A model of visual-spatial memory across saccades

This paper describes a neural network model that directs saccades back to targets after they disappear and other saccades intervene. This is a simple example of knowing where something is after it is no longer visible and the observer has moved. These tasks require a short-term memory that can store continuous values of spatial location. The model was generated by training a neural network with a recurrently connected hidden layer to specify memory-guided saccades. The trained network maintains stored locations accurately for a few seconds. It uses a leaky integrator mechanism in which there is a slow decay of the stored value to a small number of fixed point attractors. Similar mechanisms have been used to model oculomotor integration (Cannon, S., Robinson, D., & Shamma, S. (1983). A proposed neural network for the integrator of the oculomotor system. Biological Cybernetics, 49, 127-136; Seung, H. (1998). Continuous attractors and oculomotor control. Neural Networks, 11, 1253-1258). The mechanism is robust to parameters such as the input and output format and the constraints in training. However, the receptive field properties of the hidden units do depend on these parameters. It was possible to find biologically plausible parameters that produced hidden unit behavior similar to that of real neurons involved in saccade memory. In particular, training the model to simultaneously represent the target location in both eye- and head-based reference frames produces units similar to neurons in parietal saccade areas.

Polarization measurements in high-energy deuteron photodisintegration

We present measurements of the recoil proton polarization for the d(gamma-->,p-->)n reaction at straight theta(c.m.) = 90 degrees for photon energies up to 2.4 GeV. These are the first data in this reaction for polarization transfer with circularly polarized photons. The induced polarization p(y) vanishes above 1 GeV, contrary to meson-baryon model expectations, in which resonances lead to large polarizations. However, the polarization transfer Cx does not vanish above 1 GeV, inconsistent with hadron helicity conservation. Thus, we show that the scaling behavior observed in the d(gamma,p)n cross sections is not a result of perturbative QCD. These data should provide important tests of new nonperturbative calculations in the intermediate energy regime.

Two- and three-dimensional TEE differentiation of lymphoma involving the atrial septum from lipomatous hypertrophy

In this case report we present two-dimensional (2-D) and three-dimensional (3-D) transesophageal echocardiographic (TEE) findings of a patient with lipomatous atrial septal hypertrophy and a patient with Hodgkin's lymphoma with atrial septal involvement. The echocardiographic characteristics that differentiate these two lesions are discussed.

Pathways mediating sexual abuse and eating disturbance in children

OBJECTIVE

To examine the relationship between childhood maltreatment and eating disorders in a sample of children.

METHOD

Twenty 10-15-year-old female children who were receiving treatment following reported childhood sexual abuse and 20 age-matched controls were compared on a series of measures assessing eating disorder behaviors, body image concerns, substance use, mood, impulsive behavior, and self-concept.

RESULTS

Sexually abused children reported higher levels of eating disorder behaviors, impulsive behaviors, and drug abuse than controls. Furthermore, behavioral impulsivity provided the strongest mediational effect between a history of childhood sexual abuse and purging and restrictive dieting behavior. Drug use proved to be a significant secondary mediator of the childhood sexual abuse eating disorder behavior association.

DISCUSSION

These data support the hypothesis that childhood sexual abuse is related to disordered eating in children, and extend similar findings that have been previously reported with adults. Behavioral impulsivity and drug use appear to be significant mechanisms that influence eating disorder behavior following childhood sexual abuse.

A randomized trial of nelfinavir, ritonavir, or delavirdine in combination with saquinavir-SGC and stavudine in treatment-experienced HIV-1-infected patients

PURPOSE

To evaluate the 24-week impact of saquinavir-enhancing antiretroviral therapy on viral replication in patients previously treated with nucleoside analogues with or without prior saquinavir hard-gel capsules (HGC).

METHOD

Patients were randomized in three groups to receive the following: Group 1-nelfinavir (750 mg tid), saquinavir soft-gel capsule (SGC) (800 mg tid), and stavudine (40 mg bid); Group II-ritonavir (400 mg bid), saquinavir-SGC (400 mg bid), and stavudine (40 mg bid); or Group III-delavirdine (400 mg tid), saquinavir-SGC (800 mg tid), and stavudine (40 mg bid). Viral loads, CD4 count, and safety were assessed over a 24-week period with an additional 6-month follow-up.

RESULTS

73 patients received randomized therapy; 14 of whom were SQV naïve, with a median baseline viral load of 3.6 log(10) and a CD4 count of 370 cells/mm(3). By 6 months, the median decreases in plasma viral loads were 0.26, 0.71, and 0.29 log(10) copies/mL for groups I, II, and III, respectively. The median increases in CD4 counts, for groups I, II, and III, were 52, 40, and 69 cells/mm(3) at 6 months, respectively. Changes in viral load and CD4 counts at 6 months and 1 year were not significantly different between the treatment groups. More patients discontinued therapy in the ritonavir arm (35%) for drug intolerance or toxicity compared to either the nelfinavir or delavirdine arms (15% and 5%, respectively). In a multivariate analysis, baseline viral load, younger age, and baseline saquinavir resistance were significantly associated with detectable viral load at 24 weeks.

CONCLUSION

The use of antiretroviral agents that pharmacokinetically boost saquinavir levels has a modest benefit in saquinavir-experienced patients.

Measurement of the charged pion electromagnetic form factor

Separated longitudinal and transverse structure functions for the reaction 1H(e,e(')pi(+))n were measured in the momentum transfer region Q2 = 0.6--1.6 (GeV/c)(2) at a value of the invariant mass W = 1.95 GeV. New values for the pion charge form factor were extracted from the longitudinal cross section by using a recently developed Regge model. The results indicate that the pion form factor in this region is larger than previously assumed and is consistent with a monopole parametrization fitted to very low Q2 elastic data.

Elliptic flow in Au+Au collisions at square root(S)NN = 130 GeV

Elliptic flow from nuclear collisions is a hadronic observable sensitive to the early stages of system evolution. We report first results on elliptic flow of charged particles at midrapidity in Au+Au collisions at square root(S)NN = 130 GeV using the STAR Time Projection Chamber at the Relativistic Heavy Ion Collider. The elliptic flow signal, v2, averaged over transverse momentum, reaches values of about 6% for relatively peripheral collisions and decreases for the more central collisions. This can be interpreted as the observation of a higher degree of thermalization than at lower collision energies. Pseudorapidity and transverse momentum dependence of elliptic flow are also presented.

The association of race/ethnicity, socioeconomic status, and physician recommendation for mammography: who gets the message about breast cancer screening?

OBJECTIVES

This study investigated the association between physician recommendation for mammography and race/ethnicity, socioeconomic status, and other characteristics in a rural population.

METHODS

In 1993 through 1994, we surveyed 1933 Black women and White women 52 years and older in 10 rural counties.

RESULTS

Fifty-three percent of the women reported a physician recommendation in the past year. White women reported recommendations significantly more often than did Black women (55% vs 45%; odds ratio = 1.49). Controlling for educational attainment and income eliminated the apparent racial/ethnic difference. After control for 5 personal, 4 health, and 3 access characteristics, recommendation for mammography was found to be more frequent among women who had access to the health care system (i.e., had a regular physician and health insurance). Recommendation was less frequent among women who were vulnerable (i.e., were older, had lower educational attainment, had lower annual family income).

CONCLUSIONS

Socioeconomic status, age, and other characteristics--but not race/ethnicity--were related to reports of a physician recommendation, a precursor strongly associated with mammography use. Efforts to increase physician recommendation should include complementary efforts to help women address socioeconomic and other barriers to mammography use.

Clearance of barium from the oesophagus with diet cola and metoclopramide: a one stop approach to patients with dysphagia

AIM

To establish a "one-stop" dysphagia service in which a consultation, barium swallow and endoscopy can all be performed in the same hospital visit.

MATERIALS AND METHODS

In order to allow both barium swallow examination and endoscopy to be performed on the same day, a novel technique for clearing barium from the upper gastrointestinal tract was established. Following the barium swallow examination, patients were given diet cola and metoclopramide syrup. If appropriate, an upper gastrointestinal endoscopy was then performed shortly afterwards. The service was piloted for 6 months in which time 25 patients were investigated in this way.

RESULTS

All patients were seen within 2 weeks of referral. The mean time between barium swallow and endoscopy was 3 h 38 min (range, 1 h 50 min to 5 h 20 min). In all 24 patients in whom an endoscopy was performed, barium had been satisfactorily cleared from the oesophagus and stomach.

CONCLUSION

This technique allows both barium swallow and upper gastrointestinal endoscopy to be performed on the same day, providing a rapid, safe and accurate diagnosis with minimum patient inconvenience. Mitchell, J., (2001). Clinical Radiology56, 64-66

Architectural support for copy and tamper resistant software

Although there have been attempts to develop code transformations that yield tamper-resistant software, no reliable software-only methods are know. This paper studies the hardware implementation of a form of execute-only memory (XOM) that allows instructions stored in memory to be executed but not otherwise manipulated. To support XOM code we use a machine that supports internal compartments---a process in one compartment cannot read data from another compartment. All data that leaves the machine is encrypted, since we assume external memory is not secure. The design of this machine poses some interesting trade-offs between security, efficiency, and flexibility. We explore some of the potential security issues as one pushes the machine to become more efficient and flexible. Although security carries a performance penalty, our analysis indicates that it is possible to create a normal multi-tasking machine where nearly all applications can be run in XOM mode. While a virtual XOM machine is possible, the underlying hardware needs to support a unique private key, private memory, and traps on cache misses. For efficient operation, hardware assist to provide fast symmetric ciphers is also required.

Architectural support for copy and tamper resistant software

Although there have been attempts to develop code transformations that yield tamper-resistant software, no reliable software-only methods are known. This paper studies the hardware implementation of a form of execute-only memory (XOM) that allows instructions stored in memory to be executed but not otherwise manipulated. To support XOM code we use a machine that supports internal compartments---a process in one compartment cannot read data from another compartment. All data that leaves the machine is encrypted, since we assume external memory is not secure. The design of this machine poses some interesting trade-offs between security, efficiency, and flexibility. We explore some of the potential security issues as one pushes the machine to become more efficient and flexible. Although security carries a performance penalty, our analysis indicates that it is possible to create a normal multi-tasking machine where nearly all applications can be run in XOM mode. While a virtual XOM machine is possible, the underlying hardware needs to support a unique private key, private memory, and traps on cache misses. For efficient operation, hardware assist to provide fast symmetric ciphers is also required.

Teleradiology at the tertiary-level Women's and Children's Hospital in South Australia

This article relates to a teleradiology trial undertaken in 1998-1999 at the Women's and Children's Hospital (WCH) in Adelaide, the capital of South Australia. The trial involved linking the hospital to a range of rural and remote sites in South Australia and the Northern Territory. The main aim of the project was to evaluate the advantages, limitations, benefits, and costs of a teleradiology service provided by WCH. The major finding from the study is that for a tertiary hospital providing second opinions in complex medical cases, a new form of business justification is required for teleradiology. The justification would include an emphasis on the range of high-level services that a subspecialist hospital such as the WCH can provide. The justification would also include the range of benefits to different parties, particularly the patient, and the intangible nature of many of the benefits.

An evaluation of satisfaction with telemedicine among health-care professionals

A survey was conducted among non-doctor health-care professionals in six rural counties in Missouri. The purpose of the survey was to establish baseline data to evaluate the effect of changes in the health-care sector, especially technology changes, on the job satisfaction, career satisfaction, relationships and communication activities of health professionals. The survey included three rural counties in which integrated telecommunication and interactive video telemedicine services were being installed, but before significant activities had begun, and three comparator counties without substantial integrated telecommunications infrastructure and telemedicine services. During a one-month study period, 1108 questionnaires were distributed. The total response rate was 50.1% (n = 555). Of the respondents, 30.3% indicated that technology in health-care was having a large effect on their work, although only 18.2% indicated that telemedicine and telecommunications were having a large effect. No systematic differences were found among the health professionals in the two communities at the time telemedicine equipment was being installed.

The incidence and dimensions of the retroarticular canal of the atlas vertebra

The retroarticular canal has been implicated in compression of the vertebral artery, where it passes over the posterior arch of the atlas vertebra, during extreme rotational movements of the head and neck. The incidence of this retroarticular canal is not known in the South African population. The aim of the present study was to record the incidence and the dimensions of the retroarticular canal in South African white and black adults, aged 20-80 years. In a total of 1,354 atlas vertebrae, 9.8% of sides (264 left and/or right sides) were classified as having complete retroarticular canals, of which 11.7% (31 sides) were right-only, 24.6% (65 sides) left-only and 31.8% (84 left plus right sides) bilateral canals. This incidence did not increase with age and was lower in whites than blacks, with white males having the lowest and white and black females alike having the highest incidence of the canal. Measurements of the retroarticular canal showed that there was no difference between left and right sides. However, the superoinferior diameter was significantly less than the anteroposterior diameter, in all but the right canals in the white female subgroup. This difference in the dimensions of the retroarticular canal will decrease the cross-sectional area of the space available for the vertebral artery passing through it and may compromise blood flow in the vessel.

An evaluation of a network for professional development in child and adolescent mental health in rural and remote communities

In 1998 a telemedicine network was established in South Australia and the Northern Territory to deliver educational material to professionals working in child and adolescent mental health in remote areas. The network involved a wide range of health professions, from psychiatrists to psychologists and social workers. The first 12 months of network activity were evaluated by quantitative and qualitative techniques. Four sources of data were used: an activity log, questionnaires, interviews and action research. A total of 36 telemedicine sessions were held, ranging in duration from 45 to 90 min (average 56 min) and involving a total of 45 different professionals, who participated an average of four times each (range 1-15). The most common types of session were case discussions (47%), followed by specialist seminars (36%) and administrative and introductory sessions (17%). The benefits of the network included: networking and peer support; improved efficiency and reduced travel costs; and improved efficiency of health services. The problems included: costs; lack of access to technical support; and the need for staff induction and training.

Dissociation of G-protein alpha from rhabdomeric membranes decreases its interaction with rhodopsin and increases its degradation by calpain

Photoactivation of invertebrate rhodopsin activates a GTP-binding protein, Gq, which in turn activates a phospholipase C (PLC) enzyme. Gqalpha is a membrane-associated protein that is progressively released from the membrane by washing with buffers containing increasing concentrations of beta-mercaptoethanol (beta-ME). Isolated, soluble Gqalpha showed a decreased ability to be activated by rhodopsin but was more active in stimulating PLC when compared with the membrane-associated form of Gqalpha. The calcium-activated protease, calpain, selectively cleaved the soluble but not the membrane-bound form of Gqalpha. Calpain cleaved a small peptide from the amino-terminus of Gqalpha reducing the ability of the G-protein to bind GTP. The uncoupling of Gqalpha from rhodopsin and subsequent calcium-dependent proteolysis to further inactivate the G-protein may therefore be a regulatory mechanism of light adaptation in rhabdomeric photoreceptors.

Physiotherapy for anterior knee pain: a randomised controlled trial

OBJECTIVE

To determine the efficacy of the individual components of physiotherapy in subjects with anterior knee pain.

METHODS

An observer blind, prospective, factorial design randomised controlled trial. 81 young adults with anterior knee pain were randomly allocated to one of four treatment groups: (1) exercise, taping, and education; (2) exercise and education; (3) taping and education; and (4) education alone. Each group received six physiotherapist-led treatments over three months. Follow up took place at three months using the following outcome measures: patient satisfaction (discharge/refer for further treatment); a visual analogue pain score; the WOMAC lower limb function score; the Hospital Anxiety and Depression scale (HAD); and quadriceps strength. At 12 months the WOMAC and HAD were assessed by postal questionnaire.

RESULTS

All groups showed significant improvements in WOMAC, visual analogue, and HAD scores; these improvements did not vary significantly between the four groups or between exercising/non-exercising and taped/non-taped patients at three and 12 months. However, patients who exercised were significantly more likely to be discharged at three months than non-exercising patients (chi(2), p<0.001). Taping was not significantly associated with discharge. Significantly greater improvements in WOMAC, visual analogue, and the anxiety score (but not the depression score) were seen in patients who were discharged than in those who were referred.

CONCLUSIONS

The proprioceptive muscle stretching and strengthening aspects of physiotherapy have a beneficial effect at three months sufficient to permit discharge from physiotherapy. These benefits are maintained at one year. Taping does not influence the outcome.

Identification of small FRAXA premutations

BACKGROUND

Diagnosis of fragile X syndrome in mentally retarded individuals is satisfactorily achieved using a Southern blot test that detects the typical triplet repeat expansion (>200 repeats) within the FMR1 gene. All such individuals inherit the mutation from a carrier, who usually shows a lower triplet repeat number and may be asymptomatic. Having identified a fragile X proband, it is necessary to identify related carriers of this familial X-linked dominant mutation to provide family counseling and testing.

METHODS AND RESULTS

For one family in which a fragile XA repeat expansion occurs, Southern blot hybridization did not give accurate sizing data because of the very small premutation associated with the unstable allele. PCR sizing methods and linkage analysis were adapted to identify family members with the premutation.

CONCLUSION

Although most carriers can be detected using Southern blot and/or direct PCR sizing tests, very small expansions (55-70 repeats) are difficult to distinguish from larger, normal alleles. We have used linkage analysis in combination with direct allele analysis to identify carriers of very small expansions of a fragile X chromosome in a four-generation family.

Quantifying the association between habitual energy expenditure and blood pressure

BACKGROUND

Previous studies have demonstrated an association between physical inactivity and hypertension, but the methods used to assess activity have been subjective and imprecise. Recently methods have become available allowing measurement of energy expenditure in free-living populations. Our aim was to employ these methods to assess the independent association between energy expenditure, cardio-respiratory fitness and blood pressure.

METHODS

In a cross-sectional study of 775 people (45-70 years) participating in a continuing population-based cohort study, energy expenditure was assessed by 4 days of heart rate monitoring with individual calibration of the relationship between heart rate and energy expenditure, a method validated against doubly-labelled water and whole body calorimetry. Cardio-respiratory fitness was assessed in a sub-maximal test. To adjust for measurement error in the assessment of usual energy expenditure and fitness, 190 subjects repeated both tests on three further occasions at 4-monthly intervals.

RESULTS

A highly significant linear trend in blood pressure was found across quintiles of the physical activity level, the ratio of total energy expenditure to basal metabolic rate. The differences in the mean systolic/diastolic blood pressure between the top and bottom quintile was 6.3/4.4 mmHg in men and 10.7/5.9 mmHg in women. These effects were independent of obesity and cardio-respiratory fitness. Correction for measurement error suggests that the true underlying relationship between usual energy expenditure and blood pressure is stronger still.

CONCLUSIONS

These findings are compatible with a strong association between usual energy expenditure and blood pressure and support public health strategies aimed at increasing overall energy expenditure.

Identification of genetic heterogeneity in Refsum's disease

Refsum's disease (MIM 266500) is a recessive disorder characterised by defective peroxisomal alpha-oxidation of phytanic acid. A Refsum's disease gene, phytanoyl-CoA hydroxylase (PAHX), has been localised to chromosome 10p13 between the markers D10S226-D10S223. This study investigated whether all cases of Refsum's disease were linked with chromosome 10p13. Eight genetically informative families comprising 92 individuals including 17 living patients with a Refsum's disease phenotype and initial plasma phytanic acid > 200 micromol/L were recruited. Linkage to the 10pter-10p11.2 region was investigated using a panel of eight dinucleotide repeat markers. Linkage analysis of this phenotypically identical cohort suggested that Refsum's disease was genetically heterogeneous (Zmax = 5.28, alpha = 0.45). Two subgroups were identified. One group of four families with eight affected individuals had a maximum multipoint lod score for linkage of 3.89 in the region D10S547 to D10S191, whilst in another three families with nine affected individuals linkage to this region was definitely excluded. Our results show that Refsum's disease is genetically heterogeneous, with up to 55% of cases not being linked to the PAHX gene locus at D10S547 to D10S223. This suggests that Refsum's disease, in common with other peroxisomal 'diseases', may be more accurately described as a heterogeneous syndrome.

Calcium hydroxylapatite deposition disease in a Great Dane Puppy

A 10-week-old male Great Dane Puppy was presented for sudden onset tetraataxia and severe paresis of the front legs. Mineral deposits were detected radiographically, at gross postmortem examination, and light microscopically between the vertebral arches of multiple cervical and lumbar vertebrae. These deposits were associated with the interarchial ligaments (ligamentia interarcualia), along the interfaces of the synovium and articular cartilage of multiple cervical, thoracic, and lumbar facets, on the dorsal aspect of several thoracic intervertebral discs, and at the insertion of muscles at the lateral aspect of several cervical and thoracic vertebral bodies. The mineral deposits were associated with a granulomatous inflammation and synovial fibrocartilaginous metaplasia and proliferation, which was focally exuberant. X-ray diffraction analyses of the mineral deposits revealed calcium hydroxylapatite as the major component. The clinical signs in this puppy were due to focal compression of the spinal cord by marked extraarticular ligament-associated fibrocartilaginous proliferation.

Increasing the cost-effectiveness of telemedicine by embracing e-health

In 1999 a national study of telemedicine in Australia led to the promotion of the concept of 'e-health', the health sector's equivalent of 'e-commerce'. A new study explored the view that, with the convergence of technologies and the consequent increase in ability to perform multiple functions with those technologies, it is unwise to promote telemedicine in isolation from other uses of technologies in health-care. The major sources of information for the study were the presentations and discussions at five national workshops held to discuss the findings of the original report on telemedicine. Nineteen case studies were identified. The case studies showed that with the convergence of technologies telehealth is becoming part of e-health. The cost-effectiveness of both telehealth and telemedicine improves considerably when they are part of an integrated use of telecommunications and information technology in the health sector.