The principle of temperature-dependent gating in cold- and heat-sensitive TRP channels

The mammalian sensory system is capable of discriminating thermal stimuli ranging from noxious cold to noxious heat. Principal temperature sensors belong to the TRP cation channel family, but the mechanisms underlying the marked temperature sensitivity of opening and closing ('gating') of these channels are unknown. Here we show that temperature sensing is tightly linked to voltage-dependent gating in the cold-sensitive channel TRPM8 and the heat-sensitive channel TRPV1. Both channels are activated upon depolarization, and changes in temperature result in graded shifts of their voltage-dependent activation curves. The chemical agonists menthol (TRPM8) and capsaicin (TRPV1) function as gating modifiers, shifting activation curves towards physiological membrane potentials. Kinetic analysis of gating at different temperatures indicates that temperature sensitivity in TRPM8 and TRPV1 arises from a tenfold difference in the activation energies associated with voltage-dependent opening and closing. Our results suggest a simple unifying principle that explains both cold and heat sensitivity in TRP channels.     

Heat activation of TRPM5 underlies thermal sensitivity of sweet taste

TRPM5, a cation channel of the TRP superfamily, is highly expressed in taste buds of the tongue, where it has a key role in the perception of sweet, umami and bitter tastes. Activation of TRPM5 occurs downstream of the activation of G-protein-coupled taste receptors and is proposed to generate a depolarizing potential in the taste receptor cells. Factors that modulate TRPM5 activity are therefore expected to influence taste. Here we show that TRPM5 is a highly temperature-sensitive, heat-activated channel: inward TRPM5 currents increase steeply at temperatures between 15 and 35 degrees C. TRPM4, a close homologue of TRPM5, shows similar temperature sensitivity. Heat activation is due to a temperature-dependent shift of the activation curve, in analogy to other thermosensitive TRP channels. Moreover, we show that increasing temperature between 15 and 35 degrees C markedly enhances the gustatory nerve response to sweet compounds in wild-type but not in Trpm5 knockout mice. The strong temperature sensitivity of TRPM5 may underlie known effects of temperature on perceived taste in humans, including enhanced sweetness perception at high temperatures and 'thermal taste', the phenomenon whereby heating or cooling of the tongue evoke sensations of taste in the absence of tastants.     

The menthol receptor TRPM8 is the principal detector of environmental cold

Sensory nerve fibres can detect changes in temperature over a remarkably wide range, a process that has been proposed to involve direct activation of thermosensitive excitatory transient receptor potential (TRP) ion channels. One such channel--TRP melastatin 8 (TRPM8) or cold and menthol receptor 1 (CMR1)--is activated by chemical cooling agents (such as menthol) or when ambient temperatures drop below approximately 26 degrees C, suggesting that it mediates the detection of cold thermal stimuli by primary afferent sensory neurons. However, some studies have questioned the contribution of TRPM8 to cold detection or proposed that other excitatory or inhibitory channels are more critical to this sensory modality in vivo. Here we show that cultured sensory neurons and intact sensory nerve fibres from TRPM8-deficient mice exhibit profoundly diminished responses to cold. These animals also show clear behavioural deficits in their ability to discriminate between cold and warm surfaces, or to respond to evaporative cooling. At the same time, TRPM8 mutant mice are not completely insensitive to cold as they avoid contact with surfaces below 10 degrees C, albeit with reduced efficiency. Thus, our findings demonstrate an essential and predominant role for TRPM8 in thermosensation over a wide range of cold temperatures, validating the hypothesis that TRP channels are the principal sensors of thermal stimuli in the peripheral nervous system.     

TRPV3 is a temperature-sensitive vanilloid receptor-like protein

Vanilloid receptor-1 (VR1, also known as TRPV1) is a thermosensitive, nonselective cation channel that is expressed by capsaicin-sensitive sensory afferents and is activated by noxious heat, acidic pH and the alkaloid irritant capsaicin. Although VR1 gene disruption results in a loss of capsaicin responses, it has minimal effects on thermal nociception. This and other experiments--such as those showing the existence of capsaicin-insensitive heat sensors in sensory neurons--suggest the existence of thermosensitive receptors distinct from VR1. Here we identify a member of the vanilloid receptor/TRP gene family, vanilloid receptor-like protein 3 (VRL3, also known as TRPV3), which is heat-sensitive but capsaicin-insensitive. VRL3 is coded for by a 2,370-base-pair open reading frame, transcribed from a gene adjacent to VR1, and is structurally homologous to VR1. VRL3 responds to noxious heat with a threshold of about 39 degrees C and is co-expressed in dorsal root ganglion neurons with VR1. Furthermore, when heterologously expressed, VRL3 is able to associate with VR1 and may modulate its responses. Hence, not only is VRL3 a thermosensitive ion channel but it may represent an additional vanilloid receptor subunit involved in the formation of heteromeric vanilloid receptor channels.     

用循环热处理细化铸造TiAl基合金的显微组织

设计了一种新的循环热处理工艺,并用正交设计试验（Ｌ１６（４５））研究了各热处理工艺参数,即加热速度、保温温度、保温时间、冷却速度和循环次数对铸造ＴｉＡｌ基合金显微组织和显微硬度（ＨＶ５）的影响．结果表明：循环热处理工艺均能不同程度地提高显微硬度,提高的最大幅度达４０％;各因素的影响按大小排列依次为加热速度,保温时间、保温温度、冷却速度、循环次数．利用循环热处理可获得不同类型的显微组织．在正交试验的基础上确定了优化的热处理工艺,并用它获得了细小的显微组织．     

破解人类感知之谜

 戴维·朱利叶斯和阿尔登·帕塔普蒂安因发现TRPV1、TRPM8离子蛋白通道和PIEZO基因，“揭开了人类温度和触觉感受器的‘神秘面纱’”，荣获2021年诺贝尔生理学或医学奖。通过回顾2位科学家的成长经历、科研历程及在人类感知领域的研究成果，探讨了“痛感”对人体的利弊，分析了新科学仪器的应用与基础科研的关系。     

Anandamide and arachidonic acid use epoxyeicosatrienoic acids to activate TRPV4 channels

TRPV4 is a widely expressed cation channel of the 'transient receptor potential' (TRP) family that is related to the vanilloid receptor VR1 (TRPV1). It functions as a Ca2+ entry channel and displays remarkable gating promiscuity by responding to both physical stimuli (cell swelling, innoxious heat) and the synthetic ligand 4alphaPDD. An endogenous ligand for this channel has not yet been identified. Here we show that the endocannabinoid anandamide and its metabolite arachidonic acid activate TRPV4 in an indirect way involving the cytochrome P450 epoxygenase-dependent formation of epoxyeicosatrienoic acids. Application of 5',6'-epoxyeicosatrienoic acid at submicromolar concentrations activates TRPV4 in a membrane-delimited manner and causes Ca2+ influx through TRPV4-like channels in vascular endothelial cells. Activation of TRPV4 in vascular endothelial cells might therefore contribute to the relaxant effects of endocannabinoids and their P450 epoxygenase-dependent metabolites on vascular tone.     

Spider toxins activate the capsaicin receptor to produce inflammatory pain

Bites and stings from venomous creatures can produce pain and inflammation as part of their defensive strategy to ward off predators or competitors. Molecules accounting for lethal effects of venoms have been extensively characterized, but less is known about the mechanisms by which they produce pain. Venoms from spiders, snakes, cone snails or scorpions contain a pharmacopoeia of peptide toxins that block receptor or channel activation as a means of producing shock, paralysis or death. We examined whether these venoms also contain toxins that activate (rather than inhibit) excitatory channels on somatosensory neurons to produce a noxious sensation in mammals. Here we show that venom from a tarantula that is native to the West Indies contains three inhibitor cysteine knot (ICK) peptides that target the capsaicin receptor (TRPV1), an excitatory channel expressed by sensory neurons of the pain pathway. In contrast with the predominant role of ICK toxins as channel inhibitors, these previously unknown 'vanillotoxins' function as TRPV1 agonists, providing new tools for understanding mechanisms of TRP channel gating. Some vanillotoxins also inhibit voltage-gated potassium channels, supporting potential similarities between TRP and voltage-gated channel structures. TRP channels can now be included among the targets of peptide toxins, showing that animals, like plants (for example, chilli peppers), avert predators by activating TRP channels on sensory nerve fibres to elicit pain and inflammation.     

Effects of zonal perturbations of sea surface temperature on tropical equilibrium states: A cloud-resolving modeling study

The effects of zonal perturbations of sea surface temperature （SST） on tropical equilibrium states are investigated based on a series of two-dimensional cloud-resolving simulations with imposed zero vertical velocity, constant zonal wind, and a zonal model domain of 768 km. Four experiments with zonal SST perturbations of wavenumbers 1 （C1）, 2 （C2）, 4 （C3）, and 8 （C4） are compared to a control experiment with zonally uniform SST （CO）. The 40-day integrations show that the temperatures reach quasi-equilibrium states with distinct differences. C1 and C2 produce warmer equilibrium states whereas C3 and C4 generate colder equilibrium states than CO does. The heat budgets in the five experiments are analyzed. Compared to CO, less IR cooling over smaller clear-sky regions in C1 and more condensational heating in C2 are responsible for warmer equilibrium states. A reduced condensational heating leads to the cold equilibrium state in C3. The interaction between convective systems in C4 causes a decrease of condensational heating, which accounts for the cold equilibrium state.     

Effects of zonal perturbations of sea surface temperature on tropical equilibrium states: A cloud-resolving modeling study

The effects of zonal perturbations of sea surface temperature (SST) on tropical equilibrium states are investigated based on a series of two-dimensional cloud-resolving simulations with imposed zero vertical velocity, constant zonal wind, and a zonal model domain of 768 km. Four experiments with zonal SST perturbations of wavenumbers 1 (C1), 2 (C2), 4 (C3), and 8 (C4) are compared to a control experiment with zonally uniform SST (C0). The 40-day integrations show that the temperatures reach quasi-equilibrium states with distinct differences. C1 and C2 produce warmer equilibrium states whereas C3 and C4 generate colder equilibrium states than C0 does. The heat budgets in the five experiments are analyzed. Compared to C0, less IR cooling over smaller clear-sky regions in C1 and more condensational heating in C2 are responsible for warmer equilibrium states. A reduced condensational heating leads to the cold equilibrium state in C3. The interaction between convective systems in C4 causes a decrease of condensational heating, which accounts for the cold equilibrium state.     

Transition-metal-based magnetic refrigerants for room-temperature applications.

Magnetic refrigeration techniques based on the magnetocaloric effect (MCE) have recently been demonstrated as a promising alternative to conventional vapour-cycle refrigeration. In a material displaying the MCE, the alignment of randomly oriented magnetic moments by an external magnetic field results in heating. This heat can then be removed from the MCE material to the ambient atmosphere by heat transfer. If the magnetic field is subsequently turned off, the magnetic moments randomize again, which leads to cooling of the material below the ambient temperature. Here we report the discovery of a large magnetic entropy change in MnFeP0.45As0.55, a material that has a Curie temperature of about 300 K and which allows magnetic refrigeration at room temperature. The magnetic entropy changes reach values of 14.5 J K-1 kg-1 and 18 J K-1 kg-1 for field changes of 2 T and 5 T, respectively. The so-called giant-MCE material Gd5Ge2Si2 (ref. 2) displays similar entropy changes, but can only be used below room temperature. The refrigerant capacity of our material is also significantly greater than that of Gd (ref. 3). The large entropy change is attributed to a field-induced first-order phase transition enhancing the effect of the applied magnetic field.     

热电热泵在非设计工况条件下的性能分析

 采用直流电源模拟太阳能电池板输出不稳定电压驱动热电热泵工作,通过实验测试研究了在连续长时间工作、电压跳跃变化和极限电压工况下,热电热泵冷端温度T_c、热端温度T_h、冷热端温差T_d的变化对其制冷/制热的性能系数（COP）的影响。结果表明,在适宜的电压范围内,热电热泵的制冷速度快、工作性能稳定且能够长时间连续工作,而制热效果明显优于制冷效果,制热效率（E_h）平均高于制冷效率（E_c）约0.8;热电热泵的最佳工作电压区间为2~4 V,此时的冷端温度低、制冷量大、COP 值在理想范围(E_c=0.87~1.89,E_h=1.75~2.75);随着工作电压增高,热电热泵的冷热端温差增大,COP 值减小,当电压大于8V 后,冷热端温差大于45℃,COP 值降至最小,工作性能较差。     

蓄热体与换热时间的数值模拟分析

运用ANSYS中的Fluent模块功能,从流体初始速度、蓄热体结构数值以及换向周期等几个因素对其换热性能的影响进行了数值模拟,可得到蓄热室内部和面壁在蓄热和冷却期间的温度云图.结果表明:蓄热体换热过程中温度随时间变化的规律;运用数值分析的方法对蓄热室内部从初始状态到稳态工作过程进行了模拟,得到并分析了在工作运行中烟气和空气出口温度的改变状况;分析稳态时的加热和冷却末期时间段蓄热体内部温度情况.研究结果为进一步探究换热机制提供了一定的科学依据.     

内可逆Carnot制冷机和热泵输出率密度分析与优化

以内可逆Carnot循环的输出率密度(对循环最大体积平均的循环输出率),即Carnot制冷机的制冷率密度和Carnot热泵的供热率密度作为热力性能指标,分别对内可逆Carnot制冷机和热泵进行分析与优化,导出了最佳换热器面积分配关系式,通过数值计算分析了热源温比对输出率密度与性能系数关系的影响。结果表明,考虑循环体积后,Carnot制冷机的制冷率密度与制冷系数特性关系呈抛物线型,这与传统分析中单调递减的制冷率与制冷系数特性关系完全不同;Carnot热泵的供热率密度与供热系数特性关系呈抛物线型,也与传统分析得到的单调递减的供热率与供热系数特性关系不同。     

光伏辐射板型PV/T系统的电热冷性能

提出了一种基于单晶硅太阳能电池的电热冷联产光伏辐射板,将起集散热作用的辐射板与单晶硅光电池组件耦合,通过辐射板管路内流体循环,降低电池工作温度,一方面提高电池发电效率,同时回收利用余热;另一方面,夜间通过辐射制冷方式,获得冷量,从而实现电热冷联产。通过实验测试分析,光伏辐射板同比PV组件发电效率可提高8%～16%,且集热效率达到45%左右,制冷能力为40～80 W/m 2。     

CaCl2-BaCl2-NH3二级吸附式制冷系统及其制冷性能与仿真

在低于100 °C热源、高于30 °C冷凝温度的条件下，为了获得-15 °C的冷冻工况，采用二级解吸过程设计了氯化钙/氯化钡吸附氨的吸附制冷系统，并对氯化钙/氯化钡工质对的吸附性能参数进行测试，由其性能数据拟合而得到吸附与解吸曲线、耦合吸附与解吸方程和传热方程，并建立系统模型进行仿真.结果表明，该系统可以利用85 °C的低温热源，在30 °C的冷凝温度条件下获得-15 °C的制冷温度，并达到2.62 kW的制冷功率.     

相变潜热测量的扫描速率依赖性：RbNo3在结构相变中的热耗散

用差分扫描量热仪(DSC)测量了硝酸铷在380K至460K温度范围内升、降温过程中的三角(α)立方(β)结构相变。所用的扫描速率为1.25～40K/min。结果表明,升温相变的潜热(吸热)大于降温相变的潜热(放热),其差值△Q(Cal/g)随扫描速率的增大而增大。用结构相变中的热耗散对实验结果进行了解积。因此,可以用本文的方法来研究一级相变过程的不可逆耗散。     

昆仑白玉的高温原位X射线衍射实验研究

本文在28℃-1150℃温区对昆仑白玉进行高温原位X射线衍射实验,研究了升温和降温过程的物相变化,结果表明昆仑碧玉在常温下主相为Ca2Mg5Si8O22（OH）2,晶格参数a=9.818,b=18.047,c=5.275,α=90°,β=104.6°,γ=90°,空间群为C2/m,属于单斜晶系;升温过程中在800℃时少量杂质白云石（CaMg（CO3）2）分解,少量杂质滑石（Mg3[Si4O10]（OH）2）在900℃-1050℃分解,1000℃左右透闪石结构被破坏,存在形成CaMgSi2O6的两种机制,直到1150℃阳起石结构完全被破坏,最终产物中主要是透辉石CaMgSi2O6,还有少量CaSiO3,MgSiO3;降温过程的图谱表明这种高温相变是不可逆的.     

工业喷嘴雾化冷却特性测试方法

基于非稳态导热原理,设计并开发了一套喷嘴喷雾冷却特性测试实验装置。将Q215钢种试样加热并恒定表面温度,然后通过对表面进行喷雾强制冷却,连续采集并保存冷却过程中试件不同测点的温度变化。通过Matlab与VC6.0接口编程,离线拟合密度、比热容及导热系数等热物性参数与温度拟合方程以及不同测点温度与时间的拟合方程。结合测试的拟合方程,对非稳态导热方程进行离散处理间接测量表面的传热系数,进而评价喷嘴冷却特性。通过系列现场测试实验,测试喷雾冷却过程中表面温度,水流密度及喷水压力等条件下表面的传热系数,实验结果真实反映了喷雾冷却条件下喷嘴的冷却特性,并表明该方法可行,能实现喷嘴冷却特性测试及喷嘴性能评价。     

A TRPV family ion channel required for hearing in Drosophila

The many types of insect ear share a common sensory element, the chordotonal organ, in which sound-induced antennal or tympanal vibrations are transmitted to ciliated sensory neurons and transduced to receptor potentials. However, the molecular identity of the transducing ion channels in chordotonal neurons, or in any auditory system, is still unknown. Drosophila that are mutant for NOMPC, a transient receptor potential (TRP) superfamily ion channel, lack receptor potentials and currents in tactile bristles but retain most of the antennal sound-evoked response, suggesting that a different channel is the primary transducer in chordotonal organs. Here we describe the Drosophila Nanchung (Nan) protein, an ion channel subunit similar to vanilloid-receptor-related (TRPV) channels of the TRP superfamily. Nan mediates hypo-osmotically activated calcium influx and cation currents in cultured cells. It is expressed in vivo exclusively in chordotonal neurons and is localized to their sensory cilia. Antennal sound-evoked potentials are completely absent in mutants lacking Nan, showing that it is an essential component of the chordotonal mechanotransducer.