The human body is an intricate biochemical–mechanical system, with an exceedingly precise hierarchical organization in which all components work together in harmony across a wide range of dimensions. Many fundamental biological processes take place at surfaces and interfaces (e.g., cell–matrix interactions), and these occur on the nanoscale. For this reason, current health‐related research is actively following a biomimetic approach in learning how to create new biocompatible materials with nanostructured features. The ultimate aim is to reproduce and enhance the natural nanoscale elements present in the human body and to thereby develop new materials with improved biological activities. Progress in this area requires a multidisciplinary effort at the interface of biology, physics, and chemistry. In this Review, the major techniques that have been adopted to yield novel nanostructured versions of familiar biomaterials, focusing particularly on metals, are presented and the way in which nanometric surface cues can beneficially guide biological processes, exerting influence on cellular behavior, is illustrated. Frontispiece adapted from Reference 94 .
Circular RNAs (circRNAs) are a large class of relatively stable RNA molecules that are highly expressed in animal brains. Many circRNAs have been associated with CNS disorders accompanied by an aberrant wake-sleep cycle. However, the regulation of circRNAs in brain homeostasis over daily light-dark (LD) cycles has not been characterized. Here, we aim to quantify the daily expression changes of circRNAs in physiological conditions in healthy adult animals. Using newly generated and public RNA-Seq data, we monitored circRNA expression throughout the 12:12 h LD cycle in various mouse brain regions. We identified that Cdr1as, a conserved circRNA that regulates synaptic transmission, is highly expressed in the suprachiasmatic nucleus (SCN), the master circadian pacemaker. Despite its high stability, Cdr1as has a very dynamic expression in the SCN throughout the LD cycle, as well as a significant regulation in the hippocampus following the entry into the dark phase. Computational integration of different public datasets predicted that Cdr1as is important for regulating light entrainment in the SCN. We hypothesize that the expression changes of Cdr1as in the SCN, particularly during the dark phase, are associated with light-induced phase shifts. Importantly, our work revises the current beliefs about natural circRNA stability and suggests that the time component must be considered when studying circRNA regulation. 相似文献
Juice from five different varieties of oranges grown in Lebanon was canned according to commercial practices and stored at room temperature. At weekly intervals for seven weeks, chemical analyses for ascorbic acid, total acidity, total soluble solids, nitrogen, ash, total lipids, total solids, essential oils and flavonoids were performed on each sample. The fresh juice from the Blood and Washington Navel varieties compared favourably in chemical composition with a concentrated frozen product from the U.S.A.; the juice from Blood withstood canning and storage better than all other varieties tested. In all samples, there was a significant decrease in the levels of ascorbic acid and of essential oils during storage. Statistical analysis of organoleptic evaluations showed that, in general, blends of two or three different varieties were preferred to the juice from a single variety. 相似文献
This paper describes an analog frequency divider by two working in the millimeter wave frequency range around 60 GHz. This circuit is analyzed with a new method that allows one to determine the steady-state regime of any synchronized circuits with standard CAD commercial software. The method proposed relies upon the concept of open loop systems and is applicable to any feedback transistor circuits. The designed circuit was processed using a standard 0.25-μm HEMT technology. Four transistors were used for realizing the frequency division function as well as the input and output amplification. More than 10% frequency lock-in bandwidth was achieved, and conversion gain was obtained using input and output buffers. Measured results were found to be in good agreement with simulated ones 相似文献
Since nearly a decade ago, Iranian policy circles have declared innovation and development of science-based industries as a priority area. This paper utilizes the emerging Iranian patent stock in the USPTO to ascertain progress on this front. Results indicate that there are policy traces in the emerging patent portfolio as proxied by sponsorship statements in 28% of all patents. However, there is little evidence of technological specialization. Breaking down the portfolio into foreign-assigned, Iranian-assigned, unassigned and Iranian-sponsored patents, indicates that foreign-assigned, followed by Iranian-assigned patents are of higher quality and potential value. Nearly half of the patents are unassigned and 40% are assigned to foreign entities. Lack of ownership assignment can be a hurdle to effective exploitation, defense and maintenance of patents. The analysis is concluded by relevant policy lessons. 相似文献
We describe a nonuniform spectral resampling transform (NUSRT) that resamples a frequency-scaled spectrum that has been measured by a Fourier-transform spectrometer (FTS). Frequency scaling of a spectrum can arise from measurements made with off-axis detectors and Doppler shift induced by motion of a spaceborne FTS relative to an input radiation source. In addition, a spectrum may need to be rescaled in frequency to match spectral lines for applications such as the retrieval of atmospheric state parameters. The NUSRT is cast as a linear algebraic expression that relates a nonuniformly sampled interferogram to an input spectrum. A polynomial approximation is applied to this expression that reduces the inverse of the NUSRT to a series of Fourier transforms that can be implemented as fast Fourier transforms (FFTs). We show that this NUSRT algorithm requires on the order of 6N log N flops, which reduces the computational cost of rescaling by more than 1 order of magnitude compared with conventional FFT-based Shannon interpolation techniques while comparable accuracy is maintained. 相似文献
We describe the approach for the estimation of the atmospheric state, e.g., temperature, water, ozone, from calibrated, spectral radiances measured from the Tropospheric Emission Spectrometer (TES) onboard the Aura spacecraft. The methodology is based on the maximum a posteriori estimate, which mathematically requires the minimization of the difference between observed spectral radiances and a nonlinear model of radiative transfer of the atmospheric state subject to the constraint that the estimated state must be consistent with an a priori probability distribution for that state. The minimization techniques employed here are based on the trust-region Levenberg-Marquardt algorithm. An analysis of the errors for this estimate include smoothing, random, spectroscopic, \"cross-state\", representation, and systematic errors. In addition, several metrics and diagnostics are introduced that assess the resolution, quality, and statistical significance of the retrievals. We illustrate this methodology for the retrieval of atmospheric and surface temperature, water vapor, and ozone over the Gulf of Mexico on November 3, 2004. 相似文献
Growth, antibacterial and proteolytic activities of two new lactobacilli strains isolated from matsoun (Armenian traditional dairy product) and their pH dependence were studied. The results demonstrated the antibacterial activity of lactobacilli against Gram‐positive and Gram‐negative test strains. This activity was stable when pH of cell culture medium was adjusted to the value of 6.5. At pH 8, the antibacterial activity of only one strain was stable. Both strains were able to hydrolyse casein in pH range of 5.5–8 with maximal activity at pH 5.5. Controlled pH conditions were suitable for biomass yield, while noncontrolled pH was better for expression of antibacterial activity. 相似文献
Uniform GaN nanorod arrays are grown vertically by selective area growth on (left angle bracket 0001 right angle bracket) substrates. The GaN nanorods present six nonpolar {1?100} facets, which serve as growth surfaces for InGaN-based light-emitting diode quantum well active regions. Compared to growth on the polar {0001} plane, the piezoelectric fields in the multiple quantum wells (MQWs) can be eliminated when they are grown on nonpolar planes. The capability of growing ordered GaN nanorod arrays with different rod densities is demonstrated. Light emission from InGaN/GaN MQWs grown on the nonpolar facets is investigated by photoluminescence. Local emission from MQWs grown on different regions of GaN nanorods is studied by cathodoluminescence (CL). The core-shell structure of MQWs grown on GaN nanorods is investigated by cross-sectional transmission electron microscopy in both axial and radial directions. The results show that the active MQWs are predominantly grown on nonpolar planes of GaN nanorods, consistent with the observations from CL. The results suggest that GaN nanorod arrays are suitable growth templates for efficient light-emitting diodes. 相似文献
The in vitro immunoreactive (i-LH) and bioactive (b-LH) LH release from hemipituitaries of intact adult male rats (INT) or rats castrated 7 days earlier (CAS) was studied. Hemipituitaries were incubated for 30 min (time 1) plus an additional 30 min (time 2) with GnRH (10 nM) and/or KCl (50 mM), according to one of the following protocols: media alone (C), KCl+KCl (K/K), GnRH+GnRH (G/G), KCl+GnRH (K/G), GnRH+KCl (G/K). All of the hemipituitaries were further incubated in media alone for 120 min (time 3). I-LH, b-LH and i-FSH were assayed on the media. In both models, the highest bioactive:immunoactive (b/i) ratio was noted during time 1; however, CAS always secreted more b-LH than INT at any given time of the study. In INT, GnRH--but not KCl--administration during time 2 resulted in blunted i-LH. During the same time, the b/i ratios decreased in all groups but G/K. LH secretion recovered during time 3 in all groups. In CAS, i-LH levels comparable to those of time 1 were sustained by either stimulus during time 2, while the b/i ratios were markedly decreased. LH secretion recovered in the K/K group during time 3. These results suggest that: 1) promptly releasable pools of b-LH are available in both models; 2) CAS always secrete more b-LH; 3) in INT, desensitization occurs involving parallel changes in both i-LH and b-LH, while changes in b-LH rather than i-LH are noted in CAS; 4) prolonged KCl administration might play a role in new gonadotropin synthesis and/or release. 相似文献