Modification of as-cast Al-Mg/B4C composite by addition of Zr

Zirconium was used in Al-Mg/B4C composite to improve compocasting efficiency by increasing particle incorporation. Scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) results revealed that by addition of zirconium a reaction layer containing Zr, Al, B and C is formed on the interface of B4C-matrix. X-ray diffraction (XRD) analysis of extracted particles unveiled that the ZrB2 phase is the main constituent of this layer. Formation of ZrB2 is an exothermic reaction which can rise temperature locally around particles and agglomerates. Rising temperature around agglomerates in conjunction with turbulent flow of melt facilitates agglomerates wetting and dissolving into molten aluminum. As the result, final product contains more uniformly distributed B4C particles. Besides enhancing compocasting efficiency, addition of Zr and formation of reaction layer by improving particle matrix bonding quality, led to increase in ultimate tensile strength and elongation of the composite around 8% and 30%, respectively. SEM observations of the fracture surfaces confirmed that a proper bonding presents at the interface of particles and matrix in presence of Zr.Peer ReviewedPostprint (author's final draft

Freezing point depression and freeze-thaw damage by nano-fuidic salt trapping

A remarkable variety of organisms and wet materials are able to endure temperatures far below the freezing point of bulk water. Cryo-tolerance in biology is usually attributed to "anti-freeze" proteins, and yet massive supercooling ($< -40^\circ$C) is also possible in porous media containing only simple aqueous electrolytes. For concrete pavements, the common wisdom is that freeze-thaw damage results from the expansion of water upon freezing, but this cannot explain the large pressures ($> 10$~MPa) required to damage concrete, the observed correlation between pavement damage and de-icing salts, or the damage of cement paste loaded with benzene (which contracts upon freezing). In this Letter, we propose a different mechanism -- nanofluidic salt trapping -- which can explain the observations, using simple mathematical models of dissolved ions confined to thin liquid films between growing ice and charged surfaces. Although trapped salt lowers the freezing point, ice nucleation in charged pores causes enormous disjoining pressures via the rejected ions, until their removal by precipitation or surface adsorption at a lower temperatures releases the pressure and allows complete freezing. The theory is able to predict the non-monotonic salt-concentration dependence of freeze-thaw damage in concreter and provides a general framework to understand the origins of cryo-tolerance.Comment: 5 figure

Seat Belt Usage in Injured Car Occupants: Injury Patterns, Severity and Outcome After Two Main Car Accident Mechanisms in Kashan, Iran, 2012

Background: Road traffic accidents (RTAs) are the main public health problems in Iran. The seat belts, which are vehicle safety devices, are imperative to reduce the risk of severe injuries and mortality. Objectives: The aim of the study was to evaluate injury patterns, severity and outcome among belted and unbelted car occupants who were injured in car accidents. Patients and Methods: This cross-sectional prospective study was performed on all car occupants injured in RTAs (n = 822) who were transported to hospital and hospitalized for more than 24 hours from March 2012 to March 2013. Demographic profile of the patients, including age, gender, position in the vehicle, the use of seat belts, type of car crashes, injured body regions, revised trauma score (RTS), Glasgow coma score (GCS), duration of hospital stay and mortality rate were analyzed by descriptive analysis, chi-square and independent t-test. P < 0.05 was considered significant. Results: A total of 560 patients used seat belts (68.1%). The unbelted occupants were younger (28 years vs. 38 years) and had more frequently sustained head, abdomen and multiple injuries (P = 0.01, P = 0.01 and P = 0.009, respectively). Also, these patients had significantly lower GCS and elongated hospitalization and higher death rate (P = 0.001, P = 0.001 and P = 0.05, respectively). Tendency of severe head trauma and low RTS and death were increased in unbelted occupants in car rollover accident mechanisms (P = 0.001, P = 0.01 and P = 0.008, respectively). Conclusions: During car crashes, especially car rollover, unbelted occupants are more likely to sustain multiple severe injuries and death. Law enforcement of the seat belt usage for all occupants (front and rear seat) is obligatory to reduce severe injuries sustained as a result of car accidents, especially in vehicles with low safety

Chest Injury Evaluation and Management in Two Major Trauma Centers of Isfahan Province, IR Iran

Background:: Chest trauma is responsible for 50% of deaths due to trauma. This kind of death usually occurs immediately after the trauma has occurred. Objectives:: The aim of this study was to evaluate the various aspects of chest trauma in patients admitted to two main trauma centers located in the Isfahan Province, Iran. Patients and Methods:: During a six month period, a cross-sectional study of 100 patients who had sustained a chest injury was carried out. Data, including; age, sex, time of accident, trauma mechanism, organ injury, hospitalization length, complications, and patient outcomes were recorded and analyzed. Results:: The mean ages of the patients were 24.7 ± 3.1 years. Men were injured four times more often than the women. Blunt trauma was the most common type of injury. The incidence of hemothorax was 38% in blunt traumas, and 45% (P = 0.01) in penetrating ones. The incidence of pneumothorax was 43% in blunt traumas and 20% in penetrating ones (P = 0.03). The length of hospitalization was 7.2 ± 3.2 days for blunt and 10.1 ± 3.1 days for penetrating chest traumas. Five patients (5%) died during hospitalization, three of those deaths were due to arterial injuries and two cases were due to lung contusions. Conclusions:: Since hemothorax is the main complication of blunt chest trauma in young men, we recommend that special consideration needs to be made to any case of chest trauma, especially blunt chest injuries

Dynamic deformation response of Al-Mg and Al-Mg/B4C composite at elevated temperatures

The dynamic deformations at high temperatures of Al-3 wt%Mg alloy and Al-3 wt%Mg/B4C composites with different volume fractions and particle sizes were studied using a dilatometer deformation instrument and a split Hopkinson pressure bar operating at strain rates of 10–1000 1/s. A comprehensive analytical procedure was developed to correct the effects of adiabatic heating, friction at interface of the specimen and bars, and strain rate variation, on flow stress curves. Then based on corrected data, a physical based constitutive equation was developed for modeling and prediction of flow stress. It was observed that composites in comparison with single phase alloy, after initial straining, showed lower hardening rate which is unexpected. EBSD micrographs and finite element analysis were used to investigate microstructural evolution and deformation condition around particles. It was concluded that particle fracture during deformation which is more expectable in larger particles, and also higher adiabatic heating in composite and not recrystallization related phenomena, are the main reasons for softening of stress flow curves at large deformation.Peer ReviewedPostprint (author's final draft

Microstructural investigation of Al-Mg/B4C composite deformed at elevated temperature

The microstructure evolution of Al-3wt.%Mg reinforced with 10¿vol% B4C during isothermal compression at temperatures ranging 300–500¿°C at strain rates of 0.001–10 s-1 was investigated by electron backscatter diffraction (EBSD). According to the results, at strain rates lower than 0.01 s-1 and temperatures higher than 400¿°C, the grain size distribution in the microstructure is uniform, dynamic recovery is the predominant softening mechanism and continues recrystallization through lattice rotation is responsible for grain refinement. However, during deformation at higher strain rates or lower temperatures, deformation zones appeared in special locations around particles where microstructure is formed by recovered and hardened grains, and particle stimulating nucleation leaded to partially discontinues dynamic recrystallization which in turns promoted finer average grain and sub-grain size than those in single phase Al-Mg alloy. Moreover, it was found that the variation of grain and sub-grain size with deformation parameters (Zener-Holloman parameter (Z)) can be described by a power law type equation rather than by an initially expected exponential expression.Peer ReviewedPostprint (author's final draft

Comparison of the pharyngeal airway in snoring and non-snoring patients based on the lateral cephalometric study: a case-control study

BACKGROUND: Normal airways are a key factor during the craniofacial growth of the young. Therefore, sleep-disordered breathing (SDB) without treatment can have harmful consequences for development and health. OBJECTIVES: This study aimed to evaluate the cephalometric characteristics in non-snoring individuals and snoring subjects, and investigate differences in the pharyngeal airway space between the 2 groups. MATERIAL AND METHODS: This case-control study included 70 patients aged over 18 years, selected from a radiology center. The patients were divided into 2 groups: case (35 patients with a history of habitual snoring); and control (35 healthy patients). The Berlin sleep questionnaire was administered to the parents of the patients. The nasopharyngeal airway was measured according to the analysis of Linder-Aronson (1970), and 4 indices were measured and analyzed in each of the lateral cephalometric radiographs. RESULTS: No statistically significant differences were observed in the pharyngeal measurements between the 2 groups, although all means in the control group were higher than in the experimental group. However, there was a significant relationship between gender and the Ba-S-PNS and PNS-AD2 indices. CONCLUSIONS: Although the patients with nocturnal snoring had smaller airway dimensions, their pharyngeal measurements were not significantly different from the control group

Blunt Traumatic Hernia of Diaphragm With Late Presentation

Background: Diaphragmatic hernia after blunt trauma is an uncommon and often undiagnosed condition. Objectives: We aimed to review patients who presented with delayed blunt traumatic hernia of diaphragm. Patients and Methods: In this retrospective study, the medical records of six patients treated for blunt diaphragmatic hernias who were admitted to Kashan Shahid Beheshti hospital between June 2007 and June 2011 were analyzed. Results: Six patients with mean age of 41 years were included in the study. Male to female ratio was 2:1. Mean duration between trauma and admission to the hospital was 6.5 years (2 – 26 years). Five patients had left-sided diaphragmatic hernia. Chest X-ray was obtained from all patients which was diagnostic in 50 percent of the cases (n = 4). Additional diagnostic imaging with computerized tomography (CT) was used in six patients and upper gastrointestinal (GI) contrast study was performed in one patient. All patients underwent thoracotomy incision. Mesh repair was utilized in one patient. The mean hospitalization time was 14.1 days. There was one postoperative death (16.7%). Conclusions: Late presentation of blunt diaphragmatic hernia is an uncommon and challenging situation for the surgeon. Prompt diagnosis and treatment prevent serious morbidity and mortality associated with complications such as gangrene and perforation of herniated organ

The effects of dried tomato pomace and a multipleenzyme mixture supplementation (Rovabio ExcelTM) on performance and carcass quality of broiler chickens

An experiment was conducted to study the effect of dried tomato pomace (DTP) and a multienzyme preparation supplementation (Rovabio ExcelTM) on the performance and carcass quality of broiler chickens. A 4 × 2 factorial arrangement of treatments comprising 4 dietary DTP levels (0, 8, 16 and 24%) with and without enzyme supplementation was used. Each diet was fed to 4 replicates pens of 8 broiler chicks from 1 to 42 days posthatch as a coarse mash. The addition of DTP up to 16% to broiler diets did not significantly affect feed intake (FI), body weight gain (BWG) and feed conversion ratio (FCR) during starter (1 to 21 days), growing (22 to 42 days) and entire experimental (1 to 42 days) periods. Inclusion of 24% DTP into the diet significantly decreased FI at starter and entire experimental periods. Also, inclusion of 24% DTP into the diets significantly decreased BWG and increased FCR at all periods. Birds fed the diets supplemented with Rovabio ExcelTM had significantly higher BWG during the starter and entire experimental periods. No significant effect of enzyme addition was observed on FI and FCR. The dietary treatments with or without enzyme did not significantly affect mortality. The 8% DTP-fed group had comparable carcass weight, carcass yield, yield of breast, thigh, abdominal fat, heart, liver and gizzard with those of control group. The higher levels of DTP significantly decreased carcass weight and yield, yield of breast and thigh when compared to the control group. Enzyme supplementation significantly increased carcass weight and yield of abdominal fat. No significant interactions between the DTP and enzyme were observed for performance parameters and carcass characteristics. These results demonstrate that supplementation of DTP up to 8% to broiler diets had no significant adverse effects on performance parameters and carcass characteristics. The enzyme had a significant effect on BWG, carcass weight and yield of abdominal fat.Key words: Dried tomato pomace, enzyme, performance, carcass quality, broiler

Pre-Hospital Trauma Care in Road Traffic Accidents in Kashan, Iran

Background: Iran has one of the highest rates of road traffic accidents (RTAs) worldwide. Pre-hospital trauma care can help minimize many instances of traffic-related mortality and morbidity. Objectives: The aim of this study was to assess the characteristics of pre-hospital care in patients who were injured in RTAs, admitted to hospital. The focus was mainly directed at evaluating pre-hospital trauma care provided in city streets and roads out of the city. Patients and Methods: This retrospective study was carried out on all trauma patients, transported by the emergency medical service (EMS) system, who were admitted to Kashan Shahid-Beheshti hospital during the period from March 2011 to March 2012. The patients’ demographic data, location of accident, damaged organs, mechanism of injury, injury severity, pre-hospital times (response, scene, transport), pre-hospital interventions and outcomes, were extracted from the data registry and analyzed through descriptive statistics using SPSS 18 software. Results: Findings of this study showed that, 75% of RTAs occurred on city streets (n = 1 251). Motor-car accidents were the most frequent mechanism of RTA on city streets (n = 525) (42%), while car rollover was the most frequent mechanism of RTA on roads out of the city (n = 155) (44.4%). The mean pre-hospital time intervals (min); response, scene, and transport for all patients were 6.6 ± 3.1, 10.7 ± 5 and 13 ± 9.8, respectively. The mean pre-hospital time intervals (response, scene, transport) in roads out of the city were higher than those in city streets. There was a significant difference (P = 0.04) in the mortality rates due to RTAs between city streets (n = 46) and roads out of the city (n = 32). Conclusions: In comparison with road traffic accidents on city streets, trauma patients in RTAs on roads out of the city have longer pre-hospital time intervals and more severe injuries; therefore this group needs more pre-hospital resuscitation interventions