Predictors of Post-Concussion Depressive Symptoms in Patients without an Underlying Mood Disorder

ObjectiveTo identify predictors of post-concussion depressive symptoms (PCDS) in patients without baseline depressive symptoms.BackgroundDepression is common after concussion and affects quality of life and recovery. To date, the most reliable predictor for development of PCDS is existence of an underlying mood disorder. However, few predictors for PCDS in patients without an underlying mood disorder have been found.Design/MethodsA systematic search was conducted using PubMed for all original articles on post-concussion syndrome in subjects older than 18 years and depression published up to May 2, 2019. Studies that described baseline characteristics for those with and without post-concussion depression were included. Two independent authors reviewed all titles/abstracts to identify studies that met selection criteria. Studies describing pediatric presentation were excluded.ResultsPost-concussion depressive symptoms appear to be associated with symptoms of the concussion itself and with increased number of symptoms reported. Repeat concussions may also increase the risk of developing depressive symptoms. In those with persistent post-concussive symptoms, symptoms seem to appear in a predictable sequence, such that symptoms later in the sequence are more likely to be present if symptoms earlier in the sequence were already present. As such, patients reporting persistent depressive symptoms were more likely to also report existence of correlated cognitive (difficulty concentrating or remembering, feeling dazed) and somatic (headache, fatigue, sensitivity to noise and/or light) symptoms that appear earlier in sequence (OR 2.2). No association between age and gender and experience of new-onset depressive symptoms following concussion was found.ConclusionsIn patients without underlying depressive symptoms, predictors such as quantity and characterization of post-concussive symptoms may help elucidate patient profiles vulnerable to development of PCDS. Multiple concussions, presence of multiple post-concussive symptoms, and presence of correlated symptoms appear to be predictive. Familiarization with these predictors may lead to earlier detection and optimal treatment of PCDS.

In-Depth Understanding of Fatigue Micromechanisms in Cemented Carbides: Implications for Optimal Microstructural Tailoring

The fatigue mechanics and mechanisms of cemented carbides (composites usually referred to as hardmetals) are reviewed. The influence of microstructure on strength lessening and subcritical crack growth for these ceramic-metal materials when subjected to cyclic loads are highlighted. The simultaneous role of the ductile metallic binder as a toughening and fatigue-susceptible agent for hardmetals results in a tradeoff between properties measured under monotonic and cyclic loading: fracture strength and toughness on one hand, as compared to fatigue strength and crack growth resistance on the other one. Toughness/fatigue–microstructure correlations are analyzed and rationalized on the basis of specific crack–microstructure interactions, documented by the effective implementation of advanced characterization techniques. As a result, it is concluded that the fatigue sensitivity of cemented carbides may be reduced if either toughening mechanisms beyond ductile ligament bridging, such as crack deflection, are operative, or strain localization within the binder is suppressed. In this regard, grades exhibiting metallic binders of a complex chemical nature and/or distinct microstructural assemblages are proposed as options for effective microstructural tailoring of these materials.

ANALISA PEMBEBANAN DINAMIK PADA BODI PESAWAT TERBANG DENGAN SIMULASI ANSYS 18.1

Fuselage merupakan struktur pesawat dimana sebagai ruang penumpang dan juga barang. Fuselage mengalami pembebanan pada saat pesawat take off, maneuver, dan landing. Salah satu pembebanan pada fuselage adalah tekanan kabin. penggunaan metode FLMs (Fibre Metal Laminates) yang digunakan untuk menahan jalur perambatan retak yang terjadi akibat beban, sehingga beban akan terjadi pada komposit dan merambat ke alumunium secara signifikan retakan yang terjadi pada komposit akan mengurangi dampak pada alumunium. Penelitian ini bertujuan untuk mendapatkan life cycle, equivalent alternating stress, safety factor, dan fatigue sensitivity untuk beban variasi yaitu 1000 kg, 4000 kg, 6000 kg dan 8000 kg. Variasi beban yang diperoleh diambil berdasarkan persamaan hoop stress yaitu 8359,5 kg. Penelitian ini menggunakan software Autodesk Inventor dan ANSYS workbench 18.1. dimana permodelan dibuat pada Autodesk Inventor dan simulasi dilakukan dengan software ANSYS 18.1. model dibuat menggunakan metode FLMs dengan 11 lapisan material Alumunium 7075-T6 dan Composite Epoxy Carbon Woven kemudian beban divariasikan. Hasil penelitian menujukkan bahwa life cycle berkurang dengan bertambahnya beban. Sehingga dengan metode FLMs untuk Alumunium 7075-T6 dan Composite Epoxy Carbon Woven Preperg, umur fatik yang aman didapat 8.341x104 cycle dengan alternating stress 262.6 MPa pada beban 6000 kg pada beban 6000 kg drafik fatigue sensitivity masih menunjukkan cycle 104 pada beban 100%.