Sum and difference frequency generation in a valley-photonic-crystal-like topological system.

Nonlinear sum frequency generation (SFG) and difference frequency generation (DFG) are fundamental methods to obtain new light sources for various applications. However, most of the on-chip SFG and DFG are based on conventional resonators, lacking robustness against fabrication defects. Here, we demonstrate topologically protected SFG and DFG in a second-order topological photonic system. The mechanism is based on the nonlinear interaction between three high-Q corner modes inside dual topological band gaps. The frequency matching condition for SFG and DFG is precisely satisfied by designing a valley-photonic-crystal-like topological system, which provides more freedoms to tune the corner modes. The topological SFG and DFG are achieved with high conversion efficiency, and the underlying topological physics is revealed. This work opens up avenues toward topologically protected nonlinear frequency conversion, and can find applications in the fields of on-chip single-photon detections and optical quantum memories with robustness against defects.

Deregulation of the Glymphatic System in Alzheimer's Disease: Genetic and Non-Genetic Factors.

Alzheimer's disease (AD) is the most prevalent form of dementia and is characterized by progressive degeneration of brain function. AD gradually affects the parts of the brain that control thoughts, language, behavior and mental function, severely impacting a person's ability to carry out daily activities and ultimately leading to death. The accumulation of extracellular amyloid-ß peptide (Aß) and the aggregation of intracellular hyperphosphorylated tau are the two key pathological hallmarks of AD. AD is a complex condition that involves both non-genetic risk factors (35%) and genetic risk factors (58-79%). The glymphatic system plays an essential role in clearing metabolic waste, transporting tissue fluid, and participating in the immune response. Both non-genetic and genetic risk factors affect the glymphatic system to varying degrees. The main purpose of this review is to summarize the underlying mechanisms involved in the deregulation of the glymphatic system during the progression of AD, especially concerning the diverse contributions of non-genetic and genetic risk factors. In the future, new targets and interventions that modulate these interrelated mechanisms will be beneficial for the prevention and treatment of AD.

Sesquiterpenoids from Seriphidium transiliense and Their Melanogenic Activity.

A sesquiterpenoid with an unprecedented 5/5/4 tricyclic skeleton (1), a nor-sesquiterpenoid with a rare 6/7 bicyclic skeleton (2), 10 new sesquiterpenoids (3-12), and six known analogues (13-18) were isolated from the whole plants of Seriphidium transiliense. The structures of compounds 1-12 were elucidated by spectroscopic data analysis. Compound 7 showed melanogenic promotion activity in murine melanoma (B16) cells more potent than the positive control used, 8-methoxypsoralen (8-MOP). Further mechanistic studies indicated that compound 7 promotes melanogenesis through activating the transcription of microphthalmia-associated transcription factor (MITF) and tyrosinase family genes in B16 cells. Moreover, compound 7 also inhibited the expression of IFN-γ-chemokine through the JAK/STAT signaling pathway in immortalized human keratinocyte (HaCaT) cells. These results suggest that the sesquiterpenoid 7 shows potential activity for treating vitiligo.

Investigation of corner states in second-order photonic topological insulator.

Recently, higher-order topological insulators have been investigated as a novel topological phase of matter that obey an extended topological bulk-boundary correspondence principle. In this paper, we study the influence of BNN interaction on photonic higher-order corner states. We find both next-nearest-neighbor (NNN) hopping and perfect electric conductor (PEC) boundaries can solely result in two kinds of corner states which are quite different from the traditional "zero-energy" state. To demonstrate this intuitively, we design a novel all-dielectric structure that can effectively shield the influence of NNN couplings while remain the effect of PEC boundaries, so that we can distinguish the contributions from NNN hopping and PEC boundaries. In addition, we also investigate the total contribution on corner states when NNN couplings and PEC boundaries coexist, and some interesting features are revealed. These findings may expand our understanding of the high-order corner modes in a more general framework.

Broad-band, reversible nonreciprocal light transmission based on a single nanocavity.

We present a general yet simple method for achieving broad-band, high-contrast-ratio, and reversible all-optical diodes. The mechanism is based on the controllable photonic transitions inside a nonlinear nanocavity, triggered by only one pulse. We demonstrate that the interaction between the signal, pump pulse, and the cavity mode plays a crucial role in dynamically controlling the nonreciprocal light transmissions. Using this mechanism, we show that the nonreciprocal light transmission can be controllably reversed without changing the signal light's wavelength or power, with a broad operation bandwidth over 7.5nm and a transmission contrast rate over 20dB. This approach provides a promising avenue in flexible manipulation of on-chip all-optical signal processing.

Dynamic tuning of the Q factor in a photonic crystal nanocavity through photonic transitions.

Photonic devices based on a high-Q cavity are commonly constrained by narrow operation bandwidth, slow charging, and releasing speed. Here, we analytically and numerically demonstrate that this limitation can be broken via dynamically tuning the Q factors of a single nanocavity and driving controllable photonic transitions between a low-Q cavity mode and an ultrahigh-Q mode by temporal refractive index modulations inside a multimode cavity. During this dynamic process, the bandwidth of signal light is also reversibly compressed. As a result, the fundamental link between the photon lifetime and the operation bandwidth is broken, and a delay-bandwidth product of ∼76 is achieved, which is far greater than that of the usual optical resonator systems. This approach may pave the way for dynamic control of on-chip all-optical information processing.

Broad-bandwidth, reversible, and high-contrast-ratio optical diode.

Fano resonance is widely used to realize high-contrast nonreciprocal transmission. However, resonance-enhanced all-optical diodes (AOD) are bandwidth-limited, and their transmission rates are normally low, which restricts realistic application. In this Letter, we analytically and numerically demonstrate that this limitation can be overcome once multistability of cascaded nonlinear cavities is appropriately excited. By precisely molding the transiting of the signal light between multistable states, a high-contrast-ratio, high-unidirectional-transmission-rate, and reversal-controllable AOD is achieved with a bandwidth over 2.4 nm, which is about two orders of magnitude wider than the reported results obtained by other methods based on Fano resonances. This approach may pave the way for dynamic control of on-chip all-optical information processing.

Proteomic analysis of halotolerant proteins under high and low salt stress in Dunaliella salina using two-dimensional differential in-gel electrophoresis.

Dunaliella salina, a single-celled marine alga with extreme salt tolerance, is an important model organism for studying fundamental extremophile survival mechanisms and their potential practical applications. In this study, two-dimensional differential in-gel electrophoresis (2D-DIGE) was used to investigate the expression of halotolerant proteins under high (3 M NaCl) and low (0.75 M NaCl) salt concentrations. Matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF/TOF MS) and bioinformatics were used to identify and characterize the differences among proteins. 2D-DIGE analysis revealed 141 protein spots that were significantly differentially expressed between the two salinities. Twenty-four differentially expressed protein spots were successfully identified by MALDI-TOF/TOF MS, including proteins in the following important categories: molecular chaperones, proteins involved in photosynthesis, proteins involved in respiration and proteins involved in amino acid synthesis. Expression levels of these proteins changed in response to the stress conditions, which suggests that they may be involved in the maintenance of intracellular osmotic pressure, cellular stress responses, physiological changes in metabolism, continuation of photosynthetic activity and other aspects of salt stress. The findings of this study enhance our understanding of the function and mechanisms of various proteins in salt stress.

Broad-bandwidth, high-efficiency multiwavelength conversion in a high-Q photonic crystal resonator.

We analytically and numerically demonstrate that multiwavelength conversion can be realized in a high-Q photonic crystal nanocavity. With the help of a dynamic-phase-shift effect induced by bandgap-multireflection, the wavelength conversion efficiency of nearly 100% is achieved for a broad conversion range over several hundreds of nanometers, which is much larger than the reported results obtained by other linear methods (e.g., adiabatic wavelength conversion). This approach may open a way for the study of on-chip ultralow-power optical communications and quantum information processing.

Critical conditions of control light for a silicon-based photonic crystal bistable switching.

In this paper, we investigate the critical conditions of control light for a silicon-based photonic crystal bistable switching. By establishing a time-dependent evolution equation, the critical pump power and pump time of the control light are derived, respectively. It is found that with the increase of the frequency detuning of the incident light, the critical power of the control light will rise, while the corresponding critical time will be shortened. It is also revealed that under the same conditions, the critical total power of the multiple-beam control light is less than the one of the single-beam control light. The theoretical predictions show perfect agreement with the simulation results.

Metabolic alterations in the hamster co-infected with Schistosoma japonicum and Necator americanus.

Co-infection with hookworm and schistosomes is a common phenomenon in sub-Saharan Africa, as well as in parts of South America and southeast Asia. As a first step towards understanding the metabolic response of a hookworm-schistosome co-infection in humans, we investigated the metabolic consequences of co-infection in an animal model, using a nuclear magnetic resonance (NMR)-based metabolic profiling technique, combined with multivariate statistical analysis. Urine and serum samples were obtained from hamsters experimentally infected with 250 Necator americanus infective L(3) and 100 Schistosoma japonicum cercariae simultaneously. In the co-infection model, similar worm burdens were observed as reported for single infection models, whereas metabolic profiles of co-infection represented a combination of the altered metabolite profiles induced by single infections with these two parasites. Consistent differences in metabolic profiles between the co-infected and non-infected control hamsters were observed from 4 weeks p.i. onwards. The predominant metabolic alterations in co-infected hamsters consisted of depletion of amino acids, tricarboxylic acid cycle intermediates (e.g. citrate and succinate) and glucose. Moreover, alterations of a series of gut microbial-related metabolites, such as decreased levels of hippurate, 3-hydroxyphenylpropionic acid, 4-hydroxyphenylpropionic acid and trimethylamine-N-oxide, and increased concentrations of 4-cresol glucuronide and phenylacetylglycine were associated with co-infection. Our results provide a first step towards understanding the metabolic response of an animal host to multiple parasitic infections.

Contralateral 80-280 Hz EEG ripples and hippocampal single unit discharge inhibition in response to acute tetanization of rat right caudate putamen in vivo.

Clinically, 4-8 Hz (or 30-80 Hz) stimulation of the caudate nucleus ceases (or enhances) the neocortical and hippocampal epileptiform activities of the epilepsy patients. Possibly, electric stimulation of the caudate nucleus could produce epilepsy. In order to prove this point we delivered the acute tetanization (60 Hz, 2s, 0.4-0.6 mA) into the rat right caudate putamen nucleus (ATRC) and examined bilateral neocortical EEG and hippocampal unit discharges in vivo. The results demonstrated that: (1) 80-280 Hz EEG ripples could be evoked bilaterally, and more stronger on the contralateral side. And the maximum amplitudes of the power spectra (microV2/Hz) have higher shifting variability among multiple contralateral EEG ripples. (2) The EEG ripples were coupled contralaterally with the hippocampal neuronal firing inhibition. (3) An episode of 10-15 Hz EEG oscillations was ipsilaterally coupled with rhythmic hippocampal neuronal bursts. It suggested that the hemispheric reactions of neocortical EEG and hippocampal neuronal discharges are lateralized in response to the stimulation. It implies that the epileptic network activities were reorganized by the ATRC. Neocortical EEG ripples, called as seizure-like fast oscillations, were repetitively evoked by the ATRC.

[Regulatory network of hippocampal-systemic arterial blood pressure during epileptic network reestablishment].

AIM: To investigate the regulatory network of hippocampal-systemic arterial blood pressure during epileptic network reestablishment. METHODS: 7.2 microg picrotoxin (PTX) was microinjected into the right HPC (RHPC) to induce rat epilepsy. Contralateral hippocampal EEG, single unit discharges, femoral artery blood pressure and ECG were recorded simultaneously. RESULTS: PTX might induce: (1) A resemblance interspike intervals (ISI) spot distribution of long duration neuronal burst and unit after discharges in contralateral HPC. (2) Delayed the initiation time of hippocampal neuronal bursts coupled with arterial blood pressure depression. (3) Hippocampal neuronal burst or unit after discharges coupled complexly with arterial blood pressure depression. (4) Resemblance hippocampal EEG interpeak intervals (IPI) and neuronal firing ISI spot distribution coupled with arterial blood pressure depression. CONCLUSION: During contralateral hippocampal epileptic network reestablishment after microinjection of PTX to the RHPC, the function of the hippocampal-arterial blood pressure regulatory network could be modulated by characteristic network and neuronal temporal code patterning.

[Characteristics of electrographic and behavioral seizures induced by chronic tetanization of the right caudate-putamen in rats].

AIM: The electrographic and behavioral kindling effects were induced by chronic tetanization of the right caudate-putamen (CPu) to study the target-behavior expression involved in the CPu or hippocampus (HPC) network abnormalities. METHODS: Experiments were performed on 58 SD rats. Tetanization (60Hz,0.4 - 0.6mA, 2s) was delivered into the CPu or the HPC, once a day, for 7-12 days. Animal behaviors were observed every day and depth electrographs were recorded at the beginning or at the end of the experiments. RESULTS: Chronic tetanization of the CPu or of the HPC induced: (1) Rhythmic sharp waves in the CPu and paroxysmal epileptiform events in the HPC electrographs. (2) Primary behavioral seizures, secondary behavioral seizures, and kindling effects, including wet dog shakes (WEDS), rearing, face washing, immobility, chewing and head nodding. (3) Lower rate of primary WEDS (P < 0.01), and higher rate of secondary WEDS (P < 0.01) in the CPu-tetanized rats. (4) Longer silent period of behavioral seizures before kindling appeared in the CPu-tetanized rats. CONCLUSION: Kindling effects in the CPu-tetanized rats resembles those in the HPC-tetanized rats. The CPu might participate in the origin of epileptic focus and be involved in reestablishment of limbic epileptic networks, which may be responsible for the target-behavioral seizures.