E6 Models from F-theory

F-theory is a non-perturbative formulation of type IIB superstring theory which allows for the decoupling of gravity and for the formulation of GUT theories based on the gauge group E6. In this paper we explore F-theory models in which the low energy supersymmetric theory contains the particle content of three 27 dimensional representations of the underlying E6 gauge group, plus two extra right-handed neutrinos predicted from F and D flatness. The resulting TeV scale effective theory resembles either the E6SSM or the NMSSM+, depending on whether an additional Abelian gauge group does or does not survive. However there are novel features compared to both these models as follows: (i) If the additional Abelian gauge group is unbroken then it can have a weaker gauge coupling than in the E6SSM; (ii) If the additional Abelian gauge group is broken then non-perturbative effects can violate the scale invariance of the NMSSM+ leading to a generalised model; (iii) Unification is achieved not at the field theory level but at the F-theory level since the gauge couplings are split by flux effects, negating the need for any additional doublet states which are usually required; (iv) Proton decay is suppressed by the geometric coupling suppression of a singlet state, a mechanism peculiar to F-theory, which effectively suppresses the coupling of the exotic charge -1/3 colour triplet state D to quarks and leptons; (v) The D bar couples to left-handed leptoquarks, providing characteristic and striking signatures at the LHC.Comment: 31 pages, 7 figure

Gauge Coupling Unification in E6 F-Theory GUTs with Matter and Bulk Exotics from Flux Breaking

We consider gauge coupling unification in E6 F-Theory Grand Unified Theories (GUTs) where E6 is broken to the Standard Model (SM) gauge group using fluxes. In such models there are two types of exotics that can affect gauge coupling unification, namely matter exotics from the matter curves in the 27 dimensional representation of E6 and the bulk exotics from the adjoint 78 dimensional representation of E6. We explore the conditions required for either the complete or partial removal of bulk exotics from the low energy spectrum. In the latter case we shall show that (miraculously) gauge coupling unification may be possible even if there are bulk exotics at the TeV scale. Indeed in some cases it is necessary for bulk exotics to survive to the TeV scale in order to cancel the effects coming from other TeV scale matter exotics which would by themselves spoil gauge coupling unification. The combination of matter and bulk exotics in these cases can lead to precise gauge coupling unification which would not be possible with either type of exotics considered by themselves. The combination of matter and bulk exotics at the TeV scale represents a unique and striking signature of E6 F-theory GUTs that can be tested at the LHC.Comment: 21 pages, 5 figure

Reflectance spectra of Fe(2+)-Mg(2+) disordered pyroxenes: Implications to remote-sensed spectra of planetary surfaces

The reflectance spectra of Fe(2+)-Mg(2+) disordered orthopyroxenes are relevant to surfaces of terrestrial planets onto which basaltic magma has been extruded. If cooling rates of basalt lava flows were fast, equilibrium iron intersite partitioning may not have been achieved so that abnormal enrichments of Fe(2+) ions in M1 sites would occur. The two intense pyroxene Fe(2+) site CF bands in the 1 micron and 2 micron regions would continue to dominate the the reflectance spectra so that the pyroxene composition and structure type would be readily identified in telescopic spectral profiles. However, abnormal intensification of the Fe(2+)/M1 site CF band at 1.20 microns could lead to the false identification of olivine in remote sensed spectra because in pyroxene-olivine mixtures the inflection around 1.20 microns is the only spectral feature for detecting the presence of olivine. The identification of iron-bearing plagioclase feldspars, too, would be obscured by the pyroxene Fe(2+)/M1 site CF band at 1.20 microns. Such interference would be a major problem if in situ reflectance spectra could be measured on the surface of Venus where ambient temperatures are as high as 475 C. Disordering of Fe(2+) and Mg(2+) ions comparable to that in the orthopyroxenes used in this spectral chemical study might be expected in low Ca pyroxenes occurring on the Venusian surface. Researchers conclude that Fe(2+)/M1 site spectral features need to be carefully assessed in remote-sensed spectra before deductions are made about the presence of olivine on planetary surfaces

Entrapment When the Spoken Word is the Crime

The task of this Article is to assess the competing approaches that circuit courts have taken in defining the predisposition element in entrapment cases. It then attempts to try to reconcile them, not only with Jacobson v. United States, but also with policy concerns underlying the rest of the Supreme Court\u27s entrapment jurisprudence, particularly in light of the increased politicization of federal criminal law through investigations of public officials\u27 conduct by independent counsel. This Article will first frame the central issue, the supplementary mens rea requirement arising in entrapment cases. Part II then will review the common law development of the federal entrapment defense, in the context of an independent counsel investigation of public officials for mens rea crimes, with particular emphasis on the Supreme Court\u27s 1992 decision in Jacobson v. United States. Part III will detail the two essentially divergent views that circuit courts have taken over the meaning of the term “predisposition” in the wake of the Court\u27s decision in Jacobson, including the 1994 opinion by Chief Judge Posner of the Seventh Circuit in United States v. Hollingsworth. The Article will explain that Hollingworth\u27s interpretation of Jacobson that when, “but for” the Government\u27s inducement, the defendant objectively would not have committed the offense in question, is incomplete. Part IV will attempt to reconcile the competing approaches with the Court\u27s previous entrapment decisions in an attempt to ascertain which approach is most consistent with its prior entrapment jurisprudence and which best helps attain the contemporary goal of reducing the “political” component of criminal judicial enforcement. The Article concludes that a more appropriate focus for judicial or jury application of the dispositive “predisposition” test for entrapment is on the objectively historical evidence of the defendant\u27s prior similar acts (justifying the Government\u27s initial decision to target the defendant) and his or her initial responses to government inducement (justifying any continued targeting)

Farmers’ Voices: Concerns within the Agricultural Advertiser-Media-Reader Triad

This study continues an examination of power relationships within the agricultural publishing triad: advertisers, periodicals, and producer readers. It focuses on the views of farmers about the farm periodicals they read and the agricultural marketers that advertise in those periodicals. A mail survey was used to learn the opinions and observations of farmers in a nationwide sample. The sample of 497 was randomly drawn from a government database by a commercial data supply service. Three waves of letters were used along with a $1 incentive. The 198 completed responses came from 29 states. Results indicate that producers are quite discerning and insightful in what they read. Furthermore, a majority expressed concern about advertiser-editorial relationships. Most said they see evidence of advertiser influence in the form of editorial trade-offs and bias in what stories are covered (or not covered) and how topics are handled. Results of a credibility index indicate there is much room for improvement. Authors suggest that farm publishers and advertisers should reconsider their relationships if they wish to address readers’ concerns and improve their credibility. In a highly competitive environment, increased credibility has positive bottom-line implications for all partners in the triad

Mixing Lengths of Coaxial Jets in a Rocket Combustor Configuration Using Acetone PLIF

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/77322/1/AIAA-2007-5590-512.pd

Counting Room Voices in the Farm Publisher-Reader-Advertiser Triad

This study is part of a series that examines changing power relationships among commercial farm periodicals, their readers, and advertisers. The series focuses upon the health, vigor, and credibility of a complex information system in which the U.S. food enterprise and society in general have an important stake. Authors employed a “contractualist model” in which power requires mutual agreement by all parties. Two previous studies in the series identified concerns of farm periodical journalists and readers about advertiser-related pressures on editorial content. Through qualitative research methods, the study reported here examined related views among a sample of agricultural publishers and advertisers. Both groups expressed the most concern about the consolidation taking place among producers, marketers, and publishers, but they focused on different sectors. All three kinds of consolidation have the effect of giving the advertiser more power within the triad. Publishers and advertisers emphasized the need to maintain editorial credibility of commercial farm periodicals, acknowledged advertiser-related pressures, but shared a feeling that such pressures can be controlled and should not influence the independent stance of editorial content. They differed somewhat, however, in views on managing the editorial-advertising “wall.” Publishers also identified ways in which they are adapting, through diversification, to changing strategies of advertisers in an era of consolidation and new information technologies. By revealing perspectives of all partners in the triad, findings provide a useful staging point for interactions and understandings

Fading Voices: A 10-Year Trend Within an Agricultural Advertiser-Media-Reader Triad

Research reported here addresses effective communications within agriculture by examining power relationships within the agricultural publishing triad: advertisers, periodicals and producer readers. A 10-year analysis using mail surveys among agricultural print journalists explores recent changes within this triad, including perceptions of trends in the levels, kinds, and effects of advertiser influence on editorial content of U.S. commercial farm periodicals. Results reveal increasing advertiser-related pressure on the journalists. Other findings examine perceived harm to the profession, publication policies used, and differences in response related to gender and age. Authors discuss implications and offer steps for follow-up through research and professional education

Rocket Combustion Properties for Coaxial Injectors Operated at Elevated Pressures

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/76596/1/AIAA-2006-4704-966.pd