Management of Tibial Bow in Fibular Deficiency.

BACKGROUND: Deformity of the tibia, including shortening and angulation, may accompany severe forms of postaxial hypoplasia (fibular deficiency). The current literature reflects varying opinions on the appropriate management for tibial deformity in the setting of fibular deficiency. METHODS: We performed a retrospective review to determine outcomes of tibial deformity correction in patients with a primary diagnosis of fibular deficiency. Clinical and radiographic outcomes of patients treated with foot ablation were reviewed to establish indications for tibial deformity correction, identify occurrence of additional surgical procedures related to limb alignment or deformity, and characterize difficulties with prosthetic wear potentially related to residual or recurrent tibial deformity. RESULTS: From 1989 to 2016, 51 patients (57 extremities) with fibular deficiency were managed with a foot ablation procedure. Twenty-five (44%) had simultaneous correction of the tibial deformity. The initial tibial deformity measured 42.5 degrees, was corrected to 5.6 degrees intraoperatively, and measured 18.6 degrees at follow-up, suggesting recurrent deformity. In follow-up, approximately half of the patients complained of redness and one third complained of a continued prominence along the anterior tibia. Thirty-two extremities had an isolated foot ablation procedure without tibial osteotomy. Radiographic review demonstrated mild tibial bowing at the time of amputation with a mean angular deformity of 15.4 degrees and remained unchanged during the follow-up period (mean, 12.7 degrees). Similar to the osteotomy group, approximately half of the patients complained of redness and erythema over the anterior bow, with one fourth noting prominence, and only 2 reporting significant pain. CONCLUSIONS: Tibial osteotomies in patients with more significant degrees of angular deformity can be safely performed at the same setting as foot ablative procedures for fibular deficiency. Recurrent deformity with growth may occur. Patients and their caregivers should be aware that rebound deformity may occur, but typically can be managed with prosthetic adjustment and without significant disruption to the child's daily activities. LEVEL OF EVIDENCE: Level IV (case series).

Experimental optical encryption of grayscale information.

In this paper, we present a new protocol for achieving lower noise and consequently a higher dynamic range in optical encryption. This protocol allows for the securing and optimal recovery of any arbitrary grayscale images encrypted using an experimental double random phase mask encoding (DPRE) cryptosystem. The protocol takes advantage of recent advances that help reduce the noise due to the correlation of random phase mask in the decryption procedure and introduces the use of a "reference mask" as a reference object used to eliminate the noise due to the complex nature of the masks used in experimental DRPE setups. This noise reduction increases the dynamic range of the decrypted data, retaining the grayscale values to a higher extent and opening new possible applications. We detailed the procedure, and we present the experimental results, including an actual experimental video of a grayscale scene, confirming the validity of our proposal.

The orthotropic elastic properties of fibrolamellar bone tissue in juvenile white-tailed deer femora.

Fibrolamellar bone is a transient primary bone tissue found in fast-growing juvenile mammals, several species of birds and large dinosaurs. Despite the fact that this bone tissue is prevalent in many species, the vast majority of bone structural and mechanical studies are focused on human osteonal bone tissue. Previous research revealed the orthotropic structure of fibrolamellar bone, but only a handful of experiments investigated its elastic properties, mostly in the axial direction. Here we have performed for the first time an extensive biomechanical study to determine the elastic properties of fibrolamellar bone in all three orthogonal directions. We have tested 30 fibrolamellar bone cubes (2 × 2 × 2 mm) from the femora of five juvenile white-tailed deer (Odocoileus virginianus) in compression. Each bone cube was compressed iteratively, within its elastic region, in the axial, transverse and radial directions, and bone stiffness (Young's modulus) was recorded. Next, the cubes were kept for 7 days at 4 °C and then compressed again to test whether bone stiffness had significantly deteriorated. Our results demonstrated that bone tissue in the deer femora has an orthotropic elastic behavior where the highest stiffness was in the axial direction followed by the transverse and the radial directions (21.6 ± 3.3, 17.6 ± 3.0 and 14.9 ± 1.9 Gpa, respectively). Our results also revealed a slight non-significant decrease in bone stiffness after 7 days. Finally, our sample size allowed us to establish that population variance was much bigger in the axial direction than the radial direction, potentially reflecting bone adaptation to the large diversity in loading activity between individuals in the loading direction (axial) compared with the normal (radial) direction. This study confirms that the mechanically well-studied human transverse-isotropic osteonal bone is just one possible functional adaptation of bone tissue and that other vertebrate species use an orthotropic bone tissue structure which is more suitable for their mechanical requirements.

Experimental scrambling and noise reduction applied to the optical encryption of QR codes.

In this contribution, we implement two techniques to reinforce optical encryption, which we restrict in particular to the QR codes, but could be applied in a general encoding situation. To our knowledge, we present the first experimental-positional optical scrambling merged with an optical encryption procedure. The inclusion of an experimental scrambling technique in an optical encryption protocol, in particular dealing with a QR code "container", adds more protection to the encoding proposal. Additionally, a nonlinear normalization technique is applied to reduce the noise over the recovered images besides increasing the security against attacks. The opto-digital techniques employ an interferometric arrangement and a joint transform correlator encrypting architecture. The experimental results demonstrate the capability of the methods to accomplish the task.

Experimental QR code optical encryption: noise-free data recovering.

We report, to our knowledge for the first time, the experimental implementation of a quick response (QR) code as a "container" in an optical encryption system. A joint transform correlator architecture in an interferometric configuration is chosen as the experimental scheme. As the implementation is not possible in a single step, a multiplexing procedure to encrypt the QR code of the original information is applied. Once the QR code is correctly decrypted, the speckle noise present in the recovered QR code is eliminated by a simple digital procedure. Finally, the original information is retrieved completely free of any kind of degradation after reading the QR code. Additionally, we propose and implement a new protocol in which the reception of the encrypted QR code and its decryption, the digital block processing, and the reading of the decrypted QR code are performed employing only one device (smartphone, tablet, or computer). The overall method probes to produce an outcome far more attractive to make the adoption of the technique a plausible option. Experimental results are presented to demonstrate the practicality of the proposed security system.

Optical encryption and QR codes: secure and noise-free information retrieval.

We introduce for the first time the concept of an information "container" before a standard optical encrypting procedure. The "container" selected is a QR code which offers the main advantage of being tolerant to pollutant speckle noise. Besides, the QR code can be read by smartphones, a massively used device. Additionally, QR code includes another secure step to the encrypting benefits the optical methods provide. The QR is generated by means of worldwide free available software. The concept development probes that speckle noise polluting the outcomes of normal optical encrypting procedures can be avoided, then making more attractive the adoption of these techniques. Actual smartphone collected results are shown to validate our proposal.

Optical smart packaging to reduce transmitted information.

We demonstrate a smart image-packaging optical technique that uses what we believe is a new concept to save byte space when transmitting data. The technique supports a large set of images mapped into modulated speckle patterns. Then, they are multiplexed into a single package. This operation results in a substantial decreasing of the final amount of bytes of the package with respect to the amount resulting from the addition of the images without using the method. Besides, there are no requirements on the type of images to be processed. We present results that proof the potentiality of the technique.

Experimental multiplexing of encrypted movies using a JTC architecture.

We present the first experimental technique to encrypt a movie under a joint transform correlator architecture. We also extend the method to multiplex several movies in a single package. We use a Mach-Zehnder interferometer to encrypt experimentally each movie. One arm of the interferometer is the joint transform correlator and the other arm is the reference wave. We include the complete description of the procedure along with experimental results supporting the proposal.

Multiplexing of encrypted data using fractal masks.

In this Letter, we present to the best of our knowledge a new all-optical technique for multiple-image encryption and multiplexing, based on fractal encrypting masks. The optical architecture is a joint transform correlator. The multiplexed encrypted data are stored in a photorefractive crystal. The fractal parameters of the key can be easily tuned to lead to a multiplexing operation without cross talk effects. Experimental results that support the potential of the method are presented.

Master key generation to avoid the use of an external reference wave in an experimental JTC encrypting architecture.

In experimental optodigital encrypting architectures, the use of a reference wave is essential. In this contribution, we present an experimental alternative to avoid the reference wave during the encrypting procedure in a joint transform correlator architecture by introducing the concept of a master key. Besides, the master key represents an additional security element for the entire protocol. In our method, the master key is holographically processed and used during the encryption process with the encrypting key. We give the mathematical description for the process in case of a single input object and then we extend it to multiple input objects. We present the experimental demonstration of the proposed method including two examples where this technique is successfully applied for several input objects.

All-optical encrypted movie.

We introduce for the first time the concept of an all-optical encrypted movie. This movie joints several encrypted frames corresponding to a time evolving situation employing the same encoding mask. Thanks to a multiplexing operation we compact the encrypted movie information into a single package. But the decryption of this single package implies the existence of cross-talk if we do not adequately pre-process the encoded information before multiplexing. In this regard, we introduce a grating modulation to each encoded image, and then we proceed to multiplexing. After appropriate filtering and synchronizing procedures applied to the multiplexing, we are able to decrypt and to reproduce the movie. This movie is only properly decoded when in possession of the right decoding key. The concept development is carried-out in virtual optical systems, both for the encrypting and the filtering-decrypting stages. Experimental results are shown to confirm our approach.

Pure optical dynamical color encryption.

We introduce a way to encrypt-decrypt a color dynamical phenomenon using a pure optical alternative. We split the three basic chromatic channels composing the input, and then each channel is processed through a 4f encoding method and a theta modulation applied to the each encrypted frame in every channel. All frames for a single channel are multiplexed. The same phase mask is used to encode all the information. Unlike the usual procedure we do not multiplex the three chromatic channels into a single encoding media, because we want to decrypt the information in real time. Then, we send to the decoding station the phase mask and the three packages each one containing the multiplexing of a single channel. The end user synchronizes and decodes the information contained in the separate channels. Finally, the decoding information is conveyed together to bring the decoded dynamical color phenomenon in real-time. We present material that supports our concepts.

Noise-free recovery of optodigital encrypted and multiplexed images.

We present a method that allows storing multiple encrypted data using digital holography and a joint transform correlator architecture with a controllable angle reference wave. In this method, the information is multiplexed by using a key and a different reference wave angle for each object. In the recovering process, the use of different reference wave angles prevents noise produced by the nonrecovered objects from being superimposed on the recovered object; moreover, the position of the recovered object in the exit plane can be fully controlled. We present the theoretical analysis and the experimental results that show the potential and applicability of the method.

Known-plaintext attack on a joint transform correlator encrypting system.

We demonstrate in this Letter that a joint transform correlator shows vulnerability to known-plaintext attacks. An unauthorized user, who intercepts both an object and its encrypted version, can obtain the security key code mask. In this contribution, we conduct a hybrid heuristic attack scheme merge to a Gerchberg-Saxton routine to estimate the encrypting key to decode different ciphertexts encrypted with that same key. We also analyze the success of this attack for different pairs of plaintext-ciphertext used to get the encrypting code. We present simulation results for the decrypting procedure to demonstrate the validity of our analysis.

Efficient encrypting procedure using amplitude and phase as independent channels to display decoy objects.

Objects acting as inputs of encrypting optical systems can be regarded as having two independent channels: amplitude and phase. In this context, we can use the term "complex objects" to refer these input objects. In this work we explore the way to perform an undercover operation where one channel (amplitude) is used to depict decoy information to confuse intruders, while the other (phase) operates with the true information. Besides, we use the Gerchberg-Saxton algorithm to transform the amplitude and phase encrypted information into pure phase data, therefore increasing the efficiency of the technique as only a single matrix containing these data needs to be sent. Finally, as an example to show the potential of the method, we combine the separate channels in a multiplexing technique with the Gerchberg-Saxton algorithm to generate an efficient multiuser secure process.

Compensation of Presbyopia With the Light Sword Lens.

Purpose: We present the first physiological evaluation of the use of the light sword lens (LSL) for presbyopia compensation. The LSL is an axially asymmetric optical element designed for imaging with extended depth of focus. Methods: A monocular visual simulator setup is implemented to measure visual acuity (VA). Physiological presbyopia is "mimicked" in human subjects by paralysis of the ciliary muscle, using topical application of a muscarinic antagonist. The effect of a contact lens-configured LSL on the mimicked presbyopia visual system is evaluated by measuring VA as a function of target vergence. The ability of the LSL to compensate presbyopia for 2 photopic luminance values was also analyzed. Results: The average VA values for 11 subjects suggest that the LSL can compensate for presbyopia across a wide range of target vergences for which the LSL was designed (-3 to 0 D). However, the proposed corrector element causes a loss of distance VA. The mean logMAR VA in that target vergence range was 0.07. The VA curves also show that luminance does not affect the expected behavior of the LSL-corrected presbyopic eye. Conclusions: These results indicate that the LSL has significant potential as a visual aid for presbyopia.