Citations

The inverse problem of determining the size, shape and orientation of a submerged object using the scattered field data is studied. Based on the physical optics approximate, the profile function of the object is found directly proportional to its ramp response that is the second integral of the impulse response. Through analyzing the feature of the ramp response in different computed frequency ranges, it is found that the low-frequency data are essential to the shape of the underwater object while the high-frequency data are very important to the size of the object. Therefore, when employing the high-frequency data to compute the ramp response, the edge of the object can only be highlighted in the illuminated region at certain aspect. Based on this finding, a new method is developed to estimate the size of underwater objects. The present method uses different frequency ranges to determine different parameters of the underwater objects so as to achieve the best accuracy. A number of examples are presented to demonstrate the effectiveness of the present method in using the ramp response technique to identify the size of both rigid and elastic bodies.

Bloom's syndrome is a rare autosomal recessive genetic disorder characterized by chromosomal aberrations, genetic instability, and cancer predisposition, all of which may be the result of abnormal signal transduction during DNA damage recognition. Here, we show that BLM is an intermediate responder to stalled DNA replication forks. BLM colocalized and physically interacted with the DNA damage response proteins 53BP1 and H2AX. Although BLM facilitated physical interaction between p53 and 53BP1, 53BP1 was required for efficient accumulation of both BLM and p53 at the sites of stalled replication. The accumulation of BLM/53BP1 foci and the physical interaction between them was independent of γ-H2AX. The active Chk1 kinase was essential for both the accurate focal colocalization of 53BP1 with BLM and the consequent stabilization of BLM. Once the ATR/Chk1- and 53BP1-mediated signal from replicational stress is received, BLM functions in multiple downstream repair processes, thereby fulfilling its role as a caretaker tumor suppressor.

Protein kinase C ι (PKCι) has been implicated in Ras signaling, however, a role for PKCι in oncogenic Ras-mediated transformation has not been established. Here, we show that PKCι is a critical downstream effector of oncogenic Ras in the colonic epithelium. Transgenic mice expressing constitutively active PKCι in the colon are highly susceptible to carcinogen-induced colon carcinogenesis, whereas mice expressing kinase-deficient PKCι (kdPKCι) are resistant to both carcinogen- and oncogenic Ras-mediated carcinogenesis. Expression of kdPKCι in Ras-transformed rat intestinal epithelial cells blocks oncogenic Ras-mediated activation of Rac1, cellular invasion, and anchorage-independent growth. Constitutively active Rac1 (RacV12) restores invasiveness and anchorage-independent growth in Ras-transformed rat intestinal epithelial cells expressing kdPKCι. Our data demonstrate that PKCι is required for oncogenic Ras- and carcinogen-mediated colon carcinogenesis in vivo and define a procarcinogenic signaling axis consisting of Ras, PKCι, and Rac1.

The inflammatory infiltrate in atherosclerotic plaque is composed of T cells and macrophages. CD4 + T cells with a unique phenotype, CD4 + CD28 null , are preferentially recruited into culprit lesions. These T cells are distinct from classic CD4 + CD28 + T cells in gene expression and function, including their ability to mediate cytolysis. In this study, we have investigated the regulation of CD4 + CD28 null T-cell cytolytic function. In patients with acute coronary syndromes (ACS), CD4 + CD28 null T cells express killer immunoglobulin-like receptors (KIRs). KIRs encompass a polymorphic family of receptors that recognize HLA class I molecules and have been implicated in self-tolerance. CD4 + CD28 null T-cell clones from patients with ACS and age-matched controls were compared for their KIR-expression profile. T-cell clones derived from the patients expressed a broader spectrum of KIRs ( P <0.001) with preference for the stimulatory variant, CD158j. Additionally, CD4 + T-cell clones from patients but not those from controls acquired de novo expression of the DAP12 molecule, an adapter chain that transmits CD158j-derived signals. Cumulative expression of CD158j and DAP12 endowed cytolytic competence on CD4 + CD28 null T cells, allowing them to kill in the absence of T-cell receptor triggering. Our data demonstrate that CD4 + CD28 null T cells in ACS are characterized by a unique gene expression profile. Consequently, these T cells acquire cytolytic capability that can bypass the need for T-cell receptor triggering and, thus, impose a threat to self-tolerance.

The inverse problems in the area of the acoustic scattering often concern the determination of the size, shape, and orientation of an object using the scattered field data. This paper presents a method to retrieve the shape information of an underwater object using illuminated lengths, which can be obtained from the ramp response signatures of the object. An ellipsoidal object submerged in water is considered. Both the low and high backscattered frequency data have been employed to calculate the illuminated lengths. The calculated results show that the illuminated lengths will be more accurate, if only the high-frequency-range data are employed. For ellipsoidal objects, any three illuminated lengths that are not of a same plane can in theory fully determine the shape of the ellipsoid. As the calculated illuminated lengths contain numerical errors, the calculated results of the three semiaxes of the ellipsoid will deteriorate and become unreliable, especially when the three incident directions of the illuminated lengths become close. The reason is that the condition number of the coefficient matrix becomes big in such situations, which leads to an increase of the relative error upper limit in the calculated results. To avoid such errors in close incident wave cases, it is found that the use of more than three incident waves works very well in the shape identification of an underwater object.

Coupled vibration of arterial tubes is analyzed with the wave propagation approach and first-order shear deformation theory. Both the interior and exterior fluids are considered as compressible so that acoustic waves can be generated and propagated in the fluids. Results obtained using the theory have been evaluated against those available in the literature and the agreement has been found to be good. The theory can be used for future research on the vibration and acoustics of arterial walls. Vibration experiments were carried out on a silicone rubber tube in a water tank with a novel ultrasound stimulated optical vibrometry system. This system uses the radiation force of ultrasound to vibrate the tube at low frequency and records the resulting response by a laser vibrometer. Both the excitation and measurement are remote and noncontact. The silicone rubber tube was chosen because it has mechanical properties close to those of arteries. The fundamental frequency is well excited by the radiation force and measured with the laser. The measured fundamental frequency is in good agreement with the present theory.