The Simons Observatory: Cryogenic half wave plate rotation mechanism for the small aperture telescopes.

We present the requirements, design, and evaluation of the cryogenic continuously rotating half-wave plate (CHWP) for the Simons Observatory (SO). SO is a cosmic microwave background polarization experiment at Parque Astronómico de Atacama in northern Chile that covers a wide range of angular scales using both small (⌀0.42 m) and large (⌀6 m) aperture telescopes. In particular, the small aperture telescopes (SATs) focus on large angular scales for primordial B-mode polarization. To this end, the SATs employ a CHWP to modulate the polarization of the incident light at 8 Hz, suppressing atmospheric 1/f noise and mitigating systematic uncertainties that would otherwise arise due to the differential response of detectors sensitive to orthogonal polarizations. The CHWP consists of a 505 mm diameter achromatic sapphire HWP and a cryogenic rotation mechanism, both of which are cooled down to ∼50 K to reduce detector thermal loading. Under normal operation, the HWP is suspended by a superconducting magnetic bearing and rotates with a constant 2 Hz frequency, controlled by an electromagnetic synchronous motor. We find that the number of superconductors and the number of magnets that make up the superconducting magnetic bearing are important design parameters, especially for the rotation mechanism's vibration performance. The rotation angle is detected through an angular encoder with a noise level of 0.07 µrad s. During a cooldown process, the rotor is held in place by a grip-and-release mechanism that serves as both an alignment device and a thermal path. In this paper, we provide an overview of the SO SAT CHWP: its requirements, hardware design, and laboratory performance.

Selective Visualization of Live Intestinal Parasites in Stool Specimens Without Purification.

PURPOSE: Microscopic observation of live parasites in the stool is an important diagnostic tool in human and veterinary medicine. Because of the presence of large amounts of contaminating organic matter, microscopic analysis must be preceded by time-consuming pre-purification steps. Transmission-through-dye (TTD) optical microscopy obviates this problem. The purpose of this study is to illustrate the use of TTD for the analysis of stool samples. METHODS: TTD imaging is based on the exclusion of a strongly absorbing dye by living cells. A food colorant Acid Blue 9 (AB9) is added to a fecal suspension, and the sample is observed under transmitted illumination through a 630 nm bandpass filter. AB9 strongly absorbs red light, and it comes out of the sample significantly attenuated. However, if a viable cell of any origin is present in the sample, it excludes the dye and reduces the depth of the light-absorbing layer. RESULTS: Live cells or eggs appear bright red on a dark background, while most of the organic contaminants remain dark. The method has been demonstrated on schistosomes, hookworms, giardia, yeast, and other organisms. CONCLUSION: TTD dramatically increases the visibility of live parasites and permits their direct observation in a fecal suspension. TTD can be enabled on any microscope by simply adding a red filter.

Synthesis of cationic alkylated chitosans and an investigation of their rheological properties and interaction with anionic surfactant.

Two methods were used to alkylate high MW chitosan with glycidyltrimethylammonium chloride (GTAC) in order to produce chitosan derivatives that are water-soluble throughout the pH range. In addition, a novel chitosan derivative was created by alkylating one of the products with the GTAC analogue Quab 342 containing C12 alkyl chains. The phase behaviour and rheological characteristics of the chitosan derivatives were studied in the presence of anionic surfactant. The derivatives were found to form soluble complexes at low and high SDS concentrations and that the Quab 342 derivative was able to form gels.

The interfacial, emulsification and encapsulation properties of hydrophobically modified inulin.

Octenyl- and dodecenyl succinic anhydride derivatives (OSA- and DDSA-) of inulin have been synthesised and their solution and interfacial properties have been determined and compared to a commercially available alkylated inulin, Inutec SP1. All samples formed micellar aggregates in solution above a critical concentration (critical aggregation concentration) and were able to 'dissolve' a hydrophobic dye. They were also able to form stable oil-in-water (O/W) emulsions as assessed by measurements of their droplet size as a function of time. DDSA-inulin with a high degree of substitution was found to be effective at encapsulating beta carotene using the solvent evaporation method which yielded a solid which dissolved readily in simulated gastric fluid. The results confirm the potential application of these materials in a number of areas including, drug delivery, pharmaceuticals, neutraceuticals, cosmetics and personal care.

Synthesis, characterisation and physicochemical properties of hydrophobically modified inulin using long-chain fatty acyl chlorides.

A series of inulin derivatives were synthesized in aqueous solution using acyl chlorides with varying alkyl chain length (C10-C16). They were characterised using a number of techniques including MALDI TOF-MS, 1H NMR and FTIR and their degree of substitution determined. The solution properties of the hydrophobically modified inulins were investigated using dye solubilisation and surface tension and it was confirmed that the molecules aggregated in solution above a critical concentration (critical aggregation concentration, CAC). The value of the CAC was found to be reasonably consistent between the different techniques and was shown to decrease with increasing hydrophobe chain length. It was found that the C10, C12 and C14 derivatives formed stable oil-in-water emulsions and the emulsion droplet size decreased with increasing alkyl chain length. The C16 derivative was not able to produce stable oil-in-water emulsions; however, it was able to form stable water-in-oil emulsions. The fact that the derivatives are able to form micellar-like aggregates and stabilise emulsions makes them suitable candidates for the encapsulation and delivery of active compounds with potential application in food, cosmetic, personal care and pharmaceutical formulations.

Orexigenic Gene Expression in Late Gestation Ovine Foetal Hypothalamus is Sensitive to Maternal Undernutrition and Realimentation.

Adverse nutritional effects on developing foetal hypothalamic appetitive pathways may contribute to programmed hyperphagia and obesity in intra-uterine growth-restricted, low birth weight offspring. In the present study, for the first time, hypothalamic gene expression for primary orexigenic and anorexigenic genes was examined in late gestation ovine foetuses (130 days; term=145 days) whose mothers were undernourished (UN) or well-nourished (C) throughout pregnancy, or transferred from UN to C on day 90 (UN-C). Pregnancies resulted from singleton embryo transfer into adolescent growing ewes. Body weight, carcass fat content and perirenal adipose tissue (PAT) mass were all lower for UN (n=9) than C (n=7) and intermediate for UN-C foetuses (n=6), with no effect of sex. PAT leptin gene expression (by the reverse transcriptase-polymerase chain reaction) was lower in UN than C and UN-C groups, and lower in males than females. Gene expression (by in situ hybridisation with radiolabelled riboprobes) in the arcuate nucleus was greater in UN than C foetuses for neuropeptide Y (NPY), agouti-related peptide (AGRP) and leptin receptor (OBRb) but not different for pro-opiomelanocortin and cocaine- and amphetamine-regulated transcript. Gene expression in UN-C foetuses was intermediate for NPY and AGRP and not different from C foetuses for OBRb. Gene expression for NPY, AGRP and OBRb correlated negatively with foetal carcass fat content and with PAT leptin gene expression across all groups. Males had greater mRNA expression for AGRP than females, with NPY and OBRb showing similar trends. Therefore, maternal undernutrition throughout pregnancy increased orexigenic gene expression in the late gestation foetal hypothalamus, and expression levels were largely normalised by improved maternal nutrition in the last third of pregnancy. These findings may have implications for avoiding or correcting prenatal programming of postnatal hyperphagia and obesity.

Tailoring precursors for deposition: synthesis, structure, and thermal studies of cyclopentadienylcopper(i) isocyanide complexes.

We report here the synthesis and characterization of a family of copper(I) metal precursors based around cyclopentadienyl and isocyanide ligands. The molecular structures of several cyclopentadienylcopper(I) isocyanide complexes have been unambiguously determined by single-crystal X-ray diffraction analysis. Thermogravimetric analysis of the complexes highlighted the isopropyl isocyanide complex [(η(5)-C5H5)Cu(CN(i)Pr)] (2a) and the tert-butyl isocyanide complex [(η(5)-C5H5)Cu(CN(t)Bu)] (2b) as possible copper metal chemical vapor deposition (CVD) precursors. Further modification of the precursors with variation of the substituents on the cyclopentadienyl ligand system (varying between H, Me, Et, and (i)Pr) has allowed the affect that these changes would have on features such as stability, volatility, and decomposition to be investigated. As part of this study, the vapor pressures of the complexes 2b, [(η(5)-MeC5H4)Cu(CN(t)Bu)] (3b), [(η(5)-EtC5H4)Cu(CN(t)Bu)] (4b), and [(η(5)-(i)PrC5H4)Cu(CN(t)Bu)] (5b) over a 40-65 °C temperature range have been determined. Low-pressure chemical vapor deposition (LP-CVD) was employed using precursors 2a and 2b to synthesize thin films of metallic copper on silicon, gold, and platinum substrates under a H2 atmosphere. Analysis of the thin films deposited onto both silicon and gold substrates at substrate temperatures of 180 and 300 °C by scanning electron microscopy and atomic force microscopy reveals temperature-dependent growth features: Films grown at 300 °C are continuous and pinhole-free, whereas films grown at 180 °C consist of highly crystalline nanoparticles. In contrast, deposition onto platinum substrates at 180 °C shows a high degree of surface coverage with the formation of high-density, continuous, and pinhole-free thin films. Powder X-ray diffraction and X-ray photoelectron spectroscopy (XPS) both show the films to be high-purity metallic copper.

Antiproliferative and apoptosis-inducing activity of an oxidovanadium(IV) complex with the flavonoid silibinin against osteosarcoma cells.

Flavonoids are a large family of polyphenolic compounds synthesized by plants. They display interesting biological effects mainly related to their antioxidant properties. On the other hand, vanadium compounds also exhibit different biological and pharmacological effects in cell culture and in animal models. Since coordination of ligands to metals can improve or change the pharmacological properties, we report herein, for the first time, a detailed study of the mechanisms of action of an oxidovanadium(IV) complex with the flavonoid silibinin, Na2[VO(silibinin)2]·6H2O (VOsil), in a model of the human osteosarcoma derived cell line MG-63. The complex inhibited the viability of osteosarcoma cells in a dose-dependent manner with a greater potency than that of silibinin and oxidovanadium(IV) (p < 0.01), demonstrating the benefit of complexation. Cytotoxicity and genotoxicity studies also showed a concentration effect for VOsil. The increase in the levels of reactive oxygen species and the decrease of the ratio of the amount of reduced glutathione to the amount of oxidized glutathione were involved in the deleterious effects of the complex. Besides, the complex caused cell cycle arrest and activated caspase 3, triggering apoptosis as determined by flow cytometry. As a whole, these results show the main mechanisms of the deleterious effects of VOsil in the osteosarcoma cell line, demonstrating that this complex is a promising compound for cancer treatments.

Antitumor properties of a vanadyl(IV) complex with the flavonoid chrysin [VO(chrysin)2EtOH]2 in a human osteosarcoma model: the role of oxidative stress and apoptosis.

Flavonoids, a polyphenolic compound family, and the vanadium compounds have interesting biological, pharmacological, and medicinal properties. We report herein the antitumor actions of the complex [VO(chrysin)2EtOH]2 (VOchrys) on the MG-63 human osteosarcoma cell line. Oxovanadium(IV), chrysin and VOchrys caused a concentration-dependent inhibition of cell viability. The complex was the strongest antiproliferative agent (p < 0.05). Cytotoxicity and genotoxicity studies also showed a concentration effect. Reactive oxygen species (ROS) and the alterations in the GSH/GSSG ratio underlie the main mechanisms of action of VOchrys. Additions of ROS scavengers (vitamin C plus vitamin E) or GSH to the viability experiments demonstrated beneficial effects (p < 0.01). Besides, the complex triggered apoptosis, disruption of the mitochondria membrane potential (MMP), increased levels of caspase 3 and DNA fragmentation measured by the sub-G1 peak in cell cycle arrest experiments (p < 0.01). Collectively, VOchrys is a cell death modulator and a promissory complex to be used in cancer treatments.

Synthesis, characterization and self-assembly of biosurfactants based on hydrophobically modified inulins.

Biosurfactants have been synthesized using a low energy, environmentally friendly process by the derivatization of inulin with octenyl (OSA) and dodecenyl (DDSA) succinic anhydrides in aqueous solution. The inulin and its derivatives have been characterized using gel permeation chromatography/multi angle light scattering (GPC/MALLS), high-performance anion exchange chromatography with pulsed amperometric detection (HPAEC-PAD), Fourier transform infrared spectroscopy (FTIR), and NMR, and the reaction efficiency was found to be between 59 and 95%. The efficiency was generally higher for OSA derivatives compared to DDSA derivatives. The hydrophobic derivatives were found to aggregate in solution and the critical aggregation concentration (CAC) was determined using dye solubilization, surface tension, dynamic light scattering (DLS), and conductivity. There was reasonable agreement in the CAC values obtained by the different techniques except for conductivity. It was found that the CAC decreased with increasing alkenyl chain length and degree of modification, and the values were significantly lower for the DDSA derivatives compared to the OSA derivatives. GPC elution profiles for the DDSA-inulin using 12 mol % reagent confirmed the presence of aggregates with a molecular mass of ∼2.5 × 10(6) g/mol and a radius of gyration of ∼25 nm corresponding to ∼550 inulin molecules. DLS study was undertaken to determine the hydrodynamic radius, and values obtained for the DDSA (12%) derivative were 30 nm in both water and 0.1 M sodium nitrate, while for the OSA (12%) derivative values of 13 and 7 nm were obtained. The derivatives have potential application in the stabilization of particulate dispersions and emulsions and also in the encapsulation and delivery of drugs.

Metal organic chemical vapour deposition of vertically aligned ZnO nanowires using oxygen donor adducts.

Vertically aligned zinc oxide (ZnO) nanowires (NWs) have been grown by liquid injection Metal Organic Chemical Vapour Deposition, using oxygen donor adducts of Me2Zn. The growth and characterisation of the nanowires grown using [Me2Zn(L)] where L = monodentate ethers, tetrahydrofuran (C4H8O) (1), tetrahydropyran (C5H10O) (2), furan (C4H4O) (3) and the bidentate ethers, 1,2-dimethoxyethane (C4H12O2,) (4) 1,4-dioxane (C4H8O2) (5) and 1,4-thioxane (C4H8SO) (6) is discussed. Single crystal X-ray structures of (4), (5), (6) have been established and are included here. The ZnO NWs were deposited in the absence of a seed catalyst on Si(111) and F-doped SnO2/glass substrates over the temperature range 350-600 degrees C. X-ray diffraction (XRD) data shows that the nanowires grown from all adduct precursors were deposited in the wurtzitic phase.

Comparing the needs of health professional and peer cancer support group facilitators in an Australian context.

This study explored the perceived needs of health professional and peer facilitators of cancer support groups. Participants were facilitators of support groups affiliated with The Cancer Council Victoria (Australia). Facilitators completed questionnaires assessing their experience of support group facilitation, including training and support needs. Data from health professional and peer facilitators (n= 74) were analysed in this paper. The majority of facilitators (88%) were female; 57% had run their group for more than 3 years, and 47% reported between 11 and 20 people attended each group. Although results showed the characteristics of support groups are broadly similar for peers and professionals, there were some distinct differences in perceived needs. Health professional facilitators were more likely than peers to regard training as valuable and beneficial to their role. In addition, health professionals more frequently reported needing debriefing as well as more difficulty accessing debriefing than cancer peers. This study builds on the small body of literature exploring the experiences of cancer support group facilitators. Given the experiences and needs of health professional and peer facilitators may differ, it may be relevant to tailor training and support so that it meets the needs of both health professionals and cancer peers.

Mouse models of dominant optic atrophy: what do they tell us about the pathophysiology of visual loss?

Dominant optic atrophy (DOA) is the most common inherited optic neuropathy affecting one in every 12,000 people. It presents with bilateral visual loss, central visual fields defects, colour vision disturbance and optic disc pallor. OPA1 has been identified as the responsible gene and its locus mapped to chromosome 3q28-q29. Mutations in this gene are responsible for the clinical phenotype in over 70% of patients with DOA. Histopathological studies in tissues from patients reveal loss of retinal ganglion cells but the paucity of viable human tissue has raised the importance of an animal model to study the pathophysiology of the disease. In the last decade considerable work has gone into the generation of animal, most notably mouse, models of Opa1 DOA. Two murine models of DOA have been published, designated B6;C3-Opa1(Q285STOP) and B6;C3-Opa1(329-355del) and they provide valuable insights with respect to neurological and visual phenotyping, mitochondrial dysfunction, optic nerve and axonal changes, retinal ganglion cell depletion and dendritic atrophy. Here we summarise the current state of knowledge of the mechanisms of disease based on data from these models of Opa1 DOA.

Electrostatic interaction and complex formation between gum arabic and bovine serum albumin.

The interaction of gum arabic (GA) and bovine serum albumin (BSA) has been investigated through turbidity and light scattering intensity measurements and by the use of dynamic light scattering, laser Doppler velocimetry, and isothermal titration calorimetry. It has been shown that GA and BSA can form soluble and insoluble complexes depending on the solution pH and the mixing ratio and is a function of the net charge on the complex. Soluble complexes were obtained when the electrophoretic mobility was greater than ±1. 5 µm s(-1) V(-1) cm(-1). Changes in the value of the isoelectric point of the complexes with mixing ratio and isothermal titration calorimetric data indicated that complexes formed at pHs 3 and 4 consisted of ∼60 BSA molecules for every GA molecule, while at pH 5 there were ∼10 BSA molecules per GA molecule. Calorimetric studies also indicated that the interaction occurred in two stages at both pH 3 and pH 4, but that the nature of the interaction at these two pH values was significantly different. This was attributed to differences in the relative magnitude of the positive and negative charges on the BSA and GA, respectively, and possibly due to changes in the BSA conformation. The fact that there is an interaction at pH 5, which is above the isoelectric point of the BSA, is due to the interaction of the carboxylate groups on the GA with positive patches on the BSA or to the charge regulation of the protein-polysaccharide system brought about by changes in dissociation equilibria. Complexation is reduced as the ionic strength of the solvent increases and is prevented at a NaCl concentration of 120 mM.

Liquid injection atomic layer deposition of silver nanoparticles.

Silver nanoparticles are being developed for applications in plasmonics, catalysts and analytical methods, amongst others. Herein, we demonstrate the growth of silver nanoparticles using an atomic layer deposition (ALD) process for the first time. The silver was deposited from pulses of the organometallic precursor (hfac)Ag(1,5-COD) ((hexafluoroacetylacetonato)silver(I)(1,5-cyclooctadiene)) dissolved in a 0.1 M toluene solution. Catalytic oxidative dehydrogenation of the silver was achieved using intermittent pulses of propanol. The effect of substrate temperature on the size and distribution of nanoparticles has been investigated over the temperature range 110-150 degrees C. Transmission electron microscopy reveals that the nanoparticles consist of face centred cubic, facetted silver crystallites. The localized surface plasmon modes of the nanoparticles have been investigated using electron energy loss spectroscopy mapping. The distributions of plasmons within the ALD nanoparticles are comparable to those grown by solution methods. Both dipolar and quadrupolar resonant modes are observed, which is consistent with previous discrete dipole approximation models. Energy loss mapping of a loss feature at 8.1 eV reveals that it correlates with the bulk or volume region of the silver nanoparticles investigated here.

Third-body abrasive wear challenge of 32 mm conventional and 44 mm highly crosslinked polyethylene liners in a hip simulator model.

Hip simulator studies have shown that wear in the polyethylene liners used for total hip replacements increased with the larger-diameter femoral balls and could also be exacerbated by third-body abrasion. However, they also indicated that the more highly cross-linked polyethylene (HXPE) bearings were more wear resistant than conventional polyethylene (CXPE) bearings. Unfortunately the HXPE bearings appeared to be particularly sensitive to adverse wear conditions. One simulator study in particular indicated that poly(methyl methacrylate) (PMMA) debris increased wear sixfold by means of two-body abrasive interactions rather than the supposed third-body abrasion or roughening effects of the Co-Cr surfaces. There has been no confirmation of such novel theories. Therefore the goal of this study was to investigate the sensitivity of large-diameter HXPE bearings to the third-body PMMA wear challenge in a hip simulator model. An orbital hip simulator was used in standard test mode with a physiological load profile. The 32 mm control liners were machined from moulded GUR1050 and gamma irradiated to 35 kGy under nitrogen (CXPE). The 44 mm liners were also from moulded blanks, gamma irradiated to 75 kGy, machined to shape, given a proprietary heat treatment, and sterilized by gas plasma (HXPE). As in the published simulator model, the study was conducted in three phases. In phase 1, all cups were run in standard ('clean') lubricant for 1.5 x 10(6) cycles duration. In phase 2, three CXPE cups and six HXPE cups were run for 2 x 10(6) cycles with a slurry of PMMA particles added to the lubricant. In phase 3, the implants were again run in 'clean' lubricant for 2 x 10(6) cycles duration. In addition, three HXPE cups were run as wear controls for 5.5 x 10(6) cycles duration in clean lubricant. In phase-1, the HXPE liners demonstrated twelvefold reduced wear compared with the CXPE controls. The 32 mm and 44 mm Co-Cr balls were judged of comparable roughnesses. However, the surface finish of HXPE liners was superior to that of CXPE liners. In phase-2 abrasion, wear rates increased sixfold and eighty-fold for CXPE and HXPE bearings respectively. These data confirmed that HXPE bearings were particularly sensitive to 'severe' test modes. The Co-Cr balls revealed numerous surface patches representing transferred PMMA with average transient roughness increased to 25 nm and 212 nm for the 32 mm and 44 mm balls respectively. These PMMA patches produced an aggressive two-body abrasion wear of the polyethylene. After cleaning, the ball roughness returned to near normal. Therefore the Co-Cr roughness was not an issue in this severe test mode. In phase 3, the wear decreased to near the index values of phase 1, while liner roughness dropped by more than 90 per cent. The control CXPE liners now demonstrated twice the wear of the HXPE, as would be predicted comparing the diameter and cross-linking algorithms. No previous study has correlated polyethylene roughness profiles to wear performance. In phase 2, PMMA abrasion created significant damage to the polyethylene surfaces. The average roughness Sa of CXPE liners increased to 3.6 microm, a twenty-four-fold increase with some scratches up to 40 microm deep. The HXPE roughness also increased but only to 1.5 microm, a ninefold increase. The scratch indices Sz and Sp for HXPE surfaces were also 50 per cent less severe than on CXPE surfaces. However, within 2 x 10(6) cycles duration of phase 3, all liners had recovered to virtually their original surface finish in phase 1. In all test phases, the surface finish of the HXPE liners remained superior to control liners. These experimental data confirmed many of the results from the previous simulator study with the PMMA abrasion models. Thus the 44 mm liners appeared an excellent clinical alternative to the smaller ball designs used in total hip replacements.

What is a "normal" wear pattern for metal-on-metal hip bearings?

In addition to classical run-in and steady-state wear phases, metal-on-metal (MOM) hip bearings have encountered "runaway wear" (RAW) trends in simulator studies. This puzzling behavior has resulted in 2- to 19-fold wear increases compared with other apparently "identical" bearings. MOM bearings have shown five identifiable RAW wear patterns in joint simulators; therefore, additional descriptive terms were used here to indicate various observed patterns, for example, "breakaway wear" (BAW), which was defined as a higher wear trend that recovers to steady-state wear. As these trends commonly occur for MOM, this raises the question of what can be considered "normal" behavior or "abnormal"? In an effort to identify possible causes for this behavior, the current study investigated six Co-Cr bearings, which closely matched with respect to geometrical tolerances. Despite close control of design and test variables, BAW occurred in 30% of the MOM bearings, producing a threefold wear increase above otherwise identical MOM bearings within the same group. The majority of the BAW (85%) occurred on the cup side and was validated by growth of wear scars and concentrations of metal ions. One bearing that showed continuing BAW at 5 Mc revealed a cup that was 50% smoother than other cups whereas its mating head was 50% rougher, thus signifying that highly polished areas were sites of the highest MOM wear. The two BAW bearings with high wear showed the greatest conformity at 5 Mc, in apparent contradistinction to classical lubrication theory.

New insights into the structural characteristics of the arabinogalactan-protein (AGP) fraction of gum arabic.

The structural characteristics of the gum exudate of Acacia senegal (gum arabic) have been investigated by monitoring the composition and physicochemical properties before and after treatment with proteolytic enzyme and various alkaline systems. Molecular mass ( M w) and radius of gyration ( R g) measurements were performed using gel permeation chromatography (GPC) coupled to refractive index, UV absorbance, and multiangle light scattering detectors and indicated that the macromolecules present have a compact structure. It was found that treatment with proteolytic enzyme caused the arabinogalactan-protein component (AGP) with average molecular mass approximately 2 x 10 (6) Da to degrade, yielding material of molecular mass approximately 4 x 10 (5) Da, whereas the bulk of the material corresponding to the protein-deficient arabinogalactan component (AG) with molecular mass 4 x 10 (5) remained unaffected. Barium hydroxide was found to hydrolyze the polysaccharide component (AG) itself in addition to the proteinaceous component as demonstrated in control experiments using dextran. However, sodium borohydride/sodium hydroxide treatments were unable to hydrolyze dextran and were assumed to hydrolyze only the proteinaceous component of gum arabic. The AGP component was completely degraded, yielding material of molecular mass approximately 4.5 x 10 (4) Da. It has been concluded, therefore, that the enzyme did not fully hydrolyze all of the protein present and that the AGP component of gum arabic consists of carbohydrate blocks of approximately 4.5 x 10 (4) Da linked to a polypeptide chain consistent with the wattle blossom structure. Because the AGP was degraded to differing extents using a mild and more severe sodium borohydride/sodium hydroxide treatment, it was concluded that the polysaccharide moieties were linked through both O-serine and O-hydroxyproline residues. The gum arabic sample was deglycosylated by treatment with anhydrous hydrogen fluoride and revealed the presence of two putative core proteins of approximately 3 x 10 (4) and approximately 5 x 10 (3) Da, respectively, which correspond to proteins of approximately 250 and 45 amino acids in length. A new model for the structure of the AGP component has been proposed.

"Severe" wear challenge to 36 mm mechanically enhanced highly crosslinked polyethylene hip liners.

Our purpose was to compare the wear performance of mechanically enhanced 5Mrad highly crosslinked polyethylene (MEP, ArComXL) hip liners to (control) 3Mrad UHMWPE liners (ArCom) in 36 mm head size. As a more severe synergy of clinically relevant test models, we contrasted wear with custom roughened Co-Cr surfaces (Ra 500 nm) to the standard pristine Co-Cr heads (Ra < 20 nm) using a severe microseparation test mode in our hip simulator. We adopted a previously published model to estimate potential biological activity. On new Co-Cr heads, the MEP liners showed a 47% reduction in volumetric wear a 13% reduction in wear particle size and a 27% reduction in Functional Biological Activity (FBA) compared to our control. On rough Co-Cr heads, the MEP liners showed little advantage in terms of volumetric wear compared with the control. However, the MEP liners overall showed a 38% reduction in FBA compared to the control owing to a larger volume fraction of larger particles. Thus overall the MEP liners appeared to offer advantages in terms of reduced FBA indices.

Coherent transfer of an optical carrier over 251 km.

We transfer an optical frequency over 251 km of optical fiber with a residual instability of 6x10(-19) at 100 s. This instability and the associated timing jitter are limited fundamentally by the noise on the optical fiber and the link length. We give a simple expression for calculating the achievable instability and jitter over a fiber link. Transfer of optical stability over this long distance requires a highly coherent optical source, provided here by a cw fiber laser locked to a high finesse optical cavity. A sufficient optical carrier signal is delivered to the remote fiber end by incorporating two-way, in-line erbium-doped fiber amplifiers to balance the 62 dB link loss.