have incorporated ramps as variables, but little progress has been made in investigating variation in the crash mechanism or evaluating the effectiveness of countermeasures separately for the basic freeway segments and ramp vicinities. This paper divides expressways into five segments: basic freeway, upstream and downstream of exits, and entrance ramps. The paper uses high-resolution detector data and advanced ensemble learning methods such as random forest and classification and regression trees to identify important factors and understand the crash mechanism. The outcome advocates lane-based speed management to improve the safety of basic freeway segments. Although ramp flows were found to contribute to crashes in ramp vicinities, the flows caused little concern for basic freeway segments. The findings will be valuable for researchers in predicting real-time crashes, investigating crash mechanisms, and designing proactive countermeasures.

Tool Support for Continuous Quality Control

Over time, software systems suffer gradual quality decay and therefore costs can rise if organizations fail to take proactive countermeasures. Quality control is the first step to avoiding this cost trap. Continuous quality assessments help users identify quality problems early, when their removal is still inexpensive; they also aid decision making by providing an integrated view of a software system's current status. As a side effect, continuous and timely feedback helps developers and maintenance personnel improve their skills and thereby decreases the likelihood of future quality defects. To make regular quality control feasible, it must be highly automated, and assessment results must be presented in an aggregated manner to avoid overwhelming users with data. This article offers an overview of tools that aim to address these issues. The authors also discuss their own flexible, open-source toolkit, which supports the creation of dashboards for quality control.

Terrorist backlash, terrorism mitigation, and policy delegation

This paper presents a three-stage proactive game involving terrorists, elected policymakers, and voters. In each of two targeted countries, a representative voter chooses an elected policymaker, charged with deciding proactive countermeasures to ameliorate a transnational terrorist threat. Two primary considerations drive the voters' strategic choice: free riding on the other countries' countermeasures and limiting a reprisal terrorist attack. The resulting low proactive countermeasures benefit the terrorists, whose attacks successfully exploit voters' strategic actions. This finding stems from a delegation problem where leadership by voters has a detrimental consequence on the well-being of targeted countries. Domestic politics add another layer of concern when addressing a common terrorist threat.

Silicon limitation on primary production and its destiny in Jiaozhou Bay, China

In this paper, the phenomenon that the variation in nutrient and water temperature could cause changes in phytoplankton growth and structure is examined; and the question of how a marine ecosystem make up the earth ecosystem step by step to auto-sustain the balance between phytoplankton and nutrient supply especially Si is discussed. Three major complementary mechanisms of the earth ecosystem for nutrient Si, water temperature and carbon were put forward. Understanding the mechanisms nowadays would explain the why the El Nino and La Nina occurred, and forecast the trend of human-impacted the earth, which would alert us with proactive countermeasures.