Identification of single bacterial cells in aqueous solution using confocal laser tweezers Raman spectroscopy

We report on a rapid method for reagentless identification and discrimination of single bacterial cells in aqueous solutions using a combination of laser tweezers and confocal Raman spectroscopy (LTRS). The optical trapping enables capturing of individual bacteria in aqueous solution in the focus of the laser beam and levitating the captured cell well off the cover plate, thus maximizing the excitation and collection of Raman scattering from the cell and minimizing the unwanted background from the cover plate and environment. Raman spectral patterns excited by a near-infrared laser beam provide intrinsic molecular information for reagentless analysis of the optically isolated bacterium. In our experiments, six species of bacteria were used to demonstrate the capability of the confocal LTRS in the identification and discrimination between the diverse bacterial species at various growth conditions. We show that synchronized bacterial cells can be well-discriminated among the six species using principal component analyses (PCA). Unsynchronized bacterial cells that are cultured at stationary phases can also be well-discriminated by the PCA, as well as by a hierarchical cluster analysis (HCA) of their Raman spectra. We also show that unsynchronized bacteria selected from random growth phases can be classified with the help of a generalized discriminant analysis (GDA). These findings demonstrate that the LTRS may find valuable applications in rapid sensing of microbial cells in diverse aqueous media.     

High-repetition-rate short-pulse gas discharge

A high-average-power short-pulse gas discharge is described. This consists of a volume-preionized transverse discharge of the type used in gas lasers driven by a Blumlein energy storage circuit. The Blumlein circuit is fabricated from coaxial cable, is pulse-charged from a high-repetition-rate Marx-bank generator, and is switched by a high-repetition-rate segmented rail gap. The operation of this discharge under conditions typical of rare-gas halide lasers is described. A maximum of 900 pps was obtained, giving a power flow into the discharge of 30 kW.     

Identifying joints from measured reflection coefficients in beam-like structures with application to a pipe support

The properties of joints in mechanical systems are notoriously uncertain causing corresponding uncertainty in the systems’ dynamic responses. A piping system is one such example where an accurate knowledge of joint properties is useful for the purposes of structure-borne sound transmission, fatigue considerations and structural health monitoring. This paper presents an inverse technique that is applicable to joint estimation in one-dimensional structures such as a pipe. Measured wave reflection coefficients are used which have several advantages over modal information. First, they characterise just the joint and adjacent pipes and are independent of the rest of the built-up system. Second, they are potentially more sensitive to the joint parameters in question than are modal parameters.The method is illustrated by means of an experimental case study featuring a straight pipe suspended by a cantilevered hanger. The stiffness and inertia of the hanger are accurately identified from measured data at frequencies significantly higher than the fundamental modes of the structure.     

The coevolution of human fertility and wealth inheritance strategies

Life history theory concerns the scheduling of births and the level of parental investment in each offspring. In most human societies the inheritance of wealth is an important part of parental investment. Patterns of wealth inheritance and other reproductive decisions, such as family size, would be expected to influence each other. Here I present an adaptive model of human reproductive decision-making, using a state-dependent dynamic model. Two decisions made by parents are considered: when to have another baby, and thus the pattern of reproduction through life; and how to allocate resources between children at the end of the parents' life. Optimal decision rules are those that maximize the number of grandchildren. Decisions are assumed to depend on the state of the parent, which is described at any time by two variables: number of living sons, and wealth. The dynamics of the model are based on a traditional African pastoralist system, but it is general enough to approximate to any means of subsistence where an increase in the amount of wealth owned increases the capacity for future production of resources. The model is used to show that, in the unpredictable environment of a traditional pastoralist society, high fertility and a biasing of wealth inheritance to a small number of children are frequently optimal. Most such societies are now undergoing a transition to lower fertility, known as the demographic transition. The effects on fertility and wealth inheritance strategies of reducing mortality risks, reducing the unpredictability of the environment and increasing the costs of raising children are explored. Reducing mortality has little effect on completed family sizes of living children or on the wealth they inherit. Increasing the costs of raising children decreases optimal fertility and increases the inheritance left to each child at each level of wealth, and has the potential to reduce fertility to very low levels. The results offer an explanation for why wealthy families are frequently also those with the smallest number of children in heterogeneous, post-transition societies.     

Correlates of suicidal behavior in a juvenile detention population

The present study identifies the correlates of current suicidal ideation and past suicide attempt among 555 adolescents in a county juvenile detention center. Suicidal behavior in delinquent boys was generally associated with depression and decreased social connection, whereas suicidal behavior in delinquent girls was associated with impulsivity and instability. Current ideation was most significantly associated with current depression. In multivariate analyses, past attempts were associated with suicidal ideation and ineffective coping for males, with major life events and impulsivity for females, and with not residing with at least one biological parent prior to detention for both males and females.     

Streamline generation code for particle dynamics description in numerical models of turbulence

Streamline Version 4 is a versatile Fortran 77 & C++ program for calculating charged test particle trajectories or field-lines for user-specified fields using the test-particle method. The user has the freedom to specify any type of field (analytical, tabulated in files, time dependent, etc.) and maintains complete control over initial conditions of trajectories/field-lines and boundary conditions of specified fields. The structure of Streamline was redesigned from previous versions in order to know not only particle or field-lines positions and velocities at each step of the simulations, but also the instantaneous field values as seen by particles. This was made to compute the instantaneous value of the particle’s magnetic moment, but other applications are possible too. Accuracy tests of the code are shown for different cases, i.e., particles moving in constant magnetic field, magnetic plus constant electric field and wave field. In addition in the last part of the paper we concentrate our discussion on the study of velocity space diffusion of charged particles in turbulent slab fields, paying attention to the discretization of the fields and the temporal discretization of the dynamical equations. The diffusion of charged particles is a very common topic in plasma physics and astrophysics since it plays an important role in many different phenomena such as stochastic particle acceleration, diffusive shock acceleration, solar energetic particle propagation, and the scattering required for the solar modulation of galactic cosmic rays.     

Unresolved theoretical issues in self-management: Implications for research and practice.

Discusses 2 unresolved theoretical issues in the self-management literature. Cognitive-behavioral and operant theories regarding the nature of self-reinforcement and the mechanisms responsible for reactive self-monitoring are presented, along with a literature review supporting the various theories. Areas in which additional research is needed to support a particular view are discussed. Recommendations for applying self-management procedures in school psychology are offered based on the literature. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The Synthesis and Anti-tumour Properties of Poly Ethoxy Ethyl Glycinamide (PEE−G) Scaffolds with Multiple PD-1 Peptides Attached

Multivalent structures can provide multiple interactions at a target site and improve binding affinity. The multivalent presentation of the anti-tumour heptapeptide, SNTSESF, was investigated. This peptide's activity has been attributed to blockade of the PD-1 receptor-mediated signalling pathway. Two and four peptide units were conjugated to poly ethoxy ethyl glycinamide (PEE−G) scaffolds to prepare high-purity products. These conjugates and the peptide were examined in a mouse model implanted with GL261 tumours that indicated that presenting more than two copies of peptide SNTSESF on the dendritic scaffold does not increase anti-tumour activity per peptide. The fluorescent labelled peptide and most active multivalent peptide conjugate were therefore screened for their interaction with the human PD−L1 protein in a fluorescence polarisation assay. No indication of a specific SNTSESF peptide/PD−L1 interaction was observed. This finding was further supported by a molecular modelling binding study.