Bone modeling and remodeling are governed by distinct biochemical processes that may hold unique opportunities for optimizing bone mass[1,2].Remodeling refers to the coupled resorption and subsequent formation on the ...Bone modeling and remodeling are governed by distinct biochemical processes that may hold unique opportunities for optimizing bone mass[1,2].Remodeling refers to the coupled resorption and subsequent formation on the bone surface,while modeling represents uncoupled formation or resorption.Mechanical loading is known to improve bone mass,though whether this occurs through modeling or remodeling(or by some combination)is unclear.Dynamic in vivo morphometry utilizing high resolution micro-CT and image registration has only recently become feasible and thus holds an untapped and expanding potential for understanding bone metabolism by quantifying and localizing formation/resorption and modeling/remodeling events.16-week-old mice were given 2 baseline weekly micro-CT scans of both tibiae prior to the initiation of daily unilateral loading(contralateral limb for nonloaded control).Weekly scanning and daily loading continued for 5 weeks.Registered images for each mouse in a global coordinate system revealed the time course of each voxel,and changes in bone mass were quantified as modeling or remodeling starting at the onset of loading.In cortical bone,after an initial response to loading in both regimes,modeling emerged as the dominant response.Loading effects were largest in areas of mechanical significance.For example,anabolic modeling on the periosteal surface of the half of the tibia in compression under axial load presented a strong effect of loading,whereas the same measure on the endosteal surface in the area in tension showed no difference.Similarly,in trabecular bone anabolic modeling was significantly increased with loading on trabecular plates but not rods(plates have been shown to be the major contributor to overall bone strength).The catabolic modeling response on the endosteal surface showed an interesting transition over time.Loading initially led to a significant suppression of catabolic modeling,but over time increased it to levels significantly beyond that of nonloaded controls.展开更多
In this paper, the fabrication and investigation of flexible impedance and capacitive tensile load sensors based on carbon nanotube（CNT） composite are reported. On thin rubber substrates, CNTs are deposited from sus...In this paper, the fabrication and investigation of flexible impedance and capacitive tensile load sensors based on carbon nanotube（CNT） composite are reported. On thin rubber substrates, CNTs are deposited from suspension in water and pressed at elevated temperature. It is found that the fabricated load cells are highly sensitive to the applied mechanical force with good repeatability. The increase in impedance of the cells is observed to be 2.0 times while the decrease in the capacitance is found to be 2.1 times as applied force increases up to 0.3 N. The average impedance and capacitive sensitivity of the cell are equal to 3.4 N^（-1） and 1.8 N^（-1）, respectively. Experimental results are compared with the simulated values,and they show that they are in reasonable agreement with each other.展开更多
This paper presents a three-stage CMOS operational amplifier （opamp） that combines accuracy with stability for a wide range of capacitive loads. A so-called quenching capacitor is added to a multipath nested Miller ...This paper presents a three-stage CMOS operational amplifier （opamp） that combines accuracy with stability for a wide range of capacitive loads. A so-called quenching capacitor is added to a multipath nested Miller compensation （MNMC） topology to obtain stability for a wide range of capacitive loads. Theoretical analysis and mathematical formulas are provided to prove the improvement in stability. A prototype of this frequency compen- sation scheme is implemented in a 0.7μm CMOS process. Measurement′s show that the amplifier can drive capaci- tive loads ranging from 100pF to 100/μF with a gain of 90dB and a minimum phase margin of 26°. The amplifier has a unity-gain bandwidth of 1MHz for a 100pF capacitive load. It employs a quenching capacitance of 18pF.展开更多
Ultra wide bands antennas with notched bands characteristics have recently been considered for efficient communication between devices. In this paper, a compact ultra-wideband antenna (UWB) for UWB applications with t...Ultra wide bands antennas with notched bands characteristics have recently been considered for efficient communication between devices. In this paper, a compact ultra-wideband antenna (UWB) for UWB applications with triple bandnotched characteristics is presented. The proposed antenna consists of a square patch with four truncated corners and a partial ground plane with a rectangular slit. The operation bandwidth of the designed antenna is from 2.66 GHz to more than 13.5 GHz. Band-notched characteristics of antenna to reject the frequency band of 3.18 - 3.59 GHz and 4.70 - 5.88 GHz, is realized by inserting two C-shaped slots in the patch, the third band of 9.54 - 12.22 GHz is achieved by slottype capacitively-loaded loop (CLL) inserted in the patch near the feed line. Details of the proposed antenna design and simulated results are presented and discussed.展开更多
基金supported by the National Institute of Arthritis and Musculoskeletal and Skin Diseases ( R01 AR069148)
文摘Bone modeling and remodeling are governed by distinct biochemical processes that may hold unique opportunities for optimizing bone mass[1,2].Remodeling refers to the coupled resorption and subsequent formation on the bone surface,while modeling represents uncoupled formation or resorption.Mechanical loading is known to improve bone mass,though whether this occurs through modeling or remodeling(or by some combination)is unclear.Dynamic in vivo morphometry utilizing high resolution micro-CT and image registration has only recently become feasible and thus holds an untapped and expanding potential for understanding bone metabolism by quantifying and localizing formation/resorption and modeling/remodeling events.16-week-old mice were given 2 baseline weekly micro-CT scans of both tibiae prior to the initiation of daily unilateral loading(contralateral limb for nonloaded control).Weekly scanning and daily loading continued for 5 weeks.Registered images for each mouse in a global coordinate system revealed the time course of each voxel,and changes in bone mass were quantified as modeling or remodeling starting at the onset of loading.In cortical bone,after an initial response to loading in both regimes,modeling emerged as the dominant response.Loading effects were largest in areas of mechanical significance.For example,anabolic modeling on the periosteal surface of the half of the tibia in compression under axial load presented a strong effect of loading,whereas the same measure on the endosteal surface in the area in tension showed no difference.Similarly,in trabecular bone anabolic modeling was significantly increased with loading on trabecular plates but not rods(plates have been shown to be the major contributor to overall bone strength).The catabolic modeling response on the endosteal surface showed an interesting transition over time.Loading initially led to a significant suppression of catabolic modeling,but over time increased it to levels significantly beyond that of nonloaded controls.
基金Ghulam Ishaq Khan Institute of Engineering Science and Technology, Pakistan for its support
文摘In this paper, the fabrication and investigation of flexible impedance and capacitive tensile load sensors based on carbon nanotube（CNT） composite are reported. On thin rubber substrates, CNTs are deposited from suspension in water and pressed at elevated temperature. It is found that the fabricated load cells are highly sensitive to the applied mechanical force with good repeatability. The increase in impedance of the cells is observed to be 2.0 times while the decrease in the capacitance is found to be 2.1 times as applied force increases up to 0.3 N. The average impedance and capacitive sensitivity of the cell are equal to 3.4 N^（-1） and 1.8 N^（-1）, respectively. Experimental results are compared with the simulated values,and they show that they are in reasonable agreement with each other.
文摘This paper presents a three-stage CMOS operational amplifier （opamp） that combines accuracy with stability for a wide range of capacitive loads. A so-called quenching capacitor is added to a multipath nested Miller compensation （MNMC） topology to obtain stability for a wide range of capacitive loads. Theoretical analysis and mathematical formulas are provided to prove the improvement in stability. A prototype of this frequency compen- sation scheme is implemented in a 0.7μm CMOS process. Measurement′s show that the amplifier can drive capaci- tive loads ranging from 100pF to 100/μF with a gain of 90dB and a minimum phase margin of 26°. The amplifier has a unity-gain bandwidth of 1MHz for a 100pF capacitive load. It employs a quenching capacitance of 18pF.
文摘Ultra wide bands antennas with notched bands characteristics have recently been considered for efficient communication between devices. In this paper, a compact ultra-wideband antenna (UWB) for UWB applications with triple bandnotched characteristics is presented. The proposed antenna consists of a square patch with four truncated corners and a partial ground plane with a rectangular slit. The operation bandwidth of the designed antenna is from 2.66 GHz to more than 13.5 GHz. Band-notched characteristics of antenna to reject the frequency band of 3.18 - 3.59 GHz and 4.70 - 5.88 GHz, is realized by inserting two C-shaped slots in the patch, the third band of 9.54 - 12.22 GHz is achieved by slottype capacitively-loaded loop (CLL) inserted in the patch near the feed line. Details of the proposed antenna design and simulated results are presented and discussed.
基金Project Supported by Natural Science Foundation of China(50977062、51207106、51307120)Development fund Program of Science&Technology of Tianjin Higher University(20110411)
