Characterization of bacteriophage communities and CRISPR profiles from dental plaque.

BackgroundDental plaque is home to a diverse and complex community of bacteria, but has generally been believed to be inhabited by relatively few viruses. We sampled the saliva and dental plaque from 4 healthy human subjects to determine whether plaque was populated by viral communities, and whether there were differences in viral communities specific to subject or sample type.ResultsWe found that the plaque was inhabited by a community of bacteriophage whose membership was mostly subject-specific. There was a significant proportion of viral homologues shared between plaque and salivary viromes within each subject, suggesting that some oral viruses were present in both sites. We also characterized Clustered Regularly Interspaced Short Palindromic Repeats (CRISPRs) in oral streptococci, as their profiles provide clues to the viruses that oral bacteria may be able to counteract. While there were some CRISPR spacers specific to each sample type, many more were shared across sites and were highly subject specific. Many CRISPR spacers matched viruses present in plaque, suggesting that the evolution of CRISPR loci may have been specific to plaque-derived viruses.ConclusionsOur findings of subject specificity to both plaque-derived viruses and CRISPR profiles suggest that human viral ecology may be highly personalized

Inflaton Decay in an Alpha Vacuum

We study the alpha vacua of de Sitter space by considering the decay rate of the inflaton field coupled to a scalar field placed in an alpha vacuum. We find an {\em alpha dependent} Bose enhancement relative to the Bunch-Davies vacuum and, surprisingly, no non-renormalizable divergences. We also consider a modified alpha dependent time ordering prescription for the Feynman propagator and show that it leads to an alpha independent result. This result suggests that it may be possible to calculate in any alpha vacuum if we employ the appropriate causality preserving prescription.Comment: 16 pages, 1 figure, Revtex 4 preprin

Planetary Bistatic Radar

Planetary radar observations offer the potential for probing the properties of characteristics of solid bodies throughout the inner solar system and at least as far as the orbit of Saturn. In addition to the direct scientific value, precise orbital determinations can be obtained from planetary radar observations, which are in turn valuable for mission planning or spacecraft navigation and planetary defense. The next-generation Very Large Array would not have to be equipped with a transmitter to be an important asset in the world's planetary radar infrastructure. Bistatic radar, in which one antenna transmits (e.g., Arecibo or Goldstone) and another receives, are used commonly today, with the Green Bank Telescope (GBT) serving as a receiver. The improved sensitivity of the ngVLA relative to the GBT would improve the signal-to-noise ratios on many targets and increase the accessible volume specifically for asteroids. Goldstone-ngVLA bistatic observations would have the potential of rivaling the sensitivity of Arecibo, but with much wider sky access.Comment: 11 pages, 2 figures, To be published in the ASP Monograph Series, "Science with a Next-Generation VLA", ed. E. J. Murphy (ASP, San Francisco, CA

Teaching Learning Curves In An Undergraduate Economics Or Operations Management Course

Learning Curves has its roots in economics and behavioral psychology. Learning Curves theory has several business applications and is widely used in the industry. As faculty of Operations Management courses, we cover this topic in some depth in the classroom. In this paper, we present some of our teaching methods and material that have helped us in communicating the learning curves concept. The students have found these very helpful in grasping the concepts better. We present comparative charts that highlight the key differences among the three standard methods for learning curve calculations. Students find these comparative charts to be very helpful in understanding these methods and in choosing the least time-consuming method when a problem can be solved in more than one way – often important during a time based exam. Furthermore, we point out an error and an ambiguity in textbooks and also provide some insights into the formula method

Teaching Basic Probability In Undergraduate Statistics Or Management Science Courses

Standard textbooks in core Statistics and Management Science classes present various examples to introduce basic probability concepts to undergraduate business students. These include tossing of a coin, throwing a die, and examples of that nature. While these are good examples to introduce basic probability, we use improvised versions of Russian Roulette and found these to be very effective in communicating important concepts in probability to our business school students. We use these modified versions of Russian Roulette to communicate concepts such as dependent event, joint probabilities and the value of information using Bayes’ law. The students understand and enjoy these examples and the class participation has been higher than usual.

Computational Thinking Concepts for Grade School

Early education has classically introduced reading, writing, and mathematics. Recent literature discusses the importance of adding “computational thinking” as a core ability that every child must learn. The goal is to develop students by making them equally comfortable with computational thinking as they are with other core areas of early education. Computational thinking does not come naturally and requires training and guidance. This paper argues for the inclusion of computational thinking in tandem with mathematics. As an example, the paper demonstrates spreadsheet applications that can be utilized concurrently with early mathematical concepts. It demonstrates that at this time, spreadsheets are the best medium for inculcating computational thinking but recognizes that advances in technology may favor other digital approaches in time

Magnetic Field Structure and Stochastic Reconnection in a Partially Ionized Gas

We consider stochastic reconnection in a magnetized, partially ionized medium. Stochastic reconnection is a generic effect, due to field line wandering, in which the speed of reconnection is determined by the ability of ejected plasma to diffuse away from the current sheet along magnetic field lines, rather than by the details of current sheet structure. We consider the limit of weak stochasticity, so that the mean magnetic field energy density is greater than either the turbulent kinetic energy density or the energy density associated with the fluctuating component of the field. We consider field line stochasticity generated through a turbulent cascade, which leads us to consider the effect of neutral drag on the turbulent cascade of energy. In a collisionless plasma, neutral particle viscosity and ion-neutral drag will damp mid-scale turbulent motions, but the power spectrum of the magnetic perturbations extends below the viscous cutoff scale. We give a simple physical picture of the magnetic field structure below this cutoff, consistent with numerical experiments. We provide arguments for the reemergence of the turbulent cascade well below the viscous cut-off scale and derive estimates for field line diffusion on all scales. We note that this explains the persistence of a single power law form for the turbulent power spectrum of the interstellar medium, from scales of tens of parsecs down to thousands of kilometers. We find that under typical conditions in the ISM stochastic reconnection speeds are reduced by the presence of neutrals, but by no more than an order of magnitude.Comment: Astrophysical Journal in pres

Mathematical Modeling And Computational Thinking

The paper argues that mathematical modeling is the essence of computational thinking. Learning a computer language is a valuable assistance in learning logical thinking but of less assistance when learning problem-solving skills. The paper is third in a series and presents some examples of mathematical modeling using spreadsheets at an advanced level such as high school or early college

Some Comments On: A Historical Note On The Proof Of The Area Of A Circle

In a recent paper by Wilamowsky et al. [6], an intuitive proof of the area of the circle dating back to the twelfth century was presented. They discuss challenges made to this proof and offer simple rebuttals to these challenges. The alternative solution presented by them is simple and elegant and can be explained rather easily to non-mathematics majors. As business school faculty ourselves, we are in agreement with the authors. Our article is motivated by them and we present yet another alternative method. While we do not make an argument that our proposed method is any simpler, we do feel it may be easier to communicate to business school students. In addition, we present a solution using a rectangle which could be left as an exercise for the student after a brief explanation in class. Finding the area of a stack of rectangles with a rectangle as a starting point may seem redundant at first. However, we show that it is actually an excellent algebraic exercise for students since it offers a certain challenge which a square does not. We also solve this exercise using the quicker triangular approach and feel it can be appreciated by students in an Introduction to Calculus course. We also provide two interesting links that demonstrate the work of the ancient mathematicians for this well known problem

The social construction of identity in HIV/AIDS home-based care volunteers in rural KwaZulu-Natal, South Africa

Home-based care volunteer (HBCV) identity and how it is shaped was the main focus of the study. Fifteen HBCVs were interviewed about their work and personal life stories and then interviewed reflectively using a narrative interviewing style. Specific attention was paid to contextual meta-narratives and social field narratives in understanding the women’s stories. Findings indicate that social field narratives of the women’s stories were dominated by negative aspects of gender, poverty and socio-political factors. These were seen to coincide with the ‘feminisation of responsibility’ in this context effectively coercing the women into agency which manifested as theirhome-based care work. Meta-narratives influencing the women’s lives were dominated by stories of communal motherhood, aspirations to service-oriented work and religious beliefs and commitment. The question of how it is possible for women who are seemingly constrained by oppressive narratives to voluntarily engage in community participation was answered in the women’s personal life stories about being compassionate, hopeful, helpful and ambitious and having initiative. These characteristicscollectively pointed to personal agency. Exploring connections between the different aspects of identity and context revealed that the women made sense of their community participation through their personal identities as strong and loving mothers. Connections between volunteer personal identity, agency and volunteer group identity were explored to make sense of the link between HBCV identity and volunteerism. The mother identity, encompassing personal agency (strength or power) and love (themeta-narrative of communal motherly love), was salient in influencing community participation of the group