A Study to Observe Pulse Pressure Variation after Induction with Propofol for General Anesthesia

Background and Aims: Pulse pressure variation (PPV) is a reliable and predictive dynamic parameter presently being utilized for fluid responsiveness. In the operating room, fluid administration based on PPV monitoring helps the physician in deciding whether to volume resuscitate or use interventions in patients undergoing surgery. Propofol is an intravenous induction agent which lowers blood pressure. There are multiple causes such as depression in cardiac output, and peripheral vasodilatation for hypotension. We undertook this study to observe the utility of PPV as a guide to fluid therapy after propofol induction. Primary outcome of our study was to monitor PPV as a marker of fluid responsiveness for the hypotension caused by propofol induction. Secondary outcome included the correlation of PPV with other hemodynamic parameters like heart rate (HR), systolic blood pressure (SBP), and diastolic blood pressure (DBP);after induction with propofol at regular interval of time. Methods: A total number of 90 patients were recruited. Either of the radial artery was then cannulated under local anaesthesia with 20G VygonLeadercath arterial cannula and invasive monitoring transduced. A baseline recording of heart rate (HR), systolic blood pressure (SBP), diastolic blood pressure (DBP) and PPV was then recorded. Patients were then induced with predetermined doses of propofol (2 mg/kg) and recordings of HR, SBP, DBP, and PPV were taken at 5, 10 and 15 minutes. Results: Intraoperatively, PPV was significantly higher at 5 minutes and significantly lower at 15 minutes after induction. It was observed that there were no statistically significant correlations between PPV and SBP or DBP. PPV was strongly and directly associated with HR. Conclusion: We were able to establish that PPV predicts fluid responsiveness in hypotension caused by propofol induction;and can be used to administer fluid therapy in managing such hypotension. However, PPV was not directly correlated with hypotension subsequent to propofol administration.

Assessment of Stroke Volume Variation Perioperatively by Using Arterial Pressure with Cardiac Output

Objective To observe the sensitivity of stroke volume variation(SVV) for assessing volume change during induction period of general anesthesia. Methods Patients who underwent orthopaedic surgery under general anesthesia and mechanical ventilation were divided into two groups randomly. Patients in the group Ⅰwere subjected to progressive central hypovolemia and correction of hypovolemia sequentially; patients in the Group Ⅱ were exposed to hypervolemia alone. Each step was implemented after 5 minutes when the hemodynamics was stable. SVV and cardiac index(CI) were recorded, and Pearson's product-moment correlation was used to analyze correlation between SVV and CI. Results Forty patients were included in this study, 20 cases in each group. For group Ⅰ patients, SVV was increased significantly along with blood volume reduction, and changes in CI were negatively correlated with changes in SVV(r=-0.605, P<0.01); SVV decreased significantly along with correction of blood volume; changes in CI were negatively correlated with changes in SVV(r=-0.651, P<0.01). For group Ⅱ patients, along with blood volume increase, SVV did not change significantly; changes in CI revealed no significant correlation with changes in SVV(r=0.067, P>0.05). Conclusion SVV is a useful indicator for hypovolemia, but not for hypervolemia.

Variation law of gas holdup in an autoclave during the pressure leaching process by using a mixed-flow agitator

The multiphase reaction process of pressure leaching is mainly carried out in the liquid phase. Therefore, gas holdup is essential for the gas–liquid–solid phase reaction and the extraction rate of valuable metals. In this paper, a transparent quartz autoclave, a six blades disc turbine-type agitator, and a high-speed camera were used to investigate the gas holdup of the pressure leaching process. Furthermore, experiments determining the effects of agitation rate, temperature, and oxygen partial pressure on gas holdup were carried out. The results showed that when the agitation rate increased from 350 to 600 r/min, the gas holdup increased from 0.10% to 0.64%. When the temperature increased from 363 to 423 K, the gas holdup increased from 0.14% to 0.20%. When the oxygen partial pressure increased from 0.1 to 0.8 MPa, the gas holdup increased from 0.13% to 0.19%. A similar criteria relationship was established by Homogeneous Principle and Buckingham's theorem. Comprehensively, empirical equation of gas holdup was deduced on the basis of experimental data and the similarity theory, where the criterion equation was determined as ε=4.54×10^(-11)n^(3.65)T^(2.08)P_g^(0.18). It can be seen from the formula that agitation rate made the most important impact on gas holdup in the pressure leaching process using the mixed-flow agitator.

Analysis on mechanisms of anomalous variations of tropopause pressure over the Tibetan Plateau during summer in Northern Hemisphere

Using the monthly mean data from NCEP-NCAR reanalysis, through building tropopause pressure index, we investigated the mechanisms of anomalous variations of tropopause pressure over the Tibetan Plateau during summer in Northem Hemisphere. For comparative analysis we selected representative years of 1992 and 1998 to study, and they were respectively the highest and the lowest year oftropopause pressure anomaly over the Tibetan Plateau. The results are summarized as follows： （1） Over the Tibetan Plateau, the variations of tropopause pressure are well correlated respectively with anomalous temperature and geopotential height in both troposphere and stratosphere. Besides, the anomalous tropopause pressure has also close relation with anomalous surface temperature in the Tibetan Plateau. In 1992, the surface temperature was anomalously low, correspondingly, the tropopause pressure over the Tibetan Plateau was anomalously high; but in 1998, the opposite was the case. （2） Over the Tibetan Plateau, the correlation of tropopause pressure and OLR （Outgoing Longwave Radiation） is found to be positive. Furthermore, by further diagnosing the circulation fields between 850 hPa and 200 hPa levels and the whole troposphere vapour field, we found out that the anomalously high tropopause pressure in 1992 corresponded to the anticyclonic divergence of low level wind fields and the cyclonic convergence of high level wind fields, and coupled with divergence of the whole troposphere vapour fields along with the South Asian High weakened at the same time. While in 1998, the case was opposite to that in 1992. These facts indicated that the anomalous convection resulted in the significant difference oftropopause pressure in 1992 and 1998 over the Tibetan Plateau. （3） The vertically integrated heat budget anomalies were responsible for explaining tropopause pressure anomalies in 1992 and 1998 over the Tibetan Plateau.

Anesthetics management of a renal angiomyolipoma using pulse pressure variation and non-invasive cardiac output monitoring: A case report

BACKGROUND Hypovolemic shock can lead to life-threatening organ dysfunction,and adequate fluid administration is a fundamental therapy.Traditionally,parameters such as vital signs,central venous pressure,and urine output have been used to estimate intravascular volume.Recently,pulse pressure variation(PPV)and non-invasive cardiac monitoring devices have been introduced.In this case report,we introduce a patient with massive active bleeding from giant renal angiomyolipoma(AML).During emergent nephrectomy,we used non-invasive cardiac monitoring with CSN-1901(Nihon Kohden,Tokyo,Japan)and PPV to evaluate the patient's intravascular volume status to achieve optimal fluid management.CASE SUMMARY A 30-year-old male patient with giant AML with active bleeding was referred to the emergency room complaining of severe abdominal pain and spontaneous abdominal distension.AML was diagnosed by computed tomography,and emergent nephrectomy was scheduled.Massive bleeding was expected so we decided to use non-invasive cardiac monitoring and PPV to assist fluid therapy because they are relatively easy and fast compared to invasive cardiac monitoring.During the surgery,6000 mL of estimated blood loss occurred.Along with the patient's vital signs and laboratory results,we monitored cardiac output,cardiac output,stroke volume,stroke volume index with a non-invasive cardiac monitoring device,and PPV using an intra-arterial catheter to evaluate intravascular volume status of the patient to compensate for massive bleeding.CONCLUSION In addition to traditional parameters,non-invasive cardiac monitoring and PPV are useful methods to evaluate patient's intravascular volume status and provideguidance for intraoperative management of hypovolemic shock patients.

Effect of periodic wide atmospheric pressure change on CO emission in closed goaf

Atmospheric pressure fuctuation is one of the most important factors afecting the climate environment and gas emission in the fre area.To obtain the infuence rule of the surface atmospheric pressure change on the gas sampling and abnormal emission in the mine closed goaf,the No.1 coal mine in Dananhu was taken as the research object.Using Fourier transform and Fisher harmonic analysis and other statistical methods,the infuence of the periodic variation of atmospheric pressure on the gas leakage and outfow in the closed goaf was studied.The results showed that there were three atmospheric pressure periods of 15.2 d,1 d and 182.2 d,and the probability was greater than 95%.The time period with the highest number of atmospheric pressure peaks was 7:00–8:00,which accounted for 20.2%of total occurrence number in a day.And the time periods with the highest number of atmospheric pressure trough were 2:00,15:00 and 16:00,accounting for 27.4%.The peak-to-trough transition time was mainly concentrated around 6 h,and the diurnal variation curve of atmospheric pressure was mainly bimodal.The atmospheric pressure change rate was mostly concentrated in 10–50 Pa/h.It was determined that the distance that the gas sampling pipe was pre-laid into the inner side of the closed wall should be greater than 44.4 m,and the CO concentration and atmospheric pressure in the closed goaf were both periodic and negative with atmospheric pressure.The research results have important guiding signifcance for the monitoring,early warning and environmental protection of the goaf.

Spatial and temporal variation process of seabed dynamic response induced by the internal solitary wave

Internal solitary wave(ISW)is often accompanied by huge energy transport,which will change the pore water pressure in the seabed.Based on the two-dimensional Biot consolidation theory,the excess pore water pressure in seabed was simulated,and the spatiotemporal distribution characteristics of excess pore water pressure was studied.As the parameters of both ISW and seabed can affect the excess pore water pressure,the distribution of pore water pressure showed both dissipation and phase lag.And parametric studies were done on these two phenomena.Due to influenced by the phase lag of excess pore water pressure,the penetration depth under the site of northern South China Sea with total water depth 327 m,induced by typical internal solitary wave increased by 26.19%,53.27%and 149.86%from T_(0)to T_(0.5)in sand silt,clayey silt and fine sand seabed,respectively.That means the effect of ISW on seabed will be underestimated if we only take into accout the penetration depth under ISW trough,especially for fine sand seabed.In addition,the concept of“amplitude-depth ratio”had been introduced to describe the influence of ISW on seabed dynamic response in the actual marine environment.In present study,it is negatively correlated with the excess pore water pressure,and an ISW with smaller amplitude-depth ratio can wide the range of lateral impacts.Our study results help understand the seabed damage induced by the interaction between ISW and seabed.

EFFECT OF THIRD TRIMESTER OF PREGNANCYON DIURNAL VARIATION OF OCULAR PRESSURE

This study was planned to evaluate the effect of pregnancy on diurnal variation of intraocular pressure(IOP) after placing control on all the IOP affecting factors. The IOP was measured with the Goldmann ap-planation tonometer. Both in the control and 3rd trimester subjects, the peak of mean IOP appeared in themorning when the subJects waked, and the trough of mean IOP happened at 2 am to 4 am. The diurnal in-traocular pressure curves revealed that the lOP peaks were 15.4±0. 9 and 12. 9±0. 6 mmHg in the controland third trimester pregnant subjects, respectively. Whereas the trough were 13.1±0. 4 and 11. 8±0. 3mmHg, respectively. The mean diurnal variation were 2. 3±0. 6 mmHg (P<O.01 ), and 1.1±0. 8mmHg in the control and third trimester subjects, respectively. There are two main findings of presentstudy: first, compared with non-pregnant control subjects, the IOP was significantly lower (P<0.001 ) inthe third trimester pregnant subjects. Second, in the third trimester of pregnancy, the lower IOP level wasassociated with the less degree of IOP fluctuations at various hours of the day.

SPATIAL VARIATION OF WINTER SEA SURFACE TEMPERATURE IN NORTH PACIFIC AND ITS RELATION TO ATMOSPHERIC OSCILLATION MODES

The spatial variation of sea surface temperature anomalies(SSTA) in the North Pacific Ocean during winter is investigated using the EOF decomposition method.The first two main modes of SSTA are associated with Pacific Decadal Oscillation(PDO) mode and North Pacific Gyre Oscillation(NPGO) mode,respectively.Moreover,the first mode(PDO) is switched to the second mode(NPGO),a dominant mode after mid-1980.The mechanism of the modes' transition is analyzed.As the two oceanic modes are forced by the Aleutian Low(AL) and North Pacific Oscillation(NPO) modes,the AR-1 model is further used to examine the possible effect and mechanism of AL and NPO in generating the PDO and NPGO.The results show that compared to the NPO,the AL plays a more important role in generating the NPGO mode since the 1970s.Likewise,both the AL and NPO affect the PDO mode since the 1980s.

Critical Temperature Characteristics of Layered High-Temperature Superconductor Under Pressure

我们考虑一辆 Ginzburg 四轮马车在压力下面修改了分层的高温度的超导体的模型。我们理论上学习了在压力和分层的高温度的超导体的温度之间的关系。如果压力不是一个常数，我们有在压力和分层的高温度的超导体的温度之间的二次的方程的一种关系。在一种特殊情况中，我们发现批评温度与进一步增加压力减少。在另一种特殊情况中，批评温度与进一步增加压力增加。

Predictive performance of the variation rate of the driving pressure on the outcome of invasive mechanical ventilation in patients with acute respiratory distress syndrome

Purpose:To assess the value of the driving pressure variation rate(ΔP%)in predicting the outcome of weaning from invasive mechanical ventilation in patients with acute respiratory distress syndrome.Methods:In this case-control study,a total of 35 patients with moderate-severe acute respiratory distress syndrome were admitted to the intensive care unit between January 2022 and December 2022 and received invasive mechanical ventilation for at least 48 h were enrolled.Patients were divided into successful weaning group and failed weaning group depending on whether they could be removed from ventilator support within 14 days.Outcome measures including driving pressure,PaO2:FiO2,and positive end-expiratory pressure,etc.were assessed every 24 h from day 0 to day 14 until successful weaning was achieved.The measurement data of non-normal distribution were presented as median(Q1,Q3),and the differences between groups were compared by Wilcoxon rank sum test.And categorical data use the Chi-square test or Fisher's exact test to compare.The predictive value ofΔP%in predicting the outcome of weaning from the ventilator was analyzed using receiver operating characteristic curves.Results:Of the total 35 patients included in the study,17 were successful vs.18 failed in weaning from a ventilator after 14 days of mechanical ventilation.The cut-off values of the medianΔP%measured by Operator 1 vs.Operator 2 in the first 4 days were≥4.17%and 4.55%,respectively(p<0.001),with the area under curve of 0.804(sensitivity of 88.2%,specificity of 64.7%)and 0.770(sensitivity of 88.2%,specificity of 64.7%),respectively.There was a significant difference in mechanical ventilation duration between the successful weaning group and the failure weaning group(8(6,13)vs.12(7.5,17.3),p=0.043).The incidence of ventilator-associated pneumonia in the successful weaning group was significantly lower than in the failed weaning group(0.2‰vs.2.3‰,p=0.001).There was a significant difference noted between these 2 groups in the 28-day mortality(11.8%vs.66.7%,p=0.003).Conclusion:The medianΔP%in the first 4 days of mechanical ventilation showed good predictive performance in predicting the outcome of weaning from mechanical ventilation within 14 days.Further study is needed to confirm this finding.

Pressure dissociation of dense hydrogen

The self-consistent fluid variational model （SFVM） has been used to describe the pressure dissociation of dense hydrogen at high temperatures. This paper focuses on a mixture of hydrogen atoms and molecules and is devoted to the study of the phenomenon of pressure dissociation at finite temperatures. The equation of state and dissociation degree have been calculated from the free energy functions in the range of temperature 2000-10,000K and density 0.02-1.0g/cm^3, which can be compared with other approaches and experiments. The pressure dissociation is found to occur in higher density range, while temperature dissociation is a more gradual effect.

Influence of pore water pressure on upper bound analysis of collapse shape for square tunnel in Hoek-Brown media

To investigate the effective shape of collapsing block in square tunnel subjected to pore water pressure,the analytical solution of detaching curve was derived using upper bound theorem of limit analysis with Hoek-Brown failure criterion. The work rate of pore water pressure,which was regarded as an external rate of work,was taken into account in the framework of limit analysis. Taking advantages of variational calculation,the objective function with respect to detaching curve was optimized to obtain the effective shape of collapsing block for square tunnel. According to the numerical results,it is found that the varying pore water pressure coefficient only affects the height and width of the collapsing block,whereas the shape of collapsing block remains unchanged.

Arterial Pulse Pressure Variation versus Central Venous Pressure as a Predictor for Fluid Responsiveness during Open Major Abdominal Operations

Introduction: Fluid resuscitation is the cornerstone in the management of hemodynamically unstable patients. Dynamic parameters of fluid responsiveness, like pulse pressure variation, have the advantage of being more reliable index for fluid management. Objective: The aim of our study was to compare between arterial pulse pressure variation (PPV) versus central venous pressure (CVP) as a predictor for fluid responsiveness during major open abdominal operations. Patients and Methods: 60 adult patients under general anesthesia with mechanical ventilation underwent open major abdominal surgical procedures were included in our prospective randomized controlled study. Intravenous fluid was infused and monitored by CVP in control group or by PPV in the other group. Hemodynamic variables (heart rate, invasive blood pressure, PPV and CVP) were measured at baseline after anesthesia induction and every 10 min, during first hour of operation, and then every 15 min, till end of surgery. Blood loss and total i.v. fluid & blood transfusion given to patients were recorded and compared between two groups intraoperatively. Results: Patients in the PPV group required more intraoperative fluid and blood transfusion than patients in CVP group to achieve more stable hemodynamic parameters. The fall in blood pressure (>20% of baseline) and increase in heart rate are more common in CVP group (p Conclusion: PPV is a better predictor and a good guide for fluid responsiveness. More stable hemodynamic variables are observed in PPV group.

Variational assimilation in combination with a regularization method for sea level pressure retrieval from QuikSCAT scatterometer data Ⅱ:simulation experiment and actual case study

The sea level pressure field can be computed from sea surface winds retrieved from satellite microwave scatterometer measurements, based on variational assimilation in combination with a regularization method given in part I of this paper. First, the validity of the new method is proved with a simulation experiment. Then, a new processing procedure for the sea level pressure retrieval is built by combining the geostrophic wind, which is computed from the scatterometer 10-meter wind using the University of Washington planetary boundary layer model using this method. Finally, the feasibility of the method is proved using an actual case study.

Variational assimilation in combination with the regularization method for sea level pressure retrieval from QuikSCAT scatterometer data I:Theoretical frame construction

A new method of constructing a sea level pressure field from satellite microwave scatterometer measurements is presented. It is based on variational assimilation in combination with a regularization method using geostrophic vorticity to construct a sea level pressure field from scatterometer data that are given in this paper, which offers a new idea for the application of scatterometer measurements. Firstly, the geostrophic vorticity from the scatterometer data is computed to construct the observation field, and the vorticity field in an area and the sea level pressure on the borders are assimilated. Secondly, the gradient of sea level pressure （semi-norm） is used as the stable functional to educe the adjoint system, the adjoint boundary condition and the gradient of the cost functional in which a weight parameter is introduced for the harmony of the system and the Tikhonov regularization techniques in inverse problem are used to overcome the ill-posedness of the assimilation. Finally, the iteration method of the sea level pressure field is developed.

Volkmar Klien的混合类电子音乐创作技法研究——以作品《variations in air pressure》为例

文章以学习中对电子音乐的认识与了解,着重以混合类电子音乐为基础展开研究。"混合类"电子音乐是完全不同于"纯"电子音乐的一种电子音乐形态。其产生的最初目的是作曲家为了丰富釆样内容,不拘泥于某一类音色范畴,进而在理念与技术层面突破了"具体音乐"与"电子合成音乐"间的界限,将环境声音、人声或声学器乐等未经电子化处理的声音素材直接用于电子音乐作品中,形成异质声音元素并存的新状态。此篇论文是以volkmar klien创作的一首小提琴与电子音乐结合的混合型电子音乐作品《variations in air pressure》为例,浅析混合类电子音乐中的创作技法研究。

Predicting the Two-Phase Liquid-Solid Drag Model Using the Calculus of Variation

The simplified momentum equations of the two-phase flow have been adopted as the basic assumptions in this study. For vessels of small diameter, the shear stress becomes important and the friction pressure drop proposed by Ergun considers this effect by involving the wall effect. By replacing the Ergun pressure drop and the first order velocity term for particles drag model in the momentum equations, the relation for the drag coefficient versus the volume fraction is obtained. The calculus of variations is used with certain restriction for extremization of this drag coefficient. An analytical correlation for the drag coefficient is obtained depending on the volume fraction of “fluid particles”. The drag function obtained in previous studies does not match with the empirical data in the bed volume fraction range of [0.45 to 0.59]. Therefore, the function is modified and the results are better adjusted with the empirical data.

General variational solution for seismic and static active earth pressure on rigid walls considering soil tensile strength cut-off

According to the limit equilibrium state of soils behind rigid walls and the pseudo-static approach,a general closed-form solution to seismic and static active earth pressure on the walls,which considers shear and tension failure of the retained soil,is put forward using a variational calculus method.The application point of the active resultant force specified in the proposed method is explained with a clear physical meaning related to possible movement modes of the walls.In respect of the derived nine dependent equations reflecting the functional characteristics of the earth pressure,the proposed method can be performed easily via an implicit strategy.There are 13 basic factors related to the retained soils,walls,and external loads to be involved in the proposed method.The tension crack segment of the slip surface is obviously influenced by these parameters,apart from vertical seismic coefficient and geometric bounds of the surcharge,but the shear slip segment maintains an approximately planar shape almost uninfluenced by these parameters.Noticeably,the proposed method quantitatively reflects that the resultant of the active earth pressure is always within a limited range under different possible movements of the same wall.

Variational principle and zero temperature limits of asymptotically （sub）-additive projection pressure

Let {Si}li=l be an iterated function system （IFS） on Rd with an attractor K. Let （S,cr） denote the one-sided full shift over the finite alphabet {1,2,...,l}, and let π：∑ -K be the coding map. Given an asymptotically （sub）-additive sequence of continuous functions{Si}n≥1, we define the asymptotically additive projection pressure Pπ and show the variational principle for Pπunder certain affine IFS. We also obtain variational principle for the asymptotically sub-additive projection pressure if the IFS satisfies asymptotically weak separation condition （AWSC）. Furthermore, when the IFS satisfies AWSC, we investigate the zero temperature limits of the asymptotically sub-additive projection pressure Pπ（β） with positive parameter β.