Applying reticular synthesis to the design of Cu-based MOFs with mechanically interlocked linkers

The concept of“robust dynamics”describes the incorporation of mechanically interlocked molecules(MIMs)into metal-organic framework(MOF)materials such that large amplitude motions(e.g.,rotation or translation of a macrocycle)can occur inside the free volume pore of the MOF.To aid in the preparation of such materials,reticular synthesis was used herein to design rigid molecular building blocks with predetermined ordered structures starting from the well-known MOF NOTT-101.New linkers were synthesized that have a T-shape,based on a triphenylene tetra-carboxylate strut,and their incorporation into Cu(II)-based MOFs was investigated.The single-crystal structures of three new MOFs,UWCM-12(fof),β-UWCM-13(loz),UWCM-14(lil),with naked T-shaped linkers were determined;β-UWCM-13 is the first reported example of the loz topology.A fourth MOF,UWDM-14(lil)is analogous to UWCM-14(lil)but contains a[2]rotaxane linker.Variable-temperature,²H solid-state NMR was used to probe the dynamics of a 24-membered macrocycle threaded onto the MOF skeleton.     

硬件锁中的无线USB

无线USB的前途似乎无与伦比——它能消除那些把大家桌面弄得像鼠窝一样小小的不怎么灵便的电缆。但事实上,只有需要大量的外设时无线USB设备才有优势,而且它必须非常微型而廉价,否则带来的麻烦远多于缠绕的电缆。因此,插在PC USB端口作为无线基站的硬件锁就必须有尽可能高的集成度。但一片芯片中要包含USB有线接口、控制器、无线基带和RF电路,技术上还无法实现。下面我们将看到一家供应商Wisalr的一种可量产参考设计,它是如何接近于解决这个问题的。     

Magnetic effects of direct ion implantation of Mn and Fe into p-GaN

In p-GaN implanted with Mn (3×10¹⁶ cm⁻² at 250 keV), the material after annealing shows ferromagnetic properties below 250 K. Cross-sectional transmission electron microscopy (TEM) revealed the presence of platelet structures with hexagonal symmetry. These regions are most likely Ga_xMn_1−xN, which produce the ferromagnetic contribution to the magnetization. In p-GaN implanted with Fe, the material after annealing showed ferromagnetic properties at temperatures that were dependent on the Fe dose, but were below 200 K in all cases. In these samples, TEM and diffraction analysis did not reveal any secondary phase formation. The results for the Fe implantation are similar to those reported for Fe doping during epitaxial growth of GaN.     

Transjugular intrahepatic portosystemic shunts (TIPS) in children

The transjugular intrahepatic portosystemic shunt procedure is an accepted treatment for adults with complications of portal hypertension. We performed a retrospective review of all pediatric TIPS placements performed at the University of California, San Francisco between 1990 and 1996. Twelve procedures were attempted in nine children, with a mean age (+/- SD) of 9.4 +/- 3.9 years (range, 5 to 15 years) and a mean weight of 31 +/- 18 kg (range, 16 to 70 kg). The indications for TIPS placement were portal hypertension complicated by chronic variceal hemorrhage not controlled with sclerotherapy (n = 7) and hypersplenism with thrombocytopenia (n = 2). TIPS placement was successfully completed initially in seven of nine (78%) patients. Unfavorable vascular anatomy was the cause of failure in two cases. The seven patients who underwent successful TIPS placement were followed up for an average of 136 days (range, 1 to 800 days); two still have patent shunts, three underwent liver transplantation, one had a splenorenal shunt after stenosis, and one died of underlying liver disease. Variceal bleeding was controlled in four of five patients who successfully underwent TIPS placement. Shunt occlusion occurred in four patients; patency was restored by transjugular shunt revision in three, and a splenorenal shunt was performed in one.     

Viral dynamics of primary viremia and antiretroviral therapy in simian immunodeficiency virus infection

Mathematical modeling of viral replication dynamics, based on sequential measurements of levels of virion-associated RNA in plasma during antiretroviral treatment, has led to fundamental new insights into human immunodeficiency virus type 1 pathogenesis. We took advantage of the simian immunodeficiency virus (SIV)-infected macaque model to perform detailed measurements and mathematical modeling during primary infection and during treatment of established infection with the antiretroviral drug (R)-9-(2-phosphonylmethoxypropyl)adenine (PMPA). The calculated clearance half-life for productively infected cells during resolution of the peak viremia of primary infection was on the order of 1 day, with slightly shorter clearance half-lives calculated during PMPA treatment. Viral reproduction rates upon discontinuation of PMPA treatment after 2 weeks were approximately twofold greater than those obtained just prior to initiation of treatment in the same animals, likely reflecting accumulation of susceptible target cells during treatment. The basic reproductive ratio (R0) for the spread of SIV infection in vivo, which represents the number of productively infected cells derived from each productively infected cell at the beginning of infection, was also estimated. This parameter quantifies the extent to which antiviral therapy or vaccination must limit the initial spread of virus to prevent establishment of chronic disseminated infection. The results thus provide an important guide for efforts to develop vaccines against SIV and, by extension, human immunodeficiency virus.     

Temporary leukocyte depletion reduces ventricular dysfunction during prolonged postischemic reperfusion

Leukocyte depletion improves early postischemic ventricular performance in neonatal models of global myocardial ischemia. However, the rate of leukocyte reaccumulation after cardiopulmonary bypass and its subsequent impact on myocardial function is not known. This laboratory study examined the effect of leukocyte depletion on myocardial performance during the initial 6-hour period after bypass in an in situ, in vivo porcine model of neonatal cardiac surgery. Fifteen 3- to 5-day-old piglets (eight control and seven leukocyte depleted animals) were instrumented by placement of left ventricular short-axis sonomicrometry crystals and an intraventricular micromanometer catheter. Mechanical leukocyte depletion was achieved with Pall RC100 filters (Pall Biomedical, Inc., Fajardo, Puerto Rico) in the cardiopulmonary bypass circuit. Neonatal hearts were subjected to 90 minutes of hypothermic ischemia after a single dose of cold crystalloid cardioplegia. Two control animals died after the operation and were excluded from data analysis. Leukocyte filtration reduced the granulocyte count during initial myocardial reperfusion to 0.8% of control values. However, circulating granulocyte counts increased in leukocyte depleted animals throughout the postoperative period, reaching 68% of control values by 6 hours. Despite this rapid return of circulating granulocytes, animals subjected to leukocyte depletion had significantly better preservation of left ventricular performance (measured by preload recruitable stroke work, p < or = 0.02), left ventricular systolic function (measured by end-systolic pressure-volume relationship, p < or = 0.05), and ventricular compliance (p < or = 0.04) during the experiment. These changes in ventricular function were associated with a significant increase in left ventricular water content (p < or = 0.02) and tissue myeloperoxidase activity (p < or = 0.005) in control animals compared with leukocyte depleted animals. This study demonstrates that leukocyte depletion during initial reperfusion results in sustained improvement in postischemic left ventricular function despite the rapid return of granulocytes to the circulation.     

Event-related desynchronization (ERD) patterns during verbal memory tasks: effect of age

Event-related desynchronization (ERD) was studied in 10 young (mean age = 19.1) and 10 older (mean age = 62.8) subjects during a verbal recognition task. The attention load of the task varied according to the difficulty of discriminating between targets and distractors. EEG recorded from 29 electrodes was used to compute ERD from 14 source derivations in 125 ms intervals. Thereafter, it was displayed as spatiotemporal maps. The results show that attention influences the characteristics of EEG desynchronization. In young subjects, ERD is more pronounced and more widespread when the attentional load is high. In the elderly, differences between the two attention conditions are less marked. ANOVA reveals main effects of attention and time. The significant 'attention x time x age group' interaction confirms the presence of different brain activation patterns in the two age groups in relation to attention load.     

Surgery for hepatoblastoma in children

In order to characterize the role of transforming growth factor-alpha (TGF alpha) during hepatocarcinogenesis, liver tissue was examined at 10, 16, and 19 weeks following initial 10-week diethylnitrosamine (50 mg l-1 drinking water) exposure in female Wistar rats. Liver tissue protein extracts were electrophoresed and transferred to nitrocellulose filters. Levels of tissue-derived TGF alpha and epidermal growth factor receptor (EGFr) were assessed using an anti-TGF alpha monoclonal antibody (Ab-1) and an anti-EGFr polyclonal antibody (AB-4), coupled with scanning densitometric quantification. Immunolocalization of TGF alpha was performed in Bouin's-fixed, paraffin-embedded liver tissue sections. The distribution and intensity of TGF alpha immunoreactivity varied according to the degree of dysplasia, severely dysplastic cells being strongly immunoreactive. At week 10, mild hepatocyte dysplasia and perivenular inflammation were evident, together with a corresponding increase in perivenular TGF alpha immunoreactivity. By week 16, foci of moderate to severe dysplasia were observed; at this stage, there was a decrease in perivenular immunoreactivity but a further increase in overall liver tissue TGF alpha levels. Some 'altered foci' and dysplastic nodules showed intense immunoreactivity for TGF alpha. At these time points, immunodetectable liver EGFr was found to decrease significantly in comparison with normal control tissue. TGF alpha immunoreactivity was observed in fully developed carcinomas at week 19, although some tumours were negative by immunohistochemistry. The up-regulation of immunodetectable TGF alpha and the concomitant down-regulation of EGFr demonstrated positive (P < 0.01) and negative (P < 0.001) correlations, respectively, with hepatocyte proliferation indices. These findings suggest that the TGF alpha/EGFr ligand receptor system may be important during tumour promotion and in the stimulation of continued proliferation in hepatocellular carcinomas.