Spectrum of injuries associated with paediatric ACL tears: an MRI pictorial review

OBJECTIVE: Magnetic resonance imaging (MRI) findings in anterior cruciate ligament (ACL) injury are well known, but most published reviews show obvious examples of associated injuries and give little focus to paediatric patients. Here, we demonstrate the spectrum of MRI appearances at common sites of associated injury in adolescents with ACL tears, emphasising age-specific issues. METHODS: Pictorial review using images from children with surgically confirmed ACL tears after athletic injury. RESULTS: ACL injury usually occurs with axial rotation in the valgus near full extension. The MRI findings can be obvious and important to management (ACL rupture), subtle but clinically important (lateral meniscus posterior attachment avulsion), obvious and unimportant to management (femoral condyle impaction injury), or subtle and possibly important (medial meniscocapsular junction tear). Paediatric-specific issues of note include tibial spine avulsion, normal difficulty visualising a thin ACL and posterolateral corner structures, and differentiation between incompletely closed physis and impaction fracture. CONCLUSION: ACL tear is only the most obvious sign of a complex injury involving multiple structures. Awareness of the spectrum of secondary findings illustrated here and the features distinguishing them from normal variation can aid in accurate assessment of ACL tears and related injuries, enabling effective treatment planning and assessment of prognosis. TEACHING POINTS: • The ACL in children normally appears thin or attenuated, while thickening and oedema suggest tear. • Displaced medial meniscal tears are significantly more common later post-injury than immediately. • The meniscofemoral ligaments merge with the posterior lateral meniscus, complicating tear assessment. • Tibial plateau impaction fractures can be difficult to distinguish from a partially closed physis. • Axial MR sequences are more sensitive/specific than coronal for diagnosis of medial collateral ligament (MCL) injury

XRD TEM EELS Studies on Memory Device Structures

Over the past decade, numerous emerging memory technologies are being considered as contenders to displace either or both NAND flash and DRAM as scaling limitations of these conventional memories are perceived for applications in mobile devices. Some of these include Magnetic and Spin Transfer Torque Random Access Memory MRAM, STTRAM , Phase Change RAM PCRAM , Ferroelectric RAM and Resistive RAM memories. These technologies can be classified as relying on one of the movements atomic, ionic, electron charge or spin in nanoscale thin films comprising of a variety of materials. The literature shows about 50 elements of the periodic table being investigated for these memory applications owing to their unique physical and chemical properties. Engineering memory devices requires nanoscale characterizations of film stacks for their chemical compositions and crystalline nature in addition to electronic properties such as resistance, magnetization and polarization depending upon the principle involved. This paper focuses on how x ray diffraction XRD , transmission electron microscopy TEM and electron energy loss spectroscopy EELS techniques have been employed to obtain insight into engineering magnetic tunnel junctions MTJ and PCM device

A Pilot Study Of Antihypertensive Therapy In Cerebrovascular Disease

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/111248/1/j.1532-5415.1967.tb02802.x.pd

Random walk generated by random permutations of {1,2,3, ..., n+1}

We study properties of a non-Markovian random walk $X^{(n)}_l$, $l =0,1,2, >...,n$, evolving in discrete time $l$ on a one-dimensional lattice of integers, whose moves to the right or to the left are prescribed by the \text{rise-and-descent} sequences characterizing random permutations $\pi$ of $[n+1] = \{1,2,3, ...,n+1\}$. We determine exactly the probability of finding the end-point $X_n = X^{(n)}_n$ of the trajectory of such a permutation-generated random walk (PGRW) at site $X$, and show that in the limit $n \to \infty$ it converges to a normal distribution with a smaller, compared to the conventional P\'olya random walk, diffusion coefficient. We formulate, as well, an auxiliary stochastic process whose distribution is identic to the distribution of the intermediate points $X^{(n)}_l$, $l < n$, which enables us to obtain the probability measure of different excursions and to define the asymptotic distribution of the number of "turns" of the PGRW trajectories.Comment: text shortened, new results added, appearing in J. Phys.