Durable and scalable icephobic surfaces: similarities and distinctions from superhydrophobic surfaces.

Formation, adhesion, and accumulation of ice, snow, frost, glaze, rime, or their mixtures can cause severe problems for solar panels, wind turbines, aircrafts, heat pumps, power lines, telecommunication equipment, and submarines. These problems can decrease efficiency in power generation, increase energy consumption, result in mechanical and/or electrical failure, and generate safety hazards. To address these issues, the fundamentals of interfaces between liquids and surfaces at low temperatures have been extensively studied. This has lead to development of so called "icephobic" surfaces, which possess a number of overlapping, yet distinctive, characteristics from superhydrophobic surfaces. Less attention has been given to distinguishing differences between formation and adhesion of ice, snow, glaze, rime, and frost or to developing a clear definition for icephobic, or more correctly pagophobic, surfaces. In this review, we strive to clarify these differences and distinctions, while providing a comprehensive definition of icephobicity. We classify different canonical families of icephobic (pagophobic) surfaces providing a review of those with potential for scalable and robust development.

Extensional flow of hyaluronic acid solutions in an optimized microfluidic cross-slot device.

We utilize a recently developed microfluidic device, the Optimized Shape Cross-slot Extensional Rheometer (OSCER), to study the elongational flow behavior and rheological properties of hyaluronic acid (HA) solutions representative of the synovial fluid (SF) found in the knee joint. The OSCER geometry is a stagnation point device that imposes a planar extensional flow with a homogenous extension rate over a significant length of the inlet and outlet channel axes. Due to the compressive nature of the flow generated along the inlet channels, and the planar elongational flow along the outlet channels, the flow field in the OSCER device can also be considered as representative of the flow field that arises between compressing articular cartilage layers of the knee joints during running or jumping movements. Full-field birefringence microscopy measurements demonstrate a high degree of localized macromolecular orientation along streamlines passing close to the stagnation point of the OSCER device, while micro-particle image velocimetry is used to quantify the flow kinematics. The stress-optical rule is used to assess the local extensional viscosity in the elongating fluid elements as a function of the measured deformation rate. The large limiting values of the dimensionless Trouton ratio, Tr ∼ O(50), demonstrate that these fluids are highly extensional-thickening, providing a clear mechanism for the load-dampening properties of SF. The results also indicate the potential for utilizing the OSCER in screening of physiological SF samples, which will lead to improved understanding of, and therapies for, disease progression in arthritis sufferers.

GOModeler--a tool for hypothesis-testing of functional genomics datasets.

BACKGROUND: Functional genomics technologies that measure genome expression at a global scale are accelerating biological knowledge discovery. Generating these high throughput datasets is relatively easy compared to the downstream functional modelling necessary for elucidating the molecular mechanisms that govern the biology under investigation. A number of publicly available 'discovery-based' computational tools use the computationally amenable Gene Ontology (GO) for hypothesis generation. However, there are few tools that support hypothesis-based testing using the GO and none that support testing with user defined hypothesis terms.Here, we present GOModeler, a tool that enables researchers to conduct hypothesis-based testing of high throughput datasets using the GO. GOModeler summarizes the overall effect of a user defined gene/protein differential expression dataset on specific GO hypothesis terms selected by the user to describe a biological experiment. The design of the tool allows the user to complement the functional information in the GO with his/her domain specific expertise for comprehensive hypothesis testing. RESULTS: GOModeler tests the relevance of the hypothesis terms chosen by the user for the input gene dataset by providing the individual effects of the genes on the hypothesis terms and the overall effect of the entire dataset on each of the hypothesis terms. It matches the GO identifiers (ids) of the genes with the GO ids of the hypothesis terms and parses the names of those ids that match to assign effects. We demonstrate the capabilities of GOModeler with a dataset of nine differentially expressed cytokine genes and compare the results to those obtained through manual analysis of the dataset by an immunologist. The direction of overall effects on all hypothesis terms except one was consistent with the results obtained by manual analysis. The tool's editing capability enables the user to augment the information extracted. GOModeler is available as a part of the AgBase tool suite (http://www.agbase.msstate.edu). CONCLUSIONS: GOModeler allows hypothesis driven analysis of high throughput datasets using the GO. Using this tool, researchers can quickly evaluate the overall effect of quantitative expression changes of gene set on specific biological processes of interest. The results are provided in both tabular and graphical formats.

Elastic turbulence in shear banding wormlike micelles.

We study the dynamics of the Taylor-Couette flow of shear banding wormlike micelles. We focus on the high shear rate branch of the flow curve and show that for sufficiently high Weissenberg numbers, this branch becomes unstable. This instability is strongly subcritical and is associated with a shear stress jump. We find that this increase of the flow resistance is related to the nucleation of turbulence. The flow pattern shows similarities with the elastic turbulence, so far only observed for polymer solutions. The unstable character of this branch led us to propose a scenario that could account for the recent observations of Taylor-like vortices during the shear banding flow of wormlike micelles.

From ultra-soft slime to hard {alpha}-keratins: The many lives of intermediate filaments.

Intermediate filaments are filaments 10 nm in diameter that make up an important component of the cytoskeleton in most metazoan taxa. They are most familiar for their role as the fibrous component of α-keratins such as skin, hair, nail, and horn but are also abundant within living cells. Although they are almost exclusively intracellular in their distribution, in the case of the defensive slime produced by hagfishes, they are secreted. This article surveys the impressive diversity of biomaterials that animals construct from intermediate filaments and will focus on the mechanisms by which the mechanical properties of these materials are achieved. Hagfish slime is a dilute network of hydrated mucus and compliant intermediate filament bundles with ultrasoft material properties. Within the cytoplasm of living cells, networks of intermediate filaments form soft gels whose elasticity arises via entropic mechanisms. Single intermediate filaments or bundles are also elastic, but substantially stiffer, exhibiting modulus values similar to that of rubber. Hard α-keratins like wool are stiffer still, an effect that is likely achieved via dehydration of the intermediate filaments in these epidermal appendages. The diverse mechanisms described here have been employed by animals to generate materials with stiffness values that span an impressive eleven orders of magnitude.

Ex vivo rheology of spider silk.

We investigate the rheological properties of microliter quantities of the spinning material extracted ex vivo from the major ampullate gland of a Nephila clavipes spider using two new micro-rheometric devices. A sliding plate micro-rheometer is employed to measure the steady-state shear viscosity of approximately 1 microl samples of silk dope from individual biological specimens. The steady shear viscosity of the spinning solution is found to be highly shear-thinning, with a power-law index consistent with values expected for liquid crystalline solutions. Calculations show that the viscosity of the fluid decreases 10-fold as it flows through the narrow spinning canals of the spider. By contrast, measurements in a microcapillary extensional rheometer show that the transient extensional viscosity (i.e. the viscoelastic resistance to stretching) of the spinning fluid increases more than 100-fold during the spinning process. Quantifying the properties of native spinning solutions provides new guidance for adjusting the spinning processes of synthetic or genetically engineered silks to match those of the spider.

Use and efficacy of tuberculosis infection control practices at hospitals with previous outbreaks of multidrug-resistant tuberculosis.

OBJECTIVE: To evaluate the implementation and efficacy of selected Centers for Disease Control and Prevention guidelines for preventing spread of Mycobacterium tuberculosis. DESIGN: Analysis of prospective observational data. SETTING: Two medical centers where outbreaks of multidrug-resistant tuberculosis (TB) had occurred. PARTICIPANTS: All hospital inpatients who had active TB or who were placed in TB isolation and healthcare workers who were assigned to selected wards on which TB patients were treated. METHODS: During 1995 to 1997, study personnel prospectively recorded information on patients who had TB or were in TB isolation, performed observations of TB isolation rooms, and recorded tuberculin skin-test results of healthcare workers. Genetic typing of M tuberculosis isolates was performed by restriction fragment-length polymorphism analysis. RESULTS: We found that only 8.6% of patients placed in TB isolation proved to have TB; yet, 19% of patients with pulmonary TB were not isolated on the first day of hospital admission. Specimens were ordered for acid-fast bacillus smear and results received promptly, and most TB isolation rooms were under negative pressure. Among persons entering TB isolation rooms, 44.2% to 97.1% used an appropriate (particulate, high-efficiency particulate air or N95) respirator, depending on the hospital and year; others entering the rooms used a surgical mask or nothing. We did not find evidence of transmission of TB among healthcare workers (based on tuberculin skin-test results) or patients (based on epidemiological investigation and genetic typing). CONCLUSIONS: We found problems in implementation of some TB infection control measures, but no evidence of healthcare-associated transmission, possibly in part because of limitations in the number of patients and workers studied. Similar evaluations should be performed at hospitals treating TB patients to find inadequacies and guide improvements in infection control.

Shear-induced degradation of linear polyacrylamide solutions during pre-electrophoretic loading.

Electrophoretic channels are filled with a polymer matrix prior to their use in DNA separations. This process, called gel-loading, can be accomplished manually, using syringes, or can be automated through the use of small pumps or vacuum. The injection rate is constrained by the desire to minimize shear-induced degradation of the polymer molecules. Currently, the community lacks quantitative data with which to gauge the range of flow rates that prevent polymer degradation. In this study, measurements of the zero shear rate viscosity of linear polyacrylamide (LPA) solutions are used to determine the LPA molecular weight before and after gel-loading. The results indicate molecular degradation in polymer solutions even when injected at minimal flow rates of 1 microL/min. To correlate these rheological observations of shear-induced degradation with subsequent electrophoretic performance, the degraded solutions were used as sieving matrixes for DNA sequencing analysis. The decreases in electrophoretic resolution and increases in peak widths between sheared and nonsheared LPA solutions are related to the degradation in molecular weight experienced by the polymer solutions.

Randomized, controlled study of the safety and efficacy of intravenous cidofovir for the treatment of relapsing cytomegalovirus retinitis in patients with AIDS.

To assess the effect of intravenous cidofovir on delaying progression of previously treated, relapsing cytomegalovirus (CMV) retinitis, we conducted a randomized, controlled comparison of two maintenance dose levels of cidofovir. One hundred and fifty patients with AIDS and CMV retinitis that had progressed or was persistently active despite treatment with ganciclovir, foscarnet, or both were randomized to receive induction cidofovir, 5 mg/kg once weekly for 2 weeks, then maintenance therapy with either 5 mg/kg or 3 mg/kg once every other week. Concomitant probenecid and intravenous hydration were administered with each cidofovir dose. Retinitis progression was assessed in the first 100 patients by bilateral, full-field retinal photographs read at a central reading center by an ophthalmologist masked to treatment assignment. Incidence of side effects, changes in visual acuity, and mortality were also assessed. Median time to retinitis progression as assessed by retinal photography was not reached (95% confidence interval [CI], 115 days-upper limit not reached) in the 5-mg/kg group, and was 49 days (95% CI, 35-52 days) in the 3-mg/kg group (p = .0006). Dose-dependent asymptomatic proteinuria (39%) and serum creatinine elevation (24%) were the most common adverse events thought to be related to cidofovir. Reversible probenecid reactions including constitutional symptoms and nausea occurred in 65 of 150 (43%) patients. Cidofovir therapy is effective in delaying progression of CMV retinitis that had previously progressed using other anti-CMV therapies.

Improvement of Herpesvirus saimiri T cell immortalization procedure to generate multiple CD4+ T-cell clones from peripheral blood lymphocytes of AIDS patients.

Herpesvirus saimiri (HVS) can infect and immortalize human T lymphocytes of both CD4- and CD8-positive phenotypes. We have previously shown that infection of peripheral blood lymphocytes (PBL) from AIDS patients with HVS predominantly yielded immortalized CD8-positive T cell clones. Here we show that CD4-positive T cells from AIDS patients can be efficiently immortalized by HVS if patient PBL are enriched for CD4-positive T cell subpopulation prior to HVS infection. Such cells can be cloned and maintained in culture for prolonged times, and they exhibit activated T cell phenotype of Th1 class and are susceptible to HIV-1 infection. Several immortalized T cell clones obtained from one out of three AIDS patients tested here were HIV-1 positive and produced infectious virus. This approach permits efficient generation of multiple CD4-positive T cell clones from AIDS patients for functional and virological studies.

Peptide T in the treatment of painful distal neuropathy associated with AIDS: results of a placebo-controlled trial. The Peptide T Neuropathy Study Group.

OBJECTIVE: To assess the safety and efficacy of Peptide T in the treatment of painful distal symmetrical polyneuropathy (DSP) associated with human immunodeficiency virus (HIV) infection. BACKGROUND: Painful DSP is a frequent complication of HIV infection, although its etiology and optimal treatment are unknown. Peptide T (D-(alpha 1)-Peptide T-amide) has been found in phase I trials and anecdotal reports to relieve neuropathic pain in AIDS patients. DESIGN/METHODS: In this multicentered, double-blind, randomized study, subjects received intranasal Peptide T 6 mg/day or placebo for 12 weeks. The primary outcome measure was change in the modified Gracely pain score. Secondary efficacy variables were results of neurologic examination, neuropsychological and electrophysiologic studies, global evaluation, and CD4 lymphocyte counts. RESULTS: Of 81 evaluable subjects, 40 received Peptide T and 41 received placebo. The change in pain scores was not significantly different (p = 0.32) in the Peptide T group (-0.24) as compared to placebo (-0.39). Group comparisons were not significantly different for change in any clinical examination or neuropsychologic measure, sural nerve amplitude or conduction velocity, or CD4 lymphocyte count. No significant drug-related adverse effects occurred in either group. CONCLUSION: Intranasal Peptide T is safe but ineffective in the treatment of painful DSP associated with AIDS.

Oral ganciclovir for the prevention of cytomegalovirus disease in persons with AIDS. Roche Cooperative Oral Ganciclovir Study Group.

BACKGROUND: In the advanced stages of the acquired immunodeficiency syndrome (AIDS), cytomegalovirus (CMV) disease, particularly vision-damaging retinitis due to CMV is common. We evaluated prophylactic treatment with orally administered ganciclovir as a way to prevent CMV disease. METHODS: We conducted a prospective, randomized, double-blind, placebo-controlled study of CMV infected persons with AIDS with either CD4+ lymphocyte counts of < or = 50 per cubic millimeter or counts of < or = 100 per cubic millimeter in those with a history of an AIDS defining opportunistic infection. Patients were randomly assigned, in a 2:1 ratio, to receive either oral ganciclovir (1000 mg three times daily) or placebo. RESULTS: The study was stopped after a median 367 days of follow-up. In an intention-to-treat analysis, the twelve month cumulative rates of confirmed CMV disease were 26 percent in the placebo group (n = 239) and 14 percent in the ganciclovir group (n = 486), representing an overall reduction in risk of 49 percent in the ganciclovir group (P < 0.001). The incidence of CMV retinitis after 12 months was 24 percent in the placebo group and 12 percent in the ganciclovir group (P < 0.0001). The prevalence of CMV-positive urine cultures at base line was 42 percent; after two months it was 43 percent in the placebo group and 10 percent in the ganciclovir group (P < 0.0001). The one year mortality rate was 26 percent in the placebo group and 21 percent in the ganciclovir group (P = 0.14). Therapy with granulocyte colony stimulating factor was more frequent in the ganciclovir group (24 percent) than in the placebo group (9 percent). CONCLUSIONS: In persons with advanced AIDS, phophylactic oral ganciclovir significantly reduces the risk of CMV disease.

Pilot study of topical trifluridine for the treatment of acyclovir-resistant mucocutaneous herpes simplex disease in patients with AIDS (ACTG 172). AIDS Clinical Trials Group.

SUMMARY: Twenty-six AIDS patients were enrolled in an open label pilot study to evaluate the efficacy and toxicity of topical 1 percent ophthalmic trifluridine solution for the treatment of chronic mucocutaneous herpes simplex virus disease unresponsive to at least 10 days of acyclovir therapy. Susceptibility testing to acyclovir, trifluridine, and foscarnet was determined by plaque reduction assay. Twenty-four patients were evaluable for efficacy and 25 for toxicity analyses. Seven patients (29 percent) had complete healing of lesions. The overall estimated median time to complete healing was 7.1 weeks. An additional seven patients had > or = 50 percent reduction in lesion area. The overall estimated median time to 50 percent healing was 2.4 weeks. Ten (42 percent) patients discontinued treatment for reasons other than primary treatment failure and seven (29 percent) for failure to respond to therapy. Baseline patient characteristics associated with greater reduction in lesion area included higher Karnofsky score (p = 0.05), fewer lesions (p = 0.07), smaller lesion area (p = 0.11), and trifluridine susceptibility (p = 0.07). Eight (33 percent) patients developed new lesions outside of the treatment area while on study, reflecting the local nature of this therapy. No dose-limiting toxicity attributable to trifluridine was reported. Given the limited options for the treatment of acyclovir-resistant herpes simplex disease, topical trifluridine may be a useful alternative in selected patients.

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.

The nucleation of receptor-mediated endocytosis.

A theory of the mechanical origins of receptor-mediated endocytosis shows that a spontaneous membrane complex formation can provide the stimulus for a local membrane motion toward the cytosol. This motion is identified with a nucleation stage of receptor-mediated endocytosis. When membrane complexes cluster, membrane deformation is predicted to be most rapid. The rate of growth of membrane depressions depends upon the relative rates of approach of aqueous cytosolic and extracellular fluids toward the cell membrane. With cytosolic and extracellular media characterized by apparent viscosities, the rate of growth of membrane depressions is predicted to increase as the extracellular viscosity nears the apparent viscosity of the cytosol and then to decrease when the extracellular viscosity exceeds that of the cytosol. To determine whether these trends would be apparent in the overall endocytosis rate constant, an experimental study of transferrin-mediated endocytosis in two different cell lines was conducted. The experimental results reveal the same dependence of internalization rate on extracellular viscosity as predicted by the theory. These and other comparisons with experimental data suggest that the nucleation stage of receptor-mediated endocytosis is important in the overall endocytosis process.

Effects of sho-saiko-to on production of prostaglandin E2 (PGE2), leukotriene B4 (LTB4) and superoxide from peripheral monocytes and polymorphonuclear cells isolated from HIV infected individuals.

The effects of Sho-saiko-to (SST), a traditional Chinese medicine, on the production of PGE2 from monocytes, LTB4 and superoxide from polymorphonuclear cells (PMNC) in HIV infected individuals were studied. SST inhibited the production of PGE2 from monocytes stimulated by opsonized zymosan in all groups including the healthy control group and also inhibited the production of superoxide from PMNC after stimulation with FMLP. On the other hand, SST enhanced the production of LTB4 when PMNC were stimulated by the calcium ionophore A23187. These results suggest that SST has different effects on the production of prostanoids or superoxide from monocytes and PMNC. Furthermore, our data indicates that inhibition of PGE2 or superoxide production will lead to indirect suppression of HIV, and enhancement of LTB4 will contribute to the upregulation of the immune reaction in HIV infected individuals.

Conservation of an intact human immunodeficiency virus type 1 vif gene in vitro and in vivo.

Replication of vif-negative human immunodeficiency virus type 1 (HIV-1) is attenuated in certain cell lines and highly impaired in peripheral blood lymphocytes in vitro. To determine whether intact vif is positively selected during natural HIV-1 infection and to determine vif sequence variability, we employed PCR amplification, cloning, and sequencing to investigate the vif region of replicating virus in short-term-passage HIV-1 primary isolates from five asymptomatic individuals and from five persons with AIDS. A total of 46 vif clones were obtained and analyzed. Recombinant proviruses were constructed from selected vif clones from one patient and found to be fully infectious. We found that 38 of the 46 clones sequenced carried open vif reading frames and that there was a low degree of heterogeneity of vif genes within isolates from the same individual and among isolates from different donors. The cysteines previously found to be essential for vif protein function were conserved in all clones. A phylogenetic tree constructed from all available vif nucleotide sequences resulted in a virus grouping similar to those of gag and env. Direct sequencing of vif amplified by PCR from uncultured lymphocytes of 15 individuals at various stages of progression toward AIDS demonstrated vif open reading frames in 13 of 15 samples tested. There was no obvious correlation between disease status and the presence of an intact vif within this sample group at the time of sample procurement. The conservation of the vif open reading frame in vitro and in vivo and its limited variability following virus transmission in vitro are consistent with a role for vif in natural HIV-1 infection.