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An exciton is the bosonic quasiparticle of electron–hole pairs bound by the Coulomb interaction1. Bose–Einstein condensation of this exciton state has long been the subject of speculation in various model systems2,3, and examples have been found more recently in optical lattices and two-dimensional materials4–9. Unlike these conventional excitons formed from extended Bloch states4–9, excitonic bound states from intrinsically many-body localized states are rare. Here we show that a spin–orbit-entangled exciton state appears below the Neel temperature of 150 kelvin in NiPS3, an antiferromagnetic van der Waals material. It arises intrinsically from the archetypal many-body states of the Zhang–Rice singlet10,11, and reaches a coherent state assisted by the antiferromagnetic order. Using configuration-interaction theory, we determine the origin of the coherent excitonic excitation to be a transition from a Zhang–Rice triplet to a Zhang–Rice singlet. We combine three spectroscopic tools—resonant inelastic X-ray scattering, photoluminescence and optical absorption—to characterize the exciton and to demonstrate an extremely narrow excitonic linewidth below 50 kelvin. The discovery of the spin–orbit-entangled exciton in antiferromagnetic NiPS3 introduces van der Waals magnets as a platform to study coherent many-body excitons. A spin–orbit-entangled exciton state in the van der Waals material NiPS3 is observed, and found to arise from many-body states of a Zhang–Rice singlet.

Single-layer porphyrin polymerization Two-dimensional polymers can be made as monolayer sheets through controlled synthesis at an interface. However, it is often difficult to create intact sheets over large areas that can be transferred onto substrates. Zhong et al. polymerized derivatized porphyrin molecules during laminar flow at a sharp pentane-water interface to form sheets that are 5 centimeters in diameter (see the Perspective by MacLean and Rosei). The authors used electron microscopy and spectroscopy to confirm that they had produced intact monolayers. These films were then transferred onto monolayer sheets of molybdenum disulfide to form superlattices for use as capacitors. Science , this issue p. 1379 ; see also p. 1308

Estrogen receptor alpha (ERα) is a sex hormone nuclear receptor that regulates various physiological events, including the immune response. Although there have been some recent studies on ERα regarding subsets of T cells, such as Th1, Th2, Th17, and Treg cells, its role in follicular helper T (TFH) cells has not yet been elucidated. To determine whether ERα controls TFH response and antibody production, we generated T cell-specific ERα knockout (KO) mice by utilizing the CD4-Cre/ERα flox system (CD4-ERα KO) and then analyzed their phenotype. At approximately 1 year of age, CD4-ERα KO mice spontaneously showed mild autoimmunity with increased autoantibody production and CD4+CD44+CXCR5+Bcl-6+ TFH cells in the mesenteric lymph nodes and spleen. We next immunized 6–8-week-old CD4-ERα KO mice with sheep red blood cells (SRBCs), which resulted in an increased proportion of TFH cells and germinal center (GC) responses. In addition, 17β-estradiol (E2) treatment decreased TFH responses in wild-type mice and suppressed the mRNA expression of Bcl-6 and IL-21. Finally, we confirmed that the production of high-affinity antigen-specific antibodies and isotype class switching induced by NP-conjugated ovalbumin immunization were elevated in CD4-ERα KO mice under sufficient estrogen conditions. These results collectively demonstrate that the female sex hormone receptor ERα inhibits the TFH cell response and GC reaction to control autoantibody production, which was related to estrogen signaling and autoimmunity., Autoimmune disease: the importance of estrogen Estrogen signaling may play a crucial role in mediating autoimmune responses and preventing diseases such as rheumatoid arthritis. Estrogen plays vital roles in the female endocrine and reproductive systems, and its function is partly mediated by the estrogen receptor alpha (ERα). ERα-deficient mice have more severe autoimmune disease, suggesting a link between estrogen signaling and immune responses. Je-Min Choi at Hanyang University in Seoul, South Korea, and co-workers generated mice with T cells lacking ERα and followed their immune system development. They were particularly interested in monitoring follicular helper T cells (TFH), which help B cells generate antibodies in response to pathogen attack as well as self-antigen. The ERα-deficiency in T cells spontaneously developed mild autoimmune symptoms in mice, with increased levels of TFH and autoantibodies. Their results suggest ERα-mediated estrogen signaling in CD4 T cells is needed to suppress TFH activity and limit autoimmune disease development in female.

Over the last few decades, oil tankers and bulk carriers, which preferably adopting the concept of a single stern tube bearing, have been subjected to the mechanical damages on propulsion shaft bearings since such a concept overly requires a single bearing to support the full load of the propulsion shaft. This paper was to fundamentally address the problem of current practices of aligning a single stern tube bearing for commercial ships by determining the effective supporting point to balance the load of the propulsion shaft properly. Since selecting a case ship subjected to the damage on the stern tube bearing, it investigated the actual cause of the damage, thereby finding a practical way to enhance the sustainability of the propulsion shaft system using the single stern tube bearing. Computer-aided simulations using the finite element analysis as well as on-site measurements were carried out. Research findings revealed that the ignorance of the relative slope angle between the propulsion shaft and the aft stern tube bearing had led to misalignment, which resulted in adverse effects on the stability of the shaft system, and consequently damaged the stern tube bearing. Results of the analysis suggested that the degree of slope be taken into account when estimating the effective supporting point of the bearing. Finally, this paper pointed out that the establishment of a shaft installation guideline considering the effect of the shaft slope, thereby preventing wiping damage of the aft stern tube bearing would be an urgent task.

This paper is to evaluate the LNG bunkering safety for a 50,000 dead weight tonnage bulk carrier renowned as the world first LNG fueled bulk carrier. To establish a proper level of the safety zone against the potential risk of gas release from the LNG bunkering systems encompassing from truck to ship, it introduces an enhanced quantitative risk assessment process with two key ideas: firstly, the integration of the population-independent analysis with the population-dependent analysis, and secondly, the combination between the probabilistic analysis and CFD simulation for gas dispersion. Research results reveal that the appropriate levels of the safe zone can be set at 28.8 m in 1E-4/year criterion that concerns the individual risk of a fatality at the given distance to the risk source of 1 in 10,000 years, whereas at 46.6 m (in 1E-5/year criterion) and at 213.3 m (in 1E-6/year criterion) when the area within 5% and higher gas concentration in air is regarded the critical zone. On the other hand, in case of the critical area considered to be within 2.5% and higher gas concentration in air, the safety zone will much expand to 34.9 m (in 1E-4/year criterion), 80.4 m (in 1E-5/year criterion) and 541.8 m (in 1E-6/year criterion). These dissimilarities suggest that LNG bunkering ports pay attention to selecting appropriate safety criteria which would considerably change the range of safety zones. The case study also demonstrates the effectiveness of the proposed approach that can remedy the shortcomings/shortfalls of existing technical and regulatory guidance on establishing the zones. It is, therefore, believed that the risk assessment approach proposed in this paper can contribute to determining the appropriate level of safety zones whereas providing practical insight into port authorities and flag states.

Renal fibrosis is an irreversible and progressive process that causes severe dysfunction in chronic kidney disease (CKD). The progression of CKD stages is highly associated with a gradual reduction in serum Klotho levels. We focused on Klotho protein as a key therapeutic factor against CKD. Urine-derived stem cells (UDSCs) have been identified as a novel stem cell source for kidney regeneration and CKD treatment because of their kidney tissue-specific origin. However, the relationship between UDSCs and Klotho in the kidneys is not yet known. In this study, we discovered that UDSCs were stem cells that expressed Klotho protein more strongly than other mesenchymal stem cells (MSCs). UDSCs also suppressed fibrosis by inhibiting transforming growth factor (TGF)-β in HK-2 human renal proximal tubule cells in an in vitro model. Klotho siRNA silencing reduced the TGF-inhibiting ability of UDSCs. Here, we suggest an alternative cell source that can overcome the limitations of MSCs through the synergetic effect of the origin specificity of UDSCs and the anti-fibrotic effect of Klotho.

일반적으로, 선박 축계는 프로펠러 중량의 영향으로 선미관 후부베어링의 국부적인 지지하중 증가가 현격하게 나타나 잠재적인 축계 베어링 손상의 위험성을 가진다. 이를 방지하기 위한 추진축계 정렬연구는 대부분 준정적 상태(quasi-static condition)에서 프로펠러축과 선미관 후부베어링간의 상대적 경사각을 감소시키는데 중점을 두어 진행되어 왔다. 그러나 보다 완전한 축계 안정성 평가를 위해서는 동적상태에 대한 고려가 필요하다. 본 연구에서는 동적 상태에서 선박 좌현 전타시 과도적으로 변동되는 프로펠러 편심추력이 선미관 내에서 유체 유도 불안정 상태와 스톨(stall)현상을 발생시키는 것을 확인하였다. 따라서 향후 추진축계 정렬 관련 연구에는 축계 안정성 확보를 위하여 과도상태시 편심추력에 의해 발생하는 불평형 진동 특성을 추가적으로 고려해야 할 필요가 있음을 확인하였다.

Layered materials such as graphite and transition metal dichalcogenides have extremely anisotropic mechanical properties owing to orders of magnitude difference between in-plane and out-of-plane interatomic interaction strengths. Although effects of mechanical perturbations on either intra- or inter-layer interactions have been extensively investigated, mutual correlations between them have rarely been addressed. Here we show that layered materials have an inevitable coupling between in-plane uniaxial strain and interlayer shear. Because of this, the uniaxial in-plane strain induces an anomalous splitting of the degenerate interlayer shear phonon modes such that the split shear mode along the tensile strain is not softened but hardened contrary to the case of intralayer phonon modes. We confirm the effect by measuring Raman shifts of shear modes of bilayer MoS2 under strain. Moreover, by analyzing the splitting, we obtain an unexplored off-diagonal elastic constant, demonstrating that Raman spectroscopy can determine almost all mechanical constants of layered materials., Comment: 36 pages, 10 figures

Gallium selenide (GaSe) is one of layered group-III metal monochalcogenides, which has an indirect bandgap in monolayer and direct bandgap in bulk unlike other conventional transition metal dichalcogenides (TMDs) such as MoX2 and WX2 (X=S and Se). Four polytypes of bulk GaSe, designated as beta-, epsilon-, gamma-, and delta-GaSe, have been reported. Since different polytypes result in different optical and electrical properties even for the same thickness, identifying the polytype is essential in utilizing this material for various optoelectronic applications. We performed polarized Raman measurement on GaSe and found different ultra-low-frequency Raman spectra of inter-layer vibrational modes even for the same thickness due to different stacking sequences of the polytypes. By comparing the ultra-low-frequency Raman spectra with theoretical calculations and high-resolution electron microscopy measurements, we established the correlation between the ultra-low-frequency Raman spectra and the stacking sequences for trilayer GaSe. We further found that the AB-type stacking is more stable than the AA'-type stacking in GaSe.

An exciton is the bosonic quasiparticle of electron-hole pairs bound by the Coulomb interaction

Since the use of LNG as an alternative fuel has drawn increasing attention from the marine industry, this paper aimed to evaluate three competitive LNG fuelled engine systems: ultra-steam turbine, four-stroke medium speed engine, and two-stroke low-speed engine systems. To achieve this goal, the paper developed an enhanced hybrid decision-making model which was applied to integrate the economic, environmental and technical performance of these systems. This model can be represented as a semi-quantitative multi-criteria decision making process in combination of several novel techniques, particularly ‘life cycle cost assessment’ for economic analysis, ‘life cycle assessments’ for environmental analysis, ‘fuzzy order preference by similarity to ideal solution’ for technical analysis and ‘fuzzy analytic hierarchy process’ for multi-criteria decision making. A case study with a 174 K LNG carrier has revealed that the two-stroke low-speed engine system is the most effective overall and suggested that this type of engine system will hold the lead over the other candidates in the large LNG carrier market. It has also demonstrated the effectiveness of the proposed model to improve the inherent subjectivity in existing qualitative multi-criteria decision-making processes by guiding the overall process in a more objective direction. Finally, this paper has revealed an underlying novelty of the proposed model to enhance the level of confidence level in the decision by expanding our short-term perspective to the holistic one.

Carbon dioxide (CO2) is an abundant and cheap carbon source that is partly responsible for global warming in the atmosphere. The objective of this study was to construct a recombinant E. coli strain that can show enhanced production of succinate derived from CO2. In this study, we confirmed the enhancement of utilization by analyzing succinate containing one carbon-13 (13C) derived from 13CO2. Firstly, the carbonic anhydrase gene (SP(-)HCCA) derived from Hahella chejuensis KCTC 2396 was over-expressed to enhance carbon flux toward bicarbonate ion (HCO3-) synthesis in E. coli. The phosphoenolpyruvate carboxylase gene (ppc) was over-expressed to enhance the production of oxaloacetate by enhancing the carbon flux. Compared with the control strain, the percentage of the succinate containing one 13C (succinate119) to total succinate was enhanced by approximately 2.80-fold and the amount of succinate119 also increased by approximately 4.09-fold in SGJS120. Secondly, the lactate dehydrogenase gene (ldhA) was deleted to re-direct the utilization of the carbon source from glucose to enhance succinate production in SGJS120. However, ldhA deletion did not increase CO2 utilization in SJGS120. Finally, the phosphotransferase system gene (ptsG) and pyruvate kinase F gene (pykF) were deleted to increase the amount of phosphoenolpyruvate (PEP). SGJS126 (pykF deletion strain) showed the highest increase, which was 6.05-fold higher than the control strain. From the results, SP(-)HCCA overexpression and pykF deletion may be useful for enhancing CO2 utilization in E. coli. Additionally, engineered strains showed the potential to reduce the cost of succinate production by using an industrially cheaper carbon source such as CO2 and converting CO2 to a valuable chemical.

Raman spectra of few-layer MoSe2 were measured with 8 excitation energies. New peaks that appear only near resonance with various exciton states are analyzed, and the modes are assigned. The resonance profiles of the Raman peaks reflect the joint density of states for optical transitions, but the symmetry of the exciton wave functions leads to selective enhancement of the A1g mode at the A exciton energy and the shear mode at the C exciton energy. We also find Davydov splitting of intra-layer A1g, E1g, and A2u modes due to inter-layer interaction for some excitation energies near resonances. Furthermore, by fitting the spectral positions of inter-layer shear and breathing modes and Davydov splitting of intra-layer modes to a linear chain model, we extract the strength of the inter-layer interaction. We find that the second-nearest-neighbor inter-layer interaction amounts to about 30% of the nearest-neighbor interaction for both in-plane and out-of-plane vibrations., 45 pages, 19 figures, ACS Nano published (2016)

At the initial stage of propulsion shaft design, in line with shaft alignment, an intensified consideration of lateral vibration is needed to verify its operational safety. Recently the alignment problem affecting the lateral vibration has been becoming issues. However, the theoretical method of forced lateral vibration analysis is not cleary established so far and it is about to simply limited among the classification societies and international standards to avoid the blade natural frequency resonance cpm outside of of engine rpm at MCR. On the other hand, longer center distance between each support bearing shows an affirmative result normally in shaft alignment analysis whereas the blade order resonance speed may cause lowering near the limitation in the aspect of lateral vibration. Therefore, it is required careful attention to engineers as described above. As a method to solve the problem, it is mainly considered that remove forward stern tube bearing. In this paper, based on a medium size container ship case, theoretical study was carried out in the context of the forward stern tube bearing. The various effects and functions of forward stern tube bearing are reviewed and evaluated. Then an guidance note to lead the conclusion is proposed.

The marine industry has been striving to seek for proper strategies to curb air emissions from global shipping activities. To support the transition to sustainable shipping, this paper was proposed to evaluate the holistic environmental benefits of the LNG partial re-liquefaction system applied to LNG carriers by comparing among five different combination/configuration of LNG re-liquefaction systems. The theory of life cycle assessment was employed with the help of a commercial software, Sphera GaBi version 2019 to quantify the magnitude of various emissions under different life stages of the proposed systems: manufacturing, installation, use and recycling. A case study was implemented with a 174,200 m3 LNG carrier and the input data for the analysis was collected from true-to-life sources provided by manufacturers and ship operators. The electric consumption of the five systems were calculated by means of Aspen HYSYS software. A range from 1.23 to 1.64 kWh/kg was estimated and was used as key parameters to confirm the onboard electricity demands at the use phase of the five systems. The results revealed that the partial re-liquefaction system had considerable effects on the reduction in emission levels across the following five impact categories: Global Warming Potential, Particulate Matter, Photochemical Ozone Creation Potential, Eutrophication Potential and Acidification Potential. An optimal option which adopted the partial re-liquefaction system was found to release 4.49 × 108 kg CO2 eq. 1.25 × 106 kg PM2.5 eq. 7.16 × 106 kg NMVOC eq. 2.46 × 106 kg N eq. and 1.13 × 107 kg SO2 eq. in its lifetime, which were roughly equivalent to 25% emission reductions compared to the rest of the candidates to which the partial re-liquefaction principle was not applied. Lastly, it clearly presents the effectiveness of life cycle assessment. This research, particularly, suggests that this holistic approach should not be underused for resolving innumerable maritime environmental issues that appear unsolvable with the current practices in the maritime industry.

In response to the impending international maritime regulation, MARPOL Annex VI Reg. 14, to curb sulphur oxides (SOx) arising from shipping activities, this paper aimed to evaluate the environmental impacts of the entire life cycle of three different SOx reduction scrubber systems: (1) ‘wet open-loop’, (2) ‘wet closed-loop’, and (3) ‘wet hybrid’. To achieve this goal, the paper developed ‘the Parametric Trend Life Cycle Assessment (PT-LCA)’ which was introduced to proceed the extensive analysis for a number of case ship studies and quantify various emissions, such as greenhouse gases (GHG), sulphur oxides (SOx), nitrogen oxides (NOx), associated with the proposed systems from cradle to grave. A case study designed with the database consisting of 1,565 ocean-going Ro-Ro vessels based on Lloyd’s Register has revealed that, in terms of Global Warming Potential (GWP) and Acidification Potential (AP), closed-loop scrubbers were proven more environmentally friendly than open-loop scrubbers, but the opposite was true for Eutrophication Potential (EP). By identifying specific trends in scrubber systems in relation to various input parameters, the assessment contributed to improving environmental sustainability, as well as the total estimated amount of numerical environmental impacts that the scrubber systems have for the international fleets. The proposed framework enabled us not only to evaluate the different emission levels of systems applied to various ships but also to obtain the general trends of emission levels over ship parameters, which were expressed as formulae. The novelty of this paper can be placed on the provision of an insight into the optimal selection of scrubber systems depending on ship characteristics. It could also offer an insight into the improvement of current environmental regulations and guidelines by means of PT-LCA.

This paper was to address the shortcomings of current design practice to evaluate the stability of the shaft alignment for a 300,000 DWT Very Large Crude Oil Carrier. An enhanced approach using FE was applied to identify the influence of hull deformation on the alignment of the shafting system. The effectiveness of this method was demonstrated in comparison with Jack up technique. Analysis results showed that the hull deformation could be a key factor affecting the offset distortion of each bearing supporting the shaft line. Moreover, it was confirmed that the deformation pattern of cargo hold was opposite to the deformation of engine room structure when hull deformation occurred due to draught change of the case ship. As new research findings, they are believed to contribute significantly to the prevention of shaft damage associated with hull deformations, thereby improving the reliability of shaft alignment for similar types of vessels.

Three types of carbon nanoscroll (CNS) structures that are formed when scrolling up graphene sheets are investigated using Raman spectroscopy and atomic force microscopy (AFM). The CNSs were produced from exfoliated monolayer graphene deposited on a Si chip by applying a droplet of isopropyl alcohol (IPA) solution. The three types of CNS are classified as single-elliptical-core, double-elliptical-core (both with large internal volumes) and collapsed ribbon-like, based on AFM surface profile measurements. We discuss the structure and formation of CNS with much larger hollow cores than is commonly assumed and relate this to the large effective 2D bending stiffness of graphene in the IPA solution. The large elliptical core structures show Raman spectra similar to those previously reported for CNS and indicate little interaction between the scrolled layers. The Raman spectra from ribbon-like structures show additional features that are similar to that of folded graphene. These new features can be related to layer breathing modes combined with some resonance enhancement at specific regions of the ribbon-like CNSs that are due to specific twist angles produced when the structure folds/collapses.

How a certain ground state of complex physical systems emerges, especially in two-dimensional materials, is a fundamental question in condensed-matter physics. A particularly interesting case is systems belonging to the class of XY Hamiltonian where the magnetic order parameter of conventional nature is unstable in two-dimensional materials leading to a Berezinskii−Kosterlitz−Thouless transition. Here, we report how the XXZ-type antiferromagnetic order of a magnetic van der Waals material, NiPS3, behaves upon reducing the thickness and ultimately becomes unstable in the monolayer limit. Our experimental data are consistent with the findings based on renormalization-group theory that at low temperatures a two-dimensional XXZ system behaves like a two-dimensional XY one, which cannot have a long-range order at finite temperatures. This work provides the experimental examination of the XY magnetism in the atomically thin limit and opens opportunities of exploiting these fundamental theorems of magnetism using magnetic van der Waals materials., Exploring the ground state of two-dimensional (2D) magnetic systems enriches the fundamental understanding of magnetism and boosts the applications. The authors here show the suppression of magnetic order and 2D XY behavior in XXZ-type antiferromagnet NiPS3 when approaching the monolayer limit by Raman spectroscopy.

As a variety of digital devices have recently become widely commercialized, digital forensics, a process where electronic information stored in digital devices is accurately identified, collected, preserved and analysed and the information is submitted to the court as evidence, is gaining enormous popularity. This paper analyses characteristics, applications, limitations of digital forensic tools and compare the tool with others in terms of ease of use, thereby helping investigators to adopt integrated digital forensic tools in their investigation.

Few-layer tungsten diselenide (WSe2) is investigated using circularly polarized Raman spectroscopy with up to eight excitation energies. The main E2g1 and A1g modes near 250 cm-1 appear as a single peak in the Raman spectrum taken without consideration of polarization but are resolved by using circularly polarized Raman scattering. The resonance behaviors of the E2g1 and A1g modes are examined. Firstly, both the E2g1 and A1g modes are enhanced near resonances with the exciton states. The A1g mode exhibits Davydov splitting for trilayers or thicker near some of the exciton resonances. The low-frequency Raman spectra show shear and breathing modes involving rigid vibrations of the layers and also exhibit strong dependence on the excitation energy. An unidentified peak at ~19 cm-1 that does not depend on the number of layers appears near resonance with the B exciton state at 1.96 eV (632.8 nm). The strengths of the intra- and inter-layer interactions are estimated by comparing the mode frequencies and Davydov splitting with the linear chain model, and the contribution of the next-nearest-neighbor interaction to the inter-layer interaction turns out to be about 34% of the nearest-neighbor interaction. Fano resonance is observed for 1.58-eV excitation, and its origin is found to be the interplay between two-phonon scattering and indirect band transition., 45 pages, 20 figures (including Supplementary Information)

Correction for ‘Anomalous polarization dependence of Raman scattering and crystallographic orientation of black phosphorus’ by Jungcheol Kim et al., Nanoscale, 2015, 7, 18708–18715, DOI: 10.1039/C5NR04349B.

Background Coronary vasospasm causes variant angina, as well as acute myocardial infarction, ventricular tachycardia, and sudden cardiac death. We evaluated morphological changes due to vasospastic lesions, which may cause acute coronary syndrome (ACS), using a novel technique called optical coherence tomography (OCT). Methods Twenty patients (40–83 years old, 19 males) with vasospasm-induced ACS who visited the emergency room because of continuous chest pain and displayed transient ST segment elevation in their electrocardiogram were enrolled in the study. None of these patients had significant coronary artery disease and all had positive results in the provocation test. OCT examinations were performed for evaluation of vasospastic lesions. Results Intraluminal thrombi and intimal erosion were found in 6 (33.3%) and 2 patients (10%), respectively. High-sensitivity C-reactive protein levels were significantly higher in patients with microthrombi (2.66 ± 3.33 mg/L) compared with those in patients without microthrombi (0.49 ± 0.30 mg/L; P = 0.022). Serum cardiac troponin-I levels were not significantly different between patients with or without microthrombi (2.37 ± 5.31 ng/mL vs. 1.45 ± 4.68 ng/mL; P = 0.704). Other parameters, including creatinine kinase–myocardial band isoenzyme, total cholesterol, pain duration, residual stenosis, lesion length, and coronary risk factors, were not significantly different between the 2 groups. Conclusion In patients with vasospasm-induced ACS, microthrombi with or without intimal erosion are major abnormal morphologic findings of OCT examinations. However, further large-scale studies are required for validation. (J Interven Cardiol 2013;26:491-500)

Raman spectra of few-layer WS2 have been measured with up to seven excitation energies, and peculiar resonance effects are observed. The two-phonon acoustic phonon scattering signal close to the main E2g1 peak is stronger than the main peaks for excitations near the A or B exciton states. The low-frequency Raman spectra show a series of shear and layer-breathing modes that are useful for determining the number of layers. In addition, hitherto unidentified peaks (X1 and X2), which do not seem to depend on the layer thickness, are observed near resonances with exciton states. The polarization dependences of the two peaks are different: X1 vanishes in cross polarization, but X2 does not. At the resonance with the A exciton state, the Raman-forbidden, lowest-frequency shear mode for odd number of layers appears as strong as that for the allowed case of even number of layers. This mode also exhibits a strong Breit-Wigner-Fano line shape and an anomalous polarization behavior at this resonance., Comment: 35 pages, 16 figures