Seasonality of the Meridional Overturning Circulation in the subpolar North Atlantic.

Understanding the variability of the Atlantic Meridional Overturning Circulation is essential for better predictions of our changing climate. Here we present an updated time series (August 2014 to June 2020) from the Overturning in the Subpolar North Atlantic Program. The 6-year time series allows us to observe the seasonality of the subpolar overturning and meridional heat and freshwater transports. The overturning peaks in late spring and reaches a minimum in early winter, with a peak-to-trough range of 9.0 Sv. The overturning seasonal timing can be explained by winter transformation and the export of dense water, modulated by a seasonally varying Ekman transport. Furthermore, over 55% of the total meridional freshwater transport variability can be explained by its seasonality, largely owing to overturning dynamics. Our results provide the first observational analysis of seasonality in the subpolar North Atlantic overturning and highlight its important contribution to the total overturning variability observed to date.

A real-time data acquisition and control of gradient coil noise for fMRI identification of hearing disorder in children with history of ear infection.

Early ear infection and trauma, from birth to age 12 are known to have a significant effect on sensory and cognitive development. This effect can be demonstrated through the fMRI study of children who have a history of ear infection compared to a control group. A second research question is the extent to which brain plasticity at an early age can reduce the impact of infection on hearing and cognitive development. Functional Magnetic Resonance Imaging (fMRI) provides a mapping of brain activity in cognitive and sensory regions by recording the oxygenation state of the local cerebral blood flow. The gradient coils of fMRI scanners generate intense acoustic noise (GCN) - to which the subject is in close proximity - in the range of 90 to 140 db SPL during the imaging process. Clearly this noise will impress its signature on low level brain response patterns. An Active Noise Canceller (ANC) system can suppress the effect of GCN on the subject's perception of a phonetic stimulus at the phoneme, word or phrase level. Due to a superimposition of the frequency and time domain components of the test signal and GCN for MR test, the ANC filtering system performs its function in real time - we must capture the brain's response to the test signal AFTER the noise has been removed. This goal is achieved through the application of field programmable gate array (FPGA) technology of NI LabVIEW. The presentation (in the noisy fMRI environment) of test words and phrases to hearing impaired children can identify sources of distortion to their perceptual processes associated with GCN. Once this distortion has been identified, learning strategies may be introduced to replace the hearing function distorted by early infection as well as the short term effect of GCN. The study of speech cognition without the confounding effect of GCN and with the varying level of GCN for a repeated test signal at later age can be allowed to a measure of recovery through brain plasticity.

Initial stability measurement of dental implants placed in different anatomical regions of fresh human cadaver jawbone.

STATEMENT OF PROBLEM: Initial implant stability has been used as an indicator for future osseointegration and whether an immediate/early loading protocol should be applied. However, differences in initial stability in relation to anatomical regions of jawbone have not been studied extensively because of the risks involved with stability measurements. PURPOSE: The purpose of this study was to determine whether initial implant stability varies with anatomical regions of the jawbone. MATERIAL AND METHODS: Four pairs of edentulous maxillae and mandibles were retrieved from fresh human cadavers. Six implants (Biomet 3i) per pair were placed in different anatomical regions (maxillary anterior, right and left maxillary posterior, mandibular anterior, right and left mandibular posterior). Immediately after implant placement, initial implant stability was measured with a custom-made resonance frequency analyzer, a commercial resonance frequency analysis device (Osstell), and a mechanical tapping device (Periotest). All implant surgeries and initial stability measurements were performed within 72 hours of death to simulate a clinical setting. Repeated measures ANOVA (alpha=.05) and univariate correlation analyses were used to analyze the data. RESULTS: Mandibular implants had significantly higher initial stability than maxillary implants. Posterior maxillary implants were least stable. Stability was less buccolingually than mesiodistally. The measurements from 3 stability measuring devices were strongly associated with each other. CONCLUSIONS: Initial implant stability varied among anatomical regions of jawbone. Rank of Periotest value and implant stability quotient (Osstell) had the highest correlation (r=-0.852).

Investigation of non-uniform airflow signal oscillation during high frequency chest compression.

BACKGROUND: High frequency chest compression (HFCC) is a useful and popular therapy for clearing bronchial airways of excessive or thicker mucus. Our observation of respiratory airflow of a subject during use of HFCC showed the airflow oscillation by HFCC was strongly influenced by the nonlinearity of the respiratory system. We used a computational model-based approach to analyse the respiratory airflow during use of HFCC. METHODS: The computational model, which is based on previous physiological studies and represented by an electrical circuit analogue, was used for simulation of in vivo protocol that shows the nonlinearity of the respiratory system. Besides, airflow was measured during use of HFCC. We compared the simulation results to either the measured data or the previous research, to understand and explain the observations. RESULTS AND DISCUSSION: We could observe two important phenomena during respiration pertaining to the airflow signal oscillation generated by HFCC. The amplitudes of HFCC airflow signals varied depending on spontaneous airflow signals. We used the simulation results to investigate how the nonlinearity of airway resistance, lung capacitance, and inertance of air characterized the respiratory airflow. The simulation results indicated that lung capacitance or the inertance of air is also not a factor in the non-uniformity of HFCC airflow signals. Although not perfect, our circuit analogue model allows us to effectively simulate the nonlinear characteristics of the respiratory system. CONCLUSION: We found that the amplitudes of HFCC airflow signals behave as a function of spontaneous airflow signals. This is due to the nonlinearity of the respiratory system, particularly variations in airway resistance.

Modeled velocity of airflow in the airways during various respiratory patterns.

Our modeling and simulation of the respiratory system with Weibel's morphometry shows that the average velocity of expiratory airflow is always greater than the average velocity of inspiratory airflow during tidal breathing when the intervals of inspiration and expiration are same. A nonlinear circuit model was developed comprised with the upper airway, the conducting airways (trachea approximately terminal bronchioles), and the lumped alveolar space. These compartments are established with known physiologic pulmonary characteristics that are represented by nonlinear resistors and capacitors. In this paper we set up the circuit model reflecting the geometric variation of airways during tidal breathing, and demonstrated computation results for the velocity of airflow along the airways based on 16 different respiratory patterns. The circuit model offers a convenient method that can be used to investigate the velocity of airflow and its interaction with mucus, as well as suggests a basic model for our future research on analyzing airway clearance techniques.

No baseline for blood pressure in ordinary life: another case of transient chronome alterations.

Half-hourly systolic (S) and diastolic (D) blood pressure (BP) and heart rate (HR) monitoring with gaps demonstrates transient elevations of unknown origin of the chronome (time structure)-adjusted mean, the MESOR, M, of BP, and of the circadian double amplitude of BP of TS, a clinically healthy-appearing engineering student who was 27 years of age at the start of the study. An assessment of large and small arterial vessel elasticity was in keeping with no detection of functional or structural alteration in her vasculature. The recovery of normality in BP endpoints at the time of this report is speculatively associated with a weight loss of 40 pounds and the formation of a friendship by correspondence. Whatever the underlying mechanisms of a long series of abnormal records may be, a 'baseline' can include weeklong spans of abnormality and is best replaced by comparisons with chronomic reference values.