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英语听力听写练习原文
〈〉第一集
1.
Ocean Plastic
Particles Could Get in Gills
Sea
creatures
eat
plastic
dumped
in
the
ocean,
but
they
also
might
be
accumulating
plastic
by
sucking
up
tiny
particles
with
their
siphons
and
gills.
Christopher
Intagliata
reports.
There are now at least five major
garbage patches in the world's oceans, and much of
that
trash
is
plastic.
But
last
month
researchers
said
they
can
only
account
for
one
percent of the plastic
they'd expect to find in the oceans. So, where'd
the rest of it go
Well, animals eat some of
it. Plastic has been found in turtles, seabirds,
fish, plankton,
shellfish,
even
bottom-feeding
invertebrates.
But
there's
another
way
sea
creatures
might be accumulating plastic: by
sucking up tiny plastic particles with their
siphons and
gills.
Researchers
added
common
shore
crabs
—
Carcinus
maenas
—
to
tanks
of
seawater
containing millions of tiny plastic
particles, just 10 microns in diameter. After 16
hours,
all the crabs had plastic lodged
in their gills. And the particles stuck around for
up to
three weeks, too. The results are
in the journal Environmental Science and
Technology.
[Andrew
J.
R.
Watts
et
al,
Uptake
and
Retention
of
Microplastics
by
the
Shore
Crab
Carcinus maenas]
The longer plastic sits in
an animal, researchers say, the better the chances
it will travel
up the food chain.
Meaning all our plastic waste could come back to
bite us
—
or rather
be bitten by us.
if they're from
a site where there's plastic
present.
the University of Exeter.
chances are we do have some.
—
Christopher
Intagliata
2.
Salmonella's Favorite Food
Could Be Its Achilles' Heel
Salmonella's primary fuel source is the
molecule fructose-asparagine. Starving it of that
fuel
in
an
infected
person
could
kill
it
without
harming
beneficial
gut
bacteria.
Karen
Hopkin reports
Summer’s here and with it
come picnic
s, barbecues and of course
salmonella. The germ
is
notorious
for
contaminating
a
variety
of
favorite
warm-weather
foods.
But
the
bacteria’s
palate
is
more
limited
than
ours.
Once
salmonella
makes
its
way
into
your
system, it relies on a
single unusual nutr
ient to survive.
That’s according to a study in
the
journal PLoS Pathogens. [Mohamed M. Ali et al,
Fructose-Asparagine Is a Primary
Nutrient during Growth of Salmonella in
the Inflamed Intestine]
Most people tough it out when they get
food poisoning from
salmonella. That’s
because
treatment
with
antibiotics
would
eliminate
the
infection,
but
also
get
rid
of
the
gut
bacteria that promote good
health.
To figure out how to target salmonella
specifically, researchers screened for genes vital
for
the
microbe’
s
survival
during
the
active
phase
of
infection.
And
they
identified
a
cluster of five genes that work
together to allow the bacteria to digest a
molecule called
fructose-asparagine.
No
other
organisms
are
known
to
use
this
chemical
for
fuel,
so
starving
salmonella of it could be a new strategy for
fighting this foodborne bug while
leaving desirable intestinal
inhabitants unharmed.
Next,
the
researchers
plan
to
see
which
foods
contain
large
amounts
of
salmonella’s
go-
to snack. But please,
don’t send unsolicited samples of Aunt Agnes’s egg
salad.
—
Karen Hopkin
3.
Education Level Linked to
Nearsightedness
In a German
study, half of those with a university degree were
myopic compared with
less
than
a
quarter
of
folks
who
quit
after
high
school
or
secondary
school.
Karen
Hopkin reports
Nothing says “overeducated egghead”
like a pair of coke
-bottle glasses. But
even clichés
sometimes hit the nerd on
the head. Because a new study finds that
nearsightedness is
linked to the number
of years spent in school. The findings can be
viewed in the journal
Ophthalmology.
[Alireza Mirshahi et al, Myopia and Level of
Education]
In the past century, the prevalence of
myopia
—
science-speak for
being able to see only
what’s right in
front of you—
has been on t
he
rise. So much so that it can’t all be blamed
on geeky genes.
To
nail
down
the
potential
environmental
influences,
researchers
focused
on
the
classroom. They gave eye exams to
nearly 5000 German subjects in a project called
the
Gutenberg Health Study.
The researchers
found
that
individuals
with
13
years
of
education
were
more
myopic
than
those
who
didn’t
get
past
primary
school.
And
more
than
half
of
those
with
a
university degree could use a set of
specs, compared to less than a quarter of the
folks
who quit after high school or
secondary school.
All that learning takes a
lot of reading. Which itself is associated with
nearsightedness.
Or the nearsighted may
gravitate toward pursuits easier to
see
—
like hitting the books.
Either way, seems that being a good
student may not require great pupils.
—
Karen Hopkin
4.
Give Us This
Day the Bread Wheat Genome
A
preliminary
map
of
the
bread
wheat
genome
includes
the
locations
of
more
than
75,000 genes. Cynthia
Graber reports
Wheat helped cre
ate
civilization in the Middle East. It’s a staple
crop for 30 percent of
the
world’s
population.
And
now,
with
the
publication
of
four
articles
in
the
journal
Science,
we’re
close
to
a
detailed
understanding
of
the
bread
wheat
genome.
[Kellye
Eversole et al,
Slicing the wheat genome]
Wheat
is
tough
to
sequence.
It’s
gone
through
multiple
hybridizations,
making
its
genome
five times larger than a human one. Plus there are
many redundancies: more
than
80
percent
of
the
genome
is
made
of
repeated
DNA
sequences.
So
the
typical
whole-genome
shotgun
approach
—
breaking
genomes
into
segments
and
then
reassembling them
—doesn’t
work for wheat.
Instead,
an
international
consortium
devised
another
strategy,
involving
physically
mapping
individual chromosomes and chromosome
arms.
One paper
details a draft of the entire genome of bread
wheat. Another identifies all
the genes
on the largest of the plant’s 21 chromosomes. Some
75,000 genes have been
mapped.
The
methods
in
the
second
paper
will
help
scientists
map
the
remaining
chromosomes. They say it should take
another three years.
Knowing exactly which genes are
responsible for talents such as tolerating drought
or
improving yields should allow
researchers to mine the genome and to quickly
produce
new and better wheat varieties
to bring us our daily bread.
—
Cynthia
Graber
5.
Supercooled
Organs Could Stretch Time to Transplant
Liver transplant time from human donor
to patient is limited to 12 hours, but rats that
got livers specially stored for three
days were going strong three months later. Cynthia
Graber reports
If you need a new liver,
doctors have about twelve hours to transport it
from a donor.
That ticking clock
severely limits the ability of doctors to get
organs to patients.
Now
researchers
have
demonstrated
a
method
that
kept
rat
livers
viable
up
to
four
days.
The
scientists
lowered
the
livers
to
below
freezing
temperatures,
while
flooding
the
tissue with antifreeze
chemicals to prevent the formation of damaging ice
crystals.
But
such
cooling
alone
is
not
sufficient,
due
in
part
to
the
liver’s
wide
variety
of
cell
types and functions. So the researchers
also used machine perfusion: as the livers were
cooled
they
were
flushed
with
solutions
that
kept
them
operational.
They
were
perfused again as they
were brought back to above-freezing
temps.
All the
rats that were implanted with 3-day-old livers
survived for three months. Nearly
60
percent of the rats with four-day-old livers
survived. In contrast, no rats that received
3-
and
4-day-old
livers
preserved
by
currently
used
methods
survived.
[Tim
A.
Berendsen
et
al,
Supercooling
enables
long-term
transplantation
survival
following
4
days of liver
preservation, in Nature Medicine]
This work is an early step
toward creating a system that could work in
humans, which
would dramatically
improve the chances of getting organs to people
who desperately
need them.
—
Cynthia
Graber