Simultaneous Bilateral Hip Fractures in an Elderly Patient in the Absence of Bone Disease: A Case Report

Case: Eighty-three years old female patient who sustained a simultaneous bilateral hip fractures after a mechanical fall. The bilateral nature of the problem was not appreciated by the emergency team and was found after the orthopedic consultation. The patient underwent a single stage bilateral cemented bipolar hemiarthroplasty without perioperative complications. Conclusion: Simultaneous bilateral hip fractures in elderly are not commonly encountered after a low energy mechanism but early recognition of this diagnosis is important to optimize perioperative management. Having bilateral cemented stems did not lead to any significant cardiopulmonary complications as can often be concerned with so called cement syndrome.

Breaking down chipping and fragmentation in sediment transport: the control of material strength

As rocks are transported, they primarily undergo two breakdown mechanisms: fragmentation and chipping. Fragmentation is catastrophic breakup by fracture in the bulk – either by subcritical crack growth under repeated collisions, or from a single high-energy (supercritical) collision – and produces angular shards. Chipping is a distinct low-energy mechanism of impact attrition that involves shallow cracking; this process rounds river pebbles in a universal manner under bed-load transport. Despite its geophysical significance, the transition from chipping to fragmentation is not well studied. Here, we examine this transition experimentally by measuring the shape and mass evolution of concrete particles of varying strength, subject to repeated collisions in a rotating drum. For sufficiently strong particles, chipping occurred and was characterized by the following: attrition products were orders of magnitude smaller than the parent; attrition rate was insensitive to material strength; and particles experienced monotonic rounding toward a spherical shape. As strength decreased, we observed the onset of a subcritical cracking regime associated with fragmentation: mass of attrition products became larger and more varied; attrition rate was inversely proportional to material strength; and shape evolution fluctuated and became non-monotonic. Our results validate conceptual and numerical models for impact attrition: chipping follows “Sternberg's law” of exponential mass loss through time; for fragmentation, the lifetime of particles increases nonlinearly with material strength, consistent with “Basquin's law” of fatigue failure. We suggest that bedrock erosion models must be clarified to incorporate distinct attrition mechanisms, and that pebble or bedrock-channel shape may be utilized to deduce the operative mechanism in a given environment.

Noise in a metabolic pathway leads to persister formation in Mycobacterium tuberculosis

Tuberculosis is difficult to treat due to dormant cells in hypoxic granulomas, and stochastically-formed persisters tolerant of antibiotics. Bactericidal antibiotics kill by corrupting their energy-dependent targets. We reasoned that noise in the expression of an energy-generating component will produce rare persister cells. In sorted low ATP M. tuberculosis grown on acetate there is considerable cell-to-cell variation in the level of mRNA coding for AckA, the acetate kinase. Quenching the noise by overexpressing ackA sharply decreases persisters, showing that it acts as the main persister gene under these conditions. This demonstrates that a low energy mechanism is responsible for the formation of M. tuberculosis persisters and suggests that the mechanism of their antibiotic tolerance is similar to that of dormant cells in a granuloma. Entrance into a low energy state driven by stochastic variation in expression of energy-producing enzymes is likely a general mechanism by which bacteria produce persisters.

Sand spikes pinpoint powerful palaeoseismicity

Sand spikes, pin-shaped, carbonate-cemented sandstone bodies of variable size widely interpreted as sedimentary concretions, have been enigmatic for nearly two centuries. We here present a high-energy mechanism for their formation. Two classic sand spike occurrences are found in the North Alpine Foreland Basin of Central Europe and at Mount Signal in southern California, USA. A distinct seismite horizon in Mid-Miocene Molasse sediments of southern Germany, genetically linked with the Ries impact event, exhibits dewatering structures and contains numerous sand spikes with tails systematically orientated away from the Ries crater. Sand spikes at Mount Signal, strikingly similar in shape to those found in Germany, have tails that point away from the nearby San Andreas Fault. Based on their structural and stratigraphic context, we interpret sand spikes as a new type of seismite and a promising tool to identify strong impact-induced or tectonic palaeo-earthquakes and their source regions in the geologic record.

Management of Panfacial Trauma: Sequencing and Pitfalls

Panfacial trauma refers to high-energy mechanism injuries involving two or more areas of the craniofacial skeleton, the frontal bone, the midface, and the occlusal unit. These can be distracting injuries in an unstable patient and, as in any trauma, Advanced Trauma Life Support (ATLS) protocols should be followed. The airway should be secured, bleeding controlled, and sequential examinations should take place to avoid overlooking injuries. When indicated, neurosurgery and ophthalmology should be consulted as preservation of brain, vision, and hearing function should be prioritized. Once the patient is stabilized, reconstruction aims to reduce panfacial fractures, restore the horizontal and vertical facial buttresses, and resuspend the soft tissue to avoid the appearance of premature aging. Lost or comminuted bone can be replaced with bone grafts, although adequate reduction should be ensured prior to any grafting. Operative sequencing can be performed from top-down and outside-in or from bottom-up and inside-out depending on patient presentation. All protocols can successfully manage panfacial injuries, and the emphasis should be placed on a systematic approach that works from known areas to unknown areas.

Acoustic Emission Waveform Analysis of Sandstone Failure with Different Water Content

Previous studies have shown that water can reduce the acoustic emission (AE) energy and other parameters during rock failure. However, the fracture mechanism of rock can be better reflected by analyzing the AE waveform. Therefore, this paper conducted experiments of uniaxial compression on sandstone samples of various water contents and collected AE signals simultaneously. Analyses of fast Fourier transform (FFT) and Hilbert-Huang transform (HHT) were performed on the AE waveform when the sample failed. The results show that as the water content increases, the frequency and intensity of the AE signal will decrease. The influence of water on the intensity of the AE signal is greater than that on the frequency. Through the analysis of the energy mechanism of rock failure, it is pointed out that the frequency and intensity of AE signal are closely related to elastic energy index W ET and burst energy index K E . The research results have guiding significance for the monitoring of rockburst.

Lunate dislocations: anatomy, diagnosis and management

Lunate dislocation is an uncommon but serious wrist injury, often resulting from a high energy mechanism of trauma. Advanced trauma life support protocols should be followed to diagnose and treat concomitant life-threatening pathology. Thorough neurovascular and soft tissue examination is required to identify open wounds and median nerve dysfunction, including acute onset carpal tunnel syndrome. Imaging is undertaken to appreciate injury severity, which is graded by the Mayfield classification. Closed reduction in the emergency department is the initial management, which alleviates pressure on neurovascular structures. Definitive management is surgical, most commonly via open reduction and direct ligamentous stabilisation. The aims of surgery are to restore anatomical carpal alignment and maintain stability, allowing repair and healing of the important wrist ligaments. Medium-to long-term functional outcomes are adequate, with most patients returning to work within 6 months. However, progressive radiographic midcarpal arthrosis is common, as well as permanent loss of grip strength, range of motion and chronic pain. This article considers the anatomy, diagnosis and management of acute lunate and perilunate dislocations.

Study on the effective discharge energy mechanism of vertical ultrasonic vibration assisted EDM processing

Compared to traditional EDM processing, UEDM (Ultrasonic Vibration Assisted EDM) have a great improvement in optimizing discharge environment. In this study, ultrasonic vibration is attached to the electrode. According to the relative positional relationship between the movement path of the electrode tip and the discharge gap, four working states of UEDM are defined. The four working states are the path within the discharge gap, the path in contact with the edge of the discharge gap, part of the electrode end path outside the discharge gap, and the path in contact with the workpiece, respectively. States are analyzed from the effective discharge energy and discharge frequency. A mathematical model for effective discharge energy and surface roughness is established for two conventional working states. The correctness of the theoretical research is verified by experiments. As the experiment results shown, the influence of ultrasonic amplitude on the energy of UEDM is primary, while frequency is secondary. A working state with better discharge stability and higher discharge energy when the electrode end path is in contact with the edge of the discharge gap. In the first three conventional machining states, the surface quality of the workpiece increases with the increase of ultrasonic amplitude and frequency. The study can provide scientific guidance for parameter matching of UEDM.

Deterioration Characteristics and Energy Mechanism of Red-Bed Rocks Subjected to Drying-Wetting Cycles

The red-bed rocks were chosen and studied by using uniaxial compressive experiment and scanning electron microscopy to investigate the effect of drying-wetting (D-W) cycles on the mechanical properties and microstructural characteristics of red-bed rock. Additionally, the energy mechanism of specimens subjected to drying-wetting cycles was also explained. Experimental results showed that, the stress-strain could be divided into four characteristic stages in the compression failure process. After subjecting to cycles of D-W, the stress-strain curve gradually changed from softening to hardening. At the same time, uniaxial compression strength (UCS) and elastic modulus dropped obviously, while Poisson’s ratio gradually raised. Microstructural analysis results indicated that the microstructure of the specimen surface was no longer dense and uniform, and the porosity of tested specimens significantly increased with D-W cycles increasing. As the porosity grew, UCS and elastic modulus gradually declined. According to the first law of thermodynamics, the process of rock failure was an event of energy transfer and conversion. As the number of D-W cycles increased, the energy density of specimens all present linear fell. From the perspective of the theory of energy dissipation, the dissipated energy was essential for rock failure, and closely related to the strength of the specimen. With D-W cycles increasing, the specimens were more prone to failure, and the dissipated energy required for failure decreased gradually.