Human erythrocytes bearing electroinserted CD4 neutralize infection in vitro by primary isolates of human immunodeficiency virus type 1

Human erythrocytes bearing electroinserted full-length CD4 (RBC-CD4) can bind and fuse with a laboratory strain of human immunodeficiency virus type 1 (HIV-1) or with T cells infected by HIV-1. Here we show that RBC-CD4 neutralize primary HIV-1 strains in an assay of cocultivation of peripheral blood mononuclear cells (PBMC) from HIV-1-infected persons with uninfected PBMC. RBC-CD4 inhibited viral p24 core antigen accumulation in these cocultures up to 10,000-fold compared with RBC alone. Viral p24 accumulation was inhibited equally well when measured in culture supernatants or in call extracts. The inhibition was dose-dependent and long-lived. Two types of recombinant CD4 tested in parallel were largely ineffective. The neutralization of primary HIV-1 by RBC-CD4 in vitro was demonstrated in PBMC cultures from 21 of a total of 23 patients tested at two independent sites. RBC-CD4 may offer a route to blocking HIV-1 infection in vivo.     

Stability properties of slotted Aloha with multipacket receptioncapability

The stability of the Aloha random-access algorithm in an infinite-user slotted channel with multipacket-reception capability is considered. This channel is a generalization of the usual collision channel, in that it allows the correct reception of one or more packets involved in a collision. The number of successfully received packets in each slot is modeled as a random variable which depends exclusively on the number of simultaneously attempted transmissions. This general model includes as special cases channels with capture, noise, and code-division multiplexing. It is shown by drift analysis that the channel backlog Markov chain is ergodic if the packet-arrival rate is less than the expected number of packets successfully received in a collision of n as n goes to infinity. The properties of the backlog in the nonergodicity region are examined     

Bending and torsional fatigue of nylon 66 monofilaments

Using newly developed test equipment, the fatigue behavior of nylon 66 monofilaments was studied under two loading conditions, pure bending or simple torsion. For each mode, results are expressed in terms of the measured decay in stiffness with numbers of cycles over a range of maximum applied strain levels. Fatigue lifetimes are presented in S–N format where the log number of cycles of fatigue for a 40% decay in stiffness (N) is plotted as a function of applied strain (S). The failure mechanism for these fibers in each fatigue mode reflects the morphology of semicrystalline-oriented synthetic fibers. In torsion, many longitudinal cracks form around the perimeter of a fiber as the result of cleavage of the relatively weak interfibrillar bonds in nylon 66. In bending, cracks form within kink band boundaries and grow at an oblique angle to the fiber axis. © 1992 John Wiley & Sons, Inc.     

Opposite phenotypes of hypomorphic and Y766 phosphorylation site mutations reveal a function for Fgfr1 in anteroposterior patterning of mouse embryos

Intercellular communication is needed for both the generation of the mesodermal germ layer and its division into distinct subpopulations. To dissect the functions of fibroblast growth factor receptor-1 (FGFR1) during mouse gastrulation as well as to gain insights into its possible roles during later embryonic development, we have introduced specific mutations into the Fgfr1 locus by gene targeting. Our results show functional dominance of one of the receptor isoforms and suggest a function for the autophosphorylation of site Y766 in the negative regulation of FGFR1 activity. Y766F and hypomorphic mutations in Fgfr1 generate opposite phenotypes in terms of homeotic vertebral transformations, suggesting a role for FGFR1 in patterning the embryonic anteriorposterior axis by way of regulation of Hox gene activity.     

Keratoacanthoma

The keratoacanthoma is a common cutaneous neoplasm that most often occurs on sun-exposed sites in light-skinned persons of middle age or older. It is considered the prototype of cutaneous pseudo-malignancies because it is a rapidly growing tumor with a histologic pattern resembling squamous cell carcinoma. It may be best viewed as an aborted malignancy that only rarely progresses into an invasive squamous cell carcinoma. It is most likely derived from hair follicle cells. The common type of keratoacanthoma and its many variants are discussed with emphasis on clinical and histologic features, biologic behavior, and response to therapy.     

The Mona Lisa identification: Evidence from a computer analysis

A recent computer-aided study identified the model immortalized in Leonardo da Vinci's celebratedMona Lisa to be none other than the artist himself. A follow-up investigation empolying similar techniques identifies the subject of asecond HiddenMona Lisa by the same artist. Analysis of photographic and x-ray images indicates that Leonardo first created a sketch of Isabella, Duchess of Aragon, which he later painted over with theMona Lisa, using himself as the model.     

Electrodeposition of Fe−Ni−Co alloys part I: Direct current deposition

Effects of hydrodynamic conditions, current density and solution temperature on the d.c. electrodeposition of Fe–Ni–Co alloys have been investigated with stationary planar and rotating cylindrical electrodes. The deposition rate of Fe showed mass transfer effects at cathodic potentials –1.35 V/sce. Deposition of Ni appeared to be kinetically controlled; deposition of Co appeared to be under kinetic control at potentials –1.35 V/sce but under mixed control at –1.65 V. Current efficiency of the codeposition process increased with increasing current density and decreased with increasing rotation rate. Higher solution temperatures and rotation rates extended the applied current density range where smooth, adherent, and metallic-looking deposits could be obtained. An increase in solution temperatures also decreased anomalous codeposition of Fe–Ni–Co. Calculations based on the Hessami-Tobias model provide qualitative agreement with dependence of experimental electrodeposition on applied current density, hydrodynamics and temperature.     

Archival Appraisal and the Digital Record: Applying Past Tradition for Future Practice

The digital revolution has changed the daily work of archivists. As a result, archivists have refined their analog practices and initiated new ones to accommodate the unique information creation and access needs of users. While limitless storage and technological obsolescence may be surmountable challenges, appraisal continues to be a necessary component of this preservation enterprise. Macro-appraisal—a top-down functional assessment of an organization’s high-level decision making that defines the enduring value of specific bodies of documentary evidence of these creative or administrative processes—is used to facilitate the management of diverse bodies of born-digital records in archives and special collections.     

The Impact of Speculative Execution on SMT Processors

By executing two or more threads concurrently, Simultaneous MultiThreading (SMT) architectures are able to exploit both Instruction-Level Parallelism (ILP) and Thread-Level Parallelism (TLP) from the increased number of in-flight instructions that are fetched from multiple threads. However, due to incorrect control speculations, a significant number of these in-flight instructions are discarded from the pipelines of SMT processors (which is a direct consequence of these pipelines getting wider and deeper). Although increasing the accuracy of branch predictors may reduce the number of instructions so discarded from the pipelines, the prediction accuracy cannot be easily scaled up since aggressive branch prediction schemes strongly depend on the particular predictability inherently to the application programs. In this paper, we present an efficient thread scheduling mechanism for SMT processors, called SAFE-T (Speculation-Aware Front-End Throttling): it is easy to implement and allows an SMT processor to selectively perform speculative execution of threads according to the confidence level on branch predictions, hence preventing wrong-path instructions from being fetched. SAFE-T provides an average reduction of 57.9% in the number of discarded instructions and improves the instructions per cycle (IPC) performance by 14.7% on average over the ICOUNT policy across the multi-programmed workloads we simulate. This paper is an extended version of the paper, “Speculation Control for Simultaneous Multithreading,” which appeared in the Proceedings of the 18th International Parallel and Distributed Processing Symposium, Santa Fe, New Mexico, April 2004.