MIP-1α/CCL3-mediated maintenance of leukemia-initiating cells in the initiation process of chronic myeloid leukemia

In the initiation process of chronic myeloid leukemia (CML), a small number of transformed leukemia-initiating cells (LICs) coexist with a large number of normal hematopoietic cells, gradually increasing thereafter and eventually predominating in the hematopoietic space. However, the interaction between LICs and normal hematopoietic cells at the early phase has not been clearly delineated because of the lack of a suitable experimental model. In this study, we succeeded in causing a marked leukocytosis resembling CML from restricted foci of LICs in the normal hematopoietic system by direct transplantation of BCR-ABL gene–transduced LICs into the bone marrow (BM) cavity of nonirradiated mice. Herein, we observed that BCR-ABL⁺lineage⁻c-kit⁻ immature leukemia cells produced high levels of an inflammatory chemokine, MIP-1α/CCL3, which promoted the development of CML. Conversely, ablation of the CCL3 gene in LICs dramatically inhibited the development of CML and concomitantly reduced recurrence after the cessation of a short-term tyrosine kinase inhibitor treatment. Finally, normal hematopoietic stem/progenitor cells can directly impede the maintenance of LICs in BM in the absence of CCL3 signal.Chronic myeloid leukemia (CML) is a myeloproliferative neoplasm (MPN) resulting from the neoplastic transformation of hematopoietic stem cells (HSCs). CML undergoes a triphasic process, a chronic phase, an accelerated phase, and a terminal blast crisis (Lahaye et al., 2005). More than 90% of CML cases are associated with the presence of the Philadelphia chromosome. This chromosome arises from a reciprocal translocation between chromosomes 9 and 22 and forms the breakpoint cluster region with a constitutively activated tyrosine kinase, BCR-ABL fusion protein (Ren, 2005; Melo and Barnes, 2007). This protein is a pathogenic protein in CML (Sawyers, 1999), and maintenance of BCR-ABL–expressing leukemia-initiating cells (LICs) in the BM is crucial for initiating the chronic phase of CML (Koschmieder et al., 2005).Zhang et al. (2012) observed several characteristic changes in the BM microenvironment of mice developing CML-like myeloproliferative disease, such as BM hypercellularity and myeloid cell infiltration into spleen (SP). Moreover, they detected an altered chemokine/cytokine expression pattern in the BM, including down-regulation of SDF-1/CXCL12 and up-regulation of MIP-1α/CCL3, MIP-1β/CCL4, IL-1α, IL-1β, and TNF. They further obtained similar observations on human CML patients. Based on these observations, they proposed that altered chemokine/cytokine expression in BM may contribute to the preferential proliferation of LICs in the BM microenvironment, to displace the normal hematopoietic cells, although they did not clarify the molecular and cellular mechanisms in more detail.Chemokines are produced by a wide variety of hematological and stromal cells and exhibit diverse activities on various types of BM-derived cells. Evidence is accumulating to indicate that a CC chemokine, MIP-1α/CCL3, has direct inhibitory activities on normal hematopoietic stem/progenitor cell (HSPC) growth (Graham et al., 1990; Dunlop et al., 1992; Maze et al., 1992; Broxmeyer et al., 1993). Induction of BCR-ABL expression in vivo can cause the aberrant expression of CCL3 in the BM (Zhang et al., 2012). Moreover, CCL3-mediated signal can regulate the in vitro proliferation of normal HSPCs and LICs in distinct ways (Eaves et al., 1993; Chasty et al., 1995), depending on the kinase activity of Abl protein (Wark et al., 1998). Furthermore, IFN-α–induced CCL3 production by BM-derived stromal cells enhanced β1 integrin–dependent adhesion of LICs to the stromal cells to restore normal hematopoiesis in CML (Bhatia et al., 1995). These observations suggest that CCL3 can contribute to the interaction between LICs and normal hematopoietic system in the initiation process of CML development (Zhang et al., 2012), but its precise roles remain unclear because of the lack of a suitable experimental model.Murine CML-like myeloproliferative disease can be induced by transferring human-derived BCR-ABL oncogene–transduced primitive BM cells to a lethally irradiated host (Pear et al., 1998; Li et al., 1999). This experimental model has been widely used to examine the in vivo leukemogenic role of the BCR-ABL oncogene in CML development. However, in this model, lethal irradiation completely breaks down the normal hematopoietic system to enable intravenously injected BCR-ABL⁺ leukemic cells to home to the BM to grow and develop CML. Thus, this model is not helpful in elucidating the role of the BM microenvironment in CML development. Furthermore, lethal irradiation induced a temporal leukopenia, a condition that can have a profound impact on CML pathology by compensatory overproduction of various growth factors (Singh et al., 2012). Hence, to observe the course of CML development under the steady-state, an inducible BCR-ABL transgenic mouse, which can express the BCR-ABL gene under the control of a Tet-regulated 3′ enhancer of the murine stem cell leukemia gene, was established (Koschmieder et al., 2005). This well-designed transgenic model enables the study of the function of LICs in the condition closely resembling that in CML patients. However, in this experimental model, it is not easy to selectively tag leukemia cells with mutated BCR-ABL gene for the examination of leukemia cell trafficking. Moreover, it is laborious to introduce a gene mutation into either leukemia cells or normal hematopoietic cells.To circumvent these problems, we initially attempted to establish an experimental CML model under nonirradiated conditions. We transduced c-kit⁺lineage⁻Sca-1⁺ (KLS⁺) HSPCs with BCR-ABL oncogene using retroviral vector and injected the resultant cells directly into the BM cavity in nonirradiated immune-deficient nude mice. In the early phase of this model, only <500 BCR-ABL⁺KLS⁺ LICs are presumed to coexist with a large number of normal residual hematopoietic cells. However, this procedure succeeded in the development of a CML-like disease with a marked leukocytosis and splenomegaly in nonirradiated and BM-preserved host. Moreover, LICs moved to the contralateral site of BM while expanding in the injected site of BM. Thus, this novel model is quite helpful to clarify the interaction between normal hematopoietic system and leukemic cells, particularly in the early phase of CML development, and the trafficking of LICs to other hematopoietic tissues. By using this model, we have obtained definitive evidence to indicate an indispensable role of leukemia cell–derived CCL3 in the maintenance of LICs in BM for subsequent CML development.     

Multi-stage constant-current charging protocol for a high-energy-density pouch cell based on a 622NCM/graphite system

A novel multi-stage-constant-current (MS-CC) charging protocol, which charges high-energy-density lithium-ion cells (LICs) at a faster rate, is presented herein. In this work, the 0–80% state of charge (SoC), according to the maximum charging rate, yields acceptable results for different SoCs, and the charging process is divided into three parts. Twelve groups of experiments are designed under the desired conditions of avoiding lithium plating and using a charging time of less than 36 min, and 1.5C constant current charging is used as a comparison experiment. The full pouch cells are dismantled, and the lithium deposition after 1.5C charging is more extensive than that after the MS-CC charging protocol. In addition, the capacity retention for 1.5C charging is 95.7%, while those for the 12 MS-CC charging protocol groups are within the range of 99.5–100.0% after the 300th cycle at 25 °C. When the temperature is 25 °C and 50 °C, the capacity retention of the 12 MS-CC charging protocol groups remains similar, but when the temperature drops to 10 °C, the capacity retention decreases except for the 2.0–1.5–0.9C and 1.8–1.5–0.9C groups. At the 510th cycle, the capacity retention of the 2.0–1.5–0.9C and 1.8–1.5–0.9C groups is 99.6% and 99.9%, respectively; the values of the other 10 groups are between 95.0% and 98.2%. The excellent electrochemical performances of the MS-CC charging protocol may be due to the minimal damage of cell materials caused by the step-type high-rate charging process; thus, the degree of polarization is small. Furthermore, compared with the conventional constant constant-current (CC) charging procedure, MS-CC charging greatly shortens the charging time.

A novel multi-stage-constant-current (MS-CC) charging protocol, which charges high-energy-density lithium-ion cells (LICs) at a faster rate, is presented herein.     

Observation of lithium stripping in super-concentrated electrolyte at potentials lower than regular Li stripping

Lithium plating/stripping was investigated under constant current mode using a copper powder electrode in a super-concentrated electrolyte of lithium bis(fluorosulfonyl)amide (LiFSA) with methylphenylamino-di(trifluoroethyl) phosphate (PNMePh) and vinylene carbonate (VC) as additives. Typical Li plating/stripping for Cu electrodes in organic electrolytes of conventional lithium batteries proceeds at potentials of several millivolts versus a Li counter electrode. In contrast, a large overpotential of hundreds of millivolts was observed for Li plating/stripping with the super-concentrated electrolyte. When Li stripping started immediately after Li plating and with no rest time between plating and stripping, two potential plateaus, i.e., two-step Li stripping, was observed. The potential plateau for the 1^st stripping step appeared at −0.2 V versus a Li metal counter electrode. The electrical capacity for the 1^st stripping step was 0.04 mA h cm⁻², which indicates irregular Li stripping. Two-step Li stripping was also recorded using cyclic voltammetry. The electrochemical impedance spectroscopy (EIS) studies indicated that the two-step Li stripping behaviour reflected two different solid electrolyte interphases (SEIs) on electrodeposited Li in a Cu electrode. The SEI for the 1^st-step stripping was in a transition period of the SEI formation. The open circuit voltage (OCV) relaxation with an order of tens of hours was detected after Li plating and before Li stripping. The in operando EIS study suggested a decrease of the charge transfer resistance in the Cu powder electrode during the OCV relaxation. Since the capacitance for the voltage relaxation was a dozen microfarads, it had a slight contribution to the 1^st-step Li stripping behaviour. The voltage relaxation indicated the possibility that it is difficult for Li ions to be electrodeposited or that the Li plating is in a quasi-stable state.

When Li plating/stripping was conducted on a Cu powder electrode in a super-concentrated electrolyte of LiFSA and PNMePh, two potential plateaus of the Cu electrode for Li stripping were observed at −0.2 V and +1.0 V versus a Li counter electrode.     

Spinel LiMn2O4 nanoparticles fabricated by the flexible soft template/Pichini method as cathode materials for aqueous lithium-ion capacitors with high energy and power density

Spinel LiMn₂O₄ (LMO) with a three-dimensional structure has become one of the cathode materials that has gained the most interest due to its safety, low price and abundant resources. However, the lithium ion transmission is limited by large particle size and particle agglomeration of LMO. Thus, reducing the particle size and agglomeration of LMO can effectively improve its lithium ion transmission. Here, we synthesized a LMO cathode material with a nanoscale crystal size using the flexible expanded graphite (EG) soft template and Pichini method. EG-controlled particle size and particle agglomeration of LMO is conducive to charge transfer and diffusion of lithium ions between LMO and the electrolyte, meanwhile, there are more redox sites on the nanosized LMO particles, which makes the redox reaction of LMO more thorough during the charge and discharge process, resulting in high capacitance performance. In order to obtain the considerably required lithium-ion capacitors (LICs) with high energy density and power density, we assembled aqueous LMO//activated carbon (AC) LICs with 5 M LiNO₃ as the aqueous electrolytes, which are environmentally friendly, safe, low cost and have higher electrical conductivity than organic electrolytes. The optimal LIC has an energy density of 32.63 W h kg⁻¹ at a power density of 500 W kg⁻¹ and an energy density of 8.06 W h kg⁻¹ at a power density of 10 000 W kg⁻¹, which is higher than most of the LMO-based LICs in previous reports. After 2000 cycles, the specific capacitance retention rate was 75.9% at a current density of 3 A g⁻¹. Therefore, our aqueous LMO//AC LICs synthesized by the soft template/Pichini method have wide prospects and are suitable for low-cost, high-safety and high-power applications.

LiMn₂O₄ nanoparticles were synthesized by flexible Pichini method with expanded graphite as the soft template to effectively control particle size and agglomeration, contributing to high energy/power densities of its aqueous lithium-ion capacitor.     

Suppressing self-discharge of Li–B/CoS2 thermal batteries by using a carbon-coated CoS2 cathode

Thermal batteries with molten salt electrolytes are used for many military applications, primarily as power sources for guided missiles. The Li–B/CoS₂ couple is designed for high-power, high-voltage thermal batteries. However, their capacity and safe properties are influenced by acute self-discharge that results from the dissolved lithium anode in molten salt electrolytes. To solve those problems, in this paper, carbon coated CoS₂ was prepared by pyrolysis reaction of sucrose at 400 °C. The carbon coating as a physical barrier can protect CoS₂ particles from damage by dissolved lithium and reduce the self-discharge reaction. Therefore, both the discharge efficiency and safety of Li–B/CoS₂ thermal batteries are increased remarkably. Discharge results show that the specific capacity of the first discharge plateau of carbon-coated CoS₂ is 243 mA h g⁻¹ which is 50 mA h g⁻¹ higher than that of pristine CoS₂ at a current density of 100 mA cm⁻². The specific capacity of the first discharge plateau at 500 mA cm⁻² for carbon-coated CoS₂ and pristine CoS₂ are 283 mA h g⁻¹ and 258 mA h g⁻¹ respectively. The characterizations by XRD and DSC indicate that the carbonization process has no noticeable influence on the intrinsic crystal structure and thermal stability of pristine CoS₂.

Suppressing self-discharge of Li–B/CoS₂ thermal batteries through modifying the CoS₂ cathode with a protective carbon coating layer.     

Sorting efficiency

Computers and the tasks they perform are becoming increasingly important in medicine. It behooves medical personnel to become familiar with some computer functions so that they may be in a better position to demand and evaluate a given implementation. One very basic computer task is sorting information. Some general principles of computing efficiency are discussed, as well as the standard O notation. A simple sort,bubblesort, is discussed and analyzed. A second elementary sort,insertionsort, is considered in relation to its more sophisticated descendant,shellsort. The most efficient in memory sort,quicksort (and its various descendants), is likewise examined, and the advantages and disadvantages of each variant are discussed in some detail, as well as methods that may enhance speed and resource utilization. Finally,mergesort, which is used in sorting large files resident in mass-storage devices, is discussed, along with its particular advantages.     

Enhanced open-circuit voltages and efficiencies: the role of oxidation state of molybdenum oxide buffer layer in polymer solar cells

Molybdenum oxide (MoO_x) is widely used as a buffer layer in optoelectronic devices to improve the charge extraction efficiency. The oxidation state of MoO_x plays an important role in determining its electrical properties. However, there are few studies on the oxidation state to further guide the optimization of the MoO_x buffer layer. In this work, inverted-structured polymer solar cells (PSCs) with a MoO_x buffer layer were fabricated. Post-air annealing was used to control the cation valence state in MoO_x. X-ray photoelectron spectroscopy (XPS), ultraviolet photoelectron spectroscopy (UPS), atomic force microscopy (AFM) and transient photocurrent (TPC) were employed to study the valence state, energy level, morphology of the MoO_x layers and the photovoltaic property and charge transfer efficiency of the devices. It was found that the oxidation state was effectively improved by the post-annealing process. As a result, the work function of MoO_x was raised and the hole mobility was improved. The open-circuit voltages and the efficiencies of PTB7-Th:PC₇₁BM based PSCs were enhanced from 0.77 V and 8.66% to 0.81 V and 10.01%, respectively. The results show that high oxidation state MoO_x provides optimized energy level alignment, reduced defects and better charge transfer efficiency, which is more in line with the requirement of buffer layer materials for optoelectronic applications.

The high oxidation state MoO_x buffer layer provides better level alignment and charge transfer efficiency, improving the open-circuit voltages and the efficiencies of polymer solar cells.     

Searching for collaboration in international nursing partnerships: a literature review

GEORGE E.K. & MEADOWS‐OLIVER M. (2013) Searching for collaboration in international nursing partnerships: a literature review. International Nursing Review 60 , 31–36 Background: Nurses from low‐income countries (LICs) face extreme nursing shortages, faculty shortages and a lack of professional development opportunities. Nurses from high‐income countries (HICs) can leverage their wealth of resources to collaborate with nursing colleagues in LICs to expand clinical, education and research capacity. In turn, nurses from HICs gain stronger competency in the care they provide, improved communication skills and an increased understanding of global health issues. Aim: The purpose of this literature review is to identify international nursing clinical, education and research partnerships among nurses from LICs and HICs and to analyse the degree of collaboration involved in each partnership using DeSantis' counterpart concept. Methods: We conducted a systematic review of international nursing partnerships in the scientific literature from January 2001 to July 2012. A total of nine articles met inclusion criteria for analysis. Findings: All of the articles discuss lessons learnt in building international nursing partnerships among nurses from HICs and LICs. However, the articles failed to meet the criteria set forth by DeSantis' counterpart concept to achieve fully collaborative nursing partnerships. Conclusions: International nursing partnerships require more foresight and planning to create partnerships in which the benefits derived by nurses from LICs equal those of their colleagues from HICs. By striving for such collaboration, international nursing partnerships can help build nursing clinical, education and research capacity in LICs.     

MoS2/carbon composites prepared by ball-milling and pyrolysis for the high-rate and stable anode of lithium ion capacitors

Lithium ion capacitors (LICs), bridging the advantages of batteries and electrochemical capacitors, are regarded as one of the most promising energy storage devices. Nevertheless, it is always limited by the anodes that accompany with low capacity and poor rate performance. Here, we develop a versatile and scalable method including ball-milling and pyrolysis to synthesize exfoliated MoS₂ supported by N-doped carbon matrix derived from chitosan, which is encapsulated by pitch-derived carbon shells (MoS₂/CP). Because the carbon matrix with high nitrogen content can improve the electron conductivity, the robust carbon shells can suppress the volume expansion during cycles, and the sufficient exfoliation of lamellar MoS₂ can reduce the ions transfer paths, the MoS₂/CP electrode delivers high specific capacity (530 mA h g⁻¹ at 100 mA g⁻¹), remarkable rate capability (230 mA h g⁻¹ at 10 A g⁻¹) and superior cycle performance (73% retention after 250 cycles). Thereby, the LICs, composed of MoS₂/CP as the anode and commercial activated carbon (21 KS) as the cathode, exhibit high power density of 35.81 kW kg⁻¹ at 19.86 W h kg⁻¹ and high energy density of 87.74 W h kg⁻¹ at 0.253 kW kg⁻¹.

MoS₂/carbon composites prepared by ball-milling and pyrolysis for the high-rate anode of lithium ion capacitors.     

Porous lithium cobalt oxide fabricated from metal–organic frameworks as a high-rate cathode for lithium-ion batteries

Porous materials have many applications, such as energy storage, as catalysts and adsorption etc. Nevertheless, facile synthesis of porous materials remains a challenge. In this work, porous lithium cobalt oxide (LiCoO₂) is fabricated directly from Co-based metal–organic frameworks (MOFs, ZIF-67) and lithium salt via a facile solid state annealing approach. The temperature affect on the microstructure of LiCoO₂ is also investigated. The as-prepared LiCoO₂ shows a uniform porous structure. As a cathode for a lithium-ion battery (LIB), the LiCoO₂ delivers excellent stability and superior rate capability. The as-prepared porous LiCoO₂ delivers a reversible capacity of 106.5 mA h g⁻¹ at 2C and with stable capacity retention of 96.4% even after 100 cycles. This work may provide an alternative pathway for the preparation of porous materials with broader applications.

Porous lithium cobalt oxide is fabricated directly from Co-based metal–organic frameworks and lithium salt via a facile solid state annealing approach.     

One-step fabrication of nanosized LiFePO4/expanded graphite composites with a particle growth inhibitor and enhanced electrochemical performance of aqueous Li-ion capacitors

It is reported that olivine-type lithium iron phosphate (LFP) for Li-ion batteries is one of the most widely utilized cathode materials, but its high-power applications are limited due to its intrinsically poor ion transfer rate and conductivity. Therefore, it is highly desired to fabricate LFP Li-ion capacitors (LICs) with high power performance and excellent cyclic reversibility, especially in safe, low cost and environmentally friendly aqueous electrolytes. Here, we fabricate LFP/expanded graphite (EG) nanocomposites by a one-step process, in which polyethylene glycol (PEG) is used as the particle growth inhibitor combined with vacuum infiltration of the LFP precursor into EG as a conductive sub-phase, and further investigate their high-power performance in aqueous LICs. Embedding spherical LFP nanoparticles with well-controlled size and agglomeration into the pores of EG and wrapping LFP nanoparticles by EG films contribute to the rapid electron and ion diffusion in LFP/EG composites, resulting in excellent cyclic reversibility and rate performance of LFP/EG composites. The aqueous LFP/EG//active carbon (AC) LICs were assembled in LiNO₃ electrolytes with LFP/EG composites and AC as the positive and negative electrodes, respectively. The optimal LIC shows a power density of 2367.9 W kg⁻¹ at an energy density of 6.5 W h kg⁻¹, dramatically favorable rate characteristics and excellent cycle life with 82.1% capacitance retention of its primary capacitance at 2 A g⁻¹ after 6000 cycles, markedly higher than those of the commercial LFP LIC. The presented aqueous LFP/EG//AC LICs with excellent electrochemical performance are expected to have broad high-power appliances that are cost-sensitive and highly secure.

It is reported that olivine-type lithium iron phosphate (LFP) for Li-ion batteries is one of the most widely utilized cathode materials, but its high-power applications are limited due to its intrinsically poor ion transfer rate and conductivity.     

Al-doped H2TiO3 ion sieve with enhanced Li+ adsorption performance

H₂TiO₃ (HTO) is considered to be one of the most promising adsorbents for lithium recovery from aqueous lithium resources duo to its highest theoretical adsorption capacity. However, its actual adsorption capacity is much lower owing to its unknown structure and incomplete leaching of lithium. After Al is doped into H₂TiO₃ (HTO-Al), the adsorption capacity of HTO-Al is 32.12 mg g⁻¹ and the dissolution of Ti is 2.53%. HTO-Al has good adsorption selectivity, and all the separation factors α are ≫1. Furthermore, HTO-Al also exhibits good cyclic stability and solubility resistance. After 5 cycles, the adsorption capacity remains 29.3 mg g⁻¹ and the dissolution rate is 1.7%. Therefore, HTO-Al has potential application value for recovering Li⁺ from aqueous lithium resources.

H₂TiO₃ (HTO) is considered to be one of the most promising adsorbents for lithium recovery from aqueous lithium resources duo to its highest theoretical adsorption capacity.     

Facile in situ growth of ZnO nanosheets standing on Ni foam as binder-free anodes for lithium ion batteries

ZnO has attracted increasing attention as an anode for lithium ion batteries. However, the application of such anode materials remains restricted by their poor conductivity and large volume changes during the charge/discharge process. Herein, we report a simple hydrothermal method to synthesize ZnO nanosheets with a large surface area standing on a Ni foam framework, which is applied as a binder-free anode for lithium ion batteries. ZnO nanosheets were grown in situ on Ni foam, resulting in enhanced conductivity and enough space to buffer the volume changes of the battery. The ZnO nanosheets@Ni foam anode showed a high specific capacity (1507 mA h g⁻¹ at 0.2 A g⁻¹), good capacity retention (1292 mA h g⁻¹ after 45 cycles), and superior rate capacity, which are better than those of ZnO nanomaterial-based anodes reported previously. Moreover, other transition metal oxides, such as Fe₂O₃ and NiO were also formed in situ on Ni foam with perfect standing nanosheets structures by this hydrothermal method, confirming the universality and efficiency of this synthetic route.

ZnO nanosheets@Ni foam anode showed a high specific capacity, good capacity retention and superior rate capacity. Moreover, other transition metal oxides were also similarly formed on Ni foam, confirming the universality and efficiency of the synthetic route.     

Quantitative spatially resolved post-mortem analysis of lithium distribution and transition metal depositions on cycled electrodes via a laser ablation-inductively coupled plasma-optical emission spectrometry method

Diminishing the loss of performance of lithium ion batteries (LIBs) is a challenge that is yet to be fulfilled. Understanding of deterioration processes and mechanisms (i.e., so-called aging) requires analytically accurate examination of aged cells. Changes in the distribution of lithium or transition metals in the LIB cells can influence their cycle and calendar life significantly. As electrochemically treated cells and especially their electrodes do not age homogeneously and the local electrochemistry (e.g. deposition patterns) is strongly dependent on surface properties, bulk analysis is not a satisfactory investigation method. Therefore, a surface sensitive method, namely laser ablation-inductively coupled plasma-optical emission spectrometry (LA-ICP-OES) is presented. LIB cells with lithium metal oxide LiNi_1/3Co_1/3Mn_1/3O₂ (NCM111) as cathode material and graphite as anode material are investigated using a 213 nm Nd:YAG laser.

An LA-ICP-OES method was developed and applied to investigate the transition metal dissolution in lithium batteries as well as lithium deposition e.g. in case of short circuits.     

Physician Preceptor Satisfaction and Productivity Across Curricula: A Comparison Between Longitudinal Integrated Clerkships And Traditional Block Rotations

Abstract

Phenomenon: Physicians are under intense pressure to improve clinical productivity. High clinical load, limited availability, and decreased clinical efficiency are well-documented barriers to precepting medical students and threaten clinical productivity. In an era of increasing medical student enrollment, these barriers have already led to a decreased availability of clinical teachers and training sites across the United States. Improved preceptor satisfaction could have a great impact on recruitment and retention of medical student preceptors and is likely linked to changes in productivity. Curriculum structure could impact both preceptor productivity and satisfaction. Comparing productivity and satisfaction of physician preceptors teaching in longitudinal integrated clerkships (LICs) to those teaching in traditional block rotations (TBRs), or in both settings (LIC-TBR), could lead to a better understanding of the impact of curriculum structure on preceptor productivity and satisfaction. Approach: Data were collected through a quantitative cross-sectional survey of outpatient physician preceptors in North Carolina in 2017. Preceptor satisfaction and student influence on productivity-related aspects of practice were analyzed with bivariate chi-square statistics and multivariate logistic regression. Findings: Analyses included 338 physician preceptors: 79 LIC (23%), 50 LIC-TBR (15%), and 209 TBR preceptors (62%). LIC preceptors were more likely to indicate being “very satisfied” with precepting than either their LIC-TBR or TBR counterparts. There were no differences in perceived productivity-related aspects of practice across the different curricula, such as patient flow, income, or physician working hours. Logistic regressions controlling for potential confounding variables suggested that those teaching in LICs were almost 3 times more likely to be “very satisfied” relative to those teaching in LIC-TBR and TBR settings and that the negative influence of students on patient flow and physician working hours had an adverse effect on preceptor satisfaction. Insights: Preceptor satisfaction was high overall, though satisfaction was significantly higher among preceptors who teach in LICs. The perceived impact of students on clinical productivity was stable across the different curricula. In an era of increasing need for physician preceptors, the higher satisfaction of those who teach in LICs should be considered in curricular design and for preceptor recruitment and retention.     

Efficient (Cu1−xAgx)2ZnSn(S,Se)4 solar cells on flexible Mo foils

Cation substitution plays a crucial role in improving the efficiency of Cu₂ZnSn(S,Se)₄ (CZTSSe) solar cells. In this work, we report a significant efficiency enhancement of flexible CZTSSe solar cells on Mo foils by partial substitution of Cu⁺ with Ag⁺. It is found that the band gap (E_g) of (Cu_1−xAg_x)₂ZnSn(S,Se)₄ (CAZTSSe) thin films can be adjusted by doping with Ag with x from 0 to 6%, and the minimum E_g is achieved with x = 5%. We also found that Ag doping can obviously increase the average grain size of the CAZTSSe absorber from 0.4 to 1.1 μm. Additionally, the depletion width (W_d) at the heterojunction interface of CAZTSSe/CdS is found to be improved. As a result, the open-circuit voltage deficit (V_oc,def) is gradually decreased, and the band tailing is suppressed. Benefiting from the enhanced open-circuit voltage (V_oc), the power conversion efficiency (PCE) is successfully enhanced from 4.34% (x = 0) to 6.24% (x = 4%), and the V_oc,def decreases from 915 to 848 mV.

Cation substitution plays a crucial role in improving the efficiency of Cu₂ZnSn(S,Se)₄ (CZTSSe) solar cells.     

Modification of the Congo red agar method to detect biofilm production by Staphylococcus epidermidis

Staphylococcus epidermidis in immunocompromised patients can cause bacteremia related to the use of catheter due to biofilm production. There are different phenotypic methods to detect biofilm formation. One method is based on culture in brain heart infusion agar (BHIA) containing sucrose and red Congo dye (original Congo red agar). Our group created a new CRA formula and we have confirmed its capacity to detect biofilm production in 210 S. epidermidis strains, including 76 (36.2%) icaAB gene–positive strains. Other parameters were also evaluated. The new CRA formula that gave the best results was BHIA with sucrose (5%), Congo red (0.08%), NaCl (1.5%), glucose (2%), and vancomycin (0.5 mg/mL) (vancomycin-modified CRA—CRAmod). The CRAmod plus vancomycin may be a promising tool and can help to determine the real participation of S. epidermidis in the infectious process.     

Enhancement of the electrochemical performance of lithium-ion batteries by SiO2@poly(2-acrylamido-2-methylpropanesulfonic acid) nanosphere addition into a polypropylene membrane

Employing electrostatic self-assembly and free radical polymerization, the surface of SiO₂ nanospheres was coated with poly(2-acrylamido-2-methylpropanesulfonic acid) (SiO₂@PAMPS) bearing strong electron withdrawing sulfonic and amide groups, enhancing the dissociation ability of the lithium salt of the liquid electrolyte and absorbing anions via hydrogen bonds. After SiO₂@PAMPS nanospheres were introduced into the polypropylene (PP) membrane (SiO₂@PAMPS/PP), the electrolyte affinity and electrolyte uptake of the composite separators were significantly improved. The ionic conductivity of SiO₂@PAMPS/PP-18% (where 18% represents the concentration of the solution used for coating) soaked in liquid electrolyte was even 0.728 mS cm⁻¹ at 30 °C, much higher than that of the pristine PP membrane. The LiFePO₄/Li half-cell with SiO₂@PAMPS/PP-18% had a discharge capacity of 148.10 mA h g⁻¹ and retained 98.67% of the original capacity even after 120 cycles at 0.5C. Even at a rate of 1.0C, the cell capacity could be maintained above 120 mA h g⁻¹. Therefore, a coating formula was developed that could considerably improve the cycling ability and high rate charge–discharge performance of lithium ion batteries.

The surface of SiO₂ nanospheres was coated with poly(2-acrylamido-2-methylpropanesulfonic acid) bearing strong electron withdrawing sulfonic and amide groups, enhancing the dissociation ability of the lithium salt of the liquid electrolyte and absorbing anions via H-bonds.