Stochastic Modeling and Performance Analysis of Multimedia SoCs

International audienceQuality of video and audio output is a design-time constraint for portable multimedia devices. Unfortunately, there is a huge cost (e.g. buffer size) incurred to deterministically guarantee good playout quality; the worst-case workload and the timing behavior can be significantly larger than the average-case due to high variability in a multimedia system. In future mobile devices, the playout buffer size is expected to increase, so, buffer dimensioning will remain as an important problem in system design. We propose a probabilistic analytical framework that enables low-cost system design and provides bounds for playing acceptable multimedia quality. We compare our approach with a framework comprising both simulation and statistical model checking, built to simulate large embedded systems in detail. Our results show significant reduction in output buffer size compared to deterministic frameworks

Surface-charge-induced alteration of nanovortex patterning in nanoscale confinements with patterned wettability gradients

We characterize the generation of flow vortices in nanoscale confinements under the combined effects of patterned surface charge density and substrate wettability. Using molecular dynamics simulations, we elucidate the effects of ion solvation and steric interactions toward influencing the resultant transport characteristics, which are otherwise difficult to resolve using classical electrokinetic theory. We also evaluate the velocity slip (local and global) as well as vorticity parameters, in an effort to assess the implications of the generated flow structure from a pseudocontinuum viewpoint. Results from the present study are expected to provide valuable insights on augmentation of nanoscale mixing

Effect of interfacial Maxwell stress on time periodic electro-osmotic flow in a thin liquid film with a flat interface

Electro-osmotic flows (EOF) have seen remarkable applications in lab-on-a-chip based microdevices owing to their lack of moving components, durability, and nondispersive nature of the flow profiles under specifically designed conditions. However, such flows may typically suffer from classical Faradaic artifacts like electrolysis of the solvent, which affects the flow rate control. Such a problem has been seen to be overcome by employing time periodic EOFs. Electric field induced transport of a conductive liquid is another nontrivial problem that requires careful study of interfacial dynamics in response to such an oscillatory flow actuation. The present study highlights the role of electric field generated Maxwell stress and free surface potential along with the electric double layer thickness and forcing frequency, toward influencing the interfacial transport and fluid flow in free-surface electro-osmosis under a periodically varying external electric field, in a semi-analytical formalism. Our results reveal interesting regimes over which the pertinent interfacial phenomena as well as bulk transport characteristics may be favorably tuned by employing time varying electrical fields

Maxwell stress-induced flow control of a free surface electro-osmotic flow in a rectangular microchannel

Multiphase flow control is a challenging task in microfluidic systems. Application of such ideas in electro-osmotic actuation of multiphase flows, which involves a complex convolution of phenomena ranging from electro-chemistry to hydrodynamics, is even more tricky. Most of the existing studies in the field have limited their scope to the thin electric double layer (EDL) limit, where the role of ionic space charge distribution in the EDL is simplified to provide a slip velocity boundary condition at the substrate, and the role of the fluid–fluid interface is limited to continuity of velocity and hydrodynamic shear stress. In this study, electro-osmotic flow of two immiscible fluids, an electrolytic solution and an inert gas, are studied in a rectangular microchannel and the role of interfacial potential and Maxwell stress-generated dynamics is explored in a wide range of EDL thicknesses. A net stress term is used in the transport equations which includes the electric effects by Maxwell stress as well as the hydrodynamic stress. It is observed that the free surface, depending upon its potential may enhance the fluid velocity or act as a rigid wall. With the help of two-dimensional velocity contour plots, the role of various flow parameters on flow profile is discussed. Further, a parametric analysis of flow rate gives interesting insights into the flow rate reversal and control in such microfluidic devices

On two-liquid AC electroosmotic system for thin films

Lab‐on‐chip devices employ EOF for transportation and mixing of liquids. However, when a steady (DC) electric field is applied to the liquids, there are undesirable effects such as degradation of sample, electrolysis, bubble formation, etc. due to large magnitude of electric potential required to generate the flow. These effects can be averted by using a time‐periodic or AC electric field. Transport and mixing of nonconductive liquids remain a problem even with this technique. In the present study, a two‐liquid system bounded by two rigid plates, which act as substrates, is considered. The potential distribution is derived by assuming a Boltzmann charge distribution and using the Debye–Hückel linearization. Analytical solution of this time‐periodic system shows some effects of viscosity ratio and permittivity ratio on the velocity profile. Interfacial electrostatics is also found to play a significant role in deciding velocity gradients at the interface. High frequency of the applied electric field is observed to generate an approximately static velocity profile away from the Electric Double Layer (EDL).by Abhishek Navarkar, Sakir Amiroudine and Evgeny A. Demekhi

Pattern of prophylactic antibiotics usage in caesarean section: An observational study

Background: Caesarean section is the most important factor associated with postpartum bacterial infections, with a infection rate reported to be 1-25%, which is 5-20 times higher than that of vaginal delivery. Materials & Methods: It was a prospective observational single centre study. The data was collected from the patient’s file in the nursing station within the hospital premises. The hospital was a tertiary care hospital, West Bengal. The prospective study was conducted at a tertiary care hospital with all pregnant women undergoing elective and emergency caesarean section. The study was designed to assess the type of antibiotics was used prophylactically before undergoing a caesarean section. Interval between the time of administration of antibiotic & time of delivery was assessed. Data on the use of antibiotic prophylaxis in caesarean sections was collected using a customized proforma. Other data included were indication for caesarean section, route of administration of antibiotics, type of antibiotics, dosage of antibiotics, time of incision, and duration of operation. All the methods were compared to Hospital protocol and NICE protocol. Results: The maximum no.of patients were administered the combination of inj. cefotaxime & inj. metronidazole that is 49.8%. The mean time interval between administration of antibiotic and delivery (mean± s.d.) of the patients was 44.99±16.83 minutes with range 5-90 minutes and the median was 45 minutes. Most of the time interval 209 (68.5%) were as per hospital protocol which was statistically significant (Z=5.79; p=0.0001). Conclusion: Antibiotic prophylaxis significantly reduces the postpartum infection rate & thus reduces maternal morbidity & mortality in caesarean section. In this study conducted at a tertiary care hospital, the prophylactic antibiotic usage data showed that combination of cefotaxime & metronidazole is most frequently used. The study describes that the usage of prophylactic antibiotic combination cefotaxime & metronidazole are most appropriate & have compliance with hospital protocol & NICE protocol. Keywords: Antibiotic prophylaxis, postoperative infection, caesarean section, surgical site infection (SSI

Role of ultrasound guided transversus abdominis plane block as a component of multimodal analgesic regimen for lower segment caesarean section: a randomized double blind clinical study

Abstract Background While opioids are the mainstay for post-operative analgesia after lower segment caesarean section, they are associated with various untoward effects. Ultrasound guided transversus abdominis plane (TAP) block has been postulated to provide effective analgesia for caesarean section. We evaluated the analgesic efficacy of this block for post caesarean analgesia in a randomised controlled trial. Methods One hundred thirty-nine mothers undergoing caesarean delivery were randomised to receive TAP block with either 20 ml 0.375% ropivacaine or 20 ml saline after obtaining informed consent. All the subjects received a standard spinal anaesthetic and diclofenac was administered for post-operative pain. Breakthrough pain was treated with tramadol. Post-operatively, all the subjects were assessed at 0, 2, 4, 6, 8, 10, 12, 18 & 24 h. The primary outcome was the time to first analgesic request. The secondary measures of outcome were pain, nausea, sedation, number of doses of tramadol administered and satisfaction with the pain management. Results The median (interquartile range) time to first analgesic request was prolonged in the TAP group compared to the control group (p < 0.0001); 11 h (8,12) and 4 h (2.5,6) respectively. The median (interquartile range) number of doses of tramadol consumed in the TAP group was 0 (0,1) compared to 2 (1,2) in the control group (p < 0.0001). At all points in the study, pain scores both at rest and on movement were lower in the study group (p < 0.0001). Maternal satisfaction with pain relief was also higher in the study group (p 0.0002). One subject in the TAP group had convulsions following injection of local anaesthetic solution. She was managed conservatively with supportive treatment following which she recovered. Conclusion TAP block reduces pain, prolongs the duration of analgesia and decreases supplemental opioid consumption when used for multimodal analgesia for pain relief after caesarean section. However, the risk of local anaesthetic systemic toxicity remains unknown with this block. Hence larger safety trials and measures to limit this complication need to be ascertained. Trial registration The trial was registered with the Clinical Trial Registry of India (CTRI/2017/03/008194) on 23/03/2017 (trial registered retrospectively)

A Study of the indications of caesarean section in a tertiary care hospital at West Bengal: An observational study

Background: In recent decades, we have observed a remarkable increase in the rate of caesarean section (CS) in both developed and developing countries, especially in India.&nbsp; Its prevalence has increased alarmingly in the last few years, which has motivated this research to identify the indications and determinants, influencing cesarean section delivery in the study area and determine the associated correlates for emergency and elective cesarean sections. Materials &amp; Methods: The prospective study was conducted at a tertiary care hospital with all pregnant women undergoing elective and emergency caesarean section. Interval between the time of administration of antibiotic &amp; time of delivery was assessed. Data on the use of antibiotic prophylaxis in caesarean sections was collected using a customized proforma. Other data included were indication for caesarean section, route of administration of antibiotics, type of antibiotics, dosage of antibiotics, time of incision, and duration of operation. All the methods were compared to Hospital protocol and NICE protocol.&nbsp; Its prevalence has increased alarmingly in the last few years, which has motivated this research to identify the indications and determinants, influencing cesarean section delivery in the study area and determine the associated correlates for emergency and elective cesarean sections. Results were expressed as proportions, percentages &amp; as averages +/- standard deviation (SD) with corresponding ranges. Results: The mean age (mean ± s.d.) of the patients was 28.94±3.88 years with range 19 - 42 years and the median age was 29 years. Test of proportion showed that proportion of single gravidity 216(70.8%) was significantly higher than that of multi-gravidity 89(29.2%) (Z=8.74;p=0.000001).&nbsp; Most of the caesarean section 26(8.5%) were underwent as per maternal wish (Z=1.21;p=0.47). Most of the patients 280(91.8%) had intact membrane as compared to ruptured membrane 25(8.2%) (Z=10.19;p=0.000001). The mean duration of surgery (mean± s.d.) of the patients was 75.13±16.96 minutes with range 35-148 minutes and the median was 75 minutes. Most of the surgeries 250 (82%) were performed between 60-89 minutes which was significantly higher (Z=8.04;p=0.00001). Conclusion: Caesarean sections are effective in saving maternal and infant lives, but only when they are required for medically indicated reasons. Unnecessary cesarean section may have an adverse impact upon maternal, neonatal, and infant morbidity and mortality. The high cost of cesarean section may result in catastrophic health expenditure for families and additional pressure upon health systems, especially in low- and middle-income countries