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C Langer

Publications and source records attributed to C Langer.

At least 19 recordsLinked to original sources
PubMed2003

Quantum information processing with trapped ions.

Experiments directed towards the development of a quantum computer based on trapped atomic ions are described briefly. We discuss the implementation of single-qubit operations and gates between qubits. A geometric phase gate between two ion qubits is described. Limitations of the trapped-ion method such as those caused by Stark shifts and spontaneous emission are addressed. Finally, we describe a strategy to realize a large-scale device.

Journal Article↗
PubMed2003

Paralysis of the femoral nerve following totally extraperitoneal laparascopic inguinal hernia repair.

Totally extraperitoneal preparation (TEP) of an inguinal hernia is an established method of treating inguinal hernias associated with an acceptable complication rate (2-12%) and low rate of recurrence (0-3%). This is the first reported case of sensorimotor paralysis of the femoral nerve following the complete endoscopic mesh treatment of a primary inguinal hernia to the left side. Following a discussion of the necessary diagnostic and therapeutic steps, traumatic postsurgical paralysis of the nerve as well as spontaneous paralysis of the femoral nerve are discussed. The prognosis is positive given the lack of macroscopic evidence of any direct damage to the nerve.

Femoral Neuropathy↗
PubMed2003

Experimental demonstration of a robust, high-fidelity geometric two ion-qubit phase gate.

Universal logic gates for two quantum bits (qubits) form an essential ingredient of quantum computation. Dynamical gates have been proposed in the context of trapped ions; however, geometric phase gates (which change only the phase of the physical qubits) offer potential practical advantages because they have higher intrinsic resistance to certain small errors and might enable faster gate implementation. Here we demonstrate a universal geometric pi-phase gate between two beryllium ion-qubits, based on coherent displacements induced by an optical dipole force. The displacements depend on the internal atomic states; the motional state of the ions is unimportant provided that they remain in the regime in which the force can be considered constant over the extent of each ion's wave packet. By combining the gate with single-qubit rotations, we have prepared ions in an entangled Bell state with 97% fidelity-about six times better than in a previous experiment demonstrating a universal gate between two ion-qubits. The particular properties of the gate make it attractive for a multiplexed trap architecture that would enable scaling to large numbers of ion-qubits.

Journal Article↗
PubMed2003

Experimental demonstration of a technique to generate arbitrary quantum superposition states of a harmonically bound spin-1/2 particle.

Using a single, harmonically trapped 9Be(+) ion, we experimentally demonstrate a technique for generation of arbitrary states of a two-level particle confined by a harmonic potential. Rather than engineering a single Hamiltonian that evolves the system to a desired final state, we implement a technique that applies a sequence of simple operations to synthesize the state.

Journal Article↗
PubMed2003

Prognostic factors influencing surgical management and outcome of gastrointestinal stromal tumours.

BACKGROUND: The purpose of this study was to review surgical experience with gastrointestinal stromal tumours (GISTs) at a single tertiary university hospital, and to identify morphological and genetic prognostic markers of tumour progression. METHODS: Forty-eight GISTs from 39 patients were reviewed retrospectively. The prognostic significance of DNA copy number changes, measured by comparative genomic hybridization (CGH), and morphological markers in low-risk and high-risk tumours were investigated. RESULTS: Significantly more patients died from disease after incomplete tumour resection than after complete primary resection (P = 0.020). Tumour size of 5 cm or greater, mitotic count of 2 or more, and proliferative activity greater than 10 per cent were significantly associated with a shorter recurrence-free survival (P = 0.020, P = 0.001 and P = 0.002 respectively). Patients with low-risk tumours had a significantly better outcome than those with high-risk GISTs, both in terms of overall and recurrence-free survival (P < or = 0.001). CGH performed on 16 tumours revealed fewer DNA sequence copy number changes in low-risk than in high-risk GISTs. Non-progressive GISTs contained significantly fewer genetic alterations than recurrent or metastatic tumours (P < 0.001). Only tumours with more than five changes showed disease progression. CONCLUSION: Complete surgical resection is the most important means of cure for GISTs. DNA copy number changes are related to the behaviour of these tumours and may serve as additional prognostic markers.

Adult↗
PubMed2003

[Twenty-five years of experience in incisional hernia surgery. A comparative retrospective study of 432 incisional hernia repairs].

INTRODUCTION: Incisional hernia surgery in Germany is changing from conventional techniques to mesh implantation. The relevance of different factors such as surgical technique, mesh material, and patient-related parameters concerning the outcome following mesh repair is still under debate. METHODS: In a comparative retrospective study of 432 incisional hernia operations on 348 patients we analyzed 11 autodermic hernioplasties, 241 Mayo procedures,and 180 mesh repairs over a 25-year time period. In addition to the quality of life following mesh implantation,the prognostic relevance of demographic, pre- and intraoperative parameters, surgical technique, mesh material, and the surgeon's experience were subjected to both univariate and multivariate analysis. RESULTS: With a mean follow-up of 9.7+/-8.8 years, the rate of major complications following mesh repair was 9% in contrast to 3% after the Mayo procedure (p=0.091). The sublay technique revealed less complications compared to the onlay procedure (p=0.016). The total recurrence rate following the overlapping Mayo repair was 37% in contrast to 15% after mesh implantation (p=0.001), with a significant superiority of the sublay technique over the inlay technique (p=0.043). The rate of recurrences and complications after autodermic hernioplasty was 72% and 36%,respectively. After mesh repair, 86% of the patients were better satisfied with the results after Marlex mesh compared to GoreTex (p=0.016). Mesh size was the only significant prognostic factor concerning quality of life following mesh implantation. The complication rate was determined significantly by the patients' risk factors, size of hernia, surgical technique, and the surgeon's experience, whereas the rate of recurrences was significantly influenced by the parameters obesity (BMI >25), size of hernia,and surgical experience. The recurrence rate decreased significantly with the surgeon's experience: a minimum of 16 mesh repairs led to a recurrence rate of less than 10%. CONCLUSIONS: Only the mesh repair revealed acceptable recurrence rates with high patient comfort. The sublay technique is superior to onlay concerning the complication rate, whereas the autodermic hernioplasty and inlay techniques are obsolete. The material of choice is polypropylene. The most important prognostic factor following mesh repair is the surgeon's experience.

Adult↗
PubMed2003

[Cocaine-body-packing. Infrequent indication for laparotomy].

INTRODUCTION: Body-packers or "mules" are drug smugglers who swallow cocaine-filled condoms in order to conceal them during air travel. Body pushers hide drug packages in the rectum or vagina. In a cooperative effort between the Frankfurt Airport Clinic and the GIZ-Nord (Goettingen University poison control center), we performed a retrospective study and developed an algorithm for the problem of "rupture of a cocaine-filled condom in a body-packer." METHODS: In a retrospective analysis, the data of all cocaine body-packers and body pushers who were identified at Frankfurt International Airport from 1985 to 2001 were evaluated.Temporal development, demographic data, and surgical aspects were of special interest. RESULTS: From 1985 to 2001 a total of 280 body pushers and 2880 body-packers were identified: 63 "mules" (2.2%) developed symptoms of severe cocaine intoxication following rupture of a condom. Emergency laparotomy was performed on 20 patients (i.e., 32% of all symptomatic body-packers) and the condoms were removed, while 43 body-packers (68%) died before surgical therapy could be initiated. All operated patients survived. CONCLUSION: Severe cocaine intoxication is life threatening. Patients die from complications caused by generalized vasoconstriction. If the reason for severe cocaine intoxication is the rupture of a cocaine-filled condom,the only possible therapy consists of immediate laparotomy for removal of the condoms.

Adolescent↗
PubMed2003

[Preoperative diagnostic procedures in locally advanced rectal carcinoma (> or =T3 or N+). What does endoluminal ultrasound achieve at staging and restaging (after neoadjuvant radiochemotherapy) in contrast to computed tomography?].

INTRODUCTION: Neoadjuvant radiochemotherapy (neoRT/CT) in locally advanced rectal cancer requires an exact initial determination of the depth of the cancerous infiltration (T-status) and of locoregional lymph node metastasis (N-status). For staging and restaging, contrast-enhanced computed tomography (CT) is usually used. In specialised centers, the endorectal ultrasound (rES) may be preferred. METHODS: Between January 1998 and May 2001, the T- and N-status of 102 patients with adenocarcinoma of the rectum (> or =T3 or N+) was determined prospectively by rES and CT (group I: n=61 without neo-RT/CT, examined once; group II: n=41 examined before and after neoRT/CT). All diagnostic findings were compared using the (y)pTNM-classification. RESULTS: In the patients from group I, the depth of infiltration (uT) was predicted correctly by rES in 75% and by CT in 48% of cases; the carcinomas were understaged in 10% and 41% of cases and overstaged in 15% and 11%, respectively. According to the histopathological findings, the N-status was determined correctly by rES and CT in 75% and 57% of cases, understaging occurred in 8% and 30% and overstaging in 17% and 13%, respectively. In cases in which both methods resulted in identical T- (uT+ctT) or N-staging (uN+ctN), the accuracy increased to 82% and 80%, respectively. In patients from group II, after neoRT/CT rES and CT allowed the exact prediction of the yuT-stage in 66% and 51%, respectively. Only 2% were understaged by rES (understaging by CT: 22%). Overstaging occurred in 32% and 27% by rES and CT, respectively. The N-status determined by rES and CT was in accordance with the histopathological findings in 68% and 76%of cases, respectively. Understaging occurred in 20% and 17%,overstaging in 12% and 7%, respectively. Again identical staging results in both rES and CT increased the accuracy of the T- (yuT+yctT) or N- (yuN+yctN) classification to 90% and 83%, respectively. In group II, downsizing of the tumor by more than one T-stage was correctly assessed by rES results in 15/20 cases (75%). A complete remission of initial uT3-carcinoma was diagnosed correctly in only two of eight ypT0-cases. In contrast, CT demonstrated a remission of disease in all cases but was unable to predict the extent of tumour reduction. A remission of lymph node metastasis was accurately shown by rES in 17/19 cases (90%) and by CT in 10/12 cases (83%). CONCLUSION: The staging of pretherapeutic, locoregional T- and N-status by rES is superior to that by CT (T-status: P=0.0164, N-status: P=0.0035). At restaging, rES offers higher accuracy in the detection of residual tumour infiltration (but not significantly to CT, yT-status: P=0.0833, yN-status: P=0.7962) and assessment of local remission. Therefore rES should be the method of choice in staging to avoid overtreatment in neoadjuvant settings.After neoRT/CT, the predictive efficacy of the rES for the downsizing/-staging of rectal cancer must be evaluated on greater numbers of patients receiving standardised diagnostic procedures and therapy.

Adenocarcinoma↗
PubMed2003

[A bipolar radial head prosthesis after comminuted radial head fractures: indications, treatment and outcome after 5 years].

The treatment of comminuted fractures of the radial head with concomitant injuries of the ulnar complex by resection of the radial head usually does not provide satisfactory long-term results. Other than joint instability in the elbow and a limited range of motion, radius proximalisation in the sense of ulnocarpal impingement, osteoarthritis and pain in the elbow have been described. Between 1995 and 1997, 11 radial head prostheses were implanted in ten patients who had sustained a comminuted fracture of the radial head with concomitant injury to the ulnar complex. A follow-up survey was conducted with the patients on average 5 years after the injury. Eight patients with nine implants participated in the follow-up, one patient had died and another refused to participate but declared that he did not suffer from any impairment. According to the Morrey score, two of the results were found to be very good, five to be good, one to be fair and one to be poor. Despite the severe injuries sustained by the elbow, neither joint instability in the elbow nor proximalisation of the radius, cubitus valgus, ulnar nerve syndrome, nor loosening of the prosthesis were found in any of the patients. In the event of comminuted fractures of the radial head which are impossible to reconstruct by osteosynthesis and which occur with concomitant ulnar ligamentous or osseous injury, the implantation of a prosthesis is preferred over the resection of the head of the radius.

Adult↗
PubMed2002

Surgical cure for early rectal carcinoma and large adenoma: transanal endoscopic microsurgery (using ultrasound or electrosurgery) compared to conventional local and radical resection.

BACKGROUND AND AIMS: The minimally invasive technique of transanal endoscopic microsurgery (TEM) combines the benefits of local resections, a low complication rate and high patient comfort, with low recurrence rate and excellent survival rate after radical surgery (RS). The use of an ultrasonically activated scalpel rather than electrosurgery further improves the results of TEM. PATIENTS AND METHODS: A retrospective study was performed of 182 operations on 162 patients with early rectal carcinoma (pT1, G1/2) or adenoma to compare the outcome following four different kinds of surgical resection techniques: RS (anterior or abdominoperineal resection; n=27), conventional transanal resection using Park's retractor (TP; n=76), transanal endoscopic microsurgery (TEM) with electrosurgery (TEM-ES; n=45), and TEM with UltraCision (TEM-UC; n=34). One-third of the patients with RS (33%) received either a colostomy or a protective loop-ileostomy. RESULTS: Operation time with TEM-UC was significantly shorter than with TEM-ES or RS. Hospitalization was significantly longer with RS than for TEM or TP. Complication rate with TEM was significantly lower than with RS. Recurrence rate with RS and TEM was significantly lower than with TP, with a trend to TEM-UC being better than TEM-ES. Mortality rate was 3.7% with RS and 0 with TP and TEM. The 2-year survival rate was 96.3% with RS and 100% each with TP and TEM. CONCLUSION: TEM using UC seems to be the technique of choice. TP leads to an unacceptable recurrence rate, and RS results in a higher incidence of complication and impairment of life quality.

Adenoma↗
PubMed2002

Experimental demonstration of a controlled-NOT wave-packet gate.

We report the experimental demonstration of a controlled-NOT (CNOT) quantum logic gate between motional and internal-state qubits of a single ion where, as opposed to previously demonstrated gates, the conditional dynamics depends on the extent of the ion's wave packet. Advantages of this CNOT gate over one demonstrated previously are its immunity from Stark shifts due to off-resonant couplings and the fact that an auxiliary internal level is not required. We characterize the gate logic through measurements of the postgate ion state populations for both logic basis and superposition input states, and we demonstrate the gate coherence via an interferometric measurement.

Journal Article↗
PubMed2002

Trapped-ion quantum simulator: experimental application to nonlinear interferometers.

We show how an experimentally realized set of operations on a single trapped ion is sufficient to simulate a wide class of Hamiltonians of a spin-1/2 particle in an external potential. This system is also able to simulate other physical dynamics. As a demonstration, we simulate the action of two nth order nonlinear optical beam splitters comprising an interferometer sensitive to phase shift in one of the interferometer beam paths. The sensitivity in determining these phase shifts increases linearly with n, and the simulation demonstrates that the use of nonlinear beam splitters (n=2,3) enhances this sensitivity compared to the standard quantum limit imposed by a linear beam splitter (n=1).

Journal Article↗
PubMed2002

Mesh penetration of the sigmoid colon following a transabdominal preperitoneal hernia repair.

The laparascopic transabdominal preperitoneal (TAPP) repair of an inguinal hernia is an established technique associated with notably low rates of recurrence and complication. Inguinal pain and anal bleeding following a TAPP procedure may result from the penetration of the repair mesh into the sigmoid colon. In this case report, we discuss this particular complication following the TAPP procedure. Subsequently, we describe the diagnostics as well as the surgical treatment necessary.

Colon, Sigmoid↗
PubMed2002

[Simulation of surgical techniques in graduate education of the surgeon. An analysis of value and effect].

The course in Gastrointestinal Surgery (GISC) aims at teaching and training resection, reconstruction and suture techniques of the upper gastrointestinal tract. Prior to, after and 5 years following the first course, participants were asked to answer a questionnaire requesting information regarding the adequacy of surgical training in their residency program and how much they had benefited from the GISC. While 1/3 of the participants described the surgical training during their residency as inadequate, more than 90% benefited from the GISC. Although the single-layer-continuous suture technique was implemented by only 8% of the participating surgeons, other techniques such as cross-section gastroenterostomy were accepted by 38%. Only 7% of the participants rejected these new techniques, while 41% of the senior surgeons at home could not be convinced. Besides the teaching of new techniques, participants benefited above all from the repetitive training in surgical procedures.

Animals↗
PubMed2002

[The carcinogenic potential of biomaterials in hernia surgery].

The implantation of meshes to correct inguinal as well as incisional hernias is widely used in the U.S.A. and Western Europe. The short and long term results of meshes are convincing concerning complications, recurrence rate and patient's comfort. On the other hand side some scientific groups discuss the possibility of malignant tumor development due to implanted meshes. In fact, experimental models exist which demonstrate that soft tissue sarcomas can be induced in mice and rats by implanting artificial materials such as synthetics or metal. Beside millions of hernia repairs using meshes worldwide no patient has been reported with a soft tissue tumor until today. The analyses of molecular markers of proliferation, of apoptosis as well as the modulation of heat shock proteins seem not to prove the carcinogenic potential of meshes. In conclusion, there are no data so far indicating a real risk for humans to develop malignant tumors due to implanted meshes. Therefore we further propagate the implantation of meshes in hernia repair in adult patients.

Adult↗