Logistic Regression Analysis and Nursing Interventions for High-risk Factors for Pressure Sores in Patients in a Surgical Intensive Care Unit

Objective： To investigate the risk factors related to the development of pressure sores in critically ill surgical patients and to establish a basis for the formulation of effective precautions. Methods： A questionnaire regarding the factors for pressure sores in critically ill surgical patients was created using a case control study with reference to the pertinent literature. After being exam- ined and validated by experts, the questionnaire was used to collect data about critically ill surgical patients in a grade A tertiary hospital. Among the 47 patients enrolled into the study, the 14 who developed nosocomial pressure sores were allocated to the pressure sore group, and the remaining 33 patients who met the inclusion criteria and did not exhibit pressure sores were allocated to the control group. Univariate and multivariate logistic regression analyses were employed to examine the differences in 22 indicators between the two groups in an attempt to identify the risk factors for pressure sores. Results： According to the univariate analyses, the maximum value of lactic acid in the arterial blood, the number of days of norepinephrine use, the number of days of mechanical ventilation, the number of days of blood purification, and the number of days of bowel incontinence were statistically greater in the pressure sore group than in the control group （P〈0.05）. The multivariate logistic regression analysis revealed that the number of days of norepinephrine use and the level of lactic acid in the arterial blood were high risk-factors for pressure sores （P〈0.05）. Conclusions： The best method for preventing and control pressure sores in surgical critically ill patients is to strongly emphasize the duration of the critical status and to give special attention to patients in a continuous state of shock. The adoption of measures specific to high-risk patient groups and risk factors, including the active control of primary diseases and the application of decompression measures during the treatment of the patients, are helpful for improving the quality of care in the prevention and control of pressure sores in critically ill patients.

An Experimental Study on the Wave-Induced Pore Water Pressure Change and Relative Influencing Factors in the Silty Seabed

In this study, a flume experiment was designed to investigate the characteristics of wave-induced pore water pressure in the soil of a silty seabed with different clay contents, soil layer buried depths and wave heights respectively. The study showed that water waves propagating over silty seabed can induce significant change of pore water pressure, and the amplitude of pore pressure depends on depth of buried soil layer, clay content and wave height, which are considered as the three influencing factors for pore water pressure change. The pressure will attenuate according to exponential law with increase of soil layer buried depth, and the attenuation being more rapid in those soil layers with higher clay content and greater wave height. The pore pressure in silty seabed increases rapidly in the initial stage of wave action, then decreases gradually to a stable value, depending on the depth of buried soil layer, clay content and wave height. The peak value of pore pressure will increase if clay content or depth of buried soil layer decreases, or wave height increases. The analysis indicated that these soils with 5% clay content and waves with higher wave height produce instability in bed easier, and that the wave energy is mostly dissipated near the surface of soils and 5% clay content in soils can prevent pore pressure from dissipating immediately.

Risk factors of infected pancreatic necrosis secondary to severe acute pancreatitis

BACKGROUND： Severe acute pancreatitis（SAP） remains a clinical challenge with considerable morbidity and mortality.An early identification of infected pancreatic necrosis（IPN）, a life-threatening evolution secondary to SAP, is obliged for a more preferable prognosis. Thus, the present study was conducted to identify the risk factors of IPN secondary to SAP. METHODS： The clinical data of patients with SAP were retrospectively analyzed. Univariate and multivariate logistic regression analyses were sequentially performed to assess the associations between the variables and the development of IPN secondary to SAP. A receiver operating characteristic（ROC） curve was created for each of the qualified independent risk factors. RESULTS： Of the 115 eligible patients, 39（33.9%） progressed to IPN, and the overall in-hospital mortality was 11.3%（13/115）.The early enteral nutrition（EEN）（P=0.0092, OR=0.264）, maximum intra-abdominal pressure（IAP）（P=0.0398, OR=1.131）and maximum D-dimer level（P=0.0001, OR=1.006） in the first three consecutive days were independent risk factors associated with IPN secondary to SAP. The area under ROC curve（AUC） was 0.774 for the maximum D-dimer level in the first three consecutive days and the sensitivity was 90% and the specificity was 58% at a cut-off value of 933.5 μg/L; the AUC was 0.831 for the maximum IAP in the first three consecutive days and the sensitivity was 95% and specificity was 58%at a cut-off value of 13.5 mm Hg. CONCLUSIONS： The present study suggested that the maximum D-dimer level and/or maximum IAP in the first three consecutive days after admission were risk factors of IPN secondary to SAP; an EEN might be helpful to prevent the progression of IPN secondary to SAP.

Crack propagation mechanism of compression-shear rock under static-dynamic loading and seepage water pressure

To reveal the water inrush mechanics of underground deep rock mass subjected to dynamic disturbance such as blasting, compression-shear rock crack initiation rule and the evolution of crack tip stress intensity factor are analyzed under static-dynamic loading and seepage water pressure on the basis of theoretical deduction and experimental research. It is shown that the major influence factors of the crack tip stress intensity factor are seepage pressure, dynamic load, static stress and crack angle. The existence of seepage water pressure aggravates propagation of branch cracks. With the seepage pressure increasing, the branch crack experiences unstable extension from stable propagation. The dynamic load in the direction of maximum main stress increases type I crack tip stress intensity factor and its influence on type II crack intensity factor is related with crack angle and material property. Crack initiation angle changes with the dynamic load. The initial crack initiation angle of type I dynamic crack fracture is 70.5°. The compression-shear crack initial strength is related to seepage pressure, confining pressure, and dynamic load. Experimental results verify that the initial crack strength increases with the confining pressure increasing, and decreases with the seepage pressure increasing.

Theoretical and numerical studies of crack initiation and propagation in rock masses under freezing pressure and far-field stress

Water-bearing rocks exposed to freezing temperature can be subjected to freezeethaw cycles leading tocrack initiation and propagation, which are the main causes of frost damage to rocks. Based on theGriffith theory of brittle fracture mechanics, the crack initiation criterion, propagation direction, andcrack length under freezing pressure and far-field stress are analyzed. Furthermore, a calculation methodis proposed for the stress intensity factor （SIF） of the crack tip under non-uniformly distributed freezingpressure. The formulae for the crack/fracture propagation direction and length of the wing crack underfreezing pressure are obtained, and the mechanism for coalescence of adjacent cracks is investigated.In addition, the necessary conditions for different coalescence modes of cracks are studied. Using thetopology theory, a new algorithm for frost crack propagation is proposed, which has the capability todefine the crack growth path and identify and update the cracked elements. A model that incorporatesmultiple cracks is built by ANSYS and then imported into FLAC3D. The SIFs are then calculated using aFISH procedure, and the growth path of the freezing cracks after several calculation steps is demonstratedusing the new algorithm. The proposed method can be applied to rocks containing fillings such asdetritus and slurry. 2014 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Production and hosting byElsevier B.V. All rights reserved.

Blood pressure differences in people with various individual characteristics in Guangdong Province

Objective To study the differences in blood pressure (BP) levels and the main factors raising BP among the population in Guangdong Province. Methods The data analyzed stem from the sampling survey of hypertension in Guangdong Province in 1991, covering 42, 894 subjects over 15 years old. Individual characteristics included age, sex, occupation, education, smoking, alcohol drinking and body mass index (BMI) . Results Systolic and diastolic BP increased with age. The hypertension prevalence rate in male is higher than in female. The age - adjusted prevalence rate in office personnel is the highest (12.9 % ) among all occupations. It was increased with education level and BMI (in people educated at university and over is 13. 1 % ), and higher in smokers and alcohol-drinkers than non-smokers and non -alcohol-drinkers. Conclusions Age, occupation, education, smoking, alcohol drinking and BMI all effect BP. These risk factors should be reduced in the Guangdong population.

Water slip flow in superhydrophobic microtubes within laminar flow region

The fabrication of superhydrophobic surfaces and the studies on water flow characteristics therein are of great significance to many industrial areas as well as to science and technology development. Experiments were car- ried out to investigate slip characteristics of water flowing in circular superhydrophobic microtubes within lam- inar flow region. The superhydrophobic microtubes of stainless steel were fabricated with chemical etching- fluorination treatment. An experimental setup was designed to measure the pressure drop as function of water flow rate. For comparison, superhydrophilic tubes were also tested. Poiseuille number Po was found to be smaller for the superhydrophobic microtubes than that for superhydrophilic ones. The pressure drop reduc- tion ranges from 8% to 31%. It decreases with increasing Reynolds number when Re 〈 900, owing to the transition from Cassie state to Wenze] state. However, it is almost unchanged with further increasing Re after Re 〉 900. The slip length in superhydrophobic microtubes also exhibits a Reynolds number dependence similarly to the pressure drop reduction. The relation between slip length and Darcy friction factor is theoretically analyzed with consideration of surface roughness effect, which was testified with the experimental results.

Interaction analysis of back-to-back mechanically stabilized earth walls

Back-to-back mechanically stabilized earth walls （BBMSEWs） are encountered in bridge approaches, ramp ways, rockfall protection systems, earth dams, levees and noise barriers. However, available design guidelines for BBMSEWs are limited and not applicable to numerical modeling when back-to-back walls interact with each other. The objective of this paper is to investigate, using PLAXIS code, the effects of the reduction in the distance between BBMSEW, the reinforcement length, the quality of backfill material and the connection of reinforcements in the middle, when the back-to-back walls are close. The results indicate that each of the BBMSEWs behaves independently if the width of the embankment between mechanically stabilized earth walls is greater than that of the active zone. This is in good agreement with the result of FHWA design guideline. However, the results show that the FHWA design guideline underestimates the lateral earth pressure when back-to-back walls interact with each other. Moreover, for closer BBMSEWs, FHWA design guideline strongly overestimates the maximum tensile force in the reinforcement. The investigation of the quality of backfill material shows that the minor increase in embankment cohesion can lead to significant reductions in both the lateral earth pressure and the maximum tensile force in geosynthetic. When the distance between the two earth walls is close to zero, the connection of reinforcement between back-to-back walls significantly improves the factor of safety.

ERRATUM TO “CHARACTERISTICS OF PRESSURE DROP AND CORRELATION OF FRICTION FACTORS FOR SINGLE-PHASE FLOW IN ROLLING HORIZONTAL PIPE”

This is the erratum to the article [zhang Jin-hong, Yan Chang-qi, Gao Pu-zhen, Journal of Hydrodynamics, 2009, 21(5)]. The Fig.5 is corrected.

Analysis of Rolling Pressure in Asymmetrical Rolling Process by Slab Method

The plane strain asymmetrical rolling was analyzed using slab method. The contact arc was replaced by parabola, and the constant surface friction status was adopted during the analysis. The deformation area was divided into three zones according to the direction of the friction. Then, the three zones were studied, respectively. A rolling force model and a rolling torque model were developed based on the analysis, and they were used to analyze the influ- ence of asymmetrical rolling factors on deformation area and unit pressure if they had good precision which was determined by comparing the calculated results with the measured ones.

Investigation of the characteristics of particulate flows through fibrous filters using the lattice Boltzmann method

A fibrous filter is one of the most common systems used to separate suspended particles from air. Two important factors （i,e,, the pressure drop and capture efficiency） are usually used to evaluate the performance of this type of filter, This study considers three two-dimensional arrangements of fibers （parallel, staggered, and random） to geometrically model fibrous media, The lattice Boltzmann method is employed to numerically simulate fluid flow through the filter, The Lagrangian form of the equation of motion of a particle is numerically solved to track the path of each particle in the flow field, where a one-way interaction between the fluid and particles is considered. The effects of pertinent parameters such as the fiber arrangement, solid volume fraction, particle-to-fiber diameter ratio, particle-to-fluid density ratio, Reynolds number, Stokes number, and size of the fibrous medium on the pressure drop and capture efficiency are studied. The obtained results are compared with existing empirical and theoretical findings and discussed.

Numerical investigation on jet interaction with a compression ramp

A numerical investigation on jet interaction in supersonic laminar flow with a compres- sion ramp is performed utilizing the AUSMDV scheme and a parallel solver. Several parameters dominating the interference flowfield are studied after defining the relative increment of normal force and the jet amplification factor as the evaluation criterion of jet control performance. The computational results show that most features of the interaction flowfield between the transverse jet and the ramp are similar to those between a jet and a flat plate, except that the flow structures are more complicated and the low-pressure region behind the jet is less extensive. The relative force increment and the jet amplification factor both increase with the distance between the jet and the ramp shortening till quintuple jet diameters. Inconspicuous difference is observed between the jet-before-ramp and jet-on-ramp cases. The variation of the injection angle changes the extent of the separation region, the plateau pressure, and the peak pressure near the jet. In the present computational conditions, 120 is indicated relatively optimal among all the injection angles studied. For cold gas simulations, although little influence of the jet temperature on the pressure distribution near the jet is observed under the computation model and the flow parameters studied, reducing jet temperature somehow benefits the improvement of the normal force and the jet efficiency. When the pressure ratio of jet to freestream is fixed, the relative force increment varies little when increasing the freestream Mach number, while the jet amplification factor increases.