The time-resolved strain and temperature profiles of magnetron-sputtered pseudoelastic TiNi films of 20 mu m thickness are investigated during tensile stress cycling for different strain rates. Based ...on simultaneous infrared thermography and digital image correlation, a good correlation between the evolution of temperature profiles and the local formation and propagation of Lueders-like strain bands is observed. The evolution of temperature profiles can be quantitatively described by a phenomenological Tanaka-type model of the martensitic transformation combined with a heat transfer model taking into account the local interaction between transformed and untransformed regions in the transformation kinetics. The investigated film samples exhibit an undercooling of -16K upon mechanical unloading under adiabatic conditions at a strain rate of 0.2s-1. A coefficient of performance of 7.7 is determined. Due to the high surface-to-volume ratio, the films show fast heat exchange in air of the order of 1.5s. Based on these results, the prospects of SMA film-based elastocaloric cooling are discussed.
Optical modulators encode electrical signals to the optical domain and thus constitute a key element in high-capacity communication links. Ideally, they should feature operation at the highest speed ...with the least power consumption on the smallest footprint, and at low cost. Unfortunately, current technologies fall short of these criteria. Recently, plasmonics has emerged as a solution offering compact and fast devices. Yet, practical implementations have turned out to be rather elusive. Here, we introduce a 70 GHz all-plasmonic Mach-Zehnder modulator that fits into a silicon waveguide of 10 μm length. This dramatic reduction in size by more than two orders of magnitude compared with photonic Mach-Zehnder modulators results in a low energy consumption of 25 fJ per bit up to the highest speeds. The technology suggests a cheap co-integration with electronics.
Cortical networks spontaneously fluctuate between persistently active Up states and quiescent Down states. The Up states are maintained by recurrent excitation within local circuits, and can be ...turned on and off by synaptic input. GABAergic inhibition is believed to be important for stabilizing such persistent activity by balancing the excitation, and could have an additional role in terminating the Up state. Here, we report that GABA
A
and GABA
B
receptor-mediated inhibition have distinct and complementary roles in balancing and terminating persistent activity. In a model of Up–Down states expressed in slices of rat entorhinal cortex, the GABA
A
receptor antagonist, gabazine (50–500 n
m
), concentration-dependently decreased Up state duration, eventually leading to epileptiform bursts. In contrast, the GABA
B
receptor antagonist, CGP55845 (50 n
m
to 1 μ
m
), increased the duration of persistent network activity, and prevented stimulus-induced Down state transitions. These results suggest that while GABA
A
receptor-mediated inhibition is necessary for balancing persistent activity, activation of GABA
B
receptors contributes to terminating Up states.
The macroscopic properties of gels arise from their slow dynamics and load-bearing network structure, which are exploited by nature and in numerous industrial products. However, a link between these ...structural and dynamical properties has remained elusive. Here we present confocal microscopy experiments and simulations of gel-forming colloid-polymer mixtures. They reveal that gel formation is preceded by continuous and directed percolation. Both transitions lead to system-spanning networks, but only directed percolation results in extremely slow dynamics, ageing and a shrinking of the gel that resembles synaeresis. Therefore, dynamical arrest in gels is found to be linked to a structural transition, namely directed percolation, which is quantitatively associated with the mean number of bonded neighbours. Directed percolation denotes a universality class of transitions. Our study hence connects gel formation to a well-developed theoretical framework, which now can be exploited to achieve a detailed understanding of arrested gels.
This systematic review and meta-analysis set out to determine the effect of dynamic resistance exercise (DRT) on areal bone mineral density (aBMD) in postmenopausal women and derive evidence-based ...recommendations for optimized training protocols. A systematic review of the literature according to the PRISMA statement included (a) controlled trials, (b) of isolated DRT with at least one exercise and one control group, (c) with intervention durations ≥ 6 months, (d) aBMD assessments at lumbar spine or proximal femur, (e) in cohorts of postmenopausal women. We searched eight electronic databases up to March 2019 without language restrictions. The meta-analysis was performed using a random-effects model. Standardized mean differences (SMD) for BMD changes at lumbar spine (LS), femoral neck (FN), and total hip (TH) were defined as outcome measures. Moderators of the exercise effects, i.e., “intervention length,” “type of DRT,” “training frequency,” “exercise intensity,” and “exercise volume,” were addressed by sub-group analyses. The study was registered in the international prospective register of systematic reviews (PROSPERO) under ID: CRD42018095097. Seventeen articles with 20 exercise and 18 control groups were eligible. SMD average is 0.54 (95% CI 0.22–0.87) for LS-BMD, 0.22 (0.07–0.38) for FN-BMD, and 0.48 (0.22–0.75) for TH-BMD changes (all
p
≤ 0.015). While sub-group analysis for FN-BMD revealed no differences within categories of moderators, lower training frequency (< 2 sessions/week) resulted in significantly higher BMD changes at LS and TH compared to higher training frequency (≥ 2 sessions/week). Additionally, free weight training was significantly superior to DRT devices for improving TH-BMD. This work provided further evidence for significant, albeit only low–moderate, effects of DRT on LS-, FN-, and TH-BMD. Unfortunately, sub-analysis results did not allow meaningful exercise recommendations to be derived. This systematic review and meta-analysis observed a significant low–moderate effect of dynamic resistance exercise on bone mineral density changes in postmenopausal women. However, sub-group analyses focusing on exercise characteristics found no results that enable the derivation of meaningful exercise recommendations in the area of exercise and osteoporosis prevention or therapy.
Summary
The EFOPS trial clearly established the positive effect of long-term exercise on clinical low-trauma fractures in postmenopausal women at risk. Bearing in mind that the complex anti-fracture ...exercise protocols also affect a large variety of diseases of increased age, we strongly encourage older adults to perform multipurpose exercise programs.
Introduction
Physical exercise may be an efficient option for autonomous fracture prevention during increasing age. The aim of the study was to evaluate the effect of exercise on clinical overall fracture incidence and bone mineral density (BMD) in elderly subjects at risk.
Methods
In 1998 initially, 137 early-postmenopausal, osteopenic women living in Erlangen-Nuremberg, Germany, were included in the EFOPS trial. Subjects of the exercise group (EG;
n
= 86) conducted two supervised group and two home exercise sessions/week while the control group (CG;
n
= 51) was requested to maintain their physical activity. Primary study endpoints were clinical overall low-trauma fractures determined by questionnaires, structured interviews, and BMD at the lumbar spine and femoral neck assessed by dual-energy X-ray absorptiometry.
Results
In 2014, 105 subjects (EG:
n
= 59 vs. CG:
n
= 46) representing 1680 participant-years were included in the 16-year follow-up analysis. Risk ratio in the EG for overall low-trauma fractures was 0.51 (95 % confidence interval (95 % CI) 0.23 to 0.97,
p
= .046), rate ratio was 0.42 (95 % CI 0.20 to 0.86,
p
= .018). Based on comparable baseline values, lumbar spine (MV −1.5 %, 95 % CI −0.1 to −2.8 vs. −5.8 %, −3.3 to −7.2 %) and femoral neck (−6.5 %, −5.2 to −7.7 vs. −9.6 %, −8.2 to 11.1 %) BMD decreased in both groups; however, the reduction was more pronounced in the CG (
p
≤ .001).
Conclusion
This study clearly evidenced the high anti-fracture efficiency of multipurpose exercise programs. Considering furthermore the favorable effect of exercise on most other risk factors of increasing age, we strongly encourage older adults to perform multipurpose exercise programs.
Significance The hippocampus is implicated in memory and spatial navigation. In rodents, in which this bilateral brain structure has been studied extensively, the left and right hippocampi have ...generally been considered functionally equivalent. However, recent work has revealed unexpected asymmetries in the molecular and morphological characteristics of neuronal connections according to brain hemisphere. To investigate whether this left–right difference has implications for hippocampal function, we acutely inhibited activity in an area-specific and genetically-defined population of hippocampal neurons during various behavioral tasks. We found that silencing the CA3 area of the left hippocampus impaired associative spatial long-term memory, whereas the equivalent manipulation in the right hippocampus did not. Thus, our data show that hippocampal long-term memory processing is lateralized in mice.
Left–right asymmetries have likely evolved to make optimal use of bilaterian nervous systems; however, little is known about the synaptic and circuit mechanisms that support divergence of function between equivalent structures in each hemisphere. Here we examined whether lateralized hippocampal memory processing is present in mice, where hemispheric asymmetry at the CA3–CA1 pyramidal neuron synapse has recently been demonstrated, with different spine morphology, glutamate receptor content, and synaptic plasticity, depending on whether afferents originate in the left or right CA3. To address this question, we used optogenetics to acutely silence CA3 pyramidal neurons in either the left or right dorsal hippocampus while mice performed hippocampus-dependent memory tasks. We found that unilateral silencing of either the left or right CA3 was sufficient to impair short-term memory. However, a striking asymmetry emerged in long-term memory, wherein only left CA3 silencing impaired performance on an associative spatial long-term memory task, whereas right CA3 silencing had no effect. To explore whether synaptic properties intrinsic to the hippocampus might contribute to this left–right behavioral asymmetry, we investigated the expression of hippocampal long-term potentiation. Following the induction of long-term potentiation by high-frequency electrical stimulation, synapses between CA3 and CA1 pyramidal neurons were strengthened only when presynaptic input originated in the left CA3, confirming an asymmetry in synaptic properties. The dissociation of hippocampal long-term memory function between hemispheres suggests that memory is routed via distinct left–right pathways within the mouse hippocampus, and provides a promising approach to help elucidate the synaptic basis of long-term memory.
To keep pace with the demands in optical communications, electro-optic modulators should feature large bandwidths, operate across all telecommunication windows, offer a small footprint, and allow for ...CMOS-compatible fabrication to keep costs low. Here, we demonstrate a new ultra-compact plasmonic phase modulator based on the Pockels effect in a nonlinear polymer. The device has a length of only 29 µm and operates at 40 Gbit s-1 . Its modulation frequency response is flat up to 65 GHz and beyond. The modulator has been tested to work across a 120-nm-wide wavelength range centred at 1,550 nm, and is expected to work beyond this range. Its operation has been verified for temperatures up to 85 °C and it is easy to fabricate. To the best of our knowledge, this is the most compact high-speed phase modulator demonstrated to date.
Abnormal accumulation of amyloid β
oligomers (AβO
), a hallmark of Alzheimer's disease, impairs hippocampal theta-nested gamma oscillations and long-term potentiation (LTP) that are believed to ...underlie learning and memory. Parvalbumin-positive (PV) and somatostatin-positive (SST) interneurons are critically involved in theta-nested gamma oscillogenesis and LTP induction. However, how AβO
affects PV and SST interneuron circuits is unclear. Through optogenetic manipulation of PV and SST interneurons and computational modeling of the hippocampal neural circuits, we dissected the contributions of PV and SST interneuron circuit dysfunctions on AβO
-induced impairments of hippocampal theta-nested gamma oscillations and oscillation-induced LTP.
Targeted whole-cell patch-clamp recordings and optogenetic manipulations of PV and SST interneurons during in vivo-like, optogenetically induced theta-nested gamma oscillations in vitro revealed that AβO
causes synapse-specific dysfunction in PV and SST interneurons. AβO
selectively disrupted CA1 pyramidal cells (PC)-to-PV interneuron and PV-to-PC synapses to impair theta-nested gamma oscillogenesis. In contrast, while having no effect on PC-to-SST or SST-to-PC synapses, AβO
selectively disrupted SST interneuron-mediated disinhibition to CA1 PC to impair theta-nested gamma oscillation-induced spike timing-dependent LTP (tLTP). Such AβO
-induced impairments of gamma oscillogenesis and oscillation-induced tLTP were fully restored by optogenetic activation of PV and SST interneurons, respectively, further supporting synapse-specific dysfunctions in PV and SST interneurons. Finally, computational modeling of hippocampal neural circuits including CA1 PC, PV, and SST interneurons confirmed the experimental observations and further revealed distinct functional roles of PV and SST interneurons in theta-nested gamma oscillations and tLTP induction.
Our results reveal that AβO
causes synapse-specific dysfunctions in PV and SST interneurons and that optogenetic modulations of these interneurons present potential therapeutic targets for restoring hippocampal network oscillations and synaptic plasticity impairments in Alzheimer's disease.
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