eLearning

Kenneth Buckle, a visiting scientist at the Center
for Integrated Manufacturing Studies at the Rochester
Institute of Technology, provides this answer:
When connected to a load like a lightbulb, a typical battery
undergoes chemical reactions that release electrons, which
travel through the bulb and are then reabsorbed by the battery.
(Devices that store mechanical energy also exist, but the most
common bat ter ies ,  such as those used in fl  ashlights and   remotes,
hold energy in chemical form.) Inside is at least one galvanic
cell, which produces between zero and several volts,   depending
on its chemistry. In a car battery, six cells, each contributing
two volts, are connected in series …

David W. Schindler
ABSTRACT
The results of bottle and mesocosm experiments
were compared with those obtained in whole-
ecosystem experiments at the Experimental Lakes
Area. Unless they can be cleverly designed to mimic
major ecosystem processes and community compo-
sitions, smaller-scale experiments often give highly
replicable, but spurious, answers. Problems with
appropriate scaling are difficult to deduce without
direct comparisons with whole-ecosystem experi-
ments. Reasons aremany, but include inappropriate
spatial scales to include whole communities, in
particular predators and nocturnally active animals;
temporal scales that are too short to assess accu-
rately the response of slow-responding organisms
and biogeochemical processes; and elimination of
key littoral–pelagic and catchment–lake interac-
tions. Identical studies of limnological processes in
lakes of a large …

David A. Starrett
Economists are widely viewed by the general public
as being committed tomarkets as a way of allocating
resources and consequently to the use of market
prices as a reflection of social value. This view has
given economists a bad reputation in some circles;
indeed, there is a cynical definition of an economist
as someone who ‘‘knows the price of everything and
the value of nothing.’’ Whereas economists prob-
ably do as a group have more faith in markets than
others, it certainly is not true that we equate price
with value. We recognize many goods and services
for which there are no markets (such as clean air,
wildlife habitat, and …

Dan Binkley,
Yowhan Son,
and David W. Valentine
ABSTRACT
The nitrogen (N) cycle of forest ecosystems is un-
derstood relatively well, and few scientists expect
that major revisions will be necessary; most current
work on N cycling focuses on improving the preci-
sion estimates of pools and fluxes, or measuring the
magnitudes of well-known pools in response to
management or disturbances. However, in the past
few decades more than a dozen articles in refereed
journals have claimed very high rates of N input, far
beyond the rates expected for known sources of N.
In this review, we summarize the literature on N
accretion rates in forests that lack substantial con-
tributions from symbiotic N-fixing plants. We …

Howard T. Odum
and Eugene P. Odum
Valuation is one mechanism by which humans
organize occupancy and use of large-scale ecosys-
tems and regions, such as watersheds, estuaries,
cities, states, nations, and ultimately the whole
earth (the global perspective). When human valua-
tions do not measure the real contributions of
natural ecosystems, as is currently the case, ecosys-
tems are not protected, and the larger systems
produce less when the natural ecosystems are lost to
development. Ecologists working on small-scale
studies are concerned with the loss of their study
areas and biodiversity. Ecologists working at large
scales, and society in general, have to be concerned
that poor valuation is delaying the organization of a
sustainable pattern …

Lowell Pritchard Jr.,
Carl Folke,
and Lance Gunderson
INTRODUCTION
As long as we are forced to make choices, we are
doing valuation. But different approaches to valua-
tion are based on qualitatively different assump-
tions. For example, the economics approach to
valuation is based on the ethical principle of con-
sumer sovereignty, and it privileges the kinds of
decisions individuals make in the marketplace. We
accept the economics approach as a useful partial
approach to decision making in relation to ecosys-
temservices if one is interested in what people think
about and want from services; if one believes that
human preferences are the basis for the value of
services; if one accepts the assumption that adding
individual …

Soojin Park,
Dong Hyun Lee,
Ji Xu,
Bokyung Kim,
Sung Woo Hong,
Unyong Jeong,
Ting Xu,
Thomas P. Russell
Generating laterally ordered, ultradense, macroscopic arrays of nanoscopic elements will
revolutionize the microelectronic and storage industries. We used faceted surfaces of commercially
available sapphire wafers to guide the self-assembly of block copolymer microdomains into
oriented arrays with quasi–long-range crystalline order over arbitrarily large wafer surfaces.
Ordered arrays of cylindrical microdomains 3 nanometers in diameter, with areal densities in
excess of 10 terabits per square inch, were produced. The sawtoothed substrate topography
provides directional guidance to the self-assembly of the block copolymer, which is tolerant of
surface defects, such as dislocations. The lateral ordering and lattice orientation …

Y. CORDIER,
1,3 P. MISKA,
1 and D. FERRE2
1.—Institut d’Electronique et de Microélectronique du Nord, U.M.R.-C.N.R.S 8520,
Avenue Poincaré, Université de Lille 1, BP 69, 59652 Villeneuve d’Ascq Cedex, France.
2.—Laboratoire Structure et Propriétés de l’Etat Solide, URA 234, Université de Lille 1,
59650 Villeneuve d’Ascq, France. 3.—e-mail: yvon.cordier@iemn.univ-lille1.fr
InAs islands self-assembled on InAlAs layers lattice mismatched on GaAs
substrates have been grown by molecular beam epitaxy. Both pseudomorphic
and metamorphic InAlAs buffer layers were used as a template to investigate the
effects of strain relaxation on the formation of the islands. The effect of alloy
composition in the metamorphic templates is shown on the density and the shape
of …

X Z Shang1,3
,SDWu2
, C Liu1
,WXWang2
, LWGuo2
, Q Huang2
and J M Zhou2
1
School of Physics and Technology, Wuhan University, Wuhan 430072, Hubei, People’s
Republic of China
2
State Key Laboratory for Surface Physics, Institute of Physics, Chinese Academy of
Sciences, Beijing 100080, People’s Republic of China
E-mail: xunzhong@acc-lab.whu.edu.cn
Received 8 December 2005
Published 20 April 2006
Online at stacks.iop.org/JPhysD/39/1800
Abstract
Low-temperature step-graded InAlAs metamorphic buffer layers on GaAs
substrate grown by molecular beam epitaxy were investigated. The strain
relaxation and the composition of the top InAlAs layer were determined by
high-resolution triple-axis x-ray diffraction measurements, which show that
the top InAlAs layer is nearly fully relaxed. Surface morphology was
observed by reflection high-energy electron diffraction pattern and …

Cheng Cen,
Stefan Thiel,
Jochen Mannhart,
Jeremy Levy
Electronic confinement at nanoscale dimensions remains a central means of science and
technology. We demonstrate nanoscale lateral confinement of a quasi–two-dimensional electron
gas at a lanthanum aluminate–strontium titanate interface. Control of this confinement using an
atomic force microscope lithography technique enabled us to create tunnel junctions and field-effect
transistors with characteristic dimensions as small as 2 nanometers. These electronic devices can be
modified or erased without the need for complex lithographic procedures. Our on-demand
nanoelectronics fabrication platform has the potential for widespread technological application.