This nation will remain the land of the free only so long as it is the home of the brave. (這個國家依然會是愛好自由的人的土地，只要她仍然還是勇敢的人所住的家園。)

2011-10-25
This nation will remain the land of the free only so long as it is the home of the brave.

By Elmer Davis

「這個國家依然會是愛好自由的人的土地，只要她仍然還是勇敢的人所住的家園。」

WeiJin Tang (湯偉晉) 親自翻譯於 2011-10-25

This nation will remain the land of the free only so long as it is the home of the brave. (這個國家依然會是愛好自由的人的土地，只要她仍然還是勇敢的人所住的家園。)

(Click the following photo to view it on YouTube)

【成語】素未謀面

【成語】素未謀面

Usage Example (使用方式的例子、例句或實例):
素未謀面的人
Explanation in Chinese (中文的解釋):
指從來沒有見過面的人

claimant (【法律】索賠人)

claimant
【法律】索賠人
claimant (【法律】索賠人)

Usage Example (使用方式的例子、例句或實例):
This video is no longer available because the YouTube account associated with this video has been terminated due to multiple third-party notifications of copyright infringement from claimants including:

Sorry about that.

bone tissue engineering (硬骨組織工程)

bone tissue engineering
硬骨組織工程
bone tissue engineering (硬骨組織工程)
硬骨組織工程 (bone tissue engineering)

potassium sorbate (己二烯酸鉀)

potassium sorbate
己二烯酸鉀
potassium sorbate (己二烯酸鉀)

carbon tetrachloride (四氯化碳)

carbon tetrachloride
四氯化碳
carbon tetrachloride (四氯化碳)
四氯化碳 (carbon tetrachloride)

foe (敵人；仇敵，敵軍；(比賽的)敵手，對手)

foe (敵人；仇敵，敵軍；(比賽的)敵手，對手)
名詞
1. 敵人；仇敵 (opp. friend)，敵軍，敵兵；(比賽的)敵手，對手
2. 危害物

the mode of attack (攻擊模式)

the mode of attack
攻擊模式
the mode of attack (攻擊模式)

immune cell (免疫細胞)

immune cell
免疫細胞
immune cell (免疫細胞)
免疫細胞 (immune cell)

mobile phone ; cell phone (行動電話; 手機)

cell phone

行動電話

cell phone (行動電話)

行動電話 (cell phone)

cell phone

行動電話 (蜂巢式行動電話)

cell phone (行動電話 (蜂巢式行動電話))

行動電話 (蜂巢式行動電話) (cell phone)

cellular phone

行動電話 (蜂巢式行動電話)

cellular phone (行動電話 (蜂巢式行動電話))

行動電話 (蜂巢式行動電話) (cellular phone)

mobile phone

行動電話

mobile phone (行動電話)

行動電話 (mobile phone)

mobile phone

手機

mobile phone (手機)

手機 (mobile phone)

mobile phone

行動電話，手機

mobile phone (行動電話，手機)

行動電話，手機 (mobile phone)

mobile phone; cell phone

行動電話；手機

mobile phone; cell phone (行動電話；手機)

行動電話；手機 (mobile phone; cell phone)

long-term impact (長期的影響)

long-term impact
長期的影響
long-term impact (長期的影響)

wage index (工資指數)

wage index

工資指數

wage index (工資指數)

工資指數 (wage index)

teaching hospital (教學醫院)

teaching hospital
教學醫院
teaching hospital (教學醫院)
教學醫院 (teaching hospital)

wikipedia (維基百科)

wikipedia
維基百科
wikipedia (維基百科)
http://www.wikipedia.org/

Job Title (職稱; 職位的名稱)

job title

職稱

job title (職稱)

職稱 (job title)

job title

職位的名稱

job title (職位的名稱)

職位的名稱 (job title)

ruling class (統治階級)

ruling class
統治階級
ruling class (統治階級)

ruling
統治; 支配; 管理

plankton (【生物學】浮游生物; (總稱)浮游生物)

plankton
名詞
【生物學】浮游生物; (總稱)浮游生物

plankton (【生物學】浮游生物; (總稱)浮游生物)

optical tweezer (光學鑷子)

optical tweezer
光學鑷子
光學鑷子 (optical tweezer)
optical tweezer (光學鑷子)

Optical Tweezers - An Introduction
Source: http://www.stanford.edu

tweezer
名詞

鑷子，小鉗 [用複數，常作 a pair of tweezers]。
及物動詞

用鑷子鉗[拔](毛等)。

Optical Tweezers
An Introduction

The Basics

What is it? Optical Tweezers use light to manipulate microscopic objects as small as a single atom. The radiation pressure from a focused laser beam is able to trap small particles. In the biological sciences, these instruments have been used to apply forces in the pN-range and to measure displacements in the nm range of objects ranging in size from 10 nm to over 100 mm.

Figure 1. Optical Tweezers principles.

How does it work? The most basic form of an optical trap is diagramed in Fig 1a. A laser beam is focused by a high-quality microscope objective to a spot in the specimen plane. This spot creates an "optical trap" which is able to hold a small particle at its center. The forces felt by this particle consist of the light scattering and gradient forces due to the interaction of the particle with the light (Fig 1b, see Details). Most frequently, optical tweezers are built by modifying a standard optical microscope. These instruments have evolved from simple tools to manipulate micron-sized objects to sophisticated devices under computer-control that can measure displacements and forces with high precision and accuracy.

Applications

Optical Tweezers have been used to trap dielectric spheres, viruses, bacteria, living cells, organelles, small metal particles, and even strands of DNA. Applications include confinement and organization (e.g. for cell sorting), tracking of movement (e.g. of bacteria), application and measurement of small forces, and altering of larger structures (such as cell membranes). Two of the main uses for optical traps have been the study of molecular motors and the physical properties of DNA. In both areas, a biological specimen is biochemically attached to a micron-sized glass or polystyrene bead that is then trapped. By attaching a single molecular motor (such as kinesin, myosin, RNA polymerase etc.) to such a bead, researchers have been able to probe motor properties such as: Does the motor take individual steps? What is the step size? How much force can the motor produce? Similarly, by attaching the beads to the ends of single pieces of DNA, experiments have measured the elasticity of the DNA, as well as the forces under which the DNA breaks or undergoes a phase transition.

Details

Principle of Operation: Fig 1b shows a more detailed look at how an optical trap works. The basic principle behind optical tweezers is the momentum transfer associated with bending light. Light carries momentum that is proportional to its energy and in the direction of propagation. Any change in the direction of light, by reflection or refraction, will result in a change of the momentum of the light. If an object bends the light, changing its momentum, conservation of momentum requires that the object must undergo an equal and opposite momentum change. This gives rise to a force acting on the object.
In a typical optical tweezers setup the incoming light comes from a laser which has a "Gaussian intensity profile". Basically, the light at the center of the beam is brighter than the light at the edges. When this light interacts with a bead, the light rays are bent according the laws of reflection and refraction (two example rays are shown in Fig 1b). The sum of the forces from all such rays can be split into two components: Fscattering, the scattering force, pointing in the direction of the incident light (z, see axes in Fig 1b), and Fgradient, the gradient force, arising from the gradient of the Gaussian intensity profile and pointing in x-y plane towards the center of the beam (dotted line). The gradient force is a restoring force that pulls the bead into the center. If the contribution to Fscattering of the refracted rays is larger than that of the reflected rays then a restoring force is also created along the z-axis, and a stable trap will exist. Incidentally, the image of the bead can be projected onto a quadrant photodiode to measure nm-scale displacements (see Further Reading).
When the bead is displaced from the center of the trap, what force does it feel? The restoring force of the optical trap works like an optical spring: the force is proportional to the displacement out of the trap. In practice, the bead is constantly moving with Brownian motion. But whenever it leaves the center of the optical trap the restoring force pulls it back to the center. If some external object, like a molecular motor, were to pull the bead away from the center of the trap, a restoring force would be imparted to the bead and thus to the motor. An example trace of a single kinesin motor taking 8 nm steps against a 5-pN force is shown in Fig 2.

Figure 2. Measurement of the 8-nm steps of kinesin.

Modern Optical Tweezers: In practice, optical tweezers are very expensive, custom-built instruments. These instruments usually start with a commercial optical microscope but add extensive modifications. In addition, the capability to couple multiple lasers into the microscope poses another challenge. High power infrared laser beams are often used to achieve high trapping stiffness with minimal photo-damage to biological samples. Precise steering of the optical trap is accomplished with lenses, mirrors, and acousto/electro-optical devices that can be controlled via computer. Figure 3 is meant to give an idea of the number of elements in such a system. In short, these are very complicated instruments that require a working knowledge of microscopy, optics, and laser techniques.

Figure 3. Typical modern optical tweezers setup.

First Demonstration of Optical Tweezers

A. Ashkin, J.M. Dziedzic, J.E. Bjorkholm and S. Chu. 1986. "Observation of a Single-Beam Gradient Force Optical Trap for Dielectric Particles." Opt. Lett. 11 (5) 288-290.

Further Reading

1. Block S. M. 1992. "Making light work with optical tweezers." Nature 360(6403):493-5.
2. Svoboda K., Block S. M. 1994. "Biological applications of optical forces." Annu Rev Biophys Biomol Struct 23:247-85.
3. Simmons R. M., Finer J. T., Chu S., Spudich J. A. 1996. "Quantitative measurements of force and displacement using an optical trap." Biophys J 70(4):1813-22.
4. Visscher K., Gross S. P., Block S. M. 1996. "Construction of multiple-beam optical traps with nanometer-resolution position sensing." IEEE Journal of Selected Topics in Quantum Electronics 2(4):1066-1076.
5. Gittes F., Schmidt C. F. 1998. "Interference model for back-focal-plane displacement detection in optical tweezers." Optics Letters 23(1):7-9.
6. Peters I. M., de Grooth B. G., Schins J. M., Figdor C. G., Greve J. 1998. "Three dimensional single-particle tracking with nanometer resolution." Review of Scientific Instruments 69(7):2762-6.
7. Smith S. P., Bhalotra S. R., Brody A. L., Brown B. L., Boyda E. K., Prentiss M. 1998. "Inexpensive optical tweezers for undergraduate laboratories." Am. J. Phys. 67(1):26-35.
8. Visscher K., Block S. M. 1998. "Versatile optical traps with feedback control." Methods Enzymol 298:460-89.
9. Neuman K. C., Chadd E. H., Liou G. F., Bergman K., Block S. M. 1999. "Characterization of photodamage to escherichia coli in optical traps." Biophys J 77(5):2856-63.
10. Pralle A., Prummer M., Florin E. L., Stelzer E. H., Horber J. K. 1999. "Three-dimensional high-resolution particle tracking for optical tweezers by forward scattered light." Microsc Res Tech 44(5):378-86.
11. Ashkin, A. 2000. "History of Optical Trapping and Manipulation of Small-Neutral Particle, Atoms, and Molecules." IEEE Journal of Selected Topics in Quantum Electronics 6(6):841-856.
12. Ishii Y., Ishijima A., Yanagida T. 2001." Single molecule nanomanipulation of biomolecules." Trends Biotechnol 19(6):211-6.
13. Kuo S. C. 2001. "Using optics to measure biological forces and mechanics." Traffic 2(11):757-63.
14. Lang M. J., Asbury C. L., Shaevitz J. W., Block S. M. 2002. "An automated two-dimensional optical force clamp for single molecule studies." Biophys J 83(1):491-501.

Related Techniques

Atomic Force Microscopy, Magnetic Tweezers

metabolism (新陳代謝，代謝作用)

metabolism

新陳代謝

metabolism (新陳代謝)

新陳代謝 (metabolism)

metabolic pathway

新陳代謝的反應路徑

metabolic pathway (新陳代謝的反應路徑)

新陳代謝的反應路徑 (metabolic pathway)

metabolic

新陳代謝的

metabolic (新陳代謝的)

新陳代謝的 (metabolic)

metabolism
名詞
【生物學】新陳代謝，代謝作用
metabolism (【生物學】新陳代謝，代謝作用)

preferential (優先的；優待的；優先選擇的; (國際貿易等方面)特惠的)

preferential
形容詞
1. 優先的；優待的；優先選擇的；差別制的。
2. (國際貿易等方面)特惠的。
名詞
1. 優先權。
2. 特惠稅率。
-ism 名詞
關稅特惠主義。
-ist 名詞
關稅特惠主義者。

preferential (優先的；優待的；優先選擇的; (國際貿易等方面)特惠的)

habitable (適合居住的; 可以居住的)

habitable
形容詞:
適合居住的
適合居住的; 可以居住的
habitable (適合居住的; 可以居住的)

capable (能幹的；有能力的; 能接受...的；易教化的)

capable
capable (能幹的；有能力的; 能接受...的；易教化的)

形容詞:
Having power, skill, or ability.
能幹的；有能力的

例句：a capable servant
能幹的僕人

Receptive; open to influence.
能接受...的；易教化的

例句：
a capable student
可教化之學生；可教之材

片語：
capable of
(a)(指人)有...能力、技巧或傾向的。(b)(指事物)可以...的；容許...的；易...的。(c)可容納的。(d)能感覺到...的

相關字：adv. capably. n. capableness.
同義字：able, competent, efficient, skillful.

Source:  顔元叔教授主編的 網路 英英_英漢辭典
Source URL:

http://www.onlinedict.com/servlet/MobiDictLookup14?example=on&phrase=on&WoRd=capable

prohibit (禁止)

prohibit
prohibit (禁止)
(過去式: prohibited; 過去完成式: prohibited; 現在進行式: prohibiting)
及物動詞:
To forbid by law.
禁止
例句：

Smoking is strictly prohibited here.
此處嚴禁吸菸

To hinder; prevent.
阻礙；阻止

例句：
Students are prohibited from staying out after 10 o'clock.
學生十點以後禁止外出

Source:  顔元叔教授主編的 網路 英英_英漢辭典
Source URL:

http://www.onlinedict.com/servlet/MobiDictLookup14?example=on&phrase=on&WoRd=prohibit

Retired Content (已經退休的內容)

Retired Content
已經退休的內容
Retired Content (已經退休的內容)

Security Architecture (安全性架構)

Security Architecture
安全性架構
Security Architecture (安全性架構)

contents (內容)

content
contents
內容
contents (內容)

Applies to: (適用的範圍:)

Applies to:
適用的範圍:
Applies to: (適用的範圍:)