Your browser doesn't support javascript.
loading
Show: 20 | 50 | 100
Results 1 - 20 de 233
Filter
1.
Dis Model Mech ; 2024 Jun 21.
Article in English | MEDLINE | ID: mdl-38903011

ABSTRACT

Pathogenic variants in GFPT1, encoding a key enzyme to synthesize UDP-N-acetylglucosamine (UDP-GlcNAc), cause congenital myasthenic syndrome (CMS). We made a knock-in (KI) mouse model carrying a frameshift variant in Gfpt1 exon 9 simulating a CMS patient. As Gfpt1 exon 9 is exclusively included in striated muscles, Gfpt1-KI mice were deficient for Gfpt1 only in skeletal muscles. In Gfpt1-KI mice, (i) UDP-HexNAc, CMP-NeuAc, and protein O-GlcNAcylations were reduced in skeletal muscles; (ii) aged Gfpt1-KI mice showed poor exercise performance and abnormal neuromuscular junction structures; and (iii) markers for unfolded protein response (UPR) were elevated in skeletal muscles. Denervation-mediated enhancement of ER stress in Gfpt1-KI mice facilitated protein folding, ubiquitin-proteasome degradation, and apoptosis, whereas autophagy was not induced and protein aggregates were markedly increased. Lack of autophagy was accounted for by enhanced degradation of FoxO1 by increased Xbp1-s/u proteins. Similarly, in Gfpt1-silenced C2C12 myotubes, ER stress exacerbated protein aggregates and activated apoptosis, but autophagy was attenuated. In both skeletal muscles in Gfpt1-KI mice and Gfpt1-silenced C2C12 myotubes, maladaptive UPR failed to eliminate protein aggregates and provoked apoptosis.

2.
Ind Health ; 2024 May 14.
Article in English | MEDLINE | ID: mdl-38749756

ABSTRACT

This study was to investigate the employment status of pregnant women in Japan and identify risk factors associated with resigning from work during pregnancy. We conducted a cross-sectional survey with 975 postpartum women in Tokyo and its suburbs, focusing on those who were employed during pregnancy. Women who were employed when they became pregnant were selected and divided into two groups: those who did not resign and those who resigned; the groups were analyzed separately. Multiple logistic regression analyses were performed to examine associations between employment resignation and risk factors. The analysis revealed that 79% continued working, while 8.1% resigned. Risk factors for resignation included non-regular employment (OR: 13.1, 95% CI: 6.6-25.9), fewer employees (OR: 3.4, 95% CI: 1.8-6.4), and shorter employee tenure (OR: 2.4, 95% CI: 1.1-5.2). Non-regular employment status, a smaller number of employees, and shorter employee tenure were identified as risk factors for working women resigning from their job during pregnancy. In work situations and work environments that encourage pregnant women to leave the workforce, developing systems to improve these conditions for pregnant employees may help women to progress in the labor force.

3.
Healthcare (Basel) ; 12(5)2024 Feb 21.
Article in English | MEDLINE | ID: mdl-38470630

ABSTRACT

Tokophobia is regarded as the intensive fear of childbirth that some pregnant women have. However, little is known about the psychopathological details of tokophobia (fear of childbirth). Between 2020 and 2021, a total of 10 pregnant women (nine nulliparae and one multipara) with a strong fear of childbirth were referred by obstetricians. Semi-structured psychopathological interviews were conducted, and two cases were judged to have obsession, three an overvalued idea, and one secondary delusion. Three were characterised by both obsession and overvalued idea and one by both obsession and secondary delusion. In total, six cases had features of an overvalued idea. All of the participants except one had a lifetime history of a specific phobia. In addition, their history included social phobia in two cases, panic disorder in one case, obsessive-compulsive disorder (other than tokophobia) in two cases, depressive disorder in two cases, bipolar disorder in two cases, and PTSD in six cases. To conclude, this study showed that tokophobia was not a phobic disorder but a kind of overvalued idea that requires specific assessment and treatment.

4.
Neurotherapeutics ; 21(2): e00318, 2024 Mar.
Article in English | MEDLINE | ID: mdl-38233267

ABSTRACT

Signal transduction at the neuromuscular junction (NMJ) is compromised in a diverse array of diseases including congenital myasthenic syndromes (CMS). Germline mutations in CHRNE encoding the acetylcholine receptor (AChR) ε subunit are the most common cause of CMS. An active form of vitamin D, calcitriol, binds to vitamin D receptor (VDR) and regulates gene expressions. We found that calcitriol enhanced MuSK phosphorylation, AChR clustering, and myotube twitching in co-cultured C2C12 myotubes and NSC34 motor neurons. RNA-seq analysis of co-cultured cells showed that calcitriol increased the expressions of Rspo2, Rapsn, and Dusp6. ChIP-seq of VDR revealed that VDR binds to a region approximately 15 â€‹kbp upstream to Rspo2. Biallelic deletion of the VDR-binding site of Rspo2 by CRISPR/Cas9 in C2C12 myoblasts/myotubes nullified the calcitriol-mediated induction of Rspo2 expression and MuSK phosphorylation. We generated Chrne knockout (Chrne KO) mouse by CRISPR/Cas9. Intraperitoneal administration of calcitriol markedly increased the number of AChR clusters, as well as the area, the intensity, and the number of synaptophysin-positive synaptic vesicles, in Chrne KO mice. In addition, calcitriol ameliorated motor deficits and prolonged survival of Chrne KO mice. In the skeletal muscle, calcitriol increased the gene expressions of Rspo2, Rapsn, and Dusp6. We propose that calcitriol is a potential therapeutic agent for CMS and other diseases with defective neuromuscular signal transmission.


Subject(s)
Myasthenic Syndromes, Congenital , Animals , Mice , Myasthenic Syndromes, Congenital/drug therapy , Myasthenic Syndromes, Congenital/genetics , Myasthenic Syndromes, Congenital/metabolism , Calcitriol/metabolism , Neuromuscular Junction/metabolism , Receptors, Cholinergic/genetics , Receptors, Cholinergic/metabolism , Motor Neurons/metabolism
5.
J Obstet Gynaecol Res ; 50(3): 403-423, 2024 Mar.
Article in English | MEDLINE | ID: mdl-38163757

ABSTRACT

AIM: This study aimed to determine the weight gain during pregnancy that minimizes the predicted probability of various perinatal adverse events according to the pre-pregnancy body mass index (BMI) and make recommendations for optimal weight gain in Japan. METHODS: The Japan Society of Obstetrics and Gynecology perinatal database for 2015-2017 was used. From the 719 723 deliveries included in this database, parturients with underlying diseases or missing data were excluded, and 419 114 deliveries were analyzed. A questionnaire survey was also conducted to weigh each perinatal adverse event. For each of the nine outcomes, a restricted cubic spline model was made to estimate the association between the "expected gestational weight gain at 40 weeks" and the outcome risk. RESULTS: Since the classes of medical facilities were generally the same, weights were assigned according to the mean of the questionnaires rather than by the class of the facility. For each pre-pregnancy BMI, the weight gains during pregnancy that minimized the predicted probability of various adverse perinatal events were 12-15, 10-13, 7-10, and upper limit of 5 kg for the underweight, normal-weight, obese 1, and obese ≥2 groups, respectively. CONCLUSIONS: The weight gain during pregnancy that minimizes the predicted probability of various perinatal adverse events according to the pre-pregnancy BMI was established.


Subject(s)
Obesity , Weight Gain , Female , Pregnancy , Humans , Japan/epidemiology , Retrospective Studies , Obesity/epidemiology , Registries
6.
Opt Express ; 31(24): 40142-40150, 2023 Nov 20.
Article in English | MEDLINE | ID: mdl-38041321

ABSTRACT

In this study, ultrafast transient signals were detected on a single-shot basis using chirped-pulse up-conversion spectroscopy with dispersion compensation. Unlike in the conventional time-encoding technique using chirped pulses, distortion of the ultrafast waveform was reduced by applying dispersion compensation to the chirped probe pulses and using sum-frequency generation with the chirped readout pulses. The method was applied to terahertz time-domain spectroscopy and near-infrared pump-probe spectroscopy, providing ultrafast observations with an improved temporal resolution comparable to the transform-limited pulse durations. Terahertz waveforms, Kerr rotation signals, and phonon-polariton oscillations were measured accurately with no significant waveform distortion, thereby showing the proposed scheme to be promising for single-shot pump-probe spectroscopy in a wide range of spectroscopic applications.

7.
Sci Adv ; 9(50): eadj4074, 2023 Dec 15.
Article in English | MEDLINE | ID: mdl-38100589

ABSTRACT

The recently demonstrated chiral modes of lattice motion carry angular momentum and therefore directly couple to magnetic fields. Notably, their magnetic moments are predicted to be strongly influenced by electronic contributions. Here, we have studied the magnetic response of transverse optical phonons in a set of Pb1-xSnxTe films, which is a topological crystalline insulator for x > 0.32 and has a ferroelectric transition at an x-dependent critical temperature. Polarization-dependent terahertz magnetospectroscopy measurements revealed Zeeman splittings and diamagnetic shifts, demonstrating a large phonon magnetic moment. Films in the topological phase exhibited phonon magnetic moment values that were larger than those in the topologically trivial samples by two orders of magnitude. Furthermore, the sign of the effective phonon g-factor was opposite in the two phases, a signature of the topological transition according to our model. These results strongly indicate the existence of interplay between the magnetic properties of chiral phonons and the topology of the electronic band structure.

8.
J Med Econ ; 26(1): 1386-1397, 2023.
Article in English | MEDLINE | ID: mdl-37849298

ABSTRACT

AIMS: To investigate the prevalence, treatment status, and effect of anemia on medical costs, quality of life (QOL), and productivity loss in Japan. METHODS: This cross-sectional study used a database containing claims, health check-ups, and questionnaire data. Adults with hemoglobin data at 2020 check-ups were included. QOL and productivity loss were evaluated using EuroQol 5-Dimension (EQ-5D) and Work Productivity and Activity Impairment questionnaire data available for a subset of the population. Nationwide anemia prevalence, including both diagnosed as having anemia and undiagnosed but with low hemoglobin levels, were estimated. Treatment status was described by hemoglobin levels. Differences in medical costs, QOL, and productivity loss were compared between individuals with and without anemia. Subgroup analyses were performed using the Charlson Comorbidity Index (CCI). RESULTS: The study population included 554,798 individuals. Anemia prevalence was estimated at 15.1% with 55.3% undiagnosed. In patients with anemia, 85.3% were untreated; 79.5% of the treated patients received only oral iron drugs. In patients with anemia, monthly medical costs were ¥17,766 higher, EQ-5D score was 0.0118 lower, and productivity loss was 2.6% higher than in those without anemia. The trends were consistent even in limited patients with CCI = 0. Nationwide annual excess medical costs, deficit QOL, and productivity loss in patients with anemia were estimated at ¥3.32 trillion, 138,000 quality-adjusted life-years, and ¥1.13 trillion, respectively. LIMITATIONS: As the study population only included individuals who underwent health check-ups, they may be healthier than general population. Whether the differences in medical costs, QoL, and productivity loss are caused by anemia or other underlying differences in patient characteristics is unclear, given the likelihood of residual confounding. CONCLUSIONS: The results suggest that more than half of patients with anemia were undiagnosed and untreated. Patients with anemia had higher medical costs, lower QOL, and greater productivity loss than those without anemia.


Subject(s)
Anemia , Quality of Life , Humans , Adult , Prevalence , Cross-Sectional Studies , East Asian People , Anemia/epidemiology , Hemoglobins
9.
Ecotoxicol Environ Saf ; 264: 115482, 2023 Oct 01.
Article in English | MEDLINE | ID: mdl-37717354

ABSTRACT

The pervasive weak electromagnetic fields (EMF) inundate the industrialized society, but the biological effects of EMF as weak as 10 µT have been scarcely analyzed. Heat shock proteins (HSPs) are molecular chaperones that mediate a sequential stress response. HSP70 and HSP90 provide cells under undesirable situations with either assisting covalent folding of proteins or degrading improperly folded proteins in an ATP-dependent manner. Here we examined the effect of extremely low-frequency (ELF)-EMF on AML12 and HEK293 cells. Although the protein expression levels of HSP70 and HSP90 were reduced after an exposure to ELF-EMF for 3 h, acetylations of HSP70 and HSP90 were increased, which was followed by an enhanced binding affinities of HSP70 and HSP90 for HSP70/HSP90-organizing protein (HOP/STIP1). After 3 h exposure to ELF-EMF, the amount of mitochondria was reduced but the ATP level and the maximal mitochondrial oxygen consumption were increased, which was followed by the reduced protein aggregates and the increased cell viability. Thus, ELF-EMF exposure for 3 h activated acetylation of HSPs to enhance protein folding, which was returned to the basal level at 12 h. The proteostatic effects of ELF-EMF will be able to be applied to treat pathological states in humans.


Subject(s)
Electromagnetic Fields , Heat-Shock Proteins , Humans , Acetylation , Electromagnetic Fields/adverse effects , HEK293 Cells , Protein Folding , HSP70 Heat-Shock Proteins , HSP90 Heat-Shock Proteins , Adenosine Triphosphate
10.
Genes (Basel) ; 14(9)2023 09 06.
Article in English | MEDLINE | ID: mdl-37761905

ABSTRACT

Single nucleotide variants (SNVs) affecting the first nucleotide G of an exon (Fex-SNVs) identified in various diseases are mostly recognized as missense or nonsense variants. Their effect on pre-mRNA splicing has been seldom analyzed, and no curated database is available. We previously reported that Fex-SNVs affect splicing when the length of the polypyrimidine tract is short or degenerate. However, we cannot readily predict the splicing effects of Fex-SNVs. We here scrutinized the available literature and identified 106 splicing-affecting Fex-SNVs based on experimental evidence. We similarly identified 106 neutral Fex-SNVs in the dbSNP database with a global minor allele frequency (MAF) of more than 0.01 and less than 0.50. We extracted 115 features representing the strength of splicing cis-elements and developed machine-learning models with support vector machine, random forest, and gradient boosting to discriminate splicing-affecting and neutral Fex-SNVs. Gradient boosting-based LightGBM outperformed the other two models, and the length and nucleotide compositions of the polypyrimidine tract played critical roles in the discrimination. Recursive feature elimination showed that the LightGBM model using 15 features achieved the best performance with an accuracy of 0.80 ± 0.12 (mean and SD), a Matthews Correlation Coefficient (MCC) of 0.57 ± 0.15, an area under the curve of the receiver operating characteristics curve (AUROC) of 0.86 ± 0.08, and an area under the curve of the precision-recall curve (AUPRC) of 0.87 ± 0.09 using a 10-fold cross-validation. We developed a web service program, named FexSplice that accepts a genomic coordinate either on GRCh37/hg19 or GRCh38/hg38 and returns a predicted probability of aberrant splicing of A, C, and T variants.


Subject(s)
Nucleotides , RNA Splicing , Exons/genetics , Databases, Factual , Gene Frequency , Nucleotides/genetics
11.
iScience ; 26(10): 107746, 2023 Oct 20.
Article in English | MEDLINE | ID: mdl-37744035

ABSTRACT

Glutamine:fructose-6-phosphate transaminase 1 (GFPT1) is the rate-limiting enzyme of the hexosamine biosynthetic pathway (HBP). A 54-bp exon 9 of GFPT1 is specifically included in skeletal and cardiac muscles to generate a long isoform of GFPT1 (GFPT1-L). We showed that SRSF1 and Rbfox1/2 cooperatively enhance, and hnRNP H/F suppresses, the inclusion of human GFPT1 exon 9 by modulating recruitment of U1 snRNP. Knockout (KO) of GFPT1-L in skeletal muscle markedly increased the amounts of GFPT1 and UDP-HexNAc, which subsequently suppressed the glycolytic pathway. Aged KO mice showed impaired insulin-mediated glucose uptake, as well as muscle weakness and fatigue likely due to abnormal formation and maintenance of the neuromuscular junction. Taken together, GFPT1-L is likely to be acquired in evolution in mammalian striated muscles to attenuate the HBP for efficient glycolytic energy production, insulin-mediated glucose uptake, and the formation and maintenance of the neuromuscular junction.

12.
Neurosci Res ; 194: 58-65, 2023 Sep.
Article in English | MEDLINE | ID: mdl-37146794

ABSTRACT

Lower motor neuron degeneration is the pathological hallmark of spinal muscular atrophy (SMA), a hereditary motor neuron disease caused by loss of the SMN1 gene and the resulting deficiency of ubiquitously expressed SMN protein. The molecular mechanisms underlying motor neuron degeneration, however, remain elusive. To clarify the cell-autonomous defect in developmental processes, we here performed transcriptome analyses of isolated embryonic motor neurons of SMA model mice to explore mechanisms of dysregulation of cell-type-specific gene expression. Of 12 identified genes that were differentially expressed between the SMA and control motor neurons, we focused on Aldh1a2, an essential gene for lower motor neuron development. In primary spinal motor neuron cultures, knockdown of Aldh1a2 led to the formation of axonal spheroids and neurodegeneration, reminiscent of the histopathological changes observed in human and animal cellular models. Conversely, Aldh1a2 rescued these pathological features in spinal motor neurons derived from SMA mouse embryos. Our findings suggest that developmental defects due to Aldh1a2 dysregulation enhances lower motor neuron vulnerability in SMA.


Subject(s)
Muscular Atrophy, Spinal , Mice , Humans , Animals , Muscular Atrophy, Spinal/genetics , Muscular Atrophy, Spinal/metabolism , Muscular Atrophy, Spinal/pathology , Motor Neurons/metabolism , Nerve Degeneration/metabolism , Disease Models, Animal , Aldehyde Dehydrogenase 1 Family/metabolism , Retinal Dehydrogenase/metabolism
13.
Cureus ; 15(2): e35290, 2023 Feb.
Article in English | MEDLINE | ID: mdl-36974237

ABSTRACT

We treated a 65-year-old man for COVID-19 who was hospitalized urgently due to life-threatening respiratory decompensation and later developed cardiac arrest, both of which were successfully treated. Three days prior to the patient's urgent hospitalization, he had a high fever of over 38.0°C. Viral infection was diagnosed by polymerase chain reaction (PCR) on the day of admission, which was negative on the 11th day. Blood analysis on the second day was strongly positive for COVID-19 IgG antibodies, which continued for one year. Because of the acute increase in viral IgG antibodies, we performed other immunological analyses; Sjögren's syndrome antigen A (SS-A) and Sjögren's syndrome antigen B (SS-B) antibodies were positive, although he had no history of autoimmune diseases. Subsequent salivary-gland biopsy and pathological analysis confirmed the diagnosis of Sjögren's syndrome. The severe clinical manifestations and early antibody seroconversion in this case suggest COVID-19 as a mediator of autoimmunity and Sjögren's syndrome.

14.
BMC Pregnancy Childbirth ; 23(1): 182, 2023 Mar 16.
Article in English | MEDLINE | ID: mdl-36927405

ABSTRACT

BACKGROUND: Abnormal cardiotocogram (CTG) tracing may appear after induction of neuraxial labor analgesia. Non-reassuring fetal status (NRFS) indicated by severely abnormal tracings, such as prolonged deceleration (PD) or bradycardia, can necessitate immediate operative delivery. Combined spinal epidural analgesia (CSEA) is known to result in more frequent abnormal tracings than epidural analgesia (EA); however, the corresponding data related to dural puncture epidural (DPE) are unclear. We aimed to evaluate the rates of incidence of severe abnormal CTG after induction of DPE and CSEA. METHODS: In this study of nulliparous women with full-term pregnancy, data for the DPE intervention group were prospectively collected, while those for the CSEA control group were obtained from medical records. Neuraxial analgesia was performed with cervical dilation ≤ 5 cm, administering initial epidural dosing of 15 mL of 0.125% levobupivacaine with fentanyl 2.5µg/mL for DPE, and intrathecal 0.5% bupivacaine 2.5 mg (0.5ml), fentanyl 10 µg (0.2ml), and 1.3 mL of saline for CSEA. The primary outcome was the incidence of PD, defined as a fetal heart rate reduction ≥ 15 bpm below the baseline and with a lowest value < 80 bpm, and lasting for ≥ 2 min but < 10 min (fetal heart rate < 80 bpm does not have to last for ≥ 2 min), within 90 min after induction of neuraxial labor analgesia. RESULTS: A total of 302 patients were analyzed, with 151 in each group. The incidence of PD after DPE induction was significantly lower than that after CSEA induction (4.0% vs. 14.6%, P = 0.0015, odds ratio = 0.243, 95% confidence interval = 0.095-0.617). CONCLUSION: DPE appears to be a safer method compared to CSEA for neuraxial labor analgesia in the early stages of labor for nulliparous women. TRIAL REGISTRATION: UMIN-CTR: UMIN000035153 . Date registered: 01/01/2019.


Subject(s)
Analgesia, Epidural , Analgesia, Obstetrical , Pregnancy , Humans , Female , Pilot Projects , Heart Rate, Fetal , Incidence , Deceleration , Analgesia, Obstetrical/adverse effects , Analgesia, Obstetrical/methods , Spinal Puncture/methods , Analgesics , Fentanyl , Analgesia, Epidural/adverse effects , Analgesia, Epidural/methods , Labor, Induced
15.
Healthcare (Basel) ; 11(5)2023 Feb 26.
Article in English | MEDLINE | ID: mdl-36900701

ABSTRACT

Intense fear of childbirth by expectant women is called tokophobia. Because there are no qualitative studies targeting women with an intense fear of childbirth in Japan, it is unknown whether there is any link between the type of fear of objects/situations among tokophobic women and their psychological/demographic background. Furthermore, there is no available summary of the lived experience of Japanese women with tokophobia. This study aims to identify the intensity patterns of various types of fear among the participants and summarize the lived experience of having intense fear of childbirth. A qualitative descriptive study was conducted using a semi-structured interview. Pregnant women with an intense fear of childbirth participated in individual interviews facilitated by a psychiatrist and a midwife. Audio recordings of the interviews were transcribed and analyzed using a content analysis approach. The number of participants was ten. The types of feared objects varied individually and these were categorized as being related to either prospective or retrospective fear. The participants' experiences were grouped into three categories: difficulty in daily life, preoccupied negative expectation towards childbirth, and psychological adaptation to the upcoming childbirth. The results imply that women with tokophobia continuously suffer from fear in their daily life; hence, a special approach is needed to detect and reduce their fear.

16.
Surg J (N Y) ; 9(1): e36-e38, 2023 Jan.
Article in English | MEDLINE | ID: mdl-36742157

ABSTRACT

Intrauterine balloon prolapse sometimes occurs, and the intrauterine balloon must be reinserted. Furthermore, intrauterine balloon tamponade (IBT) failure can necessitate additional invasive procedures. We report a case of cervical cerclage with IBT for placenta previa with a cervical dilation. In our case, emergency cesarean section was performed at 35 + 4 weeks of gestation because of persistent hemorrhage. During the operation, we performed IBT to prevent further postpartum hemorrhage. However, immediately after the operation, uterine cervical dilatation was 6 cm, which resulted in cervical dilation and prolapse of the intrauterine balloon. Therefore, we performed cervical cerclage using absorbable sutures with IBT and blood transfusion. We speculated that the intrauterine balloon might have induced cervical canal ripening during the operation. Our case suggested that cervical cerclage with IBT is a useful method to prevent intrauterine balloon prolapse in cases with cervical dilation.

17.
J Obstet Gynaecol Res ; 49(1): 54-67, 2023 Jan.
Article in English | MEDLINE | ID: mdl-36257320

ABSTRACT

The perinatal resuscitation history in Japan is short, with the earliest efforts in the field of neonatology. In contrast, the standardization and dissemination of maternal resuscitation is lagging. With the establishment of the Maternal Death Reporting Project and the Maternal Death Case Review and Evaluation Committee in 2010, with the aim of reducing maternal deaths, the true situation of maternal deaths came to light. Subsequently, in 2015, the Japan Council for the Dissemination of Maternal Emergency Life Support Systems (J-CIMELS) was established to educate and disseminate simulations in maternal emergency care; training sessions on maternal resuscitation are now conducted in all prefectures. Since the launch of the project and council, the maternal mortality rate in Japan (especially due to obstetric critical hemorrhage) has gradually decreased. This has been probably achieved due to the tireless efforts of medical personnel involved in perinatal care, as well as the various activities conducted so far. However, there are no standardized guidelines for maternal resuscitation yet. Therefore, a committee was set up within the Japan Resuscitation Council to develop a maternal resuscitation protocol, and the Guidelines for Maternal Resuscitation 2020 was created in 2021. These guidelines are expected to make the use of high-quality resuscitation methods more widespread than ever before. This presentation will provide an overview of the Guidelines for Maternal Resuscitation 2020.


Subject(s)
Cardiopulmonary Resuscitation , Maternal Death , Maternal Health Services , Child , Female , Humans , Infant, Newborn , Pregnancy , Cardiopulmonary Resuscitation/methods , Japan , Perinatal Care/methods
18.
Opt Express ; 30(13): 23622-23630, 2022 Jun 20.
Article in English | MEDLINE | ID: mdl-36225038

ABSTRACT

Determining the dynamics of electrons and ions emitted from a target material during laser ablation is crucial for desirable control of laser processing. However, these dynamics are still challenging to understand because of a lack of ubiquitous spectroscopic tools to observe tangled-up dynamics appearing at ultrafast timescales. Here by harnessing highly sensitive single-shot terahertz time-domain spectroscopy using an echelon mirror, we investigate pulse-to-pulse temporal profile of terahertz radiation generated from the material surface. We clearly found that the carrier-envelope phase and the electric field amplitude of the terahertz waveform systematically vary between the pre- and post-ablation depending on the laser fluence and irradiated pulse numbers. Our results provide a stepping-stone towards perception of Coulomb explosion occurring throughout the laser ablation process, which is indispensable for future laser processing applications.

19.
Nat Commun ; 13(1): 4279, 2022 Jul 25.
Article in English | MEDLINE | ID: mdl-35879336

ABSTRACT

In transition metal dichalcogenides, valley depolarization through intervalley carrier scattering by zone-edge phonons is often unavoidable. Although valley depolarization processes related to various acoustic phonons have been suggested, their optical verification is still vague due to nearly degenerate phonon frequencies on acoustic phonon branches at zone-edge momentums. Here we report an unambiguous phonon momentum determination of the longitudinal acoustic (LA) phonons at the K point, which are responsible for the ultrafast valley depolarization in monolayer MoSe2. Using sub-10-fs-resolution pump-probe spectroscopy, we observed coherent phonons signals at both even and odd-orders of zone-edge LA mode involved in intervalley carrier scattering process. Our phonon-symmetry analysis and first-principles calculations reveal that only the LA phonon at the K point, as opposed to the M point, can produce experimental odd-order LA phonon signals from its nonlinear optical modulation. This work will provide momentum-resolved descriptions of phonon-carrier intervalley scattering processes in valleytronic materials.

20.
JMA J ; 5(2): 268-269, 2022 Apr 15.
Article in English | MEDLINE | ID: mdl-35611235
SELECTION OF CITATIONS
SEARCH DETAIL
...