We report the construction of a linkage map of the human genome, based on the pattern of inheritance of 403 polymorphic loci, including 393 RFLPs, in a panel of DNAs from 21 three-generation families. By a combination of mathematical linkage analysis and physical localization of selected clones, it was possible to arrange these loci into linkage groups representing 23 human chromosomes. We estimate that the linkage map is detectably linked to at least 95% of the DNA in the human genome.
Clovers are a new mechanism for object-oriented languages that relax the constraints of the conventional type/instance distinction. Clovers provide a new definition of object-hood, in which a single object may consist of multiple overlapping representations, sharing aspects of both behavior and identity. We show how clovers can be used to implement multiple views, changes to the type of an object, and expanded type notions such as minimal template. We argue that Clovers provide a useful unification of the type/instance relaxations that have been presented in the literature, such as versioning, prototypes, and boolean classes.
To identify the chromosomal location of a gene responsible for familial hypertrophic cardiomyopathy, we used clinical and molecular genetic techniques to evaluate the members of a large kindred. Twenty surviving and 24 deceased family members had hypertrophic cardiomyopathy; 58 surviving members were unaffected. Genetic-linkage analyses were performed with polymorphic DNA loci dispersed throughout the entire genome, to identify a locus that was inherited with hypertrophic cardiomyopathy in family members. The significance of the linkage detected between the disease locus and polymorphic loci was assessed by calculating a lod score (the logarithm of the probability of observing coinheritance of two loci, assuming that they are genetically linked, divided by the probability of detecting coinheritance if they are unlinked). A DNA locus (D14S26), previously mapped to chromosome 14 and of unknown function, was found to be coinherited with the disease in this family. No instances of recombination were observed between the locus for familial hypertrophic cardiomyopathy and D14S26, yielding a lod score of +9.37 (θ= 0). These data indicate that in this kindred, the odds are greater than 2,000,000,000:1 that the gene responsible for familial hypertrophic cardiomyopathy is located on chromosome 14 (band q1).
The genetic locus for neurofibromatosis 1 (NF1) has recently been mapped to the pericentromeric region of chromosome 17. We have genotyped eight previously identified RFLP probes on 50 NF1 families to determine the placement of the NF1 locus relative to the RFLP loci. Thirty-eight recombination events in the pericentromeric region were identified, eight involving crossovers between NF1 and loci on either chromosomal arm. Multipoint linkage analysis resulted in the unique placement of six loci at odds greater than 100:1 in the order of pter-A10-41-EW301-NF1-EW207-CRI-L581-CRI-L946 -qter. Owing to insufficient crossovers, three loci--D17Z1, EW206, and EW203--could not be uniquely localized. In this region female recombination rates were significantly higher than those of males. These data were part of a joint study aimed at the localization of both NF1 and tightly linked pericentromeric markers for chromosome 17.
We used molecular genetic techniques and multipoint linkage analyses to locate the gene responsible for cutaneous malignant melanoma-dysplastic nevus. We evaluated 99 relatives and 26 spouses in six families with a predisposition to melanoma. Thirty-four family members had cutaneous malignant melanoma, and 31 of these 34 also had histologically confirmed dysplastic nevi. Twenty-four family members had dysplastic nevi alone. An analysis of the cosegregation of the cutaneous malignant melanoma–dysplastic nevus trait with 26 polymorphic DNA markers on the short arm of chromosome 1 demonstrated the presence of a gene for susceptibility to melanoma. The gene was located between an anonymous DNA marker (D1S47) and the gene locus for pronatrodilatin, a commonly used reference gene (PND), in chromosome band 1p36. The odds were greater than 260,000:1 in favor of linkage at this location.
The use of DNA markers known as restriction fragment length polymorphisms is a sensitive and informative method of distinguishing patient and allogeneic donor cells after bone marrow transplantation. To apply the test, it is necessary in each case to find DNA probes that display patient-specific and donor-specific bands in Southern transfer hybridization. We have isolated a set of 12 cloned DNAs from highly polymorphic loci by which siblings can usually be distinguished. With just four of these probes, we can expect to distinguish the genotypes of the recipient and a sibling donor in more than 99% of cases (except between identical twins). The availability of many highly polymorphic probes also allows selection of an optimal probe for each case, one that can detect both the patient and donor-specific bands in a single hybridization with maximum resolution and sensitivity. We have applied these probes to the analysis of cells from peripheral blood and bone marrow after transplantation and demonstrated their usefulness in confirming engraftment of donor cells or graft rejection, and in detecting mixed lympho-hematopoietic chimerism.
Ideally skeptical inheritance supports exactly those inferences true in every credulous extension of an inheritance hierarchy. We provide a formal definition of ideally skeptical inheritance. We show that two path-based approaches fail to capture ideally skeptical inheritance, and that there are inheritance hierarchies for which there are more always-true inferences than always-supported paths. We describe an ATMS-like scheme that computes ideally skeptical inheritance and represents hierarchical dependencies using a limited form of Boolean satisfiability. Finally, we demonstrate a preemption (specificity) strategy for which ideally skeptical inheritance is polynomial time computable.
Although cystic fibrosis (CF) is among the most common inherited diseases in Caucasian populations, the basic biochemical defect is not yet known. CF is inherited as an autosomal recessive trait apparently due to mutations in a single gene, whence the efforts made to identify the genetic locus responsible by linkage studies. Two markers have recently been identified that are genetically linked to CF: one is a genetic variation in serum level of activity of the enzyme paraoxonase, and the other is a restriction fragment length polymorphism (RFLP) identified with a randomly isolated DNA probe. We report here that the genetic locus DOCRI-917 defined by the cloned DNA probe is located on chromosome 7.
Despite the rapid growth in the adoption of distance education, and asynchronous learning networks in particular, there is a dearth of detailed information on effective business models, business strategies and effective practices on which to build sustainable online education programs. What has been published on the business side of online education tends to focus on the costs and economic models, the growing for-profit sector, and new organizational approaches such as spin-offs and virtual university consortia. There are very few detailed, descriptive studies focused on the business models, strategies and effective practices of online education in U.S. degree-granting institutions.
We consider the evolution of a thin viscous fluid sheet subject to thermocapillary effects. Using a lubrication approximation we find, for symmetric interfacial deflections, coupled evolution equations for the interfacial profile, the streamwise component of the fluid velocity and the temperature variation along the surface. Initial temperature profiles change the initial flow field through Marangoni-induced shear stresses. These changes then lead to preferred conditions for rupture prescribed by the initial temperature distribution. We show that the time to rupture may be minimized by varying the phase difference between the initial velocity profile and the initial temperature profile. For sufficiently large temperature differences, the phase difference between the initial velocity and temperature profiles determines the rupture location.
To date, many processes have been used for the preparation of ionic polymer-metal composite (IPMC) artificial muscle membranes from conductive metals and perfluorosulfonic polymers such as Nafion. The most widely used of these methods is the platinum plating process, which involves chemical reduction of ionic salt solutions. Although these chemical electroding techniques produce IPMCs with outstanding surface electrodes and excellent performance characteristics, they are relatively costly and time-consuming. In this paper, we describe a novel fabrication process for fast preparation of low-cost Ni-Au-Nafion IPMCs. The process involves the formation of an adherent surface layer on prepared Nafion through DC sputter deposition of a fine-grained gold film, followed by electroplating of a thin and ductile nickel layer in a solution of aqueous nickel salts and boric acid. Preliminary results indicate that the Nafion-117-based IPMCs produced using this technique exhibit good surface conductivity and promising actuation performance, with 20 mg, 11.5 mm × 4.7 mm cantilever bending samples showing high displacements and tip forces up to 4 grams at 4 V. Our current research efforts are focused on achieving repeatable synthesis techniques and evaluating the properties and performance characteristics of the Au-Ni-Nafion IPMCs, especially in comparison to the popular platinum IPMCs.
Colloidal silica gels are shown to stiffen with time, as demonstrated by both dynamic light scattering and bulk rheological measurements. Their elastic moduli increase as a power law with time, independent of particle volume fraction; however, static light scattering indicates that there are no large-scale structural changes. We propose that increases in local elasticity arising from bonding between neighboring colloidal particles can account for the strengthening of the network, while preserving network structure.
Because an adequate blood supply to and within tissues is an essential factor for successful tissue regeneration, promoting a functional microvasculature is a crucial factor for biomaterials. In this study, we demonstrate that short self-assembling peptides form scaffolds that provide an angiogenic environment promoting long-term cell survival and capillary-like network formation in three-dimensional cultures of human microvascular endothelial cells. Our data show that, in contrast to collagen type I, the peptide scaffold inhibits endothelial cell apoptosis in the absence of added angiogenic factors, accompanied by enhanced gene expression of the angiogenic factor VEGF. In addition, our results suggest that the process of capillary-like network formation and the size and spatial organization of cell networks may be controlled through manipulation of the scaffold properties, with a more rigid scaffold promoting extended structures with a larger inter-structure distance, as compared with more dense structures of smaller size observed in a more compliant scaffold. These findings indicate that self-assembling peptide scaffolds have potential for engineering vascularized tissues with control over angiogenic processes. Since these peptides can be modified in many ways, they may be uniquely valuable in regeneration of vascularized tissues.
We find an asymptotic expression for the average signal to interference ratio (SIR) between a transmitter with a single isotropic antenna and a multi-antenna linear receiver in the presence of interferers with single isotropic transmit antennas distributed uniformly on an infinite plane. The channels are modeled as complex Gaussian random variables with average received power dependent on the distance separating nodes. We find that in large networks, the average SIR for a representative link depends primarily on the ratio of the number of receive antenna elements to the area density of interferers. Furthermore for our network model, the SIR grows super-linearly with the number of antenna elements. We also derive an approximate expression for the average capacity of the link when residual interference is treated as noise under certain conditions. We show via Monte-Carlo simulations that the asymptotic results are useful approximations to systems with finite parameters.
Laser hammering (LH) is a process used in the manufacturing of butterfly optoelectronic packages to correct laser-to-fiber misalignment that occurs when the semiconductor lasers are welded in place. High-power, precisely positioned pulsed lasers are used in LH to induce deformation of the fiber support housing to, in turn, induce realignment. A thermomechanical modeling study of LH is reported in this paper, which focuses on the degree to which a steady-state model can predict the asymptotic state of a transient response subjected to a periodic laser excitation. A baseline, two-dimensional fiber mounting/ferrule geometry is employed in a finite element analysis simulation case study. Various laser wave forms are applied to focus spot location sizes of 50 and 200 μ;m over a range of applied heat fluxes (10–1000 ;W/;mm2). Effects of laser energy deposition location, as well as the use of multiple lasers, are also studied. The results show that the steady-state solution is in good agreement with the asymptotic transient response for horizontal fiber displacement and fiber temperature. The laser focus spot surface temperature predictions are also found to be in reasonable agreement. However, the vertical fiber displacement tends to be overpredicted by the steady-state solution, sometimes by as much as an order of magnitude. The causes, both physical and computational, of this disagreement are discussed.
We consider the countercurrent flow of two incompressible immiscible viscous fluids in an inclined channel. This configuration may lead to the phenomena of ‘flooding’, i.e. the transition from a countercurrent regime to a cocurrent regime. This transition is marked by a variety of transient behaviour, such as the development of largeamplitude waves that impede the flow of one of the fluids to the reversal of the flow of the denser fluid. From a lubrication approximation based on the ratio of the channel height to the downstream disturbance wavelength, we derive a nonlinear system of evolution equations that govern the interfacial shape separating the two fluids and the leading-order pressure. This system, which assumes fluids with disparate density and dynamic viscosity ratios, includes the effects of viscosity stratification, inertia, shear and capillarity. Since the experimental constraints for this effective system are unclear, we consider two ways to drive the flow: either by fixing the volumetric flow rate of the gas phase or by fixing the total pressure drop over a downstream length of the channel. The latter forcing results in a single evolution equation whose dynamics depends non-locally on the interfacial shape. From both of these driven systems, admissible criteria for Lax shocks, undercompressive shocks and rarefaction waves are investigated. These criteria, through a numerical verification, do not depend significantly on the inertial effects within the more dense layer. The choice of the local/nonlocal constraints appears to play a role in the transient growth of undercompressive shocks, and may relate to the phenomena observed near the onset of flooding.
Areas hit by the tsunami in South and Southeast Asia need solar power for a broad range of applications, including water pumping and purification, lighting and vaccine refrigeration in medical clinics, and lighting in the thousands of homes that need to be rebuilt. Given my personal conviction that anthropologists have an ethical obligation to work on the behalf of the communities where they do research, I'm helping to bring solar power to Sri Lankan communities affected by the tsunami.
The emergence of worldwide communications networks and powerful computer technologies has redefined the concept of distance learning and the delivery of engineering education content. This article discusses the Sloan Consortium’s quest for quality, scale, and breadth in online learning, the impact on both continuing education of graduate engineers as well as degree-seeking engineering students, and the future of engineering colleges and schools as worldwide providers of engineering education.
The rapid improvement in performance and increased density of electronic devices in integrated circuits has provided a strong motivation for the development of contactless testing and diagnostic measurement methods. This paper first reviews existing contactless test methodologies and then compares these with an all-silicon contactless testing approach that has been recently developed and demonstrated. This cost-effective approach utilizes silicon-generated optical signals and has the advantages of easy test setup, low equipment cost, and noninvasiveness over existing contactless test and measurement methods.
Agonistic contests between lobsters housed together in a confined space progress through encounters of increasing intensity until a dominance relationship is established. Once this relationship is established, losing animals continually retreat from the advances of winners. 2. These encounters are likely to consume much energy in both winning and losing animals. Therefore, one might expect involvement of many physiological systems before, during and after fights. Here, we report effects of agonistic encounters on cardiac frequency in winning and losing adult lobsters involved in dyadic interactions. 3. The results show that: (i) small but significant increases in heart rate are observed upon chemical detection of a conspecific; (ii) during agonistic interactions, further increases in heart rate are seen; and (iii) ultimate winners exhibit greater increases in heart rate lasting longer periods of time compared to ultimate losers. Heart rate in winners remains elevated for at least 15 min after the contests have ended and animals have been returned to their home tanks. Reduced effects are seen in second and third pairings between familiar opponents. 4. The sustained changes in heart rate that we observe in winning lobsters may result from hormonal modulation of cardiac function related to the change in social status brought about by contest outcome.
We introduce a construction technique for generalized complex linear processing orthogonal designs, which are p × n matrices X satisfying XHX = fI, where f is a complex quadratic form, I is the identity matrix, and Xhas complex entries. These matrices generalize the familiar notions of orthogonal designs and generalized complex orthogonal designs. We explain the application of these matrices to space–time block coding for multiple-antenna wireless communications. In particular, we discuss the practical strengths of the space–time block codes constructed via our proposed technique.
We present a Chandra observation of the supernova remnant (SNR) 3C 397 (G41.1-0.3) obtained with the Advanced CCD Imaging Spectrometer (ACIS-S). Previous studies of this SNR have shown that the remnant harbors a central X-ray "hot spot'' suggestive of a compact object associated with 3C 397. With the Chandra data, we can rule out the nature of the hot spot as a pulsar or a pulsar wind nebula and put an upper limit on the flux of a hidden compact object of F-X(0.5-10 keV) similar to6 x 10(13) ergs cm(-2) s(-1). We found two point sources in the observed Chandra field. We argue that neither of them is associated with 3C 397 and that the hard source, CXO J190741.2+070650, which is characterized by a heavily absorbed spectrum with a strong Fe line, is a newly discovered active galactic nucleus. The Chandra image reveals arcsecond-scale clumps and knots that are strongly correlated with the radio VLA image, except for the X-ray hot spot. Our Chandra spatially resolved spectroscopic study shows that one-component models are inadequate and that at least two nonequilibrium ionization thermal components are needed to fit the spectra of each selected region. The derived average spectral parameters are consistent with the previous global ASCA fits performed by Safi-Harb and coworkers. However, the hard component requires a high abundance of Fe indicating the presence of hot Fe ejecta. When comparing the eastern with the western lobe, we find that the column density, the brightness, and the ionization timescales are generally higher for the western side. This result, combined with our study of the 3C 397 environs at millimeter wavelengths, indicates a denser medium to the west of the SNR. Our multiwavelength imaging and spectral study favors the scenario in which 3C 397 is a similar to5300 year old SNR expanding in a medium with a marked density gradient and is likely to be encountering a molecular cloud on the western side. We propose that 3C 397 will evolve into a mixed-morphology SNR.
What are the key business issues institutions are trying to solve in sustaining and growing their online programs? What “value-adding” attributes of online education are as perceived not just by individual learners but more generally by customers and markets? These are some of the topics explored in the report “Business Issues in Online Education” (forthcoming in Elements of Quality Online Education: Engaging Communities, Volume 6 in the Sloan-C series) funded by a grant from the Alfred P. Sloan Foundation, and based on my conversations this past year with over 50 interviewees at 25 online programs at eleven prominent not-for-profit higher learning institutions.
An important class of electrokinetic, microfluidic devices aims to pump and control electrolyte working liquids that have spatial gradients in conductivity. These high-gradient flows can become unstable under the application of a sufficiently strong electric field. In many of these designs, flow channels are thin in the direction orthogonal to the main flow and the conductivity gradient. Viscous stresses due to the presence of these walls introduce a stabilizing force that plays a major role in determining the overall instability. A thin channel model for fluid flow is developed and shown to provide good agreement with a complete three-dimensional model for channel aspect ratios less than or similar to 0.1.
The paper contributes a general dynamical formulation and numerical solution procedure for studying nonlinear and three-dimensional dynamics of Kirchhoffrods. Target applications include the dynamic formation of DNA loops and supercoils as well as loops (hockles) in marine cables. The formulation accommodates non-homogeneous and non-isotropic inextensible rods both with and without coupling of tension and torsion. The utility of this formulation is illustrated by studying the dynamics and quasi-static response of a clamped–clamped rod subject to compression and/or twist. For slow loading rates, the computed quasi-static responses converge to published equilibrium solutions for a benchmark problem. As loading rates increase, new behaviors are observed including hysteresis in the neighborhood of equilibrium bifurcations. The addition of chirality in the form of tension–torsion coupling has a pronounced influence on the computed looped geometries. This finding has implications for DNAloops formed by DNA–protein binding as well as loop formation in helically wound wire and synthetic cables.
The low-temperature magnetic excitations of the two-dimensional spin-5/2 square-lattice Heisenberg antiferromagnet Rb2MnF4 have been probed using pulsed inelastic neutron scattering. In addition to dominant sharp peaks identified with one-magnon excitations, a relatively weak continuum scattering is also observed at higher energies. This is attributed to neutron scattering by pairs of magnons and the observed intensities are consistent with predictions of spin wave theory.
The performance of single-hop links in ad-hoc wireless systems using direct-sequence (DS) code-division-multiple-access (CDMA) with random signature sequences and linear minimum-mean-square-error (MMSE) receivers is investigated. Expressions for the average signal-to-interference-plus-noise-ratio (SINR) and spectral efficiency (b s-1 Hz-1 link-1) were derived for a representative link in the presence of interferers distributed randomly on a plane with uniform area density p interferers m-2. Nodes transmit with equal power P, which decays with distance r as r-alpha. An expression for the optimum spreading factor given system parameters is also provided. It is found that for a given link length r, the average spectral efficiency when operating with the optimum spreading factor is approximately inversely proportional to pipr2. The corresponding spectral efficiency is proportional to pipr2. The parameter pipr2 can be interpreted as approximately the average number of interferers closer to the receiver than the desired transmitting node
In situ fluid film pressure and interfacial friction measurements during chemical mechanical planarization (CMP) are reported over a range of applied loads (27.6-41.4 kPA or 4-6 psi) and relative pad/wafer velocities . The slurry film pressure beneath contoured test wafers was measured using a novel experimental setup that enables dynamic data collection. The friction data have a repeatability of . The uncertainty of the pressure measurements and the computed down forces were and 20%, respectively. The data indicate that wafer shape, specifically global curvature, is a significant factor in determining the lubrication regime during CMP. Full hydrodynamic lubrication, in which the slurry fluid film supports the entire applied load, was not realized for either concave (center high) or convex (center low) wafers. The data for concave wafers show that to 37% of the applied load is supported by the slurry film, where the negative sign indicates suction conditions that were obtained at the lowest applied load condition. CMP of convex wafers is found to operate closer to full hydrodynamic lubrication, with the fluid layer supporting 36% to 64% of the applied downforce. In all cases, the measured friction coefficient decreased as the support of the fluid layer increased (higher positive pressures). CMP of concave wafers is more sensitive to changes in applied downforce, while the convex wafer type was most affected by changes in the wafer/pad rotation speed, which in turn determines effective slurry film velocity beneath the wafer. Overall, the CMP conditions seen in these scaled experiments operate primarily in the partial lubrication regime shifting closer to hydrodynamic lubrication for convex wafers at the high load, high speed conditions.
This paper is based on the premises that the purpose of engineering education is to graduate engineers who can design, and that design thinking is complex. The paper begins by briefly reviewing the history and role of design in the engineering curriculum. Several dimensions of design thinking are then detailed, explaining why design is hard to learn and harder still to teach, and outlining the research available on how well design thinking skills are learned. The currently most-favored pedagogical model for teaching design, project-based learning (PBL), is explored next, along with available assessment data on its success. Two contexts for PBL are emphasized: first-year cornerstone courses and globally dispersed PBL courses. Finally, the paper lists some of the open research questions that must be answered to identify the best pedagogical practices of improving design learning, after which it closes by making recommendations for research aimed at enhancing design learning.
Numerous studies have reported long-tailed distributions for various network metrics, including file sizes, transfer times, and burst lengths. We review techniques for identifying long-tailed distributions based on a sample, propose a new technique, and apply these methods to datasets used in previous reports. We find that the evidence for long tails is inconsistent, and that lognormal and other non-long-tailed models are usually sufficient to characterize network metrics. We discuss the implications of this result for current explanations of self-similarity in network traffic.
A chaotic mapping provides a technique for generating musical variations of an original work. Thistechnique, based on the sensitivity of chaotic trajectories to initial conditions, produces changes inthe pitch sequence of a piece. A sequence of musical pitches $pi%, i.e., any piece ranging from Bach~or earlier! to contemporary music, is paired with the x-components $xi% of a Lorenz chaotictrajectory. Each pi is marked on the x axis at the point designated by its xi . In this way, the x axisbecomes a pitch axis configured according to the notes of the original composition. Then, a secondchaotic trajectory, whose initial condition differs from the first, is launched. Its x-componentstrigger pitches on the pitch axis ~via the mapping! that vary in sequence from the original work, thuscreating a variation. There are virtually an unlimited number of variations possible, many appealingto expert and nonexpert alike.
Many recent proposals to increase the resilience of the Web PKI against misbehaving CAs face significant obstacles to deployment.
These hurdles include (1) the requirement of drastic changes to the existing PKI players and their interactions, (2) the lack of signaling mechanisms to protect against downgrade attacks, (3) the lack of an incremental deployment strategy, and (4) the use of inflexible mechanisms that hinder recovery from misconfiguration or from the loss or compromise of private keys. As a result, few of these proposals have seen widespread deployment, despite their promise of a more secure Web PKI. To address these roadblocks, we propose Certificates with Automated Policies and Signaling (CAPS), a system that leverages the infrastructure of the existing Web PKI to overcome the aforementioned hurdles. CAPS offers a seamless and secure transition away from today’s insecure Web PKI and towards present and future proposals to improve the Web PKI. Crucially, with CAPS, domains can take simple steps to protect themselves from MITM attacks in the presence of one or more misbehaving CAs, and yet the interaction between domains and CAs remains fundamentally the same. We implement CAPS and show that it adds at most 5% to connection establishment latency.
We report a neutron-scattering study of the dynamic spin correlations in Rb2MnF4, a two-dimensional spin-5/2 antiferromagnet. By tuning an external magnetic field to the value for the spin-flop line, we reduce the effective spin anisotropy to essentially zero, thereby obtaining a nearly ideal two-dimensional isotropic antiferromagnet. From the shape of the quasielastic peak as a function of temperature, we demonstrate dynamic scaling for this system and find a value for the dynamical exponent z. We compare these results to theoretical predictions for the dynamic behavior of the two-dimensional Heisenberg model, in which deviations from z=1 provide a measure of the corrections to scaling.
Part of Focus on Micro- and Nanofluidics The classical theory of electrokinetic phenomena assumes a dilute solution of point-like ions in chemical equilibrium with a surface whose double-layer voltage is of order the thermal voltage, kBT/e=25 mV. In nonlinear 'induced-charge' electrokinetic phenomena, such as ac electro-osmosis, several volts 100kBT/e are applied to the double layer, and the theory breaks down and cannot explain many observed features. We argue that, under such a large voltage, counterions 'condense' near the surface, even for dilute bulk solutions. Based on simple models, we predict that the double-layer capacitance decreases and the electro-osmotic mobility saturates at large voltages, due to steric repulsion and increased viscosity of the condensed layer, respectively. The former suffices to explain observed high-frequency flow reversal in ac electro-osmosis; the latter leads to a salt concentration dependence of induced-charge flows comparable to experiments, although a complete theory is still lacking.
We present results of a systematic x-ray scattering study of the effects of Mg doping on the high-fieldincommensurate phase of CuGeO3. Lorentzian-squared line shapes, the changing of the first-order transition tosecond order, and the destruction of long-range order with infinitesimal doping are observed, consistent withrandom-field effects in a three-dimensional XY system. Values for the soliton width in pure and lightly dopedCuGeO3 are deduced. We find that even a very small doping has a drastic effect on the shape of the latticemodulation.
Enabled/vasodilator-stimulated phosphoprotein (Ena/VASP) proteins are key actin regulators that localize at regions of dynamic actin remodeling, including cellular protrusions and cell-cell and cell-matrix junctions. Several studies have suggested that Ena/VASP proteins are involved in the formation and function of cellular junctions. Here, we establish the importance of Ena/VASP in endothelial junctions in vivo by analysis of Ena/VASP-deficient animals. In the absence of Ena/VASP, the vasculature exhibits patterning defects and lacks structural integrity, leading to edema, hemorrhaging, and late stage embryonic lethality. In endothelial cells, we find that Ena/VASP activity is required for normal F-actin content, actomyosin contractility, and proper response to shear stress. These findings demonstrate that Ena/VASP is critical for actin cytoskeleton remodeling events involved in the maintenance of functional endothelia.
Colloidal silica gels are shown to stiffen with time, as demonstrated by both dynamic light scattering and bulk rheological measurements. Their elastic moduli increase as a power law with time, independent of particle volume fraction; however, static light scattering indicates that there are no large-scale structural changes. We propose that increases in local elasticity arising from bonding between neighboring colloidal particles can account for the strengthening of the network, while preserving network structure.
We show that the dynamics of large fractal colloid aggregates are well described by a combination of translational and rotational diffusion and internal elastic fluctuations, allowing both the aggregate size and internal elasticity to be determined by dynamic light scattering. The comparison of results obtained in microgravity and on Earth demonstrates that cluster growth is limited by gravity-induced restructuring. In the absence of gravity, thermal fluctuations ultimately inhibit fractal growth and set the fundamental limitation to the lowest volume fraction which will gel.
We used molecular genetic techniques and multipoint linkage analyses to locate the gene responsible for cutaneous malignant melanoma-dysplastic nevus. We evaluated 99 relatives and 26 spouses in six families with a predisposition to melanoma. Thirty-four family members had cutaneous malignant melanoma, and 31 of these 34 also had histologically confirmed dysplastic nevi. Twenty-four family members had dysplastic nevi alone. An analysis of the cosegregation of the cutaneous malignant melanoma–dysplastic nevus trait with 26 polymorphic DNA markers on the short arm of chromosome 1 demonstrated the presence of a gene for susceptibility to melanoma. The gene was located between an anonymous DNA marker (D1S47) and the gene locus for pronatrodilatin, a commonly used reference gene (PND), in chromosome band 1p36. The odds were greater than 260,000:1 in favor of linkage at this location.
One property of the emulator framework presented by Grush is that imagery operates off-line. Contrary to this viewpoint, we present evidence showing that mental rotation of a simple figure modulates low-level features of drawing articulation. This effect is dependent upon the type of rotation, suggesting a more integrative online role for imagery than proposed by the target article.
We study phase separation in a deeply quenched colloid-polymer mixture in microgravity on the International Space Station using small-angle light scattering and direct imaging. We observe a clear crossover from early-stage spinodal decomposition to late-stage, interfacial-tension-driven coarsening. Data acquired over 5 orders of magnitude in time show more than 3 orders of magnitude increase in domain size, following nearly the same evolution as that in binary liquid mixtures. The late-stage growth approaches the expected linear growth rate quite slowly.
The critical fluctuations of CuGeO3 have been measured by synchrotron x-ray scattering, and two length scales are clearly observed. The ratio between the two length scales is found to be significantly different along the a axis, with the a axis along the surface normal direction. We believe that such a directional preference is a clear sign that random surface strains, especially those caused by dislocations, are the origin of the long length scale fluctuations.
We report a neutron scattering study of the spin correlations for the spin-5/2 two-dimensional antiferromagnet Rb2MnF4 in an external magnetic field. Choosing fields near the system’s bicritical point, we tune the effective anisotropy in the spin interaction to zero, constructing an ideal S = 5/2 Heisenberg system. The correlation length and structure factor amplitude are closely described by the semiclassical theory of Cuccoli 'et al.' over a broad temperature range, but show no indication of approaching the low-temperature renormalized classical regime of the quantum nonlinear sigma model.
The low-temperature magnetic excitations of the two-dimensional spin- 52 square-lattice Heisenberg antiferromagnetRb2MnF4 have been probed using pulsed inelastic neutron scattering. In addition to dominant sharppeaks identified with one-magnon excitations, a relatively weak continuum scattering is also observed at higherenergies. This is attributed to neutron scattering by pairs of magnons and the observed intensities are consistentwith predictions of spin wave theory.
Measurements are reported of the time dependence of the current during electrochemical oxidation and reduction at a fixed voltage of single crystals and ceramic samples of La2CuO4+d. Staging peaks in neutron measurements of the single crystals together with the electrochemical measurements and magnetization measurements confirm that stage n=6 corresponds to d=0.055 +/- 0.05, the high-d side of the oxygen-rich–oxygen-poor miscibility gap. Furthermore, stage n=4 occurs at a value of d consistent with d { n^(-1). For ceramic samples it is shown that two different superconducting compounds are formed depending on the oxidation voltage used.
To identify the chromosomal location of a gene responsible for familial hypertrophic cardiomyopathy, we used clinical and molecular genetic techniques to evaluate the members of a large kindred. Twenty surviving and 24 deceased family members had hypertrophic cardiomyopathy; 58 surviving members were unaffected. Genetic-linkage analyses were performed with polymorphic DNA loci dispersed throughout the entire genome, to identify a locus that was inherited with hypertrophic cardiomyopathy in family members. The significance of the linkage detected between the disease locus and polymorphic loci was assessed by calculating a lod score (the logarithm of the probability of observing coinheritance of two loci, assuming that they are genetically linked, divided by the probability of detecting coinheritance if they are unlinked). A DNA locus (D14S26), previously mapped to chromosome 14 and of unknown function, was found to be coinherited with the disease in this family. No instances of recombination were observed between the locus for familial hypertrophic cardiomyopathy and D14S26, yielding a lod score of +9.37 (θ= 0). These data indicate that in this kindred, the odds are greater than 2,000,000,000:1 that the gene responsible for familial hypertrophic cardiomyopathy is located on chromosome 14 (band q1).
Cell-mediated compaction of the extracellular matrix (ECM) plays a critical role in tissue engineering, woundhealing, embryonic development, and many disease states. The ECM is compacted as a result of cellular traction forces. Wehypothesize that a cell mechanically remodels the nearby ECM until some target conditions are obtained, and then the cell stopscompacting. A key feature of this hypothesis is that ECM compaction primarily occurs in the pericellular region and the propertiesof the ECM in the pericellular region govern cellular force generation. We developed a mathematical model to describe theamount of macroscopic compaction of cell-populated collagen gels in terms of the initial cell and collagen densities, as wellas the final conditions of the pericellular environment (defined as the pericellular volume where the collagen is compacted(V) and the mass of collagen within this volume (m)). This model qualitatively predicts the effects of varying initial cell andcollagen concentrations on the extent of gel compaction, and by fitting V and m, provides reasonable quantitative agreementwith the extent of gel compaction observed in experiments with endothelial cells and fibroblasts. Microscopic analysis ofcompacted gels supports the assumption that collagen compaction occurs primarily in the pericellular environment.
In this paper, we consider what we identify as crisis surveillance capitalism in higher education, drawing on the work of Naomi Klein and Shoshana Zuboff. We define crisis surveillance capitalism as the intersection of unregulated and ubiquitous data collection with the continued marginalization of vulnerable racial and social groups. Through this lens, we examine the twinned crisis narratives of student success and academic integrity and consider how the COVID-19 pandemic further enabled so-called solutions that collect massive amounts of student data with impunity. We suggest a framework of refusal to crisis surveillance capitalism coming from the work of Keller Easterling and Baharak Yousefi, identifying ways to resist and build power in a context where the cause of harm is all around and intentionally hidden.
The emerging field of Public Interest Technology contains the seeds for an engineering practice that embodies the
ethic of care and undergraduate engineering educational experiences in the mold of liberatory education. We realized these opportunities by creating an undergraduate, student-led public interest technology clinic. Using autoethnography, we reflect on our effort to create the clinic and find that we prioritized emotions and relationships, embraced slowness and deliberation, and claimed student ownership. These practices served to redefine engineering in ways that center care and equity, helping us create the inclusive and effective engineering and public interest technology educational experiences we wanted for ourselves.