Buckling-induced transmission switching in phononic waveguidesa).

On-chip phononic circuits tailor the transmission of elastic waves and couple to electronics and photonics to enable new signal manipulation capabilities. Phononic circuits rely on waveguides that transmit elastic waves within desired frequency passbands, which are typically designed based on the Bloch modes of the constitutive unit cell of the waveguide, assuming periodicity. Acoustic microelectromechanical system waveguides composed of coupled drumhead resonators offer megahertz operation frequencies for applications in acoustic switching. Here, we construct a reduced-order model (ROM) to demonstrate the mechanism of transmission switching in coupled drumhead-resonator waveguides. The ROM considers the mechanics of buckling under the effect of temperature variation. Each unit cell has two degrees of freedom: translation to capture the symmetric bending modes and angular motion to capture the asymmetric bending modes of the membranes. We show that thermoelastic buckling induces a phase transition triggered by temperature variation, causing the localization of the first-passband modes, similar to Anderson localization caused by disorders. The proposed ROM is essential to understanding these phenomena since Bloch mode analysis fails for weakly disordered (<5%) finite waveguides due to the disorder amplification caused by the thermoelastic buckling. The illustrated transmission control can be extended to two-dimensional circuits in the future.

Middle meningeal artery embolisation: The review of a new treatment for chronic subdural hematomas.

Background: This is a literature review aiming to provide an update about the recent findings related to the efficacy of middle meningeal artery embolization (MMAE) in the treatment of chronic subdural hematomas (cSDHs), comparison with conventional therapy and deduction of the current recommendations and indications. Methods: The literature is reviewed using a search through the PubMed index using keywords. Studies are then screened, skimmed, and thoroughly read. 32 studies fulfilled the inclusion criteria and are included in the study. Results: Five indications for the application of MMA embolization (MMAE) are deducted from the literature. The usage as a preventive measure after surgical treatment of symptomatic cSDHs in patients with a high risk of recurrence and the usage as a standalone procedure has been the most common reasons for indication of this procedure. Rates of failures for the aforementioned indications have been 6.8% and 3.8%, respectively. Conclusion: The safety of MMAE as a procedure is regarded as a general theme in the literature and can be considered for future applications. Usage of this procedure in clinical trials with more patient segregation and timeframe assessment relative to surgical intervention are recommendations of this literature review.

Predictive value of PSA density in the diagnosis of prostate cancer in lebanese men.

OBJECTIVE: Being the second most common cancer in men, prostate cancer detection relies on laboratory tests, imaging, and surgical procedures, although biopsy remains the mainstay in diagnosis of prostate cancer. No clear cut-off of prostate specific antigen density (PSAD) for suspecting prostate cancer has been established in the Lebanese population. Our primary objective was to evaluate the diagnostic strength of the PSAD value versus total prostate specific antigen (tPSA) level in the Lebanese men in correlation with biopsy outcome to avoid unnecessary prostate biopsy. METHODS: A retrospective study of 347 patients with history of prostate biopsy done for cancer suspicion included tPSA, prostate volume, and prostate density values and results of prostate biopsy. Data was collected from Bahman hospital and statistical analysis of the mean values of tPSA, prostate volume and PSAD in different age groups was done. Significance of the results was tested using. RESULTS: On average, patients with negative biopsies were younger and they had lower tPSA levels, lower PSAD values and larger prostate volume compared to patients with positive biopsies. A PSAD cutoff of 0.185 ng/ml2 revealed the highest predictive strength for prostate cancer (6 times risk) compared with other parameters. These findings were mainly referred to patients with PSA > 10 ng/ml. CONCLUSIONS: A multifactorial approach must be conducted including all parameters in order to decide upon the need for prostate biopsy. PSAD proved to be a good marker in favor or against a prostate biopsy with a cut-off of 0.185 ng/ml2, especially in patients with tPSA level higher to 10 ng/ml. A multicenter study was recommended for better and more reliable results and more precise cut-offs.

From Spot Sign to Bleeding on the Spot: Classic and Original Signs of Expanding Primary Spontaneous Intracerebral Hematoma.

Expansion of a primary spontaneous intracranial hemorrhage (PSICH) has become lately of increasing interest, especially after the emergence of its early predictors. However, these signs lacked sensitivity and specificity. The flood phenomenon, defined as a drastic increase in the size of a PSICH during the same magnetic resonance study, was first described in this paper based on the data of a university medical center in Lebanon. Moreover, further review of this data resulted in 205 studies with presumed diagnosis of primary spontaneous intracranial hemorrhage within the last 10 years, of which 29 exams showed typical predictors of hematoma expansion on computed tomography. The intended benefit of this observation is to draw the radiologists' attention towards minimal variations in the volume of the hematoma between the two extreme sequences of the same MRI study, in order to detect inconspicuous flood phenomena-a direct sign of hematoma expansion.

Buckling-Mediated Phase Transitions in Nano-Electromechanical Phononic Waveguides.

Waveguides for mechanical signal transmission in the megahertz to gigahertz regimes enable on-chip phononic circuitry, which brings new capabilities complementing photonics and electronics. Lattices of coupled nano-electromechanical drumhead resonators are suitable for these waveguides due to their high Q-factor and precisely engineered band structure. Here, we show that thermally induced elastic buckling of such resonators causes a phase transition in the waveguide leading to reversible control of signal transmission. Specifically, when cooled, the lowest-frequency transmission band associated with the primary acoustic mode vanishes. Experiments show the merging of the lower and upper band gaps, such that signals remain localized at the excitation boundary. Numerical simulations show that the temperature-induced destruction of the pass band is a result of inhomogeneous elastic buckling, which disturbs the waveguide's periodicity and suppresses the wave propagation. Mechanical phase transitions in waveguides open opportunities for drastic phononic band reconfiguration in on-chip circuitry and computing.

What Radiologist Should Know about MRI Translational Forces and Hazard: An Ex-Vivo Simulation of Retained Metallic Shrapnel.

BACKGROUND: In a country immersed in endless rounds of wars, retained metallic foreign bodies remain a significant dilemma in the daily practice of every Lebanese radiologist. When a shrapnel's hazard is of concern, the decision between performing or refusing a justified MRI exam is not always straightforward. In this small trial, we aimed to better understand the shrapnel's MRI safety by mimicking our daily practice. METHODS: Five shrapnel with an incremental increase in their long axis were put in an animal flesh and then introduced into a 3 T magnetic field. The behavior of each shrapnel was concretely assessed by performing before and after magnetic field exposure CT acquisitions. RESULTS: Translation along the z-axis ranged from 0.9 mm to 2.8 mm. Torque angle ranged between 2.8 and 54 degrees with an average of 15.62 degrees. CONCLUSIONS: Shrapnel's movements in the magnetic field are not negligible during the acute phase of injury where there is no reinforcing fibroblastic reaction and invite us to reconsider the MRI safety of these metallic foreign bodies. Standard radiographs may be sufficient, but a targeted CT scan may be of better value for a confident decision for assessment of shrapnel position near viscera and major vessels.

Palbociclib safety and efficacy beyond Ribociclib-induced liver toxicity in metastatic hormone-receptors positive breast cancer patient.

CDK4/6 inhibitors in association with aromatase inhibitors have led to a paradigm shift in the management of metastatic positive hormone-receptors breast cancer. Liver toxicity is common with these agents, but no data are reported on the sequential use of these CDK4/6 inhibitors in case of confirmed efficacy and intolerable toxicity. In this article, we report the successful use of Palbociclib in a metastatic positive hormone-receptors breast cancer patient after initial response to Ribociclib, which was interrupted for grade 4 liver toxicity.

Lymphoepithelioma-Like Carcinoma of the Breast: A Case Report Unveiling Several Clinical and Histopathological Challenges.

Lymphoepithelioma-like carcinoma (LELC) of the breast is an extremely rare tumor type. Histologically, it mimics undifferentiated nasopharyngeal carcinoma by demonstrating nests of neoplastic epithelial cells in a background of lymphoplasmacytic infiltrates. This paper reports a 62-year-old female patient with a 3 × 1.5 cm BI-RADS type IV breast mass diagnosed on excisional biopsy as LELC. The tumor is negative for estrogen and progesterone receptors and did not overexpress HER2/neu. Routine tests for clearance before surgery were performed, and patient was managed by a modified radical mastectomy with axillary lymph node dissection showing no residual tumor. Surgical CAse REports (SCARE) guidelines were followed for reporting our case. The rarity of LELC of the breast warrants the establishment and implementation of well-defined guidelines and criteria for diagnosis and management.

Unusual appearance of a cerebral hydatid cyst as a hemorrhagic infarct.

We herein present a 32-year-old Lebanese woman with a history of cardiac hydatid cyst presenting with headache, confusion, and right arm clumsiness. A CT of the head showed hemorrhagic infarct of the left fronto-parietal lobe. Eleven months later, the subsequent development of hydatid cysts within the necrotic area of the infracted hemisphere suggested a cerebral hydatid embolism of cardiac origin. In patients with a positive history of hydatid disease, hydatid embolism should be considered in the differential diagnosis of stroke in young patients.

Multicentric glioma: problems & interpretations. [corrected].

The authors report four patients suffering from multicentric intraparenchymatous malignant glioma lesions located in different regions of the brain. The incidence of multiple, separated, independent, non-connected neuroepithelial tumors in the same patient is rare, although a discrepancy exists in the literature with regard to its real incidence. There is also controversy with respect to the histological composition of these tumors. In some cases, identical histopathological composition has been found, while in others different cellular patterns are present. Several hypotheses have been put forward to try to explain the occurrence of multicentric glioma tumor in the same patient. They consist of disseminations (through white matter tracts, cerebrospinal fluid pathways, or metastatic satellites around the vicinity of the tumor) or simultaneous development of different tumors, independent from each other.