Hydration-induced nano- to micro-scale self-recovery of the tooth enamel of the giant panda.

The tooth enamel of vertebrates comprises a hyper-mineralized bioceramic, but is distinguished by an exceptional durability to resist impact and wear throughout the lifetime of organisms; however, enamels exhibit a low resistance to the initiation of large-scale cracks comparable to that of geological minerals based on fracture mechanics. Here we reveal that the tooth enamel, specifically from the giant panda, is capable of developing durability through counteracting the early stage of damage by partially recovering its innate geometry and structure at nano- to micro- length-scales autonomously. Such an attribute results essentially from the unique architecture of tooth enamel, specifically the vertical alignment of nano-scale mineral fibers and micro-scale prisms within a water-responsive organic-rich matrix, and can lead to a decrease in the dimension of indent damage in enamel introduced by indentation. Hydration plays an effective role in promoting the recovery process and improving the indentation fracture toughness of enamel (by ∼73%), at a minor cost of micro-hardness (by ∼5%), as compared to the dehydrated state. The nano-scale mechanisms that are responsible for the recovery deformation, specifically the reorientation and rearrangement of mineral fragments and the inter- and intra-prismatic sliding between constituents that are closely related to the viscoelasticity of organic matrix, are examined and analyzed with respect to the structure of tooth enamel. Our study sheds new light on the strategies underlying Nature's design of durable ceramics which could be translated into man-made systems in developing high-performance ceramic materials. STATEMENT OF SIGNIFICANCE: Tooth enamel plays a critical role in the function of teeth by providing a hard surface layer to resist wear/impact throughout the lifetime of organisms; however, such enamel exhibits a remarkably low resistance to the initiation of large-scale cracks, of hundreds of micrometers or more, comparable to that of geological minerals. Here we reveal that tooth enamel, specifically that of the giant panda, is capable of partially recovering its geometry and structure to counteract the early stages of damage at nano- to micro-scale dimensions autonomously. Such an attribute results essentially from the architecture of enamel but is markedly enhanced by hydration. Our work discerns a series of mechanisms that lead to the deformation and recovery of enamel and identifies a unique source of durability in the enamel to accomplish this function. The ingenious design of tooth enamel may inspire the development of new durable ceramic materials in man-made systems.

Good neurological recovery after rescue thrombolysis of presumed pulmonary embolism despite prior 100 minutes CPR.

We reported the case of a 70-year-old man who was admitted to neurologic wards for recurrent syncope for 3 years. Unfortunately, just 2 hours after his admission, he suddenly collapsed and failed to return of spontaneous circulation (ROSC) after a 100-minute standard cardiopulmonary resuscitation (CPR). Fortunately, he was timely suspected to have pulmonary embolism (PE) based on his sedentary lifestyle, elevated D-dimer and markedly enlarged right ventricle chamber on bedside echocardiography. After a rescue thrombolytic alteplase therapy, he was successfully resuscitated and good neurological recovery was achieved.

Association between XRCC1 gene polymorphisms and risk of glioma development: a meta-analysis.

OBJECTIVE: Previous studies of the association between X-ray cross-complementing group 1 (XRCC1) gene polymorphisms and the gliomas risk have yielded conflicting results, and thus a meta-analysis was performed to provide a more accurate estimation. METHODS: A computerized literature search of 5 electronic databases was conducted to identify the relevant studies. Fixed or random effect models were selected based on the heterogeneity test. Publication bias was estimated using Begg's funnel plots and Egger's regression test. RESULTS: A total of 11 studies (3,810 cases and 6,079 controls), 7 studies (2,928 cases and 5,048 controls), and 4 studies (1,461 cases and 2,593 controls) were finally included in the analyses of the association between XRCC1 Arg399Gln, Arg194Trp, and Arg280His polymorphisms and glioma risk, respectively. The pooled results showed that GlnGln carriage was associated with moderately increased risk of gliomas in Asians (GlnGln vs. ArgArg, OR=1.490, 95%CI 1.031-2.153; GlnGln/ArgGln vs. ArgArg, OR=1.321, 95%CI 1.037- 1.684), whereas a marginal association was revealed in Caucasians. For the Arg194Trp polymorphism, although a significant association was shown in the homozygous genotype comparisons (TrpTrp vs. ArgArg, OR = 2.209, 95%CI 1.398- 2.945), no significant link was found on subgroup analysis stratified by ethnicity. With regard to the Arg280His polymorphism, no significant association was found in each comparison. No particular study was found to significantly influence the pooled results, and no potential publication bias was detected. CONCLUSIONS: This meta-analysis suggested that the XRCC1 Arg399Gln polymorphism is moderately associated with increased risk of gliomas in Asians, while Arg194Trp and Arg280His polymorphisms demonstrated no significant influence. Due to the limited studies and the potential confounders, further studies are needed to confirm these results.

[Time distribution characteristics of traffic injury in different age groups in Beijing from 2004 to 2008].

OBJECTIVE: To analyze the time distributions of traffic accidents happening in different age groups in Beijing from 2004 to 2008, and to provide information on the prevention and rescue. METHODS: The traffic injury cases recorded by Beijing Emergency Medical Center from 2004 to 2008 were analyzed, and the data were separated by age: the youth (0-17 years old), the adult (18-64 years old) and the senior adult (above 65 years old). The constituent ratios of hours and months were calculated to describe the states and time distributions of all the cases. RESULTS: The high peaks of accidents for the youth group occurred in the periods 7:00 to 8:00 (6.77%, 39) and 16:00 to 18:00 (10.38%, 60;10.73%, 62), and for the senior adult group appeared in the period 9:00 to 11:00 (11.19%, 151; 11.04%, 149). The adult group showed a stable trend during the period 8:00 to 24:00. The amount of traffic injury happening in these three groups had the same status monthly, which turned out that most traffic accidents happened in October for all the groups (12.11%, 70; 10.38%, 1 257; 12.30%, 166), and February had the smallest number (4.15%, 24; 5.28%, 640; 5.26%, 71). CONCLUSION: The time distributions of traffic injury within these three groups do not show the same situation daily but do monthly. The emergency treatment team and traffic control personnel should pay attention to this and have special protocol for different cases to increase the efficiency of the prehospital rescue.

[Characteristics analyses of road traffic injury in Beijing in 2009].

OBJECTIVE: To analyze the characteristics and laws of road traffic accidents in Beijing, and provide some accident-prevention measures. METHODS: The data from Beijing Emergency Medical Center were managed by computer,then the descriptive statistical analyses were made. RESULTS: (1) A total of 2 984 traffic accidents with relatively complete information were recorded in our research,in which 42 people were led to death and 2 942 injured. Most of the casualties were male. The ages of the injured segments were mainly between 18 to 59 years.(2) The number of the injured in accidents between the motor vehicles was the largest, which was 1 883; The deaths caused by accidents between the motor vehicles and pedestrians were the most, with the number of 26;Major vicious accidents were mainly caused by accidents between the motor vehicles and the number was 11.(3) In one day accidents mainly happened at 8:00-10:00 ,and 14:00-18:00.(4) The most common injuries were the head and face injuries, with the number of 921, followed by multi-site combined injuries with the number of 761, and lower limb injuries, with the number of 541.(5) Human factors were the main causes of accidents, followed by vehicle factors. CONCLUSION: The illegal driving and walking through the pedestrian lane were the main causes of car accidents. Strengthening traffic safety education of the public, especially of the floating population, rigorous training of drivers for traffic rules and regulations, enhancing the public awareness of road safety, and improving the road traffic management and control measures were the main measures to prevent and control traffic injuries.