Effect of chemical composition, defect structure, and stress state on the elastic properties of (V1-x Al x )1-y N y .

For (V1-x Al x )1-y N y  an extensive and theoretically unexplained spread in experimentally obtained elastic moduli ranging from 254 to 599 GPa is reported in literature. To identify its origin, the effect of chemical composition (0 ⩽ x ⩽ 0.75), non-metal to metal ratio (N/M-ratio: 0.48 ⩽ y  ⩽ 0.52), and stress state (-6 ⩽ σ ⩽ 2 GPa) on the elastic modulus at room temperature is studied sytematically by density functional theory employing the Debye-Grüneisen model. As the Al concentration is increased from x = 0 to x = 0.75, strong Al-N sp3d2 hybridization causes an increase in elastic modulus of 26%. The effect of the N/M-ratio on the elastic properties is also Al content dependent. As y  is increased from y  = 0.50 to y  = 0.52, decreasing bond distance upon vacancy formation causes an anomalous increase in the elastic modulus of 6% for V1-y N y , while a decrease in elastic modulus of up to 5% occurs for (V1-x Al x )1-y N y . A stress state variation from +2 to -6 GPa increases the elastic modulus e.g. for (V0.5Al0.5)0.5N0.5 by 70 GPa and hence 13% due to shifts in density of states towards lower energies implying bond strengthening. Thus, it is suggested that the extensive spread of 58% in reported elastic moduli for (V1-x Al x )1-y N y  can at least in part be rationalized based on variations in chemical composition, off-stoichiometry induced point defects, and stress state.

Global Risk Profile Verification in Patients with Venous Thromboembolism (GRIP VTE) in 5 Gulf countries.

BACKGROUND: The Global Risk Profile Verification in Patients with Venous Thromboembolism was the first prospective multicenter registry conducted in Arabian Gulf countries to explore the epidemiology of venous thromboembolic (VTE) disorders and to provide data on diagnosis and disease management. METHODS: Data on 242 patients with confirmed VTE were submitted between September 2003 and November 2003 from 28 contributing hospitals in the Arabian Gulf region. Differences between groups were assessed by the chi(2) test or Fisher exact test for categorical variables. The Student's t test was used for testing proportions. RESULTS: The frequency of VTE cases is deep vein thrombosis (DVT), 187 (77.27%); pulmonary embolism (PE), 35 (14.46%); and DVT with PE, 20 (8.26%). The most common symptoms of DVT and DVT/PE patients were calf pain (72%), calf swelling (63.8%), and localized tenderness (52.2%). The most common symptoms in patients with PE alone and DVT/PE were dyspnea (83.6%), thoracic pain (69.1%), and cough (40%). Risk factors for VTE were immobilization (41.3%), age >65 years (28.9%), a history of VTE (20.7%), and trauma (19%). Among surgical interventions, orthopedic procedures induced the greatest number of VTE cases, followed by general surgery and gynecological procedures. Low-molecular-weight heparins were chosen to treat 33.7% of DVT cases, whereas unfractionated heparin was used in 21.9% of cases. CONCLUSION: VTE remains a common problem in medical and surgical patients in the Arabian Gulf states. Recognition of the common risk factors is of extreme importance to implement the appropriate prophylactic strategy according to the published guidelines.