Ahmed Shabana - Academia.edu (original) (raw)
Papers by Ahmed Shabana
Theoretical calculations are typically utilized for examining intermetallic interactions. However... more Theoretical calculations are typically utilized for examining intermetallic interactions. However, to validate theory, experimental confirmation of the existence of these interactions is necessary. We synthesized new heterometallic Ln–Pt complexes, NEt4{[Pt(PhSAc)4]Ln[(PhSAc)4Pt]}·2DMF (Ln: lanthanoid = Gd (1), Tb (2), Dy (3), PhSAc = benzothioacetate, NEt4 = tetraethylammonium), in which both diamagnetic Pt(II) ions interact with the central Ln(III) ion. Typically, these interactions are not detected, because the distance between Ln and Pt atoms (~3.6 Å) is much larger than the covalent radius (~3.3 Å) and ionic radius (~3.10 Å). Pt-LIII resonant inelastic X-ray scattering (RIXS) analysis was conducted to experimentally confirm the unique influence of the hidden Ln–Pt interaction on the luminescence of the Tb–Pt molecule, where the interaction induced emission properties in the Tb and Pt ions, with high quantum yield (59%). Quantum theory of atoms in molecules (QTAIM) analysis was ...
Vibration of Discrete and Continuous Systems, 1997
Vibration of Discrete and Continuous Systems, 2019
Lanthanide (Ln) compounds are common research targets in the field of magnetism and optics. Their... more Lanthanide (Ln) compounds are common research targets in the field of magnetism and optics. Their properties arise from the electron localized in the f-orbital. Moreover, the effect of the covalency between lanthanide and ligands on magnetism attracted significant attention. We provided insight into the Gd–Pt bond (of the heterometallic Ln-Pt complexes: {[Pt(PhSAc)4]Ln[(PhSAc)4Pt]} NEt4·2DMF (Ln = Y(0), La(1), Gd(2); PhSAc = thiobenzoate, NEt4 = tetraethylammonium)); single-crystal polarized X-ray absorption near edge structure (XANES) reveal the electronic states around metal ion, where spectra of Gd-LIII edges show the Gd–Pt direction has the highest covalency (less ionic) around Gd ion in 2. In addition, calculating natural bonding (NBO) analysis, natural population analysis (NPA), LOL, and atoms in molecules (AIM), ab initio calculations reveal the role of metallic and organic ligands in the electronic and magnetic properties of Ln complexes. The slow magnetization relaxation of...
Anaesthesia, 2021
SummaryPeri‐operative SARS‐CoV‐2 infection increases postoperative mortality. The aim of this stu... more SummaryPeri‐operative SARS‐CoV‐2 infection increases postoperative mortality. The aim of this study was to determine the optimal duration of planned delay before surgery in patients who have had SARS‐CoV‐2 infection. This international, multicentre, prospective cohort study included patients undergoing elective or emergency surgery during October 2020. Surgical patients with pre‐operative SARS‐CoV‐2 infection were compared with those without previous SARS‐CoV‐2 infection. The primary outcome measure was 30‐day postoperative mortality. Logistic regression models were used to calculate adjusted 30‐day mortality rates stratified by time from diagnosis of SARS‐CoV‐2 infection to surgery. Among 140,231 patients (116 countries), 3127 patients (2.2%) had a pre‐operative SARS‐CoV‐2 diagnosis. Adjusted 30‐day mortality in patients without SARS‐CoV‐2 infection was 1.5% (95%CI 1.4–1.5). In patients with a pre‐operative SARS‐CoV‐2 diagnosis, mortality was increased in patients having surgery wi...
Nonlinear Dynamics, 2021
A mechanics-based description of motion-trajectory (MT) curves is used in this investigation to i... more A mechanics-based description of motion-trajectory (MT) curves is used in this investigation to introduce Frenet oscillations. These oscillations define the time-varying orientation of the motion plane that contains the absolute velocity and acceleration vectors in terms of three Frenet-Euler angles; the curvature, vertical-development, and bank angles, referred to as the Frenet angles for brevity. The Frenet bank angle and the associated Frenet super-elevation of the motion plane, which measure the deviation of the centrifugal inertia force from the horizontal plane, can be used to shed light on the definition of the balance speed used in practice. The concept of the pre-superelevated osculating (PSEO) plane is introduced and Rodrigues' formula is employed to develop an orthogonal rotation matrix that provides a geometric interpretation of the PSEO plane. A new inverse-dynamics problem that utilizes experimentally or simulation recorded motion trajectories (RMT) is used to define the Frenet inertia forces and demonstrate their equivalence to the Cartesian form of the inertia forces. New expressions for the curvature vector in terms of the velocity and acceleration, limit on the magnitude of the tangential acceleration for a given forward velocity, condition required for the centrifugal force to remain horizontal, and condition of curvature singular points that corresponds to zero absolute acceleration are derived. The Frenet bank angle can be used to prove the existence of the normal vectors at the curvature singular points. It is shown that the inertia force can assume different forms, depending on the curve parameter used, and if the arc length parameter is not used as the curve parameter, the inverse-problem equation can include a quadratic-velocity inertia force vector. The results of a simple analytical curve demonstrate the concept of the Frenet oscillations and importance of distinguishing between the highway-ramp and railroad track bank angles and super-elevations, which are time-invariant, and the Frenet bank angle and super-elevation, which are motion-dependent.
![Research paper thumbnail of DNA interaction and anticancer evaluation of new zinc(II), ruthenium(II), rhodium(III), palladium(II), silver(I) and platinum(II) complexes based on kojic acid; X-ray crystal structure of [Ag(ka)(PPh3)]·H2O](https://attachments.academia-assets.com/113734153/thumbnails/1.jpg)
](Inorganica Chimica Acta, 2019
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service... more This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. DNA Interaction and Anticancer Evaluation of New Palladium(II), Platinum(II) and Silver(I) Complexes Based on (∆ ∆ ∆ ∆)and (Λ Λ Λ Λ)-1,2-Bis-(1H-benzimidazol-2-yl)-1,2-ethanediol Enantiomers
Journal of Mechanisms, Transmissions, and Automation in Design, 1988
A method for the dynamic analysis of flexible legged locomotion systems that accounts for the rot... more A method for the dynamic analysis of flexible legged locomotion systems that accounts for the rotary inertia and shear deformation effects is presented. The motion of the flexible components in the legged vehicle is described using a set of inertia-variant Timoshenko beams that undergo large rotations. A shape function that accounts for the combined effect of rotary inertia and shear is employed to describe the deformation relative to a selected component reference and the rigid-body modes of the shape function are eliminated using a set of reference conditions. Kinetic and strain energies are derived for each Timoshenko beam, thus identifying the beam mass and stiffness matrices which account for the rotary inertia and shear deformation effects. A new set of time-invariant matrices that describe the nonlinear inertia coupling between the reference motion and elastic deformation and account for the rotary inertia and shear is developed and it is shown that the form of these matrices...
Tanta Medical Journal, 2014
Background Morbidly adherent placenta is one of the most feared complications causing high morbid... more Background Morbidly adherent placenta is one of the most feared complications causing high morbidity and mortality in obstetrics. Cesarean hysterectomy is still the main procedure in the current management of patients diagnosed with morbidly adherent placenta. Objective To evaluate the efficacy of prophylactic bilateral hypogastric arteries ligation on maternal outcome in diagnosed cases of morbidly adherent placenta. Design Prospective study. Setting Obstetrics and Gynecology Department, Mansoura University Hospital, Egypt. Methods This was a prospective cohort study of 51 pregnant women with a history of previous cesarean sections and diagnosed with low-lying abnormally adherent placenta. All patients underwent prophylactic internal iliac artery ligation after fetal delivery and before extraction of the placenta, the placenta was removed manually in a piecemeal manner and any remaining bleeding points from the placental site were then controlled by hemostatic sutures. Results Bilateral internal iliac artery ligation was performed in patients with invasive placenta (accreta and increta) (46/51 = 90.1%) and satisfactory hemostasis was achieved in 38 patients (38/46 = 82.6%). In five patients with placenta previa increta (5/17 = 29.4%), there was uncontrolled blood loss; thus, we proceeded to cesarean hysterectomy. The mean intraoperative blood loss was 1255 ± 589 ml. Blood transfusion was necessary in 35 patients (35/46 = 76%) during the operations. The mean hemoglobin and hematocrit 1 day after the operation were 9.8 ± 1.3 and 31.4 ± 2.3, respectively. Conclusion Prophylactic bilateral internal iliac artery ligation before extraction of placenta accrete seemed to be an effective technique to decrease cesarean complications and avoid emergent peripartum hysterectomy.
Mechanism and Machine Theory, 1986
Thermal analysis of the transient motion of a multibody system, consisting of interconnected rigi... more Thermal analysis of the transient motion of a multibody system, consisting of interconnected rigid, elastic, and viscoelastic components is presented. The configuration of each elastic or viscoelastic body is identified using three sets of modes, rigid-body, reference and normal modes. Rigid-body modes describe translations and large rotations of the body reference. The finite element method is employed to describe body deformations, and reference conditions are imposed in order to define a unique displacement field. Accordingly, normal modes of vibration of flexible components can be used to reduce the number of elastic coordinates, thus eliminating high-frequency modes of vibration. The system equations of motion are formulated using Lagrange's equation, and nonlinear algebraic equations, describing constraints between adjacent bodies, are coupled to the equations of motion using a Lagrange multiplier technique.
European Journal of Mechanics - A/Solids, 1998
Web-based electronic commerce has moved from the realm of the cyberspace avant-garde to becoming ... more Web-based electronic commerce has moved from the realm of the cyberspace avant-garde to becoming successful enough to attract attention from lawmakers as a potential source of revenue through taxation (Wiseman and Nichols, 1998). As we move into uncharted territory, the players, both individual and institutional alike, fall back on assumptions and modus operandi inherited from more traditional commerce ventures. In this paper, we focus our attention on the principal players, the virtual mall operator and the anchor tenants and the types of relationships that govern them as a first step towards a comprehensive model of electronic commerce for virtual mall and communities. Our initial findings indicate that the traditional shopping center with its ensuing relationships, may not be directly transferable to a virtual setting.
Anaesthesia, 2021
SummarySARS‐CoV‐2 has been associated with an increased rate of venous thromboembolism in critica... more SummarySARS‐CoV‐2 has been associated with an increased rate of venous thromboembolism in critically ill patients. Since surgical patients are already at higher risk of venous thromboembolism than general populations, this study aimed to determine if patients with peri‐operative or prior SARS‐CoV‐2 were at further increased risk of venous thromboembolism. We conducted a planned sub‐study and analysis from an international, multicentre, prospective cohort study of elective and emergency patients undergoing surgery during October 2020. Patients from all surgical specialties were included. The primary outcome measure was venous thromboembolism (pulmonary embolism or deep vein thrombosis) within 30 days of surgery. SARS‐CoV‐2 diagnosis was defined as peri‐operative (7 days before to 30 days after surgery); recent (1–6 weeks before surgery); previous (≥7 weeks before surgery); or none. Information on prophylaxis regimens or pre‐operative anti‐coagulation for baseline comorbidities was no...
Theoretical calculations are typically utilized for examining intermetallic interactions. However... more Theoretical calculations are typically utilized for examining intermetallic interactions. However, to validate theory, experimental confirmation of the existence of these interactions is necessary. We synthesized new heterometallic Ln–Pt complexes, NEt4{[Pt(PhSAc)4]Ln[(PhSAc)4Pt]}·2DMF (Ln: lanthanoid = Gd (1), Tb (2), Dy (3), PhSAc = benzothioacetate, NEt4 = tetraethylammonium), in which both diamagnetic Pt(II) ions interact with the central Ln(III) ion. Typically, these interactions are not detected, because the distance between Ln and Pt atoms (~3.6 Å) is much larger than the covalent radius (~3.3 Å) and ionic radius (~3.10 Å). Pt-LIII resonant inelastic X-ray scattering (RIXS) analysis was conducted to experimentally confirm the unique influence of the hidden Ln–Pt interaction on the luminescence of the Tb–Pt molecule, where the interaction induced emission properties in the Tb and Pt ions, with high quantum yield (59%). Quantum theory of atoms in molecules (QTAIM) analysis was ...
Vibration of Discrete and Continuous Systems, 1997
Vibration of Discrete and Continuous Systems, 2019
Lanthanide (Ln) compounds are common research targets in the field of magnetism and optics. Their... more Lanthanide (Ln) compounds are common research targets in the field of magnetism and optics. Their properties arise from the electron localized in the f-orbital. Moreover, the effect of the covalency between lanthanide and ligands on magnetism attracted significant attention. We provided insight into the Gd–Pt bond (of the heterometallic Ln-Pt complexes: {[Pt(PhSAc)4]Ln[(PhSAc)4Pt]} NEt4·2DMF (Ln = Y(0), La(1), Gd(2); PhSAc = thiobenzoate, NEt4 = tetraethylammonium)); single-crystal polarized X-ray absorption near edge structure (XANES) reveal the electronic states around metal ion, where spectra of Gd-LIII edges show the Gd–Pt direction has the highest covalency (less ionic) around Gd ion in 2. In addition, calculating natural bonding (NBO) analysis, natural population analysis (NPA), LOL, and atoms in molecules (AIM), ab initio calculations reveal the role of metallic and organic ligands in the electronic and magnetic properties of Ln complexes. The slow magnetization relaxation of...
Anaesthesia, 2021
SummaryPeri‐operative SARS‐CoV‐2 infection increases postoperative mortality. The aim of this stu... more SummaryPeri‐operative SARS‐CoV‐2 infection increases postoperative mortality. The aim of this study was to determine the optimal duration of planned delay before surgery in patients who have had SARS‐CoV‐2 infection. This international, multicentre, prospective cohort study included patients undergoing elective or emergency surgery during October 2020. Surgical patients with pre‐operative SARS‐CoV‐2 infection were compared with those without previous SARS‐CoV‐2 infection. The primary outcome measure was 30‐day postoperative mortality. Logistic regression models were used to calculate adjusted 30‐day mortality rates stratified by time from diagnosis of SARS‐CoV‐2 infection to surgery. Among 140,231 patients (116 countries), 3127 patients (2.2%) had a pre‐operative SARS‐CoV‐2 diagnosis. Adjusted 30‐day mortality in patients without SARS‐CoV‐2 infection was 1.5% (95%CI 1.4–1.5). In patients with a pre‐operative SARS‐CoV‐2 diagnosis, mortality was increased in patients having surgery wi...
Nonlinear Dynamics, 2021
A mechanics-based description of motion-trajectory (MT) curves is used in this investigation to i... more A mechanics-based description of motion-trajectory (MT) curves is used in this investigation to introduce Frenet oscillations. These oscillations define the time-varying orientation of the motion plane that contains the absolute velocity and acceleration vectors in terms of three Frenet-Euler angles; the curvature, vertical-development, and bank angles, referred to as the Frenet angles for brevity. The Frenet bank angle and the associated Frenet super-elevation of the motion plane, which measure the deviation of the centrifugal inertia force from the horizontal plane, can be used to shed light on the definition of the balance speed used in practice. The concept of the pre-superelevated osculating (PSEO) plane is introduced and Rodrigues' formula is employed to develop an orthogonal rotation matrix that provides a geometric interpretation of the PSEO plane. A new inverse-dynamics problem that utilizes experimentally or simulation recorded motion trajectories (RMT) is used to define the Frenet inertia forces and demonstrate their equivalence to the Cartesian form of the inertia forces. New expressions for the curvature vector in terms of the velocity and acceleration, limit on the magnitude of the tangential acceleration for a given forward velocity, condition required for the centrifugal force to remain horizontal, and condition of curvature singular points that corresponds to zero absolute acceleration are derived. The Frenet bank angle can be used to prove the existence of the normal vectors at the curvature singular points. It is shown that the inertia force can assume different forms, depending on the curve parameter used, and if the arc length parameter is not used as the curve parameter, the inverse-problem equation can include a quadratic-velocity inertia force vector. The results of a simple analytical curve demonstrate the concept of the Frenet oscillations and importance of distinguishing between the highway-ramp and railroad track bank angles and super-elevations, which are time-invariant, and the Frenet bank angle and super-elevation, which are motion-dependent.
Inorganica Chimica Acta, 2019
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service... more This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. DNA Interaction and Anticancer Evaluation of New Palladium(II), Platinum(II) and Silver(I) Complexes Based on (∆ ∆ ∆ ∆)and (Λ Λ Λ Λ)-1,2-Bis-(1H-benzimidazol-2-yl)-1,2-ethanediol Enantiomers
Journal of Mechanisms, Transmissions, and Automation in Design, 1988
A method for the dynamic analysis of flexible legged locomotion systems that accounts for the rot... more A method for the dynamic analysis of flexible legged locomotion systems that accounts for the rotary inertia and shear deformation effects is presented. The motion of the flexible components in the legged vehicle is described using a set of inertia-variant Timoshenko beams that undergo large rotations. A shape function that accounts for the combined effect of rotary inertia and shear is employed to describe the deformation relative to a selected component reference and the rigid-body modes of the shape function are eliminated using a set of reference conditions. Kinetic and strain energies are derived for each Timoshenko beam, thus identifying the beam mass and stiffness matrices which account for the rotary inertia and shear deformation effects. A new set of time-invariant matrices that describe the nonlinear inertia coupling between the reference motion and elastic deformation and account for the rotary inertia and shear is developed and it is shown that the form of these matrices...
Tanta Medical Journal, 2014
Background Morbidly adherent placenta is one of the most feared complications causing high morbid... more Background Morbidly adherent placenta is one of the most feared complications causing high morbidity and mortality in obstetrics. Cesarean hysterectomy is still the main procedure in the current management of patients diagnosed with morbidly adherent placenta. Objective To evaluate the efficacy of prophylactic bilateral hypogastric arteries ligation on maternal outcome in diagnosed cases of morbidly adherent placenta. Design Prospective study. Setting Obstetrics and Gynecology Department, Mansoura University Hospital, Egypt. Methods This was a prospective cohort study of 51 pregnant women with a history of previous cesarean sections and diagnosed with low-lying abnormally adherent placenta. All patients underwent prophylactic internal iliac artery ligation after fetal delivery and before extraction of the placenta, the placenta was removed manually in a piecemeal manner and any remaining bleeding points from the placental site were then controlled by hemostatic sutures. Results Bilateral internal iliac artery ligation was performed in patients with invasive placenta (accreta and increta) (46/51 = 90.1%) and satisfactory hemostasis was achieved in 38 patients (38/46 = 82.6%). In five patients with placenta previa increta (5/17 = 29.4%), there was uncontrolled blood loss; thus, we proceeded to cesarean hysterectomy. The mean intraoperative blood loss was 1255 ± 589 ml. Blood transfusion was necessary in 35 patients (35/46 = 76%) during the operations. The mean hemoglobin and hematocrit 1 day after the operation were 9.8 ± 1.3 and 31.4 ± 2.3, respectively. Conclusion Prophylactic bilateral internal iliac artery ligation before extraction of placenta accrete seemed to be an effective technique to decrease cesarean complications and avoid emergent peripartum hysterectomy.
Mechanism and Machine Theory, 1986
Thermal analysis of the transient motion of a multibody system, consisting of interconnected rigi... more Thermal analysis of the transient motion of a multibody system, consisting of interconnected rigid, elastic, and viscoelastic components is presented. The configuration of each elastic or viscoelastic body is identified using three sets of modes, rigid-body, reference and normal modes. Rigid-body modes describe translations and large rotations of the body reference. The finite element method is employed to describe body deformations, and reference conditions are imposed in order to define a unique displacement field. Accordingly, normal modes of vibration of flexible components can be used to reduce the number of elastic coordinates, thus eliminating high-frequency modes of vibration. The system equations of motion are formulated using Lagrange's equation, and nonlinear algebraic equations, describing constraints between adjacent bodies, are coupled to the equations of motion using a Lagrange multiplier technique.
European Journal of Mechanics - A/Solids, 1998
Web-based electronic commerce has moved from the realm of the cyberspace avant-garde to becoming ... more Web-based electronic commerce has moved from the realm of the cyberspace avant-garde to becoming successful enough to attract attention from lawmakers as a potential source of revenue through taxation (Wiseman and Nichols, 1998). As we move into uncharted territory, the players, both individual and institutional alike, fall back on assumptions and modus operandi inherited from more traditional commerce ventures. In this paper, we focus our attention on the principal players, the virtual mall operator and the anchor tenants and the types of relationships that govern them as a first step towards a comprehensive model of electronic commerce for virtual mall and communities. Our initial findings indicate that the traditional shopping center with its ensuing relationships, may not be directly transferable to a virtual setting.
Anaesthesia, 2021
SummarySARS‐CoV‐2 has been associated with an increased rate of venous thromboembolism in critica... more SummarySARS‐CoV‐2 has been associated with an increased rate of venous thromboembolism in critically ill patients. Since surgical patients are already at higher risk of venous thromboembolism than general populations, this study aimed to determine if patients with peri‐operative or prior SARS‐CoV‐2 were at further increased risk of venous thromboembolism. We conducted a planned sub‐study and analysis from an international, multicentre, prospective cohort study of elective and emergency patients undergoing surgery during October 2020. Patients from all surgical specialties were included. The primary outcome measure was venous thromboembolism (pulmonary embolism or deep vein thrombosis) within 30 days of surgery. SARS‐CoV‐2 diagnosis was defined as peri‐operative (7 days before to 30 days after surgery); recent (1–6 weeks before surgery); previous (≥7 weeks before surgery); or none. Information on prophylaxis regimens or pre‐operative anti‐coagulation for baseline comorbidities was no...