The fate of Newton's law in brane-world scenarios

We consider brane-world scenarios embedded into string theory. We find that the D-brane backreaction induces a large increase in the open string's proper length. Consequently the stringy nature of elementary particles can be detected at distances much larger than the fundamental string scale. As an example, we compute the gravitational potential between two open strings ending on backreacting D3-branes in four-dimensional compactifications of type II string theory. We find that the Newtonian potential receives a correction that goes like 1/r but that is not proportional to the inertial masses of the open strings, implying a violation of the equivalence principle in the effective gravitational theory. This stringy correction is screened by thermal effects when the distance between the strings is greater than the inverse temperature. This suggests new experimental tests for many phenomenological models in type II string theory.Comment: 8 pages, 3 figure

Administrator Development: A Step Beyond Training

Busy School administrators have too many fish to fry to be subjected to remedial, piecemeal, uncoordinated, though well intended management training. (New Curriculum and Training Techniques.

9. Teaching Assessment: The Administrator\u27s Perspective

School administrators, especially principals, are under great pressure to insure high levels of teacher competence. Because the school effectiveness research has demonstrated convincingly that effective schools begin with effective principals, Peterson and Finn (1985) drew a less than surprising conclusion by stating that Practically never does one encounter a good school with a bad principal (p. 42). A less pedantic east Texas superintendent put it this way, Bad principals are like fish; you either can \u27em or smell \u27em for a long time. It is in the complex area of teaching assessment or teacher evaluation that principals draw the most criticism from classroom teachers and particularly from university pundits. As McLaughlin (1986), a longtime student of teacher evaluation, put it: Teachers seldom respect principals as experts on classroom practice or as skilled classroom observers, and in the absence of principal credibility, teachers consider the evaluation an illegitimate comment on their performance and ignore the findings (p. 163). Teacher evaluation, in short, is an activity that most principals have little interest in or capacity to carry out (p. 170). Epstein (1985) said that Critics of current evaluation schemes complain that most are based on the principal\u27s ratings on teachers that result from infrequent (sometimes just one) observations in teachers\u27 classrooms; on cronyism, patronage, or other prejudicial decisions; or on seniority, credentials, and accumulated credits that do not involve the evaluation of teaching skills (p. 3). Principals and teachers vary greatly in how they perceive the principal\u27s performance as an evaluator, according to a survey of teachers and principals in Massachusetts (Tirrell, 1986). The respondents were asked to rate the role of the principal in evaluation according to their current perceptions and ideal expectations. Principals and teachers disagreed on 28 of 37 statements concerning current perceptions. They disagreed whether or not the principal clearly communicates the philosophy of the evaluation program to the staff; clearly states the purpose of the evaluation in writing to the teachers; ensures that the teachers know and understand the caliber of their work; ensures that teachers are not threatened by evaluation practices; and encourages teachers to experiment with new behaviors designed to address weaknesses indicated in previous evaluations. (pp. 31, 32) Other studies raise questions about the accuracy of measurement instruments \u27 and their criteria to distinguish the truly outstanding teacher from the average or even minimally competent one. Young (1986) identified five major faults in most observation instruments. They are as follows: (a) high inference items, (b) too many items, (c) judgments based on teacher actions, (d) low interrater reliability, and (e) lack of research support. Other research suggests that various groups disagree on the criteria they use to judge teachers. Epstein (1985) found that parents judge teachers on the basis of the degree to which the teacher communicates with the child\u27s family, whereas principals give much less weight to this factor. In attempting to determine whether people evaluate teaching excellence with the same criteria as they use to evaluate incompetence in teaching, Carey (1986) found that, Unlike minimal competence ratings, it might be more difficult to achieve consensus in judgments of excellence in teaching. If this contention is supported in further research it may be that merit pay and mentor teacher plans suffer an Achilles heel that will be difficult to remediate. (p . 10) The use of student scores on standardized achievement tests has become the major criterion used by some evaluators to judge teacher competence. St. Louis, Missouri, teachers were told by the superintendent in 1985 that they would be rated unsatisfactory and lose their jobs unless their students reached specific levels of achievement or improvement on standardized achievement tests (Shanker, 1986, p . 3c). Other authorities, while urging evaluators to have multiple data sources for more accurate teacher evaluations, are calling for more testing to determine teacher effectiveness. According to Manatt (1986), evaluators are going to have to go, deeper than inferences based on research on teaching. We want to look at student test data broken out by classrooms ... . That way and only that way, can you really narrow it down to a teacher rather than saying in general that the school got these achievements for these boys and girls. (p. 12) Most researchers and practicing administrators agree \u27that the better teacher evaluation systems can discriminate good teachers from dreadful teachers, and adequate teachers from bad teachers. However, few knowledgeable educators believe that they can segregate the master or clearly outstanding teacher from the really good teacher. This fine line appears to be the source of much of the heat and criticism generated by teacher groups and researchers about the state-of-the art in teacher evaluation

Circadian Rhythms: Hijacking the Cyanobacterial Clock

SummaryUsing basic research to advance a practical application, a recent study demonstrates that the circadian clock in cyanobacteria can be ‘reprogrammed’ to improve yields of heterologous protein production — a green future surely beckons

Polyethylene crystallized under the combined orientation and pressure effects in the Instron Capillary Rheometer.

Crystallization of a polymer while it is subjected to orientation has recently become a subject of great interest. This introductory study is concerned with inducing crystallization under the influence of pressure and orientation and also with the nature of the crystalline structure so formed from two commercial high density polyethylenes. The resins utilized are Phillips Marlex 6009 having a melt index of 0,9 and Dupont Alathon 7050 having a melt index of 2.1. As most of the experiments were conducted on the Dupont samples, the subject will be Alathon 7050 unless noted otherwise. The Marlex 6009, with its distinctly different melt index, was largely used to confirm the generality of the phenomena observed with the Alathon 7050. Crystallization is induced in a capillary of 0.0508 cm. diameter, 2.56 cm. length, and 90° entrance angle by means of an Instron Capillary Rheometer operating at constant plunger velocity

Deconstructing the LGBT-Victimization Association: The Case of Sexual Assault and Alcohol-Related Problems

Research on lesbian, gay, bisexual and/or transgender (LGBT) students has been gaining traction in the fields of criminology, victimology, and education, but available data lag behind the demand for studies on this underserved population. While LGBT students are often perceived to face greater risk of victimization and subsequent health problems than their counterparts, little research has investigated the mechanisms behind problematic outcomes for LGBT students. This research uses data from a Southeastern University to examine sexual assault among LGBT students and their experiences with alcohol-related problems. The results show that LGBT youth are at an increased risk for sexual victimization but that LGBT status does not have a direct effect on alcohol-related problems

Some Late-time Asymptotics of General Scalar-Tensor Cosmologies

We study the asymptotic behaviour of isotropic and homogeneous universes in general scalar-tensor gravity theories containing a p=-rho vacuum fluid stress and other sub-dominant matter stresses. It is shown that in order for there to be approach to a de Sitter spacetime at large 4-volumes the coupling function, omega(phi), which defines the scalar-tensor theory, must diverge faster than |phi_infty-phi|^(-1+epsilon) for all epsilon>0 as phi rightarrow phi_infty 0 for large values of the time. Thus, for a given theory, specified by omega(phi), there must exist some phi_infty in (0,infty) such that omega -> infty and omega' / omega^(2+epsilon) -> 0 as phi -> 0 phi_infty in order for cosmological solutions of the theory to approach de Sitter expansion at late times. We also classify the possible asymptotic time variations of the gravitation `constant' G(t) at late times in scalar-tensor theories. We show that (unlike in general relativity) the problem of a profusion of ``Boltzmann brains'' at late cosmological times can be avoided in scalar-tensor theories, including Brans-Dicke theory, in which phi -> infty and omega ~ o(\phi^(1/2)) at asymptotically late times.Comment: 14 page