Biography:

In the past N. Brown has collaborated on articles with J.S. Clark and V. Degen. One of their most recent publications is Secondary nucleation of aluminium trihydroxide in seeded caustic aluminate solutions. Which was published in journal Journal of Crystal Growth.

More information about N. Brown research including statistics on their citations can be found on their Copernicus Academic profile page.

N. Brown's Articles: (18)

Secondary nucleation of aluminium trihydroxide in seeded caustic aluminate solutions

AbstractScanning electron microscopy shows that secondary nucleation of aluminium trihydroxide in seeded caustic aluminate solutions of industrial composition is closely associated with the crystal growth process via surface nucleation mechanism. When crystallization is preceded by an induction period, the seed crystals develop and give birth to large numbers of secondary nuclei. The role played by impurities normally present in Bayer process solutions is examined and a qualitative mechanism for the secondary nucleation process discussed. Under certain experimental conditions (high supersaturation, absence of impurities), the initial crop of secondary nuclei can grow dendritically. These dendrites can then break away from crystal surfaces to form an additional crop of secondary nuclei.

A quantitative study of new crystal formation in seeded caustic aluminate solutions

AbstractA quantitative study of secondary nucleation of aluminium trihydroxide Al(OH)3 in pure caustic aluminate solutions of Bayer process composition shows that when crystallization is preceded by an induction period (or time lag before crystallization gets underway at the expected rate) a saturation number of nuclei becomes established in a time which is often short compared to the overall growth cycle. Thereafter, the numbers do not increase although the nuclei become larger with growth time. Saturation number N, is correlated with initial supersaturation, S, and the length of the induction period, τ, by the relationship N=KnSτ, where Kn is a constant. Values of Kn calculated at different temperatures cannot be correlated by an Arrhenius type relation. The induction period is correlated with the initial supersaturation by the relation τ=aSb, where a and b are constants for a given temperature and seed surface area. In general, the indiction period decreases with increases in initial supersaturation, temperature and seed surface area. At sufficiently high surface areas there is no measurable induction period and little or no secondary nucleation.

Crystallization of sodium oxalate on metal surfaces

AbstractCrystallization of sodium oxalate in caustic aluminate solutions can occur on metal surfaces provided the supersaturation with respect to sodium oxalate is high enough. Heterogeneous nucleation occurs most readily on polycrystalline surfaces which also provide for strong adherability of the crystalline oxalate. The nature of the sodium oxalate that crystallizes is strongly dependent on the presence in solution of high molecular weight humic-type organics. Not only are the acicular sodium-oxalate “needles” reduced in size, they intergrow and form ball-like structures directly on the metal surface.

Hydrothermal crystallization of α-alumina monohydrate in the presence of copper ions

AbstractThe effect of copper ions on the hydrothermal crystallization of α-alumina monohydrate (A1OOH, mineral name boehmite), following oxidation of the organic carbon compounds in sodium aluminate solution of the Bayer process, has been examined using scanning electron microscopy and particle size analyses. The initial effect of the copper ions on the homogeneously nucleated α-alumina monohydrate is to inhibit crystal growth on the (001) faces and direct the growth process to the prismatic faces of the rhombic or diamond shaped crystals. At low copper levels (up to 0.1 wt% in α-alumina monohydrate), this leads to the formation of plate-like crystals up to 25 μm in size which can intergrow and develop into particles with an average size of up to 100 μm. The size and structure of the μ-alumina monohydrate particles, however, depend on the amount of copper present and increasing copper levels (up to 1.0 wt%) lead progressively to a decrease in average particle size of α-alumina monohydrate to about 10 μm and the formation of more rounded oblong-shaped particles having a compact sheaf-like structure. Copper-containing α-alumina monohydrate particles of this size and form can be readily recovered from the oxidized liquor and recycled in the industrial process.

A study of a dilute concentration of disorder in the β-Cu-Zn superlattice

AbstractA study was made of the disorder quenched in β-Cu-Zn. At low temperatures, 25–250°C, the predominant defect appears to be a wrong pair of Cu and Zn atoms whose observed value of energy of formation is 7.2–8.0 kcal/mol. The energy of motion during reordering is 14kcal/mol. and it appears that a vacancy is trapped in the vicinity of a wrong pair of atoms.

Rotational and vibrational temperatures of BaO from a barium release at 170 km, and the synthetic spectrum of BaO in the region 4700 Å to 15,500 Å

AbstractBand spectra of BaO covering a total wavelength region of 5050 Å-9300 Å were recorded from the ground with a scanning spectrophotometer at 7.1 Å resolution during a series of barium rocket releases at College, Alaska in the Spring of 1969. Rotational and vibrational temperatures, both equal to approximately 850°K at the release altitude of 170 km, were inferred by matching the release spectra with calculated synthetic spectra. This temperature persisted throughout the observing period, from release + 20 sec to 14 min after release.Analysis of the BaO band spectrum over a large wavelength region reveals that rotational temperatures are best determined at wavelengths below 5500 Å, and that vibrational temperatures should be measured at wavelengths greater than 5500 Å. Comparisons with synthetic spectra show that several broad emission features in the release spectra, located at about 7900 Å 8400 Å and 9000 Å, may be identified as clusters of overlapping BaO bands. A synthetic spectrum of BaO extending from 4700 Å to 15,000 Å is included for general reference and to facilitate future studies in that wavelength region.

Polymer paperA fundamental theory for slow crack growth in polyethylene

AbstractThe following theoretical equation has been obtained for measuring the rate of slow crack growth in polyethylene in terms of the crack opening displacement rate δ: δ̇=αy(1−y2)2ηdoE2α2cK4Here δy is the yield point, K is the stress intensity, η is the intrinsic viscosity of the fibrils in the craze, E is Young's modulus, δc is the stress to produce a craze, d0 is the primordial thickness from which the craze originates and γ is Poisson's ratio. The theoretical equation agrees with the experimental observation: δCK4e-−Q/RTThus, for the first time, the dependence of δ on stress and notch depth have been derived in fundamental terms and the physical parameters that constitute the factor C have been identified. The intrinsic viscosity η can be calculated from the theory using specific experimental data. For example at 42°C, the fibrils in a craze in a homopolymer have an intrinsic viscosity of 3 × 1011 Pas. This is much larger than the melt viscosity of the amorphous region, which is about 105–106 Pas. Thus, the resistance of polyethylene to slow crack growth is governed by the crystals and not by the amorphous region.

An interferometer for measuring surveyor's pillars in the open air

AbstractElectronic distance meters are performance tested on a 650 m long baseline at the National Measurement Laboratory, Sydney, Australia. The distances between the pillars which make up the baseline must be measured in a way which is traceable to the international definition of the metre. A laser interferometer has been developed to measure one of the intervals in a very accurate manner. It has some novel features to allow the use of a simple carriage-way to transport the reflector and has demonstrated a measurement accuracy of 0.2 ppm over a distance of 80 m in the open air.

Jet cross sections at leading double logarithm in e+e− annihilation

AbstractWe examine the leading double logarithm structure in the calculation of jet fractions using the JADE algorithm, based on a jet-jet mass cut ys. We find that there is no simple formula allowing us to explicitly sum these logarithms, a necessary procedure if we are to apply perturbation theory in the region y⪡1 where these double logarithms are large. This casts doubt on the usefulness of such an algorithm for comparing the predictions of perturbative QCD with the experimental measurements at small y.

POSTER SESSION: CLINICAL NUTRITION AND FOOD SERVICE MANAGEMENTRelationship of Nutritional Risk to Functional Outcome in Rehabilitation Patients

AbstractLEARNING OUTCOME: To discuss the relationship of nutritional risk to functional outcome and length of stay.OBJECTIVE To compare the level of nutritional risk to functional independence measure (FIM) and length of stay (LOS) outcomes in an acute care rehabilitation unit.METHOD Nutrition screening was completed on all patients upon admission. The level of nutrition risk was determined by selected criteria. Patients were placed in one of three levels: Level I (no nutritional risk), Level II (potential nutritional risk) and Level III (severe or high nutritional risk). The level of nutritional risk was subsequently compared to FIM level and LOS.SUBJECTS Subjects consisted of 100 consecutive admissions to an acute care hospital's rehabilitation unit over a three month time period. Admission diagnoses included orthopedic, cardiac and neurological impairment.OUTCOMES Measured outcomes included FIM (as determined by a physical or occupational therapist) and LOS.STATISTICAL ANALYSIS Data was analyzed using one-way ANOVA.RESULTSCONCLUSIONS The results suggest an association between functional outcome and nutritional risk

Spectral imaging system for non-contact colour measurement

AbstractThis paper describes the development of a non-contact system for measuring colour of printed material at web speeds. The system proposed uses a non-contact spectrophotometer based on a holographic grating, in conjunction with a conventional monochrome area scan camera, from which colour spectral data is extracted, whilst a xenon flash is used to illuminate colour samples. Software and hardware details of the system are given, along with the underlying mathematics for colour space conversion and measurement. Conversion equations from X,Y,Z chromaticity co-ordinates to the RGB system are presented, and also equations to convert from the L∗a∗b∗ colour space to X,Y,Z chromaticity co-ordinates. Experimental results are presented whereby the non-contact spectral system is shown to perform to a colour tolerance exceeding that of conventional colour video systems.

Short communicationAntivenom: The most cost-effective treatment in the world?

AbstractAntivenom is the only effective treatment for envenoming by snakes, scorpions and other venomous creatures. Unfortunately, supplies of this life-saving drug in many countries are critically low, and the tragic consequence of untreated envenoming exacts a chronic humanitarian and economic burden on those communities affected. This neglected health crisis struggles to compete with higher profile illnesses for recognition, research attention and funding. Sound strategies to improve the provision of antivenoms repeatedly fail because of an inability to attract the requisite financial investment. In the highly competitive international health landscape, the greatest challenge for stakeholders is to demonstrate that antivenom constitutes an affordable, cost-effective and worthwhile investment of healthcare resources. Recent collaborations in the UK, Africa and South America, have proven that lowering the production costs of antivenom to affordable levels is sustainable. A simple healthcare-economic calculation can be used to demonstrate the superior cost-effectiveness of antivenoms in preventing death and disability. These advances may lead to antivenom becoming one of the most cost-effective treatments available to modern medicine, and provides strong justification for its inclusion in international health funding initiatives.

Adult urologyClinical implication of routine stone culture in percutaneous nephrolithotomy—a prospective study

AbstractObjectivesTo evaluate the correlation between preoperative urine culture (UC) and intraoperative stone culture (SC) and the impact of SC findings on clinical decisions.MethodsUC and intraoperative fragmented SC were prospectively obtained in all patients undergoing percutaneous nephrolithotomy between January 2004 and March 2005. Patients with a positive UC received a full course of antibiotics before surgery. All postoperative systemic inflammatory response syndrome (SIRS) events were recorded, as was the antibiotic regimen used and any changes in antibiotic treatment secondary to the SC results.ResultsThe study group consisted of 75 consecutive patients. Of these 75 patients, 33 (49%) had sterile UC and SC results. Both urine and renal stones were colonized in 17 patients (24%); in 6 of them, the UC and SC showed different pathogens. A colonized SC associated with a sterile UC was found in 19 patients (25%). The calculated UC sensitivity, specificity, and positive and negative predictive value for the detection of stone colonization was 30%, 94%, and 84% and 58%, respectively. Seventeen patients (22%) had postoperative SIRS. In 13 of them, a change in antibiotic treatment was made according to the SC findings. On univariate analysis, the incidence of SIRS was not related to the length of the operation, stone-free rate, or supracostal or infracostal access. The relative risk of SIRS when the SC was positive was 3.6.ConclusionsRenal calculi pathogens are one of the predisposing factors for infectious events; however, preoperative UC often fails to grow stone-colonizing bacteria. Intraoperative SC may be essential in directing the antibiotic regimen postoperatively and should be routinely used.

Live cell detection of chromosome 2 deletion and Sfpi1/PU1 loss in radiation-induced mouse acute myeloid leukaemia

AbstractThe CBA/H mouse model of radiation-induced acute myeloid leukaemia (rAML) has been studied for decades to bring to light the molecular mechanisms associated with multistage carcinogenesis. A specific interstitial deletion of chromosome 2 found in a high proportion of rAML is recognised as the initiating event. The deletion leads to the loss of Sfpi, a gene essential for haematopoietic development. Its product, the transcription factor PU.1 acts as a tumour suppressor in this model. Although the deletion can be detected early following ionising radiation exposure by cytogenetic techniques, precise characterisation of the haematopoietic cells carrying the deletion and the study of their fate in vivo cannot be achieved. Here, using a genetically engineered C57BL/6 mouse model expressing the GFP fluorescent molecule under the control of the Sfpi1 promoter, which we have bred onto the rAML-susceptible CBA/H strain, we demonstrate that GFP expression did not interfere with X-ray induced leukaemia incidence and that GFP fluorescence in live leukaemic cells is a surrogate marker of radiation-induced chromosome 2 deletions with or without point mutations on the remaining allele of the Sfpi1 gene. This study presents the first experimental evidence for the detection of this leukaemia initiating event in live leukemic cells.

Case ReportThe value of follow-up after acute Q fever infection

SummaryThis is a case report of a 53-year-old woman involved in an outbreak of Q fever, in whom Q fever endocarditis was diagnosed 18 months after acute Q fever infection. At the time of diagnosis, she was completely asymptomatic and without screening for chronic Q fever, this severe potentially life-threatening infection would probably not have been recognised until significant valvular destruction had taken place. Early diagnosis enabled prompt, potentially curative medical treatment to start without the need for valvular heart surgery. The authors advocate that serological monitoring should be carried out every 4 months for a period of 2 years after acute Q fever and patients with high phase 1 IgG titres (>800) be investigated further and/or followed more closely depending on the clinical scenario.The case report also discusses the use of complement fixation testing in the diagnosis of Q fever endocarditis. The authors recommend that in cases of culture negative endocarditis, a single negative complement fixation test is not sufficient to exclude the diagnosis of Q fever endocarditis. Micro-immunofluorescence or repeat complement fixation testing is recommended when Q fever endocarditis is suspected clinically.

High energy gamma-ray spectroscopy with LaBr3 scintillation detectors

AbstractLanthanum bromide scintillation detectors produce very high light outputs (∼60,000 ph/MeV) within a very short decay time (typically ∼20 ns) which means that high instantaneous currents can be generated in the photocathode and dynode chain of the photomultiplier tube (PMT) used for the scintillation readout. The net result is that signal saturation can occur long before the recommended PMT biasing conditions can be reached.In search of an optimized light readout system for LaBr3, we have tested and compared two different PMT configurations for detection of gamma-rays up to 15 MeV. This range was chosen as being appropriate for gamma-ray remote sensing and medium energy nuclear physics applications. The experiments were conducted at two facilities: the Laboratori Nazionali del Sud (LNS) in Catania, Italy [1] and the High Intensity Gamma-ray Source (HIγS) at Triangle University Nuclear Laboratory, in Durham, North Carolina, USA [2].The PMT configurations we have tested are (1) a standard dynode chain operated under-biased; (2) a 4-stage reduced chain operated at nominal inter-dynode bias.The results are that shortening the number of active stages, as in configuration (2), has advantages in preserving energy resolution and avoiding PMT saturation over a large energy range.However, the use of an under-biased PMT, configuration (1), can still be considered a satisfactory solution, at least in the case of PMTs manufactured by Photonis.The results of this study will be used in support of the Mercury Gamma-ray and Neutron Spectrometer (MGNS) on board of BepiColombo, the joint ESA/JAXA mission to Mercury, scheduled for launch in 2014.

Short communicationImpact of recent antibiotics on nasopharyngeal carriage and lower airway infection in Indigenous Australian children with non-cystic fibrosis bronchiectasis

AbstractIndigenous Australian children have increased rates of bronchiectasis. Despite a lack of high-level evidence on effectiveness and antibiotic resistance, these children often receive long-term antibiotics. In this study, we determined the impact of recent macrolide (primarily azithromycin) and β-lactam antibiotic use on nasopharyngeal colonisation, lower airway infection (>104 CFU/mL of bronchoalveolar lavage fluid culture) and antibiotic resistance in non-typeable Haemophilus influenzae (NTHi), Streptococcus pneumoniae and Moraxella catarrhalis isolates from 104 Indigenous children with radiographically confirmed bronchiectasis. Recent antibiotic use was associated with significantly reduced nasopharyngeal carriage, especially of S. pneumoniae in 39 children who received macrolides [odds ratio (OR) = 0.22, 95% confidence interval (CI) 0.08–0.63] and 26 children who received β-lactams (OR = 0.07, 95% CI 0.01–0.32), but had no significant effect on lower airway infection involving any of the three pathogens. Children given macrolides were significantly more likely to carry (OR = 4.58, 95% CI 1.14–21.7) and be infected by (OR = 8.13, 95% CI 1.47–81.3) azithromycin-resistant S. pneumoniae. Children who received β-lactam antibiotics may be more likely to have lower airway infection with β-lactamase-positive ampicillin-resistant NTHi (OR = 4.40, 95% CI 0.85–23.9). The risk of lower airway infection by antibiotic-resistant pathogens in children receiving antibiotics is of concern. Clinical trials to determine the overall benefit of long-term antibiotic therapy are underway.

Review articleDiagnostic accuracy of Magnetic Resonance Imaging using liver tissue specific contrast agents and contrast enhanced Multi Detector Computed Tomography: A systematic review of diagnostic test in Hepatocellular Carcinoma (HCC)

Highlights•Hepatocellular Carcinoma is the most common global primary liver cancer in persons with chronic liver disease.•Gadoxetetic acid enhanced MRI is more sensitive in diagnosing HCC compared to contrast enhanced MDCT.•There is no difference in specificity between gadoxetetic acid enhanced MRI and contrast enhanced MDCT.•Combination of 3T MRI and gadoxetetic acid (Gd-EOBDTPA) has further improved diagnostic accuracy of HCC.

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