Chemical modification of group IV graphene analogs

Mono-elemental two-dimensional (2D) crystals (graphene, silicene, germanene, stanene, and so on), termed 2D-Xenes, have been brought to the forefront of scientific research. The stability and electronic properties of 2D-Xenes are main challenges in developing practical devices. Therefore, in this review, we focus on 2D free-standing group-IV graphene analogs (graphene quantum dots, silicane, and germanane) and the functionalization of these sheets with organic moieties, which could be handled under ambient conditions. We highlight the present results and future opportunities, functions and applications, and novel device concepts.     

Image-analysis-based assessment of the effects of the "Ca2+-jump" technique on sarcomere uniformity

A new image analysis-based technique was used to quantitatively examine the effects of the "Ca2+-jump" activation protocol on the maintenance of fiber quality in skinned rabbit psoas muscle fiber segments. Specifically, contractions in pCa 4.6 were preceded by short-duration "preactivation" soaks in a solution in which EGTA was replaced with the low-Ca2+ buffering capacity analog hexamethylenediamine-N, N, N', N'-tetraacetate, which facilitated rapid Ca2+ equilibration within the fiber segments. Fiber quality was assessed by examining the Fourier spectra of the muscle fiber images before, during, and after activation. Segment lengths were typically below 500 micrometer, thus allowing the majority of the sarcomeres to be visualized in the field of view (x200 and x400 magnification). The preactivation protocol resulted in less deterioration of fiber quality with repetitive activation. In addition, there was also a significant reduction in the time required to reach the 50% level of maximum tension, with no significant change in the maximum tension level.     

The effect of cold cardioplegic cardiac arrest and electrically induced ventricular fibrillation on human cardiac beta-adrenoceptors during open-heart surgery

This study was designed to test the hypothesis that distinct alterations in cardiac beta-adrenoceptors (betaARs) may occur during cardiopulmonary bypass (CPB) alone, during CPB with cold cardioplegic cardiac arrest (CCCA), and during CPB with electrically induced ventricular fibrillation (EIVF). We assessed the density and affinity of right atrial betaARs in 27 patients undergoing open-heart surgery by (-)-[125I]iodocyanopindolol binding before CPB, defined as the "control," immediately after initiation, defined as "before," and immediately before the cessation of CCCA or EIVF, defined as "after." The density of betaARs was equivalent between the "control" and "before" groups; however, during CPB with EIVF, the density of betaARs decreased significantly (P < 0.001), whereas during CPB with CCCA, it increased significantly (P < 0.01). The rate of changes of the betaAR density was not correlated with the "before"-"after" interval, and the affinity of the betaARs did not change throughout these CPBs. These findings demonstrate that: CPB alone does not affect cardiac betaARs, at least until the onset of EIVF or CCCA; CPB with EIVF induces rapid desensitization of cardiac betaARs; and CPB with CCCA induces rapid sensitization of cardiac betaARs.     

Ultra light-weight and high-resolution X-ray mirrors using DRIE and X-ray LIGA techniques for space X-ray telescopes

We are developing novel ultra light-weight and high-resolution X-ray micro pore optics for space X-ray telescopes. In our method, curvilinear micro pore structures are firstly fabricated by silicon deep reactive ion etching (DRIE) or X-ray LIGA processes. Secondly, side walls of the micro structures are smoothed by magnetic field assisted finishing and/or hydrogen annealing techniques for high reflectivity mirrors. Thirdly, to focus parallel X-ray lights from astronomical objects, these structures are elastically or plastically bent into a spherical shape. Fourthly, the bent structures are stacked to form a multi-stage X-ray telescope. In this paper, we report on fabrication and X-ray reflection tests of silicon and nickel X-ray mirrors using the DRIE and LIGA processes, respectively. For the first time, X-ray reflections were confirmed on both of the mirrors. Estimated rms roughnesses were 5 nm and 3 nm for the silicon and nickel mirrors, respectively.     

Heat Capacity of Dilute 3He–4He Films on Graphite

The heat capacity of dilute ³He–⁴He films is measured to clarify whether the second adsorbed layer of ⁴He films on graphite solidify into the so-called “4/7 phase.” The ³He areal density is fixed at 0.2 nm^?2, whereas the ⁴He areal density is gradually increased. The measured heat capacities suddenly decrease with an increasing areal density approaching that of the 4/7 phase. Above the areal density of the 4/7 phase, the heat capacities do not reduce completely to zero and have finite values. The behavior of the heat capacity does not change over a rather wide areal density regime, although it suddenly increases or recovers at around the areal density of the third-layer promotion. These behaviors can be interpreted as the separation of ³He–⁴He mixture films into a ³He-rich phase and a ⁴He-rich phase, with the ³He-rich phase solidifying into the 4/7 phase and the ⁴He-rich phase remaining fluid below the areal density of the third-layer promotion. These observations strongly suggest that a ⁴He film adsorbed on a graphite surface does not solidify into the 4/7 phase.     

Improved electrochemical activity of LiMnPO4 by high-energy ball-milling

Olivine lithium manganese phosphate (LiMnPO₄) becomes research focus because of its high energy density and improved thermal stability. However, its application in lithium ion batteries suffers severely from poor electrochemical activity due to low conductivity and structural instability upon the charge and discharge process. By applying a high-energy ball-milling method we succeed in improving the capacity delivery and rate capability. LiMnPO₄ materials ball-milled without or with acetylene black are able to deliver a high capacity of 135 and 127 mAh g⁻¹, respectively, more than 50% greater than the pristine one. Particularly, the latter also shows an improved discharge plateau and stable cyclability. High-energy synchrotron radiation X-ray diffraction (XRD), scanning electron microscopy (SEM), Raman spectroscopy, laser particle analysis, and galvanostatic charge and discharge are employed to understand the effect of ball-milling on the LiMnPO₄ material.     

Potential role of hepatocyte growth factor in the maintenance of renal structure: anti-apoptotic action of HGF on epithelial cells

BACKGROUND: Mesangial cells (MC) are known to secrete various vasoactive substances that may control endothelial and epithelial cell growth. Therefore, the cell-cell interactions among these cells may be important in the control of renal function. However, the exact mechanisms of maintaining the cell-cell interactions are not yet understood. We have focused on the role of hepatocyte growth factor (HGF) in the regulation of cell-cell interactions, since HGF has many protective functions in the kidney. To investigate the role of HGF in renal injury, we examined (1) the effects of HGF on epithelial injury induced by serum deprivation, and (2) the role of local HGF production in the maintenance of renal structure. METHODS: Apoptotic changes in epithelial cells were assessed by nuclear morphology and DNA fragmentation assay. Transfection of human HGF vector into epithelial cells was performed by a highly efficient viral-liposome method. The effects of secreted HGF on the growth of renal cells were examined using a co-culture system. RESULTS: The addition of recombinant HGF (rHGF) stimulated the growth of rat and porcine epithelial cells. Moreover, the decrease in number of epithelial cells by serum deprivation was significantly attenuated by rHGF. Interestingly, apoptotic changes in epithelial cells induced by serum deprivation were also significantly attenuated by rHGF (P < 0.01). As a model of gene therapy, the effects of overexpression of human HGF gene in epithelial cells on apoptosis induced by serum deprivation were examined. Transfection of human HGF vector into epithelial cells also attenuated epithelial cell death induced by serum deprivation through the inhibition of apoptosis, accompanied by increased HGF production (P < 0.01). In addition, HGF also prevented endothelial injury induced by tumor necrosis factor-alpha and dexamethasone. Given the presence of a local HGF system, we measured local HGF secreted from renal cells. Immunoreactive HGF was observed in the conditioned medium of MC, but not epithelial cells, while the specific receptor of HGF, c-met, was expressed in epithelial cells. Of importance, co-culture of MC with epithelial cells resulted in a significant increase in number of epithelial cells, which was significantly abolished by neutralizing anti-HGF antibody. CONCLUSIONS: Overall, these results demonstrate that local production of HGF in MC may maintain the growth of epithelial and endothelial cells through its anti-apoptotic action.     

New predictive formulas of pulmonary function in Japanese children

Socioeconomic conditions, including nutrition, have improved dramatically over the past four decades in Japan. Those improvements have elicited significant changes in the developmental growth and average size of Japanese children. These trends suggest that predictive formulas of pulmonary function need to be revised. Our study enrolled 446 children (222 boys and 224 girls ranging in age from 5 to 16 years) who had no history of respiratory disease. The subjects were examined by spirometry. We formulated regression equations for several measures of ventilatory function by age, weight, and height, including vital capacity (VC), forced vital capacity (FVC), and forced expiratory volume in one second (FEV1.0), using data randomly selected from 70% of the children. Optimum parameters for the equations were selected by calculating Akaike information criteria (AIC) and Mallow's index C (p). The optimum regression equations were tested for their predictive value as acceptable predictive formulas by evaluating data randomly selected from 30% of the children. These new formulas are considered to be better suited for modern-day evaluations of pulmonary function in Japanese children.     

Inhibition of intimal hyperplasia after vein grafting by in vivo transfer of human senescent cell-derived inhibitor-1 gene

OBJECTIVE: To define the distribution and determinants of cardiovascular disease events among participants undergoing long-term antihypertensive therapy, and to stratify them into risk groups on the basis of pretreatment clinical profiles. DESIGN: A prospective cohort study of participants in a worksite-based antihypertensive treatment program in New York city (1973-1994). PATIENTS: We studied 8690 systematically treated patients who had at least 6 months of follow-up (average of 5.7 years) and, at entry, had had a systolic blood pressure of > or = 160 mmHg or a diastolic blood pressure of > or = 95 mmHg (after 1992 > or = 140/90 mmHg), or had been being administered antihypertensive medication. MAIN OUTCOME MEASURES: Blood pressure and incidence of morbid and mortal cardiovascular events. RESULTS: Blood pressure control (to 140 +/- 3/87 +/- 7 mmHg) was achieved by the first year and maintained through 18 years of therapy. In nearly 50,000 person-years of follow-up, there were 468 cardiovascular disease events [myocardial infarction including revascularization (282), strokes (93), congestive heart failure (30) and other cardiovascular deaths (63)]. Deaths from cardiovascular disease events accounted for 68% of all deaths. Myocardial infarction was most common throughout, but congestive heart failure incidence surpassed stroke incidence after 10 years. A scheme for risk stratification was constructed after analysis of the independent association of baseline factors and incident cardiovascular events. Upon the basis of ease of ascertainment and their demonstrated associations with occurrence of cardiovascular disease during treatment, we selected five pretreatment factors (history of heart attack, stroke, diabetes, age > or = 55 years and pulse pressure > or = 60 mmHg) to stratify patients into four groups. Those with no risk factor had a low risk (n=2999), those with one had a moderate risk (3042), those with two had a high risk (2237), and those with three or more had a very high risk (412). Overall, the unadjusted rates of incidence of cardiovascular disease events per 1000 person-years for patients in very high and low risk groups differed by factors of six and 14 for men and women, respectively. CONCLUSION: These results demonstrate that long-term control of blood pressure can be achieved in a general population. Nevertheless, cardiovascular disease events still accounted for most morbidity and mortality among these 'recovered' hypertensive patients. At entry, on the basis of readily identifiable characteristics, it was possible to stratify patients according to likelihood of subsequent events occurring despite control of blood pressure. This scheme could provide the basis for targeting more aggressive therapy where the potential for further cardioprotection is greatest.