Subcellular Localization of the Leucine Biosynthetic Enzymes in Yeast

When baker's yeast spheroplasts were lysed by mild osmotic shock, practically all of the isopropylmalate isomerase and the β-isopropylmalate dehydrogenase was released into the 30,000 × g supernatant fraction, as was the cytosol marker enzyme, glucose-6-phosphate dehydrogenase. α-Isopropylmalate synthase, however, was not detected in the initial supernatant, but could be progressively solubilized by homogenization, appearing more slowly than citrate synthase but faster than cytochrome oxidase. Of the total glutamate-α-ketoisocaproate transaminase activity, approximately 20% was in the initial soluble fraction, whereas solubilization of the remainder again required homogenization of the spheroplast lysate. Results from sucrose density gradient centrifugation of a cell-free particulate fraction and comparison with marker enzymes suggested that α-isopropylmalate synthase was located in the mitochondria. It thus appears that, in yeast, the first specific enzyme in the leucine biosynthetic pathway (α-isopropylmalate synthase) is particulate, whereas the next two enzymes in the pathway (isopropylmalate isomerase and β-isopropylmalate dehydrogenase) are “soluble,” with glutamate-α-ketoisocaproate transaminase activity being located in both the cytosol and particulate cell fractions

Role of Endovascular Grafts in Combined Vascular and Skeletal Injuries of the Lower Extremity: a Preliminary Report

Background: A gunshot wound to the lower extremity with combined skeletal and vascular injuries can be difficult to manage. In clinical practice, it is not always possible to assemble a multispecialty team to work seamlessly to attain this goal, and the end result may be unnecessary prolonged ischemic time. A covered endovascular stent (EVS) can be used initially to restore perfusion without need of a time-consuming temporary shunt in select cases. Objectives: The objective of this study is to compare novel methods of repairing the superficial femoral artery to the traditional three-step operative approach in patients that have a concomitant femur fracture. Patients and Methods: All patients with combined vascular and skeletal injuries to the lower extremity were reviewed retrospectively. Patients were divided into three groups: Group 1: EVS placed percutaneously. Group 2: EVS placed with a hybrid combination of open and endovascular technique. Group 3: Placement of temporary shunt followed by skeletal stabilization and definitive vascular repair. Results: There were 16 patients identified. Group 1 = three, Group 2 = six, Group 3 = seven. EVS can shorten time to revascularization and prevents a second episode of vascular interruption at the time of the final vascular repair. The structural stability of the EVS was strong enough to withstand the skeletal manipulation without deformation of the stent. Conclusions: EVS is comparable to open repair and has the strength to withstand orthopedic manipulation in the short term when used in combined vascular and skeletal injuries to the lower extremity. Ischemic time is reduced significantly if final revascularization is accomplished at the onset with an EVS and the process is more efficient if the trauma surgeon is able to repair the vascular injury. With increasing sophistication of endovascular devices, this offers an appealing approach to vascular injuries that will decrease ischemic and total operative times when compared to the more traditional three-stage repair

Development of a new laser Doppler velocimeter for the Ames High Reynolds Channel No. 2

A new two-channel laser Doppler velocimeter developed for the Ames High Reynolds Channel No. 2 is described. Design features required for the satisfactory operation of the optical system in the channel environment are discussed. Fiber optics are used to transmit the megahertz Doppler signal to the photodetectors located outside the channel pressure vessel, and provision is made to isolate the optical system from pressure and thermal strain effects. Computer-controlled scanning mirrors are used to position the laser beams in the channel flow. Techniques used to seed the flow with 0.5-micron-diam polystyrene spheres avoiding deposition on the test-section windows and porous boundary-layer removal panels are described. Preliminary results are presented with a discussion of several of the factors affecting accuracy

Estimating process capability index Cpm using a bootstrap sequential sampling procedure

Construction of a confidence interval for process capability index CPM is often based on a normal approximation with fixed sample size. In this article, we describe a different approach in constructing a fixed-width confidence interval for process capability index CPM with a preassigned accuracy by using a combination of bootstrap and sequential sampling schemes. The optimal sample size required to achieve a preassigned confidence level is obtained using both two-stage and modified two-stage sequential procedures. The procedure developed is also validated using an extensive simulation study.<br /

Visual motherese? Signal-to-noise ratios in toddler-directed television

Younger brains are noisier information processing systems; this means that information for younger individuals has to allow clearer differentiation between those aspects that are required for the processing task in hand (the ‘signal’) and those that are not (the ‘noise’). We compared toddler-directed and adult-directed TV programmes (TotTV/ATV). We examined how low-level visual features (that previous research has suggested influence gaze allocation) relate to semantic information, namely the location of the character speaking in each frame. We show that this relationship differs between TotTV and ATV. First, we conducted Receiver Operator Characteristics analyses and found that feature congestion predicted speaking character location in TotTV but not ATV. Second, we used multiple analytical strategies to show that luminance differentials (flicker) predict face location more strongly in TotTV than ATV. Our results suggest that TotTV designers have intuited techniques for controlling toddler attention using low-level visual cues. The implications of these findings for structuring childhood learning experiences away from a screen are discussed

Quasi-normal modes of charged, dilaton black holes

In this paper we study the perturbations of the charged, dilaton black hole, described by the solution of the low energy limit of the superstring action found by Garfinkle, Horowitz and Strominger. We compute the complex frequencies of the quasi-normal modes of this black hole, and compare the results with those obtained for a Reissner-Nordstr\"{o}m and a Schwarzschild black hole. The most remarkable feature which emerges from this study is that the presence of the dilaton breaks the \emph{isospectrality} of axial and polar perturbations, which characterizes both Schwarzschild and Reissner-Nordstr\"{o}m black holes.Comment: 15 pages, 5 figure

Doing gender locally: The importance of ‘place’ in understanding marginalised masculinities and young men’s transitions to ‘safe’ and successful futures

Observable anxieties have been developing about the position of boys and young men in contemporary society in recent years. This is expressed as a crisis of masculinity, in which place is often implicitly implicated, but is rarely considered for its role in the shaping of young men’s practices, trajectories and aspirations. Drawing on research conducted with young people who accessed a range of social care support services, this article argues that transition means different things for young men in different locales and that local definitions of masculinity are required to better understand young men’s lives and the opportunities available to them. The authors argue that home life, street life, individual neighbourhoods, regions and nations all shaped the young men’s identities and the practices they (and the staff working with them) drew on in order to create successful futures and ‘safe’ forms of masculinity. It is suggested that this place-based approach has the potential to re-shape the ‘crisis’ discourse surrounding masculinity and the anxieties associated with young men

The spin-1/2 XXZ Heisenberg chain, the quantum algebra U_q[sl(2)], and duality transformations for minimal models

The finite-size scaling spectra of the spin-1/2 XXZ Heisenberg chain with toroidal boundary conditions and an even number of sites provide a projection mechanism yielding the spectra of models with a central charge c<1 including the unitary and non-unitary minimal series. Taking into account the half-integer angular momentum sectors - which correspond to chains with an odd number of sites - in many cases leads to new spinor operators appearing in the projected systems. These new sectors in the XXZ chain correspond to a new type of frustration lines in the projected minimal models. The corresponding new boundary conditions in the Hamiltonian limit are investigated for the Ising model and the 3-state Potts model and are shown to be related to duality transformations which are an additional symmetry at their self-dual critical point. By different ways of projecting systems we find models with the same central charge sharing the same operator content and modular invariant partition function which however differ in the distribution of operators into sectors and hence in the physical meaning of the operators involved. Related to the projection mechanism in the continuum there are remarkable symmetry properties of the finite XXZ chain. The observed degeneracies in the energy and momentum spectra are shown to be the consequence of intertwining relations involving U_q[sl(2)] quantum algebra transformations.Comment: This is a preprint version (37 pages, LaTeX) of an article published back in 1993. It has been made available here because there has been recent interest in conformal twisted boundary conditions. The "duality-twisted" boundary conditions discussed in this paper are particular examples of such boundary conditions for quantum spin chains, so there might be some renewed interest in these result

A sufficient criterion for integrability of stochastic many-body dynamics and quantum spin chains

We propose a dynamical matrix product ansatz describing the stochastic dynamics of two species of particles with excluded-volume interaction and the quantum mechanics of the associated quantum spin chains respectively. Analyzing consistency of the time-dependent algebra which is obtained from the action of the corresponding Markov generator, we obtain sufficient conditions on the hopping rates for identifing the integrable models. From the dynamical algebra we construct the quadratic algebra of Zamolodchikov type, associativity of which is a Yang Baxter equation. The Bethe ansatz equations for the spectra are obtained directly from the dynamical matrix product ansatz.Comment: 19 pages Late