Ahmed Youssef

Physicochemical and Catalytic Properties of Vanadia/Titania Catalysts. II. Textural Properties

Titania gels Ta and Tb were precipitated from TiCl4 at pH 3.0 and 9.0, respectively, using ammonia solution. Calcination products were obtained by the thermal treatment of the gels at 300, 400, 600, 750 and 1000°C, respectively. Thermal analysis, X-ray diffraction and FT-IR spectroscopy demonstrated that the anatase → rutile transformation commenced when Ta was calcined at 400°C, with the rutile form predominating when calcination was conducted at 600°C. Calcination at 750°C or 1000°C was associated with complete anatase → rutile conversion. The calcination product of Tb at 400°C was pure anatase, transformation to rutile taking place above this temperature and predominating at 600°C. Rutile was the sole phase present when Tb was calcined at 750°C. Vanadia/titania catalysts were obtained by impregnating Ta and Tb with an aqueous solution of NH4VO4 of concentration sufficient to obtain samples containing 4.0, 6.0, 8.0 or 12.0 wt% V2O5. The calcination products at 400°C and 600°C were characterized by thermal analysis, X-ray diffraction, FT-IR spectroscopy, electronic spectral analysis and magnetic susceptibility measurements. The presence of vanadium enhanced the anatase → rutile transformation. The measured X-ray diffraction lines and FT-IR peaks indicated the existence of vanadium as a separate oxide, mainly V2O5. However, the electronic spectra and magnetic susceptibility measurements predicted the possible existence of a V4+ species.

Endoscopic versus Open Approach to the Infratemporal Fossa: A Cadaver Study

Introduction Various lateral and anterior approaches to access the infratemporal fossa (ITF) have been described. We provide our observations regarding the endoscopic transpterygoid and preauricular subtemporal approaches, listing their respective advantages and limitations through cadaveric dissection. Methods A cadaver study was performed on five adult specimens. An endoscopic transpterygoid approach to the ITF was completed bilaterally in three specimens, and an open preauricular ITF approach was performed bilaterally in two specimens. Results After completing the cadaveric dissections, we studied differences between the endoscopic transpterygoid approach and open preauricular subtemporal approaches in regard to exposure and ease of dissection of different structures in the ITF. Conclusions In comparison with a lateral approach, the endonasal endoscopic transpterygoid approach provides better visualization and more direct exposure of median structures such as the nasopharynx, eustachian tube, sella, and clivus. We concluded that the endoscopic transpterygoid approach can be utilized to resect benign lesions and some select group of malignancies involving the infratemporal and middle cranial fossae. Open approaches continue to play an important role, especially in the resection of extensive malignant tumors extending to these regions.

The keyhole retrosigmoid approach to the cerebello-pontine angle: indications, technical modifications, and results.

OBJECTIVES Establish the versatility and usefulness of the keyhole retrosigmoid approach to the cerebello-pontine angle (CPA) in various pathologies. DESIGN Prospective clinical study. SETTING Tertiary referral university hospital. METHODS One hundred twenty-one patients with various pathologies of the CPA underwent the relevant investigations and were operated upon by the retrosigmoid microendoscopic approach. The technical modifications and progression of our technique are described. RESULTS This group consisted of 121 patients (103 men and 28 women). The pathologies included were 60 acoustic neuromas, 28 vestibular neurectomies, nine meningiomas, and four arachnoid cysts. For nonmass lesions, no additional facial nerve injury or deterioration of hearing occurred. Total excision of mass lesions was achieved in 94.5% of cases. Facial nerve integrity was preserved in 92.3% of cases with mass lesions and permanent facial paralysis occurred in 8.3%. There were no mortalities, and the most frequent complication was a delayed cerebrospinal fluid leak from the site of the wound (15%), which was managed conservatively in all cases. CONCLUSIONS The keyhole retrosigmoid approach is a versatile one. It can be used to deal with different pathologies through a unified access, and with the increasing exclusive use of endoscopes, a truly minimally invasive surgery can be achieved.

Neuromuscular dysfunction associated with delayed weaning from mechanical ventilation in patients with respiratory failure

Abstract Background Mechanical ventilation offers essential ventilatory support, while the respiratory system recovers from acute respiratory failure. Yet, invasive mechanical ventilation is associated with risks and complications that prolong the duration of mechanical ventilation and increase the risk of death. Neuromuscular dysfunctions acquired during intensive care unit (ICU) stay are considered to be one of the important factors that impair the weaning process. The aim of this work To evaluate the role of the neuromuscular factors responsible for difficult weaning from mechanical ventilation. Methods The study included 19 patients with difficult weaning from mechanical ventilation from the Alexandria medical respiratory intensive care unit (ICU) during the period from May 2009 till May 2010. The selected patients included patients who need mechanical ventilation for medical reasons, Patient fulfilling the parameters for weaning, (59) with failed spontaneous breathing trial. In the present study EMG and sensory–motor nerve conduction study was done. Results 26% show normal study, 63% showed moderate to severe axonal sensory–motor peripheral neuropathy and 11% showed a picture of myopathy. The study revealed that 33% of the patients with peripheral neuropathy failed weaning trials and finally died. It is also found that drugs taken during ICU stay as corticosteroids and electrolyte disturbances (hypocalcaemia, hypophosphatemia, and hypomagnesaemia) may be related to the occurrence of neuromuscular dysfunctions. The present work also revealed a significant relationship between hypoalbuminemia and neuromuscular dysfunction. Conclusions The present study stresses on the importance of neuromuscular assessment in all cases with difficult weaning as this may be an important contributing factor for difficult weaning and prolonged mechanical ventilation (neuropathic or myopathic in origin). EMG and nerve conduction study may be of help for the detection of such disturbances. So, proper assessment of the neuromuscular apparatus and the management of any disorder may be a great step toward successful weaning.

Sorption of Chromium Ions from Aqueous Solution onto Chemically Activated Carbons Developed from Maize Cobs

Chemically activated carbons were prepared from maize cobs, using phosphoric acid of variable concentration. The textural parameters of the activated carbons were determined from the nitrogen adsorption isotherms measured at 77 K. The chemistry of the carbon surface was determined by measuring the surface pH, the pHPZC and the concentration of the carbon - oxygen groups of the acid type on the carbon surface. Kinetics of Cr(VI) sorption/reduction was investigated at 303 K. Two processes were investigated in terms of kinetics and equilibrium namely; Cr(VI) removal and chromium sorption were studied at various initial pH (1-7). Removal of Cr(VI) shows a maximum at pH 2.5. At pH2.5 is due to proton insufficiency and to the decrease of the extent of Cr(VI) reduction. The chemistry of the surface of activated carbon is an important factor in determining its adsorption capacity from aqueous solutions particularly when the sorption process involves ion exchange.

Removal of Pesticide (Oxamyl) from Water using Activated Carbons Developed from Apricot Stones

Four stream- activated carbons were prepared by carbonizing apricot stones at followed by gasification with steam at to burn-offs=17, 32, 49 and 65%. The textural parameters of these activated carbons were determined from nitrogen adsorption results at 77 K. The total pore volume and the mean pore radius increased with the increase of % burn-off whereas the surface area increased with the increase of burn- off from 17 to 32 and further to 49%. Further increase of burn-off to 65% was associated with a considerable decrease in surface area as a result of pronounced pore widening due to pore erosion. The surface pH values of the carbons investigated range between 7.1 and 8.2. The adsorption of oxamyl onto the activated carbon followed pseudo-second order kinetics and the equilibrium adsorption isotherms fitted Langmuir adsorption model. The adsorption of oxamyl proved to be of the physical type and took place in non-micropores. The amount of oxamyl adsorbed expressed as depends to a large extent to the surface area located in non-micropores , where a straight line relationship passing through the origin was obtained.

Traumatic cerebrospinal fluid leakage following septorhinoplasty

Septoplasty/septorhinoplasty is a common ear, nose and throat procedure offered for those patients with deviated septum who are suffering from nasal obstruction and functional or cosmetic problems. Although it is a basic and simple procedure, it could lead to catastrophic complications including major skull base injuries which result in cerebrospinal fluid (CSF) leaks. We describe two different cases of traumatic CSF leaks following septoplasty/septorhinoplasty at two different sites. The first patient suffered a CSF leak following septoplasty and presented to Alexandria University Hospital. The leak was still active at presentation and identified as coming from a defect in the roof of the sphenoid sinus and was repaired surgically. The second patient presented 4 days after her cosmetic septorhinoplasty with a CSF leak and significant pneumocephalus. She was managed conservatively. Understanding the anatomical variations of the paranasal sinuses and implementing proper surgical techniques are crucial in preventing intracranial complications when performing either septoplasty or septorhinoplasty. A good quality computed tomography of the nose and paranasal sinuses is a valuable investigation to avoid major complications especially CSF leaks following either procedure.

Endoscopic approach to the infratemporal fossa

Abstract Introduction Multiple surgical approaches have been described to access the infratemporal fossa. One of them is the endoscopic endonasal transpterygoid approach to the infratemporal fossa. The endoscopic endonasal transpterygoid approach is considered the best to access the midline structures such as the nasopharynx, Eustachian tube, sella, and clivus. Through this work, we try to describe the anatomical structures and landmarks of the infratemporal fossa from the endosopic endonasal transpterygoid point of view. Methods A cadaveric study was performed on five adult specimens. Endoscopic medial maxillectomy and complete resection of the posterior wall of the maxillary antrum were performed. Extension of the medial maxillectomy anteriorly was done to reach the lateral part of the infratemporal fossa. Endoscopic Denker’s or Sturman–Canfield approach was done. Dissection of the pterygopalatine fossa was done with identification of maxillary artery branches, V2 (maxillary nerve) and masticatory muscles. Resection of the lateral pterygoid muscle and drilling the lateral pterygoid plate improve exposure of the infratemporal fossa, including V3 (mandibular nerve), which lies posterior to the lateral pterygoid plate. Results A total of ten infratemporal and pterygopalatine fossae (five cadaveric specimens) were dissected endoscopically using a transpterygoid approach. Dissection of different anatomical structures in the infratemporal fossa was done to describe the anatomical structures and landmarks of the infratemporal fossa. Conclusions Endoscopic endonasal transpterygoid approach is considered one of the most useful surgical solutions to manage selected tumors that involve the infratemporal fossa. A good understanding of the endoscopic anatomy of infratemporal fossa allows safe and complete resection of lesions arising or extending to infratemporal fossa.