Potential advantage of flash echocardiography for digital subtraction of B-mode images acquired during myocardial contrast echocardiography

Optimal assessment of myocardial perfusion with contrast echocardiography by using B-mode imaging often requires image alignment and background subtraction, which are time consuming and need extensive expertise. Flash echocardiography is a new technique in which primary images are gated to the electrocardiogram and secondary images are obtained by transmitting ultrasound pulses in rapid succession after each primary image. Myocardial opacification is seen in the primary image and not in the secondary images because of ultrasound-induced bubble destruction. Because the interval between the primary and first few secondary images is very short, cardiac motion between these images should be minimal. Therefore we hypothesized that 1 or more secondary images could be subtracted from the primary image without the need for image alignment. The ability of ultrasound to destroy microbubbles was assessed by varying the sampling rate, line density, and mechanical index in 6 open-chest dogs. The degree of translation between images was quantified in the x and y directions with the use of computer cross-correlation. At sampling rates of 158 Hz or less and a mechanical index of more than 0.6, videointensity rapidly declined to baseline levels by 25 ms. Significant translation between images was noted only at intervals of more than 112 ms. It is concluded that flash echocardiography can be used for digital subtraction of baseline from contrast-enhanced B-mode images without image alignment. Background subtraction is therefore feasible on-line, potentially eliminating the need for off-line image processing in the future.     

Magnetotransmission and magnetoresistance in film manganite/ferrite heterostructures

For a series of epitaxial and polycrystalline manganite/ferrite heterostructures grown on different substrates, the interelation between light transmission in the IR range and electrical resistance, magnetotransmission, and magnetoresistance has been studied in a temperature range of 80–385 K. It has been established that the temperature dependences of transmission and magnetotransmission in the manganite/ferrite heterostructures on different substrates are similar to the temperature dependences in the films of manganites on the same substrates. It has been shown that in a magnetic field of 8 kOe applied perpendicular to the surface of the epitaxial manganite/ferrite heterostructure the magnetotransmission increases by ～40% relative to its value in the single-layer epitaxial films.     

High-frequency heating and dynamic susceptibility of small La1 ? xAgyMnO3 + δ particles in the range of the magnetic phase transition

The nanoparticles of the lanthanum-silver manganites with the general formula La_{1 − x} Ag _y MnO_{3 + δ} (LAMO) that exhibit the Curie temperature T _C in the range 35…50°C, which is important for medical applications, are synthesized and studied. The heating kinetics of the LAMO aqueous suspensions under the action of the high-frequency (HF) magnetic field is experimentally studied and the self-stabilization in the vicinity of the Curie temperature is demonstrated. A sharp increase in the HF-absorption (specific absorption rate) is observed for the materials under study when approaching the Curie temperature from below. This effect is proven by direct measurements of the dynamic magnetic susceptibility in the critical range. The physical interpretations of the HF absorption are based on the hysteresis and oscillations of domain boundaries. It is demonstrated that the materials under study are promising for the medical hyperthermia with controlled heating temperature.     

Design and analysis of spatial encoding circuits for peak power reduction in on-chip buses

We propose various low-latency spatial encoder circuits based on bus-invert coding for reducing peak energy and current in on-chip buses with minimum penalty on total latency. The encoders are implemented in dual-rail domino logic with interfaces for static inputs and static buses. A spatial and temporally encoded dynamic bus technique is also proposed for higher performance targets. Comparisons to standard on-chip buses of various lengths with optimal repeater configurations at the 130-nm node show the energy-delay and peak current-delay design space in which the different encoder circuits are beneficial. A 9-mm spatially encoded static bus exhibits peak energy gains beyond that achievable through repeater optimization for a single-cycle operation at 1 GHz, with delay and energy overhead of the encoding included. For throughput-constrained buses, the spatially encoded static bus can provide up to 31% reduction in peak energy, while the spatially and temporally encoded dynamic bus yields peak current reductions of more than 50% for all bus lengths. The encoder circuits show good scaling properties since the performance penalty from encoding decreases with scaled interconnects.     

Stability indicating HPTLC determination of linezolid as bulk drug and in pharmaceutical dosage form

A simple, selective, precise, and stability-indicating high-performance thin layer chromatographic method of analysis of Linezolid both as a bulk drug and in formulations was developed and validated in pharmaceutical dosage form. The method employed TLC aluminium plates precoated with silica gel 60F-254 as the stationary phase. The solvent system consisted of toluene-acetone (5:5, v/v). This system was found to give compact spots for Linezolid (R_f value of 0.29 ± 0.01). Linezolid was subjected to acidic, alkali hydrolysis, oxidation, and photodegradation. The degraded products also were well separated from the pure drug. Densitometric analysis of Linezolid was conducted in the absorbance mode at 254 nm. The linear regression data for the calibration plots showed good linear relationship with r² = 0.997 ± 0.001 in the concentration range of 300-800 ng/spot. The mean value of correlation coefficient, slope, and intercept were 0.998 ± 0.003, 0.15 ± 0.009, and 19.52 ± 1.66 respectively. The method was validated for precision, accuracy, ruggedness, and recovery. The limits of detection and quantification were 20 ng/spot and 50 ng/spot, respectively. The drug undergoes degradation under acidic and basic conditions, oxidation and photo degradation. All the peaks of degraded product were resolved from the standard drug with significantly different R_f values. This indicates that the drug is susceptible to acid-base hydrolysis, oxidation, and photo degradation. Statistical analysis proves that the method is reproducible and selective for the estimation of the said drug. Because the method could effectively separate the drug from its degradation products, it can be used as a stability indicating one.     

Failure analysis of an ammonia refrigerant condenser tube

A detailed failure analysis was conducted on an ammonia refrigerant condenser tube component that failed catastrophically during its initial hours of operation. Evidence collected clearly demonstrated that the weld between a pipe and a dished end contained a sharp unfused region at its root (lack of penetration). Component failure had started from this weld defect. The hydrogen absorbed during welding facilitated crack initiation from this weld defect during storage of the component after welding. Poor weld toughness at the low operating temperature facilitated crack growth during startup, culminating in catastrophic failure as soon as the crack exceeded critical length.     

Albumin microbubble persistence during myocardial contrast echocardiography is associated with microvascular endothelial glycocalyx damage

BACKGROUND: We hypothesized that the persistence of albumin microbubbles within the myocardium during crystalloid cardioplegia (CP) infusion and ischemia-reperfusion (I-R) occurs because of endothelial injury. METHODS AND RESULTS: The myocardial transit rate of albumin microbubbles was measured in 18 dogs perfused with different CP solutions and in 12 dogs undergoing I-R. Electron microscopy with cationized ferritin labeling of the glycocalyx was performed in 9 additional dogs after CP perfusion and in 3 additional dogs undergoing I-R. Microbubble transit was markedly prolonged during crystalloid CP perfusion. The addition of whole blood to the CP solution accelerated the transit rate in a dose-dependent fashion (P<0.05), which was greater with venous than with arterial blood (P<0.05). The addition of plasma or red blood cells to CP solutions was less effective in improving transit rate than addition of whole blood (P<0.05). Microbubble transit rate was independent of the temperature, K+ content, pH, PO2, osmolality, viscosity, and flow rate of the perfusate. Similarly, a proportion of microbubbles persisted in the myocardium after I-R, which was related to the duration of ischemia (P<0.01) but not of reflow. Crystalloid CP perfusion and I-R resulted in extensive loss of the endothelial glycocalyx without other ultrastructural changes. This effect was partially reversed in the case of crystalloid CP when it was followed by blood CP. CONCLUSIONS: Sonicated albumin microbubbles persist within the myocardium in situations in which the endothelial glycocalyx is damaged. The measurement of the myocardial transit rate of albumin microbubbles may provide an in vivo assessment of endothelial glycocalyx damage.     

Microwave engineering

A brief history of microwave engineering is given. The impact of computer-aided design and monolithic microwave integrated circuits on microwave design is examined. The career potential of microwave engineering is discussed, along with suggestions for related studies that would be useful to the microwave engineer     

Low-power on-chip communication based on transition-aware global signaling (TAGS)

In this paper, we propose a new circuit structure, the transition aware global signaling (TAGS) receiver, that detects transitions at arbitrary switch points. The major performance advantage of this circuit occurs when it switches before the 50% point in the input transition. The TAGS receiver stores the next state of the line while quiet. Upon detection of a transition at the end of the line the output is temporarily driven by the stored next state. Transitions at the output of the receiver are much faster than at the end of the line since they are generated locally. Its ability to detect transitions before a standard inverter and locally generate them at its output, allows its use at the end of long interconnects with fewer repeaters for the same delay as the standard repeater paradigm. The need for fewer repeaters with the TAGS scheme results in lower power consumption for on-chip global communication, while also reducing the placement overhead involved with large buffer blocks. This is shown in the context of bus optimizations, where TAGS achieves up to 50% reduction in power compared to standard repeaters. In an industrial 0.13-/spl mu/m CMOS process, TAGS receivers enable 8-mm-long buses at 1.5-GHz clock rates without repeaters, while the traditional scheme required three repeaters on the line. An extensive analysis of crosstalk noise in the bus environment shows that TAGS can handle the noise levels produced in typical bus structures. Also, the variation of delay in the bus structure under worst-case power supply noise for the TAGS scheme is typically smaller than the delay variation using the standard repeater scheme.