Archaeal ubiquity

In the seventeenth century, Antoine von Leeuwenhook used a simple microscope to discover that we live within a previously undetected microbial world containing an enormously diverse population of creatures. The late nineteenth and early twentieth century brought advances in microbial culture techniques and in biochemistry, uncovering the roles that microbes play in all aspects of our world, from causing disease to modulating geochemical cycles. In the last 25 years, molecular biology has revealed the complexity and pervasiveness of the microbial world and its importance for understanding the interactions that maintain living systems on the planet. The paper by Preston et al. (1) in this issue of the Proceedings provides a clear illustration of the power of these molecular techniques to describe new biological relationships and to pose important questions about the mechanisms that drive evolution. The analysis of ribosomal RNA gene sequences is one molecular approach that has radically altered our view of microbial diversity. Its application can be extended and expedited by the use of PCR. The confluence of these techniques has stimulated the rapid assembly of sequence information from homologues rRNA gene regions derived from virtually all classes of organisms. The data collected thus far support the scheme first presented by Woese et al. (2), which holds that the relationships among organisms can be summarized in the form of a universal phylogenetic tree comprised of one eukaryotic and two prokaryotic domains: the Eucarya, the Bacteria, and the Archaea (Fig. 1)

Women at risk for sexually transmitted diseases: correlates of intercourse without barrier contraception

Objective: The purpose of this study was to evaluate the correlates of vaginal intercourse without barrier contraception (unprotected intercourse). Study Design: Baseline data from a randomized trial were analyzed to evaluate factors that are associated with intercourse without barrier method use among women \u3c35 years old. Logistic regression models provided estimates of the association of demographic, reproductive, and sexual history variables with unprotected intercourse. Results: Intercourse without barrier contraception was common; 65% of participants had ≥2 episodes of intercourse without barrier contraception use in the past month. Factors that were associated with increased odds of unprotected intercourse included the number of coital episodes, a male partner’s unwillingness to use condoms (adjusted odds ratio, 4.1; 95% CI, 2.3-6.9), and, among women \u3c20 years old, low condom use self-efficacy score (adjusted odds ratio, 1.6; 95% CI, 1.0-2.9). Conclusion: Risk factors for unprotected intercourse included coital frequency and the male partner’s unwillingness to use condoms. Self-efficacy for condom use was especially important for women \u3c20 years old

Stance phase control of above-knee prostheses: Knee control versus SACH foot design

The mobility of above-knee amputees (A/K) is limited, in part, due to the performance of A/K prostheses during the stance phase. Currently stance phase control of most conventional A/K prostheses can only be achieved through leg alignment and choice of the SACH (Solid Ankle Cushioned Heel) foot. This paper examines the role of the knee controller in relation to a SACH foot during the stance phase of level walking.The three-dimensional gait mechanics were measured under two stance phase conditions. In the first set of trials, the amputee used a prosthesis with a conventional knee controller that allowed the amputee to maintain the knee joint in full extension during the stance phase. In the second set of trials, the prosthetic knee, during stance, echoed the modified kinematics of the amputee's sound (intact) knee that had been recorded during the previous sound stance phase.Analysis and interpretation of the data indicate the following: (1) SACH foot design can strongly influence the walking mechanics independent of the knee controller; (2) knee controller design and SACH foot design are mutually interdependent; and (3) normal kinematics imposed on the prosthetic knee does not necessarily produce normal hip kinematics (e.g. reduce the abnormal rise in the prosthetic side hip trajectory). Future research is necessary to explore and exploit the interdependency of prosthetic knee control and foot design.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/26850/1/0000413.pd

Effects of the Novel NMDA Receptor Antagonist Gacyclidine on Recovery From Medial Frontal Cortex Contusion Injury in Rats

Gacyclidine, a novel, noncompetitive NMDA receptor antagonist, was injected (i.v.) into rats at three different doses to determine if the drug could promote behavioral recovery and reduce the behavioral and anatomical impairments that occur after bilateral contusions of the medial frontal cortex (MFC). In the Morris water maze,contused rats treated with gacyciidine at a dosage of 0.1 mg/kg performed better than their vehicle-treated conspecifics. Rats given gacyclidine at either 0,3 or 0.03 mg/kg performed better than brain-injured controls, but not as well as those treated with 0.1 mg/kg. Counts of surviving neurons in the nucleus basalis magnoceilularis (NBM) and the medial dorsal nucleus (MDN) of the thalamus were used to determine whether gacyclidine treatment attenuated secondary cell death. In both the NBM and the MDN, the counts revealed fewer surviving neurons in untreated contused rats than in gacyclidine-treated rats. Increases in the size and number of microglia and astrocytes were observed in the striatum of gacyclidinetreated contused brains. Although most consequences of MFC contusions were attenuated, we still observed increases in ventricle dilation and thinning of the cortex. In fact, the ventricles of rats treated with 0.1 mg/kg of gacyclidine were larger than those of their vehicle treated counterparts, although we observed no behavioral impairment

A Base-Excitation Approach to Polynomial Chaos-Based Estimation

Abstract-This paper presents a novel method for identifying in real-time the sprung mass of a 2-DOF quarter-car suspension model. It does so by uniquely combining the base-excitation concept with polynomial chaos estimation. This unique combination of the two methods provides two important benefits. First, the base-excitation concept makes it possible to estimate the sprung mass without explicitly measuring or knowing the terrain profile prior to estimation. Second, the polynomial chaos estimation strategy makes it possible to perform such mass estimation using sprung and unsprung acceleration measurements without pseudo-integration filters that can be difficult to tune. This paper derives the proposed method in detail and presents computer simulations to evaluate its convergence speed and accuracy. The simulation results consistently converge to within 10% of the true mass value typically within 120 seconds

Danger on the Way to School: Exposure to ViolentCrime, Public Transportation, and Absenteeism

In this study, we propose and test a mechanism for the effect of neighborhood of residence on school outcomes: absenteeism that results from exposure to danger on the way to school. We first determine the most efficient route to school using public transportation for 4,200 first-time freshmen in Baltimore City public high schools. Then, we link the specific streets along the most efficient route to incident-level crime data from the Baltimore Police Department. We find that students whose estimated routes require walking along streets with higher violent-crime rates have higher rates of absenteeism throughout the year. We also show that absenteeism is not associated with exposure to dangerous streets while riding on public transit and exposure to property crime.These conclusions hold with and without adjustments for student demographic characteristics, prior school attendance, violent crime around homes and schools, and unobserved differences related to school preference and neighborhood selection

What does it take to learn in next generation learning spaces?

This chapter identifies the attributes that learners need in order to learn effectively in new technology rich educational environments. There are a number of different ways of synthesising the findings from this emerging literature which relies heavily on qualitative research. This chapter reports on a literature review which adopted a deliberately interpretative qualitative meta-analysis, synthesising the findings from 15 key studies. As such, the chapter demonstrates a way of reviewing and compiling current research. The synthesis resulted in the identification of six attributes that learners need to do well in next generation learning spaces. These are: engaged, connected, confident, adaptable, intentional and self-aware. Although some of these attributes are applicable to all learning contexts, those of being connected, confident, adaptable and intentional seem to be particularly important in learning in next generation learning spaces. The challenge is to design learning activities that encourage and reward the development of these attributes. The hope is that through both its findings and its method, this chapter provokes debate on what it now means to be a successful learner in today’s technology rich world

Size-dependent rheology of type-I collagen networks

We investigate the system size dependent rheological response of branched type I collagen gels. When subjected to a shear strain, the highly interconnected mesh dynamically reorients, resulting in overall stiffening of the network. When a continuous shear strain is applied to a collagen network, we observe that the local apparent modulus, in the strain-stiffening regime, is strongly dependent on the gel thickness. In addition, we demonstrate that the overall network failure is determined by the ratio of the gel thickness to the mesh size. These findings have broad implications for cell-matrix interactions, the interpretation of rheological tissue data, and the engineering of biomimetic scaffolds.Comment: 3 pages, 4 figures, to appear in Biophysical Journal Letters, September 201

A Cepheid Distance to NGC 4603 in Centaurus

In an attempt to use Cepheid variables to determine the distance to the Centaurus cluster, we have obtained images of NGC 4603 with the Hubble Space Telescope on 9 epochs using WFPC2 and the F555W and F814W filters. This galaxy has been suggested to lie within the ``Cen30'' portion of the cluster and is the most distant object for which this method has been attempted. Previous distance estimates for Cen30 have varied significantly and some have presented disagreements with the peculiar velocity predicted from redshift surveys, motivating this investigation. Using our observations, we have found 61 candidate Cepheid variable stars; however, a significant fraction of these candidates are likely to be nonvariable stars whose magnitude measurement errors happen to fit a Cepheid light curve of significant amplitude for some choice of period and phase. Through a maximum likelihood technique, we determine that we have observed 43 +/- 7 real Cepheids and that NGC 4603 has a distance modulus of 32.61 +0.11/-0.10 (random, 1 sigma) +0.24/-0.25 (systematic, adding in quadrature), corresponding to a distance of 33.3 Mpc. This is consistent with a number of recent estimates of the distance to NGC 4603 or Cen30 and implies a small peculiar velocity consistent with predictions from the IRAS 1.2 Jy redshift survey if the galaxy lies in the foreground of the cluster.Comment: Accepted for publication in the Astrophysical Journal. 17 pages with 17 embedded figures and 3 tables using emulateapj.sty. Additional figures and images may be obtained from http://astro.berkeley.edu/~marc/n4603