1,390 research outputs found
In situ growth of CuO on porous geopolymer spheres as green catalysts for enhanced peroxymonosulfate-activated degradation of Orange I
No full textIn this study, in situ growth of CuO on the surface of porous geopolymer catalyst spheres (GC) was prepared through a simple method for the activation of peroxymonosulfate (PMS) to degrade Orange I (OI) in water. GC-0.01 exhibited an excellent performance with more than 95% degradation of OI within 30 min. The effects of PMS concentrations, catalyst dosage, Cl−, HCO3−, and humic acid (HA) on OI degradation in the GC-0.01/PMS system were systematically investigated. The study of the mechanism showed that PMS combined with the catalyst to generate complexes on the surface of the spheres, which could degrade OI through an electron transfer pathway. In addition, a variety of reactive oxygen species, mainly 1O2, were also present in the GC-0.01/PMS system, which could also degrade OI. This work provides new insight into the application of oxide-modified geopolymers in the activation of PMS for water purification applications
Joint relay and jammer selection improves the physical layer security in the face of CSI feedback delays
No full textWe enhance the physical-layer security (PLS) of amplify-and-forward relaying networks with the aid of joint relay and jammer selection (JRJS), despite the deliterious effect of channel state information (CSI) feedback delays. Furthermore, we conceive a new outage-based characterization approach for the JRJS scheme. The traditional best relay selection (TBRS) is also considered as a benchmark. We first derive closed-form expressions of both the connection outage probability (COP) and of the secrecy outage probability (SOP) for both the TBRS and JRJS schemes. Then, a reliable-and-secure connection probability (RSCP) is defined and analyzed for characterizing the effect of the correlation between the COP and SOP introduced by the corporate source-relay link. The reliability-security ratio (RSR) is introduced for characterizing the relationship between the reliability and security through the asymptotic analysis. Moreover, the concept of effective secrecy throughput is defined as the product of the secrecy rate and of the RSCP for the sake of characterizing the overall efficiency of the system, as determined by the transmit SNR, secrecy codeword rate and the power sharing ratio between the relay and jammer. The impact of the direct source-eavesdropper link and additional performance comparisons with respect to other related selection schemes are further included. Our numerical results show that the JRJS scheme outperforms the TBRS method both in terms of the RSCP as well as in terms of its effective secrecy throughput, but it is more sensitive to the feedback delays. Increasing the transmit SNR will not always improve the overall throughput. Moreover, the RSR results demonstrate that upon reducing the CSI feedback delays, the reliability improves more substantially than the security degrades, implying an overall improvement in terms of the security-reliability tradeoff. Additionally, the secrecy throughput loss due to the second hop feedback delay is more pronounced th- n that of the first hop
Low-PAPR layered/enhanced ACO-SCFDM for optical-wireless communications
No full textIn this letter, we propose layered/enhanced asymmetrically clipped optical single-carrier frequency-division multiplexing (L/E-ACO-SCFDM) for optical-wireless communications. L/E-ACO-SCFDMhas a lower computational complexity and peak-to-average power ratio (PAPR) than L/E-ACO orthogonal frequency-division multiplexing (L/E-ACO-OFDM). The computational complexity of the simplified transmitter in L/EACO-SCFDM with R layers is (2 - 2/2R)O(N), which is lower than the computational complexity of (2 - 2/2R)O(Nlog2N) in L/E-ACO-OFDM. At a complementary cumulative distribution function of 10-3, the PAPR of L/E-ACO-SCFDM is approximately 4.2, 3.4, and 2.7 dB lower than that of L/E-ACO-OFDM for 2, 3, and 4 layers, respectively. The simulation results indicate that L/E-ACO-SCFDM has better performance than L/E-ACOOFDM under the transmitter nonlinearity and multipath fading.</p
An efficient implementation of transonic aeroelastic tailoring based on a reduced-order model using structural dynamic reanalysis method
No full textDue to fuel efficiency, advanced aerodynamic and structural concern, more and more composite materials used in aircraft desgin. In composite structure aeroelastic tailoring process, an accurate and efficient method to evaluate the aeroelastic stability is very required. The traditional CFD-based POD/ROM has been shown its accuracy and efficiency for transonic aeroelastic analysis at fixed system. In aeroelastic tailoring process, in order to meet the requirements of aeroelastic performance, the parameters of the composite structure need to be modified repeatedly and the aerodynamic model have to be reconstructed. However, these reconstruction procedures take a considerable time, and greatly increasing the time cost of the aircraft design. To develop a more efficient composite structure aeroelastic tailoring method, starting with improving the efficiency of aeroelastic performance evaluation, this paper propose an approximate aeroelastic characteristics evaluation method based CFD-based POD/ROM by introducing the structural dynamic reanalysis method. The improved AGARD 445.6 composite wing was employed to verify the accuracy and efficiency of the proposed method. The results show that the proposed evaluation method can not only accurately predict the aeroelastic response of the structure, but also greatly improving the efficiency of transonic composite structure aeroelastic tailoring.</p
Variables influencing radiological fracture healing in children with femoral neck fractures treated surgically: A review of 177 cases
No full textPurpose: This study aimed: (1) to determine the probability of and the amount of time needed to achieve fracture healing in children with displaced femoral neck fractures (FNFs) treated surgically; and (2) to determine which factors can affect both the probability of and the amount of time needed to achieve radiological fracture healing in those patients. Hypothesis: Pediatric FNFs require longer time to achieve union than previously reported. Methods: We retrospectively reviewed the data of 177 children (mean age 10.5 ± 3.9 years) with FNFs treated surgically. Risk factors, including age, sex, laterality, the mechanism of injury, the initial displacement severity, the type of fracture, the time to reduction, the reduction method, the fixation method and the reduction quality, were recorded. Furthermore, the presence of a comminuted medial or posterior cortex on anteroposterior (AP) or lateral radiographs was also recorded. Results: A total of 172 hips (97.2%) achieved radiological fracture healing during the follow-up period. Severe initial displacement, a comminuted cortex on the AP or lateral radiographs and poor reduction quality significantly increased the time needed to achieve radiological fracture healing (p < 0.05). Cox regression analysis indicated that the cumulative probability of achieving fracture healing increased linearly during the first 6 months and then plateaued, with a monthly increase of less than 5%. The severity of initial displacement, presence/absence of comminution on the medial or posterior cortex, and reduction quality were factors influencing the probability of achieving fracture healing within the first 6 months after injury (p < 0.05). Conclusions: Radiological union of displaced pediatric FNFs treated surgically increases linearly during the first six month after surgery and then it tends to plateau. Risk factors for nonunion are severe initial displacement, poor reduction quality and the presence of comminuted medial or posterior cortex on AP or lateral radiographs; the same factors are associated with a longer time to achieve fracture healing. Level of evidence: III
The Duration of Hardware Retention After Radiologic Union of Surgically Treated Femoral Neck Fractures in Children May Predict the Aggravation or Occurrence of Avascular Necrosis of the Femoral Head or Neck After Hardware Removal
No full textBackground: The incidence of aggravation or occurrence of avascular necrosis (AVN) following hardware removal in surgically treated pediatric femoral neck fractures who achieved radiologic consolidation is unknown. This study aimed to investigate the risk factors for this complication.
Methods: Seventy-one pediatric (mean age: 9.8± 3.9 y) were retrospectively analyzed. Risk factors (age, sex, laterality, severity of initial displacement, type of fracture, time from trauma to reduction, reduction and fixation method, quality of reduction, time required to achieve radiologic union, duration of hardware retention, presence of AVN before hardware removal and follow-up time) were recorded. The severity of AVN was
assessed based on radiographs with Ratliff’s classification.
Results: Following hardware removal, the aggravation/occurrence of AVN was detected in 11 hips (15.5%). Among the 5 hips (7%) with aggravation of AVN, 1 (1.4%) with type II AVN and 3 (4.2%) with type III AVN exhibited aggravation of type I AVN, while the remaining hip (1.4%; type I) showed enlargement of the involved AVN area. Six hips (8.5%) developed AVN following hardware removal: 2 (2.8%) were classified as type I and 4 (5.6%) as type III. Receiver operating characteristic curve analysis indicated that hardware retention >7 months after union is associated with a decreased rate of aggravation or occurrence of AVN of the femoral neck or head following hardware removal.
Conclusions: The incidence of aggravation or occurrence of AVN following hardware removal in surgically treated pediatric femoral neck fractures is 15.5%; hardware retention > 7 months after radiologic union may reduce the risk of aggravation or occurrence of AVN of the femoral neck or head postimplant removal.
Level of evidence: Level III.Background: The incidence of aggravation or occurrence of avascular necrosis (AVN) following hardware removal in surgically treated pediatric femoral neck fractures who achieved radiologic consolidation is unknown. This study aimed to investigate the risk factors for this complication. Methods: Seventy-one pediatric (mean age: 9.8± 3.9 y) were retrospectively analyzed. Risk factors (age, sex, laterality, severity of initial displacement, type of fracture, time from trauma to reduction, reduction and fixation method, quality of reduction, time required to achieve radiologic union, duration of hardware retention, presence of AVN before hardware removal and follow-up time) were recorded. The severity of AVN was assessed based on radiographs with Ratliff’s classification. Results: Following hardware removal, the aggravation/occurrence of AVN was detected in 11 hips (15.5%). Among the 5 hips (7%) with aggravation of AVN, 1 (1.4%) with type II AVN and 3 (4.2%) with type III AVN exhibited aggravation of type I AVN, while the remaining hip (1.4%; type I) showed enlargement of the involved AVN area. Six hips (8.5%) developed AVN following hardware removal: 2 (2.8%) were classified as type I and 4 (5.6%) as type III. Receiver operating characteristic curve analysis indicated that hardware retention >7 months after union is associated with a decreased rate of aggravation or occurrence of AVN of the femoral neck or head following hardware removal. Conclusions: The incidence of aggravation or occurrence of AVN following hardware removal in surgically treated pediatric femoral neck fractures is 15.5%; hardware retention > 7 months after radiologic union may reduce the risk of aggravation or occurrence of AVN of the femoral neck or head postimplant removal. Level of evidence: Level III
Peer Effects and Voluntary Green Building Certification
No full textabstract: Empirical evidence is provided to show that peer effects have statistically significant and positive impacts on the diffusion of green building certificates. Application and approval records of green certificates by commercial buildings in NY and AZ are used. The challenge of self-selection is addressed by the usage of fixed effects and the challenge of reflection is addressed by the time lag delay between a building’s application and its approval. Empirical results show that an additional approved LEED certificate within a zip code will increase the probability of a commercial building in the same zip code to apply for a LEED certificate by 3–4 percentage points; an additional approved Energy Star certificate within a zip code will increase the probability of a commercial building in the same zip code to apply for an Energy Star certificate by 1–2 percentage points
Effect of the Number, Size, and Location of Cannulated Screws on the Incidence of Avascular Necrosis of the Femoral Head in Pediatric Femoral Neck Fractures: A Review of 153 Cases
No full textBackground: The correlation between the number, size, and location of cannulated screws and the incidence of avascular necrosis (AVN) in children with femoral neck fractures treated surgically is uncertain. Methods: We retrospectively reviewed 153 children (mean age: 10.6±3.7 y) with femoral neck fractures treated by internal fixation with 2 (n=112) or 3 (n=41) cannulated screws. The severity of initial displacement was divided into incomplete (type I) and complete (type II, angulation <50 degrees; type III, angulation >50 degrees) fractures. The diameter of the screw was measured and recorded as a percentage of the femoral neck width. The distance (D) between the mid-point of each screw at the base (B) of the femoral neck and at the tip (T) of each screw and the superior and anterior cortices of the femoral neck, respectively, were measured on anteroposterior (AP) and lateral (L) radiographs. Values were expressed as the ratio between the measured distance and the width of the femoral neck (BDAP%, TDAP%, BDL%, and TDL%). The correlation between the number, size, and location of the screws and AVN was analyzed. Results: Patients with type II of initial displacement treated with 2 cannulated screws had a lower AVN rate (21.4%) than those treated with 3 screws (44.8%) (P=0.027). Screw diameter (19%) in patients with AVN was larger than (17%) in patients without AVN (P<0.001); patients with AVN had a lower BDAP% (48.6%) than those without AVN (56.4%) (P<0.001). Screw size and BDAP% were risk factors for AVN (P<0.05). Further, screw diameter >16.5% and BDAP% <51.6% of the femoral neck width were the cutoff values for an increased AVN rate (P<0.05). Conclusions: Patients treated with 2 cannulated screws showed a lower rate of AVN than patients treated with 3 screws. Screws of larger size and screws closer to the piriformis fossa on AP radiographs increased the risk of AVN in children with femoral neck fractures treated surgically. Level of Evidence: Level III
Risk factors for proximal radial abnormalities in children with untreated chronic Monteggia fractures: a review of 142 cases
No full textAbstract
Background The risk factors for proximal radial abnormalities (PRA) in paediatric patients with untreated chronic Monteggia fractures (CMFs) are unclear. This multicentre study aimed to evaluate the risk factors for PRA in children with untreated CMFs.
Materials and methods The clinical data of 142 patients (mean age at the time of injury: 5.73 years) with untreated unilateral CMFs were retrospectively reviewed. The radial neck-shaft angle (RNSAP) and radial head size (RHL) were measured on anteroposterior (AP) and lateral (L) radiographs, respectively. The RHL size was the ratio of the widest
width of the proximal radial metaphysis to the narrowest radial neck width. The En-RNSAP and En-RHL were the ratios of the enlargement (En) of the RNSAP angle and RHL
size of the injured elbow to those of the uninjured elbow, respectively. Paired-sample t-tests, single-factor analyses and multiple linear regression analyses were performed to evaluate the correlation between the differences in these parameters between the injured and uninjured elbows and the assessed risk factors. These risk factors included institution, sex, laterality, age at injury, time from injury to diagnosis, direction of RH dislocation, distance of RH dislocation (DD-RH), presence of radial or median nerve injury, heterotopic ossification and immobilization of the elbow after injury.
Results In children with untreated CMFs (mean time from injury to diagnosis: 14.6 months), Student’s t-test revealed a significant difference in the RHL size (P < 0.001) but not in the RNSAP angle (P = 0.075) between the injured and uninjured elbows. Pearson correlation analysis revealed a potential correlation between En-RHL and age at the time
of injury (P = 0.069), time from injury to diagnosis (P < 0.001) and DD-RH (P < 0.001), excluding other risk factors (P > 0.05). Multiple linear regression analysis revealed that age at the time of injury (P = 0.047), time from injury to diagnosis (P = 0.007) and DD-RH (P = 0.001) were risk factors for an increased En-RHL in patients with untreated CMFs; the variability in En-RHL among the other three risk factors was 21.4%.
Conclusions In paediatric patiens with unilateral untreated CMFs, PRA of the injured elbow consisted mainly of RH enlargement or radial neck narrowing rather than valgus deformities of the proximal radius. Older age at injury, increased time from injury to diagnosis and DD-RH were risk factors for more severe PRA.
Level of evidence III.Abstract
Background The risk factors for proximal radial abnormalities (PRA) in paediatric patients with untreated chronic Monteggia fractures (CMFs) are unclear. This multicentre study aimed to evaluate the risk factors for PRA in children with untreated CMFs.
Materials and methods The clinical data of 142 patients (mean age at the time of injury: 5.73 years) with untreated unilateral CMFs were retrospectively reviewed. The radial neck-shaft angle (RNSAP) and radial head size (RHL) were measured on anteroposterior (AP) and lateral (L) radiographs, respectively. The RHL size was the ratio of the widest width of the proximal radial metaphysis to the narrowest radial neck width. The En-RNSAP and En-RHL were the ratios of the enlargement (En) of the RNSAP
angle and RHL size of the injured elbow to those of the uninjured elbow,
respectively. Paired-sample t-tests, single-factor analyses and multiple linear regression analyses were performed to evaluate the correlation between the differences in these parameters between the injured and uninjured elbows and the assessed risk factors. These risk factors included institution, sex, laterality, age at injury, time from injury to diagnosis, direction of RH dislocation, distance of RH dislocation (DD-RH), presence of radial or median nerve injury, heterotopic ossification and immobilization of the elbow after injury.
Results In children with untreated CMFs (mean time from injury to diagnosis: 14.6 months), Student’s t-test revealed a significant difference in the RHL size (P < 0.001) but not in the RNSAP angle (P = 0.075) between the injured and uninjured elbows. Pearson correlation analysis revealed a potential correlation between En-RHL and age at the time of injury (P = 0.069), time from injury to diagnosis (P < 0.001) and DD-RH (P < 0.001), excluding other risk factors (P > 0.05). Multiple linear regression analysis revealed that age at the time of injury (P = 0.047), time from injury to diagnosis (P = 0.007) and DD-RH (P = 0.001) were risk factors for an increased En-RHL in patients with untreated CMFs; the variability in En-RHL among the other three risk factors was 21.4%
Is there an alternative to the Delbet-Colonna classification? Introduction and reliability assessment of a new classification system for paediatric femoral neck fractures: preliminary results
No full textAbstract
Purpose The purpose of this study was to introduce a new classification system for pediatric femoral neck fractures (PFNFs) and to evaluate its reliability.
Methods Two hundred and eight unilateral PFNFs (mean patient age: 9.0 ± 4.8 years) were included. Based on preoperative radiographs, the new classification system distinguished PFNFs without anterior or posterior translation (Type I), PFNFs with anterior (Type II) or posterior (Type III) translation, PFNFs with a comminuted medial or posterior column (Type IV), and subtrochanteric femoral fractures (SFFs; Type V). Radiographs were evaluated twice with an interval of two weeks by 19 raters with different specialties, experiences and geographical origins. The results were compared with a selection of 50 patient age-matched unilateral PFNFs and SFFs (mean patient age: 9.1 ± 4.9 years). These were graded twice by the same graders according to the Delbet-Colonna (D-C) classification.
Results Four radiologists and 15 pediatric orthopedic surgeons from Europe and Asia graded the radiographs. Fair agreement was found between radiologists (κ = 0.296 ± 0.01) and surgeons (κ = 0.3 ± 0.005) (P = 0.17), although more experienced surgeons performed better than less experienced ones; a similar fair assessment was found for raters from Europe (κ = 0.309 ± 0.021) and Asia (κ = 0.3 ± 0.006) and for type II, III and IV fractures; the κ value in the first evaluation (0.309) was similar to that in the second evaluation (0.298). The overall κ value of the D-C classification subtypes was significantly higher (0.599 ± 0.217) than that of the new classification, 0.326 ± 0.162 (t = 3.190 P = 0.005).
Conclusions The new classification system showed fair reliability relative to the D-C classification. The reliability of the new classification system was not affected by the specialty or geographic origin of the rater or the evaluation round, only by rater experience level. The concordance was worse for PFNFs with anterior or posterior translation or with a comminuted medial or posterior columns.Purpose: The purpose of this study was to introduce a new classification system for paediatric femoral neck fractures (PFNFs) and to evaluate its reliability. Methods: Two hundred and eight unilateral PFNFs (mean patient age: 9.0 ± 4.8 years) were included. Based on preoperative radiographs, the new classification system distinguished PFNFs without anterior or posterior translation (Type I), PFNFs with anterior (Type II) or posterior (Type III) translation, PFNFs with a comminuted medial or posterior column (Type IV), and subtrochanteric femoral fractures (SFFs; Type V). Radiographs were evaluated twice with an interval of two weeks by 19 raters with different specialties, experiences and geographical origins. The results were compared with a selection of 50 patient age-matched unilateral PFNFs and SFFs (mean patient age: 9.1 ± 4.9 years). These were graded twice by the same graders according to the Delbet-Colonna (D-C) classification. Results: Four radiologists and 15 paediatric orthopaedic surgeons from Europe and Asia graded the radiographs. Fair agreement was found between radiologists (κ = 0.296 ± 0.01) and surgeons (κ = 0.3 ± 0.005) (P = 0.17), although more experienced surgeons performed better than less experienced ones; a similar fair assessment was found for raters from Europe (κ = 0.309 ± 0.021) and Asia (κ = 0.3 ± 0.006) and for type II, III and IV fractures; the κ value in the first evaluation (0.309) was similar to that in the second evaluation (0.298). The overall κ value of the D-C classification subtypes was significantly higher (0.599 ± 0.217) than that of the new classification, 0.326 ± 0.162 (t = 3.190 P = 0.005). Conclusions: The new classification system showed fair reliability relative to the D-C classification. The reliability of the new classification system was not affected by the specialty or geographic origin of the rater or the evaluation round, only by rater experience level. The concordance was worse for PFNFs with anterior or posterior translation or with a comminuted medial or posterior columns
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