Nanoparticle catalysts for proton exchange membrane fuel cells: can surfactant effects be beneficial for electrocatalysis?

Platinum (Pt) nanoparticles were prepared in aqueous dispersion using the non-ionic surfactant nonylphenolethoxylate (NP9) and the cationic surfactant tetradecyltrimethylammonium bromide (TTAB). The surfactants were added to give colloidal stability. Such species are generally considered to block electrochemical active sites and to be undesirable for the oxygen reduction reaction (ORR). However, the procedures used to remove them are likely to cause particle aggregation. The purpose of this work was to investigate the effect of surfactants on Pt ORR performance. The nanoparticles prepared using NP9 showed good oxygen reduction performance when compared with the commercial Pt/C catalyst TKK, without removing the surfactant. In contrast, Pt nanoparticles prepared using the cationic surfactant TTAB showed very poor ORR performance, exemplifying the importance of careful surfactant selection in catalyst synthesis.

Configuration of microbially synthesized Pd-Au nanoparticles studied by STEM-based techniques.

Bimetallic Pd-Au particles synthesized using Desulfovibrio desulfuricans bacteria are characterized using scanning transmission electron microscopy (STEM) with a high-angle annular dark field (HAADF) detector combined with energy dispersive x-ray (EDX) silicon drift detector (SDD) elemental mapping and plasmon electron energy-loss spectroscopy (EELS). When combined with EDX, theoretical considerations or EELS, the atomic-number contrast (Z-contrast) provided by HAADF-STEM is effective in characterizing the compositional configuration of the bimetallic nanoparticles. Homogeneous mixing and complex segregations have been found for different particles in this work. The EELS study has also found different behaviours corresponding to surface plasmon resonances in different regions of a single particle due to its heterogeneity and anisotropy. HAADF-STEM tomography has been performed to obtain three-dimensional (3D) visualization of the nanoparticles.

The influence of surface lubricity on the adhesion of Navicula perminuta and Ulva linza to alkanethiol self-assembled monolayers.

The settlement and adhesion of Navicula perminuta and Ulva linza to methyl-terminated alkanethiol self-assembled monolayers (SAMs) of increasing chain length has been investigated. Organisms were allowed to settle onto the monolayers and were subsequently exposed to hydrodynamic shear stress in order to determine their adhesion strength. Results show that as the SAM structure changes from amorphous to crystalline (C14), there is a marked change in the adhesion of N. perminuta and U. linza. Given that the SAMs in the series all exhibit similar contact angle behaviour and surface energy, it is hypothesized that the lubricity of the surface plays a role in determining the surface adhesion.

Splenogonadal fusion in an 18-month-old.

BACKGROUND: Splenogonadal fusion is rare abnormal congenital connection of splenic tissue and gonad. It commonly presents with either cryptorchidism or as a palpable mass. As a benign anomaly, orchiectomy is often unnecessary. Removal of the splenic component may be accomplished with preservation of the testicle. METHODS: An 18-month-old boy presented with right cryptorchidism and left retractile testicle. Laparoscopic examination found a viable right testicle, and a successful orchiopexy was performed. The left testicle demonstrated splenogonadal fusion. Discontinuous accessory splenules were noted along the path of testicular descent. After confirmation from a radionucleotide liver-spleen scan the patient was brought back to the operating room for open excision of the adherent splenic tissue and orchiopexy of the testicle via an open inguinal approach. CONCLUSION: Splenogonadal fusion is a rare condition, but may be suspected in children with cryptorchidism or palpable peri-testicular mass. As with the present patient, in most cases the splenic tissue may be successfully excised without injury to the testicle.

Electrostatically stabilised nanoparticles: self-organization and electron-beam patterning.

The self-organisation of citrate- and magnesium oleate-stabilised gold nanoparticles on SiO2/Si substrates was investigated. In drop deposition, nucleation of citrate-stabilised gold nanoparticles was observed at the rim of the droplet, symmetric or multibranched dendroid gold structures were found in the area between the rim and the central part of the droplet, depending on the drying temperature. Homogeneous submonolayer nanoparticle coverage was obtained by immersion of amineterminated SiO2/Si surfaces into a citrate-stabilised colloidal gold acidic solution. Drop deposition of magnesium oleate-stabilised gold nanoparticles onto the SiO2/Si surfaces resulted in the formation of uniformly close-packed nanoparticle arrays. Under electron beam irradiation, no apparent changes were found for monolayer films of citrate-stabilized particles, but sintering of the nanoparticles was observed in multilayer films. In contrast, coalescence of magnesium oleate-stabilised gold nanoparticle occurred in monolayer films after electron irradiation.

Physicochemical properties and aroma volatile profiles in a diverse collection of California-grown pomegranate (Punica granatum L.) germplasm.

Colorful antioxidant-rich fruits often convey astringency and sourness that juice consumers may not appreciate. We assessed properties in juices from a collection of California-grown pomegranate from the National Clonal Germplasm Repository. The goal was to evaluate overall differences in germplasm with quality traits classified as sweet, sweet-sour and sour. Previous relationships noted in sweet and sour cultivar attributes were observed. Wonderful generally clustered with sweet-sour and sour cultivars. Sweet low acid cultivars occasionally clustered closely with Wonderful which is hard to rationalize. The dominant compounds were 3-hexenol and 1-hexanol which allowed separation of Kara Gul, Haku-botan and Wonderful. Aldehyde and terpene content can be used to characterize cultivars. The study represents the first data on variation in juice qualities in different sweet, sweet-sour and sour cultivars, grown in California, compared with Wonderful. Data may help the juice industry better select raw juice materials in order to ultimately satisfy consumers.

Heterosupramolecular chemistry: programmed pseudorotaxane assembly at the surface of a nanocrystal.

Gold nanocrystals, stabilized by thiols covalently bound to a dibenzo[24]crown-8 moiety, have been programmed to recognize and selectively bind dibenzylammonium cations in solution. This results in a self-organization process at the surface of a nanocrystal with the assembly of a pseudorotaxane (see picture).

Iowa cochlear implant clinical project: results with two single-channel cochlear implants and one multi-channel cochlear implant.

Cochlear implants have become a realistic alternative for the management of profoundly deaf patients. A variety of implants with differing electrode designs and coding strategies have been developed by nine major implant centers around the world. Each center has their "star" patient, but objective comparisons between these different implant designs are unavailable. In order to determine the performance characteristics of the present generation of cochlear implants, comparison data are vital. We have developed an independent center where uniform objective comparisons of different cochlear implants can be performed longitudinally. This report will present results of nine patients implanted with three different cochlear implant prostheses. Four patients have been implanted with the Los Angeles (House) single-channel implant, three patients have received the Vienna (Hochmair) single-channel intracochlear device, and two patients have been implanted with the Melbourne (Clark) 21-channel unit. All patients have had 11 months or more of experience with their cochlear prostheses. The results of a comprehensive audiologic battery which includes audiovisual and environmental tasks are presented. All implants provide significant improvement in speechreading and sound awareness. The findings to date suggest that there is strong correlation between top-down cognitive processing (as reflected by lip reading skills) and performance with cochlear implants.

Audiological results with two single channel cochlear implants.

We tested six patients with single channel cochlear implants on several tests from the Minimal Auditory Capabilities battery and the Iowa Cochlear Implant Tests. All patients were able to discriminate some everyday sounds and to identify the number of syllables in the words presented. Five patients were able to identify speaker sex reliably. Surprisingly, some patients had difficulty discriminating between a modulated noise and a voice or between a question and a statement or identifying the accented word in a sentence. On several audiovisual tests, an improvement was observed for the sound plus vision condition compared to the vision only condition. This was particularly true for sentence tests, but was not uniform across patients or across tests.

Paediatric tracheostomy: persistent tracheo-cutaneous fistula following decannulation.

A retrospective analysis of 101 children with tracheostomies, all performed for upper airway obstruction and who were decannulated in a single department, is reported. Persistent tracheo-cutaneous fistula occurred in 43% of patients and this was significantly related to age at tracheostomy and duration of tracheostomy. The operation of tracheo-cutaneous fistula closure is described.

Relationship of pure-tone averages to speech reception threshold for male and female speakers.

The availability of a compact disc with a female speaker for clinical use has raised the issue of the equivalence between the female speaker and the previous standard male speaker for assessing the speech reception threshold (SRT). This study evaluated the relationship of two- and three-frequency averages to the SRT for a male speaker on an audio tape and a female speaker on a compact disc in two similar groups of clinic patients, each consisting of 215 ears. There were no significant differences between the SRTs for the two groups, suggesting that the two speakers/recordings are equivalent for clinical purposes. The SRTs from both speakers/recordings were within 6 dB of both the two- and three-frequency averages. There were no significant differences between the SRTs and the three-frequency average.

Panoramic radiographic survey of dentists participating in ADA health screening programs: 1976, 1977, and 1978.

Results of the panoramic examination of dentists participating in the health evaluation program of the ADA annual sessions held at Las Vegas (1976), Miami Beach (1977), and Anaheim (1978) were reported and compared as accurately as possible with the results of the panoramic examinations of dentists taking part in the health evaluation programs of the ADA annual sessions in 1964, 1966, and 1968. The panoramic radiograph continues to serve as a diagnostic aid in dental health evaluation programs. Only general impressions may be drawn from surveys of this nature for various reasons: the inability to follow up each case with a clinical examination; the lack of correlation of findings between examiners; and the use of different criteria each year. Generally, dentists examined in the health evaluation programs in 1976, 1977, and 1978 were in good dental health.

Effects of time compression and time compression plus reverberation on the intelligibility of Northwestern University Auditory Test No. 6.

The Tonal and Speech Materials for Auditory Perceptual Assessment, Disc 1.0 audio compact disc developed in 1992 includes several sets of degraded speech materials, two of which, time compression and reverberation, are described in this paper. The digital techniques used to compress the NU No. 6 materials (female speaker) on an 80386-based computer are described, along with a series of experiments on subjects with normal hearing that document the effects of the time compression on recognition performance. Experiment I examined at 70 dB SPL the effect on word recognition of 45, 55, 65, 70, and 75 percent compressions. Experiment II developed psychometric functions for the 45, 65, and 75 percent time-compression conditions. Experiment III defined the effects that time-compression degradation (45% and 65%) plus reverberation degradation (0.3 sec) had on the recognition performance on the NU No. 6 materials. Based on the experiments, four conditions (45% compression, 65% compression, 45% compression plus 0.3-sec reverberation, and 65% compression plus 0.3-sec reverberation) were selected and recorded on the compact disc. In the compact disc trials, normative data on the four conditions were developed from 120 listeners with normal hearing.

A sharp debridement procedure devised by specialist nurses.

In the clinical governance era, self-education is not adequate training for nurses to carry out sharp debridement, which is a risky process. Specialist nurses in south-east London drew up a workable procedure for training and practice.

Total bed management: the way forward in pressure sore prevention.

King's College Hospital, London, is the first trust to implement total bed management (TBM) to assist in the reduction and prevention of pressure sores. TBM is a new concept, whereby the tissue viability, manual handling and therapy needs of the trust are met at reduced costs through a partnership with a contractor. The introduction of a large number of electric bed frames and foam mattress replacements, with the availability of dynamic pressure-relieving equipment and a service agreement, has led to an expected trust saving of 86,000 Pounds in 1998/1999 and 100,000 Pounds in 1999/2000 onwards. This article outlines the perceived benefits of this approach.

Vascular programming in twins: the effects of chorionicity and fetal therapy for twin-to-twin transfusion syndrome.

We assessed vascular programming in genetically identical monochorionic twin pairs with twin-to-twin transfusion syndrome (TTTS) treated differently in utero by serial amnioreduction or fetal laser arterial photocoagulation. This case-control study re-assessed four twin groups at median 11 years comprising 20 pairs of monochorionic diamniotic twins: nine treated by amnioreduction (TTTS-amnio) and eleven by laser (TTTS-laser) with seven monochorionic and six dichorionic control pairs. Outcome measures were current blood pressure (BP), brachio-radial arterial stiffness derived from pulse wave velocity (PWV), resting microcirculation (Flux) and response to heating and post-occlusive reactive hyperaemia measured using laser Doppler. Potential confounders [PWV and BP at first study, current height, weight, heart rate and twin type (ex-recipient, ex-donor or heavier/lighter of pair)] were accounted for by Mixed Linear Models statistical methodology. PWV dichorionic > monochorionic (P = 0.024); systolic and diastolic BP dichorionic > TTTS-amnio and TTTS-laser (P = 0.004, P = 0.02 and P = 0.005, P = 0.02, respectively). Within-twin pair pattern of PWV discordance was similar in laser treated and dichorionic controls (heavier-born > lighter), opposite to TTTS-amnio and monochorionic controls. Flux monochorionic > dichorionic (P = 0.044) and heavier > lighter-born (P = 0.024). TTTS-laser and dichorionic diamniotic showed greatest hyperaemic responses (dichorionic > TTTS-amnio or monochorionic controls (P = 0.007, P = 0.025). Hyperaemic responses were slower in heavier-born twins (P = 0.005). In summary, monochorionic twins had lower BP, arterial stiffness and increased resting vasodilatation than dichorionic twins implying shared fetal circulation affects vascular development. Vascular responses in laser-TTTS were similar to dichorionic and opposite to TTTS-amnio suggesting a lasting effect of fetal therapy on vascular health.