Recording advances for neural prosthetics

An important challenge for neural prosthetics research is to record from populations of neurons over long periods of time, ideally for the lifetime of the patient. Two new advances toward this goal are described, the use of local field potentials (LFPs) and autonomously positioned recording electrodes. LFPs are the composite extracellular potential field from several hundreds of neurons around the electrode tip. LFP recordings can be maintained for longer periods of time than single cell recordings. We find that similar information can be decoded from LFP and spike recordings, with better performance for state decodes with LFPs and, depending on the area, equivalent or slightly less than equivalent performance for signaling the direction of planned movements. Movable electrodes in microdrives can be adjusted in the tissue to optimize recordings, but their movements must be automated to be a practical benefit to patients. We have developed automation algorithms and a meso-scale autonomous electrode testbed, and demonstrated that this system can autonomously isolate and maintain the recorded signal quality of single cells in the cortex of awake, behaving monkeys. These two advances show promise for developing very long term recording for neural prosthetic applications

Magnetoresistance of a two-dimensional electron gas in a parallel magnetic field

The conductivity of a two-dimensional electron gas in a parallel magnetic field is calculated. We take into account the magnetic field induced spin-splitting, which changes the density of states, the Fermi momentum and the screening behavior of the electron gas. For impurity scattering we predict a positive magnetoresistance for low electron density and a negative magnetoresistance for high electron density. The theory is in qualitative agreement with recent experimental results found for Si inversion layers and Si quantum wells.Comment: 4 pages, figures included, PDF onl

Causes of road traffic accidents in Juba

Introduction: Road traffic accidents (RTAs) are a major cause of death and disability in South Sudan. The purpose of this study was to investigate whether violation of traffic rules is the main cause of RTAs.Method: A cross sectional study design was used with quantitative data covering January – December 2014. The main objective of the research was to understand the epidemiology of RTAs in order to develop preventive measures. A total of 1,725 cases from road RTAs data were extracted from the directorate of traffic police Central Equatoria state Juba and Juba teaching hospital.Results: Most (99.5%) of the RTA drivers were not under the influence of alcohol. Most accidents were caused by male drivers (99%). The highest number of RTAs took place in August (11%). Drivers of private vehicles caused most accidents (37%). Most drivers (46%) were aged 20-30 years. RTAs occurred most often on city roads (89.83%). Conclusion: This leads us to conclude that a comprehensive safety system is needed that are premised on the idea of community-based awareness of traffic rules and safety regulations. Resources are limited so there is a need to harness local resources including the local community. More efforts are needed to improve road safety education among the youth/ integrate safety into road design.Key Words: Road traffic accidents, private vehicles, alcoho

Possible Metal/Insulator Transition at B=0 in Two Dimensions

We have studied the zero magnetic field resistivity of unique high- mobility two-dimensional electron system in silicon. At very low electron density (but higher than some sample-dependent critical value, $n_{cr}\sim 10^{11}$ cm$^{-2}$), CONVENTIONAL WEAK LOCALIZATION IS OVERPOWERED BY A SHARP DROP OF RESISTIVITY BY AN ORDER OF MAGNITUDE with decreasing temperature below 1--2 K. No further evidence for electron localization is seen down to at least 20 mK. For $n_s<N_{cr}$, the sample is insulating. The resistivity is empirically found to SCALE WITH TEMPERATURE BOTH BELOW AND ABOVE $n_{cr}$ WITH A SINGLE PARAMETER which approaches zero at $n_s=n_{cr}$ suggesting a metal/ insulator phase transition.Comment: 10 pages; REVTeX v3.0; 3 POSTSCRIPT figures available upon request; to be published in PRB, Rapid Commu

Abstracts from the 50th European Society of Human Genetics Conference: Posters

International audienc

Effects of consistency vs. variability in robotically controlled training of stepping in adult spinal mice

This paper studies the possible benefit that can be obtained by introducing variability into the robotic control of trajectories used to train hindlimb locomotion in adult spinal mice. The spinal cords of adult female Swiss-Webster mice were completely transected at a mid-thoracic level. Fourteen days post-transection, the spinal mice were robotically trained to step in the presence of a 5-HT agonist, quipazine, for a period of six weeks. In this pilot study nine animals were divided into three groups, each receiving a different control strategy: a fixed training trajectory (Group A), a variable training trajectory without interlimb coordination imposed (Group B) and a variable training trajectory with hindlimb bilateral coordination imposed (Group C). Preliminary results indicate that Group A recovers more slowly than the two groups receiving variable modes of robotic training. Groups B and C show higher levels of recovery than Group A in terms of the number of steps performed during testing sessions, as well as in their step periodicity and shape consistency. Group C displays a higher incidence of alternating stepping than Group B. These results indicate that variable trajectory robotic training paradigms may be more effective than fixed trajectory paradigms in promoting robust post-injury stepping behavior. Furthermore, it appears that the inclusion of interlimb coordination is an important contribution to successful training

Solvent-free fluidic organic dye lasers

We report on the demonstration of liquid organic dye lasers based on 9-(2-ethylhexyl)carbazole (EHCz), so-called liquid carbazole, doped with green-and red-emitting laser dyes. Both waveguide and Fabry-Perot type microcavity fluidic organic dye lasers were prepared by capillary action under solvent-free conditions. Cascade Forster-type energy transfer processes from liquid carbazole to laser dyes were employed to achieve color-variable amplified spontaneous emission and lasing. Overall, this study provides the first step towards the development of solvent-free fluidic organic semiconducting lasers and demonstrates a new kind of optoelectronic applications for liquid organic semiconductors

Utility of Dutch Lipid Clinic Network Score to Estimate Prevalence of Familial Hypercholestrolemia in Patients with ST-Elevation Myocardial Infarction

Background Hypercholesterolaemia is prevalent in the Malaysian population, and its treatment control rates remain suboptimal1. Familial hypercholesterolemia (FH) is an autosomal dominant condition that leads to accelerated arteriosclerotic cardiovascular disease (ASCVD). The prevalence of FH in the general population worldwide has been postulated to be 1:3132 and 1:100 in the Malaysian community3. It has been proposed that lipid lowering treatment prevents further increase in total cardiovascular risk of FH patients, and this recommendation is extensible for FH patients plus atherosclerotic CAD (coronary artery disease). However, despite its implication in CAD, FH is still an underdiagnosed and undertreated condition2-4. To date, the prevalence of FH in the STEMI (ST-elevation myocardial infarction) population in Malaysia is not studied. Establishing the prevalence of FH among patients with CAD and comparing this with the general population would help future efforts at identifying subjects with FH. Objective We aim to estimate the prevalence of FH in patients with STEMI in Sarawak using Dutch Lipid Clinic Network (DLCN) score. Materials and Methods Patients who were admitted for type-1 STEMI from April 2021 until July 2021 to Pusat Jantung Sarawak were recruited. History taking and physical examination were carried out on-site. FH was screened clinically using DLCN score. Results Out of the recruited patients, 45% of the cohort was clinically categorized into probable/ possible FH without genetic testing. Mean age and low density lipoprotein (LDL) were 52.7 and 3.38mmol/l respectively. Prevalence of premature CAD was 63%. Male gender, smoking, high BMI was the most frequent risk factor observed. Conclusions Prevalence of probable/possible familial hypercholesterolemia in a STEMI cohort using DLCN score is 45%. DLCN score in the STEMI cohort is not related to LDL levels

Coronary artery calcification – distribution, extent and 1-year outcomes in patients with low to intermediate pre-test probability of coronary artery disease.

Background: Coronary artery calcium (CAC) is an established marker to predict major cardiovascular events (MACE), and has incremental value over traditional risk factors (CVRF). CAC is widely available, easily reproducible, and used in nearly all coronary computed tomography angiography (CCTA) assessment protocols for coronary artery disease (CAD). The distribution and extent of CAC, and its prognostic implications in local Malaysian patients with low to intermediate pre-test probability (LI-PTP) of CAD had not been established. Objectives: We aimed to establish the distribution, extent and prognostic implications of CAC in patients without known CAD, but with LI-PTP of CAD, undergoing CCTA for chest pain evaluation. Methods: Clinical information was obtained from consecutive patients who underwent CAC and CCTA examination from January 2020 to January 2021 at a single public access tertiary referral centre. The primary outcomes were the distribution and extent of CAC, and its relationship with MACE at 1 year. Results: Of 499 consecutive patients, 7 were excluded due to high PTP. CAC was present in 172/492 (35%). Within this group, 74/172 (41.3%) had CAC score of 1-100 (mild), 75/172 (42.4%) had a CAC of 101- 400 (moderate), 23/172 (13.4%) had CAC of >400 (high). 136 had suspected significant CAD and was offered conventional coronary angiography (CCA). 91/492 underwent CCA, and 38 were found to have significant CAD. Of those found to have significant CAD, 7/38 (18.4%) had CAC of zero, 8/38 (21.1%) had mild CAC, 12/38 (31.6%) moderate, and 11/38 (30%) high CAC. Severe CAC was associated with a higher rate of revascularization 11/23 (47.8%), compared to those with zero 7/320 (2.2%), mild 8/74 (10.8%) and moderate 12/75 (16%) CAC. Predictors of high CAC were age, male gender, and presence of cardiovascular disease risk factors. Of the 492 patients, 230 patients completed 1 year follow-up, and from this, 1 patient had a MACE. Conclusion In patients with LI-PTP risk of CAD, CAC was seen in approximately one third of our cohort. In the group with high CAC, a higher proportion required coronary revascularization, but MACE remained low at 1 year

Coronary Computed Tomography Angiography as part of initial strategy, in assessment of patients with chest pain – clinical experience and 1 year prognosis.

Background: Coronary computed tomography angiography (CCTA) has been showed to have high specificity and sensitivity for detecting coronary artery disease (CAD). In Malaysia, national guidelines state that CCTA may be used in low- to intermediate pre-test probability (LI-PTP) of CAD, who have an equivocal functional test result, and who are asymptomatic or mildly symptomatic with good exercise capacity. Recent evidence suggested a ‘CCTA-first’ strategy in the evaluation of a patient with chest pain could provide prognostic benefits. Prognostic benefits of adopting this strategy in Malaysia has not been well studied. Objectives: We aimed to evaluate 12-month clinical outcomes of patients with LI-PTP, using the CCTA as an initial strategy, or as part of the work-up for, chest pain assessment. Methods: Consecutive patients who underwent CCTA examination from January 2020 to January 2021 were enrolled. Clinical information was then extracted. Primary outcome was defined as presence of stenosis of >50% in a major epicardial coronary artery; and secondary outcome defined as a composite of all-cause mortality, non-fatal myocardial infarction (MI) and coronary revascularisation. Results: Among the initial 499 patients, 7 were excluded as they were high in PTP. The mean PTP was 47.1±26.3. Baseline characteristics were available in 300 patients. The mean age was 53.5±11.4 years, 59.3% were male, 18.6% were diabetic, 71.2% had hypertension, and 50.8% had hypercholestrolaemia. 1.9% had an equivocal functional test for ischaemia. Of the 492 LI-PTP patients who underwent CCTA, 136 patients were suspected to have significant CAD, and recommended conventional coronary angiography (CCA). Of these, 91 patients underwent CCA. From this group 38 were found to have significant CAD which warranted revascularisation – 32 by percutaneous coronary intervention (PCI) and 6 referred for coronary artery bypass surgery (CABG). Therefore, utilising this strategy, 7.7% (38/492) of patients met the primary outcome. Of the original cohort of 492 LI-PTP patients, only 230 completed 1 year follow up, and from this, one patient met the secondary outcome. Conclusion Incorporation of CCTA into contemporary chest pain evaluation identified significant number of patients with significant CAD and was also associated with a low cardiac event rate at 1 year follow-up