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Biomedical subjects

A J Daley

Publications and source records attributed to A J Daley.

At least 19 recordsLinked to original sources
PubMed2006

Dark-state cooling of atoms by superfluid immersion.

We propose and analyze a scheme to cool atoms in an optical lattice to ultralow temperatures within a Bloch band and away from commensurate filling. The protocol is inspired by ideas from dark-state laser cooling but replaces electronic states with motional levels and spontaneous emission of photons by emission of phonons into a Bose-Einstein condensate, in which the lattice is immersed. In our model, achievable temperatures correspond to a small fraction of the Bloch bandwidth and are much lower than the reservoir temperature. This is also a novel realization of an open quantum optical system, where known tools are combined with new ideas involving cooling via a reservoir.

Journal Article↗
PubMed2006

Repulsively bound atom pairs in an optical lattice.

Throughout physics, stable composite objects are usually formed by way of attractive forces, which allow the constituents to lower their energy by binding together. Repulsive forces separate particles in free space. However, in a structured environment such as a periodic potential and in the absence of dissipation, stable composite objects can exist even for repulsive interactions. Here we report the observation of such an exotic bound state, which comprises a pair of ultracold rubidium atoms in an optical lattice. Consistent with our theoretical analysis, these repulsively bound pairs exhibit long lifetimes, even under conditions when they collide with one another. Signatures of the pairs are also recognized in the characteristic momentum distribution and through spectroscopic measurements. There is no analogue in traditional condensed matter systems of such repulsively bound pairs, owing to the presence of strong decay channels. Our results exemplify the strong correspondence between the optical lattice physics of ultracold bosonic atoms and the Bose-Hubbard model-a link that is vital for future applications of these systems to the study of strongly correlated condensed matter and to quantum information.

Journal Article↗
PubMed2006

Coagulase-negative staphylococci in very-low-birth-weight infants: inability of genetic markers to distinguish invasive strains from blood culture contaminants.

Selected coagulase-negative staphylococci from the blood of very-low-birth-weight infants in the Neonatal Intensive Care Unit at the Royal Women's Hospital, Melbourne, collected over a 5-year period were examined. Isolates were classified as invasive or contaminants, speciated, typed by pulsed-field gel electrophoresis, and examined for biofilm genes (icaA, icaC, and icaD), adhesion genes (atlE, fbe), and the number of copies of IS256. Of the 24 isolates studied, there were 13 contaminants and 11 invasive isolates. The collection included 15 Staphylococcus epidermidis, eight Staphylococcus capitis, and one each of Staphylococcus warneri and Staphylococcus haemolyticus. Two small clusters of S. epidermidis that belonged to the same molecular type were identified. All S. capitis isolates belonged to the same molecular type or subtype, suggesting that a particular clone was circulating in the unit. There was no significant difference in the species found, the presence of icaA, icaC, icaD, atlE, or fbe, or the number of copies of IS256 between invasive isolates and contaminants. A series of nasal isolates from nonhospitalized adults differed from hospital isolates in the absence of IS256 and the low prevalence of icaC. There was no evidence of IS256-mediated insertion into ica genes as a mechanism of phase variation. These findings suggest that contaminants and invasive isolates derived from the same pool of hospital strains capable of causing sepsis in compromised hosts and that other mechanisms of phase variation exist, apart from IS256 insertion into ica genes.

Biofilms↗
PubMed2005

What is the best screening method to detect Serratia marcescens colonization during an outbreak in a neonatal intensive care nursery?

Serratia marcescens can cause outbreaks in neonatal intensive care units (NICUs), but the optimum method of screening for carriage has not been determined in this group of patients. During an outbreak of S. marcescens infections across two geographically distinct NICUs, babies were screened for both respiratory and gastrointestinal carriage. A total of 58 babies were colonized (N = 47) or infected (N = 11) with S. marcescens over a nine-month period. Forty-four colonized babies had paired respiratory and gastrointestinal tract specimens collected. Of these, 39% were positive from the gastrointestinal tract and 22% from respiratory tract specimens alone, and 39% had growth from both sites. Enrichment prior to inoculation on to solid media increased the detection of respiratory tract carriers. During an outbreak of S. marcescens, both respiratory and gastrointestinal samples should be collected in order to maximize the identification of colonized infants. Broth enrichment adds an additional day to obtaining results but increases the yield of positive results from respiratory specimens.

Australia↗
PubMed2005

Early onset neonatal meningitis in Australia and New Zealand, 1992-2002.

OBJECTIVES: To study the epidemiology of early onset neonatal bacterial meningitis (EONBM) in Australasia. DESIGN: Prospective surveillance study, 1992-2002, in 20 neonatal units in Australia and New Zealand. EONBM was defined as meningitis occurring within 48 hours of delivery. RESULTS: There were 852 babies with early onset sepsis, of whom 78 (9.2%) had EONBM. The incidence of early onset group B streptococcal meningitis fell significantly from a peak of 0.24/1000 live births in 1993 to 0.03/1000 in 2002 (p trend = 0.002). There was no significant change over time in the incidence of Escherichia coli meningitis. The rate of EONBM in very low birthweight babies was 1.09/1000 compared with the rate in all infants of 0.11/1000. The overall rate of EONBM was 0.41/1000 in 1992 and 0.06 in 2001, but this trend was not significant (p trend = 0.07). Case-fatality rates for EONBM did not change significantly with time. Birth weight <1500 g (odds ratio (OR) 7.2 (95% confidence interval (CI) 4.8 to 10.9)) and Gram negative bacillary meningitis (OR 3.3 (95% CI 2.2 to 4.9)) were significant risk factors for mortality. Sixty two percent of the 129 babies who died from early onset sepsis or suspected sepsis did not have a lumbar puncture performed. CONCLUSION: The incidence of early onset group B streptococcal meningitis has fallen, probably because of maternal intrapartum antibiotic prophylaxis, without a corresponding change in E. coli meningitis. Gram negative bacillary meningitis still carries a worse prognosis than meningitis with a Gram positive organism.

Age of Onset↗
PubMed2004

Single atom transistor in a 1D optical lattice.

We propose a scheme utilizing a quantum interference phenomenon to switch the transport of atoms in a 1D optical lattice through a site containing an impurity atom. The impurity represents a qubit which in one spin state is transparent to the probe atoms, but in the other acts as a single atom mirror. This allows a single-shot quantum nondemolition measurement of the qubit spin.

Journal Article↗
PubMed2004

Prevention of neonatal group B streptococcal disease: progress, challenges and dilemmas.

Significant advances in the prevention of neonatal group B streptococcal (GBS) disease have occurred in the last decade. In Australia, as well as in centres overseas, intrapartum penicillin given to carrier mothers has been shown to unequivocally decrease early onset neonatal GBS sepsis. In choosing which women should receive intrapartum chemoprophylaxis, recent data suggest that screening programmes for the detection of GBS carriage may be more effective than risk-based strategies to prevent early onset neonatal GBS sepsis. Combined vaginal and rectal swabs, collected between 35 and 37 weeks gestation, either by a health care worker or by the patient herself and inoculated onto selective media after enrichment provide the optimum conditions to detect carriage. Increasingly erythromycin and clindamycin resistance is being described overseas, which may influence the choice of antibiotics used in those allergic to penicillin. Widespread antibiotic use, particularly with broad-spectrum agents, may lead to increasing neonatal sepsis with ampicillin resistant organisms. Whilst rates of non-GBS neonatal sepsis are generally stable there is evidence suggesting that Escherichia coli sepsis in premature infants is increasing. Novel vaccination strategies for GBS are being developed that may ultimately provide broader protection for mothers and babies and eliminate the need for intrapartum antibiotics.

Anti-Bacterial Agents↗
PubMed2003

Defect-suppressed atomic crystals in an optical lattice.

We present a coherent filtering scheme which dramatically reduces the site occupation number defects for atoms in an optical lattice by transferring a chosen number of atoms to a different internal state via adiabatic passage. With the addition of superlattices it is possible to engineer states with a specific number of atoms per site (atomic crystals), which are required for quantum computation and the realization of models from condensed matter physics, including doping and spatial patterns. The same techniques can be used to measure two-body spatial correlation functions.

Journal Article↗
PubMed2003

Subjective exercise experiences during and after high and low intensity exercise in active and inactive adult females. Some preliminary findings.

AIM: To investigate the relationship between subjective exercise experiences and exercise intensity in active and inactive females. METHODS: Participants consisted of 8 inactive and 8 active female volunteers who completed the Subjective Exercise Experience Scale pre-exercise, 10 min during and 5 min after low and high intensity exercise. RESULTS: A series of 2x2x3 (Group x Condition x Time) between-participants repeated measures analysis of variance revealed a significant Condition x Time interaction for Psychological Well-being scores (p<0.01). During exercise participants reported significantly higher Psychological Well-being scores in the low intensity compared to high intensity exercise condition. In the high intensity exercise condition participants reported higher Psychological Well-being scores per exercise than before or during exercise. Time main effects were also recorded for Psychological Well-being (p<0.05) and Psychological Distress scores (p<0.05). CONCLUSION: These preliminary findings indicate that exercise may positively influence psychological states irrespective of participants' activity status.

Adult↗
PubMed2002

Early time diffusion for the quantum kicked rotor with narrow initial momentum distributions.

We investigate analytically and numerically early-time momentum diffusion rates for the delta-kicked rotor across the quantum to classical transition, i.e., as increased total system action produces more macroscopic dynamics. For sufficiently narrow initial momentum distributions we find a rich structure of resonances in these diffusion rates as a function of the effective Planck's constant. Our study is set in the physical context of the atom optics kicked rotor, and numerical simulations confirm that the resonances persist with kicks of finite duration and with other typical experimental imperfections, such as spontaneous emission noise. Our results should be testable in experiments where narrow initial momentum distributions are prepared using, for example, velocity selective Raman transitions or Bose-Einstein condensates.

Journal Article↗
PubMed2002

Diffusion resonances in action space for an atom optics kicked rotor with decoherence.

We numerically investigate momentum diffusion rates for the pulse kicked rotor across the quantum to classical transition as the dynamics are made more macroscopic by increasing the total system action. For initial and late time rates we observe an enhanced diffusion peak which shifts and scales with changing kick strength, and we also observe distinctive peaks around quantum resonances. Our investigations take place in the context of a system of ultracold atoms which is coupled to its environment via spontaneous emission decoherence, and the effects should be realizable in ongoing experiments.

Journal Article↗
PubMed2002

Emerging viral infections in Australia.

Emerging viruses include known viruses that have increased in incidence or geographic range (such as enteroviruses and Japanese encephalitis virus), new viruses associated with known diseases (Australian bat lyssavirus) and new viruses associated with previously unrecognized diseases (Hendra and Nipah viruses). Some may have a predilection for children (Japanese encephalitis, influenza viruses and enterovirus 71) and vigilance is essential to ensure early recognition of these agents.

Animal Diseases↗
PubMed2001

Comparison of male and female junior athletes' self-perceptions and body image.

Few studies have examined sex differences in body perceptions in sports where the pressure to display a certain physique is reduced. The aim of the present study was to investigate sex differences in physical self-perceptions and body image in junior athletes who are involved in sprint kayaking, a sport where a low body weight is relatively unimportant. 12 male and 13 female members (aged 13-17 yr.) of the British Canoe Union Junior Development Squad for sprint-kayak racing completed the Physical Self-perception Profile for Children and the Multidimensional Body-Self Relations Questionnaire. Multivariate analysis of variance indicated that girls reported significandy higher Sports Competence and lower Appearance Orientation scores than boys. This study has raised a number of issues surrounding the physical self-perceptions and body image of junior athletes involved in a power- and strength-based sport. It seems that male athletes may also experience pressures to conform to a male version of a 'beautiful body'.

Body Constitution↗
PubMed2000

Comparison of influenza A and influenza B virus infection in hospitalized children.

BACKGROUND: Influenza A and B viruses were cocirculating in Australia in the winter of 1997. OBJECTIVE: To compare the clinical and demographic features of children with influenza A or influenza B virus infection admitted to a paediatric tertiary referral centre. METHODOLOGY: Retrospective chart review of 91 hospitalized children with culture-proven influenza A or B virus infection during 1997. RESULTS: Thirty-six (56%) of 64 children with influenza A were under 12 months of age compared with seven (26%) of 27 children with influenza B virus infection (P = 0.02). Influenza B virus infection was more common in children with underlying medical problems (P = 0. 01). Neurological manifestations were present in eight (12.5%) of 64 children with influenza A and none with influenza B virus infection (P = 0.09). There were no significant differences in signs and symptoms of children with influenza A and B virus infection, in severity of illness or in duration of hospital stay. CONCLUSIONS: A greater proportion of children admitted with influenza A virus infection were under 12 months of age. Influenza B virus infection is associated more commonly with underlying medical disorders. It is not possible to differentiate between influenza A or B virus infection from presenting clinical signs and symptoms.

Australia↗