Tuning friction and slip at solid-nanoparticle suspension interfaces by electric fields.

We report an experimental Quartz Crystal Microbalance (QCM) study of tuning interfacial friction and slip lengths for aqueous suspensions of TiO2 and Al2O3 nanoparticles on planar platinum surfaces by external electric fields. Data were analyzed within theoretical frameworks that incorporate slippage at the QCM surface electrode or alternatively at the surface of adsorbed particles, yielding values for the slip lengths between 0 and 30 nm. Measurements were performed for negatively charged TiO2 and positively charged Al2O3 nanoparticles in both the absence and presence of external electric fields. Without the field the slip lengths inferred for the TiO2 suspensions were higher than those for the Al2O3 suspensions, a result that was consistent with contact angle measurements also performed on the samples. Attraction and retraction of particles perpendicular to the surface by means of an externally applied field resulted in increased and decreased interfacial friction levels and slip lengths. The variation was observed to be non-monotonic, with a profile attributed to the physical properties of interstitial water layers present between the nanoparticles and the platinum substrate.

Free energies of (Co, Fe, Ni, Zn)Fe2O4 spinels and oxides in water at high temperatures and pressure from density functional theory: results for stoichiometric NiO and NiFe2O4 surfaces.

A set of effective chemical potentials (ECPs) are derived that connect energies of (Co, Fe, Ni, Zn)Fe2O4 spinels and oxides calculated at 0 K from density functional theory (DFT) to free energies in high temperature and pressure water. The ECPs are derived and validated by solving a system of linear equations that combine DFT and experimental free energies for NiO, ZnO, Fe2O3, Fe3O4, FeO(OH), CoFe2O4, ZnFe2O4, NiFe2O4 and H2O. To connect to solution phase chemistry, a set of ECPs are also derived for solvated Ni(2+), Zn(2+), Fe(2+) and Fe(3+) ions using an analogous set of linear equations and the solid ECPs. The ECPs are used to calculate free energies of low index stoichiometric surfaces of nickel oxide (NiO) and nickel ferrite (NiFe2O4) in water as a function of temperature from 300 to 600 K at a pressure of 155 bar. Surface denuding at high temperatures is predicted, the implications of which for the formation of oxide corrosion products on heat transfer surfaces in light-water nuclear reactors are discussed.

Immobilization of mycotoxins on modified nanodiamond substrates.

The effectiveness of modified nanodiamonds (NDs) for the adsorption of mycotoxins, aflatoxin B1 (AfB1) and ochratoxin A (OTA), are investigated in this paper. Binding and release mechanisms of the mycotoxins were addressed using an assortment of NDs modified by different surface treatments, including carboxylation, hydrogenation and hydroxylation, followed by isolating NDs of different sizes. Results indicate that AfB1 adsorption on NDs is directly related to aggregate size, whereas OTA adsorption is primarily centered upon electrostatic interactions that depend on the types of surface functional groups on the ND. Findings show that modified NDs with small aggregation sizes (∼40 nm) have greater adsorption capacities for AfB1 than yeast cells walls and untreated NDs from various vendors, but comparable to activated charcoal. In OTA studies, positively charged NDs outperformed clay minerals, which are well-known and efficient sorbents for mycotoxins. Furthermore, ND adsorption capacities can be preserved in a wide range of pH.

STM, QCM, and the windshield wiper effect: a joint theoretical-experimental study of adsorbate mobility and lubrication at high sliding rates.

We have observed that when mobile adsorbed films of benzene, tricresyl phosphate, and tertiary-butyl phenyl phosphate are present on the surface electrode of a quartz crystal microbalance (QCM), oscillation of the QCM produces clearer scanning tunneling microscope (STM) images of the electrode surface. This is in contrast to an immobile overlayer of iodobenzene, where oscillation of the QCM does not affect image quality. This observation is attributed to a "windshield wiper effect", where at MHz frequencies the tip motion maintains a region of the surface where the absorbate concentration is reduced, which leads to a clearer image. A straightforward model is presented that supports this conclusion and that provides guidelines for effective lubrication of contacts operating at MHz frequencies.

Molecular dynamics simulations of dimer opening on a diamond {001}(2x1) surface.

Computer simulations of hydrocarbon and related molecules using empirical force fields have become important tools for studying a number of biological and related processes at the atomic scale. Traditional force fields, however, cannot be used to simulate dynamic chemical reactivity that involves changes in atomic hybridization. Application of a many-body potential function allows such reactivity to occur in a computer simulation. Simulations of the reaction of small hydrocarbon molecules adsorbed on a reconstructed diamond {001}(2x1) surface suggest that these hydrocarbons are highly reactive species and that initial stages of diamond growth proceed through a dimer-opening mechanism. Rates estimated from transition state theory of two interconversions between states where the dimer is open and closed are given.

Suprarenal Greenfield filter placement to prevent pulmonary embolus in patients with vena caval tumor thrombi.

The presence of tumor thrombus secondary to inferior vena caval extension from renal carcinoma carries the threat of pulmonary tumor embolus. In theory, safe prophylaxis could be accomplished by placement of a Greenfield filter in the suprarenal vena cava, which has been accomplished without complication. We treated 6 patients with renal call carcinoma and extensive tumor thrombus of the vena cava with suprarenal filter placement as an adjunct to thrombectomy and nephrectomy. Clinically all 6 patients have done well. However, the over-all rate of vena caval thrombosis or occlusion associated with infrarenal filter placement is 3 to 5%. To investigate the potential risk to renal function if a vena caval occlusion occurred above a solitary kidney shortly after unilateral nephrectomy, we performed suprarenal inferior vena caval ligations after unilateral nephrectomy in 10 dogs. A total of 6 dogs suffered persistent loss of renal function and 3 of these 6 died of uremia. Of 4 dogs who underwent suprarenal inferior vena caval ligation only 1 (25%) had persistent compromise of renal function. A total of 2 dogs underwent unilateral nephrectomy only without compromise of normal renal function. We conclude that the risk of total vena caval occlusion after suprarenal Greenfield filter placement is small. However, should it occur in the setting of recent nephrectomy there is potential for significant renal morbidity. In selected patients this risk may be offset by the potential benefits that the filter offers in terms of protection against tumor and/or bland pulmonary embolus. Further clinical experience will be needed to strengthen and clarify the indications and benefits of preoperative or intraoperative filter placement as reported.

Adrenal pheochromocytoma presenting with persistent abdominal and flank pain.

Pheochromocytoma is classically associated with paroxysms of headache and hypertension. Its presentation, however, may be more varied and subtle. We present a case of an adolescent female who complained of right upper quadrant and flank pain. A right adrenal pheochromocytoma was diagnosed and subsequently removed. The pertinent literature is discussed.

Transplantation of horseshoe kidney into single recipient.

A case of successful en bloc transplantation of a horseshoe kidney into a single recipient is reported. The literature is briefly reviewed. The use of horseshoe kidneys in transplantation is recommended in selected cases.

Comparison of transrectal fine-needle aspiration cytology and core needle biopsy in diagnosis of prostate cancer.

One hundred sixty-nine transrectal fine-needle aspirations of the prostate gland were performed in 166 patients over a two-year period. The results were compared with simultaneous core needle biopsy performed in all but 4 patients. Forty-seven (28%) aspirations were either unsatisfactory or inconclusive. Of the remaining 122 (72%) patients in whom a cytologic diagnosis could be made, core biopsy was available in 120. Aspiration cytology was 87 percent sensitive and 96 percent specific with an overall agreement of 93 percent with core biopsy. No major complications occurred. We conclude that fine-needle aspiration of the prostate is accurate, safe, and cost-effective, and greater application of this technique is encouraged.

Squamous cell carcinoma of bladder after successful intravesical therapy with Bacillus Calmette-Guérin.

A case of invasive squamous cell carcinoma of the bladder following intravesical immunotherapy with Bacillus Calmette-Guérin in a patient with pre-existing squamous dysplasia of the bladder is presented.

Flow cytometric analysis of DNA content in children with neuroblastoma.

Flow cytometric DNA content analyses were performed in a retrospective study of archival tumor specimens of 15 patients with diagnosed neuroblastoma treated at a single institution. Survival statistics were positively influenced by the presence of aneuploidy. Kaplan-Meier analysis indicated a significant survival advantage for patients with aneuploid tumors (P = .036). Survivors were significantly younger at the time of diagnosis than nonsurvivors, but age at diagnosis did not correlate with DNA content. We conclude that DNA content analysis may be of value in determining the prognosis for children with neuroblastoma.

Mortality associated with feeding catheter jejunostomy after radical cystectomy.

Twenty-five patients undergoing cystectomy and diversion for transitional cell carcinoma of the bladder and 8 patients having major surgery for renal and testes neoplasms and trauma have received needle jejunostomy placement at the time of surgery. One patient died secondary to vascular collapse. Postmortem examination revealed necrosis of the entire small bowel except the conduit segment. The implications of these findings are discussed.

Upper tract urothelial malignancy after cyclophosphamide therapy: a case report and literature review.

We report an unusual case of simultaneous transitional cell carcinoma of the renal pelvis and distal ureter without transitional cell carcinoma of the bladder occurring after chronic cyclophosphamide therapy for nonHodgkin's lymphoma. Other upper tract neoplasms after cyclophosphamide are reviewed.