Urinary stone analysis on 12,846 patients: a report from a single center in China

We reported a retrospective review of the urinary stone compositions in 12,846 patients. Data on urinary stone compositions analyzed between January 2003 and December 2012 in our center were collected. Infrared spectroscopy was used for stone analysis. Predominant stone component was recorded. Patients were divided into four age groups: 0–18, 19–40, 41–60, and 61–92, and five categories by components. In order to determine the change of stone characteristics with respect to time, data were also divided into two periods, 2003–2007 and 2008–2012. A total of 12,846 stones were included in this study. The age of the patients ranged from 1 to 92 years with 7,736 males and 5,110 females. Stone made of single component was rare, 2.61 %. Calcium oxalate stone was the most common component at 82.56 %. Calcium oxalate and uric acid stones were more common in male than in female. The incidence of calcium phosphate stones and uric acid stones had increased during the past 5 years, while calcium oxalate stones decreased. We found the highest incidence of stone disease in the 41–60 years old group and the lowest in the 1–18 years old for both genders. Calcium oxalate was the dominant component in every group but was more prevalent in 19–40 years group. The percentage of magnesium ammonium phosphate stone and uric acid stone increased with age.     

A prospective study concerning the relationship between metal allergy and post-operative pain following total hip and knee arthroplasty

Purpose

A prospective study was conducted to detect whether a relationship exists between metal allergy and post-operative pain in total hip and knee arthroplasty patients. We postulated that to some extent a relationship does exist between them.

Materials and methods

Patients who had undergone total hip and knee arthroplasty surgery because of hip and knee disease were included. The exclusion criteria were patients who were treated with immunosuppressor two weeks pre-operatively, skin conditions around the patch testing site, and other uncontrollable factors. Each patient agreed to patch testing for three days before surgery. Photographic images before patch testing, two and three days after patch testing were obtained to evaluate the final incidence of metal allergy. The patch tests contained 12 metal elements; chromium, cobalt, nickel, molybdenum, titanium, aluminium, vanadium, iron, manganese, tin, zirconium, and copper. Two independent observers evaluated the images. The results were divided into a non-metal allergy group and a metal allergy group. Pre-operative and postoperative VAS score, lymphocyte transforming test, and X-rays were collected to detect the relationship between metal allergy and post-operative pain following total hip and knee arthroplasty.

Results

There were 96 patients who underwent pre-operative patch testing. The overall metal allergy rate was 51.1 % (49/96) in our study. Nickel, cobalt, manganese, and tin were the most common allergic metal elements in our study. Nine inappropriate cases were excluded, and 87 patients were finally included in our study. There were 36 metal allergy and 26 non-metal allergy patients in the THA group, while 11 metal allergy and 14 non-metal allergy patients were found in the TKA group. We found no relationship existed between metal allergy and post-surgery pain in total hip and knee arthroplasty.

Conclusion

Pain caused by metal allergy usually presents as persistent and recurrent pain. The white cell count, C-reactive protein, erythrocyte sedimentation rate and postoperative radiographs were not affected. Currently, patch testing and lymphocyte transforming tests are used for metal allergy diagnosis. We deemed that a relationship between post-surgery pain and metal allergy in total hip and knee patients may exist to some extent. Larger samples and longer follow-up time are essential for further study.     

关于血细胞计数仪白细胞分类的评价

美国Coulter 有集团公司生产的JT3型血球计数仪能计数全血细胞同时也能得出白细胞分类的结果.我们用此仪器测试258份门诊病人静脉血标本,同人工显微镜检查结果进行了比较.证明此仪器淋巴细胞和粒细胞的分析结果准确可靠,相关系数分别为0.951和0.930,单核细胞相关系数为0.468.对于嗜酸和嗜碱细胞增高,此仪器可作出定性提示,准确性较高.可疑有异常细胞的标本,此仪器能在报告上示出报警信号,阳性率为22%,其中真阳性占32%.假阴性结果占阴性标本的0.5%.JT3计数仪操作简便,分析标本速度快,白细胞分类结果可以作为常规血液检查的筛选手段.     

Health-related quality of life after mandibular resection for oral cancer: Reconstruction with free fibula flap

Objectives: Mandibular resection for oral cancer is often necessary to achieve an adequate margin of tumor clearance. Mandibular resection has been associated with a poor health-related quality of life (HRQOL), particularly before free fibula flap to reconstruct the defect. The aim of this study was to evaluate health-related quality of life in patients who have had mandibular resections of oral cancer and reconstruction with free fibula flap. Study Designs: There were 115 consecutive patients between 2008 and 2011 who were treated by primary surgery for oral squamous cell carcinoma, 34 patients had a mandibular resection. HRQOL was assessed by means of the 14-item Oral Health Impact Profile (OHIP-14) and University of Washington Quality of Life (UW-QOL) questionnaires after 12 months postoperatively. Results: In the UW-QOL the best-scoring domain was mood, whereas the lowest scores were for chewing and saliva. In the OHIP-14 the lowest-scoring domain was social disability, followed by handicap, and psychological disability. Conclusions: Mandible reconstruction with free fibula flap would have significantly influenced on patients’quality of life and oral functions. The socio-cultural data show a fairly low level of education for the majority of patients. Key words:Health-related quality of life, free fibula flap, mandibulectomy, UW-QOL, OHIP-14.     

Anomalously robust valley polarization and valley coherence in bilayer WS2

We report the observation of anomalously robust valley polarization and valley coherence in bilayer WS₂. The polarization of the photoluminescence from bilayer WS₂ follows that of the excitation source with both circular and linear polarization, and remains even at room temperature. The near-unity circular polarization of the luminescence reveals the coupling of spin, layer, and valley degree of freedom in bilayer system, and the linearly polarized photoluminescence manifests quantum coherence between the two inequivalent band extrema in momentum space, namely, the valley quantum coherence in atomically thin bilayer WS₂. This observation provides insight into quantum manipulation in atomically thin semiconductors.Tungsten sulfide WS₂, part of the family of group VI transition metal dichalcogenides (TMDCs), is a layered compound with buckled hexagonal lattice. As WS₂ thins to atomically thin layers, WS₂ films undergo a transition from indirect gap in bulk form to direct gap at monolayer level with the band edge located at energy-degenerate valleys (K, K′) at the corners of the Brillouin zone (1–3). Like the case of its sister compound, monolayer MoS₂, the valley degree of freedom of monolayer WS₂ could be presumably addressed through nonzero but contrasting Berry curvatures and orbital magnetic moments that arise from the lack of spatial inversion symmetry at monolayers (3, 4). The valley polarization could be realized by the control of the polarization of optical field through valley-selective interband optical selection rules at K and K′ valleys as illustrated in Fig. 1A (4–6). In monolayer WS₂, both the top of the valence bands and the bottom of the conduction bands are constructed primarily by the d orbits of tungsten atoms, which are remarkably shaped by spin–orbit coupling (SOC). The giant spin–orbit coupling splits the valence bands around the K (K′) valley by 0.4 eV, and the conduction band is nearly spin degenerated (7). As a result of time-reversal symmetry, the spin splitting has opposite signs at the K and K′ valleys. Namely, the Kramer’s doublet |K ↑ ? and |K′ ↓ ? is separated from the other doublet |K′ ↑ ? and |K ↓ ? by the SOC splitting of 0.4 eV. The spin and valley are strongly coupled at K (K′) valleys, and this coupling significantly suppresses spin and valley relaxations as both spin and valley indices have to be changed simultaneously.Open in a separate windowFig. 1.(A) Schematic of valley-dependent optical selection rules and the Zeeman-like spin splitting in the valence bands of monolayer WS₂. (B) Diagram of spin–layer–valley coupling in 2H stacked bilayer WS₂. Interlayer hopping is suppressed in bilayer WS₂ owing to the coupling of spin, valley, and layer degrees of freedom.In addition to the spin and valley degrees of freedom, in bilayer WS₂ there exists an extra index: layer polarization that indicates the carriers’ location, either up-layer or down-layer. Bilayer WS₂ follows the Bernal packing order and the spatial inversion symmetry is recovered: each layer is 180° in plane rotation of the other with the tungsten atoms of a given layer sitting exactly on top of the S atoms of the other layer. The layer rotation symmetry switches K and K′ valleys, but leaves the spin unchanged, which results in a sign change for the spin–valley coupling from layer to layer (Fig. 1B). From the simple spatial symmetry point of view, one might expect that the valley-dependent physics fades at bilayers owing to inversion symmetry, as the precedent of bilayer MoS₂ (8). Nevertheless, the inversion symmetry becomes subtle if the coupling of spin, valley, and layer indices is taken into account. Note that the spin–valley coupling strength in WS₂ is around 0.4 eV (the counterpart in MoS₂ ∼ 0.16 eV), which is significantly higher than the interlayer hopping energy (∼0.1 eV); the interlayer coupling at K and K′ valleys in WS₂ is greatly suppressed as indicated in Fig. 1B (7, 9). Consequently, bilayer WS₂ can be regarded as decoupled layers and it may inherit the valley physics demonstrated in monolayer TMDCs. In addition, the interplay of spin, valley, and layer degrees of freedom opens an unprecedented channel toward manipulations of quantum states.Here we report a systemic study of the polarization-resolved photoluminescence (PL) experiments on bilayer WS₂. The polarization of PL inherits that of excitations up to room temperature, no matter whether it is circularly or linearly polarized. The experiments demonstrate the valley polarization and valley coherence in bilayer WS₂ as a result of the coupling of spin, valley, and layer degrees of freedom. Surprisingly, the valley polarization and valley coherence in bilayer WS₂ are anomalously robust compared with monolayer WS₂.For comparison, we first perform polarization-resolved photoluminescence measurements on monolayer WS₂. Fig. 2A shows the photoluminescence spectrum from monolayer WS₂ at 10 K. The PL is dominated by the emission from band-edge excitons, so-called “A” exciton at K and K′ valleys. The excitons carry a clear circular dichroism under near-resonant excitation (2.088 eV) with circular polarization as a result of valley-selective optical selection rules, where the left-handed (right handed) polarization corresponds to the interband optical transition at K (K′) valley. The PL follows the helicity of the circularly polarized excitation optical field. To characterize the polarization of the luminescence spectra, we define a degree of circular polarization as P=I(σ+)−I(σ−)I(σ+)+I(σ−), where I(σ±) is the intensity of the right- (left-) handed circular-polarization component. The luminescence spectra display a contrasting polarization for excitation with opposite helicities: P = 0.4 under σ+ excitation and P = −0.4 under σ− excitation on the most representative monolayer. For simplicity, only the PL under σ+ excitation is shown. The degree of circular polarization P is insensitive to PL energy throughout the whole luminescence as shown in Fig. 2A, Inset. These behaviors are fully expected in the mechanism of valley-selective optical selection rules (3, 4). The degree of circular polarization decays with increasing temperature and drops to 10% at room temperature (Fig. 2B). It decreases as the excitation energy shifts from the near-resonance energy of 2.088 to 2.331 eV as illustrated in Fig. 2C. The peak position of A exciton emission at band edges shifts from 2.04 eV at 10 K to 1.98 eV at room temperature. The energy difference between the PL peak and the near-resonance excitation (2.088 eV) is around 100 meV at room temperature, which is much smaller than the value 290 meV for the low temperature off-resonance excitation at 2.331 eV. However, the observed polarization for off-resonance excitation at 10 K (P = 16%) is much higher than the near-resonance condition at room temperature (P = 10%). It clearly shows that the depolarization cannot be attributed to single process, namely the off-resonance excitation or band-edge phonon scattering only (10).Open in a separate windowFig. 2.Photoluminescence of monolayer WS₂ under circularly polarized excitation. (A) Polarization resolved luminescence spectra with σ+ detection (red) and σ− detection (black) under near-resonant σ+ excitation (2.088 eV) at 10 K. Peak A is the excitonic transition at band edges of K (K′) valleys. Opposite helicity of PL is observed under σ− excitation. Inset presents the degree of the circular polarization at the prominent PL peak. (B) The degree of the circular polarization as a function of temperature. The curve (red) is a fit following a Boltzmann distribution where the intervalley scattering by phonons is assumed. (C) Photoluminescence spectrum under off-resonant σ+ excitation (2.33 eV) at 10 K. The red (black) curve denotes the PL circular components of σ+ (σ−).Next we study the PL from bilayer WS₂. Fig. 3 shows the PL spectrum from bilayer WS₂. The peak labeled as “I” denotes the interband optical transition from the indirect band gap, and the peak A corresponds to the exciton emission from direct band transition at K and K′ valleys. Although bilayer WS₂ has an indirect gap, the direct interband optical transition at K and K′ valleys dominates the integrated PL intensity as the prerequisite of phonon/defect scattering is waived for direct band emission and the direct gap is just slightly larger than the indirect band gap in bilayers. Fig. 3A displays surprisingly robust PL circular dichroism of A exciton emission under circularly polarized excitations of 2.088 eV (resonance) and 2.331 eV (off resonance). The degree of circular polarization of A exciton emission under near-resonant σ± excitation is near unity (around 95%) at 10 K and preserves around 60% at room temperature. In contrast, the emission originating from indirect band gap is unpolarized in all experimental conditions.Open in a separate windowFig. 3.Photoluminescence of bilayer WS₂ under circularly polarized excitations. (A) Polarization-resolved luminescence spectra with components of σ+ (red) and σ− (black) under near-resonant σ+ excitation (2.088 eV) at 10 K. Peak A is recognized as the excitonic transition at band edge of direct gap. Peak I originates from the indirect band-gap emission, showing no polarization. Inset presents the circular polarization of the A excitonic transition around the PL peak. Opposite helicity of PL is observed under σ− excitation. (B) The degree of circular polarization as a function of temperature (black). The curve (red) is a fit following a Boltzman distribution where the intervalley scattering by phonons is assumed. (C) Photoluminescence spectrum of components of σ+ (red) and σ− (black) under off-resonance σ+ excitation (2.33 eV) at 10 K. A nonzero circular polarization P is only observed at emissions from A excitons.To exclude the potential cause of charge trapping or substrate charging effect, we study the polarization-resolved PL of bilayer WS₂ with an out-plane electric field. Fig. 4A shows the evolution of PL spectra in a field-effect-transistor-like device under circularly polarized excitations of 2.088 eV and an electric gate at 10 K. The PL spectra dominated by A exciton show negligible change under the gate bias in the range of −40 to 20 V. The electric-conductance measurements show that the bilayer WS₂ stays at the electrically intrinsic state under the above bias range. The PL spectra can be safely recognized as emissions from free excitons. As the gate bias switches further to the positive side (>20 V), the PL intensity decreases, and the emission from electron-bounded exciton “X⁻,” the so-called trion emerges and gradually raises its weight in the PL spectrum (11, 12). The electron–exciton binding energy is found to be 45 meV. Given only one trion peak in PL spectra, the interlayer trion (formed by exciton and electron/hole in different layers) and intralayer trion (exciton and electron/hole in the same layer) could not be distinguished due to the broad spectral width (13). Both the free exciton and trion show slight red shifts with negative bias, presumably as a result of quantum-confined stark effect (14). At all of the bias conditions, the degree of circular polarization of the free exciton and trion stays unchanged within the experiment sensitivity as shown in Fig. 4C.Open in a separate windowFig. 4.Electric-doping-dependent photoluminescence spectrum of bilayer WS₂ field-effect transistor. (A) Luminescence spectra of bilayer WS₂ at different gate voltage under near-resonant σ+ excitation (2.088 eV) at 10 K. X and X⁻ denote neutral exciton and trion, respectively. Green curve is a fitting consisting of two Lorentzian peak fits (peak I and X⁻) and one Gaussian peak fit (peak X). (B) Intensity of exciton and trion emissions versus gate. (Upper) The gate-dependent integral PL intensity consisting of exciton (X) and trion (X⁻). (Lower) The ratio of the integral PL intensity of exciton versus that of trion, as a function of the gate voltage. (C) Degree of circular polarization of exciton (X, red) and trion (X⁻, blue) versus the gate.It is also unlikely that the high polarization in bilayers results from the isolation of the top layer from the environments, as similar behaviors are observed in monolayer and bilayer WS₂ embedded in polymethyl methaccrylate (PMMA) matrix or capped with a 20-nm-thick SiO₂ deposition. The insensitivity of the circular-polarization degree on bias and environments rules out the possibility that the effects of Coulomb screening, charge traps, or charge transfers with substrates are the major causes for the robust circular dichroism in bilayers against monolayers.One potential cause may result from the shorter lifetime of excitons at K (K′) valley for bilayer system. The band gap shifts from K and K′ points of the Brillouin zone in monolayers to the indirect gap between the top of the valence band at Γ points and the bottom of the conduction band in the middle of K and Γ points in bilayers. Combining our time-resolved pump-probe reflectance experiments (Supporting Information) and the observed relative PL strength between monolayer and bilayer (10:1), we infer the exciton lifetime at K (K′) valleys around 10 ps, a fraction of that at monolayers. If we assume (i) the PL circular polarization P=P01+2ττk, where P₀ is the theoretical limit of PL polarization, and τ_k and τ denote the valley lifetime and exciton lifetime respectively; and (ii) the valley lifetime is the same for both monolayers and bilayers, the shorter exciton lifetime will lead to significantly higher PL polarization. However, the difference in exciton lifetime between bilayers and monolayers is not overwhelming enough to be the major cause of robust polarization observed in the time-integrated PL in bilayers.In monolayer WS₂ under circularly polarized resonant excitations, the depolarization mainly comes from the K ? K′ intervalley scattering. In bilayers, the depolarization could be either via K ? K′ intervalley scattering within the layer in a similar way as in monolayers, or via interlayer hopping, which also requires spin flip. As we discussed above, the interlayer hopping at K valley is suppressed in WS₂ as a result of strong SOC in WS₂ and spin–layer–valley coupling, which were experimentally proved by the circular dichroism in PL from bilayers. The robust polarization in bilayers implies that the intervalley scattering within a layer is diminished compared with that in monolayers. There are two prerequisites for intervalley scattering within layers: conservation of crystal momentum and spin flip of holes. The crystal momentum conservation could be satisfied with the involvement of phonons at K points in the Brillouin zone or atomic size defects, presumably sharing the similar strength in monolayers and bilayers. Spin-flip process could be realized by three different spin scattering mechanisms, namely D’yakonov–Perel (DP) mechanism (15), Elliot–Yaffet (EY) mechanism (16), and Bir–Aronov–Pikus (BAP) mechanism (17, 18). The DP mechanism acts through a Lamor precession driven by electron wavevector k dependent spin–orbit coupling. It is thought to be negligible for spin flip along out-plane direction as the mirror symmetry with respect to the plane of W atoms secures a zero out-plane crystal electric field. Another possible driving force behind the DP mechanism could be the asymmetry owing to the interface with the substrate. This can be excluded by the similar behaviors, where the monolayers and bilayers WS₂ are embedded in PMMA matrix or capped with a thin layer of SiO₂. The negligible effect of electric gating on polarization also implies that the DP mechanism is weak in monolayer and bilayer WS₂; the EY mechanism originates from scattering with phonons and defects. Its strength in bilayers and monolayers is likely to be at similar scale, and bilayers even have more low-frequency collective vibrational modes (19). Therefore, EY mechanism is unlikely to be the cause here; the BAP mechanism originates from the electron–hole exchange interaction. In monolayer and bilayer TMDCs, the optical features are dominated by the Wannier type, yet giant excitonic effect, and the exciton-binding energy in such intrinsic 2D semiconductors is estimated to be 0.6 ∼ 1 eV (20, 21). This giant exciton-binding energy indicates a mixture of electron and hole wavefunctions and, consequently, strong exchange interaction, which may contribute to the spin flip and intervalley scattering (5, 22). As the conduction band has a band mixing at K points, the spin flip of the electron would be a quick process. An analogous scenario is that the spin of holes relaxes in hundreds of femtoseconds or fewer in GaAs as a result of band mixing and spin–orbit coupling. The electron spin flip could lead to hole spin flip via strong exchange interaction accompanying intervalley scattering, which is realized by the virtual annihilation of a bright exciton in the K valley and then generation in the K′ valley or vice versa (22). This non-single-particle spin relaxation leads to valley depolarization instead of the decrease of luminescence intensity that results from coupling with dark excitons. Generally, the exciton-binding energy decreases with the relaxation of spatial confinement. However, first principle calculation shows that monolayer and bilayer WS₂ share the similar band dispersion and effective masses around K valley in their Brillouin zone as a result of spin–valley coupling (7). It implies that the binding energy of excitons around K valley in bilayer WS₂ is similar to or slightly less than that in monolayer WS₂. As the exchange interaction is roughly proportional to the square of exciton binding energy, the spin-flip rate and consequently intervalley scattering via exciton exchange interactions is presumably comparable or smaller to some extent in bilayer WS₂ (Supporting Information). Nevertheless, this is unlikely the major cause of the anomalously robust valley polarization in bilayer WS₂.Another possibility includes extra spin-conserving channels via intermediate intervalley-interlayer scatterings in bilayer WS₂, which are absent in monolayers (23). The extra spin-conserving channel may compete with the spin-flip process and reduce the relative weight of spin-flip intervalley scattering to some extent. However, the mechanism and the strength are unclear so far. Overall, the robust circular polarization in bilayers likely results from combined effects of the shorter exciton lifetime, smaller exciton-binding energy, extra spin-conserving channels, and the coupling of spin, layer, and valley degrees of freedom, indicating the relatively weak intervalley scattering in bilayer system. Further quantitative study is necessary to elaborate the mechanism.We also investigated the PL from bilayer WS₂ under a linearly polarized excitation. A linearly polarized light could be treated as a coherent superposition of two opposite-helicity circularly polarized lights with a certain phase difference. The phase difference determines the polarization direction. In semiconductors, a photon excites an electron–hole pair with the transfer of energy, momentum, and phase information. The hot carriers energetically relax to the band edge in a quick process around 10⁻¹ ∼ 10¹ ps through runs of inelastic and elastic scatterings, e.g., by acoustic phonons. During the quick relaxation process, generally the phase information randomizes and herein coherence fades. In monolayer TMDCs, the main channel for carrier relaxation is through intravalley scatterings including Coulomb interactions with electron (hole) and inelastic interactions with phonons, which are valley independent and preserve the relative phase between K and K′ valleys (24). In bilayer WS₂, the suppression of intervalley scattering consequently leads to the suppression of inhomogeneous broadening in carrier’s phase term. Subsequently, the valley coherence demonstrated in monolayer WSe₂ (24) is expected to be enhanced in bilayers (13). The valley coherence in monolayer and bilayer WS₂ could be monitored by the polarization of PL under linearly polarized excitations.Fig. 5A shows the linearly polarized components of PL under a linearly polarized excitation of 2.088 eV at 10 K. The emission from indirect band gap is unpolarized and A exciton displays a pronounced linear polarization following the excitation. The degree of linear polarization P=I(‖)−I(⊥)I(‖)+I(⊥) is around 80%, where I(∥)(I(⊥)) is the intensity of PL with parallel (perpendicular) polarization with respect to the excitation polarization. In contrast, the linear polarization is much weaker in monolayer samples (4% under the same experimental conditions, as shown in Fig. 5B). As presented in Fig. 5C, the polarization of A exciton is independent of crystal orientation and exactly follows the polarization of excitations. The degree of the linear polarization in bilayer WS₂ slightly decreases with the increased temperature and drops from 80% at 10 K to 50% at room temperature (Fig. 5D). This is the paradigm of the robust valley coherency in bilayer WS₂.Open in a separate windowFig. 5.Linearly polarized excitations on monolayer and bilayer WS₂. (A) Linear-polarization-resolved luminescence spectra of bilayer WS₂ under near-resonant linearly polarized excitation (2.088 eV) at 10 K. Red (black) presents the spectrum with parallel (cross) polarization with respect to the linear polarization of excitation source. A linear polarization of 80% is observed for exciton A, and the indirect gap transition (I) is unpolarized. (B) Linear-polarization-resolved luminescence spectra of monolayer WS₂ under near-resonant linearly polarized excitation (2.088 eV) at 10 K. Red (black) denotes the spectrum with the parallel (cross) polarization with respect to the linear polarization of excitation source. The linear polarization for exciton A in monolayer WS₂ is much weaker, with a maximum value of 4%. (C) Polar plot for intensity of the exciton A in bilayer WS₂ (black) as a function of the detection angle at 10 K. Red curve is a fit-following cos²(θ). (D) The degree of linear polarization of exciton A in bilayer WS₂ (black) as a function of temperature. The curve (red) is a fit following a Boltzmann distribution where the intervalley scattering by phonons is assumed. (E) Electric doping dependence of the linear polarization of exciton A in bilayer WS₂ at 10 K.The linear polarization of both exciton and trion in bilayer, contrasting to the circular polarization, which is insensitive to the electric field in the range, shows a weak electric gating dependence as shown in Fig. 5E. The PL linear polarization, presenting valley coherence, decreases as the Fermi level shifts to the conduction band. It does not directly affect intervalley scattering within individual layers and makes negligible change in circular dichroism. Nevertheless, the electric field between the layers induces a layer polarization and slightly shifts the band alignments between the layers by different amounts in conduction and valence bands (13, 25), although the shift is indistinguishable in the present PL spectra due to the broad spectral width. The layer polarization and the shift of band alignments may induce a relative phase difference between two layers and therefore affect the PL linear polarization via interference. Further study is needed to fully understand the mechanism.In summary, we demonstrated anomalously robust valley polarization and valley polarization coherence in bilayer WS₂. The valley polarization and valley coherence in bilayer WS₂ are the direct consequences of giant spin–orbit coupling and spin valley coupling in WS₂. The depolarization and decoherence processes are greatly suppressed in bilayer, although the mechanism is ambiguous. The robust valley polarization and valley coherence make bilayer WS₂ an intriguing platform for spin and valley physics.     

Urinary netrin-1 and KIM-1 as early biomarkers for septic acute kidney injury

Background: Acute kidney injury (AKI) during sepsis is associated with poor outcome. However, diagnosis of AKI with serum creatinine (SCr) level change is neither highly sensitive nor specific. Therefore, identification of novel biomarkers for early diagnosis of AKI is desirable. Aims: To evaluate the capacity of combining urinary netrin-1 and human kidney injury molecule type 1 (KIM-1) in the early diagnosis of septic AKI. Methods: We prospectively recruited 150 septic patients from Jun 2011 to Jun 2013 at Zhejiang Provincial People's Hospital, China. SCr, urinary netrin-1, and KIM-1 levels were recorded at 0, 1, 3, 6, 24, and 48?h of ICU admission and compared between AKI and non-AKI patients. In addition, we investigated the prognostic value of netrin-1 and KIM-1 between non-survivors and survivors in septic AKI patients. Results: SCr levels started to show elevation after 24?h of ICU admission. However, netrin-1 levels increased significantly as early as 1?h, peaked at 3–6?h and remained elevated up to 48?h of ICU admission in septic AKI patients. KIM-1 increased significantly by 6?h, peaked at 24?h and remained significantly elevated until 48?h of ICU admission. Furthermore, we observed significant higher urinary KIM-1 levels at 24?h and 48?h in non-survivors compared to survivors in AKI patients. Conclusions: Our results suggest that both netrin-1 and KIM-1 are clinically useful as early biomarkers in the diagnosis of septic AKI. In addition, persistent elevation of urinary KIM-1 level may be associated with poor prognosis.