Repetitive transcranial magnetic stimulation for Alzheimer's disease: an overview of systematic reviews and meta-analysis.

Objective: Alzheimer's disease (AD) is a prevalent neurodegenerative condition that significantly impacts both individuals and society. This study aims to evaluate the effectiveness of repetitive transcranial magnetic stimulation (rTMS) as a treatment for AD by summarizing the evidence from systematic reviews (SRs) and meta-analyses (MAs). Methods: SRs/MAs of rTMS for AD were collected by searching Embase, Web of Science, Cochrane Library, PubMed, CNKI, VIP, Sino-Med, and Wanfang databases. The search was conducted from database creation to January 23, 2024. Methodological quality, reporting quality and risk of bias were assessed using the Assessing Methodological Quality of Systematic Reviews 2 (AMSTAR-2), Risk of Bias in Systematic Reviews (ROBIS) tool and the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA). In addition, the quality of evidence for outcome measures was assessed using the Grading of Recommendations, Assessment, Development and Evaluation (GRADE). Results: Eight SRs/MAs included in this study met the inclusion criteria. Based on the AMSTAR-2, 4 of the SRs/MA were classified as low quality, while the remaining 4 were deemed to be of very low quality. The PRISMA analysis revealed that out of the 27 items reporting, 16 achieved full reporting (100%). However, there were still some deficiencies in reporting, particularly related to protocol and registration, search strategy, risk of bias, and additional analysis. The ROBIS tool indicated that only 3 SRs/MAs had a low risk of bias. The GRADE assessment indicated that 6 outcomes were of moderate quality (18.75%), 16 were of low quality (50%), and 10 were classified as very low quality (31.25%). Conclusion: Based on the evidence collected, rTMS appears to be effective in improving cognitive function in AD patients, although the methodological quality of the SRs/MAs reduces the reliability of the conclusions and the overall quality is low. However, based on the available results, we still support the value of rTMS as an intervention to improve cognitive function in AD. In future studies, it is necessary to confirm the efficacy of rTMS in AD patients and provide more reliable and scientific data to contribute to evidence-based medicine.

Terahertz photoconductive antenna based on antireflection dielectric metasurface with embedded plasmonic nanodisks: erratum.

This erratum reports corrections in Figs. 5 and 8 of our previous paper [Appl. Opt.60, 7921 (2021)APOPAI0003-693510.1364/AO.431678].

Curcumin Synergizes with Cisplatin to Inhibit Colon Cancer through Targeting the MicroRNA-137-Glutaminase Axis.

OBJECTIVE: Colorectal cancer (CRC) is one of the most lethal and prevalent malignancies world-wide. Currently, surgery, radiotherapy and chemotherapy are clinically applied as common approaches for CRC patients. Cisplatin is one of the most frequently used chemotherapy drugs for diverse cancers. Although chemotherapeutic strategies have improved the prognosis and survival of cancer patients, development of cisplatin resistance has led to cancer recurrence. Curcumin, isolated from turmeric, has been used as an effective anti-cancer agent. However, the molecular mechanisms for curcumin-mediated cisplatin sensitivity of CRC have not been elucidated. This study aimed to investigate the effects of curcumin treatment on cisplatin-resistant CRC cells. METHODS: Expression levels of miRNAs and mRNAs were determined by qRT-PCR. Protein expression levels were detected by Western blotting. Cell responses to curcumin treatments were evaluated by MTT assay, Clonogenic assay and Annexin V apoptosis assay. The glutamine metabolism of colon cancer cells was assessed by glutamine uptake and glutaminase (GLS) activity. The binding of miR-137 on 3' UTR of GLS was validated by Western blotting and luciferase assay. RESULTS: Results demonstrated that curcumin significantly synergized with cisplatin (combination index <1) to suppress proliferation of colon cancer cells compared with curcumin or cisplatin alone. Moreover, from the established cisplatin-resistant cell line (HT-29), glutamine metabolism was remarkedly elevated in cisplatin-resistant CRC cells that displayed a glutamine addictive phenotype. Furthermore, curcumin treatments attenuated glutamine metabolism in colon cancer cells. Under low glutamine supply, colon cancer cells showed less sensitivity to curcumin. Using a microRNA (miRNA) microArray assay, miR-137, a tumor suppressor in colon cancer, was significantly induced by curcumin treatments in CRC cells. Bioinformatics analysis and a luciferase assay illustrated miR-137 directly targeted the 3' UTR of GLS mRNA. Rescue experiments demonstrated that miR-137-induced cisplatin sensitization was through targeting of GLS. Finally, curcumin treatment overcame cisplatin resistance through miR-137-mediated glutamine inhibition. CONCLUSION: Collectively, these results indicate that curcumin could be clinically applied as an anti-chemoresistance approach against CRC by modulating miR-137-inhibited glutamine metabolism.

Terahertz photoconductive antenna based on antireflection dielectric metasurfaces with embedded plasmonic nanodisks.

By taking advantage of dielectric metasurfaces and plasmonic nanostructures, a terahertz photoconductive antenna (THz-PCA) is proposed and investigated in detail. The designed dielectric metasurfaces can reduce the optical reflection down to 1.4% and accelerate the switching process (electric conductive to resistive) that broadens the THz spectrum emitted from THz-PCA. Simultaneously, the embedded plasmonic nanostructures can realize 11.2 times enhancement in local electric field without affecting the switching process and the damage threshold of the THz-PCA. Simulated results indicate that the proposed THz-PCA is 70.56 times stronger in THz radiation power than that of the traditional THz-PCA. The significant enhancement ensures the proposed THz-PCA has great prospects in promoting THz technology based on the THz-PCA.

Impact of COVID-19 on Acute Stroke Presentation in a Designated COVID-19 Hospital.

Objectives: Thousands of designated COVID-19 hospitals have been set up in China to fight the ongoing COVID-19 pandemic. Anecdotal reports indicate a falling rate of acute stroke diagnoses in these hospitals during the COVID-19 period. We conducted an exploratory single-center analysis to estimate the change in acute stroke presentation at the designated COVID-19 hospitals. Methods: This retrospective observational study included all patients admitted to Yongchuan Hospital Affiliated to Chongqing Medical University with acute stroke between January 24 and March 10, 2020. Patient demographics, characteristics of the stroke, treatment details, and clinical outcomes were compared with those of patients admitted in the corresponding period in the year before (2019, "the pre-COVID-19 period"). Subgroup analysis was performed in the ischemic and hemorrhagic stroke groups. Results: A total of 110 patients presented with acute stroke symptoms during the COVID-19 pandemic, compared with 173 patients in the pre-COVID-19 period. A higher proportion of stroke patients presented to the hospital via emergency medical services during the pandemic (48.2 vs. 31.8%, p = 0.006). There was a lower proportion of ischemic stroke patients (50.9 vs. 65.3%, p = 0.016) than in the preceding year. There were significantly fewer patients with 90-day modified Rankin Scale score ≥3 in the COVID-19 period compared with the pre-COVID-19 period (17.3 vs. 30.6%, p = 0.012). Among patients with ischemic stroke, the mean time from patient arrival to vessel puncture for emergency endovascular therapy in the COVID-19 period was shorter than that in the pre-COVID-19 period (109.18 ± 71.39 vs. 270.50 ± 161.51 min, p = 0.002). Among patients with hemorrhagic stroke, the rate of emergency surgical operation in the COVID-19 period was higher than that in the pre-COVID-19 period (48.1 vs. 30.0%, p = 0.047). The mean time from patient arrival to emergency surgical operation (15.31 ± 22.89 vs. 51.72 ± 40.47 min, p = 0.002) was shorter in the COVID-19 period than in the pre-COVID-19 period. Conclusions: Although fewer acute stroke patients sought medical care in this designated COVID-19 hospital during the COVID-19 pandemic, this type of hospital was more efficient for timely treatment of acute stroke. Recognizing how acute strokes presented in designated COVID-19 hospitals will contribute to appropriate adjustments in strategy for dealing with acute stroke during COVID-19 and future pandemics.

Risk factors for adverse clinical outcomes with COVID-19 in China: a multicenter, retrospective, observational study.

Background: The risk factors for adverse events of Coronavirus Disease-19 (COVID-19) have not been well described. We aimed to explore the predictive value of clinical, laboratory and CT imaging characteristics on admission for short-term outcomes of COVID-19 patients. Methods: This multicenter, retrospective, observation study enrolled 703 laboratory-confirmed COVID-19 patients admitted to 16 tertiary hospitals from 8 provinces in China between January 10, 2020 and March 13, 2020. Demographic, clinical, laboratory data, CT imaging findings on admission and clinical outcomes were collected and compared. The primary endpoint was in-hospital death, the secondary endpoints were composite clinical adverse outcomes including in-hospital death, admission to intensive care unit (ICU) and requiring invasive mechanical ventilation support (IMV). Multivariable Cox regression, Kaplan-Meier plots and log-rank test were used to explore risk factors related to in-hospital death and in-hospital adverse outcomes. Results: Of 703 patients, 55 (8%) developed adverse outcomes (including 33 deceased), 648 (92%) discharged without any adverse outcome. Multivariable regression analysis showed risk factors associated with in-hospital death included ≥ 2 comorbidities (hazard ratio [HR], 6.734; 95% CI; 3.239-14.003, p < 0.001), leukocytosis (HR, 9.639; 95% CI, 4.572-20.321, p < 0.001), lymphopenia (HR, 4.579; 95% CI, 1.334-15.715, p = 0.016) and CT severity score > 14 (HR, 2.915; 95% CI, 1.376-6.177, p = 0.005) on admission, while older age (HR, 2.231; 95% CI, 1.124-4.427, p = 0.022), ≥ 2 comorbidities (HR, 4.778; 95% CI; 2.451-9.315, p < 0.001), leukocytosis (HR, 6.349; 95% CI; 3.330-12.108, p < 0.001), lymphopenia (HR, 3.014; 95% CI; 1.356-6.697, p = 0.007) and CT severity score > 14 (HR, 1.946; 95% CI; 1.095-3.459, p = 0.023) were associated with increased odds of composite adverse outcomes. Conclusion: The risk factors of older age, multiple comorbidities, leukocytosis, lymphopenia and higher CT severity score could help clinicians identify patients with potential adverse events.

Timely identification of atypical acute aortic dissection in the emergency department:a study from a tertiary hospital

Background/aim: Acute aortic dissection (AAD) is a rare but fatal disease if left untreated. Symptoms are often similar to common conditions; therefore, the diagnostic strategy is important. We aimed to identify the atypical symptoms in a timely manner without putting patients at greater risk for undetected AAD. Materials and methods: We conducted a retrospective observational study of 59 AAD patients with both atypical and typical symptoms from January 2012 to December 2016. Patients with atypical symptoms continuing more than 30 min underwent a D-dimer test and computed tomography (CT) or computed tomographic angiography (CTA). Results: Of the 59 AAD patients, 22 were atypical. In the atypical group, the median delay time in our hospital was 3.1 h; average delay time after July 2015 was shorter than average delay time before June 2015 (16.59 ± 24.70 vs. 1.90 ± 0.57 h, P = 0.076). Conclusions: For patients in the emergency department who are suspected of having AAD, incorporating atypical symptoms with high levels of D-dimer into a triage strategy could improve the efficiency of clinical decision making. Furthermore, essential education directed towards the recognition of the atypical symptoms of AAD for front-line physicians may aid in a timely diagnosis, as compared with the usual assessments in the emergency department.

Effects of UV-B radiation on the survival, egg hatchability and transcript expression of antioxidant enzymes in a high-temperature adapted strain of Neoseiulus barkeri.

Biological control of spider mites in hot and dry weather is a serious technical issue. A high-temperature adapted strain (HTAS) of the predatory mite Neoseiulus barkeri Hughes was selected from its conventional strain (CS), via long-term heat acclimation and frequent heat hardenings in our previous studies. However, the environment of high temperature is usually associated with enhanced ultraviolet (UV) radiation. In the present study, the physiological effects of UV-B radiation on survival rate and egg damage of N. barkeri were investigated, as well as the activities and expression profiles of antioxidant enzymes to UV-B radiation stress. UV-B radiation had deleterious effects on egg hatchability and survival of N. barkeri. Adults of the HTAS strain were less UV-B resistant than those of the CS strain; they also had lower levels of enzymatic activity of superoxide dismutase (SOD) and catalase against oxidative damage and weaker upregulation of SOD genes. The mRNA expression of three SOD genes of CS adult females immediately increased whereas that of HTAS showed almost no difference under UV-B stress for 1 h. The results showed the HTAS of N. barkeri had lower fitness under UV-B stress compared with the CS of N. barkeri. These results suggested that long-term heat acclimation may exert a profound impact on the developmental physiology of N. barkeri.

Terahertz and infrared characteristic absorption spectra of aqueous glucose and fructose solutions.

In this paper, the terahertz (THz) and infrared (IR) characteristic absorption spectra of aqueous glucose solutions and aqueous fructose solutions with different concentrations were measured and studied. The absorption spectra of these two molecules in solid-state and in aqueous solutions were compared and analyzed, the significant effect of molecular adjacent environment on the molecular structure and vibrational mode was revealed. In addition, the THz and IR absorption spectra of these two isomers' aqueous solutions were also compared and explored. No obvious differences were found from their IR absorption features measured at room temperature, while their THz absorption spectra do have the differences, indicating THz characteristic absorption spectra more suitable for the detection and identification of aqueous glucose and fructose solutions. The results are helpful to understand the influence of aqueous solutions environment on the molecular structures and vibrational modes of the materials, and also provide a theoretical reference for the quantum chemical calculation of biological macromolecules.

Fingolimod Protects Against Ischemic White Matter Damage by Modulating Microglia Toward M2 Polarization via STAT3 Pathway.

BACKGROUND AND PURPOSE: White matter (WM) ischemic injury, a major neuropathological feature of cerebral small vessel diseases, is an important cause of vascular cognitive impairment in later life. The pathogenesis of demyelination after WM ischemic damage are often accompanied by microglial activation. Fingolimod (FTY720) was approved for the treatment of multiple sclerosis for its immunosuppression property. In this study, we evaluated the neuroprotective potential of FTY720 in a WM ischemia model. METHODS: Chronic WM ischemic injury model was induced by bilateral carotid artery stenosis. Cognitive function, WM integrity, microglial activation, and potential pathway involved in microglial polarization were assessed after bilateral carotid artery stenosis. RESULTS: Disruption of WM integrity was characterized by demyelination in the corpus callosum and disorganization of Ranvier nodes using Luxol fast blue staining, immunofluorescence staining, and electron microscopy. In addition, radial maze test demonstrated that working memory performance was decreased at 1-month post-bilateral carotid artery stenosis-induced injury. Interestingly, FTY720 could reduce cognitive decline and ameliorate the disruption of WM integrity. Mechanistically, cerebral hypoperfusion induced microglial activation, production of associated proinflammatory cytokines, and priming of microglial polarization toward the M1 phenotype, whereas FTY720 attenuated microglia-mediated neuroinflammation after WM ischemia and promoted oligodendrocytogenesis by shifting microglia toward M2 polarization. FTY720's effect on microglial M2 polarization was largely suppressed by selective signal transducer and activator of transcription 3 (STAT3) blockade in vitro, revealing that FTY720-enabled shift of microglia from M1 to M2 polarization state was possibly mediated by STAT3 signaling. CONCLUSIONS: Our study suggested that FTY720 might be a potential therapeutic drug targeting brain inflammation by skewing microglia toward M2 polarization after chronic cerebral hypoperfusion.

Fingolimod suppresses neuronal autophagy through the mTOR/p70S6K pathway and alleviates ischemic brain damage in mice.

The bioactive, signaling lipid, sphingosine-1-phosphate (S1P), and its analog, fingolimod (FTY720), have previously shown neuroprotective effects against ischemic brain injury. However, the underlying mechanisms have not yet been fully clarified. The roles of autophagy in ischemic stroke are being increasingly recognized. In the present study, we sought to determine whether the S1P pathway is involved in neuronal autophagy and investigate its possible mechanisms following stroke. Interestingly, we found that FTY720 significantly attenuates infarct volumes and reduces neuronal apoptosis on days 1 and 3 post stroke, accompanied by amelioration of functional deficits. Additionally, FTY720 was found to decrease the induction of autophagosome proteins, microtubule-associated protein 1 light chain 3(LC3-II) and Beclin1, following ischemic stroke in a dose-dependent manner. Meanwhile, protein levels of the mammalian target of rapamycin (mTOR) and the 70-kDa ribosomal protein, S6 kinase1 (p70S6K), were also up-regulated in FTY720-treated animals, and the nonspecific SphK inhibitor, N,N-dimethylsphingosine (DMS), was found to cause a reverse effect. Our results indicate that modulation of the S1P signaling pathway by FTY720 could effectively decrease neuronal autophagy through the mTOR/p70S6K pathway and attenuate ischemic brain injury in mice.

Plasma levels of soluble receptor for advanced glycation end products in Alzheimer's disease.

BACKGROUND: A decreased plasma level of soluble form of the receptor for advanced glycation end products (sRAGE) in patients with Alzheimer's disease (AD) has been reported. However, no evidence has shown whether the sRAGE plasma level of AD patients may differentiate from other types of dementia. METHODS: Our study assessed sRAGE concentrations in the following 121 individuals in Chongqing area: 36 patients with AD, 12 with vascular dementia (VaD), 14 with mixed dementia (MD), 24 with other dementia (OD) including Parkinson's disease dementia, frontotemporal dementia, paralytic dementia and 35 cognitively normal controls. The total plasma level of sRAGE was determined using sandwich ELISA method. RESULTS: sRAGE concentration in AD is significantly decreased compared with healthy controls. However, the receiver operating characteristic curve analysis of sRAGE between the AD and the control shows a low diagnostic accuracy. CONCLUSIONS: Our results demonstrate that sRAGE may assist the diagnosis of AD from normal individuals, but cannot differentiate AD from VaD, MD or OD.

Preoperative assessment of labial bone perforation for virtual immediate implant surgery in the maxillary esthetic zone: A computer simulation study.

BACKGROUND: In this computer simulation study, the authors investigated the frequency distribution of labial bone perforation (LBP) between various sagittal root position (SRP) classes with respect to the anterior maxillary osseous housing and evaluated the associated factors correlated with a higher risk of LBP when performing a virtual immediate implant surgery in the esthetic zone. METHODS: The authors analyzed cone-beam computed tomography (CBCT) images from 285 qualified study participants (1,449 teeth) to determine the probability of LBP when associated with selected variables, such as tooth type, SRP class, and morphologic parameters. The authors examined associated factors and analyzed the adjusted odds ratios by means of multiple logistic regression analysis. RESULTS: The overall probability of LBP was 81.7%, which presented statistically significant differences between each specific tooth type and SRP class (all P<.001). After adjusting for other factors, the authors found that the maxillary central incisor was 2.37 times more likely to have LBP than the canine. SRP class I was 4.9 times more likely to be associated with LBP when compared with SRP class IV. CONCLUSIONS: When a clinician performs an immediate implant in the anterior esthetic zone, he or she should be aware that the specific tooth type, SRP class, and morphologic features of fossa concavities are associated with a risk of experiencing LBP. PRACTICAL IMPLICATIONS: Presurgical cross-sectional images can be analyzed to identify anatomic features relative to LBP in the maxillary esthetic region, and this can avoid unpleasant complications, specifically when performing immediate implant procedures.

Risk of lingual plate perforation for virtual immediate implant placement in the posterior mandible: A computer simulation study.

BACKGROUND: This study sought to determine which factors are correlated to a higher risk of lingual plate perforation (LPP) when placing a virtual implant in the area of the anticipated extraction site of the posterior mandible. METHODS: Computed tomographic images of 300 patients (1,279 teeth) were analyzed in regard to the shape of the mandible (convergent, parallel, or undercut type), dimensional parameters of lingual concavity (angle, height, depth) and its relation to the inferior alveolar canal (zones A, B, C), distance from root apex to inferior alveolar canal, and probability of LPP. The odds ratio of variables was determined by multiple logistic regression modeling. RESULTS: The overall probability of LPPs on virtual implant placement was 3.1%. This perforation was most commonly observed at the second molar and with a U-type ridge. After adjusting cofounders, a concave point located in zone A is 17.34 times more likely to have a LPP than one in zone C. The probability of LPPs was reduced by 34% for every 1-millimeter increase in distance from root apex to inferior alveolar canal on virtual implant placement of posterior mandible region. CONCLUSIONS: Three-dimensional cone-beam computed tomographic imaging is essential for planning immediate implant placement in the anticipated extraction sites of the posterior mandible region as proved by anatomic findings that can only be understood from preoperative imaging analysis. PRACTICAL IMPLICATIONS: Presurgical cross-sectional images can be analyzed to identify anatomic features relative to the lingual concavities in the posterior mandible region, which can help to avoid unpleasant complications, specifically when performing immediate implant procedures.

Rapid Identification of Legionella Pathogenicity by Surface-Enhanced Raman Spectroscopy.

OBJECTIVE: To establish Surface-enhanced Raman Spectroscopy (SERS) can be used as a rapid and reliable method to distinguish virulent strain and mild strain of L. pneumophila. METHODS: Mortality data were collected from company departments through administrative documents, death certificates, etc. Trend analyses of cancer mortality were performed on the basis of 925 cancer deaths between 2001 and 2010. RESULTS: Our results indicated that the peaks of high virulence strains reached ⋝4000. This criterion was verified by subsequent cell experiments. In addition, we also conducted SERS rapid identification on the virulence of several collected clinical strains and obtained accurate results. CONCLUSION: The present study indicates that the established SERS protocol can be used as a rapid and reliable method to distinguish virulent and mildly virulent strains of L. pneumophila, which can be further used in clinical samples.

Ionic liquids: not only structurally but also dynamically heterogeneous.

In recent years, the complex and heterogeneous structure of ionic liquids has been demonstrated; however, the consequences on the dynamics have remained elusive. Here, we use femtosecond IR spectroscopy to elucidate the local structural dynamics in protic alkylammonium-based ionic liquids. The structural relaxation after an ultrafast temperature increase, following vibrational excitation and subsequent relaxation of the N-D (or N-H) stretching vibration, is found to vary substantially between the ionic and hydrophobic subdomains. The dynamics in the ionic domains are virtually unaffected by the alkyl chain length and is, therefore, decoupled from viscosity. Equilibration within the hydrophobic subdomains, as evident from the dynamics of the C-H stretching vibration, is faster than that in the ionic domains and shows a remarkably low thermal activation.

High-resolution reconstruction for terahertz imaging.

We present a high-resolution (HR) reconstruction model and algorithms for terahertz imaging, taking advantage of super-resolution methodology and algorithms. The algorithms used include projection onto a convex sets approach, iterative backprojection approach, Lucy-Richardson iteration, and 2D wavelet decomposition reconstruction. Using the first two HR reconstruction methods, we successfully obtain HR terahertz images with improved definition and lower noise from four low-resolution (LR) 22×24 terahertz images taken from our homemade THz-TDS system at the same experimental conditions with 1.0 mm pixel. Using the last two HR reconstruction methods, we transform one relatively LR terahertz image to a HR terahertz image with decreased noise. This indicates potential application of HR reconstruction methods in terahertz imaging with pulsed and continuous wave terahertz sources.

[Study on THz spectra and vibrational modes of benzoic acid and sodium Benzoate].

Terahertz time-domain spectroscopy was employed to measure the terahertz absorption spectra of benzoic acid and sodium benzoate at room temperature. The origins of the measured features of benzoic acid were summarized based on previous study. Density functional theory was used to compute and analyze the molecular structure and vibrational modes of sodium benzoate in monomer. Based on the obtained results, the authors found that the THz spectral features can be used to distinguish benzoic acid and sodium benzoate totally; the essential reason for the THz spectral difference between benzoic acid and sodium benzoate is that the electrovalent bond of sodium benzoate affects the values of covalent bond lengths and bond angles, as well as the molecular interactions and arrangement in unit cell; the measured features of benzoic acid and sodium benzoate come from the collective vibrations except the peaks located at 107 cm-1 of benzoic acid and 54 cm-1 of sodium benzoate.

[Terahertz spectroscopy of DNA nucleobases: cytosine and thymine].

The absorption features of DNA nucleobases cytosine and thymine were measured by terahertz time-domain spectroscopy (THz-TDS) from 0.1 to 3.5 THz. Our experimental results clearly show that these important biomolecules exhibit distinctive absorption features in THz region. To the best of our knowledge, the subtle absorption peak of cytosine at 2.53 THz is reported for the first time. Moreover, geometry optimizations and lattice dynamic calculations on cytosine crystal were also performed with the pseudo-potential plane wave method of density functional theory by taking periodic boundary conditions into account. All measured terahertz absorption features of cytosine were assigned successfully and its absorption spectrum was reproduced according to our calculations. Furthermore, our results show that absorption features of cytosine below 3.5 THz arise from external modes in translation and rotation motions, which are dominated by the intermolecular hydrogen bonds.

First principles investigation of L-alanine in terahertz region.

Terahertz absorption spectrum (0.5-4.0 THz) of L-alanine in the solid phase was measured by terahertz time-domain spectroscopy at room temperature. Simulations utilizing gaseous-state and solid-state theory were performed to determine the origins of the observed vibrational features. Our calculations showed that the measured features in solid-state materials could be well understood by considering the crystal packing interactions in a solid-state density functional theory calculation. Furthermore, intermolecular vibrations of L-alanine are found to be the dominating contributions to these measured spectral features in the range of 0.5-4.0 THz, except that located at 3.11 THz.