Groups and semigroups with a one-counter word problem

We prove that a finitely generated semigroup whose word problem is a one-counter language has a linear growth function. This provides us with a very strong restriction on the structure of such a semigroup, which, in particular, yields an elementary proof of a result of Herbst, that a group with a one-counter word problem is virtually cyclic. We prove also that the word problem of a group is an intersection of finitely many one-counter languages if and only if the group is virtually abelian

Spectroscopic Studies of Brooker\u27s Merocyanine in Zeolite L

Zeolites are porous, crystalline substances that have very unique atomic organizations which allow for the formation of complex channels within the crystals. Each type of zeolite has a distinct shape and structure. To better understand the properties of zeolite channels, a dye molecule known as Brooker’s merocyanine was inserted into Zeolite L. Maximum dye loading into the zeolite channels was achieved by altering different experimental variables, such as heat, solution concentration, stirring, cation exchange, and light exposure. X-ray diffraction was used to verify the synthesis of zeolites, the cation exchange process, and dye loading. UV-Vis spectroscopy was used to measure the amount of dye adsorbed by the zeolite. By using the UV-Vis absorbance values and Beer’s Law, the concentration of dye in the zeolites was determined. The results showed that an increase of heat and stirring correlated to an increase of adsorption of dye by the zeolite. Due to the light sensitivity of Brooker’s merocyanine, it was found that limiting the amount of light exposure of the dye solutions also resulted in higher dye adsorption by the zeolites. An increase of the concentration of the dye solution increased the rate of adsorption in the channels. However, exchanging the potassium ions found within the synthesized Zeolite L channels with smaller hydrogen ions did not have an affect on the adsorption of dye in the channels. Characterizing how to achieve a maximum of dye adsorption in the zeolites allows for a better understanding of how dye molecules interact within the zeolite channels

Examining the Correlates of Failed DRDoS Attacks

Over the last decade, there has been a rise in cybercrime services offered on a feefor- service basis, enabling individuals to direct attacks against various targets. One of the recent services offered involves stresser or booter operators, who offer distributed reflected denial of service (DRDoS) attacks on an hourly or subscription basis. These attacks involve the use of malicious traffic reflected off of webservers to increase the volume of traffic, which is directed toward websites and servers rendering them unusable. Researchers have examined DRDoS attacks using realtime data, though few have considered the experience of their customers and the factors associated with the likelihood of successful attack outcomes. This study examines this issue using a binary logistic regression analysis of survey responses from a population of stresser clients. The implications of this study for our understanding of the social factors underlying cyberattacks is discussed in depth

CNOOC-UNOCAL and the WTO: Discriminatory Rules in the China Protocol Are a Latent Threat to the Rule of Law in the Dispute Settlement Understanding

In the summer of 2005, the Chinese state-owned oil company CNOOC, Ltd. (“CNOOC”) attempted to purchase American-owned Unocal Corporation on very favorable terms. There was a serious problem with the merger, however—the U.S. Congress was not about to let the People’s Republic of China (“China”) buy up an American company, no matter how much it was willing to pay. Following a period of increasingly heated rhetoric about the deal, the U.S. Congressman representing competitor Chevron Corporation’s home district inserted a provision in the Energy Policy Act of 2005 that was intended to, and did, scuttle the deal. The U.S. Congress’ underlying concern that Chinese ownership of a U.S. oil company would threaten national security (whether justified or not) obscured a potentially larger issue. China had already agreed not to grant the type of subsidy that made CNOOC’s offer possible when it acceded to the World Trade Organization (“WTO”). Incorporated into the Protocol on the Accession of the People’s Republic of China (“China Protocol”) was a commitment that China would not use unprofitable “noncommercial” loans from its state-owned enterprises to further state policy. The Unocal acquisition was to be funded by precisely this type of subsidized loan. The unique WTO rules contained in the China Protocol do more than prevent China from buying U.S. companies, however. The rules are applicable only to China, and prevent conduct that would be allowed under any generally applicable WTO agreement. As such, they undermine the core nondiscrimination principles on which the WTO was founded. More seriously, unresolved interpretative conflicts between the China Protocol and the set of agreements into which it is putatively “integrated” will force the WTO’s panels and Appellate Body to make “WTO common law,” a function specifically forbidden to them. This will seriously undermine the legitimacy of the WTO’s crucially important Dispute Settlement Understanding, and call into question the continued efficacy of the organization as a whole

Identification of a Functional Hotspot on Ubiquitin Required for Stimulation of Methyltransferase Activity on Chromatin

Histone post-translational modifications modulate chromatin structure and function either by directly altering the intrinsic physical properties of the chromatin fiber or by nucleating the recruitment and activity of a host of transacting nuclear factors. Histone ubiquitylation is one class of histone PTMs where the 76 amino acid protein, ubiquitin, is ligated to the ε-nitrogen of a lysine amino acid residue within the histone substrate. 36 unique ubiquitin sites across the 4 canonical histones have been annotated, with 7 of these sites associated with chromatin-templated processes. One such modification, the ubiquitylation of Histone H2B at lysine 120 (H2B-Ub) is enriched at the 5’ end of active genes and has been implicated in transcriptional elongation and chromatin conformation, interacting with over 90 trans-acting nuclear factors. Further, it is additionally responsible for the regulation of H3K4 and H3K79 methylations, through the direct stimulation of methyltransferase activity specific to the installation of these marks. Interested in the surface features on ubiquitin required for H2B-Ub stimulation of the human H3K79 methyltransferase, hDot1L, we developed a strategy for the site-specific chemical ligation of ubiquitin to preassembled mononucleosomes to greatly expedite structure activity studies of ubiquitin in a nucleosome context. Accordingly, we synthesized a library of H2Bligated ubiquitin alanine mutant nucleosomes and tested their ability to stimulate hDot1L-mediated H3K79 methylation. A functional hotspot on Ub that is required for the stimulation of hDot1L activity in vitro was identified. We additionally investigated the structural implication of this functional hotspot in the context of nucleosomes and nucleosomal array compaction. Both nucleosomal structural and H2B-Ub-induced impairment of chromatin fiber compaction was not affected by this functional surface. Lastly, this functional hotspot was further tested with the yeast H3 methyltransferases, yDot1 and ySet1C. Surprisingly, this functional surface was dispensable for yDot1-mediated H3K79 methylation both in vivo and in vitro. Further insights into yDot1-mediated H3K79 methylation was obtained through an alanine scan of the Ub surface in the context of the nucleosome. Interestingly, the hDot1L hotspot within ubiquitin was found to be important for the regulation of ySet1-mediated H3K4 methylation. Collectively, these data delineate the multi-functionality of H2B-Ub as a histone post-translational modification

Hacks, Cracks, and Crime: An Examination of the Subculture and Social Organization of Computer Hackers

This dissertation examines both the subculture and social organization practices of computer hackers. The concept of normative orders (Herbert, 1998: 347) is used to explore hacker subculture in different contexts. To assess hacker social organization, I use Best and Luckenbill¿s (1994) framework of organizational sophistication as well as measures from Decker et al. (1998). The relationships between subculture, social organization, and behavior are explored as well. I collected three qualitative data sets to explore these issues, including posts from six on-line hacker discussion forums, in-depth interviews with active hackers, and field observations at the Defcon 12 hacker convention. These data were triangulated and used to investigate the research questions. The findings suggest the social world of hackers is shaped by five normative orders: technology, knowledge, commitment, categorization, and law. These orders are interrelated, and overwhelmingly influenced by technology. Furthermore, hackers tend to perform hacks alone, but have relatively loose social networks that are used to share information and introduce subcultural norms to new hackers. These networks are couched in a larger hacker community that provided access to a variety of resources and materials. Finally, this analysis demonstrates the dynamic relationships between subculture, social organization, and behavior. I found that subculture and social organization structure the nature of deviant relationships, norms, and behavior. At the same time, the nature of deviant acts appears to influence social organization and subculture. I also discuss the implications for research on computer hackers and crime generally

Groups with context-free co-word problem

The class of co-context-free groups is studied. A co-context-free group is defined as one whose coword problem (the complement of its word problem) is context-free. This class is larger than the subclass of context-free groups, being closed under the taking of finite direct products, restricted standard wreath products with context-free top groups, and passing to finitely generated subgroups and finite index overgroups. No other examples of co-context-free groups are known. It is proved that the only examples amongst polycyclic groups or the Baumslag–Solitar groups are virtually abelian. This is done by proving that languages with certain purely arithmetical properties cannot be context-free; this result may be of independent interest