The nanometre limits of ballistic and diffusive hot-hole mediated nonlocal molecular manipulation.

We report an experimental investigation into the surface-specific and experimental limits of the range of STM induced nonlocal molecular manipulation. We measure the spot-size of the nonlocal manipulation of bromobenzene molecules on the Si(111)-7 × 7 surface at room temperature at two voltages and for a wide range of charge-injection times (number of hot charge-carriers) from 1 s up to 500 s. The results conform to an initially ballistic, 6-10 nm, and then hot-hole diffusive, 10-30 nm, transport away from the localised injection site. This work gives further confirmation that nonlocal molecular manipulation by STM directly reveals the ultrafast transport properties of hot-charge carriers at surfaces.

Regulating the femtosecond excited-state lifetime of a single molecule.

The key to controlling reactions of molecules induced with the current of a scanning tunneling microscope (STM) tip is the ultrashort intermediate excited ionic state. The initial condition of the excited state is set by the energy and position of the injected current; thereafter, its dynamics determines the reaction outcome. We show that a STM can directly and controllably influence the excited-state dynamics. For the STM-induced desorption of toluene molecules from the Si(111)-7x7 surface, as the tip approaches the molecule, the probability of manipulation drops by two orders of magnitude. A two-channel quenching of the excited state is proposed, consisting of an invariant surface channel and a tip height-dependent channel. We conclude that picometer tip proximity regulates the lifetime of the excited state from 10 femtoseconds to less than 0.1 femtoseconds.

Initiating and imaging the coherent surface dynamics of charge carriers in real space.

The tip of a scanning tunnelling microscope is an atomic-scale source of electrons and holes. As the injected charge spreads out, it can induce adsorbed molecules to react. By comparing large-scale 'before' and 'after' images of an adsorbate covered surface, the spatial extent of the nonlocal manipulation is revealed. Here, we measure the nonlocal manipulation of toluene molecules on the Si(111)-7 × 7 surface at room temperature. Both the range and probability of nonlocal manipulation have a voltage dependence. A region within 5-15 nm of the injection site shows a marked reduction in manipulation. We propose that this region marks the extent of the initial coherent (that is, ballistic) time-dependent evolution of the injected charge carrier. Using scanning tunnelling spectroscopy, we develop a model of this time-dependent expansion of the initially localized hole wavepacket within a particular surface state and deduce a quantum coherence (ballistic) lifetime of ∼10 fs.

Atomically resolved real-space imaging of hot electron dynamics.

The dynamics of hot electrons are central to understanding the properties of many electronic devices. But their ultra-short lifetime, typically 100 fs or less, and correspondingly short transport length-scale in the nanometre range constrain real-space investigations. Here we report variable temperature and voltage measurements of the nonlocal manipulation of adsorbed molecules on the Si(111)-7 × 7 surface in the scanning tunnelling microscope. The range of the nonlocal effect increases with temperature and, at constant temperature, is invariant over a wide range of electron energies. The measurements probe, in real space, the underlying hot electron dynamics on the 10 nm scale and are well described by a two-dimensional diffusive model with a single decay channel, consistent with 2-photon photo-emission (2PPE) measurements of the real time dynamics.

Mapping the site-specific potential energy landscape for chemisorbed and physisorbed aromatic molecules on the Si(1 1 1)-7 × 7 surface by time-lapse STM.

We present a scanning tunnelling microscope study of site-specific thermal displacement (desorption or diffusion) of benzene, toluene, and chlorobenzene molecules on the Si(1 1 1)-7 × 7 surface. Through time-lapse STM imaging and automated image analysis we probe both the chemisorbed and the physisorbed states of these molecules. For the chemisorption to physisorption transition there are distinct site-specific variations in the measured rates, however their kinetic origin is ambiguous. There is also significant variation in the competing rates out of the physisorbed state into chemisorption at the various surface sites, which we attribute to differences in site-specific Arrhenius pre-factors. A prediction of the outcome of the competing rates and pre-factors for benzene over three hours matches experiment.

Preparing and regulating a bi-stable molecular switch by atomic manipulation.

We present a scanning tunneling microscopy (STM) investigation into the influence of the STM tip on the adsorption site switching of polychlorinatedbiphenyl (PCB) molecules on the Si(111)-7 × 7 surface at room temperature. From an initially stable adsorption configuration, atomic manipulation by charge injection from the STM tip prepared a new bi-stable configuration that switched between two bonding arrangements. No switching rate bias dependence was found for +1.0 to +2.2 V. Assuming a thermally driven switching process we find that the measured energy barriers to switching are influenced by the exact location of the STM tip by more than 10%. We propose that this energy difference is due the dispersion interaction between the tip and the molecule.

Site- and energy-selective intramolecular manipulation of polychlorinated biphenyl (PCB) molecules.

We demonstrate the conversion of an adsorbed precursor state of polychlorinated biphenyl (PCB) molecules on the Si(111)-7 × 7 surface at room temperature into a more stable configuration via site- and energy-selective atomic manipulation in the scanning tunneling microscope (STM). Whereas molecular desorption is maximized by electron injection into the chemisorbed molecular ring at low voltage, injection into the physisorbed molecular ring above a threshold voltage (2.5 V) favors the reconfiguration of the bonding. The results clearly demonstrate both intramolecular charge localization and intramolecular charge transportation as key ingredients in the atomic manipulation of individual polyatomic molecules.

Nonlocal desorption of chlorobenzene molecules from the Si(111)-(7×7) surface by charge injection from the tip of a scanning tunneling microscope: remote control of atomic manipulation.

We report the nonlocal desorption of chlorobenzene molecules from the Si(111)-(7×7) surface by charge injection from the laterally distant tip of a scanning tunneling microscope and demonstrate remote control of the manipulation process by precise selection of the atomic site for injection. Nonlocal desorption decays exponentially as a function of radial distance (decay length ∼100 A) from the injection site. Electron injection at corner-hole and faulted middle adatoms sites couples preferentially to the desorption of distant adsorbate molecules. Molecules on the faulted half of the unit cell desorb with higher probability than those on the unfaulted half.

Time-resolved scanning tunnelling microscopy for molecular science.

Time-resolved scanning tunnelling microscopy (STM) and its application in molecular science are reviewed. STM can image individual atoms and molecules and thus is able to observe the results of molecular processes such as diffusion, desorption, configuration switching, bond-breaking and chemistry, on the atomic scale. This review will introduce time-resolved STM, its experimental limitations and implementations with particular emphasis on thermally activated and tunnelling current induced molecular processes. It will briefly examine the push towards ultrafast imaging. In general, results achieved by time-resolved STM demonstrate the necessity of both space and time resolution for fully characterizing molecular processes on the atomic scale.

Calibrating thermal and scanning tunnelling microscope induced desorption and diffusion for the chemisorbed chlorobenzene/Si(111)7 × 7 system.

The precise calibration of thermally driven processes in scanning tunnelling microscope (STM) manipulation experiments, especially at room temperature and above, is necessary to uncover an accurate picture of non-thermal dynamical processes such as desorption induced by electronic transitions, driven by the STM current. Here we probe the displacement (the sum of desorption and diffusion) of chlorobenzene molecules chemisorbed on the Si(111)-7 × 7 surface, induced both by the STM electrical current and by heat. We also establish truly passive imaging inspection parameters. The activation energy for pure thermal displacement is 580 ± 20 meV, possibly associated with excitation to a physisorbed precursor state. STM induced displacement shows a marked decrease with increasing temperature, once the thermal effects are removed.

Two-electron dissociation of single molecules by atomic manipulation at room temperature.

Using the tip of a scanning tunnelling microscope (STM) to mechanically manipulate individual atoms and molecules on a surface is now a well established procedure. Similarly, selective vibrational excitation of adsorbed molecules with an STM tip to induce motion or dissociation has been widely demonstrated. Such experiments are usually performed on weakly bound atoms that need to be stabilized by operating at cryogenic temperatures. Analogous experiments at room temperature are more difficult, because they require relatively strongly bound species that are not perturbed by random thermal fluctuations. But manipulation can still be achieved through electronic excitation of the atom or molecule by the electron current tunnelling between STM tip and surface at relatively high bias voltages, typically 1-5 V. Here we use this approach to selectively dissociate chlorine atoms from individual oriented chlorobenzene molecules adsorbed on a Si(111)-7 x 7 surface. We map out the final destination of the chlorine daughter atoms, finding that their radial and angular distributions depend on the tunnelling current and hence excitation rate. In our system, one tunnelling electron has nominally sufficient energy to induce dissociation, yet the process requires two electrons. We explain these observations by a two-electron mechanism that couples vibrational excitation and dissociative electron attachment steps.

Decoration of surfaces with size-selected clusters and molecular manipulation at room temperature: precision and uncertainty in organizing atoms.

The deposition onto surfaces of clusters of atoms, prepared and size-selected in the gas phase, is, like atomic or molecular manipulation with the scanning tunnelling microscope, an appealing (but parallel) route to the creation of nanoscale surface features. Both of these seemingly orthogonal approaches allow, in principle, a selected number of atoms to be organized, and both are strongly affected by the lateral thermal diffusion of the constituent atoms, molecules or clusters over the surface. In this sense, the room-temperature (as opposed to cryogenic-temperature) regime can be regarded as a hostile environment for organizing atoms. In this paper we review recent achievements in size-selected cluster deposition and molecular manipulation at room temperature and thus address the fundamental question: with what precision can we organize atoms at room temperature?

Mechanisms of molecular manipulation with the scanning tunneling microscope at room temperature: chlorobenzene/si(111)-(7 x 7).

We report a systematic experimental investigation of the mechanism of desorption of chlorobenzene molecules from the Si(111)-(7 x 7) surface induced by the STM at room temperature. We measure the desorption probability as a function of both tunneling current and a wide range of sample bias voltages between -3 V and +4 V. The results exclude field desorption, thermally induced desorption, and mechanical tip-surface effects. They indicate that desorption is driven by the population of negative (or positive) ion resonances of the chemisorbed molecule by the tunneling electrons (or holes). Density functional calculations suggest that these resonant states are associated with the pi orbitals of the benzene ring.

Cancer pain management skills among medical students: the development of a Cancer Pain Objective Structured Clinical Examination.

Recent surveys suggest that most physicians have inadequate knowledge to assess and manage cancer pain; however, the important domain of clinical performance has not yet been clearly evaluated. The Objective Structured Clinical Examination (OSCE) has become a widely- used and accepted method to evaluate the clinical abilities of medical students. The purpose of this study was to develop and test a Cancer Pain OSCE for medical students evaluating their clinical competence in the area of cancer pain management. A four-component Cancer Pain OSCE was developed and presented to 34 third-year medical students during a sixteen-week combined medicine/surgery clerkship. The content of the objective criteria for each component of the OSCE was developed by a multidisciplinary group of pain experts. The OSCE was designed to assess the students' cancer pain management skills of pain history-taking, focused physical examination, analgesic management of cancer pain, and communication of opioid analgesia myths. Actual cancer survivors were used in the five-minute individual stations. The students were asked to complete a cancer pain history, physical examination, manage cancer pain using analgesics, and communicate with a family member regarding opioid myths. Clinical performance was evaluated using pre-defined checklists. Results showed the student's average performance for the history component was the highest of all four components of the examination. Out of 34 points possible on this clinical skills item, students on average (SD) scored 24.5 (5.2), or 72%. For the short-answer analgesic management component of the Cancer Pain OSCE, the overall score was 32%. Most students managed cancer pain with opioids, however, very few prescribed regular opioid use, and the use of adjuvant analgesics was uncommon. Student performance on the focused cancer pain physical examination was, in general, poor. On average students scored 61% on the musculoskeletal system, but only 31% on both the neurological and lymphathic examination. The overall percent score for the cancer pain OSCE was 48%. We conclude that the Cancer Pain OSCE is a useful performance-based tool to test individual skills in the essential components of cancer pain assessment and management. Of the four components of the Cancer Pain OSCE, medical students performed best on the cancer pain history and performed poorly on the cancer pain physical examination. Information gained from this study will provide a foundation on which future small-group medical student structured teaching will be based.

Cancer pain education: a structured clinical instruction module for hospice nurses.

The learning experience with the Cancer Pain Structured Clinical Instruction Module (SCIM), a highly structured skills training course for medical students, has been reported favorably. The purpose of this study was to present the Cancer Pain SCIM to registered nurses employed in a hospice setting. The goal of the study was to pilot test a structured cancer pain educational program for hospice nurses and to determine the perceived effectiveness of this course on the participants' cancer pain assessment and management skills. A multidisciplinary Cancer Pain SCIM was presented to 25 hospice nurses to improve their understanding of the management of cancer pain. The development group identified essential aspects of cancer pain management and then developed checklists defining specific station content. During the 2-hour Cancer Pain SCIM, nurses rotated through 8 stations in groups of 3, spending 15 minutes at each station. Eight instructors and 6 standardized patients, 5 of whom were survivors of cancer, participated in the course. All participants (students, instructors, and patients) evaluated the course, using a 5-point Likert scale (1 = strongly disagree; 5 = strongly agree). Nurses provided self-assessments of their perceived competence on important aspects of cancer pain management both before and after the SCIM. The self-assessment items used a 5-point scale ranging from 1 (not competent) to 5 (very competent). Twenty-five hospice nurses, averaging 4.1 years (range 1-30 years) postgraduation, participated in the Cancer Pain SCIM. Overall, nurses agreed that they improved on each of the 8 teaching items (P < 0.001). The average (SD) pretest score of 2.8 (0.72) improved to 3.8 (0.58) on the post-test (P < 0.001). Nurses believed that their mastery of specific clinical skills, taught in all 8 stations, improved as a result of participation in the course. Nurses strongly agreed (mean +/- SD) that it was beneficial to use patients with cancer in the course (4.6 +/- 0.82). Faculty members enjoyed participating in the course (4.9 +/- 0.35) and indicated a willingness to participate in future courses (4.7 +/- 0.49). Significant perceived learning among hospice nurses took place in all aspects of the Cancer Pain SCIM. Participating nurses, instructors, and patients with cancer appreciated the SCIM format. Nurses and faculty considered the participation of actual patients with cancer highly beneficial. The SCIM format has great potential to improve the quality of cancer pain education.

Implementing cancer pain education for medical students.

PURPOSE: The purpose of this study was to develop and pilot a cancer pain education course for medical students, using a structured home hospice visit. DESCRIPTION OF STUDY: A 1-hour home hospice visit was presented to 57 senior medical students. The content and objective criteria for the structured home hospice visit were developed by a multidisciplinary group of experts. During a 1-hour interview, students completed a cancer pain history, performed a focused physical examination, and received feedback and teaching regarding the essentials of cancer pain management from the hospice nurse. All students and hospice patients completed a multi-item evaluation questionnaire with a 5-point Likert scale (1=strongly disagree; 5=strongly agree) regarding the structured home hospice visit. RESULTS: Most students agreed strongly that the home hospice visit was a positive experience (mean +/- SD 4.8 +/- 0.44) that helped them to understand the management of cancer pain (mean 4.7 +/- 0.46) and opioid-related side effects (mean 4.5 +/- 0.57). Most patients enjoyed visiting with the students (mean 4.90 +/- 0.30), agreed that the visit was not tiring (mean 4.81 +/- 0.51), and felt that they benefited from participating (mean 4.76 +/- 0.54). CLINICAL IMPLICATIONS: The authors concluded the following: 1) that medical students benefited from learning about cancer pain assessment and management through the use of a structured home hospice visit; 2) that a structured home hospice visit helped the students to learn the basics of cancer pain management; 3) that patients enjoyed their role as teacher for medical students; and 4) that senior hospice nurses provided excellent instruction for medical students in the management of cancer pain.

Junior medical students' perceptions of an introductory hospice experience.

INTRODUCTION: The importance of palliative care education in the medical school curriculum is becoming more recognized. The purpose of this study was to assess medical students' perceptions of an introductory hospice experience. METHODS: Forty-one second-year medical students took part in an introductory hospice experience in which they were acquainted with a wide range of hospice services provided to patients and families by an interdisciplinary team involved in hospice care. In addition, the students visited patients' homes individually with an experienced hospice nurse or social worker. At the end of their experience, the students were asked to complete a multi-item evaluation questionnaire in order to share their perceptions of the hospice experience and their suggestions for improvement of the course. RESULTS: The students spent an average of four hours on their introductory hospice experience, and they indicated that all of their personal goals for their experience had been met. Suggestions for improvement of the course were to increase the amount of course time allotted and to provide further opportunity to see more patients. Overall, the students rated their experience as "above average" to "excellent." CONCLUSIONS: According to the medical students who participated, the introductory hospice experience was a worthwhile and valuable educational experience. An equal or increased amount of hospice time should be allotted in the education of future junior medical students.

Cancer pain education: the use of a structured clinical instruction module to enhance learning among medical students.

The Structured Clinical Instruction Module (SCIM) is an educational format developed for the teaching of clinical and interpersonal skills. The purpose of this study was to develop and pilot-test a SCIM to enhance medical students' learning and understanding about cancer pain assessment and management. The Cancer Pain SCIM was presented to 34 third-year medical students. Eight instructors and six standardized patients (five cancer patients) participated in the course. All participants evaluated the course using a five-point Likert scale (1 = strongly disagree; 5 = strongly agree). Students self-assessed their clinical skills before and after the course using a five-point scale (1 = not competent; 5 = very competent). Students agreed [mean (S.D.)] very strongly that the SCIM was a valuable educational experience [4.4 (0.56)] and that it was beneficial to use actual cancer patients in the SCIM [4.5 (0.63)]. Students believed their skills in the assessment and management of cancer pain significantly improved after the course. The SCIM is a valuable and novel instructional format to teach essential skills in the assessment and management of cancer pain to medical students.

Physician board certification in hospice and palliative medicine.

The American Board of Hospice and Palliative Medicine (ABHPM) was formed in 1995 to establish and implement standards for certification of physicians practicing hospice and palliative medicine and, ultimately, accreditation of physician training in this discipline. The ABHPM has created a certification process that parallels other member boards of the American Board of Medical Specialties (ABMS). After 3(1/2) years and the administration of seven examinations, 623 physicians have achieved board certification in hospice and palliative medicine. Those with ABMS primary board certifications have been certified by anesthesiology, 4%; family practice, 23%; internal medicine, 55%; pediatrics, 1%; radiation oncology, 2%; and surgery, 2%. The majority describe their practice location as urban. Sixty-nine percent report more than 5 years of clinical experience in hospice/palliative medicine and 75% report an association with a hospice as medical director or hospice physician. Sixty-seven percent belong to the American Academy of Hospice and Palliative Medicine. Applicants were drawn from 48 states, Canada, and 3 foreign countries. The available data indicate only 20% were less than 40 years of age and that two-thirds were men. There is significant physician interest in seeking professional recognition of expertise in caring for terminally ill persons and their families through creation of a specialty in hospice and palliative medicine. Certification of physicians and accreditation of training programs are key elements in this process. This process will encourage more physicians to enter this field and provide needed expertise in the management of patients with progressive disease for whom the prognosis is limited, and the focus of care is quality of life.

Cancer pain assessment and management recommendations by hospice nurses. University of Kentucky, Lexington, Kentucky.

Pain is often the most prevalent symptom among cancer patients referred to hospice or palliative care programs. This study was designed to use performance-based testing to evaluate the skills of hospice nurses in assessing the severe pain of a cancer patient and the pain management recommendations they would present to the patient's primary care physician. Twenty-seven hospice nurses (ranging in experience from 1 month to 10 years) were presented with the same standardized patient with cancer pain. In Part A (7 minutes), one of the investigators checked for predetermined behaviors as the nurses performed the clinical pain assessment. In Part B (7 minutes), the nurses answered questions regarding their recommendations for pain management for the patient seen in Part A. In the admission pain assessment, hospice nurses did well in assessing pain intensity (85%), pain location (70%), and pain-relieving factors (59%). However, only 48% of the nurses adequately assessed the pain onset, and only 44% adequately assessed other symptoms the patient might be experiencing. In Part B, 96% of the nurses recommended opioids, 96% recommended the oral route of administration, and 82% recommended regular dosing of the opioids. Fifty-six percent of nurses included a breakthrough medication in their analgesic recommendations. All of the hospice nurses treated the patient's fear of addiction in an appropriate manner, and 93% of the nurses recommended increasing the patient's opioid dosage to treat the persisting pain problem. There were no significant differences among nurses with regard to length of time as a hospice nurse or hospice certification on any of the items in either Part A or Part B. Most practicing hospice nurses were judged to be competent in the assessment and management of the severe pain of the standardized cancer patient, although some deficits were noted. Regular oral opioids were the analgesics of choice. Co-analgesics were rarely recommended.