Statins have a variety of cardioprotective properties following chronic treatment. In contrast, little is known about the acute effects. Reperfusion acutely injures the heart by activation of neutrophils as well as endothelial cells. Because statins are known to influence the processes pathogenetically involved, we hypothesized that acute application of statins attenuates the sequelae of cardiac reperfusion. In rats, myocardial infarction (MI) was induced by ligature of the left coronary artery followed by reperfusion. Myocardial blood flow (MBF) was determined by H 2 clearance and regional myocardial function (fractional thickening, FT) by pulsed Doppler. MI size was measured by triphenyltetrazolium chloride (TTC) staining, neutrophil extravasation by determination of myeloperoxidase (MPO) activity, and nitric oxide generation via measurement of cGMP. Treatment with fluvastatin, administered intravenously 20 min before the onset of ischemia, significantly attenuated the decline of FT and MBF at the end of the reperfusion period and significantly reduced MI size. Furthermore, fluvastatin induced a significant reduction of MPO activity and an increase of cGMP level compared with the control group. The effect of fluvastatin was completely abolished following pretreatment of N G -nitro-L-arginine methyl ester (L-NAME). These findings suggest that acute application of fluvastatin reduces MI size and attenuates reperfusion injury. We propose that the underlying mechanism is at least partially an inhibition of inflammation and endothelial dysfunction by preventing the activation and extravasation of neutrophils.

A reduced availability of tetrahydrobiopterin (BH4), an essential cofactor for NO-synthesis, is causally involved in the development of endothelial dysfunction associated with ischemia/reperfusion. We, therefore, investigated the effect of sepiapterin, a substrate for BH4 synthesis, on postischemic injury in myocardial infarction and myocardial stunning. In rats, myocardial stunning was induced by repetitive ischemia (5 x 10-min ligature of the left coronary artery, 5 x 20-min reperfusion) and myocardial infarction by 50-min ligature and 60-min reperfusion. Myocardial blood flow was determined by H2-clearance, regional myocardial function by pulsed Doppler and infarct size by tetrazolium staining. Myeloperoxidase (MPO) activity was measured as a marker of neutrophil extravasation. cGMP was determined in rat serum as an indicator of increased NO synthesis. In animals treated with sepiapterin, regional myocardial function was significantly improved in both myocardial stunning and infarction and infarct size was significantly reduced. MPO activity decreased with sepiapterin treatment in both models. The systemic level of cGMP was reduced both following myocardial stunning and myocardial infarction in the control group. Pretreatment with sepiapterin induced a significant increase of cGMP level at the end of the protocol in both models. Substitution of sepiapterin reduces postischemic injury both in myocardial stunning and infarction apparently by ameliorating the availability of NO, thereby attenuating the activation of neutrophils in ischemia/reperfusion.

Two different solder alloys, Sn-37Pb and Sn-4Ag-0.5Cu, were used to joint p-and n-type bismuth telluride-based thermoelements with copper. SnTe and Pb 1−x Sn x Te were identified to be the major interfacial compounds for the Sn-Ag-Cu and Sn-Pb soldered junctions, respectively. The contact resistivity measured is around 10 −4 to 10 −5 ⍀ cm 2 , which depends on both the thickness and composition of interfacial compounds. The study shall lead to the effective strategy for choosing appropriate solder alloy systems to improve the contact property of bismuth telluride-based thermoelectric coolers.Thermoelectric coolers have been extensively used to cool microsensors and optoelectronic devices due to the advantages of miniaturization and short response time. 1-3 Typical thermoelectric coolers ͑TECs͒ are made of a number of p-and n-type thermoelements which are jointed to copper conductors by soldering reaction and arranged in a square array between two ceramic plates. Some solders such as Sn-Bi, Sn-Pb, and Sn-Ag alloys are commonly employed in assembling TECs. The electrical contact resistance of soldered junctions, in general, is negligible in comparison to the total resistance of thermoelements in typical TECs. However, the contact effect may not be ignored when short or thin-film-type thermoelements are used in high-power TECs. The maximum cooling efficiency of TECs depends on the thermoelectric figure-of-merit ͑FoM͒ of thermoelements. The higher the thermoelectric FoM, the better cooling performance the TEC can achieve. By considering the electrical contact effect, the effective FoM of the thermoelements ͑Z eff ͒ is given by 4where Z, , and l are thermoelectric FoM, resistivity, and length of thermoelements, respectively, and c is the contact resistivity of soldered junctions. The soldered junctions of c ͑=10 −5 ⍀ cm 2 ͒ lead to a 6% decrease in FoM for the regular 1.6 mm thick thermoelements ͑ = 10 −3 ⍀ cm͒ but an almost 33% reduction in FoM for 200 m thick ones. Bismuth telluride-based compounds are the best known thermoelements for TEC applications. It has been reported that the contact resistivity of nickel-plated bismuth telluride-based thermoelements solder-jointed with Sn-Pb alloy is around 10 −5 to 10 −6 ⍀ cm 2 . 5 The plated nickel layer serves as a diffusion barrier that prevents interdiffusion and chemical reaction between the solder and thermoelements. Buist et al. have measured the contact resistivity of 1-2 ϫ 10 −4 ⍀ cm 2 for bare bismuth telluride-based thermoelements soldered with Bi-Sn alloy and 5-10 ϫ 10 −5 ⍀ cm 2 for nickel-plated thermoelements soldered with Sn-Pb alloy. 6 Nevertheless, their work did not provide a detailed insight into the origin of the contact resistance for different thermoelement/Cu soldered junctions. Alieva et al. have investigated the electrical properties and microstructure of the interfaces between Bi 0.5 Sb 1.5 Te 3 ͑Bi 2 Te 2.7 Se 0.3 ͒ and Bi-Sn-based alloys with various Pb, Cd, and Sb ingredients. 7 They found that theinterfacial compounds were mainly tellurides, suc...

Hearing loss is one of the most common conditions affecting older adults worldwide. Frequent complaints from the users of modern hearing aids include poor speech intelligibility in noisy environments and high cost, among other issues. However, the signal processing and audiological research needed to address these problems has long been hampered by proprietary development systems, underpowered embedded processors, and the difficulty of performing tests in real-world acoustical environments. To facilitate existing research in hearing healthcare and enable new investigations beyond what is currently possible, we have developed a modern, open-source hearing research platform, Open Speech Platform (OSP). This paper presents the system design of the complete OSP wearable platform, from hardware through firmware and software to user applications. The platform provides a complete suite of basic and advanced hearing aid features which can be adapted by researchers. It serves web apps directly from a hotspot on the wearable hardware, enabling users and researchers to control the system in real time. In addition, it can simultaneously acquire high-quality electroencephalography (EEG) or other electrophysiological signals closely synchronized to the audio. All of these features are provided in a wearable form factor with enough battery life for hours of operation in the field. INDEX TERMS Hearing aids (HAs), wearable computers, speech processing, field programmable gate arrays (FPGAs), electrophysiology (EEG), system-level design, open source hardware, embedded software, Internet of Things, research initiatives.

Abstract-In hearing aids (HAs), the acoustic coupling between the microphone and the receiver results in the system becoming unstable under certain conditions and causes artifacts commonly referred to as whistling or howling. The least mean square (LMS) class of algorithms is commonly used to mitigate this by providing adaptive feedback cancellation (AFC). The speech quality after AFC and the amount of added stable gain (ASG) with AFC are used to assess these algorithms. In this paper, we introduce a variant of the LMS that promotes sparsity in estimating the acoustic feedback path. By using the lp norm as a diversity measure, the approach does not enforce, but takes advantage of sparsity when it exists. The performance in terms of speech quality, misalignment, and ASG of the proposed algorithm is compared with other proportionate-type LMS algorithms which also leverage sparsity in the feedback path. We demonstrate faster convergence compared with those algorithms, quality improvement of about 0.25 (on a 0-1 objective scale of the hearing-aid speech quality index (HASQI)), and about 5 dB ASG improvement compared with the normalized LMS (NLMS).