PubMed Health⌕ Search

Biomedical subjects

P M Davidson

Publications and source records attributed to P M Davidson.

At least 19 recordsLinked to original sources
PubMed2006

Probing shell structure and shape changes in neutron-rich sulfur isotopes through transient-field g-factor measurements on fast radioactive beams of 38S and 40S.

The shell structure underlying shape changes in neutron-rich nuclei near N = 28 has been investigated by a novel application of the transient-field technique to measure the first-excited-state g factors in 38S and 40S produced as fast radioactive beams. There is a fine balance between proton and neutron contributions to the magnetic moments in both nuclei. The g factor of deformed 40S does not resemble that of a conventional collective nucleus because spin contributions are more important than usual.

Journal Article↗
PubMed2006

Clinical leadership in contemporary clinical practice: implications for nursing in Australia.

BACKGROUND: Leadership in the clinical practice environment is important to ensure both optimal patient outcomes and successive generations of motivated and enthusiastic clinicians. AIM: The present paper seeks to define and describe clinical leadership and identify the facilitators and barriers to clinical leadership. We also describe strategies to develop clinical leaders in Australia. Key drivers to the development of nursing leaders are strategies that recognize and value clinical expertise. These include models of care that highlight the importance of the nursing role; evidence-based practice and measurement of clinical outcomes; strategies to empower clinicians and mechanisms to ensure participation in clinical decision-making. KEY ISSUES: Significant barriers to clinical leadership are organizational structures that preclude nurses from clinical decision making; the national shortage of nurses; fiscal constraints; absence of well evaluated models of care and trends towards less skilled clinicians. CONCLUSIONS: Systematic, strategic initiatives are required to nurture and develop clinical leaders. These strategies need to be collegial collaborations between the academic and health care sectors in order to provide a united voice for advancing the nursing profession.

Australia↗
PubMed2005

Excitation energies of superdeformed States in 196Pb: towards a systematic study of the second well in Pb isotopes.

The excitation energy of the lowest-energy superdeformed band in 196Pb is established using the techniques of time-correlated gamma-ray spectroscopy. Together with previous measurements on 192Pb and 194Pb, this result allows superdeformed excitation energies, binding energies, and two-proton and two-neutron separation energies to be studied systematically, providing stringent tests for current nuclear models. The results are examined for evidence of a "superdeformed shell gap."

Journal Article↗
PubMed2004

Antimicrobial activity of ultrasound-assisted solvent-extracted spices.

AIMS: The objective of this research was to determine the antimicrobial activity of conventional and high-intensity ultrasound-assisted (HI-US) solvent-extracted Thai spices, including ginger (Zingiber officinale Rose), fingerroot (Bosenbergia pandurata Holtt) and turmeric (Curouma longa Linn). METHODS AND RESULTS: Extracts were obtained using hexane, isopropanol and a 7 : 3 isopropanol : hexane mixture as solvents with and without HI-US. The antimicrobial activity of the extracts was assayed against four strains each of Listeria monocytogenes and Salmonella Typhimurium DT 104 using an agar dilution assay. Application of HI-US did not alter antibacterial activity against S. Typhimurium, but antilisterial activity of some HI-US spice extracts decreased. Solvent type affected antimicrobial efficacy of extracts with hexane producing the least antimicrobial activity. Fingerroot extracted with isopropanol-hexane and without HI-US had the best antilisterial effect while HI-US-isopropanol fingerroot extract had the greatest antimicrobial efficacy against S. Typhimurium. CONCLUSIONS: Application of HI-US reduced time of extraction to 5 min, compared with the 24 h required for conventional extraction and maintained antimicrobial activity against Salmonella but slightly reduced activity against Listeria. SIGNIFICANCE AND IMPACT OF THE STUDY: HI-US in combination with proper solvent selection may offer a new tool to optimize extraction of spice essential oil for use as antimicrobial agents, and reduce processing time and costs.

2-Propanol↗
PubMed2004

Cations reduce antimicrobial efficacy of lysozyme-chelator combinations.

Reduction of the antimicrobial efficacy of lysozyme-chelator combinations against two Escherichia coli O157:H7 strains on addition of mineral salts was studied. The objective of the study was to determine the effect of type and concentration of mono-, di-, and trivalent mineral salts on the antimicrobial effectiveness of lysozyme and various chelators against E. coli O157:H7. Seven salts (Al3+, Ca2+, Fe2+, Fe3+, K+, Mg2+, and Na+) at 1 to 10 mM were added to aqueous solutions of lysozyme and disodium ethylenediamine tetraacetic acid (EDTA), disodium pyrophosphate (DSPP), or pentasodium tripolyphosphate (PSTPP) at pH 6, 7, or 8 and applied to cultures of E. coli O157:H7 strains 932 and H1730. Inhibitory activity of lysozyme chelator combinations against both strains was completely lost after addition of > or = 1 mM Ca2+ and Mg2+ at pH 7 and 8. At pH 6, antimicrobial activity of lysozyme-EDTA against both strains was retained in the presence of calcium or magnesium cations. DSPP-lysozyme inhibited strain H1730 at pH 6 despite the presence of Mg2+. Concentrations above 4 mM Fe2+ neutralized activity of all lysozyme-chelator combinations. Reversal of inhibition by lysozyme-chelator complexes by the monovalent Na+ and K+ ions depended on E. coli O157:H7 strain type. Neither monovalent cation reversed inhibition of strain 932. However, Na+ and K+ reversed lysozyme-chelator inhibition of strain H1730. The addition of > or = 1 mM Fe3+ or Al3+ was effective in reversing inhibition of both strains by lysozyme and EDTA at pH 6, 7, and 8. Isothermal titration calorimetry was used to determine the amount of ion-specific competitive binding of free cations by EDTA-lysozyme combinations. A mechanistic model for the antimicrobial functionality of chelator-lysozyme combinations is proposed.

Anti-Infective Agents↗
PubMed2004

Molecular weight of chitosan influences antimicrobial activity in oil-in-water emulsions.

The objective of this study was to evaluate the antimicrobial efficiency of chitosans in oil-in-water emulsions. Model emulsions were prepared with 20% corn oil, 1.5% Tween 20, 1.5% Trypticase soy broth, 0.58% acetic acid, and chitosan polysaccharide or chitosan oligosaccharide in concentrations of 0, 0.1, 0.2, 0.5, and 0.7%. A control containing HCl was included to determine the role of acetic acid in the overall antibacterial activity. The pH of samples and controls was adjusted to 4.5. Emulsions were inoculated with Listeria monocytogenes (strains Scott A and 310) or Salmonella Typhimurium DT104 (strains 2486 and 2576) at a level of 10(7) CFU/ml. Inoculated emulsions were incubated at 10 and 25 degrees C for 4 days and analyzed for bacterial count every 24 h. Both tested Salmonella strains were more susceptible to acetic acid than Listeria. However, L. monocytogenes was more affected by chitosan than either Salmonella strain. During the storage at 25 degrees C, initial inoculum in the emulsions with 0.58% acetic acid and 0.1% chitosan polysaccharide was reduced to below the detection limits after 24, 48, 72, or 96 h for L. monocytogenes 310, Salmonella Typhimurium DT104 2576, Salmonella Typhimurium DT104 2486, or L. monocytogenes Scott A, respectively. Chitosan oligosaccharide was less effective against all tested bacteria and showed a concentration-dependent effect. The antimicrobial efficacy of chitosan was reduced at 10 degrees C, and reduction of microbial loads was delayed for approximately 24 h compared with 25 degrees C. Results suggest that addition of 0.1% chitosan polysaccharide would be sufficient to ensure the microbial safety of oil-in-water emulsions regardless of storage temperature.

Anti-Bacterial Agents↗
PubMed2003

Direct decays from superdeformed states in 192Pb observed using time-correlated gamma-ray spectroscopy.

Correlations of decays above and below isomeric states in the normally deformed minimum of 192Pb have been used to identify discrete transitions in the decay of the superdeformed (SD) band. The data establish the absolute excitation energy of the lowest observed SD level as 4.425 MeV. Extrapolation to the bandhead indicates that the excitation energy of the superdeformed well in 192Pb is 0.5 MeV lower than in the heavier isotope 194Pb. The results confirm the trend to decreasing excitation energy with decreasing neutron number predicted by both a macroscopic Strutinsky method approach and microscopic mean field calculations.

Journal Article↗
PubMed2003

Enhanced inhibition of Escherichia coli O157:H7 by lysozyme and chelators.

This study examined the effects of three chelating agents (EDTA, disodium pyrophosphate [DSPP], and pentasodium tripolyphosphate [PSTPP]) on the inhibition of the growth of Escherichia coli O157:H7 by lysozyme. The objective of this study was to identify replacement chelators that exhibit synergistic properties similar to those of EDTA. The inhibitory effects of EDTA at 300 to 1,500 microg/ml and of DSPP and PSTPP at 3,000 to 15,000 microg/ml in combination with lysozyme at 200 to 600 microg/ml for up to 48 h at pHs of 6.0, 7.0, and 8.0 on four strains of E. coli O157:H7 was studied with the use of a microbroth dilution assay. The addition of EDTA enhanced lysozyme's inhibitory effect on strains of E. coli O157:H7. EDTA at > or = 300 microg/ml combined with lysozyme at 200 to 600 microg/ml was sufficient to inhibit the growth of the strains at pHs of 6.0 and 8.0. At pH 7.0, lysozyme at 200 to 600 microg/ml and EDTA concentrations of > or = 1,000 microg/ml were effective in inhibiting three of the four strains. DSPP at pH 6.0 was inhibitory at > or = 10,000 microg/ml when combined with lysozyme at 200 to 300 microg/ml. In contrast, PSTPP increased the inhibitory activity of lysozyme more effectively at pH 8.0. Lysozyme at 200 to 600 microg/ml was effective against two strains of E. coli O157:H7 when used in conjunction with PSTPP at > or = 5,000 microg/ml. The remaining strains were inhibited by PSTPP at > or = 10,000 microg/ml. Our results indicate that inhibition occurred with each lysozyme-chelator combination, but the concentrations of phosphates required to increase the antimicrobial spectrum of lysozyme against E. coli O157:H7 were higher than the EDTA concentrations required to achieve the same effect.

Anti-Infective Agents↗
PubMed2002

Growth of Escherichia coli O157:H7, Salmonella typhimurium DT104, and Listeria monocytogenes in dark cutting beef at 10 or 22 degrees C.

An experiment was conducted to determine the effects of the dark, firm, and dry (DFD) condition of beef on growth of the foodborne pathogens Escherichia coli O157:H7, Salmonella Typhimurium DT104, and Listeria monocytogenes Scott A in ground beef. Longissimus muscles from a DFD carcass (pH = 6.45) and normal carcass (N; pH = 5.64) were ground and samples obtained (100 and 0% DFD, respectively). Equal amounts of the 0 and 100% DFD ground samples were mixed to obtain 50% DFD samples. Inoculated 0, 50, and 100% DFD samples were packaged into oxygen-permeable overwrap and stored at 10 degrees C for E. coli O157:H7, Salmonella Typhimurium DT104, and L. monocytogenes Scott A or at 22 degrees C for E. coli O157:H7. Growth characteristics of E. coli O157:H7, Salmonella Typhimurium DT104, and L. monocytogenes Scott A did not differ (P > 0.05) between 0 and 100% DFD. Results indicated that the DFD beef used in this study was no more susceptible to growth of E. coli O157:H7, Salmonella Typhimurium, or L. monocytogenes Scott A than N beef.

Animals↗
PubMed2001

Antibacterial activity in extracts of Camellia japonica L. petals and its application to a model food system.

The potential presence of naturally occurring antimicrobials in petals of Camellia japonica L., a member of the tea family, was investigated against foodborne pathogens in microbiological media and food. Petals of the camellia flower (C. japonica L.) were extracted with methanol and fractionated into basic, acidic, and neutral fractions. The acidic fraction (equivalent to 1.0 g of raw sample per disk) produced an inhibitory zone of 14 to 19 mm (diameter) in a disk assay against the pathogens Salmonella Typhimurium DT104, Escherichia coli O157:H7, Listeria monocytogenes, and Staphylococcus aureus on agar plates. Silica gel adsorption column chromatography, Sephadex LH-20 column chromatography, and preparative purification by high-pressure liquid chromatography were used to purify compounds in the fraction. The mass spectrum of the antibacterial compound isolated had a molecular ion (M+) of m/z 116 and showed good conformity with the spectrum of fumaric acid (HOOC-CH=CH-COOH). An aqueous extract from the petals of C. japonica L. had an inhibitory effect on growth of all pathogens at 37 degrees C in microbiological media by increasing the lag phase. None of the microorganisms was inhibited completely. Milk was used as a model food system. Aqueous extract at a concentration of 100 mg/ml was bacteriostatic against all the foodborne pathogens in the milk stored at 25 degrees C for up to 4 days.

Animals↗
PubMed2000

Randomised controlled trial of ultrasonography in diagnosis of acute appendicitis, incorporating the Alvarado score.

OBJECTIVES: To determine whether diagnosis by graded compression ultrasonography improves clinical outcomes for patients with suspected appendicitis. DESIGN: A randomised controlled trial comparing clinical diagnosis (control) with a diagnostic protocol incorporating ultrasonography and the Alvarado score (intervention group). SETTING: Single tertiary referral centre. PARTICIPANTS: 302 patients (age 5-82 years) referred to the surgical service with suspected appendicitis. 160 patients were randomised to the intervention group, of whom 129 underwent ultrasonography. Ultrasonography was omitted for patients with extreme Alvarado scores (1-3, 9, or 10) unless requested by the admitting surgical team. MAIN OUTCOME MEASURES: Time to operation, duration of hospital stay, and adverse outcomes, including non-therapeutic operations and delayed treatment in association with perforation. RESULTS: Sensitivity and specificity of ultrasonography were measured at 94. 7% and 88.9%, respectively. Patients in the intervention group who underwent therapeutic operation had a significantly shorter mean time to operation than patients in the control group (7.0 v 10.2 hours, P=0.016). There were no differences between groups in mean duration of hospital stay (53.4 v 54.5 hours, P=0.84), proportion of patients undergoing a non-therapeutic operation (9% v 11%, P=0.59) or delayed treatment in association with perforation (3% v 1%, P=0.45). CONCLUSION: Graded compression ultrasonography is an accurate procedure that leads to the prompt diagnosis and early treatment of many cases of appendicitis, although it does not prevent adverse outcomes or reduce length of hospital stay.

Acute Disease↗
PubMed2000

Activity of hydrolysed lactoferrin against foodborne pathogenic bacteria in growth media: the effect of EDTA.

Lactoferrin was hydrolysed with pepsin and the antimicrobial activity of the resulting hydrolysate (HLF) was studied in 1% peptone, 0.05% yeast extract, 1% glucose (PYG) medium and tryptic soy broth (TSB). HLF was effective against Listeria monocytogenes, enterohaemorrhagic Escherichia coli and Salmonella enteritidis in PYG, however, the highest studied concentration (1.6 mg ml-1) did not inhibit growth of any of these organisms in TSB. The addition of EDTA enhanced the activity of HLF in TSB, indicating that the decreased activity of HLF may have been due, in part, to excess cations in the medium.

Animals↗
PubMed2000

Inguinoscrotal bruising: a sign of neonatal adrenal hemorrhage.

A 5-day-old baby presented with right inguinoscrotal bruising. The underlying testis and cord were normal on examination. Intra-abdominal bleeding was suspected. Abdominal ultrasound showed right adrenal hemorrhage. This was managed nonoperatively and with supportive therapy; the inguinoscrotal bruising resolved spontaneously.

Adrenal Gland Diseases↗
PubMed2000

Microbiology of potatoes and potato products: a review.

Many types of spoilage and pathogenic microorganisms exist on fresh, minimally processed, and fully processed potato products. Potatoes are processed into many products including frozen, dried, ready-to-eat, and minimally processed. The microbiological quality of finished potato products is influenced by the natural microflora, processing, handling, and human contact. The natural microflora of potatoes are influenced by soil and airborne inocula, agricultural practices, harvesting methods, and storage conditions. The microflora of processed products are influenced by all of the factors and conditions affecting the natural microflora as well as the processes applied to the product. Increased consumer demand for new and existing potato products highlights the importance of ensuring their microbiological safety. This review considers the sources of microorganisms, microflora, foodborne disease pathogens, and outbreaks associated with, and selected microbiological research involving, potatoes and potato products.

Consumer Advocacy↗
PubMed1999

Graded compression ultrasonography in the assessment of the "tough decision" acute abdomen in childhood.

The diagnosis of acute appendicitis in childhood is frequently difficult. In some situations the need to operate is clear, but in others the decisions may be much "tougher" because the clinical findings are equivocal. This is a retrospective study of a consecutive series of 253 children presenting with "acute abdominal pain? appendicitis" who had graded compression ultrasonography (GCUS) because the clinical scenario did not warrant immediate laparotomy. This represents 30% of all cases seen in the study period. The aim of the study was to examine the role of GCUS and a clinical scoring system (the Alvarado score) in patients in whom the diagnosis is uncertain.

Abdomen, Acute↗
PubMed1998

The experiences of female spouses of survivors of acute myocardial infarction: a pilot study of Lebanese-born women in south-western Sydney, Australia.

Lebanese migrants form a significant proportion of the population in southwestern Sydney (SWS), and in New South Wales, Australia. This pilot study was undertaken in south-western Sydney, a rapidly expanding and socioeconomically disadvantaged region, to explore the experiences of English speaking women of Lebanese origin whose spouses had recently experienced an acute myocardial infarction (AMI). Semi-structured interviews were conducted with seven Lebanese-born women at 2- and 4-week intervals, following the discharge of their husbands from hospital. Qualitative analysis of narrative text revealed four distinct themes. These were: struggle to resolve distress; intensive monitoring of the AMI survivor; searching for avenues of support; and reflecting on the future. Study findings are discussed in relation to the literature. Implications for nursing practice and research are drawn from study findings.

Adaptation, Psychological↗
PubMed1998

Effect of oscillatory high hydrostatic pressure treatments on Byssochlamys nivea ascospores suspended in fruit juice concentrates.

The effect of continuous (689 MPa with holding times of 5, 15 or 25 min) and oscillatory (one, three or five cycles at 689 MPa with holding times of 1 s) high hydrostatic pressure treatments on the viability of Byssochlamys nivea ascospores suspended in apple and cranberry juice concentrates adjusted by dilution to water activities (aw) of 0.98 and 0.94 was evaluated at 21 and 60 degrees C. Inactivation of the initial spore inocula was achieved after three or five cycles of oscillatory pressurization at 60 degrees C when the aw was 0.98 in both fruit juices. With aw 0.94, the initial inocula were reduced by less than 1 log-cycle after five pressure cycles. Inactivation was not observed within 25 min with continuous pressurization at 60 degrees C. In treatments at 21 degrees C, no effect on spore viability was observed with continuous or oscillatory treatments.

Ascomycota↗