253 research outputs found
A Digitally Assisted, Signal Folding Neural Recording Amplifier
No full textA novel signal folding and reconstruction scheme for neural recording applications that exploits the 1/f(n) characteristics of neural signals is described in this paper. The amplified output is 'folded' into a predefined range of voltages by using comparison and reset circuits along with the core amplifier. After this output signal is digitized and transmitted, a reconstruction algorithm can be applied in the digital domain to recover the amplified signal from the folded waveform. This scheme enables the use of an analog-to-digital convertor with less number of bits for the same effective dynamic range. It also reduces the transmission data rate of the recording chip. Both of these features allow power and area savings at the system level. Other advantages of the proposed topology are increased reliability due to the removal of pseudo-resistors, lower harmonic distortion and low-voltage operation. An analysis of the reconstruction error introduced by this scheme is presented along with a behavioral model to provide a quick estimate of the post reconstruction dynamic range. Measurement results from two different core amplifier designs in 65 nm and 180 nm CMOS processes are presented to prove the generality of the proposed scheme in the neural recording applications. Operating from a 1 V power supply, the amplifier in 180 nm CMOS has a gain of 54.2 dB, bandwidth of 5.7 kHz, input referred noise of 3.8 mu V-rms and power dissipation of 2.52 mu W leading to a NEF of 3.1 in spike band. It exhibits a dynamic range of 66 dB and maximum SNDR of 43 dB in LFP band. It also reduces system level power #by reducing the number of bits in the ADC by 2# as well as data rate to 80% of a conventional design. In vivo measurements validate the ability of this amplifier to simultaneously record spike and LFP signals
An artifact-suppressed stimulator for simultaneous neural recording and stimulation systems
No full textThis paper proposes an artifact-suppressed stimulator with a referenced and tuned push-pull stimulation (RTPPS) scheme where a tri-polar electrode is employed. The stimulation pulses delivered to two working electrodes are complementary and thus one counteracts with the other to suppress the artifact at the recording site. The prototype stimulator chip is implemented in 0.18-μm CMOS process technology. In-vivo experiments are carried out with the chip to demonstrate the proposed artifact-suppression technique in a simultaneous neural recording and stimulation system. The results show that the stimulation artifact can be greatly reduced. The amplitude of the measured stimulation artifact is therefore constrained in a negligible level (10%-20%) compared to recorded neural spikes
Minimal Effects on Human Memory Following Long-Term Living at Moderate Altitude
No full textZhang, Jiaxing, Haichen Liu, Xiaodan Yan, and Xuchu Weng. Minimal effects on human memory follwing long-term living at moderate altitude. High Alt. Med. Biol. 12:37-43, 2011.-A number of studies describe memory deficits at extremely high altitudes. However, little is known about the effect of long-term living at moderate altitude (MA). The subjects for this study were 52 college students originally from sea level (SL), but studying at a MA of 2260 m over a 7-month period, with a return to SL for 30 days in the middle of the period. Fifty-two matched college students who stayed at SL all the time were the control group. The neuropsychological battery of assessments included the Chinese revised version of Wechsler Memory Scale tests (WMS-CR), verbal and spatial two-back working memory tests, long-term explicit memory (word recall and recognition of words, faces, and pictures) tests, Rey Auditory Verbal Learning test, Rey-Osterrieth Complex Figure (ROCF) test, degraded picture naming test, and the Serial Reaction Time Test. We found that the MA subjects showed significantly poorer performances than SL controls only in short-term visual construction assessed in the visual reproduction test from WMS-CR and in the ROCF immediate test. There were no significant differences in all other tasks between the MA group and SL group. These findings suggest that long-term hypoxic exposure at moderate altitude has minimal effects on human memory
Family altruism and incentives
No full textThe author builds on the altruistic model of the family, to explore the strategic interaction between altruistic parents, and selfish children, when children's efforts are endogenous. If there is uncertainty about the amount of income the children will realize, and if parents have imperfect information, the children have an incentive to exert little effort, and to rely on their parent's altruistically motivated transfers. Because of this, parents face a tradeoff between the insurance that bequests implicitly provide their children, and the disincentive to work prompted by their altruism. The author shows that if parents can credibly commit to a pattern of transfers, they will choose not to compensate children in bad outcomes, as much as predicted by the standard (no uncertainty, no asymmetric information) dynastic model of the family. Alternatively, parents may choose to forgo any insurance, and offer a fixed level of bequest, to elicit greater effort from their children. The optimal transfers structure that the author derives, reconciles the predictions of the altruistic family model, with much of the existing evidence on inter-generational transfers, which suggests that parents compensate only partially, or not at all, for earnings differentials among their children. Moreover, the author shows that Ricardian equivalence holds in this setup, except when non-negativity constraints are binding.Economic Theory&Research,Environmental Economics&Policies,Health Economics&Finance,Educational Sciences,Safety Nets and Transfers
Can reforming global institutions help developing countries share more in the benefits from globalization?
No full textGlobalization could significantly expand trade, international investment, and technological advances, but the gains from global integration have been unevenly distributed across and within nations. Greater global interdependence has also brought greater macroeconomic volatility, resulting in several serious financial crises in the second half of the 1990s. The global matrix of Bretton Woods and United Nations institutions that developed starting in the 1940s, formed under a different balance of power, in a world of fixed exchange rates and limited capital mobility. Since the 1960s regional financial institutions have emerged because of the greater autonomy of different regions and the greater financial needs of development. The author reviews different proposals for reform of the international financial institutions and changes in the roles of the International Monetary Fund (IMF) and the World Bank. He highlights the implications for developing countries of (1) Policy conditionality. (2) The countercyclical role of multilaterals'lending. (3) Greater lending to middle-income than to low-income developing countries. (3) Access to liquidity at times of crisis. (4) Mechanisms for giving low-income countries a greater voice in IMF and World Bank decisionmaking. The author streses the overlapping responsibilities of the Bretton Woods and regional financial institutions and the need to reassess the allocation of responsibilities and to develop better coordination mechanisms between these institutions. Those designing institutional reform must consider the corporate capabilities of each type of institution. The corporate cultures of global and regional institutions differ. So does the kind of knowledge they generate and disseminate, and so do patterns of interactions with, and mechanisms for representation of, client countries.Finally, the author calls attention to the need to harmonize national and global growth-oriented policies in a way that reduces volatility and promotes social equity.Environmental Economics&Policies,Governance Indicators,Financial Intermediation,Economic Theory&Research,Banks&Banking Reform
High-Mobility TCO-Based Contacting Schemes for c-Si Solar Cells
No full textIn the efficiency-driven photovoltaic (PV) industry, the market dominating crystalline silicon (c-Si) technology has been developing towards PV devices with carrier-selective passivating contacts (CSPCs). Especially, the silicon heterojunction (SHJ) solar cell, based on hydrogenated amorphous silicon (a-Si:H) contact stacks, and the poly-Si solar cell, based on ultrathin SiOx/poly-Si passivating contacts, pave the way for power conversion efficiencies above 26%, approaching the theoretical limit of the c-Si solar cell. In case of front/back-contacted (FBC) architectures, to minimize the optical parasitic absorption at the emitter and/or surface field side(s), thin doped silicon layers are normally applied, which exhibit high sheet resistance. Accordingly, transparent conductive oxide (TCO) layers are required to ensure sufficient lateral carrier transport towards the metal electrodes. However, problems still exist in contacting schemes for high-efficiency solar cell design towards future multi-terawatt production of PV modules, regarding the development of TCO layer with high carrier mobility (μ), its integration into specific device structures, and more importantly, the material availability. In this work, we present three types of TCO materials. They are tin-, fluorine- and tungsten-doped indium oxide layers, namely, ITO, IFO, and IWO. RF magnetron sputtering approach has been utilized to deposit the films. The TCOs are integrated into both low thermal-budget SHJ and high thermal-budget poly-Si solar cells. Further, to address the sustainability implication related to indiumconsumption, we propose a strategy of bifacial SHJ solar cell with reduced TCO use. Meanwhile, to reduce silver (Ag) consumption, as well as to reach good solar cell performance in our laboratory, we have developed a platformfor bifacial copper (Cu)-platingmetallization approach. Specific results are summarized as follows...Photovoltaic Materials and Device
Dynamical mechanical characteristic simulation and analysis of the low voltage switch under vibration and shock conditions
No full textEffect of Low-Frequency Electrical Stimulation Combined with Abdominal Acupoint Massage on Postoperative Gastrointestinal Function Recovery after Cesarean Section: A Prospective Randomized Study
No full textBackground: This study aimed to investigate the effects of low-frequency electrical stimulation combined with abdominal acupoint massage on the recovery of gastrointestinal function following cesarean section. Methods: A total of 60 postoperative patients were randomly assigned to either the control group (group A, n = 30) or the observation group (group B, n = 30) between January 2021 to December 2021. The control group received conventional interventions, while the observation group received a nursing intervention consisting of low-frequency electrical stimulation combined with abdominal acupoint massage starting at 10–12 hours after the operation. The primary outcomes included the time to first bowel sound, time to flatus, time to defecation, and time to lactation. The secondary outcomes included postoperative visual analogue scale (VAS) pain scores, the rate and severity of abdominal distension, and serum levels of prolactin (PRL) and vasoactive intestinal peptide (VIP). Results: The observation group had significantly earlier restoration of bowel sounds, passage of first flatus, and first defecation than the control group (p < 0.001). The VAS scores in the observation group were significantly lower than those in the control group at 24 h, 48 h, and 72 h after the operation (p < 0.001). The incidence of abdominal distension in the observation group (13.3%, 4/30) was lower than that in the control group (36.7%, 11/30) (p < 0.05). Furthermore, compared to the control group, the observation group showed a significant increase in serum PRL levels and a significant decrease in VIP levels after treatment (p < 0.001). Conclusions: The application of low-frequency electrical stimulation combined with abdominal acupoint massage after cesarean section can expedite the recovery of gastrointestinal function and reduce pain and complications, such as abdominal distension. This approach can be used in clinical practice to accelerate the recovery of intestinal function after cesarean section. Clinical Trial Registration: The study was registered with the ISRCTN registry (https://www.isrctn.com/), registration number: ISRCTN16533743
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