Dynamic study of the finger interphalangeal joint volar plate-motion analysis with magnetic resonance cinematography and histologic comparison.

OBJECTIVE: We aimed to further improve knowledge about volar plate (VP) motion of the finger proximal interphalangeal joint (PIP), by analyzing the dynamic VP shape during a full range of finger flexion using magnetic resonance cinematography of the fingers (MRCF), and to compare the results with anatomical cross sections from cadaver specimens. MATERIALS AND METHODS: The dynamic sagittal VP shape was visualized with MRCF in a total number of 23 healthy volunteers. The length, angle, and thickness as well as the contact length of the VP to the PIP joint base were measured. Statistical analysis included t-test or rank-sum testing. Anatomical cross sections with differing degrees of PIP joint flexion were obtained from 12 cadaver specimens (fingers) for comparison. RESULTS: Significant positive correlations between PIP joint flexion angle and VP area, length, depth and the VP contact length were found. This matched histologically to fiber rearrangements especially within the loose third VP layer. CONCLUSION: Our study analyzed the full range of motion dynamic VP shape of the PIP joint using MRCF. This contributes to a more precise understanding of the complex interaction of the VP with the PIP joint and may facilitate evaluation of clinical cases such as VP avulsion or pulley rupture.

Thermomolecular orientation of nonpolar fluids.

We investigate the response of molecular fluids to temperature gradients. Using nonequilibrium molecular dynamics computer simulations we show that nonpolar diatomic fluids adopt a preferred orientation as a response to a temperature gradient. We find that the magnitude of this thermomolecular orientation effect is proportional to the strength of the temperature gradient and the degree of molecular anisotropy, as defined by the different size or mass of the molecular atomic sites. We show that the preferred orientation of the molecules follows the same trends observed in the Soret effect of binary mixtures. We argue this is a general effect that should be observed in a wide range of length scales.

Nonequilibrium molecular dynamics simulations of the thermal conductivity of water: a systematic investigation of the SPC/E and TIP4P/2005 models.

We report an extensive nonequilibrium molecular dynamics investigation of the thermal conductivity of water using two of the most accurate rigid nonpolarizable empirical models available, SPC/E and TIP4P/2005. Our study covers liquid and supercritical states. Both models predict the anomalous increase of the thermal conductivity with temperature and the thermal conductivity maximum, hence confirming their ability to reproduce the complex anomalous behaviour of water. The performance of the models strongly depends on the thermodynamic state investigated, and best agreement with experiment is obtained for states close to the liquid coexistence line and at high densities and temperatures. Considering the simplicity of these two models the overall agreement with experiments is remarkable. Our results show that explicit polarizability and molecular flexibility are not needed to reproduce the anomalous heat conduction of water.

Water under temperature gradients: polarization effects and microscopic mechanisms of heat transfer.

We report non-equilibrium molecular dynamics simulations (NEMD) of water under temperature gradients using a modified version of the central force model (MCFM). This model is very accurate in predicting the equation of state of water for a wide range of pressures and temperatures. We investigate the polarization response of water to thermal gradients, an effect that has been recently predicted using Non-Equilibrium Thermodynamics (NET) theory and computer simulations, as a function of the thermal gradient strength. We find that the polarization of the liquid varies linearly with the gradient strength, which indicates that the ratio of phenomenological coefficients regulating the coupling between the polarization response and the heat flux is independent of the gradient strength investigated. This notion supports the NET theoretical predictions. The coupling effect leading to the liquid polarization is fairly strong, leading to polarization fields of ~10(3-6) V m(-1) for gradients of ~10(5-8) K m(-1), hence confirming earlier estimates. Finally we employ our NEMD approach to investigate the microscopic mechanism of heat transfer in water. The image emerging from the computation and analysis of the internal energy fluxes is that the transfer of energy is dominated by intermolecular interactions. For the MCFM model, we find that the contribution from hydrogen and oxygen is different, with the hydrogen contribution being larger than that of oxygen.

Lumbrical muscle tear: clinical presentation, imaging findings and outcome.

The incidence of lumbrical muscle tear is increasing due to the popularity of climbing sport. We reviewed data from 60 consecutive patients with a positive lumbrical stress test, including clinical examination, ultrasound and clinical outcomes in all patients, and magnetic resonance imaging in 12 patients. Fifty-seven patients were climbers. Lumbrical muscle tears were graded according to the severity of clinical and imaging findings as Grade I-III injuries. Eighteen patients had Grade I injuries (microtrauma), 32 had Grade II injuries (muscle fibre disruption) and 10 had Grade III injuries (musculotendinous disruption). The treatment consisted of adapted functional therapy. All patients completely recovered and were able to return to climbing. The healing period in Grade III injuries was significantly longer than in the patients with Grade I or II injuries ( p < 0.001). We recommend evaluation of specific clinical and imaging findings to grade the injuries and to determine suitable therapy. LEVEL OF EVIDENCE: IV.

Alkali halide solutions under thermal gradients: soret coefficients and heat transfer mechanisms.

We report an extensive analysis of the non-equilibrium response of alkali halide aqueous solutions (Na(+)/K(+)-Cl(-)) to thermal gradients using state of the art non-equilibrium molecular dynamics simulations and thermal diffusion forced Rayleigh scattering experiments. The coupling between the thermal gradient and the resulting ionic salt mass flux is quantified through the Soret coefficient. We find the Soret coefficient is of the order of 10(-3) K(-1) for a wide range of concentrations. These relatively simple solutions feature a very rich behavior. The Soret coefficient decreases with concentration at high temperatures (higher than T ∼ 315 K), whereas it increases at lower temperatures. In agreement with previous experiments, we find evidence for sign inversion in the Soret coefficient of NaCl and KCl solutions. We use an atomistic non-equilibrium molecular dynamics approach to compute the Soret coefficients in a wide range of conditions and to attain further microscopic insight on the heat transport mechanism and the behavior of the Soret coefficient in aqueous solutions. The models employed in this work reproduce the magnitude of the Soret coefficient, and the general dependence of this coefficient with temperature and salt concentration. We use the computer simulations as a microscopic approach to establish a correlation between the sign and magnitude of the Soret coefficients and ionic solvation and hydrogen bond structure of the solutions. Finally, we report an analysis of heat transport in ionic solution by quantifying the solution thermal conductivity as a function of concentration. The simulations accurately reproduce the decrease of the thermal conductivity with increasing salt concentration that is observed in experiments. An explanation of this behavior is provided.

Uncommon lesions in the internal auditory canal (IAC): review of the literature and case report.

BACKGROUND: Despite the relatively frequent occurrence of multiple primary tumors, namely, 10% of intracranial tumors, metastasis is a rare occurrence within the internal auditory canal (IAC) and cerebellopontine angle (CPA). Intracanalicular metastases of adenocarcinoma are documented, but a primary adenocarcinoma remains unreported. We provide a review of uncommon lesions in the IAC and describe to our knowledge the first instance of a primary adenocarcinoma. CASE REPORT: A 60-year-old man presented with nausea and vomiting. Cranial computed tomography scan revealed bilateral nonspecific periventricular and subcortical vascular lesions. He presented 8 months later with left-sided tinnitus, progressive hearing loss, and attacks of vertigo. Magnetic resonance imaging (MRI) showed an extra-axial mass most likely representing a left-sided vestibular schwannoma with characteristic contrast enhancement in the IAC. The follow-up MRI showed an unchanged pattern of contrast enhancement. Due to progressive headaches and dizziness, the patient underwent a left transtemporal craniotomy with subtotal tumor resection. Histological examination revealed blennogenic cylindrical adenocarcinoma. The investigations for the primary tumor site were all negative. The patient's condition deteriorated gradually. MRI showed an increase of the residual tumor and meningeosis carcinomatosa, and cerebrospinal fluid (CSF) examination was positive for tumor cells. The patient was treated with intrathecal chemotherapy. He died of multiple organ failure. DISCUSSION: The discussion focuses on the incidence of extra-axial CPA and IAC lesions with their clinical presentations and their radiological findings. We address the issue of a possible regulation of CPA lesion laterality by asymmetrically expressed genes. In view of the sparse literature on treatment of single intracanalicular metastases, the review is broadened to the current treatment recommendations of single brain metastases. CONCLUSIONS: The differentiation between benign and malign lesions in the CPA and IAC is important, as it requires diverse treatment protocols. For the physician this differentiation represents a clinical and radiological challenge. For the developmental research the left-right asymmetry might be a field of research.