Background: In radiological emergencies with radionuclide incorporation, decorporation treatment is particularly effective if started early. Treating all people potentially contaminated("urgent treatment") m...Background: In radiological emergencies with radionuclide incorporation, decorporation treatment is particularly effective if started early. Treating all people potentially contaminated("urgent treatment") may require large antidote stockpiles. An efficacious way to reduce antidote requirements is by using radioactivity screening equipment. We analyzed the suitability of such equipment for triage purposes and determined the most efficient mix of screening units and antidote daily doses.Methods: The committed effective doses corresponding to activities within the detection limits of monitoring portals and mobile whole-body counters were used to assess their usefulness as triage tools. To determine the optimal resource mix, we departed from a large-scale scenario(60,000 victims) and based on purchase prices of antidotes and screening equipment in Germany, we calculated efficiencies of different combinations of medical countermeasure resources by data envelopment analysis. Cost-effectiveness was expressed as the costs per life year saved and compared to risk reduction opportunities in other sectors of society as well as the values of a statistical life.Results: Monitoring portals are adequate instruments for a sensitive triage after cesium-137 exposure with a high screening throughput. For the detection of americium-241 whole-body counters with a lower daily screening capacity per unit are needed. Assuming that 1% of the potentially contaminated patients actually need decorporation treatment, an efficient resource mix includes 6 monitoring portals and 25 mobile whole-body counters. The optimum mix depends on price discounts and in particular the fraction of victims actually needing treatment. The costeffectiveness of preparedness for a "dirty bomb" attack is less than for common health care, but costs for a life year saved are less than for many risk-reduction interventions in the environmental sector.Conclusion: To achieve economic efficiency a high daily screening capacity is of major importance to substantially decrease the required amount of antidote doses. Among the determinants of the number of equipment units needed, the fraction of the potentially contaminated victims that actually needs treatment is the most difficult to assess. Judging cost-effectiveness of the preparedness for "dirty bomb" attacks is an issue of principle that must be dealt with by political leaders.展开更多
In the case of a terrorist attack by a“dirty bomb”,blast injuries,external irradiation and the incorporation of radioactivity are to be expected.Departing from information about the radiological attack scenario with...In the case of a terrorist attack by a“dirty bomb”,blast injuries,external irradiation and the incorporation of radioactivity are to be expected.Departing from information about the radiological attack scenario with cesium-137 in the U.S.National Scenario Planning Guide,we estimated the radiological doses absorbed.Similar calculations were performed for a smaller plume size and a detonation in a subway.For conditions as described in the U.S.scenario,the committed effective dose amounted to a maximum of 848 mSv,even for very unfavorable conditions.Red bone marrow equivalent doses are insufcient to induce acute radiation sickness(ARS).In the case of a smaller plume size,the ARS threshold may be exceeded in some cases.In a subway bombing,doses are much higher and the occurrence of ARS should be expected.The health hazards from a dirty bomb attack will depend on the location and the explosive device.The derived Haddon matrix indicates that preparing for such an event includes education of all the medical staff about radiation effects,the time lines of radiation damages and the treatment priorities.Further determinants of the outcome include rapid evacuation even from difficult locations,the availability of a specific triage tool to rapidly identify victims at risk for ARS,the availability of an antidote stockpile and dedicated hospital beds to treat seriously irradiated victims.展开更多
Theories and experiments on dirty superconductors are complex but important in terms of both theoretical fundamentals and practical applications.These activities are even more challenging when magnetic fields are pres...Theories and experiments on dirty superconductors are complex but important in terms of both theoretical fundamentals and practical applications.These activities are even more challenging when magnetic fields are present because the field distribution,electron density of states,and superconducting pairing potentials become nonuniform.Here,we present tunneling microspectroscopic experiments on NbC single crystals and demonstrate that NbC is a homogeneous dirty superconductor.When applying magnetic fields to the samples,we found that the zero-energy local density of states and the pairing energy gap followed the explicit scaling relation proposed by de Gennes for homogeneous dirty superconductors in high magnetic fields.More significantly,our experimental findings indicate that the validity of the scaling relation extends to magnetic field strengths far below the upper critical field,calling for a new nonperturbative understanding of this fundamental property in dirty superconductors.On the practical side,we used the observed scaling relation to derive a simple and straightforward experimental scheme for estimating the superconducting coherence length of a dirty superconductor in magnetic fields.展开更多
A wide spectrum of scenarios may lead to radiation incidents and the liberation of radioactive material. In the case of a terrorist attack by a "dirty bomb", there is a risk of mechanical and thermal trauma,...A wide spectrum of scenarios may lead to radiation incidents and the liberation of radioactive material. In the case of a terrorist attack by a "dirty bomb", there is a risk of mechanical and thermal trauma, external irradiation, superficial contamination and incorporation of radioactive material. The first treatment priority must be given to the care of trauma patients with life-threatening injuries, as the health effects of radiation occur with latency. Radionuclide incorporation will lead to a longer-lasting irradiation from inside the body, associated with a higher risk of stochastic radiation effects(e.g., occurrence of tumors) in the long run. It must be expected that victims with potentially incorporated radionuclides will far outnumber trauma patients. The elimination of radionuclides can be enhanced by the administration of decorporation agents such as(Ca) Diethylenetriaminepentaacetic acid(DTPA) or Prussian blue,reducing the radiological burden of the body. There is still no consensus whether decorporation treatment should be started immediately based only on a suspicion of radionuclide incorporation("urgent approach") or if the results of internal dosimetry confirming the necessity of a treatment should be awaited, accepting the delay caused by the measurements and computations("precautionary approach"). As the therapeutic effectiveness may be substantially decreased if treatment initiation is delayed only by several days, depending on the radionuclide, the physicochemical properties of the compounds involved and the route of absorption, we favor an "urgent approach" from a medical point of view. In doubt, it seems justified to treat victims by precaution, as the adverse effects of the medication seem minimal. However, in the case of a high number of victims, an "urgent treatment approach" may require a large number of daily doses of antidotes, and therefore, adequate investments in preparedness and antidote stockpiling are necessary.展开更多
Data quality is important in many data-driven applications, such as decision making, data analysis, and data mining. Recent studies focus on data cleaning techniques by deleting or repairing the dirty data, which may ...Data quality is important in many data-driven applications, such as decision making, data analysis, and data mining. Recent studies focus on data cleaning techniques by deleting or repairing the dirty data, which may cause information loss and bring new inconsistencies. To avoid these problems, we propose EntityManager, a general system to manage dirty data without data cleaning. This system takes real-world entity as the basic storage unit and retrieves query results according to the quality requirement of users. The system is able to handle all kinds of inconsistencies recognized by entity resolution. We elaborate the EntityManager system, covering its architecture, data model, and query processing techniques. To process queries efficiently, our system adopts novel indices, similarity operator and query optimization techniques. Finally, we verify the efficiency and effectiveness of this system and present future research challenges.展开更多
This article considers the two-way multiple-input multiple-output(MIMO) relaying channels with multiple users,in which multiple users are served simultaneously by the base station(BS) with the assistance of the re...This article considers the two-way multiple-input multiple-output(MIMO) relaying channels with multiple users,in which multiple users are served simultaneously by the base station(BS) with the assistance of the relay.The transmission consists of only two phases,doubling the system throughout over traditional one-way half-duplex transmission.A zero-forcing dirty paper coding(ZFDPC) aided physical-layer network coding(PNC) scheme is proposed in this article and the achievable capacity of the ZFDPC aided PNC scheme is derived.Simulation results show that the proposed scheme outperforms the previous decode-and-forward(DF) and zero-forcing beamforming(ZFBF) aided PNC scheme due to more degrees of freedoms and the advantage of PNC.Moreover,we analyze the effect of the imperfect channel state information(CSI) from RS to users at BS side to show the robustness of the proposed ZFDPC aided PNC scheme.展开更多
Scientists use biology to purify polluted land In the old section of Suzhou, east China’s Jiangsu Province, a 40-hectare piece of land has been deserted for three years.
Rapid economic growth has taken a toll on water quality Houses lining up meandering rivers make Jiaxing in east China’s Zhejiang Province a famed water city.Yet the Venetian-style center is suffering from a water sho...Rapid economic growth has taken a toll on water quality Houses lining up meandering rivers make Jiaxing in east China’s Zhejiang Province a famed water city.Yet the Venetian-style center is suffering from a water shortage.Jiaxing has a population of more than展开更多
贵刊去年第6期曾刊登一短文,题目是:盐,迫升血压之元凶。读了该文,我开始严格控制每日的食盐摄入量,再附以药物治疗,血压果然趋于平稳。近日上网,遇一奇文,意思是人的血压与空气污染状况有涉!根据对2600个成年人的调查,得出了这样的结论...贵刊去年第6期曾刊登一短文,题目是:盐,迫升血压之元凶。读了该文,我开始严格控制每日的食盐摄入量,再附以药物治疗,血压果然趋于平稳。近日上网,遇一奇文,意思是人的血压与空气污染状况有涉!根据对2600个成年人的调查,得出了这样的结论:Pollution may cause changes in the part of the nervous system that controls blood pressure.文章又同时说明:Exactly how pollution might cause blood pressure to climb remains unclear.人体之奥妙由此可见一斑。展开更多
In the phase diagram of the nickel-based superconductor Ba_(1-x)Sr_(x)Ni_(2)As_(2),T_(C) has been found to be enhanced sixfold near the quantum critical point(QCP) x=0.71 compared with the parent compound.However,the ...In the phase diagram of the nickel-based superconductor Ba_(1-x)Sr_(x)Ni_(2)As_(2),T_(C) has been found to be enhanced sixfold near the quantum critical point(QCP) x=0.71 compared with the parent compound.However,the mechanism is still under debate.Here,we report a detailed investigation of the superconducting properties near the QCP(x≈0.7) by utilizing scanning tunneling microscopy and spectroscopy.The temperature-dependent superconducting gap and magnetic vortex state were obtained and analyzed in the framework of the Bardeen-Cooper-Schrieffer model.The ideal isotropic s-wave superconducting gap excludes the long-speculated nematic fluctuations while preferring strong electron-phonon coupling as the mechanism for T_(C) enhancement near the QCP.The lower than expected gap ratio of Δ/(k_(B) T_(C)) is rooted in the fact that Ba_(1-x)Sr_(x)Ni_(2)As_(2) falls into the dirty limit with a serious pair breaking effect similar to the parent compound.展开更多
<b><span style="font-family:Verdana;">Background: </span></b><span style="font-family:""><span style="font-family:Verdana;">Terra Firma-Forme Derm...<b><span style="font-family:Verdana;">Background: </span></b><span style="font-family:""><span style="font-family:Verdana;">Terra Firma-Forme Dermatosis (TFFD), a benign skin condition which presents with asymptomatic brown to black plaques which resemble dirty skin. </span><b><span style="font-family:Verdana;">Aim:</span></b><span style="font-family:Verdana;"> To document a new case presentation with TFFD in the Arab region which is considered as one of the differential diagnos</span></span><span style="font-family:Verdana;">e</span><span style="font-family:""><span style="font-family:Verdana;">s of dirty neck. </span><b><span style="font-family:Verdana;">Case presentation: </span></b><span style="font-family:Verdana;">A 15-year-old girl presented with a history of asymptomatic brownish dirt-like lesion on the nape and sides of the neck for 4-years duration, not resolved by wash with water and soap and confused with other dermatos</span></span><span style="font-family:Verdana;">e</span><span style="font-family:Verdana;">s like acanthosis nigricans or atopic dermatitis. The diagnosis of TFFD was confirmed when the lesions </span><span style="font-family:Verdana;">were </span><span style="font-family:""><span style="font-family:Verdana;">completely resolved after gentle swabbing with 70% isopropyl alcohol. </span><b><span style="font-family:Verdana;">Conclusion:</span></b><span style="font-family:Verdana;"> TFFD is rarely reported in Arab region and should be considered when evaluating cases of dirty neck-like presentation of atopic dermatitis or acanthosis nigricans.展开更多
In this paper, the capacity of a multiuser Multiple Input Multiple Output (MIMO) system employing the block diagonalization broadcasting scheme in presence of spatial correlation and mutual coupling is investigated. I...In this paper, the capacity of a multiuser Multiple Input Multiple Output (MIMO) system employing the block diagonalization broadcasting scheme in presence of spatial correlation and mutual coupling is investigated. It is shown by computer simulations that, in general, the presence of spatial correlation decreases the capacity of a multiuser MIMO system. However, for some particular antenna element spacing mutual coupling decreases the spatial correlation rendering an increased capacity. The optimized diagonalization broadcasting technique with a two-stage power allocation scheme is proposed and verified. The presented simulations results confirm the advantage of the proposed broadcasting scheme.展开更多
英语中有些动词,只要运用适当,可让表达更趋委婉,让对方更乐意接受。 1.建议对方别干某事时,可使用thank,allow,trouble(bother),suppose等。 I’ll thank you not to dirty my new bike. 求你别弄脏我的新自行车。句中的thank you not...英语中有些动词,只要运用适当,可让表达更趋委婉,让对方更乐意接受。 1.建议对方别干某事时,可使用thank,allow,trouble(bother),suppose等。 I’ll thank you not to dirty my new bike. 求你别弄脏我的新自行车。句中的thank you not to…意思是“求你别……”,并不表示“感谢”,说话人或许有些不耐烦了,使用了thank可不致失礼。展开更多
众所周知,西方人喜好养狗.因此英语中也就出现了许多与狗有关的习语.今年适逢又是中国人农历的狗年.在狗年谈狗更有一番情趣.Dog一词来自古英语里的docga、请看它的用法和习惯表述.1.指人(preceded by an adj)fellow or chap;a man or b...众所周知,西方人喜好养狗.因此英语中也就出现了许多与狗有关的习语.今年适逢又是中国人农历的狗年.在狗年谈狗更有一番情趣.Dog一词来自古英语里的docga、请看它的用法和习惯表述.1.指人(preceded by an adj)fellow or chap;a man or boy regarded asunpleasaht or wretchcd:e.g.a bird dog 搜罗人材的人:招揽生意的人.a clever dor 聪明伶俐的人dirty dog 坏小子;下流坯:卑污之人.a dumb dog展开更多
This paper deals with design and analysis of user scheduling and power allocation for multi-antenna OFDM systems with DPC,ZF-DPC,ZF-BF and TDMA transmit strategies.We consider the general multi-user downlink schedulin...This paper deals with design and analysis of user scheduling and power allocation for multi-antenna OFDM systems with DPC,ZF-DPC,ZF-BF and TDMA transmit strategies.We consider the general multi-user downlink scheduling problem and power minimization with multi-user rate constraints.According to the channel state,it is shown that there is a power optimal policy which selects a subset of users in each scheduling interval.We present user selection algorithms for DPC,ZF-DPC,ZF-BF and TDMA for multi-antenna OFDM system in broadcast channels,and we also present the practical water-filling solution in this paper.By the selected users with the consideration of fairness,we derive the power optimization algorithm with multi-user rate constraints.We also analyze the power duality of uplink-downlink for the transmit strategies of DPC,ZF-DPC and ZF-BF.Simulation results show that the present user-scheduling algorithm and power minimization algorithm can achieve good power performance,and that the scheduling algorithm can guarantee fairness.展开更多
文摘Background: In radiological emergencies with radionuclide incorporation, decorporation treatment is particularly effective if started early. Treating all people potentially contaminated("urgent treatment") may require large antidote stockpiles. An efficacious way to reduce antidote requirements is by using radioactivity screening equipment. We analyzed the suitability of such equipment for triage purposes and determined the most efficient mix of screening units and antidote daily doses.Methods: The committed effective doses corresponding to activities within the detection limits of monitoring portals and mobile whole-body counters were used to assess their usefulness as triage tools. To determine the optimal resource mix, we departed from a large-scale scenario(60,000 victims) and based on purchase prices of antidotes and screening equipment in Germany, we calculated efficiencies of different combinations of medical countermeasure resources by data envelopment analysis. Cost-effectiveness was expressed as the costs per life year saved and compared to risk reduction opportunities in other sectors of society as well as the values of a statistical life.Results: Monitoring portals are adequate instruments for a sensitive triage after cesium-137 exposure with a high screening throughput. For the detection of americium-241 whole-body counters with a lower daily screening capacity per unit are needed. Assuming that 1% of the potentially contaminated patients actually need decorporation treatment, an efficient resource mix includes 6 monitoring portals and 25 mobile whole-body counters. The optimum mix depends on price discounts and in particular the fraction of victims actually needing treatment. The costeffectiveness of preparedness for a "dirty bomb" attack is less than for common health care, but costs for a life year saved are less than for many risk-reduction interventions in the environmental sector.Conclusion: To achieve economic efficiency a high daily screening capacity is of major importance to substantially decrease the required amount of antidote doses. Among the determinants of the number of equipment units needed, the fraction of the potentially contaminated victims that actually needs treatment is the most difficult to assess. Judging cost-effectiveness of the preparedness for "dirty bomb" attacks is an issue of principle that must be dealt with by political leaders.
基金Bundeswehr Institute of Radiobiology,Neuherberg Str.1180937 Munich,Germany。
文摘In the case of a terrorist attack by a“dirty bomb”,blast injuries,external irradiation and the incorporation of radioactivity are to be expected.Departing from information about the radiological attack scenario with cesium-137 in the U.S.National Scenario Planning Guide,we estimated the radiological doses absorbed.Similar calculations were performed for a smaller plume size and a detonation in a subway.For conditions as described in the U.S.scenario,the committed effective dose amounted to a maximum of 848 mSv,even for very unfavorable conditions.Red bone marrow equivalent doses are insufcient to induce acute radiation sickness(ARS).In the case of a smaller plume size,the ARS threshold may be exceeded in some cases.In a subway bombing,doses are much higher and the occurrence of ARS should be expected.The health hazards from a dirty bomb attack will depend on the location and the explosive device.The derived Haddon matrix indicates that preparing for such an event includes education of all the medical staff about radiation effects,the time lines of radiation damages and the treatment priorities.Further determinants of the outcome include rapid evacuation even from difficult locations,the availability of a specific triage tool to rapidly identify victims at risk for ARS,the availability of an antidote stockpile and dedicated hospital beds to treat seriously irradiated victims.
基金supported by the National Key Research and Development Program of the Ministry of Science and Technology of China(Grant Nos.2017YFA0302903,2016YFA0300602,2016YFA0300604,and 2016YFJC010282)the National Natural Science Foundation of China(Grant Nos.11227903,12004416,and U2032204)+3 种基金the Beijing Municipal Science and Technology Commission,China(Grant Nos.Z181100004218007 and Z191100007219011)the National Basic Research Program of China(Grant No.2015CB921304)the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant Nos.XDB07000000,XDB28000000 and XDB33000000)supported by the US Department of Energy(Basic Energy Sciences Grant No.DE-FG02-99ER45747).
文摘Theories and experiments on dirty superconductors are complex but important in terms of both theoretical fundamentals and practical applications.These activities are even more challenging when magnetic fields are present because the field distribution,electron density of states,and superconducting pairing potentials become nonuniform.Here,we present tunneling microspectroscopic experiments on NbC single crystals and demonstrate that NbC is a homogeneous dirty superconductor.When applying magnetic fields to the samples,we found that the zero-energy local density of states and the pairing energy gap followed the explicit scaling relation proposed by de Gennes for homogeneous dirty superconductors in high magnetic fields.More significantly,our experimental findings indicate that the validity of the scaling relation extends to magnetic field strengths far below the upper critical field,calling for a new nonperturbative understanding of this fundamental property in dirty superconductors.On the practical side,we used the observed scaling relation to derive a simple and straightforward experimental scheme for estimating the superconducting coherence length of a dirty superconductor in magnetic fields.
文摘A wide spectrum of scenarios may lead to radiation incidents and the liberation of radioactive material. In the case of a terrorist attack by a "dirty bomb", there is a risk of mechanical and thermal trauma, external irradiation, superficial contamination and incorporation of radioactive material. The first treatment priority must be given to the care of trauma patients with life-threatening injuries, as the health effects of radiation occur with latency. Radionuclide incorporation will lead to a longer-lasting irradiation from inside the body, associated with a higher risk of stochastic radiation effects(e.g., occurrence of tumors) in the long run. It must be expected that victims with potentially incorporated radionuclides will far outnumber trauma patients. The elimination of radionuclides can be enhanced by the administration of decorporation agents such as(Ca) Diethylenetriaminepentaacetic acid(DTPA) or Prussian blue,reducing the radiological burden of the body. There is still no consensus whether decorporation treatment should be started immediately based only on a suspicion of radionuclide incorporation("urgent approach") or if the results of internal dosimetry confirming the necessity of a treatment should be awaited, accepting the delay caused by the measurements and computations("precautionary approach"). As the therapeutic effectiveness may be substantially decreased if treatment initiation is delayed only by several days, depending on the radionuclide, the physicochemical properties of the compounds involved and the route of absorption, we favor an "urgent approach" from a medical point of view. In doubt, it seems justified to treat victims by precaution, as the adverse effects of the medication seem minimal. However, in the case of a high number of victims, an "urgent treatment approach" may require a large number of daily doses of antidotes, and therefore, adequate investments in preparedness and antidote stockpiling are necessary.
基金This work was partially supported by the National Key Technology Research and Development Program of the Ministry of Science and Technology of China under Grant No. 2015BAH10F01, the National Natural Science Foundation of China under Grant Nos. U1509216, 61472099, and 61133002, the Scientific Research Foundation for the Returned Overseas Chinese Scholars of Heilongjiang Province of China under Grant No. LC2016026, and the Ministry of Education (MOE)-Microsoft Key Laboratory of Natural Language Processing and Speech, Harbin Institute of Technology.
文摘Data quality is important in many data-driven applications, such as decision making, data analysis, and data mining. Recent studies focus on data cleaning techniques by deleting or repairing the dirty data, which may cause information loss and bring new inconsistencies. To avoid these problems, we propose EntityManager, a general system to manage dirty data without data cleaning. This system takes real-world entity as the basic storage unit and retrieves query results according to the quality requirement of users. The system is able to handle all kinds of inconsistencies recognized by entity resolution. We elaborate the EntityManager system, covering its architecture, data model, and query processing techniques. To process queries efficiently, our system adopts novel indices, similarity operator and query optimization techniques. Finally, we verify the efficiency and effectiveness of this system and present future research challenges.
基金supported by IMT-Advanced Novel Wireless Transmission Technology Program (2008ZX03003-004,2008BAH30B09)Chinese Important National Science and Technology Specific Project (2010ZX03002-003)+1 种基金the National Basic Research Program of China (2007CB310602)International Science and Technology Cooperation Program (2008DFA12160)
文摘This article considers the two-way multiple-input multiple-output(MIMO) relaying channels with multiple users,in which multiple users are served simultaneously by the base station(BS) with the assistance of the relay.The transmission consists of only two phases,doubling the system throughout over traditional one-way half-duplex transmission.A zero-forcing dirty paper coding(ZFDPC) aided physical-layer network coding(PNC) scheme is proposed in this article and the achievable capacity of the ZFDPC aided PNC scheme is derived.Simulation results show that the proposed scheme outperforms the previous decode-and-forward(DF) and zero-forcing beamforming(ZFBF) aided PNC scheme due to more degrees of freedoms and the advantage of PNC.Moreover,we analyze the effect of the imperfect channel state information(CSI) from RS to users at BS side to show the robustness of the proposed ZFDPC aided PNC scheme.
文摘Scientists use biology to purify polluted land In the old section of Suzhou, east China’s Jiangsu Province, a 40-hectare piece of land has been deserted for three years.
文摘Rapid economic growth has taken a toll on water quality Houses lining up meandering rivers make Jiaxing in east China’s Zhejiang Province a famed water city.Yet the Venetian-style center is suffering from a water shortage.Jiaxing has a population of more than
文摘贵刊去年第6期曾刊登一短文,题目是:盐,迫升血压之元凶。读了该文,我开始严格控制每日的食盐摄入量,再附以药物治疗,血压果然趋于平稳。近日上网,遇一奇文,意思是人的血压与空气污染状况有涉!根据对2600个成年人的调查,得出了这样的结论:Pollution may cause changes in the part of the nervous system that controls blood pressure.文章又同时说明:Exactly how pollution might cause blood pressure to climb remains unclear.人体之奥妙由此可见一斑。
基金Project supported by the National Key R&D Program of China (Grant Nos. 2022YFA1403203, 2022YFA1403400, and 2021YFA1400400)the Innovation Program for Quantum Science and Technology (Grant No. 2021ZD0302802)+2 种基金the National Natural Science Foundation of China (Grant Nos. 12074002, 12104004, 12204008, and 12374133)the Chinese Academy of Sciences (Grant Nos. XDB33000000 and GJTD-2020-01)the Major Basic Program of Natural Science Foundation of Shandong Province (Grant No. ZR2021ZD01)。
文摘In the phase diagram of the nickel-based superconductor Ba_(1-x)Sr_(x)Ni_(2)As_(2),T_(C) has been found to be enhanced sixfold near the quantum critical point(QCP) x=0.71 compared with the parent compound.However,the mechanism is still under debate.Here,we report a detailed investigation of the superconducting properties near the QCP(x≈0.7) by utilizing scanning tunneling microscopy and spectroscopy.The temperature-dependent superconducting gap and magnetic vortex state were obtained and analyzed in the framework of the Bardeen-Cooper-Schrieffer model.The ideal isotropic s-wave superconducting gap excludes the long-speculated nematic fluctuations while preferring strong electron-phonon coupling as the mechanism for T_(C) enhancement near the QCP.The lower than expected gap ratio of Δ/(k_(B) T_(C)) is rooted in the fact that Ba_(1-x)Sr_(x)Ni_(2)As_(2) falls into the dirty limit with a serious pair breaking effect similar to the parent compound.
文摘<b><span style="font-family:Verdana;">Background: </span></b><span style="font-family:""><span style="font-family:Verdana;">Terra Firma-Forme Dermatosis (TFFD), a benign skin condition which presents with asymptomatic brown to black plaques which resemble dirty skin. </span><b><span style="font-family:Verdana;">Aim:</span></b><span style="font-family:Verdana;"> To document a new case presentation with TFFD in the Arab region which is considered as one of the differential diagnos</span></span><span style="font-family:Verdana;">e</span><span style="font-family:""><span style="font-family:Verdana;">s of dirty neck. </span><b><span style="font-family:Verdana;">Case presentation: </span></b><span style="font-family:Verdana;">A 15-year-old girl presented with a history of asymptomatic brownish dirt-like lesion on the nape and sides of the neck for 4-years duration, not resolved by wash with water and soap and confused with other dermatos</span></span><span style="font-family:Verdana;">e</span><span style="font-family:Verdana;">s like acanthosis nigricans or atopic dermatitis. The diagnosis of TFFD was confirmed when the lesions </span><span style="font-family:Verdana;">were </span><span style="font-family:""><span style="font-family:Verdana;">completely resolved after gentle swabbing with 70% isopropyl alcohol. </span><b><span style="font-family:Verdana;">Conclusion:</span></b><span style="font-family:Verdana;"> TFFD is rarely reported in Arab region and should be considered when evaluating cases of dirty neck-like presentation of atopic dermatitis or acanthosis nigricans.
文摘In this paper, the capacity of a multiuser Multiple Input Multiple Output (MIMO) system employing the block diagonalization broadcasting scheme in presence of spatial correlation and mutual coupling is investigated. It is shown by computer simulations that, in general, the presence of spatial correlation decreases the capacity of a multiuser MIMO system. However, for some particular antenna element spacing mutual coupling decreases the spatial correlation rendering an increased capacity. The optimized diagonalization broadcasting technique with a two-stage power allocation scheme is proposed and verified. The presented simulations results confirm the advantage of the proposed broadcasting scheme.
文摘英语中有些动词,只要运用适当,可让表达更趋委婉,让对方更乐意接受。 1.建议对方别干某事时,可使用thank,allow,trouble(bother),suppose等。 I’ll thank you not to dirty my new bike. 求你别弄脏我的新自行车。句中的thank you not to…意思是“求你别……”,并不表示“感谢”,说话人或许有些不耐烦了,使用了thank可不致失礼。
文摘众所周知,西方人喜好养狗.因此英语中也就出现了许多与狗有关的习语.今年适逢又是中国人农历的狗年.在狗年谈狗更有一番情趣.Dog一词来自古英语里的docga、请看它的用法和习惯表述.1.指人(preceded by an adj)fellow or chap;a man or boy regarded asunpleasaht or wretchcd:e.g.a bird dog 搜罗人材的人:招揽生意的人.a clever dor 聪明伶俐的人dirty dog 坏小子;下流坯:卑污之人.a dumb dog
基金Project supported by the National Natural Science Foundation of China (No. 60572157)the Key Laboratory of Universal Wireless Communication of the Ministry of Education,China (No. 2007103)
文摘This paper deals with design and analysis of user scheduling and power allocation for multi-antenna OFDM systems with DPC,ZF-DPC,ZF-BF and TDMA transmit strategies.We consider the general multi-user downlink scheduling problem and power minimization with multi-user rate constraints.According to the channel state,it is shown that there is a power optimal policy which selects a subset of users in each scheduling interval.We present user selection algorithms for DPC,ZF-DPC,ZF-BF and TDMA for multi-antenna OFDM system in broadcast channels,and we also present the practical water-filling solution in this paper.By the selected users with the consideration of fairness,we derive the power optimization algorithm with multi-user rate constraints.We also analyze the power duality of uplink-downlink for the transmit strategies of DPC,ZF-DPC and ZF-BF.Simulation results show that the present user-scheduling algorithm and power minimization algorithm can achieve good power performance,and that the scheduling algorithm can guarantee fairness.