1,703 research outputs found
Functional Convergence of Thalamic and Intrinsic Projections to Cortical Layers 4 and 6
Ascending sensory information is conveyed from the thalamus to layers 4 and 6 of the
sensory cortical areas. Interestingly, receptive field properties of cortical layer-6 neurons
differ from those in layer 4. Do such differences reflect distinct inheritance patterns from
the thalamus, or are they derived instead from local cortical circuits? To distinguish between
these possibilities, we utilized in vitro slice preparations containing the thalamo-cortical
pathways of the auditory and somatosensory systems. Responses from neurons in layers 4
and 6 that resided in the same column were recorded using whole-cell patch clamp. Laserscanning photostimulation via uncaging of glutamate in the thalamus and cortex was used to
map the functional topography of thalamo-cortical and intracortical inputs to each layer. In
addition, we assessed the functional divergence of thalamo-cortical inputs by optical imaging
of flavoprotein autofluorescence. We found that the thalamo-cortical inputs to layers 4 and
6 originated from the same thalamic domain, but the intracortical projections to the same
neurons differed dramatically. Our results suggest that the intracortical projections, rather
than the thalamic inputs, to each layer contribute more to the differences in their receptive
field propertiesВисхідний потік сенсорної інформації передається з таламуса до шарів 4 та 6 сенсорних кортикальних зон. Цікавим є
те, що властивості рецептивних полів у нейронів кортикального шару 6 є відмінними від таких у шарі 4. Чи відображають дані відмінності специфічні природжені патерни таламічних зв’язків або вони зумовлені специфікою локальних
кортикальних нейронних мереж? Щоб зробити вибір між такими можливостями, ми використали слайсові препарати in vitro, котрі вміщували таламо-кортикальні шляхи слухової
та соматосенсорної систем. Застосовуючи методику петчклемп у конфігурації «ціла клітина», ми відводили відповіді нейронів шарів 4 та 6, розташованих в одній і тій самій
кортикальній колонці. Для отримання карт функціональної
топографії таламо-кортикальних та інтракортикальних входів, до кожного із шарів ми використовували методику лазерної скануючої стимуляції, що забезпечувала вивільнення глутамату в таламусі та корі. Окрім того, ми оцінювали
функціональну дивергенцію таламо-кортикальних входів за
допомогою візуалізації аутофлуоресценції флавопротеїнів.
Було виявлено, що таламо-кортикальні входи до шарів 4 та
6 походили від ідентичних таламічних регіонів, тоді як інтракортикальні проекції до одних і тих самих нейронів значно відрізнялися. Наші результати примушують думати, що
саме інтракортикальні проекції того або іншого шару, а не
таламічні входи в більшій мірі визначають відмінності відповідних рецептивних полів у згаданих шарах
Forest harvesting impacts on microclimate conditions and sediment transport activities in a humid periglacial environment
Sediment transport activities in periglacial environments
are controlled by microclimate conditions (i.e., air and ground temperatures,
throughfall), which are highly affected by vegetation cover. Thus, there is
the possibility that forest harvesting, the most dramatic change to
vegetation cover in mountain areas, may severely impact sediment transport
activities in periglacial areas (i.e., soil creep, dry ravel). In this study,
we investigated changes in sediment transport activities following forest
harvesting in steep artificial forests located in a humid periglacial area of
the southern Japanese Alps. In the southern Japanese Alps, rainfall is
abundant in summer and autumn, and winter air temperatures frequently rise
above and fall below 0∘. Our monitoring by time lapse cameras
revealed that gravitational transport processes (e.g., frost creep and dry
ravel) dominate during the freeze–thaw season, while rainfall-induced
processes (surface erosion and soil creep) occur during heavy rainfall
seasons. Canopy removal by forest harvesting increased the winter diurnal
ground surface temperature range from 2.7 to 15.9 ∘C. Forest
harvesting also increased the diurnal range of net radiation and ground
temperature, and decreased the duration of snow cover. Such changes in the
microclimate conditions altered the type of winter soil creep from frost
creep to diurnal needle-ice creep. Winter creep velocity of ground surface
sediment in the harvested site (> 2 mm day−1 on the days
with frost heave) was significantly higher than that in the non-harvested
site (generally < 1 mm day−1). Meanwhile, sediment flux on
the hillslopes, as observed by sediment traps, decreased in the harvested
site. Branches of harvested trees left on the hillslopes captured sediment
moving downslope. In addition, the growth of understories after harvesting
possibly reduced surface erosion. Consequently, removal of the forest canopy
by forest harvesting directly impacts the microclimate conditions (i.e.,
diurnal range of ground temperature and net radiation, duration of snow
cover) and increases frequency and velocity of periglacial soil creep, while
sediment flux on hillslopes is decreased by branches left on the hillslopes
and recovery of understories. The impact of forest harvesting on sediment
transport activity is seasonally variable in humid periglacial areas, because
microclimate conditions relevant to both freeze–thaw processes and
precipitation-induced processes control sediment transport.</p
Search for exotic neutrino-electron interactions using solar neutrinos in XMASS-I
We have searched for exotic neutrino-electron interactions that could be
produced by a neutrino millicharge, by a neutrino magnetic moment, or by dark
photons using solar neutrinos in the XMASS-I liquid xenon detector. We observed
no significant signals in 711 days of data. We obtain an upper limit for
neutrino millicharge of 5.410 at 90\% confidence level
assuming all three species of neutrino have common millicharge. We also set
flavor dependent limits assuming the respective neutrino flavor is the only one
carrying a millicharge, for , for , and for .
These limits are the most stringent yet obtained from direct measurements. We
also obtain an upper limit for the neutrino magnetic moment of
1.810 Bohr magnetons. In addition, we obtain upper limits for
the coupling constant of dark photons in the model of
1.310 if the dark photon mass is 1 MeV,
and 8.810 if it is 10 MeV
Flowering Times of Wild Arabidopsis Accessions From Across Norway Correlate With Expression Levels of FT, CO, and FLC Genes
Temperate species often require or flower most rapidly in the long daylengths, or photoperiods, experienced in summer or after prolonged periods of cold temperatures, referred to as vernalization. Yet, even within species, plants vary in the degree of responsiveness to these cues. In Arabidopsis thaliana, CONSTANS (CO) and FLOWERING LOCUS C (FLC) genes are key to photoperiod and vernalization perception and antagonistically regulate FLOWERING LOCUS T (FT) to influence the flowering time of the plants. However, it is still an open question as to how these genes vary in their interactions among wild accessions with different flowering behaviors and adapted to different microclimates, yet this knowledge could improve our ability to predict plant responses in variable natural conditions. To assess the relationships among these genes and to flowering time, we exposed 10 winter-annual Arabidopsis accessions from throughout Norway, ranging from early to late flowering, along with two summer-annual accessions to 14 weeks of vernalization and either 8- or 19-h photoperiods to mimic Norwegian climate conditions, then assessed gene expression levels 3-, 5-, and 8-days post vernalization. CO and FLC explained both FT levels and flowering time (days) but not rosette leaf number at flowering. The correlation between FT and flowering time increased over time. Although vernalization suppresses FLC, FLC was high in the late-flowering accessions. Across accessions, FT was expressed only at low FLC levels and did not respond to CO in the late-flowering accessions. We proposed that FT may only be expressed below a threshold value of FLC and demonstrated that these three genes correlated to flowering times across genetically distinct accessions of Arabidopsis
Specific-heat study of superconducting and normal states in FeSe1-xTex (0.6<=x<=1) single crystals: Strong-coupling superconductivity, strong electron-correlation, and inhomogeneity
The electronic specific heat of as-grown and annealed single-crystals of
FeSe1-xTex (0.6<=x<=1) has been investigated. It has been found that annealed
single-crystals with x=0.6-0.9 exhibit bulk superconductivity with a clear
specific-heat jump at the superconducting (SC) transition temperature, Tc. Both
2Delta_0/kBTc [Delta_0: the SC gap at 0 K estimated using the single-band BCS
s-wave model] and Delta C/(gamma_n-gamma_0)Tc [Delta C$: the specific-heat jump
at Tc, gamma_n: the electronic specific-heat coefficient in the normal state,
gamma_0: the residual electronic specific-heat coefficient at 0 K in the SC
state] are largest in the well-annealed single-crystal with x=0.7, i.e., 4.29
and 2.76, respectively, indicating that the superconductivity is of the strong
coupling. The thermodynamic critical field has also been estimated. gamma_n has
been found to be one order of magnitude larger than those estimated from the
band calculations and increases with increasing x at x=0.6-0.9, which is
surmised to be due to the increase in the electronic effective mass, namely,
the enhancement of the electron correlation. It has been found that there
remains a finite value of gamma_0 in the SC state even in the well-annealed
single-crystals with x=0.8-0.9, suggesting an inhomogeneous electronic state in
real space and/or momentum space.Comment: 22 pages, 1 table, 6 figures, Version 2 has been accepted for
publication in J. Phys. Soc. Jp
MR Imaging-Based Correction for Partial Volume Effect Improves Detectability of Intractable Epileptogenic Foci on Iodine 123 Iomazenil Brain SPECT Images: An Extended Study with a Larger Sample Size
BACKGROUND AND PURPOSE: It has been suggested, on the basis of a previous pilot study conducted in a small number of patients, that MR imaging-based PVE correction in I-123 iomazenil brain SPECT improves the detectability of cortical epileptogenic foci. In the present study, we performed an investigation by using a larger sample size to establish the effectiveness of the PVE correction and to conduct a detailed evaluation based on the histologic classification of lesions
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