Chicken genomics: feather-pecking and victim pigmentation

Feather-pecking in domestic birds is associated with cannibalism and severe welfare problems. It is a dramatic example of a spiteful behaviour in which the victim's fitness is reduced for no immediate direct benefit to the perpetrator and its evolution is unexplained. Here we show that the plumage pigmentation of a chicken may predispose it to become a victim: birds suffer more drastic feather-pecking when the colour of their plumage is due to the expression of a wild recessive allele at PMEL17, a gene that controls plumage melanization, and when these birds are relatively common in a flock. These findings, obtained using an intercross between a domestic fowl and its wild ancestor, have implications for the welfare of domestic species and offer insight into the genetic changes associated with the evolution of feather-pecking during the early stages of domestication.     

鸽蛋人工孵化和仔鸽并窝的试验研究

研究了鸽蛋人工孵化和仔鸽并窝对产鸽生产性能的影响。试验结果表明:鸽蛋人工孵化可有效减少破蛋率,降低死胎率,出雏率提高12.2%(P<0.05)。同时,使产蛋周期缩短30 d,差异极显著(P<0.01);并窝3只的乳鸽体重增长与非并窝的乳鸽相似,但饲料报酬明提较高,重料比差异极显著(P<0.01);并窝4只的仔鸽饲料报酬高,但乳鸽增重较慢。说明一对亲鸽完全有可能同时哺喂3~4只仔鸽,但以每窝并至3只仔鸽较理想。     

无公害肉鸽饲养管理技术的研究

无公害肉鸽标准之一是生长健康,饲养过程中不使用药物添加剂及生长激素;合理使用兽药及其它化学药品,降低肉鸽制品的药物残留,保证肉的口感争品质。本文从鸽场的建造、饲养方式、饲料配制、保健沙、管理、疾病用药等方面对无公害内鸽的饲养管理技术进行了探讨。     

Magnetoreception and its trigeminal mediation in the homing pigeon

Two conflicting hypotheses compete to explain how a homing pigeon can return to its loft over great distances. One proposes the use of atmospheric odours and the other the Earth's magnetic field in the 'map' step of the 'map and compass' hypothesis of pigeon homing. Although magnetic effects on pigeon orientation provide indirect evidence for a magnetic 'map', numerous conditioning experiments have failed to demonstrate reproducible responses to magnetic fields by pigeons. This has led to suggestions that homing pigeons and other birds have no useful sensitivity to the Earth's magnetic field. Here we demonstrate that homing pigeons (Columba livia) can discriminate between the presence and absence of a magnetic anomaly in a conditioned choice experiment. This discrimination is impaired by attachment of a magnet to the cere, local anaesthesia of the upper beak area, and bilateral section of the ophthalmic branch of the trigeminal nerve, but not of the olfactory nerve. These results suggest that magnetoreception (probably magnetite-based) occurs in the upper beak area of the pigeon. Traditional methods of rendering pigeons anosmic might therefore cause simultaneous impairment of magnetoreception so that future orientation experiments will require independent evaluation of the pigeon's magnetic and olfactory systems.     

家鸽红细胞血型的初步研究

采用2种方法对家鸽的红细胞血型进行了初步研究．方法一：血清平板凝集试验．取家鸽的红细胞分别与家兔以及其它家鸽的血清进行混合，结果有些家鸽的红细胞与有些家兔的血清发生了凝集反应，而另一些则不发生；家鸽的不同个体之间也存在红细胞凝集现象．这表明家鸽的红细胞表面存在凝集原．方法二：异种动物免疫．将家鸽的红细胞注射到家兔体内，然后取家兔产生的免疫血清与该家鸽的红细胞混合，结果发生了凝集反应．这进一步表明家鸽的红细胞表面存在凝集原，即家鸽具有红细胞血型．     

网络入侵检测系统的拒绝服务攻击的检测与防御

针对网络入侵检测系统的拒绝服务攻击(DOS)具有难于检测与防御的特点，提出了一种新颖的检测与防御算法。该算法通过分析告警的频率与分散度来检测DOS攻击，并采用分阶段切换的方式将状态检测由正常模式转为紧急模式，丢弃不属于正常TCP会话的数据包，以实现对DOS的防御。性能分析和实验结果表明，该算法能够及时发现、防御DOS攻击，有效地阻止DOS攻击所造成的系统破坏。     

Disruptive sexual selection for plumage coloration in a passerine bird

The theory of sexual selection was developed to explain the evolution of highly exaggerated sexual ornaments. Now supported by vast empirical evidence, sexual selection is generally considered to favour individuals with the most extreme trait expression. Here we describe disruptive selection on a sexual ornament, plumage coloration, in yearling male lazuli buntings (Passerina amoena). In habitats with limited good-quality nesting cover, the dullest and the brightest yearlings were more successful in obtaining high-quality territories, pairing with females and siring offspring, than yearlings with intermediate plumage. This pattern reflects the way that territorial adult males vary levels of aggression to influence the structure of their social neighbourhood. Adult males showed less aggression towards dull yearlings than intermediate and bright ones, permitting the dull yearlings to settle on good territories nearby. Fitness comparisons based on paternity analyses showed that both the adults and dull yearlings benefited genetically from this arrangement, revealing a rare example of sexually selected male-male cooperation.     

Plant genetics. Ancient wild olives in Mediterranean forests

Early domestication and extensive cultivation have meant that staple Mediterranean fruit crops such as olives, grapes and dates exist in wild-looking forms that are secondary derivatives produced by sexual reproduction among cultivated plants (cultivars), which were initially propagated vegetatively. By using genetic markers associated with characters that render plants unsuitable for domestication, we show here that genuinely wild olive trees, which cannot be distinguished morphologically from feral forms, still survive in a few Mediterranean forests. These wild stocks are genetically distinct and more variable than either the crop strains or their derived feral forms, a finding that has important implications for the conservation of these ancient lineages.     

A nonparametric adaptive CUSUM method and its application in source-end defense against SYN flooding attacks

Combating DDoS attacks at their sources is still in its infancy.In this paper,a nonparametric adaptive CUSUM (cumulative sum) method is presented,which is proven efficient in detecting SYN flooding attacks close to their sources.Different from other CUSUM methods,this new method has two distinct features:① its detection threshold can adapt itself to various traffic conditions and ② it can timely detect the end of an attack within a required delay.Trace-driven simulations are conducted to validate the efficacy of this method in detecting SYN flooding attacks,and the results show that the nonparametric adaptive CUSUM method excels in detecting low-rate attacks.     

密钥交换协议IKEv2的分析与改进

In ternet密钥交换协议第二版本(IKEv2)即将成为标准,分析该协议有助于更好地理解和实现该协议,针对协议存在的安全隐患提出改进措施。通过对协议的安全性分析,发现协议面临基于分片的拒绝服务攻击和退化消息类型的中间人攻击。针对前一种攻击提出了一种基于地址偏好列表的防御措施。针对后一种攻击提出了一种基于共享密钥的密钥生成方案。分析表明,使用这两种改进措施可以有效地提高协议抵抗拒绝服务攻击和退化消息攻击的能力。基于地址偏好列表的防御措施可以直接用于协议实现,改进的密钥生成方案可以为协议的下一个版本提供借鉴。     

一种改进的中间域多变量公钥签名方案

多变量公钥密码体制能抵抗量子计算机的攻击,被认为是后量子时代一种安全的密码体制备选方案.考虑到原中间域多变量公钥加密体制不能抵抗高阶线性化攻击,利用一种新的外部干扰,重构中心映射,提出一种基于外部干扰的改进签名方案.改进方案保持了原方案结构简单、求逆容易的性质,还能抵抗穷举攻击,秩攻击,差分攻击,代数攻击.     

Flying in a flock comes at a cost in pigeons

Flying birds often form flocks, with social, navigational and anti-predator implications. Further, flying in a flock can result in aerodynamic benefits, thus reducing power requirements, as demonstrated by a reduction in heart rate and wingbeat frequency in pelicans flying in a V-formation. But how general is an aerodynamic power reduction due to group-flight? V-formation flocks are limited to moderately steady flight in relatively large birds, and may represent a special case. What are the aerodynamic consequences of flying in the more usual 'cluster' flock? Here we use data from innovative back-mounted Global Positioning System (GPS) and 6-degrees-of-freedom inertial sensors to show that pigeons (1) maintain powered, banked turns like aircraft, imposing dorsal accelerations of up to 2g, effectively doubling body weight and quadrupling induced power requirements; (2) increase flap frequency with increases in all conventional aerodynamic power requirements; and (3) increase flap frequency when flying near, particularly behind, other birds. Therefore, unlike V-formation pelicans, pigeons do not gain an aerodynamic advantage from flying in a flock. Indeed, the increased flap frequency, whether due to direct aerodynamic interactions or requirements for increased stability or control, suggests a considerable energetic cost to flight in a tight cluster flock.     

Palaeontology: leg feathers in an Early Cretaceous bird

Here we describe a fossil of an enantiornithine bird from the Early Cretaceous period in China that has substantial plumage feathers attached to its upper leg (tibiotarsus). The discovery could be important in view of the relative length and aerodynamic features of these leg feathers compared with those of the small 'four-winged' gliding dinosaur Microraptor and of the earliest known bird, Archaeopteryx. They may be remnants of earlier long, aerodynamic leg feathers, in keeping with the hypothesis that birds went through a four-winged stage during the evolution of flight.     

体育恐怖袭击事件探析

通过对体育赛事中发生的恐怖袭击事件进行梳理,探析重大体育恐怖袭击事件发生的特征与深层次原因,发现：政治霸权与政治纷争是体育恐怖袭击事件发生的本质原因;体育赛事的高影响度是体育恐怖袭击事件发生的主要原因;不同体育文明冲突与意识形态是体育恐怖袭击事件发生的重要原因。提出预防和消除体育恐怖袭击事件的对策：全球共同努力建立公正合理的国际政治经济新秩序;发挥体育推动世界和平共处与社会和谐发展的功能;加强大型体育赛事的安保措施。     

北京雨燕幼鸟羽毛生长发育研究初报

北京雨燕是中国北方常见鸟类,作者于1985年4月至1988年8月对北京雨燕幼鸟羽毛发育进行了初步研究。研究表明,幼鸟羽毛发育有严格的规律性。在呼和浩特地区常见窝雏数为两雏鸟,所以仅对两雏幼鸟的羽毛发育进行描述。刚孵化的北京雨燕全身裸露,8日龄时长出飞羽鞘与尾羽鞘,18日龄时羽毛覆满全身。30日龄时两翅可在背部重迭。背部羽毛生长早于腹部羽毛。幼乌离巢时羽毛分布情况与成体相似,仅羽色比成体为淡。     

Chunking by a pigeon in a serial learning task

A basic principle of human memory is that lists that can be organized into memorable 'chunks' are easier to remember. Memory span is limited to a roughly constant number of chunks and is to a large extent independent of the amount of informaton contained in each chunk. Depending on the ingenuity of the code used to integrate discrete items into chunks, one can substantially increase the number of items that can be recalled correctly. Newly developed paradigms for studying memory in non-verbal organisms allow comparison of the abilities of human and non-human subjects to memorize lists. Here I present two types of evidence that pigeons 'chunk' 5-element lists whose components (colours and achromatic geometric forms) are clustered into distinct groups. Those lists were learned twice as rapidly as a homogeneous list of colours or heterogeneous lists in which the elements are not clustered. The pigeons were also tested for knowledge of the order of two elements drawn from the 5-element lists. They responded in the correct order only to those subsets that contained a chunk boundary. Thus chunking can be studied profitably in animal subjects; the cognitive processes that allow an organism to form chunks do no presuppose linguistic competence.     

Evidence from mitochondrial DNA that African honey bees spread as continuous maternal lineages

African honey bees have populated much of South and Central America and will soon enter the United States. The mechanism by which they have spread is controversial. Africanization may be largely the result of paternal gene flow into extant European populations or, alternatively, of maternal migration of feral swarms that have maintained an African genetic integrity. We have been using both mitochondrial and nuclear DNA restriction fragment length polymorphisms to follow the population dynamics between European and African bees. In earlier reports, we suggested that if African honey bees had distinctive mitochondrial (mt) DNA, then it could potentially distinguish the relative contributions of swarming and mating to the Africanization process. Because mtDNA is maternally inherited, it would not be transmitted by mating drones and only transported by queens accompanying swarms. Furthermore, the presence of African mtDNA would reflect unbroken maternal lineages from the original bees introduced from Africa. The value of mtDNA for population studies in general has been reviewed recently. Here we report that 19 feral swarms, randomly caught in Mexico, all carried African mtDNA. Thus, the migrating force of the African honey bee in the American tropics consists of continuous African maternal lineages spreading as swarms. The mating of African drones to European queens seems to contribute little to African bee migration.     

A new relay attack on distance bounding protocols and its solution with time-stamped authentication for RFID

Relay attack is one of the most threatening challenges against radio frequency identification(RFID) now. Distance bounding protocols have been introduced to thwart relay attacks. They form a family of challenge-response authentication protocols and confirm the round-trip time at the Rapid Bit Exchange phase. They enable a reader to authenticate and to establish an upper bound on the physical distance to an entrusted tag. We design an effective attack against a family of such protocols to launch the spoofing attacks within effective distance successfully, which demonstrates that existing protocols cannot eliminate such attacks completely. The thesis proposes a new program with time- stamping verification to correct the defect and verify the effectiveness.     

Structural Fault Tolerance of Scale-Free Networks

The fault tolerance of scale-free networks is examined in this paper. Through the simulation on the changes of the average path length and network fragmentation of the Barabasi-Albert model when faults happen, it can be observed that generic scale-free networks are quite robust to random failures, but are very vulnerable to targeted attacks at the same time. Therefore, an existing optimization strategy for the robustness of scale-free networks to failures and attacks is also introduced. The simulation similar with the above proved that the so-called (1,0) network has potentially interconnectedness closer to that of a scale-free network and robustness to targeted attacks closer to that of an exponential network. Furthermore,its resistance to random failures is better than that of either of them.     

无线传感器网络路由协议安全问题分析

现有的针对无线传感器网络的路由协议的设计主要目标是保证通信的同时,降低节点的能耗,缺乏对路由安全性的考虑。因此这类路由协议存在众多安全隐患,易于受到攻击并且在很多领域无法有效应用。文中先就可能的针对各种路由协议的攻击类型做了分析说明。在此基础上,结合典型路由协议的算法思想和工作特点,对存在的漏洞和安全隐患做出分析。最后,找出几种典型的无线传感器网络路由协议各自的安全漏洞和易于受到的攻击类型。